JP2000032214A - Color image sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the color image sensor of a contact on-chip filter type capable of correcting the deviation of image formation position by the color aberration of SLA. SOLUTION: This color image sensor irradiates an original 3 by using a white light source 1, forms the object image to a photodetector by a 'Selfoc(R)' lens array 5, sticks an on-chip filter 8 onto the photodetector and outputs color information color resolved by the on-chip filter. In this case, by using the on-chip filters of red, green and blue as the filter and using the ones of different film thickness as the on-chip filters for the respective colors or using the materials of different refractive indexes, the image forming position deviation by the color aberration of the SLA is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image sensor of a contact-on-chip filter type.

[0002]

2. Description of the Related Art For example, contact color image reading apparatuses such as image scanners and film scanners are known.
In order to read a color image on a recording medium such as a document by shading information, (1) a light source switching method in which R (red), G (green), and B (blue) light sources are switched and read by a monochrome sensor; RGB filter switching using a white light source, a filter switching method for reading with a black and white sensor, (3) RGB using a white light source
An on-chip filter type color image sensor that reads a B filter with a color sensor attached to a light receiving element is provided.

(Description of FIG. 11) FIG. 11 is a cross-sectional view showing the basic principle of a conventional contact-on-chip filter type color image sensor. In FIG. 11, 101 is a white light source, 102 is a platen glass, 103 is a document, 104 is a document reading position, and 105 is a selfoc lens array (S
LA). Reference numeral 106 denotes a sensor plate, 107 denotes a light receiving element, and 108 denotes an on-chip filter including R (red), G (green), and B (blue).

Irradiation light from a white light source 101 passes through an original platen glass 102 at an angle of about 45 degrees and irradiates an original reading position 104 of an original 103.

The reflected light at the document reading position 104 is
Diffuse reflected light according to the object density.

The SLA 105 is mounted on the normal line of the document reading position 104 so as to be perpendicular to the document 103. S
Since the LA 105 is located on the normal line of the document reading position, the SLA 105 receives the subject density at the document reading position 104 as 0 degree diffuse reflection light.

On the emission light side of the SLA 105, a sensor plate 106, a black and white light receiving element 107 previously mounted on the sensor plate 106, and an on-chip filter 108 composed of arbitrary picture element configurations (filter configurations) R, G, B Is attached.

The SLA 105 forms a subject image at the document reading position 104 on the light receiving element 107.

The light receiving element 107 converts the subject image into an electric signal.

Since an on-chip filter composed of R, G, and B is attached to the light receiving element 107 in advance, the electric signals output from the light receiving element 107 are R, G, and B color signals. As described above, the close-contact on-chip filter type color image sensor operates.

(Explanation of FIG. 12) FIG. 12 is a sectional view showing a basic optical arrangement of a contact image sensor using an SLA. 12, reference numeral 103 denotes a document; 104, a document reading position; 105, an SLA; 106, a sensor plate;
07 is a light receiving element, Tc101 is a conjugate length (distance between object image planes from the document reading position to the light receiving element), and Z101 is SL
The length A and L101 are the working distance (the distance from the SLA end face to the document reading position or the light receiving element).

The Tc 101 (conjugate length) is fixed by the physical properties of the SLA 105 unless a medium having a different refractive index exists in the light propagation path from the document reading position 104 to the light receiving element 107. By attaching the SLA 105 to the central portion between the document reading position 104 and the light receiving element 107, the subject image at the document reading position 104 is accurately formed on the light receiving element 107. For details, refer to the literature: “Small, lightweight, high-performance lens Selfoc Lens Array Cat.SLA Vol4 / printed 198
9.7 (Nippon Sheet Glass Co., Ltd.) ”, page 14,“ Imaging Equations and Specifications ”.

(Explanation of FIG. 13) FIG. 13 is a sectional view showing the optical arrangement of a contact image sensor using an SLA. FIG.
3, reference numeral 102 denotes a platen glass; 103, a document;
04 is the document reading position, 105 is the SLA, 106 is the sensor plate, 107 is the light receiving element, 108 is the on-chip filter, Tc102 is the conjugate length, Z101 is the SLA length, L102 is the working distance (the document is read from one end of the SLA. L103 is the working distance (the distance from the other end face of the SLA to the light receiving element), t101 is the thickness of the platen glass, and t102 is the thickness of the on-chip filter.

A medium having a different refractive index (the platen glass 10) is provided in the light propagation path from the document reading position 104 to the SLA 105.
2) exists, and the light receiving element 107
There is an on-chip filter in the light propagation path up to. Therefore, the distance of Tc102 (conjugate length) or SLA1
The mounting position of 05 changes depending on the thickness and refractive index of the platen glass and the thickness and refractive index of the on-chip filter.

