JP4507432B2 - Image reading device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus, and more particularly, to an image reading apparatus with improved document reading position correction and skew correction functions.
[0002]
[Prior art]
In Japanese Patent Laid-Open No. 08-214771, black data and white data having a width of one main scan are obtained by averaging a plurality of lines and used as black reference data and white reference data to perform shading correction and perform image correction processing. It is disclosed.
[0003]
Conventionally, in an image reading apparatus such as a copying machine, even if a document is set normally, the image reading apparatus is composed of multiple parts. There is a problem that a deviation of the document reading position occurs due to the inclination of the image.
[0004]
[Problems to be solved by the invention]
Conventionally, document reading image position correction and inclination (skew) correction in an image reading apparatus are performed by reading a sample image at the time of factory production or market setting, and comparing and measuring the sample image and the output image of the image reading apparatus. Correction processing was performed.
[0005]
However, such an artificial correction processing work increases the number of work steps and makes it difficult to increase the accuracy.
[0006]
In view of the above problems, an object of the present invention is to automate document reading image position correction and tilt (skew) correction, and to perform high-precision correction processing and obtain an image with little variation. To provide an apparatus.
[0007]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above problems.
[0008]
According to the first aspect of the present invention, there is provided an image reading apparatus, wherein a document image is placed outside a reading area of a document on a vertical scale and a horizontal scale arranged in a vertical direction and a horizontal direction of a document glass table on which the document is placed. Provided with a plurality of black reference detection units that are read by an optical scanning means for reading , based on each black reference detection value that is the distance from the read actual document reading region end to each black reference detection unit , In an image reading apparatus comprising means for detecting a deviation or skew in a document reading position caused by a component mounting position, installation conditions, etc., and correcting the output position of the read image and skew correction, the output position correction and skew of the read image means for correcting the JP in the black reference detection unit of the plurality of respective performs multiple detection, the use of average values of the detected value detected this several times as the black reference detection value To.
[0009]
According to a second aspect of the present invention, in the image reading apparatus according to the first aspect , the means for correcting the output position and the skew correction of the read image determines whether the average value is within a predetermined upper and lower limit range. , The average value is used as the black reference detection value.
[0010]
According to a third aspect of the present invention, in the image reading apparatus according to the first aspect , the means for correcting the output position and the skew correction of the read image is an average value of the detected values detected a plurality of times before the power of the apparatus is turned on. The average value of the detected value is taken and it is determined whether the average value is within a predetermined upper and lower limit range. If it is determined that the average value is included, the average value is detected as the black reference detection value. It is used as a value.
[0011]
According to a fourth aspect of the present invention, in the image reading apparatus according to the second or third aspect , the means for performing output position correction and skew correction of the read image is such that each of the average values falls within a predetermined upper and lower limit value range. If it is determined that the detected value is not, the detected value that has already been detected is reset, and each of the plurality of black reference detection units performs detection a plurality of times, and an average value of the detected values that are detected a plurality of times is calculated. The calculation process is performed a predetermined number of times.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
[0013]
FIG. 1 is a perspective view showing a part of the structure of an image reading apparatus according to the present invention.
[0014]
In the figure, reference numeral 1 denotes a first mirror unit, 2 denotes a second mirror unit, and 9 denotes a pulse motor, which are provided at the lower part of an original glass plate of the image reading apparatus. The first mirror unit 1 includes a light source (not shown) and a first mirror supported at both ends, and the second mirror unit 2 includes a second mirror similarly supported at both ends. These mirror units 1 and 2 are driven by a pulse motor 9 in response to an image reading request signal for each line sent from a host computer (not shown), and move along the original at a speed of 2: 1. The image is read sequentially.
[0015]
2 is a front view showing a part of the structure provided under the original glass table of the image reading apparatus according to the present invention, and FIG. 3 is a plan view showing the structure near the original glass table of the image reading apparatus according to the present invention. It is.
