JPH1042097A - Color linear image sensor and image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a uniform an excellent color separation characteristic by preventing color mixture due to an oblique incident light over the lengthwise direction of a color linear image sensor adopting the point sequential system. SOLUTION: This image sensor is provided with a plurality of photo sensing pixels 13 arranged on a line, receiving an image light and storing electric charges, a shield layer 12 arranged above a plurality of the photo sensing pixels so as to shield between the photosensing pixels, and color filters 11 in a plurality of colors arranged above the shield layer corresponding to a plurality of the pixels so as to selectively pass a specific color light of the image light. Then the filters 11 are shifted toward the center of the pixel array arranged on a line from the position of the corresponding pixels, or the shield layer 12 is shifted toward the center of the picture element array arranged on a line proportional to a distance from the center. Furthermore, the sensor is combined with a telecentric image forming optical system so as to make the major ray in parallel with the optical axis in an image space thereby preventing color mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color linear image sensor for arranging sensor pixel rows in a predetermined repetition order by a plurality of sensor pixels of a plurality of colors and extracting a document reading signal separated into each color, and image processing using the sensor. Related to the device.

[0002]

2. Description of the Related Art FIG. 14 is a diagram showing a configuration example of a conventional dot-sequential one-line color linear image sensor, FIG. 15 is a diagram showing another configuration example of a conventional dot-sequential one-line color linear image sensor, and FIG. FIG. 17 is a diagram for explaining the operation of the chip internal configuration diagram shown in FIG. 16, FIG. 17 is a diagram for explaining the operation of the chip internal configuration diagram shown in FIG. 16, and FIG. 18 is a video signal of the 3-line color linear image sensor. FIG. 3 is a diagram illustrating a configuration example of a processing circuit.

[0003] CCD linear sensors are used in image reading apparatuses such as copiers, facsimile machines, and scanners of OA equipment that read original images. When reading a color original image using this CCD linear sensor, R
A color linear image sensor in which color filters having spectral sensitivities of (red), G (green), and B (blue) are on-chip on a CCD linear sensor is used.

Conventionally, a color image is read by a one-line color linear image sensor of a point-sequential system by combining a close-contact sensor and a rod lens array. In this case, the S / N ratio is good because the photosensitive pixels of the sensor are large.
When reading spi, a long sensor of 30 cm length is required because it is an equal magnification system, so it is difficult to realize it with one chip, and it has to be a multi-chip configuration, for example, a configuration using five chips of 60 mm length. . For this reason, the sensor itself and the drive / signal processing circuit are expensive, and there are drawbacks such that not only the color difference between chips occurs but also the depth of focus cannot be obtained because of the combination with the rod lens array.

Therefore, the chip size is small, and
Due to the chip configuration, there has been adopted a method in which an inexpensive reduced type three-line type line sequential sensor having no difference between chips and a spherical lens is combined. However, in the case of this method, as shown in FIG. 18, gap correction is required in the sub-scanning direction, and the accuracy of gap correction cannot be maintained due to the influence of vibration generated from the scan motor and the like. ing. To solve such a problem of the correction in the sub-scanning direction, a one-line type dot sequential color linear image sensor has been proposed.

In the case of the former three-line color sensor, there is a line gap between RGB, so that line correction is necessary. In the case of the latter point-sequential one-line color sensor, however, the gap between lines is required. In that respect, the former is more advantageous than the former three-line color sensor, but a color shift occurs in the main scanning direction between RGB. Therefore, in order to correct this color shift, a moving average process may be performed.
There is a secondary obstacle that the MTF is deteriorated by the arithmetic processing.

As described above, as a conventional color linear image sensor, a three-line color linear image sensor in which sensor pixel rows using color filters having R, G, and B spectral sensitivities are arranged in parallel in the sub-scanning direction is known. ., RGBRGB... Shown in FIG. 14, a sensor pixel array 91 is formed of a three-color sequential repetitive array, and a read signal is serially extracted in the same order via a CCD register 93 in a dot-sequential one-line color linear image. A sensor pixel row 91 is formed of a three-color sequential repetitive array like a sensor, RGBRGB shown in FIG.
There is a dot-sequential one-line color linear image sensor in which a read signal is transferred from the sensor pixel array 91 to the CCD registers 93R, 93G, and 93B for each color, and each is taken out by serial transfer.