(Comparison of FIGS. 12 and 13) Conjugation length Tc10
1 and Tc102, working distances L101 and L102, L10
The comparison of No. 3 will be described with reference to FIGS. First, as described above, the conjugate length Tc101 or the working distance L101 in FIG. 12 is determined by the physical properties of the SLA. When the refractive index of the platen glass is N101 and the refractive index of the on-chip filter is N102, Tc102, L
102 and L103 can be calculated by the following equations. L102 = (t101x (N101-1) / N101) + L101 L103 = (t102x (N102-1) / N102) + L101 Tc102 = Tc101 + (t101x (N101-1) / N101) + (t102x (N102-1)
/ N102)

According to the above formula, for example, the document and the SL
This proves that the focal position on the light receiving element is changed by inserting a transmissive material with a predetermined thickness between A or between the SLA and the light receiving element. For example, the above-mentioned platen glass (thickness t101, refractive index N101) is referred to as a document
Since the document is inserted between LAs, the focal position of the document reading position changes by (t101x (N101-1) / N101). Assuming that the thickness t101 of the platen glass is 3 mm and the refractive index N101 of the platen glass is 1.52, the focal position is about 1 mm.
It will grow.

(Explanation of FIG. 14) FIG. 14 is an explanatory diagram of chromatic aberration caused by SLA. In FIG. 14, 103
Is a document, 104 is a document reading position, 105 is an SLA, 1
08R is an R (red) imaging position, 108G is a G (green) imaging position, 108B is a B (blue) imaging position Tc101 is a conjugate length, and ΔL (R) is an R (red) imaging position The shift ΔL (B) is the shift of the imaging position of B (blue). For details, refer to “Chromatic Aberration” on page 19 of the aforementioned document.

Generally, the light receiving surface of the light receiving element mounted on the sensor plate is flat. For this reason, in order to obtain a more accurate imaging position, the mounting position of the light receiving element is adjusted based on the G (green) sensor output signal and the MTF (“MTF” on page 14 of the above-mentioned document), and the color wavelength is adjusted. The resulting chromatic aberration, that is, the deterioration of the MTF due to the subject color is minimized. At this time, R (red) image position shift ΔL (R)
And B (blue) are substantially the same. Also, this image position shift differs depending on the type of SLA used. Suppose a green document is projected on the light receiving element,
If this imaging is performed accurately, M
TF shows the highest value. However, when projecting a red document, the image forming position is located farther from the light receiving element, and when projecting a blue document, the image forming position is located closer to the light receiving element, compared to the green MTF. The red and blue MTFs degrade.

[0019]

However, even if the above-described optical adjustment (means for minimizing the imaging position shift described with reference to FIG. 12) is performed, the following problems occur.

Generally, an SLA having a small F value is used in a contact color image sensor that requires miniaturization and high luminance. (Generally, the smaller the F value, the shorter the Tc. Therefore, the distance from the document to the light receiving element is shortened, and the size can be reduced.) However, the SLA with a small F value
Has large chromatic aberration and is not suitable for a color image sensor. Even if an SLA with small chromatic aberration is used at the expense of the F-number, the imaging position shift due to the color wavelength always occurs, and MTF deterioration due to the color of the subject cannot be avoided. (The F value is described on page 16 of the document, and the chromatic aberration is described on page 19).

For this reason, the contact color image sensor can be reduced in size, increased in brightness, and increased in MTF due to the chromatic aberration of SLA.
Problems arise.

The present invention solves the above-mentioned conventional problems, and
It is an object of the present invention to provide a contact-on-chip filter type color image sensor capable of correcting an image forming position shift (focal shift due to a color of a document) due to LA chromatic aberration.

[0023]

For this purpose, in a color image sensor according to the present invention, a white light source is used to irradiate a subject on a document, and this subject image is formed on a light receiving element at a magnification of 1 by a selfoc lens. An on-chip filter is attached on the light-receiving element, and in a color image sensor that outputs color information separated by the on-chip filter, red, green, and blue on-chip filters are used as the filters. By using a filter having a different film thickness or using a material having a different refractive index as an on-chip filter, an image forming position on a light receiving element caused by chromatic aberration of a Selfoc lens is corrected. .

In the color image sensor according to the present invention, an on-chip filter having a uniform thickness and a thin film shape is attached on the light receiving element, and the thickness and the refractive index of each color are changed on the on-chip filter. By attaching different transparent films, an image forming position on the light receiving element caused by chromatic aberration of the Selfoc lens is corrected.

Further, in the color image sensor according to the present invention, an on-chip filter of a thin film shape having a uniform thickness is attached on the light receiving element, and a convex lens having a different refractive index for each color is provided on the on-chip filter. By attaching the transparent transparent film, the imaging position on the light receiving element caused by the chromatic aberration of the Selfoc lens is corrected.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing the basic principle of the color image sensor according to the first embodiment of the present invention.

