JP2002267412A - Measuring instrument of color image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring instrument of a color image reader which can speedily measure a chromatic aberration with high precision. SOLUTION: A chromatic aberration measuring instrument 2 is equipped with an image signal input part 25 which obtains the image signal outputted by a color image reader 1 to be measured, an image storage memory 27 which stores the image signal obtained by the input part 25, and an image processing arithmetic part 26 which obtains the image signal from the memory 27 and computes position shift quantities among respective colors; and a document which has uniform density in the scanning direction of an optical system and uneven density at right angle to the direction is set on the color image reader 1 and the image processing arithmetic part 26 computes the relative positions of image data of a specific area of an image signal of one color of the image signal obtained by the input part 25 and image data of an area shifting by image pickup element pitch from the specific area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device capable of measuring chromatic aberration of an image read by a color image reading device with high accuracy.

[0002]

2. Description of the Related Art Conventionally, as an example of this type of measuring device, there is an image reading device disclosed in JP-A-11-8734. According to this conventional technique, a window is set in the read image data, and when it is determined that a 45 ° oblique line pattern is formed at a constant pitch in the sub-scanning direction (document conveying direction) on a white background, the window is set to the oblique line angle. , And the positions of the pixels in the main scanning direction are measured based on the change in the position of the oblique lines in each window.
Chromatic aberration between RGB images is measured by sequentially performing the measurement on each of the three primary colors (green and blue). Note that chromatic aberration is one of optical characteristics, and when a color scanner is described as an example, in image reading through a lens, an RGB image reads a point image at a different position on an image sensor. Basically, it is a physical phenomenon caused by a difference in the refractive index of a lens with respect to the wavelength of light.

[0003]

However, in the above-mentioned prior art, there is a problem that the oblique pattern is affected by chromatic aberration in the sub-scanning direction. However, there is a problem that it is difficult to separate the relative position shift and the chromatic aberration generated between RGB from the deflection of the folding mirror, the vibration of the image sensor, and the line-sequential image reading speed fluctuation. In an image reading apparatus (full-color scanner) that reads a line-sequential image using a three-line CCD (imaging element), when the speed of the carriage fluctuates or the vibration of an optical system such as a mirror occurs, the reading positions of RGB become different. Therefore, the relative positional relationship at the same position of each of the RGB images does not become the chromatic aberration amount as it is. Therefore, simply reading the image into the buffer and aligning the RGB positions results in a measurement including a reading position shift component, resulting in measurement accuracy. However, there is a problem in that the metal is deteriorated. Also, the image reading by the full-color scanner to be measured is not always constant due to the MTF fluctuation of the optical system, etc.
There was also a problem that stable measurement was difficult. An object of the present invention is to solve such a problem of the related art. Specifically, in measuring chromatic aberration in the main scanning direction,
By using a document having a density that is not uniform in the main scanning direction and uniform in the sub-scanning direction, chromatic aberration in the main scanning direction and chromatic aberration in the other direction are completely separated, and a reading position shift component of the image reading apparatus is reduced. It is an object of the present invention to provide a measuring apparatus capable of quickly and accurately measuring chromatic aberration by eliminating the influence.

[0004]

According to a first aspect of the present invention, there is provided an optical system for imaging a subject one-dimensionally, and an image sensor, wherein the image sensor includes a predetermined image sensor. A two-dimensional image of the subject by scanning the optical system in one direction and causing the image of the subject to be incident on the image sensor, comprising an image sensor corresponding to each of the three primary colors arranged at an element pitch; Color image input means for inputting the image data for each image sensor, and adjusting the positional shift by the image sensor pitch; signal processing means for generating an image signal from a signal output from the color image input means; The image signal output by the signal output means of the color image reading apparatus is provided to the color image reading apparatus to be measured, the signal output means comprising: An image signal input means for obtaining,
A color image reading apparatus comprising: an image storage unit that stores an image signal obtained by the image signal input unit; and an image signal calculation unit that obtains an image signal from the image storage unit and calculates a positional shift amount between each color. In the measuring device of the device,
An original having a density that is uniform in the scanning direction of the optical system and that is not uniform in a direction perpendicular to the direction is set in the color image reading apparatus, and the image signal obtained by the image signal input unit is The image signal calculation means,
The relative positions of the image data of the designated area in the one color image signal and the image data of the area shifted from the designated area by the image sensor pitch in the other one color image signal among the image signals are targeted. Was calculated.