The dot sequential one-line color linear image sensor shown in FIG. 14 has a pulse .phi.ROG as shown in FIG.
The readout gate 92 is controlled by the driver 95 based on the
And transfer them in batches in parallel to clocks φ1 and φ
2. Serially read out at V _OUT through output amplifier 94 by reset pulse φRS. The dot-sequential one-line color linear image sensor shown in FIG. 15 has, for example, a specific chip internal configuration (for example, “High-speed driving point-sequential color CCD linear sensor”, Vol. 47, No. 9, pp. ~ 1167
16), and FIG. 17 shows an operation pulse waveform diagram thereof. As shown in FIG.
The readout gate 92 is controlled by the driver 95 based on OG (R), (G), and (B), and the sensor pixel row 91 is controlled.
Signals from the CCD registers 93R, 93G, 93, respectively.
B, and holds the clocks φ1, φ2, φ3, φ4
, A CCD register 93R, 93G, 93B via a timing generator 99 and a clock driver 96.
And V _OUT (R, G, B) through the output amplifier 94
Is being read.

On the other hand, in a three-line color linear image sensor, for example, as shown in FIG. 18, a video signal obtained by separating reflected light from a color original into R, G, and B and converting it into an electric signal is converted into an odd-numbered pixel ( Odd) and the even-numbered pixel (E
ven). The video signal processing circuit includes a sample hold circuit 202 and a gain adjustment circuit AG.
C (AUTOMATIC GAIN CONTROL) 203, offset adjustment circuit AOC (AUTOMATIC OFFSET CONTROL) 204, A /
A three-line color linear image sensor 2 including a D conversion circuit 205, a multiplexer 206, gap correction memories 207 and 207 ', and a shading correction circuit 208;
After sampling and holding the analog video signal output from 01, converting the digital signal by adjusting the gain and offset, and mixing the even-numbered pixels and the odd-numbered pixels, gap correction and shading correction are performed. . The gap correction memories 207 and 207 'are for correcting the gap between the sensors in the pixel rows R, G, and B, and include, for example, a line memory having a FIFO configuration.

[0010]

FIG. 19 is a view showing an outline of an optical system of a reduction type document reading apparatus, and FIG. 20 is a view for explaining a problem of color mixing. However, in the above-described reduced type document reading apparatus, the spherical lens 252 is used between the document 251 and the sensor 241 as shown in FIG. As the light reflected from the sensor approaches both ends of the sensor, the light enters the filter / pixel of the sensor obliquely.

In the dot sequential sensor, the conventional 3
It is necessary to realize the width of each pixel narrower than that of the line type sensor.
m, the number of pixels per color is A3, and 5000 pixels for 400 spi reading, the pixel size (width)
In the three-line ^{sensor, 70 × 10 3/5000 =} 14μ
The m dot sequential ^{sensor, 70 × 10 3/5000 ×} 3 =
4.66 μm.

In the color sensor, as shown in FIG. 20, a CC which is a base which is shielded by a shielding layer (aluminum layer) 302 is used.
The color filter 303 is provided on the pixel 301 of the D sensor. However, if the width of the pixel is reduced as described above, the height and thickness of the filter cannot be ignored. Therefore, color mixing does not occur when the angle of the incident light is perpendicular to the sensor as shown in FIG. 20A. However, as shown in FIG. If there is a component that enters the light, a part of the light that has passed through a certain color, for example, a G filter, is not a pixel facing the filter, but an adjacent pixel,
For example, light is originally incident on the R light receiving pixel as indicated by a dashed line, and as a result, a "color mixture" phenomenon is caused. Have a problem.

[0013]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and even in a color linear image sensor of a dot-sequential system, color mixing due to oblique incident light over the longitudinal direction of the sensor is prevented and uniform. To achieve good color separation characteristics.

For this purpose, the present invention provides, as a color linear image sensor, a plurality of photosensitive pixels which are arranged in a straight line, receive image light and accumulate electric charges, and a photosensitive pixel and a photosensitive pixel above the plurality of photosensitive pixels. A plurality of color filters arranged to selectively pass specific color light of image light with the shielding layer interposed therebetween corresponding to the plurality of photosensitive pixels, and a shielding layer disposed so as to shield between the plurality of photosensitive pixels. Wherein the position of the color filter is shifted closer to the center of the pixel array arranged on the straight line than the position of the corresponding pixel.