[0016]
In these drawings, 10 is a document reading area (shaded area), 11 is a CCD sensor reading area, 12a, 12b, and 12c are black reference detection parts, 13 is a document glass table, 14 is a vertical scale, 15 is a horizontal scale, 16 Is a white reference plate.
[0017]
In this image reading apparatus, an image of a document placed on the document glass table 13 is illuminated from below by a light source (not shown), and the reflected light is reflected from a first mirror, a second mirror, and a second mirror (not shown). The image is formed by the imaging lens through the three mirrors, and the formed image is converted into an electrical signal by a reading sensor such as a CCD, and then transmitted to a host computer (not shown).
[0018]
White reference plates 16 for correcting the image white level are provided on the bottom surface of the vertical scale 14 provided at the end portion of the original glass table 13, and both end portions of the white reference plate 16 in the main scanning direction. Black reference detectors 12 a and 12 b are provided outside the original reading area 10, and a black reference detector 12 c is provided outside the original reading area 10 in the sub-scanning direction of the bottom surface of the horizontal scale 15.
[0019]
The read image position correction value and the inclination (skew) correction value are moved by moving the first mirror unit 1 to each of the black reference detection units 12a, 12b, and 12c during the homing operation or the shading operation when the apparatus is ON. The distance is obtained by measuring with the first mirror unit 1.
[0020]
Here, the distance between one black reference detection unit 12a and the end of the document reading area 10 in the sub-scanning direction is a, and the distance between the other black reference detection unit 12b and the end of the document reading area 10 in the sub-scanning direction is b. When the distance between the black reference detection units 12a and 12b is c, and the distance between the black reference detection unit 12c and the end of the document reading area 10 in the main scanning direction is d,
Read image position correction value (sub-scanning direction) = (a + b) / 2
Read image position correction value (main scanning direction) = d
Inclination (skew) value = (a − b) / c
Can be expressed as
[0021]
The distances a, b, and c measured by the first mirror unit 1 are compared with predetermined upper and lower limit values after each correction value is calculated by the above method, that is, when there is a relationship shown below: This is adopted as a reference value for the read image position correction value and the inclination (skew) value.
[0022]
Read image position correction value (sub-scanning direction) α1 <(a + b) / 2 < β1
Read image position correction value (main scanning direction) α2 <d < β1
Inclination (skew) value α3 <(a − b) / c < β3
Each correction value measured and determined in this way is adopted as a reference value during image processing and is subjected to predetermined processing, so that an inclination ( An image having no skew can be acquired.
[0023]
FIG. 4 is a flowchart showing a processing procedure of read image position correction (sub-scanning direction) according to the present invention.
[0024]
In the figure, first, the black reference positions are detected a plurality of times by the respective black reference detectors 12a and 12b, and the detected values a1, a2, a3,... Am and the detected values b1, b2, b3,. Further, an average value ax = (a1 + a2 + a3 +... Am) / m and an average value bx = (b1 + b2 + b3 +... Bm) / m are obtained (step 1). The detected values a1, a2, a3,... Am and the detected values b1, b2, b3,... Bm detected here are detected at least 4 at a time, and the maximum value and the minimum value among the detected values are detected. Adopt value excluded. By performing such processing, it is possible to prevent an abnormal detection value from being detected for some reason. Next, with respect to the average values ax and bx of the detection values calculated this time, for the respective previous times, for example, using the average values a0 and b0 of the detection values acquired before turning on the power of the device, Average values ay = (a0 + ax) / 2 and by = (b0 + bx) / 2 of the current and previous detection values are calculated (step 2). Whether the average value (ay + by) / 2 calculated based on the average value calculated in step 2 is within a predetermined upper and lower limit value, that is, within a range of α1 <(ay + by) / 2 <β1. It is determined whether or not (step 3). If the predetermined upper and lower limit values are not exceeded, the calculated average value (ay + by) / 2 is adopted as the reference value, the read image position correction process is performed (step 4), and then the read image output process is performed. (Step 5). If it is determined in step 3 that the predetermined upper and lower limit values have been exceeded, whether or not the average value (a0 + b0) / 2 of the detection values detected when the power was last turned on is in the range of α1 <(a0 + b0) / 2 <β1. Is determined (step 6). If this does not exceed the predetermined upper and lower limit values, the average value (a0 + b0) / 2 based on the previously detected detection value is adopted as the reference value, and the read image position correction process is performed (step 7). If the predetermined upper and lower limit values are exceeded in step 6, either one of the upper and lower limit values α1 or β1 is adopted as a reference value to perform the read image position correction process (step 8).
