JP3581748B2 - Image reading device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image reading device, and more particularly, to an image reading device capable of appropriately determining shading correction accuracy and image quality.
[0002]
[Prior art]
In the image reading apparatus, there are fluctuations in the light emission amount of the light source over time, fluctuations due to temperature rise, and fluctuations in read density due to fluctuations in the sensitivity of each pixel of the photoelectric conversion unit. Conventionally, a white reference plate is scanned before reading an image of a document to obtain white reference data, and shading correction of the image of the document is performed based on the white reference data. ing.
[0003]
As a device for performing such shading correction, for example, a circuit that A / D converts an image signal obtained by scanning a photodetector array a plurality of times and accumulates and stores the image signal for each pixel, And a circuit for calculating and storing the shading correction coefficient from the value, thereby providing an image input device (see Japanese Patent Application Laid-Open No. 61-71764) for obtaining the shading correction coefficient with low noise and high speed, and a plurality of white reference plates. An image reading apparatus (see Japanese Patent Application Laid-Open No. 63-1249) that determines the life of a light source or a white reference plate by comparing the maximum value of an image signal obtained by scanning with a preset threshold has been proposed. Also, when reading the luminance information on the reference plate, the carriage carrying the image sensor and the light source is moved at the same time when the image sensor is irradiated with light. And by suppressing the shading correction apparatus the influence of changes in the partial reflectance on the reference plate (see JP-A-1-132275) have been proposed.
[0004]
As described above, in the conventional image reading apparatus, how the shading coefficient is set to be low noise, the life of the light source or the white reference plate is determined from the white reference data obtained by reading the white reference plate, or the white reference It is an object of the present invention to appropriately perform shading correction depending on how to reduce the influence of partial reflectance when reading a plate.
[0005]
In the conventional shading correction, generally, as shown in the case of the facsimile apparatus 1 in FIG. Then, shading correction is performed based on the white reference data.
[0006]
That is, in the facsimile apparatus 1, before reading the original 2, the light source 3 irradiates the white reference plate 4 from the light source 3, and the reflected light is introduced into the image sensor 7 via the mirror 5 and the lens 6. The signal is photoelectrically converted and transferred to the A / D converter 9 via the amplifier 8. The maximum value of the image signal for one line input to the A / D converter 9 is detected and held by a peak hold circuit 10, and the A / D converter 9 detects the peak value detected and held by the peak hold circuit 10. The image signal amplified and input by the amplifier 8 based on the value is quantized and stored as white reference data in the line buffer 13 via the shading correction circuit 11.
[0007]
When reading the original 2, the original 2 conveyed on the guide 14 is irradiated with light from the light source 3, and the reflected light is introduced into the image sensor 7 via the mirror 5 and the lens 6 in the same manner as described above. Then, the image signal photoelectrically converted by the image sensor 7 is transferred to the A / D converter 9 via the amplifier 8. At this time, the maximum value of the image signal for one line is detected by the peak hold circuit 10, quantized by the A / D converter 9 based on the maximum value (peak value), and output to the shading correction circuit 12.
[0008]
The system control unit 14 sequentially reads out the white reference data stored in the line buffer 13 when reading the white reference plate 4 corresponding to the image signal input from the A / D converter 9 for each pixel. The image signal is transferred to the shading correction circuit 12, and the shading correction circuit 12 performs a predetermined shading correction operation on the image signal input from the A / D converter 9 based on the white reference data, and outputs the image signal to the digital image processing circuit 16.
[0009]
The digital image processing circuit 16 performs various image processing on the image signal on which the distortion correction has been performed.
[0010]
Then, the image reading apparatus such as the conventional facsimile apparatus 1 performs the reading of the white reference plate 4 once before reading the document 2 to obtain the white reference data. Is subjected to shading correction based on the white reference data.
[0011]
[Problems to be solved by the invention]
However, in such a conventional image reading apparatus, only the shading correction is performed based on the white reference data obtained by scanning the white reference plate once before reading the document, and the accuracy of the shading correction is evaluated. Has not been performed, the reading sensitivity has decreased due to the deterioration of the photoelectric conversion units such as the light source and the image sensor due to the passage of time due to paper dust or dust adhering to the optical system. It is not known that the accuracy has deteriorated, and in such a case, the same image processing is performed and there is a problem that the image quality is reduced.
[0012]
Further, in the above-described conventional publications, how low the shading coefficient is set to noise, and the life of the light source and the white reference plate are determined from white reference data obtained by reading the white reference plate. Or to reduce the influence of the partial reflectance when reading the white reference plate to reduce the effect of shading correction appropriately. Deterioration of the reading system due to contamination of the system or aging can not be properly determined, and there is a problem that image quality is deteriorated.
[0013]
In particular, when a document is read at the time of transmission by the facsimile apparatus, the image quality of the read result cannot be recognized by the operator on the transmission side, maintenance is not properly performed, and the image quality is continued to be used in a state where the image quality is reduced. Results.
[0014]
The present invention determines the correction accuracy of shading correction before scanning a document, thereby preventing deterioration of the optical system and quality due to dust and scratches, and improving image quality. It is intended to provide a reading device.
[0015]
More specifically, the present invention determines the shading correction accuracy based on the binarized image data, thereby making it possible to determine the shading correction accuracy using an image processing process of a normal image reading apparatus. It is intended to provide a reading device.
[0016]
In particular, the invention according to claim 1 determines shading correction accuracy based on binarized image data obtained by binarizing image data of a white reference member a predetermined number of times by changing a binarization threshold, It is an object of the present invention to provide an image reading apparatus capable of performing more precise determination of shading correction accuracy.
[0017]
Another object of the present invention is to provide an image reading apparatus capable of determining shading correction accuracy by increasing a binarization threshold from a low value.
[0018]
A third object of the present invention is to provide an image reading apparatus capable of determining shading correction accuracy by lowering a binarization threshold from a high value.
[0019]
An object of the present invention is to provide an image reading apparatus capable of determining shading correction accuracy based on the appearance of black image data when binarized by changing a binarization threshold. I have.
[0020]
According to a fifth aspect of the present invention, there is provided an image reading apparatus capable of predicting and judging image quality when a document is scanned in advance based on a result of binarizing image data which has been subjected to shading correction by scanning a white reference member. It is intended to provide.
[0021]
An object of the present invention is to provide an image reading apparatus capable of determining image quality based on the appearance of black image data when binarized by changing a binarization threshold. I have.
[0022]
According to a seventh aspect of the present invention, the image quality determination process is performed a plurality of times, and if a predetermined accuracy is not obtained as a result, a warning is output to thereby suppress the influence of transient disturbance such as noise. It is an object of the present invention to provide an image reading apparatus that can determine the image quality while avoiding the problem, recognize the abnormality of the optical system, and improve the image quality.
[0023]
The invention according to claim 8 provides an image reading apparatus that can determine whether an optical system is abnormal due to deterioration of the optical system, scratches, dust, or the like when there is an abnormality in the optical system. The purpose is.
[0024]
It is another object of the present invention to provide an image reading apparatus capable of determining image quality according to a document reading mode.
[0025]
It is another object of the present invention to provide an image reading apparatus capable of preventing or reducing the occurrence of black streaks and background stains on an image obtained by actually binarizing a document.
[0026]
It is an object of the present invention to provide an image reading apparatus capable of preventing or reducing the occurrence of background contamination or the like in an image obtained by actually performing halftone processing on a document.
[0027]
It is another object of the present invention to provide an image reading apparatus capable of performing high-speed processing for determining whether or not black image data is generated and the ratio of generated black image data by hardware.
[0028]
[Means for Solving the Problems]
The invention according to claim 1 is a scanning unit that scans a white reference member and a document using an optical system, and a white reference that stores pixel-based white reference data obtained by the scanning unit scanning the white reference member. Data storage means, shading correction means for shading correction of shading distortion by the optical system on image data obtained by scanning by the scanning means based on the white reference data, and image data shaded by the shading correction means And an image processing unit for performing various image processing on the image reading device,
After scanning the white reference member by the scanning unit and storing the white reference data in the white reference data storage unit, the scanning unit scans the white reference member again before scanning the original. Then, after the image data obtained by scanning the white reference member is subjected to shading correction by the shading correction means based on the white reference data, the image processing means is binarized by a predetermined binarization threshold. The shading correction is performed based on the binarized image data obtained by binarizing the image data of the white reference member, which has been subjected to shading correction by the shading correction unit, with a predetermined binarization threshold value by the image processing unit. Determining means for determining the accuracy,
The image processing unit binarizes the image data of the white reference member subjected to the shading correction by the shading correction unit a predetermined number of times by sequentially changing the binarization threshold value. The shading correction accuracy is determined based on binarized image data that has been binarized by changing the binarization threshold.
[0029]
According to the above configuration, it is possible to determine the correction accuracy of the shading correction before scanning the original, to prevent the deterioration of the optical system and the deterioration of the quality due to dust and scratches, and to improve the image quality. Can be. In particular, the shading correction accuracy can be determined based on the binarized image data, and the shading correction accuracy can be determined using an image processing process of an ordinary image reading device. As a result, the processing for determining the shading correction accuracy can be made simple and easy.
Further, the shading correction accuracy can be determined based on the binarized image data obtained by binarizing the image data of the white reference member subjected to shading correction a predetermined number of times by changing the binarization threshold. Thus, a more precise determination of shading correction accuracy can be made.
[0030]
Further, in the invention according to claim 2, the image processing means performs the binarization by sequentially increasing the binarization threshold from a predetermined low value at predetermined intervals, and the determination means includes Performs the determination of the shading correction accuracy based on the binarization threshold when black image data first appears in the binarized image data binarized by sequentially increasing the binarization threshold. I do.
[0031]
According to the above configuration, the appearance of black image data in the binarized image data when the binarization threshold is increased from a low value is monitored, and shading is performed based on the binarization threshold at that time. The correction accuracy can be determined, and the shading correction accuracy can be determined more accurately and easily.
[0032]
Further, in the invention according to claim 3, the image processing means performs the binarization by sequentially lowering the binarization threshold value from a predetermined high value at predetermined intervals, and the determination means includes: Is characterized in that the shading correction accuracy is determined based on the binarization threshold when all of the binarized image data that has been binarized by sequentially lowering the binarization threshold becomes white image data for the first time. I do.
[0033]
According to the above configuration, the binarized image data when the binarized threshold value is lowered from a high value is monitored, and the shading correction accuracy is determined based on the binarized threshold value when all of the image data becomes white image data. Can be determined, and when the deterioration of the optical system is small, the shading correction accuracy can be determined more quickly, with high accuracy, and easily.
[0034]
According to a fourth aspect of the present invention, in the image processing apparatus, the image processing means may sequentially decrease the binarization threshold at a predetermined interval from a predetermined high value or increase the binary threshold at a predetermined interval from a predetermined low value. The binarization is performed, and the determination unit performs the shading correction based on the appearance of black image data when the image processing unit sequentially lowers or increases the binarization threshold to perform the binarization. It is characterized in that the accuracy is determined.
[0035]
According to the above configuration, it is possible to determine the shading correction accuracy based on the appearance of the black image data when the binarization is performed by changing the binarization threshold, for example, the increase rate or the decrease rate of the black image data. Thus, the shading correction accuracy can be determined more accurately and easily.