In FIG. 1, 1 is a white light source, 2 is a platen glass, 3 is a document, 4 is a document reading position, 5 is a selfoc lens array (SLA), 6 is a sensor plate, 7
Denotes a light receiving element, and 8 denotes an on-chip filter composed of R (red), G (green), and B (blue).

First, the components shown in FIG. 1 will be described.
The white light source 1 is a tube light source including cold cathodes, hot cathodes and the like,
Alternatively, LEDs made of R (red), G (green), and B (blue) are caused to emit light simultaneously. The platen glass 2 is used for bringing the original 3 into close contact and fixing the original reading position 4.
In addition, since the platen glass transmits white irradiation light or reflected light corresponding to the document density (subject image), a white plate glass or the like having good transparency and having little influence on the color wavelength is used. The document reading position 4 is determined in advance, and the document 3 or the platen glass 2 is
The SLA 5 is arranged so as to be vertical. The distance from the document reading position 4 to the end of the SLA is determined by the thickness of the SLA 5 and the platen glass 2 and the refractive index of the platen glass 2. When the document reading position 4 is determined, the white light source 1 is fixed so that the irradiation light from the white light source 1 becomes approximately 45 degrees. A sensor plate 6, a black and white light receiving element 7, and an on-chip filter 8 are attached to the other end face of the SLA 5. The light receiving element 7 is previously mounted on a line on the sensor plate 6, and on the surface of the light receiving element 7, an R, G, B on-chip filter having an arbitrary picture element configuration is attached. . The distance from the end face of the SLA 5 to the light receiving element 7 is determined by the thickness of the SLA 5 and the on-chip filter 8 and the refractive index of the on-chip filter 8. The document reading position 4, the optical axis center of the SLA 5, and the line of the light receiving element 7 group are straight lines.

Next, the operation in FIG. 1 will be described. Irradiation light from the white light source 1 enters the platen glass 2. At this time, the irradiation light changes the angle depending on the refractive index of the platen glass, and irradiates the subject surface of the document 3 closely attached to the platen glass 2. The reflected light at the document reading position 4 becomes diffuse reflection light according to the density of the subject, and since the SLA 5 is located on the normal line of the document reading position, the SLA 5
Receives the subject density at the document reading position 4 as 0 degree diffuse reflection light. The SLA 5 forms a subject image at the document reading position 4 on the light receiving element 7, and the light receiving element 7 converts the subject image into an electric signal.

Since an on-chip filter composed of R, G, and B is previously attached to the light receiving element 7,
The electric signals output by the light receiving elements are R, G, and B color signals. An object of the present invention is to prevent the deterioration of the MTF due to chromatic aberration by changing the thickness of the on-chip filter composed of R, G, and B in units of R, G, and B. This will be described in detail with reference to FIGS. 2 and 3.

(Explanation of FIG. 2) FIG. 2 (a) shows two rows of light receiving elements 7 in the line direction (main scanning direction), and R rows in one row.
This is an example of a color image sensor in which B and B on-chip filters are alternately attached, and a G on-chip filter is attached to the other row, and illustrates the configuration and cross-sectional shape of a picture element.

In FIG. 2A, 6 is a sensor plate, 7 is a light receiving element, 8R is an on-chip filter of R (red), 8G is an on-chip filter of G (green), and 8B is B
(Blue) on-chip filter.

First, the configuration of the picture element shown in FIG. 2A will be described. On the sensor plate 6, two rows of black-and-white light receiving elements 7 are arranged and mounted in advance. The B on-chip filters 8B and R on-chip filters 8R are stuck on the light receiving element 7 so as to be alternately arranged in one row. On the other row, a G on-chip filter 8G is attached on the light receiving element 7. For example, the light receiving element to which the B on-chip filter is attached outputs a blue color signal.

In general, the operation of attaching these on-chip filters involves three processes of R, G and B individually. For example, an R mask (only the R light receiving part is exposed)
Attach the red filter with a spinner, etc., replace with the mask of B, paste the blue filter, G
Replace with a new mask and paste the green filter. Therefore, it is easy to change the materials (e.g., transmittance), the size, and the thickness of each of R, G, and B. In the present embodiment, the thickness or the refractive index of the R, G, B on-chip filters is changed to correct the imaging position shift due to the chromatic aberration of the used SLA.

FIG. 2B is a diagram showing a cross-sectional structure of the light receiving section B and the light receiving section G of FIG. 2A. Similarly, FIG. FIG. 4 is a diagram showing a cross-sectional structure of a light receiving unit of FIGS. The thickness of each on-chip filter has a relationship of 8B>8G> 8R. A specific thickness relationship will be described later.

(Explanation of FIG. 3) FIGS. 3A and 3B show three rows of light receiving elements 7 arranged in the line direction (main scanning direction).
This is a modification of the color image sensor in which R, G, and B on-chip filters are attached to each column. FIG. 3 (a)
Shows the structure of a picture element, and FIG. 3B shows a cross-sectional structure. The attachment process and the thickness relationship of the on-chip filter are the same as those described with reference to FIG.