[0025]
FIG. 5 is a flowchart showing a processing procedure of read image position correction (sub-scanning direction) according to the present invention, which is different from the processing procedure of FIG.
[0026]
In the figure, first, each black reference position is detected a plurality of times at each black reference position 12a, 12b, and detection values a1, a2, a3,... Am and detection values b1, b2, b3,. Further, the average value ax = (a1 + a2 + a3 +... Am) / m and the average value bx = (b1 + b2 + b3 +... Bm) / m are obtained (step 11). Here, the detected values a1, a2, a3,... Am and the detected values b1, b2, b3,. Next, with respect to the average values ax and bx of the detection values calculated this time, for the respective previous times, for example, using the average values a0 and b0 of the detection values acquired before turning on the power of the device, The average values ay = (a0 + ax) / 2 and by = (b0 + bx) / 2 of the current and previous detection values are calculated. (Step 12). Whether the average value (ay + by) / 2 calculated based on the average value calculated in step 12 is within a predetermined upper and lower limit value, that is, is in a range of α1 <(ay + by) / 2 <β1. It is determined whether or not (step 13). If the predetermined upper and lower limit values are not exceeded, the calculated average value (ay + by) / 2 is adopted as a reference value, read image position correction processing is performed (step 14), and then read image output processing is performed. (Step 15). If the predetermined upper and lower limit values are exceeded in step 13, it is determined whether the processing from step 11 to step 13 has been performed a predetermined number of times (step 19). If it has been performed a predetermined number of times, it is determined whether or not the average value (a0 + b0) / 2 of the detection values detected when the power is turned on last time is in the range of α1 <(a0 + b0) / 2 <β1 (step 16). If this does not exceed the predetermined upper and lower limit values, the read image position correction process is performed using the average value (a0 + b0) / 2 based on the previously detected detection value as a reference value (step 17). If the predetermined number of times is not performed in step 19, the detection values a1, a2, a3,... Am and the detection values b1, b2, b3,. The processes from are repeated (step 20). If the predetermined upper and lower limit values are exceeded in step 16, either the upper or lower limit values α1 or β1 is adopted as a reference value, and the read image position correction process is performed (step 18).
[0027]
Although the processing procedure of the read image position correction (sub-scanning direction) has been described here, other read image position correction (main scanning direction) and inclination (skew) value correction can be performed by the same processing procedure. .
[0028]
As described above, according to the present invention, at least three black reference detection units are provided on the vertical scale and the horizontal scale which are the document setting reference, and the distance from the black reference detection unit to each scale end is measured by the CCD sensor. By detecting multiple times and averaging it, an accurate detection value is obtained, and in addition, the CCD sensor may take an abnormal value due to some reason. In order to correct the read image position and the inclination (skew) by using an average value with the detection value detected by the CCD sensor and determining whether the average value is within a predetermined upper and lower limit range. The reference value with high accuracy can be obtained.
[0029]
Further, according to the present invention, when it is determined that the average value is not within the predetermined upper / lower limit value range as described above, the detection value detected when the power is turned on last time is within the predetermined upper / lower limit value range. By adding a process for determining whether or not it is present, it is possible to obtain a highly accurate reference value for correcting the read image position and tilt (skew).
[0030]
Further, according to the present invention, when it is determined that the previously detected detection value is not within the range of the predetermined upper and lower limit values as described above, the upper and lower limit values themselves are adopted as the correction values, which is abnormal. The detection value can be avoided from being adopted.
