JP2002281243A - Image reading apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out operations of positional correction and skew correction automatically for an manuscript read image, and obtain an image with a small variation by making the correction process highly accurate. SOLUTION: In black reference detecting units 12a, 12b, and 12c, a plurality of black references out of a manuscript reading region are read through an optical scanning means used for reading the manuscript image. A means for compensating the output position and the skew of the read image on the basis of the read black references is provided in the image reading apparatus. The compensating means detects a plurality of times at the black reference detecting units 12a, 12b, and 12c, and a mean value of the detected values from the detecting units is used as the black reference detected value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, and more particularly, to an image reading apparatus having improved functions of original reading position correction and skew correction.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 08-214771 discloses a method in which black data and white data of one line width in the main scanning are obtained and averaged for a plurality of lines and used as black reference data and white reference data to perform shading correction. Performing an image correction process is disclosed.

Conventionally, in an image reading apparatus such as a copying machine or the like, even if a document is normally set, the image reading apparatus is composed of many parts. There is a problem that the original reading position shifts due to (e.g., inclination of the installation location) or the like.

[0004]

Conventionally, in the image reading apparatus, the correction of the position of the original image and the correction of the inclination (skew) are performed by reading a sample image at the time of factory production or installation in a market, and outputting the sample image and the output of the image reading apparatus. Correction processing was performed artificially by comparing and measuring an image.

[0005] However, such an artificial correction process requires an increased number of working steps and is difficult to achieve high accuracy.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to automate the work of correcting the position of an image read from a document and to correct the inclination (skew), to improve the accuracy of the correction processing, and to obtain an image with less variation. It is an object of the present invention to provide an image reading apparatus capable of performing the above.

[0007]

The present invention employs the following means in order to solve the above-mentioned problems.

The first means is provided with a plurality of black reference detecting portions, which are read by an optical scanning means for reading a document image, outside the document reading area, and based on the plurality of detected black reference values. In an image reading apparatus provided with means for correcting the output position and the inclination (skew) of a read image, the means performs detection a plurality of times in each of the plurality of black reference detection units, and detects the plurality of times. The average value of the detected values is used as the black reference detected value.

A second means is the first means, wherein the means determines whether or not the average value falls within a predetermined range of upper and lower limits. The value is used as the black reference detection value.

A third means is the first means, wherein the means takes an average value of an average value of the detection values detected a plurality of times and a detection value detected before power-on of the device.
It is characterized in that it is determined whether or not the average value falls within a predetermined range of upper and lower limits, and when it is determined that the average value falls within the range, the average value is used as the black reference detection value.

A fourth means is that, in the second means or the third means, when it is determined that each of the average values does not fall within the range of predetermined upper and lower limit values, the means has already been detected. Resetting the detected values, performing a plurality of detections in each of the plurality of black reference detection units, and performing a predetermined number of processes of calculating an average value of the plurality of detected detection values. .

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a perspective view showing a part of the structure of an image reading apparatus according to the present invention.

In FIG. 1, reference numeral 1 denotes a first mirror unit;
Reference numeral 2 denotes a second mirror unit, and reference numeral 9 denotes a pulse motor, which are provided below an original glass table 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).
Images are sequentially read while moving along the document at a speed of 2: 1.

FIG. 2 is a front view showing a part of the structure provided below the original glass table of the image reading apparatus according to the present invention, and FIG. 3 is a diagram showing the structure near the original glass table of the image reading apparatus according to the present invention. FIG.

In these figures, reference numeral 10 denotes an original reading area (shaded area), 11 denotes a CCD sensor reading area, and 12a, 1
Reference numerals 2b and 12c denote a black reference detecting unit, 13 denotes an original glass table, 1
4 is a vertical scale, 15 is a horizontal scale, and 16 is a white reference plate.

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 reflected light thereof is reflected by a first mirror and a second mirror (not shown). An image is formed by an image forming lens via a mirror and a third mirror, and the formed image is converted into an electric signal by a reading sensor such as a CCD, and then transmitted to a host computer (not shown).

A white reference plate 16 for performing image white level correction is provided on a bottom surface of a vertical scale 14 provided at an end of the original glass table 13.
Black reference detecting sections 12a and 12b are provided outside the document reading area 10 at both ends in the main scanning direction.
A black reference detection unit 12c is provided outside the document reading area 10 in the sub-scanning direction on the bottom surface.

The read image position correction value and the inclination (skew) correction value are obtained by operating the first mirror unit 1 to each of the black reference detection units 12a, 12b, and 12c during a homing operation or a shading operation when the apparatus is ON. Is measured by measuring the moving distance with the first mirror unit 1.