[0015] The shift amount is set in proportion to the distance from the center position, and the larger the color filters located above the color filters having different heights, the larger the shift amount is. The color filters of a plurality of colors are arranged in a predetermined repetition order in a plurality of colors, the arrangement order of the colors is set so as to be line-symmetric from the center position, and the color filters of the plurality of colors having different heights are arranged. In contrast, the color arranged closer to the center is higher than the color arranged closer to the outside.

An image forming optical system for forming an image light of an original on a point-sequential color linear image sensor comprising the photosensitive pixels, the shielding layer and the color filter is provided, and the optical axis of the image forming optical system is set at the center of the sensor. And the imaging optical system is characterized in that the maximum value of the angle of the principal ray incident on the sensor is not less than 10 ° and not more than 20 °, and further shifting the color filter. Instead of this configuration, the position of the shielding layer is shifted toward the center of the pixel array arranged on the straight line.

The image reading apparatus further includes the color linear image sensor, and an image forming optical system for forming an image light of a document on the color linear image sensor. The optical axis is configured to coincide with the center position of the sensor, and the imaging optical system includes:
The maximum value of the angle of the principal ray incident on the sensor is not less than 10 ° and not more than 20 °, and the shift amount is set according to the incident angle of the image light projected by the imaging optical system. It is characterized by the following.

Further, as an image reading device, a plurality of photosensitive pixels which are arranged in a straight line, receive image light, and accumulate electric charges, and shield between the photosensitive pixels above the plurality of photosensitive pixels. A plurality of color filters arranged so as to selectively pass specific color light of image light with the shielding layer interposed therebetween corresponding to the plurality of photosensitive pixels, and the photosensitive pixels And a telecentric imaging optical system for projecting an image on a point-sequential color linear image sensor comprising a shielding layer and a color filter.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing an embodiment of an image reading apparatus according to the present invention, FIG. 2 is a view showing another embodiment of the image reading apparatus according to the present invention, and 1 is a dot-sequential color linear image sensor. 2 is a telecentric lens, 3 is an aperture stop, 4 is a platen glass, 5 is a manuscript,
11 denotes a color filter, 12 denotes a shielding layer, and 13 denotes a photosensitive pixel.

In FIG. 1, a dot-sequential color linear image sensor 1 has R (red), G
This sensor is composed of sensor pixel rows on-chip so as to repeat color filters having spectral sensitivities of (green) and B (blue) in a predetermined arrangement order, and is a sensor for taking out a read signal of a color-separated color original. BGRB to the right
GR or RGBRGB ... repetition of the photosensitive pixel rows. The repetition order of the photosensitive pixel rows is reversed from the center position, that is, the color arrangement order is right and left in RGB from the center position of the photosensitive pixel rows. The photosensitive pixel rows are arranged so as to be line-symmetric. The telecentric lens 2 is an optical system in which the position of the exit pupil is set to infinity. By placing the aperture stop 3 at the front focal point, the principal ray that has passed through the telecentric lens 2 in this optical system is converted into an image space ( On the sensor side), it is parallel to the optical axis. Therefore, even if the point-sequential color linear image sensor 1 has an angle-of-view dependency in the color separation characteristics as described with reference to FIG. 10, the image reading apparatus can use the telecentric imaging optical system using the telecentric lens 2. By combining them, uniform and good color separation characteristics can be obtained over the longitudinal direction of the sensor.

In the above telecentric imaging optical system,
The cost of the telecentric lens 2 is higher than that of a lens conventionally used. Therefore, the embodiment shown in FIG. 2 is configured to improve the angle-of-view dependency of the color separation characteristics by the dot-sequential color linear image sensor itself, and as shown in FIG.
1 is shifted toward the center in the longitudinal direction of the sensor from the position of the corresponding pixel unit 13. Now
As shown in FIG. 2A, the distance from the rear principal point of the lens to the point-sequential color linear image sensor 1 is L, the distance from the optical axis to the pixel of interest is r, and the half angle of view is θ. Assuming that the distance between the color filter 11 of the dot-sequential color linear image sensor 1 and the pixel (photoelectric conversion unit) 13 is d, Δr shown in FIG. The shift amount Δr can be obtained from the relationship between two well-known similar triangles. That is,
A right-angled triangle having distances L and r as two sides sandwiching a right angle in FIG. 2A and a right-angled triangle having distance d and shift amount Δr as two sides sandwiching a right angle in FIG. 2B have the same half angle of view θ as a vertex angle. Since these have similar triangles, the ratio between the shift amount Δr, which is the corresponding side thereof, and the distance r from the optical axis (the center of the sensor) is the same as the ratio between the distance d and the distance L.