[0036]
The invention according to claim 5, wherein a scanning means for scanning a white reference member and a document using an optical system, and a white reference for storing pixel-based white reference data obtained by the scanning means scanning the white reference member. Data storage means, shading correction means for shading correction of shading distortion by the optical system on image data obtained by scanning by the scanning means based on the white reference data, and image data shaded by the shading correction means And an image processing unit for performing various image processing on the image reading device,
After the white reference member is scanned by the scanning means and the white reference data is stored in the white reference data storage means, before the scanning means scans the original, the white reference member is again set to a predetermined value. After the image data obtained by scanning the white reference member by scanning the white reference member is subjected to shading correction by the shading correction unit, the image processing unit performs scanning every time the scanning unit scans the white reference member. Control means for increasing the binarization threshold at predetermined intervals sequentially from a predetermined high value, or decreasing at predetermined intervals sequentially from a predetermined low value, and the image processing means comprising: Are sequentially increased or decreased, and the binarized threshold value when the image data binarized by all becomes white image data for the first time, or before the black image data appears for the first time. It said scanning means on the basis of the binarization threshold, characterized in that it comprises determining means for determining an image quality when scanning the document.
[0037]
According to the above configuration, before scanning the original, the image quality when the original is scanned is predicted and determined in advance before the original is scanned based on the result of binarizing the image data subjected to the shading correction by scanning the white reference member. And the image quality can be improved.
[0038]
According to a sixth aspect of the present invention, in the image processing device, the image processing unit may increase or decrease the binarization threshold by binarizing the binarized image data so that black image data appears in the binarized image data. The determination of the image quality is performed based on
[0039]
According to the above configuration, the image quality can be determined based on the appearance of the black image data when the binarization is performed by changing the binarization threshold, for example, the increase rate or the decrease rate of the black image data, The image quality can be determined more accurately and easily.
[0040]
Further, in the invention according to claim 7, the control means, when the binarization threshold value is equal to or less than a predetermined reference threshold value, performs the image quality determination process from a scan for collecting the white reference data by the scanning means. And if any of the determination results obtained by performing the image quality determination processing a predetermined number of times is equal to or less than the reference threshold, a warning that the optical system is abnormal is output.
[0041]
According to the above configuration, the image quality determination process is performed a plurality of times, and the image quality determination process can be performed while avoiding the influence of a transient disturbance such as noise. Nevertheless, if an appropriate image quality cannot be obtained, a warning can be output, and it can be recognized that there is an abnormality in the optical system. As a result, abnormality of the optical system can be managed more appropriately, repair can be promoted, and image quality can be improved.
[0042]
Furthermore, the invention according to claim 8, wherein the image reading device further includes a black pixel appearance position storage unit that stores an appearance position of the black image data when the binarization threshold is raised or lowered. The determining unit determines that the optical system has an abnormality such as a scratch or dust when the appearance position of the black image data stored in the black pixel appearance position storage unit is continuous with a predetermined local area. It is characterized by.
[0043]
According to the above configuration, when there is an abnormality in the optical system, it is possible to classify and determine whether the abnormality is due to deterioration of the optical system or due to scratches, dust, or the like. Can be determined. As a result, the optical system can be repaired more appropriately.
[0044]
In a ninth aspect of the present invention, the determination unit changes a determination criterion for determining the image quality according to a document reading mode such as a halftone reading mode or a simple binary reading mode. It is characterized by the following.
[0045]
According to the above configuration, the image quality can be determined according to the document reading mode, and the image quality can be determined more appropriately.
[0046]
Further, the invention according to claim 10 is characterized in that the control means changes a binarization threshold value when binarizing image data obtained by scanning the document by the image processing means based on a result of the determination by the determination means. It is characterized by making it.
[0047]
According to the above configuration, the binarization threshold for binarizing image data obtained by actually scanning a document can be changed according to the image quality determination result, that is, the shading correction accuracy. It is possible to prevent or reduce the occurrence of black streaks or background stains on the image, and to improve the image quality.
[0048]
Further, in the invention according to claim 11, the image processing means performs gradation processing on the image data obtained by reading the document to a predetermined gradation, and the control means performs the gradation processing based on the image quality judgment result of the judgment means. And changing the number of gradations at the time of the gradation processing by the image processing means.
[0049]
According to the above configuration, the number of gradations when performing gradation processing on image data obtained by actually scanning an original can be changed according to the image quality determination result, that is, the shading correction accuracy. It is possible to prevent or reduce the occurrence of stains and the like, and to improve the image quality.
[0050]
Further, in the twelfth aspect of the present invention, the determining means determines whether the binarized image data of the white reference member is black image data or not by the determining circuit. A counter for counting the black image data, wherein the determination of the presence / absence of the black image data or the occurrence ratio thereof is performed by hardware.
[0051]
According to the above configuration, it is possible to perform the processing of determining whether or not black image data is generated and the rate of occurrence thereof at a high speed and while reducing the load on software, thereby improving the processing speed of the image reading apparatus. Can be.
[0052]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0053]
It should be noted that the embodiments described below are preferred embodiments of the present invention, and therefore, various technically preferred limitations are given. However, the scope of the present invention is not limited to the following description. The embodiments are not limited to these embodiments unless otherwise specified.
[0054]
FIGS. 1 to 3 show a first embodiment of an image reading apparatus according to the present invention, and this embodiment is applied to a facsimile apparatus.
[0055]
1, a facsimile apparatus 20 includes a system control unit 21, a system memory 22, a parameter memory 23, a scanner 24, a plotter 25, a network control unit 26, a modem 27, an image memory 28, an encoding / decoding unit 29, and an operation panel. The components are connected to a bus 31.
[0056]
The system control unit (control means, determination means) 21 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and the like. The ROM has a basic processing program and a shading correction accuracy determination processing program as the facsimile apparatus 20. And various kinds of programs such as an image quality judging station program, and system data necessary for executing the above-mentioned processes. The system control unit 21 controls the respective units of the facsimile machine 20 using the system memory 22 as a work memory based on a program in the ROM, and executes basic processing as the facsimile machine 20. To perform a shading correction accuracy determination process and an image quality determination process.
[0057]
The parameter memory 23 stores various parameter information necessary for facsimile communication.
[0058]
As shown in FIG. 2, the scanner 24 includes a guide member 42 for guiding a document 41 conveyed by a conveyance roller (not shown). The scanner 24 is attached to the guide member 42, guides the document 41, and removes dust and dirt from the optical system. A target glass 43 for preventing contamination, a white reference plate 44 for correcting shading distortion caused by the optical system, a light source 45 for irradiating the conveyed document 41 and the white reference plate 44 with light, a mirror 47, a lens 46, an image A sensor 48, an amplifier 49, an A / D converter 50, a peak hold circuit 51, a shading correction circuit 52, a line buffer 53, a digital image processing circuit 54, and the like are provided, and the shading correction circuit 52 and the digital image processing circuit 54 , Are connected to the system control unit 21 via a bus 31.
[0059]
When scanning the white reference plate (white reference member) 44, the light from the light source 45 is applied to the white reference plate 44 through the target glass 43, and the light reflected by the white reference plate 44 is An image is formed on the image sensor 48 via the mirror 46 and the lens 47 at a predetermined reduction ratio. When scanning the original 41, light from the light source 45 irradiates the original 41 conveyed on the target glass 43 through the target glass 43, and the light reflected by the original 41 is reflected by the mirror 47 and the lens 46. Is imaged on the image sensor 48 at a predetermined reduction rate.
[0060]
The image sensor 48 converts the formed optical information into an electric signal and outputs the electric signal to the amplifier 48. The amplifier 48 uses, for example, an operational amplifier (op-amp) to convert an analog image input from the image sensor 48. The signal is amplified at a predetermined magnification and output to the A / D converter 50 and the peak hold circuit 51.
[0061]
Therefore, the light source 45, the mirror 46, the lens 47, and the image sensor 48 function as a scanning unit as a whole.
[0062]
The peak hold circuit 51 detects and holds the maximum value (peak value) of the image signal for one line input from the amplifier 48.
[0063]
The A / D (Analog to Digita) converter 50 quantizes the image signal input from the amplifier 49 based on the peak value held by the peak hold circuit 51, and outputs the quantized image signal to the shading correction circuit 52.
[0064]
A line buffer (white reference data storage means) 53 stores, as white reference data, one line of image data output from the A / D converter 50 when the white reference plate 44 is scanned, and performs shading by the shading correction circuit 52. It is referred to in correction and image processing in the digital image processing circuit 54.
[0065]
The shading correction circuit (shading correction means) 52 stores the shading distortion caused by the characteristics of the optical system in the image data input from the A / D converter 50 in the line buffer 53 under the control of the system control unit 21. A shading correction process for performing correction while referring to the image data is performed and output to the digital image processing circuit 54.
[0066]
The digital image processing circuit (image processing means) 54 operates under the control of the system control unit 21 and refers to the image data stored in the line buffer 53 or uses the line buffer 53 to generate a shading correction circuit. The image data input from 52 is binarized, subjected to halftone processing, and various image processing is performed, and stored in the line buffer 22a.
[0067]
The line buffer 22a is for temporarily storing image data binarized or subjected to halftone processing by the digital image processing circuit 54, and uses a part of the system memory 22 of FIG.
[0068]
Therefore, when the scanner 24 scans the white reference plate 44 to obtain white reference data for shading correction, the image signal converted into an electric signal by the image sensor 48 is amplified by the amplifier 49 and the peak hold circuit The digital data is converted by the A / D converter 50 based on the peak value held at 51 and stored in the line buffer 53 via the shading correction circuit 52 as white reference data. Then, as will be described later, when the white reference plate 44 is scanned again in order to determine the shading correction accuracy, the image signal is similarly converted into an electric signal by the image sensor 48 and is converted into a digital signal by the A / D converter 50. After shading correction is performed by the shading correction circuit 52 on the basis of the white reference data of the line buffer 53, the digital image processing circuit 54 binarizes the data and temporarily stores it in the line buffer 22a. The system control unit 21 determines the shading correction accuracy based on the binarized image data in the line buffer 22a.
[0069]
Thereafter, when scanning the original 41, the image signal converted into an electric signal by the image sensor 48 is amplified by the amplifier 49, digitally converted by the A / D converter 50, and then referred to the white reference data of the line buffer 53. Then, shading correction is performed by the shading correction circuit 52, various image processing is performed by the digital image processing circuit 54, and the image data is transferred to the line buffer 22a.
[0070]
The processing for determining the shading correction accuracy using the scanner 24 will be described later in detail.
[0071]
Although not shown, the scanner 24 generally includes an automatic document feeder (ADF), and the ADF sends the set plurality of originals 41 one by one to the target glass 43, that is, the reading unit. Pay.
[0072]
In FIG. 1 again, as the plotter 25, for example, a thermal recording device using a thermal element or an electrophotographic recording device is used. When the thermal recording device is used, the plotter 25 Images are recorded directly or indirectly on ordinary recording paper via ink sheets.
[0073]
The network control unit 26 is connected to a modem 27, and a line (for example, a telephone line) is connected to the network control unit 26. The network control unit 26 operates under the control of the system control unit 21 to automatically receive an incoming call from a line, perform an automatic call processing to the line, and perform communication between the line and a partner facsimile machine. The facsimile communication procedure is executed by exchanging facsimile control signals, setting communication functions and exchanging various kinds of control information.
[0074]
The modem 27 operates under the control of the system control unit 21, modulates a transmission signal, and demodulates a reception signal.