[0005] According to the second aspect of the present invention, the first aspect is provided.
A measuring method of the color image reading apparatus for obtaining an image signal output by the signal output unit of the color image reading apparatus described above, and calculating a positional shift amount between each color with respect to the obtained image signal; The image signal output by the signal output means when a document having a density that is uniform in the direction in which the color image is read and that is not uniform in a direction perpendicular to the direction is acquired in the color image reading device, and the acquired image signal is The relative position between the image data of the designated area in the image signal of one color and the image data at a position shifted by the image sensor pitch from the designated area in the image signal of the other one color is calculated. I made it. According to a third aspect of the present invention, in the configuration of the second aspect, the respective volume centroid positions of the two-color image data are obtained, and a difference between the obtained two volume centroid positions is calculated as the relative position. did. According to a fourth aspect of the present invention, in the second aspect, the relative position is calculated by pattern matching using one image data as a reference image. According to a fifth aspect of the present invention, in the second, third, or fourth aspect, a smoothing process is performed on the acquired image data before calculating the relative position. did. According to a sixth aspect of the present invention, in the second, third, or fourth aspect, the width of the parallel line pattern of the document in the direction in which the relative position is calculated is the resolution width of the image sensor. The configuration is larger. According to a seventh aspect of the present invention, in the second, third, or fourth aspect of the present invention, the gray portion of the original pattern is formed of gray having the same sensitivity as all of the image sensors. It was configured. Further, in the invention according to claim 8, the program programmed according to the measurement method according to claim 2, 3, or 4 is stored in the storage medium storing the program.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view of a main part of a color image reading apparatus to be measured according to the present invention. The color image reading apparatus is, for example, a scanner unit of a full-color copying machine. As shown in the figure, a first traveling body 3 that scans a lamp illuminating a document, and a second traveling body that moves a folding mirror.
A traveling body 4, a line CCD unit 5 serving as a one-dimensional image sensor corresponding to three colors of RGB and forming a line in a direction perpendicular to the traveling direction of the first traveling body 3,
A lens 6 and the like for forming an image on the D unit 5 are provided, and the first traveling body 3 scans the document setting place in one direction, so that the image on the document placed at the document setting place is line-sequentially ( The image is read as a two-dimensional image by taking in (in order of one line) and the image signal is output from the image output port 9. The first traveling body 3 and the second traveling body 4
Is driven by the motor 7 through the drive transmission means 8.
FIG. 2 shows the structure of the main part of the color image reading apparatus. As shown, a reference chart document 10 is placed on a contact glass 11 and a lamp as a light source for illuminating the document 10 is provided.
12 irradiates the imaging area 13 with light, and the second traveling body 4 that moves the folding mirror 14 and the first traveling body 3 that follows the scanning mirror scan from the beginning to the end of the document 10, so that the folding mirror 14 and the lens The reflected light of the entire document sequentially reaches the line CCD unit 5 via the CCD 6, where the reflected light is photoelectrically converted and taken in as an image signal. Note that FIG.
In the figure, reference numeral 15 denotes a reflector. FIG. 3 is an overall configuration diagram relating to the measuring device of the present invention. As shown,
A color image reading device 1 to be measured for acquiring chart document image data, and a chromatic aberration measuring device 2 connected thereto
The chromatic aberration measuring device 2 includes an image signal input unit
21, a measuring device main body including an image signal storage unit for storing the image signal and an image signal calculation unit for calculating the amount of chromatic aberration and the like
22, an image display device 23 for displaying the result calculated by the image signal calculation section. The measurement device main body 22 can be used as various calculation, communication, and storage means by using a computer including a keyboard, a mouse, and the like. The image display device 23 is, for example, a CRT.