[0022]

(Equation 1) , The shift amount Δr is obtained. That is, it is proportional to the distance r from the optical axis.

Further, another embodiment in which the position of the color filter 11 is shifted toward the center in the longitudinal direction of the sensor from the position of the corresponding pixel portion 13 will be described.
FIG. 3 is a diagram showing an embodiment of a dot-sequential color linear image sensor in which the arrangement order of the color filters is the same over the entire length. The color filters are arranged in the order of RGBRGB from the right end to the left end. It is shifted in proportion to the distance from the center toward the center in the longitudinal direction from the center of the corresponding pixel. FIG. 4 is a diagram showing an embodiment of a dot-sequential color linear image sensor in which the arrangement order of the color filters is line-symmetrical from the center position to the left and right.
BGR..., Color filters are similarly arranged in order of BGRBGR... Toward the left end, and the position of the color filter is shifted from the position of the corresponding pixel toward the center in the longitudinal direction from the center in proportion to the distance. It is.

In the case of a conventional point-sequential color linear image sensor, there is no problem on the optical axis as shown in FIG. 3B, but the incident light has an angle on both left and right sides of the sensor as shown in FIGS. 3A and 3C. For example, on the left side of the sensor, as shown in FIG. 3A, the transmitted light component (dashed line) of the G color filter adjacent to the R pixel portion is mixed, and similarly, the B color adjacent to the G pixel portion is mixed. The transmitted light component (dashed-dotted line) of the filter and the transmitted light component (dashed-dotted line) of the R color filter adjacent to the B pixel portion are mixed. On the right side, as shown in FIG. 3C, the transmitted light components (dashed lines) of the color filters are mixed in a combination opposite to that on the left side. Therefore, this tendency of color mixing is
Since the left and right sides of the optical axis are different, the color change is asymmetrical to the optical axis. Therefore, the color filter is shifted toward the center by the amount of shift determined in accordance with the distance from the center of the sensor, that is, by the amount of influence of the incident light angle, with respect to the left and right sides of the sensor. In this way, as shown in FIGS. 3D and 3F, it is possible to prevent color mixing due to transmitted light components of the color filters of adjacent pixels. In this case, the image data may be divided into several blocks and a predetermined shift amount may be set for each block.

When the arrangement order of the color filters is the same over the entire length as described above, if the shift amounts are not sufficiently matched at the left and right ends, the color filters are not symmetric and may give a sense of incongruity as a whole. . However, FIG.
In the case of a point-sequential color linear image sensor in which the arrangement order of the color filters is line-symmetrical from the center position to the left and right as shown in Fig. 7, light enters from a direction slightly different from the assumed angle, and color mixing occurs. However, the tendency is axisymmetric on the left and right, so that the apparent impression is better than in the case of asymmetric.

Next, since an on-wafer method is often used as a method for realizing a color filter of a dot-sequential color linear image sensor, the present invention is applied to a dot-sequential color linear image sensor using this on-wafer method. Another embodiment will be described. FIG. 5 is a diagram for explaining the process of the on-wafer method, and FIG. 6 is a diagram showing an embodiment using a dot-sequential color linear image sensor manufactured by the on-wafer method and having the same color filter arrangement order from the left end to the right end. FIG. 7 is a diagram showing an embodiment using a point-sequential color linear image sensor manufactured by an on-wafer method and arranged in an order of color filters symmetrical to the left and right from the center.