[0075]
The image memory 28 includes, for example, a large-capacity RAM (Random Access Memory) or a hard disk device, and mainly stores image data. That is, image data for transmission read by the scanner 24 and received image data are accumulated in the image memory 28, and are read out at a predetermined time under the control of the system control unit 21 to perform transmission processing, recording processing, and the like. Offered to
[0076]
The encoding / decoding unit 29 shortens the transmission time of image data and increases the efficiency of storage in the image memory 28. The encoding / decoding unit 29 compresses (encodes) the image data at the time of transmission, and encodes the image data at the time of reception. The decoded image data is reproduced (decoded) into original image data.
[0077]
The operation panel 30 includes various operation keys such as a numeric keypad, a start key, a stop key, and a function key, and also includes a display (for example, a liquid crystal display). Various commands such as a transmission operation are input from the operation keys. You. The display of the operation panel 30 displays the contents of commands input from the operation keys and various information notified to the operator from the facsimile machine 1, and also provides a result of determination of shading correction accuracy and image quality, which will be described later, and a notification of an abnormality. Are displayed and output.
[0078]
Next, the operation will be described.
[0079]
In the present embodiment, after the white reference plate 44 is scanned to obtain white reference data, the white reference plate 44 is scanned a predetermined number of times again before reading the document 41, and the shading correction accuracy and image The characteristic is that the quality is determined.
[0080]
Hereinafter, the shading correction accuracy processing and the image quality determination processing will be described based on the flowchart of FIG.
[0081]
When an instruction to read the document 41 is input from the operation panel 30, the system control unit 21 performs various parameters necessary for reading the document 41 and various parameters necessary for the shading correction accuracy determination processing, particularly, for shading correction accuracy determination. First, the count value of a counter N that counts the number of times of scanning the white reference plate 44 (the number of times of white reference data collection) is initialized (N = 0) (step S1), and the upper limit TH of the number of times of white reference data collection is set. (Step S2). An initial value of the white reference data sampling frequency upper limit TH is set in advance in the ROM in the system control unit 21. In step S2, the initial value is set as the upper limit TH, but the upper limit TH is input from the operation panel 30. By doing so, it can be changed and set.
[0082]
Next, the system control unit 21 determines the original reading mode designated by the operation panel 30, that is, the original reading mode such as the simple binary reading mode or the halftone reading mode for reading a photograph or the like. (Step S3), a correction accuracy determination level LV corresponding to the determined document reading mode, that is, a determination level of the correction accuracy of the shading correction is set (Step S4).
[0083]
The correction accuracy determination level LVH is stored in advance in a ROM or the like for each reading mode, and in each reading mode, a minimum level of shading correction accuracy that does not affect image quality is set.
[0084]
For example, when the document reading mode is the halftone reading mode, a high correction is required as the correction accuracy. Therefore, the system control unit 21 sets a high value as the correction accuracy determination level LV, and sets the simple binary reading mode. Is set to a low value that can guarantee a binary image.
[0085]
Thereafter, the system control unit 21 turns on the light source 45 (LAMP ON) (step S5), first scans the white reference plate 44 to acquire white reference data, and performs A / D conversion according to the above-described procedure. The image data digitally converted by the converter 50 is stored (collected) in the line buffer 53 as white reference data (step S6).
[0086]
Next, the system control unit 21 scans the white reference plate 44 again (step S7), and calculates the shading correction accuracy based on the image data obtained by scanning the white reference plate 44 (step S8). It is checked whether the shading correction accuracy exceeds the correction accuracy determination level LV set in step S4 (step S9).
[0087]
That is, when the image signal obtained by scanning the white reference plate 44 again is converted into a digital signal by the A / D converter 50, the system control unit 21 converts the image signal into white reference data stored in the line buffer 53 in the shading correction circuit 52. Based on the shading correction, the image data subjected to the shading correction is binarized by a predetermined threshold value (threshold level) by the digital image processing circuit 54 and transferred to the line buffer 22a. The system control unit 21 calculates the correction accuracy based on how much black pixels are included in the binarized image data, and determines whether the correction accuracy exceeds the correction accuracy determination level LV set in step S4. Is determined in step S9. The method of calculating the shading correction accuracy is not limited to the above method.
[0088]
In step S9, when the calculated correction accuracy does not exceed the correction accuracy determination level LV, the system control unit 21 increments a counter N for counting the number of white reference data collections (step S10). It is checked whether N exceeds the upper limit TH of the number of times of collection of the white reference data set in step S2, that is, whether the white reference data has been collected up to the upper limit TH of the number of times of collection of the white reference data set in advance (step S11). ).
[0089]
In step S11, when the count number of the counter N does not exceed the upper limit TH of the number of times of collecting the white reference data, the system control unit 21 determines that the white reference data has not been collected up to the preset number of times of collecting the white reference data. Then, returning to step S6, the same processing as described above is performed from the collection of the white reference data. When the white reference data is collected, the white reference plate 44 is again scanned (step S7), and the shading correction accuracy is calculated. (Step S8).
[0090]
When the correction accuracy calculated as described above has not reached the correction accuracy determination level LV, the system control unit 21 increments the counter N in the same manner as described above (step S10), and Is higher than the upper limit TH of the number of times of collecting white reference data (step S11).
[0091]
By performing the above process a predetermined number of times of collecting the white reference data and performing the shading correction process, the influence of noise or the like can be excluded. However, despite the influence of noise or the like being excluded, the upper limit TH is set in step S11. If it exceeds, the system control unit 21 determines that the light source 45, the white reference plate 44, or the optical system such as the mirror 46, the lens 47, and the image sensor 48 has deteriorated or becomes dirty, so that appropriate shading correction accuracy can be obtained. Is determined not to be possible, and the fact is displayed on the display of the operation panel 30. If necessary, a warning sound is generated, a warning is issued, and the shading correction accuracy determination processing ends (step S12). .
[0092]
When the calculated correction accuracy exceeds the correction accuracy determination level LV in step S9, the system control unit 21 determines that appropriate shading correction accuracy has been obtained, and shifts to a normal document 41 reading process. Then, the shading correction determination processing ends (step S13).
[0093]
As described above, in the present embodiment, after the white reference data is collected, the white reference plate 44 is read again to perform shading correction, and the shading correction accuracy at that time is calculated. It is determined whether the shading correction accuracy exceeds the correction accuracy determination level LV set corresponding to the document reading mode. If the shading correction accuracy does not exceed the correction accuracy determination level LV, the white reference data is collected again and the white reference plate is collected. The shading correction is performed on the image data obtained by reading the image data 44 to determine whether the shading correction accuracy has exceeded the correction accuracy determination level LV. If the shading correction accuracy does not exceed the correction accuracy determination level LV even after performing the above-described processing a predetermined number of times, it is determined that the optical system is deteriorated or dirty, and a warning can be issued. Deterioration or contamination of the optical system can be determined in advance based on the accuracy, and an appropriate process can be prompted to the operator. As a result, it is possible to prevent an image of the document 41 having deteriorated image quality from being transmitted without the operator noticing, thereby improving the image quality.
[0094]
FIGS. 4 to 7 are diagrams showing a second embodiment of the image reading apparatus of the present invention. In this embodiment, image data obtained by scanning a white reference plate after collecting white reference data is converted to binary data. In this case, the correction accuracy is determined by sequentially increasing the threshold value to be changed.
[0095]
This embodiment is applied to an embodiment similar to the above-described first embodiment. In the description of the present embodiment, the reference numerals used in the first embodiment are used as they are, This will be described below.
[0096]
In the present embodiment, as shown in FIG. 4, when a reading instruction is given from the operation panel 30, the system control unit 21 performs various initial settings and, in particular, a counter N that counts the number of white reference data collections. Then, a count value of a pixel counter I for counting pixels in one line is initialized (N = 0, I = 0) (step P1), and an upper limit TH of the number of times of white reference data collection is set (step P2). In the present embodiment, the description will be made below assuming that the number of pixels for one line is 2048 pixels.
[0097]
Next, the system control unit 21 sets an initial binarization threshold UPTH and a step width (elevation step) α for increasing the threshold (step P3), and determines the document reading mode designated on the operation panel 30 ( Step P4), a correction accuracy determination level LV corresponding to the determined document reading mode is set (step P5).
[0098]
After that, the system control unit 21 turns on the light source 45 (step P6), first scans the white reference plate 44 to obtain white reference data, and performs the above-described procedure by using the A / D converter 50 in the A / D converter 50. The digitally converted image data is stored in the line buffer 53 as white reference data (step P7).
[0099]
Next, as shown in FIG. 5, the system control unit 21 sets the initial binarization threshold UPTH set in step P3 as the temporary binarization threshold Th (step P8), and again, the white reference plate 44 Is stored in the line buffer 22a as multi-valued image data VID (I) (step P9).
[0100]
When rescanning the white reference plate 44 to determine the correction accuracy, the system control unit 21 increments the pixel counter I by 1, and the multi-valued image data VID (I) of the pixel indicated by the pixel counter I is changed. It is checked whether or not the binarization threshold Th set in step P8 is smaller, that is, whether the multi-valued image data VID (I) of the pixel is smaller than the binarization threshold Th and is black image data (step P11). When the multivalued image data VID (I) of the pixel exceeds the binarization threshold Th, the pixel is determined to be white image data, and the pixel counter I counts one line (2048 pixels). It is checked whether it is (Step P12).
[0101]
If the pixel counter I has not counted one line in Step P12, the process returns to Step P10, and the pixel counter I is incremented in the same manner as described above, and the multi-valued image data of the pixel is similarly processed for the next pixel. It is checked whether VID (I) is smaller than the binarization threshold Th.
[0102]
The above processing is sequentially performed, and if the multi-valued image data VID (I) of all the pixels in one line is white image data (steps P11 and P12), the binarization threshold Th is increased by the increase step α. After the pixel counter I is cleared to "0" (step P13), the process returns to step P10, and the multi-valued image data VID (I) stored in the line buffer 22a is sequentially incremented by only the ascending step α as described above. A comparison is made with the increased binarization threshold Th (step P11).
[0103]
When the same processing as described above is performed and all the multi-valued image data VID (I) is white image data larger than the binarization threshold Th (step P12), the binarization threshold Th is increased again only by the step α. At the same time, the pixel counter I is cleared (step P13), and the same processing as above is performed (steps P10 to P13).
[0104]
When the multi-valued image data VID (I) smaller than the binarization threshold Th, that is, black image data appears in step P11 after performing the above processing, the process proceeds to step P14 to calculate the shading correction accuracy at that time. Then, it is checked whether or not the calculated shading correction accuracy exceeds the correction accuracy determination level LV set in the above step P5 (step P15).
[0105]
If the calculated shading correction accuracy does not exceed the correction accuracy determination level LV in step P15, the system control unit 21 increments a counter N that counts the number of times white reference data is collected (step P16). It is checked whether N exceeds the upper limit TH of the number of times of collection of the white reference data set in step P2, that is, whether the white reference data has been collected up to the upper limit TH of the number of times of collection of the white reference data set in advance (step P17). ).
[0106]
In step P17, when the count number of the counter N does not exceed the upper limit TH of the number of white reference data collections, the system control unit 21 determines that the white reference data has not been collected up to the preset number of white reference collections. Then, returning to step P7 in FIG. 5, the same processing as described above is performed after the collection of the white reference data, and when the white reference data is collected, the initial binarization threshold UPTH is again set to the binary value as shown in FIG. After setting as the threshold value Th (Step P8), the white reference plate 44 is scanned again (Step P9), and whether or not each multi-valued image data VID (I) is smaller than the threshold value Th is determined in the same manner as described above. That is, it is checked whether black image data is included (step P11).