Here, the distance between one of the black reference detectors 12a and the end of the original reading area 10 in the sub-scanning direction is a, and the distance between the other black reference detector 12b and the end of the original reading area 10 in the sub-scanning direction is a. Assuming that the distance is b, 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, the read image position correction value (sub scanning direction) ) = (A + b) / 2 Read image position correction value (main scanning direction) = d Slope (skew) value = (a + b) / c.

The distances a, b, and c measured by the first mirror unit 1 are compared with predetermined upper and lower limits after the respective correction values are calculated by the above-described method, that is, the following relations are obtained. At some point, it is adopted as a reference value for the read image position correction value and the inclination (skew) value.

Scanned image position correction value (sub-scanning direction) α1 <(a + b) / 2> β1 Scanned image position correction value (main scanning direction) α2 <d> β1 Slope (skew) value α3 <(a + b) / c> β3 Each correction value measured and determined in this manner is adopted as a reference value at the time of image processing, and by performing a predetermined process, it is ensured from the first sheet of the original reading that the original image position with high accuracy is tilted. An image without (skew) can be obtained.

FIG. 4 is a flowchart showing a processing procedure of read image position correction (sub-scanning direction) according to the present invention.

In the figure, first, each black reference detecting section 12
a, 12b, the black reference position is detected a plurality of times, and the detected values a1, a2, a3,.
, B3,... Bm, and the average value ax = (a1 + a2 + a3 +.
m, average value bx = (b1 + b2 + b3 +... bm) /
m is obtained (step 1). The detected values a1, a2, a3,... Am and the detected values b1,
.., bm are detected at least four times at a time, and the maximum value and the minimum value are excluded from the detected values and adopted. 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, the average values a0 and b0 of the detection values corresponding to the previous times, for example, obtained before the power of the apparatus is turned on.
And the average value of the current and previous detection values ay = (a0 + ax) / 2 and by = (b0 + b)
x) / 2 is calculated (step 2). The average value (ay + b) calculated based on the average value calculated in Step 2
y) / 2 is within predetermined upper and lower limits, ie, α
It is determined whether or not 1 <(ay + by) / 2 <β1 (step 3). If the value does not exceed the predetermined upper and lower limit values, the calculated average value (ay + by) / 2 is adopted as a reference value to perform a read image position correction process (step 4), and then perform a read image output process. (Step 5). In step 3, if the value exceeds the predetermined upper and lower limit values, the average value (a0)
+ B0) / 2 is determined whether or not α1 <(a0 + b0) / 2 <β1 (step 6). 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 value as the reference value (step 7). If it is determined in step 6 that the value exceeds the predetermined upper / lower limit value, either of the upper / lower limit values α1 and β1 is adopted as a reference value to perform a read image position correction process (step 8).

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.

In FIG. 1, first, each black reference position 12
a, 12b, each black reference position is detected a plurality of times, and the detected values a1, a2, a3,.
.. bm, and the average value ax = (a1 + a2 + a3 +... am) of the respective detected values
/ M, average value bx = (b1 + b2 + b3 +... Bm)
/ M is obtained (step 11). Note that the detected values a1, a2, a3,... Am and the detected values b1, b
The maximum value and the minimum value among 2, b3,... Bm are excluded and adopted. Next, the average value a of the detection values calculated this time is
For x and bx, for example,
Using the average values a0 and b0 of the detection values obtained before the power supply of the apparatus is turned on, the average value of the current and previous detection values ay = (a0 + ax) / 2, by =
(B0 + bx) / 2 is calculated. (Step 12). Whether the average value (ay + by) / 2 calculated based on the average value calculated in step 12 is within the predetermined upper and lower limit values, that is, is in the range of α1 <(ay + by) / 2 <β1 It is determined whether or not it is (step 13). If the value does not exceed the predetermined upper and lower limit values, the calculated average value (ay +
(by) / 2 is adopted as a reference value, and a read image position correction process is performed (step 14), and then a read image output process is performed (step 15). If it is determined in step 13 that the value exceeds the predetermined upper and lower limit values, it is determined whether the processes from step 11 to step 13 have been performed a predetermined number of times (step 19). If the operation has been performed a predetermined number of times, turn on the power last time
The average value (a0 + b0) / 2 of the detection values detected at the time is α1
It is determined whether or not the range is <(a0 + b0) / 2 <β1 (step 16). If this does not exceed the predetermined upper and lower limits, the average value (a
(0 + b0) / 2 is adopted as a reference value to perform a read image position correction process (step 17). In step 19, if the detection has not been performed the predetermined number of times, the detection values a1, a2, a3,.
, Bm,... Bm are all reset and step 11
Is repeated (step 20). If it is determined in step 16 that the value exceeds the predetermined upper / lower limit value, one of the upper / lower limit values α1 and β1 is adopted as a reference value to perform a read image position correction process (step 18).

