JP3449490B2 - Image reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reader used in an image reader, a digital copying machine, etc., and more particularly, to a digital image using a plurality of CCD chips. The present invention relates to an image reading apparatus that performs shading correction on a reading level difference of each CCD chip using a shading plate when reading. 2. Description of the Related Art Generally, a CCD chip has different characteristics for each pixel and a different read level. As described above, in an image reading apparatus using a CCD chip having different characteristics for each pixel, it is necessary to correct the reading level difference of each CCD chip in order to stably realize high-quality image reading. Become. Conventionally, in an image reading apparatus using a CCD chip, a reference reading plate (hereinafter referred to as a shading plate) for correcting a reading level difference between the CCD chips is used. And performs shading correction for correcting the read level difference between the CCD chips. In this type of image reading apparatus, if there is slight dirt or dust on the shading plate, dirt on the reading optical system or abnormality of the CCD chip, the corresponding reference reading output of the shading plate is not uniform. In an image formed by image reading output which has been subjected to shading correction based on such data, a vertical streak occurs in the abnormal portion or the image quality deteriorates, so that correct image data can be obtained. Can not. In order to solve such a problem in the image reading device, there has been proposed a device in which the reading position of the shading plate is changed when there is an abnormality in the CCD reading data of the shading plate (for example, Japanese Patent Laid-Open Publication No. HEI 9 (1994) -209686). 3-7466). [0006] The C of the shading plate
When the CD read data is abnormal, as described above,
If the reading position of the shading plate is changed, the influence of dirt and dust on the shading plate can be avoided.However, if there is an abnormality such as a large dirt on the shading plate or dirt on the reading optical system, the abnormality detection and There is a problem that the influence cannot be avoided. [0009] An object of the image reading apparatus according to the present invention is as follows.
In the case of an abnormality such as a large stain on the shading plate or a stain on the reading optical system, it is determined whether the shading plate is dirty, the reading optical system is dirty, or the CCD chip is abnormal. An image reading device according to the present invention is a reference reading plate for correcting a reading level difference of each CCD chip in an image reading device for reading a digital image using a plurality of CCD chips. A shading plate, shading data storage means for storing read data of the shading plate before reading the current document, or storing read data of a standard shading plate stored in advance before reading the current original, and the shading data Shading correction means for calculating the output of the storage means and the actual read data of the original to correct the read level difference of each CCD chip;
The average value from the read data for each CCD of the shading plate, and calculating means for calculating a maximum value and the minimum value, the Shedin the output data of the calculating means
Check whether there is any abnormality in the reading data of the board
If the data read from the shading plate is abnormal,
Read each other location of the shading plate to each CCD.
Determining means for determining, based on the read data , whether the abnormality of the read data is based on the contamination of the shading plate or the abnormality of the CCD chip. [0013] [0014] [0015] [action] said determining means, there is an abnormality in the read data of the shading plate on the basis of the output data of the calculating means
Check the CCD reading of the shading plate
When data is abnormal, the above shading is applied to the CCD.
Read another part of the board and read the data.