[0107]
The above processing is performed on the multi-valued image data VID (I) for one line, and when the black image data is not included in one line (steps P10 to P12), the system control unit 21 sets the binarization threshold Th to Is increased by an ascending step α (step P13), similarly to the above, it is checked whether or not the multi-valued image data VID (I) includes black image data (steps P10 to P12). When the black image data appears, the correction accuracy is calculated (step P14), and it is checked whether the calculated correction accuracy is higher than the correction accuracy determination level LV (step P15).
[0108]
In step P15, when the calculated correction accuracy is lower than the correction accuracy determination level LV, the system control unit 21 increments the counter N to exceed the upper limit TH of the number of times of collection of the white reference data, as described above. It is checked whether there is any (Step P17), and if not, the process returns to Step P7 to perform the same processing as above (Step P7 to Step P17).
[0109]
The binarization threshold Th was gradually increased to check the shading correction accuracy even though the influence of noise and the like was excluded by performing the redoing of the white reference data and performing the shading correction processing. When the correction reference level LV cannot be obtained and the upper limit TH of the number of times of collection of the white reference data is exceeded, the system control unit 21 determines whether the light source 45 or the white reference plate 44 or the mirror 46 or the lens 47 and the image It is judged that the optical system such as the sensor 48 has deteriorated or becomes dirty, and it is not possible to obtain appropriate shading correction accuracy. This is displayed on the display of the operation panel 30 and, if necessary, an alarm sound is issued. Is generated, a warning is issued, and the shading correction accuracy determination processing ends (step P18).
[0110]
When the calculated correction accuracy exceeds the correction accuracy determination level LV in step P15, the system control unit 21 determines that appropriate shading correction accuracy has been obtained, and shifts to a normal document 41 reading process. Then, the shading correction determination processing ends (Step P19).
[0111]
As described above, in the present embodiment, after the white reference data is collected, the white reference plate 44 is read again, and as shown in FIGS. For each data VID (I), the initial binarization threshold UPTH is compared with the set binarization threshold Th to determine whether the image data is white image data or black image data, and the multi-valued image data VID (I ) Is white image data, the binarization threshold Th is increased by the ascending step α, and it is checked whether black image data is included in the multi-valued image data VID (I) of one line. If all the multi-valued image data VID (I) is white image data, the same check is performed again by increasing the binarization threshold Th by the ascending step α again.
[0112]
In this case, when the shading correction accuracy is high, the multi-valued image data VID (I) from which the white reference plate 44 is read should not include the black image data. For example, as shown in FIG. Black image data is not detected near the upper limit of the initial binarization threshold UPTH + 8α as the binarization threshold Th, but when the shading correction accuracy is low, for example, as shown in FIG. 7, the initial binarization threshold UPTH + 4α , Black image data appears.
[0113]
The shading correction accuracy at the time when the black image data appears is calculated and compared with the correction accuracy determination level LV to determine the shading correction accuracy, and to determine whether to issue a warning or perform the reading process of the document 41. I have decided.
[0114]
Therefore, it is possible to more appropriately and accurately determine the shading correction accuracy.
[0115]
8 to 11 are diagrams showing a third embodiment of the image reading apparatus according to the present invention. In this embodiment, image data obtained by scanning a white reference plate after collecting white reference data is converted to binary data. In this case, the correction accuracy is determined by sequentially lowering the threshold values to be converted.
[0116]
This embodiment is applied to an embodiment similar to the above-described first embodiment. In the description of the present embodiment, the reference numerals used in the first embodiment are used as they are, This will be described below.
[0117]
In the present embodiment, as shown in FIG. 8, when a reading instruction is given from the operation panel 30, the system control unit 21 performs various initial settings and, in particular, a counter N that counts the number of times white reference data is collected. Then, a count value of a pixel counter I for counting pixels in one line is initialized (N = 0, I = 0) (step Q1), and an upper limit TH of the number of times of white reference data collection is set (step Q2). Also, in the present embodiment, a description will be given below assuming that the number of pixels for one line is 2048 pixels.
[0118]
Next, the system control unit 21 sets an uppermost initial binarization threshold value DWTHH for sequentially lowering the binarization threshold value and a step width (decrease step) α for decreasing the binarization threshold value (step Q3). Then, the document reading mode specified by the operation panel 30 is determined (step Q4), and a correction accuracy determination level LV corresponding to the determined document reading mode is set (step Q5).
[0119]
Thereafter, the system control unit 21 turns on the light source 45 (step Q6), first scans the white reference plate 44 to store the white reference data, and stores the white reference data in the line buffer 53 (step Q6). Q7).
[0120]
Next, as shown in FIG. 9, the system control unit 21 sets the initial binarization threshold value DWTHH set in the step Q3 as the provisional binarization threshold Th (step Q8), and again, the white reference plate 44 Is stored in the line buffer 22a as multivalued image data VID (I) (step Q9).
[0121]
When the system control unit 21 rescans the white reference plate 44 for shading correction accuracy determination, the system control unit 21 increments the pixel counter I by one and multi-valued image data VID (I) of the pixel indicated by the pixel counter I. Is smaller than the binarization threshold Th set in step Q8, that is, whether the multivalued image data VID (I) of the pixel is smaller than the binarization threshold Th and is black image data (step Q11). If the multivalued image data VID (I) of the pixel exceeds the binarization threshold Th, the pixel is determined to be white image data, and the pixel counter I counts one line (2048 pixels). It is checked whether the process has been performed (step Q12).
[0122]
If the pixel counter I has not counted one line in step Q12, the process returns to step Q10, and the pixel counter I is incremented in the same manner as described above, and the multi-valued image data of the pixel is similarly processed for the next pixel. It is checked whether VID (I) is smaller than the binarization threshold Th (step Q11).
[0123]
If the above processing is sequentially performed and the multi-valued image data VID (I) of all the pixels in one line is black image data (steps Q11 and Q12), the binarization threshold value Th is reduced by the above-mentioned lowering step α ( (Th = Th−α), and after clearing the pixel counter I to “0” (step Q13), the process returns to step P10, and the multi-valued image data VID (I) stored in the line buffer 22a is converted in the same manner as described above. Is compared with the binarization threshold value Th sequentially lowered by the lowering step α (step Q11).
[0124]
When black image data appears halfway through the same processing as described above (steps Q10 to Q12), the binarization threshold Th is lowered again by the lowering step α, and the pixel counter I is cleared (step Q13). The same processing as described above is performed (steps Q10 to Q13).
[0125]
When the above processing is performed and all the T-value image data VID (i) in one line are white image data, the process proceeds to step Q14, and the shading correction accuracy at that time is calculated (step Q14). It is checked whether or not the shading correction accuracy exceeds the correction accuracy determination level LV set in step Q5 (step Q15).
[0126]
In step Q15, when the calculated shading correction accuracy does not exceed the correction accuracy determination level LV, the system control unit 21 increments a counter N for counting the number of times of white reference data collection (step Q16), and It is checked whether N exceeds the upper limit TH of the number of times of collecting white reference data set in the above step Q2 (step Q17).
[0127]
In step Q17, when the count number of the counter N does not exceed the upper limit TH of the number of times of collection of the white reference data, the system control unit 21 determines that the white reference data has not been collected up to the preset number of times of collection of the white reference data. Then, returning to step Q7 in FIG. 8, the same processing as described above is performed after the white reference data is collected, and when the white reference data is collected, the initial binarization threshold value DWNH is again changed to the binary value as shown in FIG. After setting as the threshold value Th (step Q8), the white reference plate 44 is scanned again (step Q9), and as described above, whether or not each multi-valued image data VID (I) is smaller than the threshold value Th That is, it is checked whether black image data is included (step Q11).
[0128]
The above processing is performed on the multi-valued image data VID (I) for one line, and when black image data is included in one line (steps Q10 to Q12), the system control unit 21 sets the binarization threshold Th to Is lowered by the lowering step α (step Q13), and it is checked whether or not the multi-valued image data VID (I) includes black image data (steps Q10 to Q12) in the same manner as described above. When the black image data does not appear in the data, the correction accuracy is calculated (step Q14), and it is checked whether the calculated correction accuracy is higher than the correction accuracy determination level LV (step Q15).
[0129]
In step Q15, when the calculated correction accuracy is lower than the correction accuracy determination level LV, the system control unit 21 increments the counter N to exceed the upper limit TH of the number of times of collection of the white reference data, as described above. It is checked whether there is any (step Q17), and if not, it returns to step Q7 and performs the same processing as above (steps Q7 to Q17).
[0130]
Despite eliminating the influence of noise and the like by performing redo collection of white reference data and performing shading correction processing, the binarization threshold Th was gradually lowered to check the shading correction accuracy. When the correction reference level LV cannot be obtained and the upper limit TH of the number of times of collection of the white reference data is exceeded, the system control unit 21 determines whether the light source 45 or the white reference plate 44 or the mirror 46 or the lens 47 and the image It is judged that the optical system such as the sensor 48 has deteriorated or becomes dirty, and it is not possible to obtain appropriate shading correction accuracy. This is displayed on the display of the operation panel 30 and, if necessary, an alarm sound is issued. Is generated, a warning is issued, and the shading correction accuracy determination processing ends (step Q18).
[0131]
When the calculated correction accuracy exceeds the correction accuracy determination level LV in step Q15, the system control unit 21 determines that appropriate shading correction accuracy has been obtained, and shifts to a normal document 41 reading process. Then, the shading correction determination processing ends (step Q19).
[0132]
As described above, in the present embodiment, after the white reference data is collected, the white reference plate 44 is read again, and as shown in FIGS. For each data VID (I), the initial binarization threshold DWNH is compared with the set binarization threshold Th to determine whether the image data is white image data or black image data, and multi-value image data VID ( If black image data is included in I), the binarization threshold value Th is lowered by the descending step α, and it is checked whether black image data is included in the multi-valued image data VID (I) of one line. If the black image data is included in the multi-valued image data VID (I) of one line, the binarization threshold Th is further reduced again by the lowering step α, and the same check is performed.
[0133]
In this case, when the shading correction accuracy is high, the multi-valued image data VID (I) from which the white reference plate 44 has been read should not include the black image data. For example, as shown in FIG. Although the black image data is no longer detected when the binarization threshold Th is reduced to the initial binarization threshold DWTHH-2α, if the shading correction accuracy is low, for example, as shown in FIG. Black image data will not be detected until the binarization threshold Th is reduced to about the threshold DWTNH-6α.
[0134]
The shading correction accuracy at the time when the black image data is no longer detected is calculated, and is compared with the correction accuracy determination level LV to determine the shading correction accuracy, and a warning is issued or the original 41 is read. Have decided.
[0135]
Therefore, when the deterioration of the optical system has not progressed more appropriately, the determination of the shading correction accuracy is performed more quickly than when the binarization threshold Th is increased. be able to.
[0136]
12 and 13 are diagrams showing a fourth embodiment of the image reading apparatus according to the present invention. In this embodiment, black image data is included in one line of image data obtained by scanning the white reference plate again. This is detected by hardware as to whether the image data is included or how many black image data are included.
[0137]
This embodiment is applied to a facsimile apparatus similar to that of the first embodiment. In the description of the present embodiment, the same reference numerals used in FIG. .
[0138]
12, in the facsimile apparatus 1 of the present embodiment, a black pixel detection / counting circuit 60 is incorporated in the scanner 24, and the black pixel detection / counting circuit 60 includes an AND circuit 61, a counter 62, and a host interface ( HOST I / F) 63 and the like.