In the on-wafer process, a light-shielding layer (aluminum layer) 12 is formed on a photosensitive pixel 13 having a photodiode as shown in FIG. 5A. Smoothing layer 14,
The color filter 11B shown in FIG. 5C, the intermediate layer 15 shown in FIG. 5D, the color filter 11R shown in FIG. 5E, the intermediate layer 16 shown in FIG. 5F, the color filter 11G shown in FIG.
Overcoat layers (protective layers) 17 shown in FIG. 5H are sequentially formed. In the formation of the smooth layer 14 and the intermediate layers 15 and 16,
A transparent protective resist (acrylic) is applied to ensure smoothness of the surface irregularities and adhesion to the dyeing resist. In forming the color filters 11B, 11R, and 11G, a water-soluble dyeing layer resist (casein) is used. Dipped in dyeing solution and dried. In the process of the on-wafer method, a good color filter can be realized with good accuracy and low cost in this way.
Since there is a difference in the height of each color filter, there is a disadvantage that the filter is more susceptible to the inclination of the incident angle than in the above embodiment.

That is, in a dot-sequential color linear image sensor manufactured by the on-wafer method, FIGS.
As shown in (1), a portion where the color filter overlaps at the end of the sensor with respect to the incident light or a gap portion is formed on the contrary. for that reason,
In the point-sequential color linear image sensor manufactured by the on-wafer method, as in the above-described embodiment,
When the color filters are shifted as shown in FIGS. 6D and 6F on both left and right sides except for the vicinity of the center of the sensor, the shift amount is different depending on the height of the color filters because the height of the color filters varies depending on the color. The upper one,
Also, as the distance from the center position of the sensor increases, the shift amount needs to be increased.

As described above, the arrangement order of the color filters is the same from the left end to the right end. In the same manner as in the embodiment shown in FIG. 4, even if the color filters are line-symmetric at the center of the sensor as shown in FIG. Good. By doing so, it is possible to prevent an asymmetric color mixing tendency from occurring. Further, for the sake of manufacturing, it is desirable that the size of the color filters provided on the sensor be the same regardless of the location. In this case, the state of overlapping of the color filters at the ends is shown in FIG.
B and C are different from FIGS. 7D, 7E and 7F. FIG. 7A,
In B and C, the color filters near the center are high, so that all the gaps are generated between the adjacent filters. Conversely, in FIGS. 7D, E and F, the color filters near the center are low. Therefore, a gap is generated only in a part. Considering the case where light from other than the assumed angle exists, the latter is more preferable.

FIG. 8 is a view showing an embodiment including the entire optical system of the image reading apparatus according to the present invention. When a good image reading device is realized by mounting a point-sequential color linear image sensor as in each of the above embodiments, the optical axis of the imaging optical system of the device is set at the center of the sensor, or of the symmetrically arranged pixels. In such a case, it is necessary to match the symmetry axis as much as possible. Further, the angle of the light beam (principal ray) passing through the imaging optical system of the image reading device and entering the sensor may be made to substantially coincide with the incident light angle to the sensor that minimizes the occurrence of color mixing. is necessary. Further, when the maximum half angle of view (θ _max in FIG. 2) of the apparatus is too large, a phenomenon that the resolution characteristic of the lens is deteriorated at the end portion is caused. There is a problem that the optical path length becomes longer and the device becomes larger. After all, as the place practical, considering the conditions above, the maximum value theta _max angle of the principal ray is preferably in the range of _{10 ° ≦ θ max ≦ 20 °} . FIG. 8 shows a model having almost the same size as that of the conventional apparatus within this range, in which the original surface 21 is 317.5 mm, and the pixel row length of the sensor 23 (14 μm × 5).
000 pixels) is 70 mm, the optical path length from the document surface 21 to the sensor 23 is 420 mm, and the reduction ratio of the lens 22 is 1 /
It is 4.5. The half angle of view in this case is about 18 °
Becomes Therefore, it is desirable that the dot-sequential color linear image sensor is also realized so as to minimize the occurrence of color mixture with respect to incident light of, for example, 18 ° within the above range.

FIG. 9 is a view showing still another embodiment of the image reading apparatus according to the present invention in which the width of the shielding layer is changed. In the conventional image reading apparatus, the color mixing caused by the incident light from the adjacent color filters as shown by the dashed line shown in FIGS. 9A and 9C is not a shift of the color filters but a shielding as shown in FIGS. 9D and F. This is realized by changing the width of the layer. That is, when the width of the shielding layer is increased, the light amount is slightly reduced in the central portion of the sensor illustrated in FIG. 9E, but the transmitted light components of the adjacent pixels can be shielded on both left and right sides as illustrated in FIGS. . In this manner, the width of the shielding layer may be changed so as to extend outside the intermediate position between adjacent pixels and widen to block light of the mixed color component (dashed line), or similar to the shift amount of the color filter. The position of the shielding layer may be changed according to the distance from the center. In this case, since the incident light is line-symmetrical on the left and right sides of the sensor, the position of the shielding layer may be line-symmetrical.