FIG. 4 shows a system configuration of this embodiment. In this embodiment, the image signal input means, the image storage means, and the image signal calculation means are respectively provided in the order of the image signal input section 25, the image storage memory 2,
7 and the image processing operation unit 26. With such a configuration, in the color image reading apparatus 1, reflected light from a document is line-sequentially captured by the three-line CCD unit 5 via an optical system such as the return mirror 14 and the lens 6, and the captured document reflected light is It is converted into an electric signal by the 3-line CCD unit 5. Then, under the control of the control unit 16, the A / D conversion unit 17 converts the electric signal from analog to digital data, the shading correction unit 18 performs shading correction on the data, and the image signal output unit 19 The corrected image signal is output from port 9. Under the control of the control unit 16, a full-color image of all images is output in a line-sequential manner. Subsequently, the image signal is input by the image signal input control unit 25 of the chromatic aberration measurement device 2, and under the control of the control unit 24, all the image data is stored in the image storage memory 27.
Is stored in Further, the control unit 24 sequentially takes out the two-color pixel data at positions shifted relatively by the value set in the sub-scanning direction, and the image processing calculation unit 26 calculates the relative position of the two-color pixel data. The calculated relative position is the chromatic aberration amount, and the image display unit 28 displays the calculated measurement result on the image display device 23. FIG. 5 shows an example of a document pattern used in the first embodiment of the present invention and an example of an image signal output by the color image reading apparatus 1. As illustrated, the chart document is a line pattern in which white and gray patterns of each density are arranged at equal intervals in a direction perpendicular to the main scanning direction.

Next, referring to FIG. 6 and FIG. 7, the operation of the first embodiment of the present invention will be described in the case of using R (red) and G (green) images. First, the R image data of the designated area (see FIG. 7) is read from the image storage memory 27 (S1), and the volume center of gravity Pr of the image (see FIG. 7, the position of each image data included in the designated area in each main scanning direction) Average of the values that indicate
Is calculated (S2). Further, G at a position (see FIG. 7) shifted from the R image data by a value designated in the sub-scanning direction.
The image data is read out (S3), and the volume center of gravity Pg of the image is calculated (S4). Further, a difference Pr-Pg of the volume center of gravity is determined (S5). Since the measurement target is chromatic aberration in the main scanning direction,
The difference between the positions obtained by calculating the center of gravity only in the main scanning direction from each image data (pixel data) is the chromatic aberration amount. Since the values in the sub-scanning direction are all the same if the positions in the main scanning direction are the same, it is not necessary to calculate in consideration of the influence of the shift in the sub-scanning direction. Thus, according to this embodiment, the amount of chromatic aberration can be quickly measured. Further, since the chromatic aberration is obtained in the same environment and at the same time as in the actual operation, an output image without color shift can be obtained by performing correction using the chromatic aberration amount measured at this time.

Next, the operation of the second embodiment of the present invention will be described with reference to FIGS. 8 and 9 in the case of using R (red) and G (green) images. First, the R image data of the designated area (see FIG. 9) is read out from the image storage memory 27 (S11), and further, the R image data is shifted from the R image data by a designated value in the sub-scanning direction. The G image data of the same size in the sub-scanning direction with respect to the data and of a size smaller by a predetermined amount in the main scanning direction (to be at the center with respect to the R image data) is read (S12). This G image data is registered (stored) as a reference image for pattern matching (S13),
The position in the main scanning direction that best matches the reference image is calculated from the R image data, and the left end position of the reference image in the matching state with reference to the left end of the R image data designated area is set to Prg (see FIG. 9) (S14). ). Then, the value Prg and the value Pc of the relative read position of the G image data with respect to the R image data (FIG. 9)
In the example of (1), the amount of chromatic aberration that is the difference from b−a) is obtained (S1).
Five). Thus, in this embodiment, the chromatic aberration amount can be obtained without performing the volume center of gravity calculation.