[0139]
The binarized data BIDAT binarized by the digital image processing circuit 54 shown in FIG. 2 is input to the AND circuit 61, and the binarized data BIDAT is supplied to the system memory 22 a via the host interface 63 and the bus 63. Will be forwarded to
[0140]
The AND circuit (determination circuit) 61 further receives a pixel synchronization clock ELCK, which is a transfer synchronization clock for pixel data, and synchronizes the binary data BIDAT from the digital image processing circuit 54 with the pixel synchronization clock ELCK. The data is transferred to the circuit 61 and the host interface 63.
[0141]
The pixel synchronization clock ELCK is a signal that becomes high level “1” at the transfer timing of the pixel data as shown in FIG. 13, and the binarized data BIDAT is “0” when the image data is white image data. , Which is “1” in the case of black image data.
[0142]
When the binary data BIDAT transferred at the timing of the pixel synchronization clock ELCK is black image data, that is, “1”, the AND circuit 61 sends to the counter 62 a black signal that becomes “1” at the rising edge thereof. Output.
[0143]
The counter 62 counts the “1” black signal input from the AND circuit 61 and outputs the count result to the system control unit 21 via the host interface 63.
[0144]
The counter 62 receives the line synchronization signal LNSYC shown in FIG. 13 at its reset terminal R, and the counter 62 clears its count value by the line synchronization signal LNSYC.
[0145]
Therefore, the black pixel detection / counting circuit 60 detects the presence or absence of black image data in one line, counts the black image data in one line, and outputs the detection result and coefficient result to the system control unit 21. I do.
[0146]
That is, as shown in FIG. 13, the black pixel detection / counting circuit 60 converts the binarized binary data BIDAT of the digital image processing circuit 54 transferred from the digital image processing circuit 54 in synchronization with the pixel synchronization clock ELCK. When there is black image data in the AND circuit 61, the black image data is detected by the AND circuit 61, and the AND circuit 61 detects the black image data during one line from the input of the line synchronization signal LNSYC to the next input of the line synchronization signal LNSYC. The detected black image data is sequentially counted by the counter 62 and output to the system control unit 21 via the host interface 63.
[0147]
Therefore, as in the above embodiments, the system control unit 21 reads the white reference plate 44 to collect the white reference data, reads the white reference plate 44 again, and first reads the white reference plate 44. After performing shading correction on the image data obtained when the white reference plate 44 is read again based on the white reference data obtained when is read, the digital image processing circuit 54 binarizes the image data using a predetermined binarization threshold value. By detecting and counting the binarized binary data BIDAT of the digital image processing circuit 54 by the black pixel detection / counting circuit 60, the system control unit 21 determines the shading correction accuracy.
[0148]
As a result, the shading correction accuracy can be determined at high speed while reducing the load on the system control unit 21.
[0149]
14 and 15 are diagrams showing a fifth embodiment of the image reading apparatus of the present invention. In this embodiment, image data obtained by scanning the white reference plate again while sequentially increasing the binarization threshold value The binarization is performed, and software detects whether or not black image data exists in one line of the binarized image data.
[0150]
This embodiment is applied to an embodiment similar to the above-described first embodiment. In the description of this embodiment, the reference numerals used in the above-described first embodiment are used as they are. explain.
[0151]
In the present embodiment, as shown in FIG. 14, when a reading instruction is given from the operation panel 30, the system control unit 21 performs various initial settings and, in particular, resets the count values of the counter N and the pixel counter I. Initialization (N = 0, I = 0) (step R1), the setting of the white reference data sampling upper limit TH, the initial binarization threshold UPTH, and the ascending step α are set (step R2). Also, in the present embodiment, a description will be given below assuming that the number of pixels for one line is 2048 pixels.
[0152]
Next, the system control unit 21 determines the document reading mode designated on the operation panel 30 and sets the correction accuracy determination level LV corresponding to the determined document reading mode (step R3), and turns on the light source 45. (Step R4), the white reference plate 44 is scanned, and the image data obtained by the scanning is stored in the line buffer 53 as white reference data (Step R5).
[0153]
Next, as shown in FIG. 15, the system control unit 21 sets the initial binarization threshold UPTH set in the step R2 as the temporary binarization threshold Th (step R6), and again, the white reference plate 44 (Step R7), the image data obtained by scanning the white reference plate 44 is subjected to shading correction by the shading correction circuit 52, and then binarized, and the binarized image data BID is stored in the line buffer 22a. It is stored as (I) (step R8).
[0154]
That is, the system control unit 21 causes the white reference plate 44 to scan again, and performs shading correction by the shading correction circuit 52 based on the white reference data in the line buffer 53, based on the image data obtained by scanning the white reference plate 44. After that, the image is binarized by the digital image processing circuit 54 using the above-mentioned binarization threshold value Th and stored in the line buffer 22a as the binarized image data BID (I).
[0155]
When the transfer of the binarized image data BID (I) to the line buffer 22a is completed, the system control unit 21 increments the pixel counter I by 1 (step R9), and outputs the data of the pixel indicated by the pixel counter I. It is checked whether or not the binary image data BID (I) is "1", that is, whether or not the image data is black image data (step R10). If the image data is not black image data, the pixel counter I is set to one line (2048 pixels). ) It is checked whether or not counting has been performed (step R11).
[0156]
In step R11, when the pixel counter I has not counted one line, the system control unit 21 returns to step R9, increments the pixel counter I in the same manner as described above (step R9), and performs the next binarization. Similarly, the image data BID (I) is checked whether it is black image data (whether it is "1") (step R10).
[0157]
The above processing is sequentially performed, and if the binarized image data BID (I) of all the pixels in one line is white image data (steps R9 to R11), the binarization threshold Th is increased by the ascending step α. After the pixel counter I is cleared to "0" (step R12), the process returns to step R7, where the white reference plate 44 is scanned again to perform shading correction and binarization, and the binarized image data BID ( I) is stored in the line buffer 22a (steps R7 to R8), and the binary image data BID (I) stored in the line buffer 22a is sequentially checked as to whether it is black image data (steps R9 to R9). R11).
[0158]
When the same processing as described above is performed and all the binarized image data BID (I) is white image data (steps R9 to R11), the binarization threshold Th is increased again by the increasing step α, The pixel counter I is cleared (step R12), and the same processing as above is performed (steps R9 to R11).
[0159]
When the above processing is performed and black image data appears in step R10, the process proceeds to step R13, where the shading correction accuracy at that time is calculated (step R13), and the calculated shading correction accuracy is set in step R3. It is checked whether the correction accuracy determination level LV has been exceeded (step R14).
[0160]
In step R14, when the calculated shading correction accuracy does not exceed the correction accuracy determination level LV, the system control unit 21 increments the counter N for counting the number of times the white reference data is collected (step R15). It is checked whether N exceeds the upper limit TH of the number of times of collection of the white reference data set in the step R2, that is, whether the white reference data has been collected up to the preset upper limit TH of the number of times of collection of the white reference data (step R16). ).
[0161]
In step R16, when the count number of the counter N does not exceed the upper limit TH of the number of times of collecting white reference data, the system control unit 21 returns to step R5 in FIG. When the white reference data is collected, as shown in FIG. 15, the initial binarization threshold UPTH is set as the binarization threshold Th again (step R6), and the white reference plate 44 is again scanned (step R6). R7) In the same manner as described above, after shading correction and binarization and storing as binary image data BID (I) in the line buffer 22a (step R8), the binary image data BID (I) for one line It is checked whether black image data is included (steps R9 to R11).
[0162]
When the black image data is not included in the binary image data BID (I) for one line (steps R9 to R11), the system control unit 21 increases the binary threshold Th by the ascending step α. Th is increased (step R12), and the white reference plate 44 is scanned in the same manner as described above to check whether the binary image data BID (I) subjected to shading correction and binarization includes black image data (step R12). R7 to R11), when black image data appears in step P11, the system control unit 21 calculates the correction accuracy (step R13) and checks whether the calculated correction accuracy is higher than the correction accuracy determination level LV. (Step R14).
[0163]
In step R14, when the calculated correction accuracy is lower than the correction accuracy determination level LV, the system control unit 21 increments the counter N to exceed the upper limit TH of the number of times of collection of the white reference data, as described above. It is checked whether there is any (step R16), and if not, the process returns to step R5 and performs the same processing as above (steps R5 to R16).
[0164]
Despite eliminating the influence of noise and the like by redoing the collection of white reference data and performing shading correction processing, the binarization threshold Th was gradually increased to check the shading correction accuracy. If the correction accuracy determination level LV cannot be obtained and the upper limit TH of the number of times of collection of the white reference data is exceeded, the system control unit 21 obtains appropriate shading correction accuracy due to deterioration or dirt of the optical system. If it is determined that the shading correction cannot be performed, the fact is displayed on the display of the operation panel 30. If necessary, a warning sound is generated, a warning is issued, and the shading correction accuracy determination processing ends (step R17). ).
[0165]
If the calculated correction accuracy exceeds the correction accuracy determination level LV in step R14, the system control unit 21 determines that appropriate shading correction accuracy has been obtained, and shifts to the normal document 41 reading process. Then, the shading correction determination processing ends (step R18).
[0166]
As described above, in the present embodiment, after the white reference data is collected, the white reference plate 44 is read again, and for each of the binarized image data BID (I) subjected to shading correction and binarization, It is determined whether the image data is white image data or black image data. If the binarized image data BID (I) of one line is white image data, the binarization threshold value Th is increased by the ascending step α, and the white reference plate is again set. Scanning is performed to check whether black image data is included in the binary image data BID (I) of one line subjected to shading correction and binarization. If all the binarized image data BID (I) is white image data, the binarization threshold Th is increased again by the ascending step α, and the same check is performed.
[0167]
Therefore, the shading correction accuracy can be more appropriately and accurately determined by software processing without making a major hardware change, and the facsimile apparatus 1 capable of determining the shading correction accuracy is inexpensive. Can be provided. In particular, the circuits in the scanner 24 and the line buffer 22a used for the shading correction accuracy determination processing in the present embodiment are provided in a normal facsimile machine in advance, and in particular, new hardware The determination of the shading correction accuracy can be performed without performing addition.
[0168]
FIGS. 16 to 18 are diagrams showing a sixth embodiment of the image reading apparatus of the present invention. In this embodiment, the image data obtained by scanning the white reference plate again is binarized while sequentially increasing the threshold value. The determination is made by distinguishing between dust and scratches in the optical system and deterioration in the optical system, based on whether or not black image data exists in one line of the binarized image data.
[0169]
This embodiment is applied to an embodiment similar to the above-described first embodiment. In the description of this embodiment, the reference numerals used in the above-described first embodiment are used as they are. explain.
[0170]
In the present embodiment, as shown in FIG. 16, when a reading instruction is given from the operation panel 30, the system control unit 21 performs various initial settings and, in particular, counts the counter N, the pixel counter I, Initialize the count value of the counter M for counting the number of black pixels and the counter L for counting the number of lines (the number of lines where black image data is detected in the local area) (N = 0, I = 0, M = 0, L = 0) (step T1), the upper limit TH1 of the number of times of white reference data collection, the number TH2 of optical system dust / flaw determinations, the initial binarization threshold UPTH, and the ascending step α are set (step T2). Also, in the present embodiment, a description will be given below assuming that the number of pixels for one line is 2048 pixels.
[0171]
Next, the system control unit 21 determines the original reading mode specified on the operation panel 30 and sets the correction accuracy determination level LV corresponding to the determined original reading mode (step T3), and turns on the light source 45. (Step T4), the white reference plate 44 is scanned, and the image data obtained by the scanning is stored in the line buffer 53 as white reference data (Step T5).