It is determined whether the abnormality of the read data is based on the contamination of the shading plate or the abnormality of the CCD chip. [0016] [0017] According to the image reading apparatus according to the present invention, the shading plate on the basis of the output data of the calculating means
Of detecting an abnormality in the read data, so the abnormality can be determined whether one or CCD chip abnormality in based on the contamination of the shading plate, the maintenance of the image reading apparatus is facilitated. Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a digital color copying machine (hereinafter simply referred to as a copying machine) provided with an image reading apparatus according to an embodiment of the present invention. The configuration will be described below in the order of the items. (1) Image Reader Unit 30 The image reader unit 30 scans an image of a document placed on a document table 31 by exposing and scanning with a scanner 32, and uses an image sensor of a photoelectric conversion unit 201 arranged in plurals. ,
After photoelectrically converting the reflected light of the image, the image signal processing unit 3
At 30, predetermined processing is performed to generate digital image data for driving the laser diode, and the print head (P
H) Transmit to the control unit 335. The drive of the scanner 32 is performed by a pulse motor 35. FIG. 2 shows an example of the configuration of the image sensor of the photoelectric conversion unit 201. The image sensor (CCD sensor for color) is a contact type color CCD sensor in which five high-sensitivity CCD sensor chips are arranged in a zigzag pattern, and A4
The original can be read at a resolution of 400 DPI. Also, in order to separate the reflected light from the original color, R, G, and B filters are applied to each pixel, and the R, G, and B filters are applied to the monochrome CCD sensor. It will be the same as The filter of the color CCD sensor is inclined by 45 degrees as shown in FIG. Returning to FIG. 1, a shading plate 33 made of a white plate for obtaining a reference white output is arranged at a predetermined position of the document table 31 in the copying machine. The data read from the shading plate 33 and the data read from the original document are calculated to correct unevenness of the exposure lamp, the light amount of the optical system, and the variation of the CCD sensor chip of the image sensor of the photoelectric conversion unit 201. (2) Printer Unit 20 The printer unit 20 includes an image forming unit, a developing unit, and a paper processing unit. Hereinafter, the configurations of the image forming unit, the developing unit, and the sheet processing unit will be sequentially described. (2-1) Imaging Unit The imaging unit writes an electrostatic latent image on the surface of the photosensitive drum 4 by the laser unit 21 driven by the digital image data and the like, and develops the toner by the developing unit 6. After doing
The image is transferred onto the paper surface on the transfer drum 10. The photosensitive drum 4 and the transfer drum 10 are driven in synchronization by a drum drive motor 22. (2-2) Developing Unit 6 The developing unit 6 includes a magenta developing device 6M for developing with magenta toner, a cyan developing device 6C for developing with cyan toner, and a yellow developing device for developing with yellow toner. 6Y, a black developing unit 6K for developing with black toner. Above the developing unit 6, four toner hoppers (not shown) for supplying the toners of the colors corresponding to the developing units 6M, 6C, 6Y and 6K are provided. The vertical movement of the developing unit 6 is performed by a developing unit motor 61. (2-3) Paper Processing Unit The paper processing unit transports the paper drawn from any of the storage cassettes 42 to 44 to the transfer drum 1 by a conveying roller group.
After being conveyed to the transfer drum 10 and wound around the transfer drum 10, the toner images on the photosensitive drum 4 are sequentially transferred (up to four colors). Thereafter, the fixing device 4 is separated from the transfer drum 10 and
At 8, the image is fixed, and the sheet is discharged to the sheet discharge tray 49 by the transport belt 47. The timing roller pair 45 is a roller for setting the registration timing. The main motor 41 drives the conveying roller group, the conveying belt 47, and the like. The transfer drum 10 has a tip chuck claw (not shown) for chucking the leading end of the sheet, a suction charger 11 for electrostatically attracting the sheet to the transfer drum 10, a sheet pressing roller 12, a photosensitive member. A transfer charger 14 for sucking and transferring the toner image visualized on the drum 4 onto a sheet of paper, after the transfer of the toner image is completed (in the case of full-color development, the transfer of the toner image for four colors is completed) rear)
In addition, the charge removing chargers 16 and 17 for removing the charge from the transfer drum 10 to separate the sheet and the transfer drum 10
Separating claws 18 and the like for peeling off from the surface are arranged. The sheet that has been subjected to the above copying process is led to the intermediate storage section 50. After the fixing process,
By switching the transport path switching unit 53 installed in the transport path, the sheet is transported downward in FIG. A transport path switching unit 54 is further provided in the transport path. The transported paper is switched back and transported by the reversing device 51, and then the intermediate storage unit 50 is transported.