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 are performed in the same processing procedure. be able to.

As described above, according to the present invention, at least three black reference detecting sections are provided on the vertical scale and the horizontal scale which are the document setting references, and the distance from the black reference detecting section to the end of each scale is determined. By detecting multiple times with the CCD sensor and averaging it, an accurate detected value is obtained.In addition, it is considered that the detected value may become abnormal due to some cause of the CCD sensor. Then, by using the average value of the values detected by the previous CCD sensor and determining whether the average value falls within the range of predetermined upper and lower limits, the read image position correction and the inclination (skew) are performed. A highly accurate reference value for correction can be obtained.

Further, according to the present invention, if it is determined that the average value is not within the range of the predetermined upper and lower limit values as described above, the detection value detected last time when the power is turned on is changed to the predetermined upper and lower limit value. By adding a process of determining whether or not the value falls within the range, it is possible to obtain a highly accurate reference value for the read image position correction and the inclination (skew) correction.

Further, according to the present invention, when it is determined that the previously detected value does not fall within the range of the predetermined upper and lower limit values, the upper and lower limit values themselves are adopted as the correction value. Thus, the adoption of an abnormal detection value can be avoided.

Further, according to the present invention, when it is determined that the average value does not fall within the range of the predetermined upper and lower limit values as described above, all the detection values detected this time are reset and the black reference detection is performed again. A proper detection value can be obtained by adding a process of detecting the black reference position a plurality of times and a process of repeating the averaging process a predetermined number of times.

[0032]

According to the first aspect of the present invention, a plurality of black reference detecting sections which are read by an optical scanning means for reading a document image are provided outside the document reading area, and a plurality of black reference detecting sections are detected. By performing a correction process based on the black reference detection value obtained by averaging the values, an abnormality detection value (abnormality detection due to dust and dirt, electric noise, etc.) does not affect the reference value, Correct output position correction and inclination (skew) correction of the read image can be performed accurately.

According to the second aspect of the present invention, an output of an abnormal image is avoided by providing a means for determining whether or not the averaged black reference detection value is within predetermined upper and lower limits. can do.

According to the third aspect of the present invention, the average of the averaged black reference detected value and the previously detected and stored black reference detected value is within predetermined upper and lower limits. By providing a means for determining whether or not an abnormal image is output, the output of an abnormal image can be further avoided.

According to the fourth aspect of the present invention, when it is determined that each of the averaged black reference detection values does not fall within the predetermined upper and lower limit values, the currently detected and averaged black reference is calculated. The detection value is reset, and again, in each of the plurality of black reference detection units, detection is performed a plurality of times, and averaging processing of the detection values detected a plurality of times is performed. By making the determination, 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 below a document 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 a document glass table of the image reading apparatus according to the present invention.

FIG. 3 is a plan view showing a part of a structure near an original glass table 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.

5 is a flowchart showing a processing procedure from acquisition of a read image position correction value according to the present invention to image reading, which is different from the processing procedure shown in FIG. 4;

[Description of Signs] 1 First mirror unit 2 Second mirror unit 9 Pulse motor 10 Document reading area (shaded area) 11 CCD sensor reading area 12 Black reference detection unit 13 Document glass table 14 Vertical scale 15 Horizontal scale 16 White reference plate

Claims (4)

[Claims] A plurality of black reference detection units which are read by an optical scanning unit for reading a document image outside a document reading area, and wherein a plurality of black reference detection values are read based on the plurality of read black reference detection values. An image reading apparatus comprising means for performing an output position correction and a tilt (skew) correction, wherein the means performs detection a plurality of times in each of the plurality of black reference detection units, and calculates a detection value of the plurality of detections. An image reading apparatus, wherein an average value is used as the black reference detection value. 2. The method according to claim 1, wherein the determining unit determines whether the average value is within a predetermined range of upper and lower limits. If the average value is determined to be within the range, the average value is used as the black reference detection value. The image reading device according to claim 1, wherein: 3. The means for calculating an average value of an average value of the detection values detected a plurality of times and a detection value detected before the power of the apparatus is turned on, wherein the average value is a predetermined upper and lower limit value. 2. The image reading apparatus according to claim 1, wherein it is determined whether the image is within the range, and when it is determined that the image is within the range, the average value is used as the black reference detection value. 4. When the average value is determined not to be within the range of predetermined upper and lower limit values, the means resets a detection value that has already been detected, and resets each of the plurality of black values. The image reading apparatus according to claim 2, wherein the reference detection unit performs detection a plurality of times, and performs a process of calculating an average value of the detection values detected a plurality of times a predetermined number of times.