[0172]
Next, as shown in FIG. 17, the system control unit 21 sets the initial binarization threshold UPTH set in step T2 as the temporary binarization threshold Th (step T6), and again, the white reference plate 44 Is scanned, and the image data obtained by scanning the white reference plate 44 is subjected to shading correction by the shading correction circuit 52, and then binarized by the digital image processing circuit 54, and the binarized image is stored in the line buffer 22a. The data is stored as data BID (I) (step T8).
[0173]
When the transfer of the binarized image data BID (I) to the line buffer 22a is completed, the system control unit 21 increments the pixel counter I by 1 (step T9), and It is checked whether or not the binary image data BID (I) is "1", that is, whether or not the image data is black image data (step T10). If the image data is black image data, the appearance position of the black image data is indicated. The value of the pixel counter I is held, the counter M is incremented (step T11), and it is checked whether or not the pixel counter I has counted one line (2048 pixels) (step T12). The value of the pixel counter I is stored in the system memory 22, for example.
[0174]
In step T10, when the binary image data BID (I) of the pixel indicated by the pixel counter I is not “1”, that is, when the image data is white image data, the value of the pixel counter I is held and the counter M is The process proceeds to step T12 without incrementing, and checks whether the pixel counter I has counted one line (step T12).
[0175]
If the pixel counter I has not counted for one line in step T12, the process returns to step T9, where the pixel counter I is incremented (step T9), and the same applies to the next binary image data BID (I). It is checked whether the data is black image data (whether it is "1") (step T10).
[0176]
The system control unit 21 sequentially performs the above processing to determine whether the binary image data BID (I) of all the pixels in one line is black image data or white image data, and determines the black image data of the binary image data BID (I). The value of the pixel counter I of the black image data and the counter M are incremented (step T11), and for the white image data, the process proceeds to step T12 without incrementing the value of the pixel counter I and the counter M, and 1 It is checked whether the processing for one line is completed (step T12). When the processing for one line is completed in step T12, it is determined whether the count value of the counter M is positive (M> 0), that is, two out of one line. It is checked whether or not black image data exists in the valued image data BID (I) (step T13).
[0177]
In step T13, if no black image data exists in the binary image data BID (I) in one line, the binary threshold Th is increased by the above-mentioned increasing step α, and the pixel counter I is set to “0”. (Step T14), the process returns to step T7, the white reference plate 44 is scanned again, shading correction and binarization are performed, and the binarized image data BID (I) is stored in the line buffer 22a. The binary image data BID (I) stored (steps T7 and T8) and stored in the line buffer 22a is sequentially checked for black image data in the same manner as described above. While the value of the pixel counter I in which the data has been generated is held, the counter M is incremented. If the data is not black image data, the process directly proceeds to step T12. Te, to check whether performing the processing of one line (step T9~T12).
[0178]
By performing the same processing as above, if all the binarized image data BID (I) is white image data and M is not positive in step T13, the binarization threshold Th is increased again by the increasing step α, The pixel counter I is cleared (step T14), and the same processing as above is performed (steps T7 to T13).
[0179]
When the above processing is performed and the black image data appears in the binary image data BID (I) for one line and the counter M is positive in step T13, the process proceeds to step T15 and the shading at that time is performed. The correction accuracy is calculated (step T15), and as shown in FIG. 18, it is checked whether the calculated shading correction accuracy exceeds the correction accuracy determination level LV set in step T3 in FIG. 16 (step T16).
[0180]
When the calculated shading correction accuracy does not exceed the correction accuracy determination level LV in step T16, the system control unit 21 checks whether or not black image data is re-detected in the local area (step T17).
[0181]
That is, the system control unit 21 determines whether or not the black image data has been re-detected in the local region, based on whether or not the value of the pixel counter I held in step T11 is continuous for a predetermined number.
[0182]
In step T17, when the black image data is not detected again in the local area, the counter N for counting the number of times of collecting the white reference data is incremented (step T18). It is checked whether or not the upper limit TH1 of the number of times of white reference data collection set in the step (1), that is, whether or not the white reference data has been collected up to the preset upper limit TH1 of the number of times of white reference data collection (step T19).
[0183]
In step T19, when the count number of the counter N does not exceed the upper limit TH1 of the number of white reference data collections, the system control unit 21 determines that the white reference data has not been collected up to the preset number of white reference collections. Then, returning to step T5 in FIG. 16, the same processing as described above is performed after the collection of the white reference data, and when the white reference data is collected, the initial binarization threshold UPTH is again set to the binary value as shown in FIG. After the threshold value Th is set (step T6), the white reference plate 44 is again scanned (step T7), and the line buffer 22a is subjected to shading correction and binarization as the binarized image data BID (I) in the same manner as described above. (Step T8), it is determined whether the binary image data BID (I) for one line contains black image data or not. The holds the value of existing pixel counter I of the black image data, increments the counter M for counting the number of occurrences and checks have been processed for one line (step T9~ step T12).
[0184]
When the processing for one line is performed and the black image data is not included in the binary image data BID (I) in the one line, the system control unit 21 increases the binary threshold Th by the ascending step α. After raising the binarization threshold Th and resetting the pixel counter I (step T14), the white reference plate 44 is scanned in the same manner as described above to perform shading correction and binarization of the binarized image data BID (I). Check whether the image data contains black image data, and when the image data is included, the value of the pixel counter I is held and the counter M is incremented (steps T9 to T12).
[0185]
When the processing for one line is performed and the black image data is included in step T13 and the value of the counter M is positive, the correction accuracy is calculated (step T15), and the calculated correction accuracy is determined as the correction accuracy determination level. It is checked whether it is higher than LV (step T16).
[0186]
If the calculated correction accuracy is lower than the correction accuracy determination level LV in step T16, the system control unit 21 checks whether black image data has been re-detected in the local area as described above (step T17). When the black image data is not detected again in the area, the counter N is incremented (step T18), and it is checked whether the upper limit TH1 of the number of times of collection of the white reference data is exceeded (step T19). Returning to step T5 in FIG. 16, the same processing as described above is performed (step T5 to step T19).
[0187]
The binarization threshold Th was gradually increased to check the shading correction accuracy even though the influence of noise and the like was excluded by performing the redoing of the white reference data and performing the shading correction processing. If the correction accuracy determination level LV cannot be obtained and the black image data is not re-detected in the local area, and the upper limit TH1 of the number of times of collection of the white reference data is exceeded, the system control unit 21 sets the optical system It is determined that the S / N ratio is lowered due to the deterioration of the control panel 30 and a warning is displayed on the display of the operation panel 30 to that effect (step P20).
[0188]
When the black image data is re-detected in the local area in step T17, the system control unit 21 increments the counter L for counting the number of lines in which the black image data is detected in the local area (step T21). It is checked whether the count of the counter L exceeds the optical system dust / flaw determination number TH2 set in step T2 of FIG. 16 (step T22), and the counter L counts the optical system dust / flaw determination number TH2. If not, the process proceeds to step T18, where the counter N is incremented (step T18), and it is checked whether the upper limit TH1 of the number of times of collection of the white reference data is exceeded (step T19). In step T19, when the value of the counter N does not exceed the upper limit TH1 of the number of times of collecting the white reference data, the system control unit 21 returns to step T5 in FIG. 16 and performs the same processing as described above (step T5 to step T5). T19, steps T21, T22).
[0189]
In step T22, when the count number of the counter L exceeds the optical system dust / flaw determination number TH2, the system control unit 21 determines that the optical system has dust / flaw, and displays a display to that effect on the operation panel. A warning is displayed on the display 30 and, if necessary, a warning sound is generated to give a warning and terminate the shading correction accuracy determination processing (step T23).
[0190]
When the calculated correction accuracy exceeds the correction accuracy determination level LV in step T16, the system control unit 21 determines that appropriate shading correction accuracy has been obtained, and performs the normal document 41 reading process. The process proceeds to end the shading correction determination processing (step T24).
[0191]
As described above, in the present embodiment, after the white reference data is collected, the white reference plate 44 is read again, and for each of the binarized image data BID (I) subjected to shading correction and binarization, It is determined whether the image data is white image data or black image data. If the binarized image data BID (I) of one line is white image data, the binarization threshold value Th is increased by the ascending step α, and the white reference plate is again set. Scanning is performed to check whether black image data is included in the binary image data BID (I) of one line subjected to shading correction and binarization. If all the binarized image data BID (I) is white image data, the binarization threshold Th is increased again by the ascending step α, and the same check is performed.
[0192]
If the black image data is included in the binary image data BID (I) in one line and the correction accuracy has not reached the correction accuracy determination level LV, the binary image data in the one line is determined a predetermined number of times. It is checked whether the black image data is included in the BID (I) and the black image data is re-detected in the local area. If the black image data is not re-detected in the local area, the S / N ratio due to the deterioration of the optical system is determined. Is judged to be a decrease, a display to that effect is made, and when black image data is re-detected continuously for a predetermined line in the local area, dust is attached to the optical system or it is determined that the optical system is scratched. Judgment is made and a warning is displayed to that effect.
[0193]
That is, black image data generated at a uniform level and randomly occurs is considered to be a noise component (white noise) that is originally superimposed on the reading system (optical system). The S / N ratio may decrease, and image quality may deteriorate depending on the reading mode. Further, when black image data is continuously detected in a specific area, it is considered that dust is attached to the optical system or a local abnormality such as a scratch is present, and the reading system ( Although it is not the deterioration of the optical system itself, the image quality may be deteriorated depending on the reading mode.
[0194]
Therefore, in the present embodiment, when the shading correction is performed several times, and the binarization threshold Th is changed, and the black image data is included in the image data when the white reference plate 44 is read, Depending on whether or not the black image data is continuously detected in the local area, it is determined whether the S / N ratio is lowered due to the deterioration of the optical system (reading system), or whether the black image data is due to scratches or dust in the optical system. It is determined and a display to that effect is displayed.
[0195]
Therefore, it is possible to easily and easily know whether the optical system has been degraded or whether there is a flaw or dust, and an appropriate maintenance process can be performed.
[0196]
As a result, the usability of the facsimile machine 1 can be improved, and the image quality can be improved.
[0197]
FIGS. 19 to 21 are diagrams showing a seventh embodiment of the image reading apparatus of the present invention. In this embodiment, the image data obtained by scanning the white reference plate is binarized by sequentially increasing the binarization threshold. The binarization threshold value for reading a document is set based on the ratio of occurrence of black image data in one line of the binarized image data.
[0198]
This embodiment is applied to an embodiment similar to the above-described first embodiment, and the description of the present embodiment will be made using the reference numerals used in FIGS. 1 and 2 as they are. .
[0199]
[0200]
Next, the system control unit 21 turns on the light source 45 (step V3), scans the white reference plate 44, and stores the scanned image data in the line buffer 53 as white reference data (step V4). ).
[0201]
Next, as shown in FIG. 20, the system control unit 21 sets the initial binarization threshold UPTH set in step V2 as the provisional binarization threshold Th (step V5), and counts the pixel counter I. After resetting the counter L for counting the number of occurrences of the black image data (the number of pixels of the black image data detected in one line) to "0" (step V6), the white reference plate 44 is reset again. After scanning (Step V7), the image data obtained by scanning the white reference plate 44 is subjected to shading correction by the shading correction circuit 52, and then binarized, and the binarized image data BID ( I) (step V8).