Next, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, as shown in FIG. 10, patterns of density of white and gray (having RGB components) are arranged at equal pitches in the main scanning direction, and the interval between the patterns is determined by the color image reading apparatus. A document having a line pattern larger than the resolution (resolution width) of the image sensor is used.
As a result, in this embodiment, moire is eliminated and a high S
Since an RGB image having N can be acquired, chromatic aberration measurement accuracy can be improved. Further, in the fourth embodiment of the present invention, the gray portion of the original pattern is formed of gray having the same sensitivity for all of the RGB image sensors. As a result, in this embodiment, there is no color component having a small value of the image signal data, and therefore, the SN is increased and the correction accuracy is improved. Further, in the fifth embodiment of the present invention, a smoothing process is performed on the image data sequence acquired from the image reading device to be measured before the calculation for obtaining the chromatic aberration. As an example, a case where R image data and G image data are used will be described. First, R image data and G image data are read, and smoothing processing is performed on these image data. A low-pass filter or the like is used as a smoothing processing method. In order to reduce the change in the data value between adjacent pixels, simply, for example, the data is corrected so that the change amount is equal to or less than a predetermined amount. Then, after performing the smoothing process, the calculation for obtaining the chromatic aberration is executed as described above. Thus, according to this embodiment, since the obtained image data sequence is subjected to the smoothing process, high-precision measurement is realized without being affected by the signal SN error caused by the MTF difference between RGB. can do. Although the case where the measuring device is the chromatic aberration measuring device 2 shown in FIGS. 3 and 4 has been described above, the program programmed according to the measuring method described above is stored in, for example, a removable storage medium, and the storage medium Is attached to an information processing apparatus such as a personal computer which has not been able to perform the chromatic aberration measurement according to the present invention, so that the information processing apparatus can also perform the chromatic aberration measurement according to the present invention.

[0011]

As described above, according to the present invention,
According to the first and second aspects of the present invention, when the image signal output from the color image reading device is acquired and the amount of displacement between the colors of the image signal is calculated, the image signal is uniformly scanned in the scanning direction of the optical system. Further, an image signal output when an original having non-uniform density in a direction perpendicular to the direction is set in the color image reading device is obtained, and image data of a designated area in one color image signal among the image signals is obtained. And the relative position between the image data at the position shifted by the image sensor pitch from the designated area in the other one color image signal, the chromatic aberration in the main scanning direction and the chromatic aberration in the other direction are calculated. Can be completely separated, so that the chromatic aberration can be measured quickly and with high accuracy. According to a third aspect of the invention, in the second aspect of the invention, the respective volume centroid positions of the two-color image data are obtained, and a difference between the obtained two volume centroid positions is calculated as the relative position. Therefore, chromatic aberration can be measured more quickly. Further, in the invention according to claim 4, in the invention according to claim 2, the relative position is calculated by pattern matching using one of the image data as a reference image. The chromatic aberration in the main scanning direction can be measured with high accuracy without being affected by image distortion.

According to a fifth aspect of the present invention, in the second, third or fourth aspect of the present invention, the smoothing process is performed on the acquired image data before calculating the relative position. Since the measurement is performed, the measurement can be performed with high accuracy without being affected by the signal SN error caused by the difference in the MTF between RGB. According to a sixth aspect of the present invention, in the second, third, or fourth aspect, the width of the parallel line pattern of the document in the direction in which the relative position is calculated is the resolution width of the image sensor. Since it is larger, moiré can be eliminated, and an RGB image having a high SN can be obtained, and therefore, chromatic aberration measurement accuracy can be improved. Further, according to the invention described in claim 7, according to claim 2,
According to the third or fourth aspect of the present invention, since the gray portion of the original pattern is formed of gray having the same sensitivity as that of each of the image sensors, there is no color component having a small value of the image signal data. The SN is increased, and the measurement accuracy is improved. In the invention according to claim 8, the program programmed in accordance with the measurement method according to claim 2, 3, or 4 is stored in, for example, a removable storage medium. The information processing apparatus according to claim 2, 3, or 4, which is mounted on an information processing apparatus such as a personal computer that cannot perform the chromatic aberration measurement according to the invention described in claim 2, 3, or 4, also performs the chromatic aberration measurement. The effect of the invention described in Item 4 can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of a color image reading apparatus to be measured according to the present invention.

FIG. 2 is an explanatory diagram showing a main part of a color image reading apparatus to be measured according to the present invention.

FIG. 3 is an overall configuration diagram relating to a measurement device of the present invention.

FIG. 4 is a system configuration diagram showing a measurement system of each embodiment of the present invention.