To be stored directly in the intermediate storage unit 50. After all, when the paper fed from the intermediate storage unit 50 is re-conveyed to the transfer drum 10, this process determines whether the image is transferred to the same surface as the originally printed paper surface or to the back surface. Will choose. The reference position sensor 13 detects a reference position of the transfer drum 10. The actuator plate 13a activates the reference position sensor 13. Note that the detection timing of the reference position and the image reader unit 30 and the printer unit 2
The operation of 0 will be described later. (3) Image processing unit 3 of image reader unit 30
FIG. 4 shows a configuration of the image signal processing unit 330. The electric signal of the original image photoelectrically converted by the image sensor (color CCD sensor) of the photoelectric conversion unit 201 installed in the scanner 32 (see FIG. 1) is amplified by the amplification unit 202, and A / A
The signal is converted into a digital signal by the D converter 203. Next, the shading correction unit 204 performs processing in order to correct unevenness in the amount of light of the exposure lamp 250 and variation in sensitivity of each pixel of the image sensor of the photoelectric conversion unit 201. After performing this process, an image signal of the same level is obtained for each pixel for a uniform density original. The output of the shading correction unit 204 is input to a reflectance / density conversion unit 205. Since the image signal at the preceding stage of the reflectance / density conversion unit 205 is a signal proportional to the amount of reflected light from the original, the reflectance / density conversion unit 205 converts the reflectance to the density so as to facilitate the subsequent processing. Is performed. Further, tone reproduction processing such as highlight section enhancement and shadow section enhancement is also performed in the reflectance density conversion section 205 at the same time. This setting is performed by the setting of the panel unit 300 (see FIG. 7). In each block from the image sensor 201 to the reflectance / density conversion unit 205, the three primary colors (R,
G, B) are processed in parallel. In the color correction unit 206, the three primary colors (R,
G, B) by synthesizing the image signals of Y, Y,
A print output signal of any of M, C, and K is generated. When performing trimming editing, for example, the editing control unit 207 performs erasure outside the designated area. Also,
The MTF correction unit 208 performs edge enhancement and smoothing processing. The scaling / moving unit 209 converts the pixel density in the main scanning direction, shifts the image, and repeatedly outputs the same area.
Perform (image repeat). The gamma correction section 211 can change image quality, color tone, and the like by switching various built-in gamma curve setting ROMs. This gamma correction unit 21
The output of 1 is input to the print head control unit 335.
The laser is controlled by the output of the print head controller 335 to print image data on the photoconductor 4. Each block of the photoelectric conversion unit 201 to the gamma correction unit 211 operates according to a signal (drive pulse or the like) provided from the control signal generation unit 220 and an operation parameter provided from the MPU 210. From the control signal generator 220, a control signal 1 of a low-frequency drive clock set used when capturing shading correction data and a control signal 2 of a high-frequency drive clock set used when capturing actual image data are obtained. Output to the selector 221. The selector 221 can control which control signal is selected by a selection signal from the CPU 230. MPU230
Performs the switching of the driving clock according to the mode with this signal. If the driving clock is delayed when the shading correction data is taken in, the accumulation time of the image sensor of the photoelectric conversion unit 201 becomes longer, so that the voltage applied to the exposure lamp 250 is reduced so that the sensor output is not saturated. Need to be done. This means that the voltage control input of the voltage controllable power supply 240 is connected to the MPU 23
This is achieved by controlling at zero. The MPU 230 operates according to an instruction given via a communication line from an MPU block (MSC) for managing the entire copying machine. CPU 230
Is connected to an external device via a communication line, and can exchange various data with the external device. (4) Panel Unit 300 The panel unit 300 is a block for the user of the copying machine to specify the operation mode of the copying machine. As shown in FIG. 7, the panel section 300 stores the operation information of the copying machine and the C of the shading plate 33.
A liquid crystal display device 301 for displaying various messages including copier maintenance information such as CD read data, a number key 302 for setting the number of copies, a copy start key 303, and the display contents of the liquid crystal display device 301 are different. Various operation keys 30 serving as function operation keys
4,305, etc. Table 1 below shows an example in which the CCD reading data of the shading plate 33 is displayed on the liquid crystal display device 301 of the operation panel 300. [Table 1] In this embodiment, the color CCD sensor is
As shown in Table 1 above, since each chip is composed of five chips of R, G, B readable CCDs, I.I. 1 to 5 chips ... 1 to 5 CCD chips II. R, G, B ... R, G, B readings III. Avr, Max, Min... A total of 49 items of average, maximum and minimum values are displayed. With the above display, it is possible to determine whether each CCD chip is normal or abnormal, and it is easy to specify an abnormal portion and to find the cause. (5) MPU Unit In the copying machine of the embodiment, as shown in FIG. 5, a plurality of MPUs 210, 420, 43 for controlling each operation block.
0, and an MPU 410 that controls the operation of these MPUs 210, 420, and 430. An MPU 4 for controlling the entire copying machine shown in FIG.