(Fourth Description) FIGS. 4A to 4C are explanatory diagrams of the principle of the color image sensor according to the first embodiment. FIG. 4A is an optical cross-sectional view in which an R (red) on-chip filter is attached, FIG. 4B is an optical cross-sectional view in which a G (green) on-chip filter is attached, and FIG. FIG. 5 is an optical cross-sectional view showing a B (blue) on-chip filter attached thereto.

4A to 4C, reference numeral 3 denotes a document;
4 is an original reading position, 5 is an SLA, 6 is a sensor plate, 7 is a light receiving element, 8R is an on-chip filter of R (red), 8G is an on-chip filter of G (green), and 8B is B
(Blue) on-chip filter, Tc1 is conjugate length (distance between object image plane from document reading position to light receiving element), Z0 is SLA length, L0 is working distance (1) (from SLA end face to document reading position) L1 is the working distance (2) (SL
The distance from the A end face to the light receiving element), t (R) is the film thickness of the R (red) on-chip filter attached on the light receiving element, and t (G) is G ( The film thickness t (B) of the (green) on-chip filter is the film thickness of the B (blue) on-chip filter attached on the light receiving element.

In FIG. 4A, it is assumed that the original reading position 4 of the original 3 has been irradiated with white light in advance.
The 0-degree diffuse reflection light corresponding to the subject density at the document reading position 4 is incident on the SLA 5, and the subject image at the document reading position 4 is
An image is formed on the light receiving element 7. At this time, since the R on-chip filter 8R is attached on the light receiving element 7, this light receiving element forms an image of R (red) and converts it into an electric signal. The length Z0 of the SLA5 and the working distance (1) L0 without a propagation medium between the SLA5 and the document reading position are represented by SL
Determined by the physical properties of A5. The working distance (2) L1 is L1 = L0 + (t (R). (N (R) -1) /, where N (R) is the refractive index of the on-chip filter of R and t (R) is the thickness of the filter. N
(R)). The conjugate length Tc1 is the sum of the length of the SLA 5 and the working distances L0 and L1. In the present embodiment, the conjugate length Tc1 is R (red) since the on-chip filter film of R (red) is the thinnest. The optical cross section of ()) is fundamental.

FIG. 4B shows a G (green) on-chip filter 8G attached to the light receiving element 7, which forms a G (green) image and converts it into an electric signal. . Since the sensor plate 6 or the light receiving surface of the light receiving element is flat, the conjugate length is the conjugate length Tc1 in the R (red) optical cross section described with reference to FIG. If the thickness t (R) and the refractive index N (R) of the R on-chip filter 8R and the thickness t (G) and the refractive index N (G) of the G on-chip filter 8G are the same, respectively. Because the G image position is closer to the SLA side than the R image position (SLA side) due to chromatic aberration, in the present embodiment, the G on-chip filter 8G is made thicker or a material having a large refractive index is used. Means for extending the image position is performed.

FIG. 4C shows a B (blue) on-chip filter 8G attached to the light receiving element 7, which forms a B (blue) image and converts it into an electric signal. . The conjugate length is the conjugate length Tc1 in the R (red) optical cross section described with reference to FIG. Assume that the thickness t (R) of the R on-chip filter 8R, the refractive index N (R), and the B on-chip filter 8R
If the thickness t (B) and the refractive index N (B) of B are the same, the image forming position of B is closer to the image forming position of R and further to the image forming position of G (SLA side) due to chromatic aberration. To become
In the present embodiment, the B on-chip filter 8B is made thicker than the G on-chip filter 8G.
Alternatively, a means for extending the image forming position using a material having a large refractive index is used.

The image shift amounts due to the chromatic aberration of G (green) and B (blue) with respect to R (red) are represented by Δt (G) and Δt (B), respectively.
Then, the thickness t (G) of the G (green) on-chip filter
Alternatively, the thickness t (B) of the B (blue) on-chip filter can be calculated by the following equation. Note that the image shift amounts Δt (G), Δt
(B) is determined by the SLA to be used, and the image formation position in the present embodiment is adjusted by R (red). Therefore, the image shift amount of R is 0, and the thickness t of the on-chip filter of R is t. Since (R) is in the form of a thin film, it is not particularly considered in the following formula.