FIG. 10 is a view showing the overall system configuration of the image processing apparatus, FIG. 11 is a view showing a schematic configuration of the image processing apparatus,
FIG. 12 is a diagram showing a configuration example of the image reading unit, and FIG. 13 is a diagram for explaining a reading direction of a document reading signal by the image reading unit.

The overall system configuration of the image processing apparatus equipped with the color linear image sensor according to the present invention includes, for example, an image input unit (scanner unit, IIT) 51 for reading an image and converting it into an electric signal as shown in FIG. An image processing unit (IPS) 52 that corrects, converts, and adjusts an image signal of a read document; and an image output unit that converts an image signal (electric signal) into a light signal to form an image by an electrostatic latent image. (IOT) 53 and the image processing unit (IPS)
An image editing unit 55 that performs editing processing is connected to 52. Then, an image signal from an external device 54 such as a personal computer having a scanner, a workstation, or a facsimile is input to the image processing unit 52, and an image signal output from the image processing unit 52 is input to the external device 54. FIG. 11 shows a schematic configuration of such an image processing apparatus, and FIG. 12 shows a configuration example of an image reading unit.

The image input unit 51 employs a reduction optical system using an illuminating device 82 such as a fluorescent lamp or a halogen lamp, reflection mirrors 83 and 84, and an optical lens 85, and each color 50
An RGB 3-line CCD sensor 61 of 00 pixels is mounted. The signal read by the CCD sensor 61 is amplified by an analog amplifier and converted to a digital signal by an A / D converter. The control board 72 includes an image processing unit 5
2 and an electric circuit of the image output unit 53 are mounted. In the image processing unit 52, for example, 8
Various processes are performed on the bit RGB digital signals to generate C (cyan), M (magenta), Y (yellow), and B _k (black) signals that match the characteristics of the image output unit 53. The image output unit 53 inputs the CMYB _k signals sequentially sent first from the image processing unit 52 to the driver for controlling the lighting of the semiconductor laser is converted into an optical signal. RO
S (Raster Output Scanner)
The unit 65 includes an infrared semiconductor laser, a lens, and a polygon mirror, and scans the photosensitive drum 63 as spot light of, for example, 60 μm. The photosensitive drum 63 is
It is charged by a charger, and an electrostatic latent image is formed by a light signal. The latent image becomes a toner image by a two-component magnetic brush phenomenon on the rotary developing device 66, and is transferred onto a sheet adsorbed on a transfer drum. The photosensitive drum 63 is
Excess toner is cleaned by the cleaner 64.
This process is repeated in the order of B _k , Y, M, and C, and multiple transfer is performed on paper. The paper is peeled from the transfer drum, and the toner is fixed by a fixing device.

In the image input section 51, when a document 88 is placed downward on a document table 81 as shown in FIG. 12, the illumination device 82 illuminates the document 88, and the reflection mirrors 83, 84,
A document image is formed on a linear CCD sensor 86 via an optical lens 85, and the document is read in the main scanning direction.
The CCD sensor 86 converts the original image into an electric signal.
The illuminating device 82 and the reflecting mirrors 83 and 84 are moved by a motor drive system (not shown) in a direction indicated by an arrow in the drawing to scan the document table 81 and perform reading in the sub-scanning direction. In this way, an electric signal corresponding to the original image, that is, an image signal is obtained from the CCD sensor 86.

Further, in the image reading apparatus shown in FIG.
Means for removing so-called shading such as density unevenness due to dirt or the like and unevenness of the luminous intensity distribution of the optical lens 85 are provided. That is, the white reference plate 87 for shading correction is provided at the scanning start end of the document table 81 in the sub-scanning direction. The white reference plate 87 is a plate-like body that functions as a density reference plate for generating a signal serving as a reference when correcting an image signal, and has a front surface uniformly painted, for example, in white. As shown in FIG. Note that in FIG.
8, the right side is the front of the apparatus, that is, the operator side, the left side is the back side, and the upper side is the left side when viewed from the front of the apparatus. Also, in FIG. 13, the document 88 is main-scanned from left to right and sub-scanned from top to bottom. When reading the document, the white reference plate 87 is read prior to scanning of the document 88. After that, the original is scanned to perform image signal correction based on the read signal of the white reference plate 87.
Reference numeral 89 denotes a cover for the white reference plate 87 and a butting guide for defining the document position.