10 is an MSC (macro system controller Ma)
cro System Controller), MSU410
Transmits commands necessary for the operation of the target mode to the panel unit 300, the printer unit 20, and the image reader unit 30. The panel unit 300, the printer unit 20, and the image reader unit 30 execute an operation corresponding to the given command, and transmit information to the
SC410. As described above, the exchange of information is performed using the MSC 410 as a core, and the panel unit 300 and the printer unit 20 do not directly perform transmission and reception. FIG. 6 shows an example of the configuration of the A / D conversion section 203 and the shading correction section 204 in FIG. FIG. 6 shows a state of, for example, the R line among the R, G, and B lines. Other lines have the same configuration. A / D converter 1000 converts the input image data (analog value) into, for example, an 8-bit digital value. The A / D converter 1000 receives an A / D conversion clock for digitally converting image data, and at the falling timing of the A / D conversion clock,
The A / D converter 1000 outputs data. The output of the A / D converter 1000 is
010, and the latch 1010 latches the output of the A / D converter 1000 with the latch clock a. In this embodiment, the latch clock a is the same as the A / D conversion clock. When fetching shading correction data, the data is written to the memory 1030 through the buffer 1040. The address of the memory 1030 is stored in an address counter 102 that counts based on a latch clock a.
Input from 0. At the time of capturing actual image data, the latch 101
The output of 0 is input to the address of the memory 1060, and the output of the memory 1030 is also input to the address terminal of the memory 1060 through the latch 1050. The data of the output data corresponding to the address input value is input to the shading correction memory 1060 in advance. Shading correction is performed by passing image data through the memory 1060. The output of the shading correction memory 1060 is supplied to the reflectance / density converter 20 shown in FIG.
5 is input. The shading correction memory 106
0 can be freely read from the IRMPU 210 of FIG.
Can freely perform the reading and the arithmetic processing of the data which has been subjected to the shading reading. The memory 1070 is a data storage memory for shading correction in a normal state (or at the time of shipment).
This memory 1070 is also readable and writable from the IRMPU 210. The memory 1070 temporarily stores the data in the memory 1070 when an error occurs in the shading correction data.
It is used to prevent image deterioration using the shading correction data in 70. (6) Shading Abnormality Detection Processing If the shading plate reading data becomes abnormal due to contamination of the shading plate 33 or the like, as shown in FIG.
In many cases, the data at a location becomes larger or smaller, and this appears as a streak in the read image. FIG. 9 shows a flow of the shading abnormality detection processing. First, in step S1, a reading process of the shading plate 33 is performed. Then, since the read data is stored in the shading correction memory 1060, the data is analyzed in step S2 to check whether there is a data abnormality. If the data is normal (YES), the process proceeds to step S7, and the process ends. On the other hand, if the data is abnormal (NO), the process proceeds to step S3, and another location of the shading plate 33 is read again. Then, the read data is analyzed in step S4, and when the data is normal (YES), there is an abnormality in the shading plate 33 itself (step S4).
6). On the other hand, when the data is abnormal (NO), it is determined that the optical system is dirty or the CCD chip is abnormal (step S5). As described above, even when an abnormality appears in the data read by the shading plate, it is possible to specify whether the cause is the shading plate 33, the optical system, or the CCD chip. Can be done accurately. (7) Calculation of average value, maximum value and minimum value of read data In the calculation flow of average value, maximum value and minimum value of read data shown in FIG. 10, first, in step S21, the flow of FIG. Initialize the variables used in. The contents of the variables are as follows. max: variable for obtaining the maximum value, initial value 0 (minimum value) min: variable for obtaining the minimum value, initial value 255 (maximum value) ave: variable for obtaining the average value, initial value 0 Next, the process proceeds to step S22. Then, it is determined whether the processing of all data of any one of R, G, and B for one chip is completed. If the determination is NO, the process proceeds to step S23. In step S23, one dot data is read from the shading correction memory 1060, and is temporarily stored as variable data. Next, in step S24, the maximum value max up to that point is compared with the read data, and if the data is larger (YES), the flow advances to step S25 to store the data in max. In this way, the maximum value is obtained. Similarly, steps S26 and S27
Find the minimum value with. In step S 28, first, each read data “data” is added to “ave” in order to finally obtain the average value. Next, when the processing is terminated in S22 (N
O), and proceed to step S29. The ave added in step S28 is divided by the total number of dots to obtain an average value. When the above flow is completed, each variable is
The maximum, minimum, and average values will be included. This process is performed for 1 to 5 chips and the R, G, B data of each chip, and displayed on the operation panel. (8) Correction processing when shading is abnormal FIG. 11 shows a correction processing flow when the shading plate read data becomes abnormal due to contamination of the shading plate 33 or the like. First, in step S10, a shading plate reading process is performed. And the read data is
Since the data is stored in the shading correction memory 1060, the data is analyzed in step S11 to check whether there is any data abnormality. If there is an abnormality (YES), the process proceeds to step S12, and the shading correction data at that time is stored in the normal data storage memory 1.