[0202]
That is, the system control unit 21 causes the white reference plate 44 to scan again, and performs shading correction by the shading correction circuit 52 based on the white reference data in the line buffer 53, based on the image data obtained by scanning the white reference plate 44. After that, the image is binarized by the digital image processing circuit 54 using the above-mentioned binarization threshold value Th and stored in the line buffer 22a as the binarized image data BID (I).
[0203]
When the transfer of the binarized image data BID (I) to the line buffer 22a is completed, the system control unit 21 increments the pixel counter I by 1 (step V9), and outputs the pixel indicated by the pixel counter I. It is checked whether the binary image data BID (I) is "1", that is, whether the image data is black image data (step V10). If the image data is black image data, the counter L is incremented (step V11). It is checked whether the value of the counter L has exceeded the black pixel detection number determination threshold value TH (step V12).
[0204]
If the value of the counter L does not exceed the black pixel detection number determination threshold value TH in step V12, it is checked whether or not the pixel counter I has counted one line (2048 pixels) (step V13). If the minute count has not been performed, the process returns to step V9, where the pixel counter I is incremented (step V9), and the next binary image data BID (I) is similarly black image data ("1"). (Step V10).
[0205]
The system control unit 21 sequentially performs the above-described processing, determines whether the binary image data BID (I) of all the pixels in one line is black image data or white image data, and determines the counter value for the black image data. L is incremented (step V11), it is checked whether the value of the counter L exceeds the black pixel detection number determination threshold TH (step V12), and the number of appearances of the black image data is set to the set black pixel detection number determination threshold TH. If not, the above process is repeated.
[0206]
In step V13, when the processing for one line is completed without the number of appearances of the black image data reaching the set black pixel detection number determination threshold value TH, the binarization threshold value Th is increased by the increase step α (step V14). ), Returning to step V6, and performing the same processing as described above.
[0207]
The above processing is performed on the newly read image data of the white reference plate 44. When the number of appearances of the black image data, which is the count value of the counter L, exceeds the black pixel detection number determination threshold value TH in step V12, the black image data Is set as a binarization threshold for reading the document 41 based on the number of appearances of the document 41 (step V15), and the reading process of the document 41 is performed using the set binarization threshold (step V15). Step V16).
[0208]
As the binarization threshold value at the time of reading the document 41, for example, the binarization threshold value at the time of reading the document 41 when the shading correction is performed in a completely satisfactory state is set to the maximum level value of the image data of 50. Assuming that the value is set to the% value, a binarization threshold lower than the 50% value is set according to the number of appearances of the black image data.
[0209]
Therefore, the magnitude of the noise level due to the deterioration of the reading system is determined by changing the binarization threshold Th after shading correction of the image data when the white reference plate 44 is read, and changing the binarization threshold Th at that time. By making the determination, the binarization threshold value at the time of reading the document 41 can be reduced and binarized in accordance with the noise level, and the background stain due to noise can be prevented, and the image quality can be improved.
[0210]
That is, as shown in FIG. 21A, if the level of the scanning waveform of the image data when the white reference plate 33 is re-scanned is reduced due to background contamination, etc. If the high-density document is read at the binarization threshold TH without performing the binarization threshold setting process, as shown in FIG. 21B, the image data binarized at the binarization threshold TH is converted into a background image. Black image data due to dirt will appear. However, when the processing of setting the binarization threshold value at the time of reading a document according to the present embodiment is performed, as shown in FIG. 21C, based on the number of black image data generated when the white reference plate 44 is re-scanned. The binarization threshold value at the time of reading the original can be reduced from the binarization threshold value TH to the binarization threshold value TH ′, and the binarization can be performed. Can be prevented from being included, and the image quality can be improved.
[0211]
FIGS. 22 to 23 are views showing an eighth embodiment of the image reading apparatus of the present invention. In this embodiment, the image data obtained by scanning the white reference plate is binarized by sequentially increasing the binarization threshold. This is for setting the number of gradations when halftone processing is performed on image data obtained by reading a document, based on the occurrence ratio of black image data in one line of the binarized image data.
[0212]
This embodiment is applied to an embodiment similar to the above-described first embodiment, and the description of the present embodiment will be made using the reference numerals used in FIGS. 1 and 2 as they are. .
[0213]
In the present embodiment, as shown in FIG. 22, when a reading instruction is issued from the operation panel 30, the system control unit 21 performs various initial settings (step W1), and sets the black pixel detection number determination threshold value TH. , An initial binarization threshold UPTH and an ascending step α are set (step V2). Also, in the present embodiment, a description will be given below assuming that the number of pixels for one line is 2048 pixels.
[0214]
Next, the system control unit 21 sets the gradation number determination thresholds TH1 and TH2 (step W3), turns on the light source 45 (step W4), scans the white reference plate 44, and scans the light. The image data is stored in the line buffer 53 as white reference data (step W5). Note that the gradation number determination threshold value TH1 and the gradation number determination threshold value TH2 have a relationship of TH1> TH2.
[0215]
Next, as shown in FIG. 23, the system control unit 21 sets the initial binarization threshold UPTH set in step W2 as the temporary binarization threshold Th (step W6), and counts the pixel counter I. After resetting the counter L for counting the number of occurrences of the black image data (the number of pixels of the black image data detected in one line) (set to "0") (step W7), the white reference plate 44 is reset again. After scanning (Step W7), the image data obtained by scanning the white reference plate 44 is subjected to shading correction by the shading correction circuit 52, and then binarized by the digital image processing circuit 54 to be stored in the line buffer 22a. It is stored as the coded image data BID (I) (step W9).
[0216]
When the transfer of the binarized image data BID (I) to the line buffer 22a is completed, the system control unit 21 increments the pixel counter I by 1 (step W10), and outputs the pixel indicated by the pixel counter I. It is checked whether or not the binary image data BID (I) is "1", that is, whether or not the image data is black image data (step W11). If the image data is black image data, the counter L is incremented (step W12). It is checked whether the value of the counter L has exceeded the black pixel detection number determination threshold value TH (step W13).
[0217]
If the value of the counter L does not exceed the black pixel detection number determination threshold value TH in step W13, it is checked whether or not the pixel counter I has counted one line (2048 pixels) (step W14). When the minute count has not been performed, the process returns to step W10, where the pixel counter I is incremented (step W10), and the next binary image data BID (I) is similarly black image data ("1"). Check) (step W11).
[0218]
The system control unit 21 sequentially performs the above-described processing, determines whether the binary image data BID (I) of all the pixels in one line is black image data or white image data, and determines the counter value for the black image data. L is incremented, and it is checked whether the value of the counter L has exceeded the black pixel detection number determination threshold TH. If the number of appearances of black image data has not reached the set black pixel detection number determination threshold TH, the above processing is performed. Are repeated (step W10 to step W14).
[0219]
In step W14, when the processing for one line is completed without the number of appearances of the black image data reaching the set black pixel detection number determination threshold value TH, the binarization threshold value Th is increased by the above-mentioned increasing step α (step W15). ), Returning to step W7 to perform the same processing as described above.
[0220]
The system control unit 21 performs the above-described processing on the newly read image data of the white reference plate 44. In step W13, the number of appearances of the black image data, which is the count value of the counter L, exceeds the black pixel detection number determination threshold TH. And whether the binarization threshold Th at which black image data exceeding the black pixel detection number determination threshold TH has appeared is higher than the high gradation number determination threshold TH1 set in step W3 of FIG. 22 (Th> TH1). Check (step W16), when the binarization threshold value Th is higher than the gradation number determination threshold value TH1, it is determined that the optical system has not deteriorated and shading correction has been performed satisfactorily. A maximum of 64 gradations is set as the number of gradations for the halftone processing of the image data obtained by reading 41 (step W17).
[0221]
When the binarization threshold value Th is lower than the gradation number determination threshold value TH1 in step W16, the system control unit 21 determines whether the threshold value TH is higher than the low gradation number determination threshold value TH2 set in step W3 in FIG. (Th> TH2) is checked (step W18), and when the binarization threshold Th is higher than the gradation number determination threshold TH2, the optical system has deteriorated, but it is determined that the degree of deterioration is low. Then, 32 gradations are set as the gradation number of the halftone processing of the image data obtained by reading the document 41 (step W19).
[0222]
Further, when the binarization threshold value Th is lower than the gradation number determination threshold value TH2 in step W18, the system control unit 21 determines that the optical system is significantly deteriorated, and determines whether the image data of the original 41 is read. 16 gradations are set as the number of gradations for the halftone processing (step W20).
[0223]
When the setting of the number of gradations is completed, the system control unit 21 performs a reading process of the document 41, and performs a halftone process of the image data obtained by reading the document 41 by the number of gradations set by the digital image processing circuit 54. The halftone processing is performed, and the shading correction accuracy determination processing ends (step W21).
[0224]
Therefore, after the image data is subjected to shading correction when the white reference plate 44 is read, the binarization threshold Th is changed, and the magnitude of the noise level due to the deterioration of the reading system is determined based on the number of black image data generated at that time. Then, it is possible to set the number of gradations of the halftone processing when the original 41 is read in accordance with the noise level, and it is possible to perform appropriate halftone processing according to the degree of deterioration of the optical system. . As a result, it is possible to improve the image quality when performing halftone processing.
[0225]
That is, when performing halftone processing on an image obtained by reading the document 41, if the reading system is deteriorated and high gradation processing is performed despite the presence of large noise components, even the noise components are toned, and background contamination is reduced. May occur.
[0226]
However, in this embodiment, since the number of gradations is changed according to the degree of deterioration of the reading system, although there is a decrease in image quality due to a decrease in the number of gradations, noise components can be removed. On the contrary, the image quality can be improved.
[0227]
As described above, the invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above, and can be variously modified without departing from the gist thereof. Needless to say.
[0228]
For example, in each of the embodiments described above, the case where the present invention is applied to the facsimile apparatus 20 has been described. However, the present invention is not limited to the facsimile apparatus, and can be applied to general image reading apparatuses that perform shading correction.
[0229]
In the seventh and eighth embodiments, when the shading correction accuracy is low, the binarization threshold is changed and the number of gradations is set without performing the warning process. May be performed, thereby improving the maintainability and the usability of the facsimile machine 20.
[0230]
【The invention's effect】
The main functions and effects of the image reading apparatus of the present invention are listed below.
(1) It is possible to determine the correction accuracy of shading correction before scanning a document, to prevent deterioration of the optical system and quality due to dust and scratches, and to improve image quality.
[0231]
(2) The shading correction accuracy can be determined based on the binarized image data, and the shading correction accuracy can be determined using an image processing process of a normal image reading device. As a result, the processing for determining the shading correction accuracy can be made simple and easy.
[0232]
(3) It is possible to determine shading correction accuracy based on binarized image data obtained by binarizing image data of a white reference member subjected to shading correction a predetermined number of times by changing a binarization threshold. As a result, more accurate shading correction accuracy can be determined.
[0233]
(4) The appearance of black image data in the binarized image data when the binarization threshold is increased from a low value is monitored, and the shading correction accuracy is determined based on the binarization threshold at that time. The shading correction accuracy can be determined more accurately and easily.
[0234]
(5) Monitor the binarized image data when the binarization threshold is lowered from a high value, and determine the shading correction accuracy based on the binarization threshold when all of the image data becomes white image data. Therefore, when the deterioration of the optical system or the like is small, the shading correction accuracy can be determined more quickly, with high accuracy, and easily.
[0235]
(6) The shading correction accuracy can be determined based on the appearance of the black image data when the binarization is performed by changing the binarization threshold, for example, the increase rate or the decrease rate of the black image data. The shading correction accuracy can be determined accurately and easily.