In the image processing section 52, the BGR signal from the image input section 51 has 8-bit data (25
6 gradations) Enter a, CMYB _k signal (after conversion to the toner signal), a selection of toner signal X of process colors, which binarized image by the on / off data of the process color toner signal output The data is output to the unit 53, during which various data processing is performed in order to enhance the color reproducibility, the gradation reproducibility, the definition reproducibility, and the like. For example, equivalent neutral density conversion for adjusting (converting) a read signal of a color original into a gray-balanced color signal, matrix conversion for converting a BGR signal to a YMC signal, and conversion processing using a designated color in a specific area are performed. UCR (Under Color Removal; under color removal) & Black which generates an appropriate amount of B _k so as not to cause color turbidity and reduces YMC by an equal amount (under color removal) according to the amount. The halftone removal information and the edge emphasis information are generated by the generation, the digital filter, and the modulation table, and are smoothed in the case of the original of the photograph or the halftone print, and the edge emphasis is performed in the case of the original of the character or the line drawing. . Furthermore, it is intended to improve reproducibility, and has editing functions such as density adjustment, contrast adjustment, negative / positive inversion, color balance adjustment, character mode, and watermark synthesis according to the area signal. Further, the image processing unit 52 adopts an L ^* a ^* b ^* signal having brightness and hue information as a system value, and performs a color conversion of BGR → L ^* a ^* b ^* → CMY. You may.

Note that the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in the above-described embodiment, the case where the height step of each filter is equal to the thickness of the filter has been described as a typical example. However, this step may be slightly thicker or thinner, or may have a complete cross-sectional shape. It goes without saying that the effects of the present invention are not impaired even when the shape is somewhat rounded due to manufacturing reasons instead of being rectangular. In addition, the type of the color filter may be a pigment type in addition to the dye type described above. Further, in the above-described embodiment, the case where the color filters are three colors of RGB has been described.
The present invention can be similarly applied to the case of a three-color configuration or a filter configuration of other two or more colors, and the effects are of course the same.

[0039]

As is apparent from the above description, according to the present invention, a telecentric imaging optical system using a telecentric lens is employed so that the principal ray is parallel to the optical axis in the image space, or Since the positional relationship between the shielding layer and the color filter above the pixel of the sensor is relatively shifted toward the center, it is possible to eliminate color mixing near the left and right ends that deviate from the vicinity of the optical axis of the sensor.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an image reading apparatus according to the present invention.

FIG. 2 is a diagram showing another embodiment of the image reading apparatus according to the present invention.

FIG. 3 is a diagram showing an embodiment of a dot-sequential color linear image sensor in which the arrangement order of color filters is the same over the entire length.

FIG. 4 is a diagram illustrating an embodiment of a dot-sequential color linear image sensor in which the arrangement order of the color filters is line-symmetric from the center position to the left and right.

FIG. 5 is a diagram for explaining an on-wafer method process.

FIG. 6 is a diagram showing an embodiment using a dot-sequential color linear image sensor manufactured by an on-wafer method and in which the arrangement order of color filters is the same from the left end to the right end.

FIG. 7 is a diagram showing an embodiment using a dot-sequential color linear image sensor manufactured by an on-wafer method and arranged in an order of color filters left-right symmetrically from the center.

FIG. 8 is a diagram showing an embodiment including an entire optical system of the image reading apparatus according to the present invention.

FIG. 9 is a diagram showing still another embodiment of the image reading apparatus according to the present invention in which the width of the shielding layer is changed.

FIG. 10 is a diagram illustrating an overall system configuration of an image processing apparatus.

FIG. 11 is a diagram illustrating a schematic configuration of an image processing apparatus.

FIG. 12 is a diagram illustrating a configuration example of an image reading unit.

FIG. 13 is a diagram for explaining a reading direction of a document reading signal by an image reading unit.