070. This processing is to make it possible to always use the most recent normal data when an abnormality occurs in the shading correction data. Next, step S14 is executed, and shading correction processing is performed using the shading correction data read in step S10. On the other hand, if it is abnormal (NO) in step S11, the shading correction data cannot be used. Therefore, step S13 is performed to perform shading correction processing at the time of abnormality. Specifically, the normal-time shading correction data is read from the normal-time data storage memory 1070, and is written to the shading correction memory 1060. Then, shading correction processing is performed using the written shading correction data. By performing the processing described above,
Even if an abnormality occurs in the shading correction data, the image can be read without causing image deterioration by using the previous normal shading correction data instead. In the above embodiment, an embodiment in which the present invention is applied to a copying machine has been described. However, the present invention is not limited to a copying machine, but may be applied to, for example, an image input device for inputting image information or the like to a computer. Can also be applied.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing a configuration of a copying machine provided with an image reading device according to the present invention. FIG. 2 is a diagram illustrating the structure of an image sensor. FIG. 3 is an explanatory diagram of an arrangement of a filter of the image sensor of FIG. 2; 4 is an explanatory diagram of a configuration of an image signal processing unit in the copying machine of FIG. 5 is an explanatory diagram of a configuration of an MPU of the copying machine in FIG. FIG. 6 is an explanatory diagram illustrating an example of a configuration of an A / D conversion unit and a shading correction unit in FIG. 5; 7 is a perspective view of an operation panel of the copying machine shown in FIG. FIG. 8 is an explanatory diagram of shading plate read data when an abnormality occurs due to contamination of the shading plate or the like. FIG. 9 shows a processing flow for detecting a shading abnormality. FIG. 10 shows a maximum value of data read by a shading plate,
The flow of calculating the minimum value and the average value is shown. FIG. 11 shows a flow of a correction process when shading plate read data becomes abnormal. [Description of Signs] 30 Image reader unit 31 Document table 32 Scanner 32a Exposure lamp 33 Shading plate (reference reading plate) 201 Image sensor 202 Amplification unit 203 A / D conversion unit 204 Shading correction unit 205 Reflection density conversion unit 206 Color correction Unit 207 edit control unit 208 MTF correction block 209 scaling unit 211 gamma correction unit 300 panel unit 330 image signal processing unit 335 panel unit 1060 shading correction memory 1070 normal data storage memory

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-99369 (JP, A) JP-A-62-281675 (JP, A) JP-A-4-1199071 (JP, A) JP-A-2- 143678 (JP, A) JP-A-63-52575 (JP, A) JP-A-4-271663 (JP, A) JP-A-63-290071 (JP, A) JP-A-3-7466 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 1/40

Claims (1)

(57) [Claim 1] In an image reading apparatus for reading a digital image using a plurality of CCD chips, a shading plate as a reference reading plate for correcting a reading level difference of each CCD chip is provided. A shading data storage means for storing the read data of the shading plate and storing the read data of the shading plate before reading the current document or the read data of the standard shading plate stored in advance; and an output of the shading data storage means. And shading correction means for calculating the read level difference of each CCD chip, and calculating the average value, maximum value and minimum value from the read data for each CCD of the shading plate. Calculating means, and output data of the calculating means. The shading plate by
Check whether there is any abnormality in the read data of
If the data read from the shading plate is abnormal,
Read another location of the above shading plate by CCD
An image reading apparatus comprising: a determination unit configured to determine, based on the read data , whether the read data is based on a stain on the shading plate or the CCD chip.