T (G) = Δt (G) · N (G) / (N (G) −1) (1) t (B) = Δt (B) · N (B) / ( N (B) -1) ..... (2)

As described above, according to the first embodiment, in the color image sensor of the contact on-chip filter type, first, the SLA is determined in advance, and this SLA is determined.
Determines the red image formation position (the distance from the end surface of the SLA to the light receiving element below the red on-chip filter) on the light receiving element. Since the distance from the SLA end to the image forming position is the longest in the red image forming position compared to the green and blue image forming positions, the green and blue image forming positions are closer to the front than the red image forming position. become. At this time, the amount of green image shift and the amount of blue image shift that occur with respect to the red image position are determined in advance by the physical properties of the SLA, and the thickness of the green on-chip filter is calculated according to equation (1). Is determined, and the thickness of the blue on-chip filter is determined by the equation (2). Therefore, a simple change of the manufacturing process (each film thickness when attaching the red, green, and blue on-chip filters) Or by changing the refractive index of each filter) to eliminate the imaging position shift (focal shift due to the color of the original) due to the chromatic aberration of the SLA. It can be used as an image lens.

Since the SLA having a short conjugate length can be used, the size of the image sensor can be reduced.
In general, an SLA with a short conjugate length (short lens length) has a small F value, and transmits a larger amount of reflection of a document to a light receiving element. Therefore, the amount of light input to the light receiving element becomes large (high sensitivity), and high S / N and high speed can be achieved.

Further, it is possible to prevent the MTF from being deteriorated due to the color of the subject, and to provide a color image sensor having a higher MTF and a close contact on-chip filter system.

Next, a second embodiment of the present invention will be described. (Description of FIG. 5) FIG. 5 is a sectional view showing the basic principle of the color image sensor according to the second embodiment of the present invention. In FIG. 5, 1 is a white light source, 2 is a platen glass,
3 is a document, 4 is a document reading position, 5 is a selfoc lens array (SLA), 6 is a sensor plate, 7 is a light receiving element, 8 is an on-chip composed of R (red), G (green), and B (blue). The filter 9 is a transparent film.

The basic configuration or operation principle is the same as that of the first embodiment. In the second embodiment, the red, green, and blue on-chip filters have the original thin film thickness, and the transparent film 9 is further covered on the on-chip filters. The thickness or the refractive index of the transparent film 9 is changed for each color so that the image forming positions of red, green and blue are the same. That is, a light receiving element is previously mounted on the line on the sensor plate 6, and on the surface of the light receiving element 7, an R, G, B on-chip filter having an arbitrary picture element configuration is attached. Have been. On the on-chip filter 8, a transparent film having a different thickness or refractive index is attached to each filter for each color. (The transparent film on the red on-chip filter is not particularly required.)

An optical signal corresponding to the density of the document emitted by the SLA 5 is refracted and input by the transparent film 9 and further transmitted through an on-chip filter to be input to a light receiving element. The light receiving element 7
This optical signal is converted into an electric signal. Since an on-chip filter composed of R, G, and B is attached to the light receiving element 7 in advance, the electrical signals output by the light receiving element are R, G, and B color signals.

(Description of FIG. 6) FIG. 6A shows two rows of light receiving elements 7 arranged in the line direction (main scanning direction), and one row of R elements.
FIG. 7 illustrates the configuration and cross-sectional shape of a picture element of a color image sensor in which a G on-chip filter and a B on-chip filter are alternately attached, and a G on-chip filter is attached to the other row. 6A to 6C, reference numeral 6 denotes a sensor plate, 7 denotes a light receiving element, 8R denotes an R (red) on-chip filter, 8G denotes a G (green) on-chip filter, and 8B denotes B.
(Blue) on-chip filter, 9G is a transparent film (1) attached on G (green) on-chip filter, 9B is B
(Blue) Transparent film pasted on on-chip filter
(2).

The configuration of the picture element in FIG. 6A is the same as the configuration of the picture element described in FIG. 2 of the first embodiment. In the second embodiment, the thicknesses of the R, G, and B on-chip filters may all be in the form of thin films having a uniform thickness, and it is not necessary to change the thickness. In FIG. 6A, a transparent film (1) 9G is attached on the G on-chip filter 8G,
A transparent film (2) 9B is attached on the on-chip filter 8B. By changing the thicknesses of these transparent films 9G and 9B, the imaging position shift due to the chromatic aberration of the SLA used is corrected.

FIG. 6B is a diagram showing a cross-sectional structure of the light receiving portion B of FIG. 6A and the light receiving portion G of FIG. 6A. Similarly, FIG. It is a figure showing the section structure in the G light sensing portion. The relationship of the thickness of the transparent film is G
(Green) and B (blue) unless the mutual refractive index is changed.
G <9B. A specific thickness relationship will be described later.

(Explanation of FIG. 7) FIGS. 7A and 7B show three rows of light receiving elements 7 in the line direction (main scanning direction).
An embodiment in a color image sensor in which R, G, and B on-chip filters are attached to each row, and a transparent film having a different thickness for each of G and B is attached on the G and B on-chip filters. It is. FIG. 7A shows a configuration of a picture element, and FIG. 7B shows a cross-sectional structure. The attaching process of the on-chip filter is the same as that of the related art, and the thickness relationship is the same as that of FIG.