[0031]
Furthermore, according to the present invention, when it is determined that the average value is not within the range of the predetermined upper and lower limit values as described above, all of the detection values detected this time are reset and the black reference detection unit again. Appropriate detection values can be obtained by adding a process for detecting the black reference position a plurality of times and a process for repeating the averaging process a predetermined number of times.
[0032]
【The invention's effect】
According to the first aspect of the present invention, the plurality of black reference detection units that are read by the optical scanning unit for reading the document image are provided outside the document reading region, and the detection values detected a plurality of times are averaged. By performing correction processing based on the detected black reference detection value, the abnormal detection value (detection of abnormality due to dust, dirt, electrical noise, etc.) does not affect the reference value, and an accurate read image Output position correction and tilt (skew) correction can be performed.
[0033]
According to the second aspect of the present invention, it is possible to avoid the output of an abnormal image by providing means for determining whether or not the averaged black reference detection value is within a predetermined upper and lower limit value. it can.
[0034]
According to a third aspect of the present invention, whether or not an average value of the black reference detection value subjected to the averaging process and the black reference detection value detected and stored last time is within a predetermined upper and lower limit value. By providing the means for determining the abnormal image, the output of the abnormal image can be further avoided.
[0035]
According to the fourth aspect of the present invention, when it is determined that the averaged black reference detection values are not within the predetermined upper and lower limit values, the black reference detection values detected and averaged this time are determined. After resetting, each of the plurality of black reference detection units performs detection a plurality of times, performs an averaging process of the detection values detected a plurality of times, and determines whether the above determination process has been repeated a predetermined number of times. Thus, a more appropriate black reference detection value can be obtained and output of an abnormal image can be avoided.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a part of a structure provided under an original glass table of an image reading apparatus according to the present invention.
FIG. 2 is a front view showing a part of the structure of an original glass table of the image reading apparatus according to the present invention.
FIG. 3 is a plan view showing a part of the structure in the vicinity of the original glass plate of the image reading apparatus according to the present invention.
FIG. 4 is a flowchart showing a processing procedure from acquisition of a read image position correction value to image reading according to the present invention.
FIG. 5 is a flowchart showing a processing procedure from acquiring a read image position correction value according to the present invention different from the processing procedure shown in FIG. 4 to reading an image;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st mirror unit 2 2nd mirror unit 9 Pulse motor 10 Original reading area (shaded part)
11 CCD sensor reading area 12 Black reference detection unit 13 Original glass table 14 Vertical scale 15 Horizontal scale 16 White reference plate

Claims (4)

A plurality of blacks read by an optical scanning means for reading a document image outside a reading area of the document on the vertical scale and the horizontal scale arranged in the vertical and horizontal directions of the document glass table on which the document is placed Document reading position due to the mounting position and installation conditions of parts based on each black reference detection value, which is the distance from the end of the actual document reading area that has been read to each black reference detection section. In an image reading apparatus provided with means for detecting deviation and skew, and correcting the output position and skew of a read image,
The means for correcting the output position and skew correction of the read image is detected a plurality of times in each of the plurality of black reference detection units, and an average value of the detection values detected a plurality of times is used as the black reference detection value. An image reading apparatus characterized by being used. The means for correcting the output position and skew correction of the read image determines whether the average value is within a predetermined upper and lower limit range, and if it is determined that the average value is within the range, The image reading apparatus according to claim 1, wherein the image reading apparatus is used as a reference detection value. The means for correcting the output position and skew correction of the read image takes an average value of the detection values detected a plurality of times and a detection value detected before the apparatus is turned on, and this average value is 2. The image reading apparatus according to claim 1, wherein it is determined whether or not a predetermined upper and lower limit value is within a range, and if it is determined that the average value is determined, the average value is used as the black reference detection value. The means for correcting the output position and skew correction of the read image resets the detection value that has already been detected when it is determined that the respective average values are not within the predetermined upper and lower limit values, 4. The method according to claim 2, wherein each of the plurality of black reference detection units performs detection a plurality of times and calculates an average value of the detection values detected a plurality of times a predetermined number of times. Image reading device.

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