FIG. 14 is a diagram illustrating a configuration example of a conventional dot-sequential one-line color linear image sensor.

FIG. 15 is a diagram illustrating another configuration example of a conventional dot-sequential one-line color linear image sensor.

FIG. 16 is a diagram showing the internal configuration of a chip of the dot-sequential one-line color linear image sensor shown in FIG. 22;

FIG. 17 is a diagram for explaining the operation of the chip internal configuration diagram shown in FIG. 23;

FIG. 18 is a diagram illustrating a configuration example of a video signal processing circuit of a three-line color linear image sensor.

FIG. 19 is a diagram illustrating an outline of an optical system of a reduction-type original reading device.

FIG. 20 is a diagram for explaining a problem of color mixing.

[Explanation of symbols]

1: Point-sequential color linear image sensor, 2: Telecentric lens, 3: Aperture stop, 4: Platen glass,
5 ... manuscript, 11 ... color filter, 12 ... shielding layer, 13
... pixels

Claims (12)

[Claims] 1. A plurality of photosensitive pixels which are arranged on a straight line, receive image light, and accumulate electric charges, and a shielding disposed above the plurality of photosensitive pixels so as to shield between the photosensitive pixels. And a plurality of color filters arranged to selectively pass specific color light of image light with the shielding layer interposed therebetween corresponding to the plurality of photosensitive pixels, and the position of the color filter is provided. A color linear image sensor, wherein the position of a corresponding pixel is shifted toward the center of a pixel array arranged on the straight line. 2. The apparatus according to claim 1, wherein the shift amount is set in proportion to a distance from the center position.
A color linear image sensor as described. 3. The color linear image sensor according to claim 1, wherein the shift amount is set to be larger for the color filters of different colors in the color filters located above the color filters of different heights. 4. The color linear image sensor according to claim 1, wherein the plurality of color filters have a plurality of colors arranged in a fixed repetition order. 5. The color linear image sensor according to claim 1, wherein the color filters of the plurality of colors are arranged in a color arrangement order so as to be line-symmetric from the center position. 6. The color filters of the plurality of colors are arranged such that a color arranged closer to the center is higher than a color arranged closer to the outside of the color filters having different heights. The color linear image sensor according to claim 5, wherein: 7. A plurality of photosensitive pixels which are arranged on a straight line, receive image light, and accumulate electric charges, and a shielding disposed above the plurality of photosensitive pixels so as to shield between the photosensitive pixels. And a plurality of color filters arranged so as to selectively transmit specific color light of image light with the shielding layer interposed therebetween corresponding to the plurality of photosensitive pixels, and the position of the shielding layer is provided. A color linear image sensor wherein the pixel array arranged on the straight line is shifted toward the center in proportion to the distance from the center. 8. A plurality of photosensitive pixels which are arranged on a straight line, receive image light, and accumulate electric charge, and a shielding disposed above the plurality of photosensitive pixels so as to shield between the photosensitive pixels. And a plurality of color filters arranged so as to selectively pass specific color light of image light with the shielding layer interposed therebetween corresponding to the plurality of photosensitive pixels. A color linear image sensor shifted closer to the center of the pixel row arranged on the straight line than the position of the corresponding pixel; and an image forming optical system for forming an image light of a document on the color linear image sensor. An image reading device characterized by the above-mentioned. 9. The image reading apparatus according to claim 8, wherein an optical axis of said imaging optical system is configured to coincide with a sensor center position. 10. The image reading device according to claim 8, wherein the imaging optical system has a maximum value of an angle of a principal ray incident on the sensor of 10 ° or more and 20 ° or less. 11. The image reading apparatus according to claim 8, wherein the shift amount is set according to an incident angle of image light projected by the imaging optical system. 12. A plurality of photosensitive pixels which are arranged on a straight line, receive image light, and accumulate electric charge, and a shielding disposed above the plurality of photosensitive pixels so as to shield between the photosensitive pixels. A plurality of color filters arranged so as to selectively pass specific color light of image light with the shielding layer interposed therebetween corresponding to the plurality of photosensitive pixels, and the photosensitive pixel, the shielding layer, and the color. An image reading device comprising: a telecentric imaging optical system that projects an image onto a point-sequential color linear image sensor including a filter.