FIG. 5 is an explanatory diagram of a document pattern used in the first embodiment of the present invention and an image signal output from the color image reading device.

FIG. 6 is an operation flowchart of the measuring apparatus according to the first embodiment of the present invention.

FIG. 7 is an explanatory diagram of a main part of a measuring apparatus according to the first embodiment of the present invention.

FIG. 8 is an operation flowchart of a measuring apparatus according to a second embodiment of the present invention.

FIG. 9 is an explanatory diagram of a main part of a measuring device showing a second embodiment of the present invention.

FIG. 10 is an explanatory diagram of a main part of a measuring device showing a third embodiment of the present invention.

[Explanation of symbols]

1 color image reading device, 2 chromatic aberration measuring device, 21 image signal input section, 22 measuring device main body, 23 image display device,
24 control unit, 25 image signal input control unit, 26 image processing operation unit, 27 image storage memory

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yunami F-term in Ricoh Co., Ltd. 1-3-6 Nakamagome, Ota-ku, Tokyo 2F065 AA14 AA56 BB02 DD04 FF04 JJ03 JJ26 LL12 LL62 MM24 QQ03 QQ17 QQ24 QQ33 QQ38 SS13

Claims (8)

[Claims] 1. An image pickup device comprising: an optical system for one-dimensionally capturing an image of a subject; and an image sensor, wherein the image sensor includes image sensors corresponding to each of three primary colors arranged at a predetermined image sensor pitch. A two-dimensional image of the object is input to each image sensor by scanning the optical system in one direction to cause the image of the object to enter the image sensor, and a color shift that adjusts the position shift by the image sensor pitch is provided. A color image to be measured, comprising: an image input unit; a signal processing unit configured to generate an image signal from a signal output from the color image input unit; and a signal output unit configured to output an image signal of the signal processing unit to the outside. For the reading device, an image signal input unit that obtains an image signal output by the signal output unit of the color image reading device, and an image signal that is obtained by the image signal input unit A measuring device for a color image reading apparatus, comprising: an image storage unit configured to store an image signal; and an image signal calculation unit configured to acquire an image signal from the image storage unit and calculate a positional shift amount between respective colors. A document having a density that is uniform in the scanning direction and not uniform in a direction perpendicular to the scanning direction is set in the color image reading apparatus, and the image signal obtained by the image signal input unit is set to the image signal. The arithmetic means targets image data of a designated area in one color image signal of the image signal and image data of an area shifted from the designated area in the other one color image signal by the imaging element pitch. A measuring device for a color image reading device, wherein a relative position between the two is calculated. 2. The color image reading apparatus according to claim 1, wherein the color image reading apparatus acquires an image signal output by the signal output unit, and calculates a displacement amount between the colors of the acquired image signal. Acquiring an image signal output by the signal output means when an original having a density uniform in a scanning direction of the optical system and not uniform in a direction perpendicular to the scanning direction is set in the color image reading apparatus. Then, with respect to image data of a designated area in one color image signal of the acquired image signals and image data at a position shifted by the image sensor pitch from the designated area in another one color image signal, A method for measuring a color image reading device, comprising calculating a relative position between the two. 3. The measurement method for a color image reading device according to claim 2, wherein the respective volume centroid positions of the image data of two colors are obtained, and a difference between the obtained two volume centroid positions is calculated as the relative position. A method for measuring a color image reading apparatus, comprising: 4. The method according to claim 2, wherein the relative position is calculated by pattern matching using one of the image data as a reference image. 5. A method for measuring a color image reading device according to claim 2, wherein a smoothing process is performed on the acquired image data before calculating the relative position. A method for measuring a color image reading apparatus, comprising: 6. The measuring method for a color image reading apparatus according to claim 2, wherein the width of the parallel line pattern of the document is determined by the resolution of the image sensor in the direction in which the relative position is calculated. A measuring method for a color image reading device, wherein the measuring method is configured to be larger than a width. 7. The measuring method for a color image reading device according to claim 2, wherein the gray portion of the original pattern is formed of gray having sensitivity equal to all of the image pickup devices. A measuring method for a color image reading apparatus. 8. A storage medium storing a program, the storage medium storing a program programmed according to the measurement method according to claim 2, 3 or 4.