(Explanation of FIG. 8) FIGS. 8A to 8C are explanatory diagrams of the principle of the color image sensor according to the second embodiment. 8A is an optical cross-sectional view in which an R (red) on-chip filter is attached, FIG. 8B is an optical cross-sectional view in which a G (green) on-chip filter is attached, and FIG. FIG. 5 is an optical cross-sectional view showing a B (blue) on-chip filter attached thereto.

8A to 8C, reference numeral 3 denotes an original,
4 is an original reading position, 5 is an SLA, 6 is a sensor plate, 7 is a light receiving element, 8R is an on-chip filter of R (red), 8G is an on-chip filter of G (green), and 8B is B
(Blue) on-chip filter, 9G is a transparent film (1) attached on G (green) on-chip filter, 9B is B
(Blue) Transparent film pasted on on-chip filter
(2), Tc2 is the conjugate length (distance between the object image plane from the document reading position to the light receiving element), Z0 is the length of the SLA, L0 is the working distance (1) (the distance from the SLA end face to the document reading position), L2 is the working distance (3) (the distance from the SLA end face to the light receiving element), and t (R) is R attached to the light receiving element.
The thickness of the (red) on-chip filter, t (G) 1 is the thickness of the G (green) on-chip filter attached to the light receiving element, and t (G) 2 is the G (green) on-chip filter. The thickness of the transparent film (1) 9G attached on 8G, t (B) 1 is the thickness of the B (blue) on-chip filter attached on the light receiving element, and t (B) 2 is B (Blue) The thickness of the transparent film (2) 9B attached on the on-chip filter 8B.

In FIG. 8A, it is assumed that the original reading position 4 of the original 3 has been irradiated with white light in advance.
The 0-degree diffuse reflection light corresponding to the subject density at the document reading position 4 is incident on the SLA 5, and the subject image at the document reading position 4 is
An image is formed on the light receiving element 7. At this time, since the R on-chip filter 8R is attached on the light receiving element 7, this light receiving element forms an image of R (red) and converts it into an electric signal. The length Z0 of the SLA5 and the working distance (1) L0 without a propagation medium between the SLA5 and the document reading position are represented by SL
Determined by the physical properties of A5. The working distance (3) L2 is L2 = L0 + (t (R). (N (R) -1) /, where N (R) is the refractive index of the on-chip filter of R and t (R) is its thickness. N (R))
Is determined by The conjugate length Tc2 is obtained by adding the length of the SLA 5 and the working distances L0 and L2.
The conjugate length Tc2 is based on the optical section of R (red).

FIG. 8 (b) shows a G (green) on-chip filter 8G attached on the light receiving element 7, and a transparent film (1) 9G attached on the on-chip filter 8G. The light receiving element forms a G (green) image and converts it into an electric signal. As described with reference to FIG. 6, the on-chip filters of R, G, and B may be in the form of a thin film, and it is not particularly necessary to change the thickness. Further, since the image forming position of G is closer to the image forming position of R, the transparent film 9G is attached on the G on-chip filter 8G. The transparent film 9G has an effect of refracting light emitted from the SLA and extending an image forming position on the light receiving element 7. At this time, the thickness of the transparent film 9G is changed so that the image forming position is the same as the image forming position of R, thereby correcting the image forming position shift due to the chromatic aberration of the SLA.

FIG. 8C shows a B (blue) on-chip filter 8B attached on the light receiving element 7, and a transparent film (1) 9B attached on the on-chip filter 8B. The light receiving element forms a B (blue) image and converts it into an electric signal. As described above, the R, G, and B on-chip filters may be in the form of a thin film, and need not be particularly changed in thickness. In addition, since the image forming position of B is located before the image forming position of R and further before the image forming position of G, on the on-chip filter 8B of B, it is thicker than the transparent film 9G of G. Alternatively, a transparent film 9B having a large refractive index is attached. The transparent film 9B has an effect of refracting light emitted from the SLA and extending an image forming position on the light receiving element 7.
At this time, the thickness of the transparent film 9B is changed so that the imaging position is the same as the R imaging position, thereby correcting the imaging position shift due to the chromatic aberration of the SLA.

It has been described that the R, G, and B on-chip filters in the second embodiment have a thin film shape. Therefore, if the amount of refraction deviation due to the R, G, B on-chip filter film is almost zero, or if the amount of refraction deviation is equal between R, G, and B,
Transparent film 9 attached to G (green) on-chip filter
The thickness t (G) 2 of G or the thickness t (B) 2 of the transparent film 9B attached to the B (blue) on-chip filter can be calculated by the following equation. Note that the image shift amounts Δt (G) and Δt (B)
Is determined by the SLA to be used, and the image formation position in the present embodiment is adjusted by R (red), so that the image shift amount of R is 0. Nd is the refractive index of the transparent film, which is about 1.52 in the case of glass.