[0236]
(7) Based on the result of binarizing the image data that has been scanned and shaded by the white reference member and before scanning the document, the image quality when the document is scanned can be predicted and determined in advance, Image quality can be improved.
[0237]
(8) The image quality can be determined based on the appearance of the black image data when the binarization is performed by changing the binarization threshold, for example, the increase rate or the decrease rate of the black image data. The image quality can be determined well and easily.
[0238]
(9) Image quality determination processing can be performed a plurality of times to avoid the influence of transient disturbance such as noise, and image quality determination processing can be performed. If an appropriate image quality cannot be obtained, a warning can be output, and it can be recognized that there is an abnormality in the optical system. As a result, abnormality of the optical system can be managed more appropriately, repair can be promoted, and image quality can be improved.
[0239]
(10) When there is an abnormality in the optical system, it is possible to classify and determine whether the abnormality is due to deterioration of the optical system or due to scratches, dust, etc., and more appropriately determine abnormality in the optical system. can do. As a result, the optical system can be repaired more appropriately.
[0240]
(11) The image quality can be determined according to the document reading mode, and the image quality can be determined more appropriately.
[0241]
(12) The binarization threshold for binarizing image data obtained by actually scanning a document can be changed according to the image quality determination result, that is, the shading correction accuracy, and the binarized image can be changed to black. The image quality can be improved by preventing or reducing the occurrence of streaks and background stains.
[0242]
(13) The number of gradations when gradation processing is performed on image data obtained by actually scanning an original can be changed in accordance with the image quality determination result, that is, the shading correction accuracy. This can be prevented or reduced from occurring beforehand, and the image quality can be improved.
[0243]
(14) It is possible to perform the processing for determining whether or not black image data is generated, the rate of occurrence, and the like at a high speed and with a reduced load on software, thereby improving the processing speed of the image reading apparatus.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram of a facsimile apparatus to which a first embodiment of an image reading apparatus according to the present invention is applied.
FIG. 2 is a main part configuration diagram of the scanner of FIG. 1;
FIG. 3 is a flowchart showing shading correction accuracy determination processing and image quality determination processing by the facsimile apparatus of FIG. 1;
FIG. 4 is a flowchart illustrating shading correction accuracy determination processing and image quality determination processing according to a second embodiment of the image reading apparatus of the present invention.
FIG. 5 is a flowchart showing a process subsequent to the shading correction accuracy determination process and the image quality determination process of FIG. 4;
FIG. 6 shows a waveform and a binarization threshold at the time of rescanning of a white reference plate for explaining the operations of the shading correction accuracy determination processing and the image quality determination processing of FIGS. 4 and 5 when the shading correction precision is good. FIG.
FIG. 7 is a diagram showing a waveform and a binarization threshold at the time of rescanning a white reference plate for explaining the operations of the shading correction accuracy determination processing and the image quality determination processing of FIGS. 4 and 5 when the shading correction precision is poor. .
FIG. 8 is a flowchart illustrating shading correction accuracy determination processing and image quality determination processing according to a third embodiment of the image reading apparatus of the present invention.
FIG. 9 is a flowchart showing a process subsequent to the shading correction accuracy determination process and the image quality determination process of FIG. 8;
FIG. 10 shows a waveform and a binarization threshold at the time of re-scanning of a white reference plate for explaining the operations of the shading correction accuracy determination processing and the image quality determination processing of FIGS. 8 and 9 when the shading correction precision is good. FIG.
FIG. 11 is a diagram showing a waveform and a binarization threshold at the time of re-scanning of a white reference plate for explaining the operations of the shading correction accuracy determination processing and the image quality determination processing of FIGS. 8 and 9 when the shading correction precision is poor. .
FIG. 12 is a circuit configuration diagram of a black pixel detection / counting circuit of a scanner according to a fourth embodiment of the image reading apparatus of the present invention.
FIG. 13 is a timing chart of signals of respective parts of the black pixel detection / counting circuit of FIG. 8;
FIG. 14 is a flowchart illustrating shading correction accuracy determination processing and image quality determination processing according to a fifth embodiment of the image reading apparatus of the present invention.
FIG. 15 is a flowchart showing a continuation of the shading correction accuracy determination process and the image quality determination process of FIG. 14;
FIG. 16 is a flowchart illustrating shading correction accuracy determination processing and image quality determination processing according to a sixth embodiment of the image reading apparatus of the present invention.
FIG. 17 is a flowchart showing a continuation of the shading correction accuracy determination process and the image quality determination process of FIG. 16;
FIG. 18 is a flowchart illustrating a further subsequent process of the shading correction accuracy determination process and the image quality determination process of FIG. 17;
FIG. 19 is a flowchart illustrating a shading correction accuracy determination process and an image quality determination process for setting a binarization threshold when reading a document according to the seventh embodiment of the image reading apparatus of the present invention.
FIG. 20 is a flowchart illustrating a continuation of the shading correction accuracy determination process and the image quality determination process of FIG. 19;
FIG. 21 is a waveform (a) of image data of a white reference plate read by the shading correction accuracy determination processing and the image quality determination processing of FIGS. 19 and 20, the waveform of image data when reading a document, and determination of shading correction accuracy. FIG. 7 is a diagram showing a comparison between a binarization threshold (b) before being set by the processing and the image quality determination processing and a binarization threshold (c) set by the shading correction accuracy determination processing and the image quality determination processing.
FIG. 22 is a flowchart illustrating a shading correction accuracy determination process and an image quality determination process for setting the number of gradations in the halftone process according to the eighth embodiment of the image reading apparatus of the present invention.
FIG. 23 is a flowchart showing a continuation of the shading correction accuracy determination process and the image quality determination process of FIG. 22;
FIG. 24 is a configuration diagram of a main part of a conventional image reading apparatus.
[Explanation of symbols]
20 Facsimile machine
21 System control unit
22 System memory
22a Line buffer
23 Parameter memory
24 Scanner
25 plotter
26 Network control unit
27 Modem
28 Image memory
29 Encoding / decoding unit
30 Operation panel
31 bus
41 manuscript
42 Guide member
43 Target glass
44 White reference plate
45 light source
46 mirror
47 lenses
48 Image Sensor
49 amplifier
50 A / D converter
51 Peak hold circuit
52 Shading correction circuit
53 line buffer
54 Digital Image Processing Circuit
60 Black pixel detection and counting circuit
61 AND circuit
62 counter
63 Host Interface

Claims (12)

Scanning means for scanning a white reference member and a document using an optical system; white reference data storage means for storing pixel-based white reference data obtained by the scanning means scanning the white reference member; Shading correction means for shading correction of shading distortion by the optical system on image data obtained by scanning by the scanning means based on data; An image reading apparatus comprising:
After scanning the white reference member by the scanning unit and storing the white reference data in the white reference data storage unit, the scanning unit scans the white reference member again before scanning the original. Then, after the image data obtained by scanning the white reference member is subjected to shading correction by the shading correction means based on the white reference data, the image processing means is binarized by a predetermined binarization threshold. The shading correction is performed based on the binarized image data obtained by binarizing the image data of the white reference member, which has been subjected to shading correction by the shading correction unit, with a predetermined binarization threshold value by the image processing unit. Determining means for determining the accuracy,
The image processing means binarizes the image data of the white reference member subjected to shading correction by the shading correction means by a predetermined number of times by sequentially changing the binarization threshold,
The image reading apparatus according to claim 1, wherein the determination unit determines the shading correction accuracy based on binarized image data binarized by changing the binarization threshold by the image processing unit. The image processing means performs the binarization by sequentially increasing the binarization threshold from a predetermined low value at predetermined intervals,
The determination unit is configured to perform the shading correction based on the binarization threshold when black image data first appears in the binarized image data binarized by the image processing unit sequentially increasing the binarization threshold. 2. The image reading device according to claim 1, wherein the accuracy is determined. The image processing means performs the binarization by sequentially lowering the binarization threshold at a predetermined interval from a predetermined high value,
The determination unit is configured to perform the shading correction based on the binarization threshold when all of the binarized image data that has been binarized by sequentially decreasing the binarization threshold by the image processing unit becomes white image data for the first time. 2. The image reading device according to claim 1, wherein the accuracy is determined. The image processing means performs the binarization by sequentially lowering the binarization threshold at a predetermined interval from a predetermined high value, or sequentially increasing the binarization threshold at a predetermined interval from a predetermined low value,
The determination unit may determine the shading correction accuracy based on the appearance of black image data when the image processing unit sequentially lowers or increases the binarization threshold and performs the binarization. The image reading device according to claim 1, wherein: Scanning means for scanning a white reference member and a document using an optical system; white reference data storage means for storing pixel-based white reference data obtained by the scanning means scanning the white reference member; Shading correction means for shading correction of shading distortion by the optical system on image data obtained by scanning by the scanning means based on data; An image reading apparatus comprising:
After the white reference member is scanned by the scanning means and the white reference data is stored in the white reference data storage means, before the scanning means scans the original, the white reference member is again set to a predetermined value. After the image data obtained by scanning the white reference member by scanning the white reference member is subjected to shading correction by the shading correction unit, the image processing unit performs scanning every time the scanning unit scans the white reference member. Control means for sequentially increasing the binarization threshold at a predetermined interval from a predetermined high value, or decreasing the binarization threshold at a predetermined interval from a predetermined low value,
The image processing means sequentially increases or decreases the binarization threshold, and the binarization threshold when the image data that has been binarized becomes white image data for the first time, or the black image data appears for the first time. Determining means for determining the image quality when the scanning means scans the document based on the binarization threshold at the time,
An image reading apparatus comprising: The determination unit determines the image quality based on the appearance of black image data in the binarized image data binarized by increasing or decreasing the binarization threshold by the image processing unit. The image reading apparatus according to claim 5, wherein the image reading is performed. When the binarization threshold is equal to or less than a predetermined reference threshold, the control unit causes the scanning unit to perform the image quality determination process from scanning for collecting the white reference data, and performs the image quality determination process. 7. The image reading apparatus according to claim 6, wherein a warning that there is an abnormality in the optical system is output when any of the determination results performed a predetermined number of times is equal to or less than the reference threshold. The image reading device further includes a black pixel appearance position storage unit that stores an appearance position of the black image data when the binarization threshold is increased or decreased.
  The determining unit determines that the optical system has an abnormality such as a scratch or dust when the appearance position of the black image data stored in the black pixel appearance position storage unit is continuous with a predetermined local area. The image reading device according to any one of claims 2 to 7, wherein 6. The image forming apparatus according to claim 5, wherein the determination unit changes a criterion for determining the image quality in accordance with a document reading mode such as a halftone reading mode or a simple binary reading mode. Item 9. The image reading device according to any one of Items 8. 6. The image processing apparatus according to claim 5, wherein the control unit changes a binarization threshold when the image processing unit binarizes the image data obtained by scanning the document based on a determination result of the determination unit. The image reading device according to claim 9. The image processing means performs gradation processing on the image data obtained by reading the document to a predetermined gradation,
10. The image processing apparatus according to claim 5, wherein the control unit changes the number of gradations at the time of the gradation processing by the image processing unit based on a result of the image quality judgment by the judgment unit. An image reading device according to any one of the above. The determination unit includes a determination circuit that determines whether the binarized image data of the white reference member is black image data, and a counter that counts the black image data determined by the determination circuit. 12. The image reading apparatus according to claim 2, wherein a process of determining whether or not the black image data is generated or a generation ratio is performed by hardware.

Images