T (G) 2 = Δt (G) · Nd / (Nd−1)... (3) t (B) 2 = Δt (B) · Nd / (Nd−1) .. (4)

As described above, according to the second embodiment, in the color image sensor of the contact-on-chip filter type, first, the SLA is determined in advance, and this SLA is determined.
Determines the red image formation position (the distance from the end surface of the SLA to the light receiving element below the red on-chip filter) on the light receiving element. Since the distance from the SLA end to the image forming position is the longest in the red image forming position compared to the green and blue image forming positions, the green and blue image forming positions are closer to the front than the red image forming position. become. At this time, the amount of green image shift and the amount of blue image shift generated with respect to the red image position were determined in advance based on the physical properties of the SLA, and attached to the green on-chip filter according to equation (3). Since the thickness of the transparent film is determined and the thickness of the transparent film attached to the blue on-chip filter is determined by the equation (4), a simple manufacturing process is added (the green and blue on-chip filters , A transparent film having a predetermined thickness is adhered) to extend the green or blue image forming position so that the green or blue image forming position becomes the same as the red image forming position. Since we have devised to eliminate the shift)
In addition to the effects described in the first embodiment, the transmission attenuation due to the on-chip filter film is particularly small in green and blue. Therefore, the number of manufacturing steps is slightly increased (the transparent film is attached) compared to the first embodiment, but higher sensitivity and higher S
/ N and speeding up (for example, in a CCD image sensor, the output sensitivity is determined by the light sensitivity input to the light receiving element and the charge accumulation time (generally, the time for one line of reading).
Therefore, the higher the speed, the shorter the charge accumulation time, and the more photosensitivity is required).

Next, a third embodiment of the present invention will be described. (Description of FIG. 9) FIGS. 9A to 9D show two rows of light receiving elements 7 in the line direction (main scanning direction), and R and B in one row.
Alternately apply the on-chip filter of
2 illustrates the configuration and cross-sectional shape of a picture element of a color image sensor to which the on-chip filter is attached.

9 (a) to 9 (d), reference numeral 6 denotes a sensor plate, 7 denotes a light receiving element, 8R denotes an R (red) on-chip filter, 8G denotes a G (green) on-chip filter, 8B
Is an on-chip filter of B (blue), 10R is a convex lens-like transparent film to be mounted on an on-chip filter of R (red)
(1), 10G is a convex lens-shaped transparent film (2) mounted on a G (green) on-chip filter, and 10B is a convex lens-shaped transparent film (3) mounted on a B (blue) on-chip filter.

The basic configuration or operation principle is the same as that of the first and second embodiments. In the third embodiment, the transparent film adhered on the on-chip filter described in the second embodiment is changed to a convex lens-shaped transparent film, and the sensitivity is further improved without impairing the effect of the second embodiment. It is intended for. That is, a light receiving element is previously mounted on the line on the sensor plate 6, and on the surface of the light receiving element 7, an R, G, B on-chip filter having an arbitrary picture element configuration is attached. Have been. On the on-chip filter, a convex lens-like transparent film having a different thickness and a different refractive index is attached to each filter for each color. The optical signal emitted from the SLA 5 according to the original density passes through the convex lens-shaped transparent film and the on-chip filter, and is then input to the light receiving element. The light receiving element 7 converts this optical signal into an electric signal. The light receiving element 7 has
Since the on-chip filter composed of R, G, and B is attached, the electric signal output from the light receiving element is an R, G, and B color signal having an arbitrary picture element configuration.

FIGS. 9 (a) and 9 (b) show two rows of light receiving elements 7 in the line direction (main scanning direction), and R and B on-chip filters are alternately attached to one row, and the other row. It is a figure explaining composition of a picture element of a color image sensor which attached a G on-chip filter to a column. FIG. 9 (c)
FIG. 9A shows a cross-sectional structure of the light receiving unit of B and G in FIG. 9A or 9B, and FIG. 9D shows a cross-sectional structure of the light receiving unit of R and the light receiving unit of G. FIG.

The configuration of the picture elements in FIGS. 9A and 9B is the same as the configuration of the picture elements described with reference to FIG. 2 of the first embodiment or FIG. 6 of the second embodiment. In the third embodiment, the thicknesses of the R, G, and B on-chip filters do not need to be particularly changed as in the second embodiment. Therefore, the R, G, and B on-chip filters may all be in the form of a thin film. In FIG. 9A, the convex lens-shaped transparent film (1) 10R is placed on the R on-chip filter 8R, and the convex lens-shaped transparent film (3) 1 is placed on the B on-chip filter 8B.
0B is attached to each light receiving portion, and a long convex lens-like transparent film (2) 10 is provided on the G on-chip filter 8G.
Attach G. In this embodiment, based on the thickness of the R convex lens-like transparent film (1) 10R, the G convex lens-like transparent film (2) 10G or the B convex lens-like transparent film (3) 1
By changing 0B to a predetermined thickness, the used SLA
Of the imaging position due to the chromatic aberration of

In the second embodiment, it has been described that a transparent film is not particularly required on the R on-chip filter. However, in the third embodiment, it is desired to increase the light receiving sensitivity of R. , G and B on the on-chip filters.
The relation of the refractive index of each convex lens-shaped transparent film is 10R> 10G
> 10B.

(Explanation of FIG. 10) FIGS. 10 (a) to 10 (c)
FIG. 9 is an optical sectional view illustrating a basic principle of a color image sensor according to a third embodiment. 10A is an optical sectional view of a red light receiving section, FIG. 10B is an optical sectional view of a green light receiving section, and FIG. 10C is an optical sectional view of a blue light receiving section.

10 (a) to 10 (c), reference numeral 3 denotes an original, 4 denotes an original reading position, 5 denotes an SLA, 6 denotes a sensor plate, 7 denotes a light receiving element, 8R denotes an R (red) on-chip filter, 8G Is the G (green) on-chip filter, 8B is B
(Blue) on-chip filter, 10R: convex lens-shaped transparent film (1), mounted on R (red) on-chip filter, 1
0G is a convex lens-shaped transparent film (2) mounted on a G (green) on-chip filter, 10B is a convex lens-shaped transparent film (3) mounted on a B (blue) on-chip filter, and Tc3 is a conjugate length (light receiving from the document reading position). Distance between the object and the image plane to the element), Z0 is the length of the SLA, and L0 is the working distance (1) (SL
L3 is the working distance (4) (the distance from the SLA end face to the light receiving element).

In FIG. 10A, it is assumed that the original reading position 4 of the original 3 has been irradiated with white light in advance. The 0-degree diffuse reflected light corresponding to the subject density at the document reading position 4 enters the SLA 5, and forms the subject image at the document reading position 4 on the light receiving element 7. At this time, since the R on-chip filter 8R is attached on the light receiving element 7, this light receiving element forms an image of R (red) and converts it into an electric signal. The length Z0 of the SLA 5 and the working distance (1) L0 without a propagation medium between the SLA 5 and the document reading position are represented by S
Determined by the physical properties of LA5. The working distance (4) L3 varies depending on the refractive index of the convex lens-shaped transparent film (1) concentrically luminous with the light receiving element. The conjugate length Tc3 is the sum of the length of the SLA 5 and the working distances L0 and L3. In the description of the third embodiment, the conjugate length Tc3 is based on the optical cross section of R (red).

FIG. 10B shows that G (green) is formed on the light receiving element 7.
Is attached, and a convex lens-like transparent film (2) 10G is attached on the on-chip filter 8G. The light receiving element forms a G (green) image,
Convert to electrical signals. As described in FIG. 9, R, G,
The on-chip filter of B may be in the form of a thin film, and it is not particularly necessary to change the thickness. Further, since the image forming position of G is closer to the image forming position of R, the convex lens-like transparent film (2) having a smaller refractive index than the convex lens-like transparent film (1) 10R is provided on the G on-chip filter 8G. ) Attach 10G. The convex lens-like transparent film 10G has the effect of refracting and concentrically radiating the radiated light from the SLA, extending the image formation position on the light receiving element 7, or expanding the subject area to be imaged. At this time, the refractive index of the convex lens-like transparent film 10G is changed, and the image forming position is made the same as the image forming position of R, whereby SL
The imaging position shift due to the chromatic aberration of A is corrected.

FIG. 10C shows that B (blue) is formed on the light receiving element 7.
Is attached, and a convex lens-like transparent film (3) 10B is attached on the on-chip filter 8B. The light receiving element forms an image of B (blue),
Convert to electrical signals. As described above, the R, G, and B on-chip filters may have a thin film shape with a uniform thickness, and there is no particular need to change the thickness. The image forming position of B is
Since it is before the image forming position of R and further before the image forming position of G, a convex lens having a smaller refractive index than the convex lens transparent film (2) 10G of G is formed on the on-chip filter 8B of B. Attach the transparent film (3) 10B. The convex lens-like transparent film (3) 10B has the effect of refracting and concentrically radiating the light emitted from the SLA, extending the image forming position on the light receiving element 7, or expanding the subject area to form an image. At this time, the refractive index of the convex lens-like transparent film (3) 10B is changed, and the image forming position is made the same as the image forming position of R, so that S
An image forming position shift caused by LA chromatic aberration is corrected.

As described above, according to the third embodiment, in the color image sensor of the contact on-chip filter type, first, the SLA is determined in advance, and this SLA is determined.
Determines the red image formation position (the distance from the end surface of the SLA to the light receiving element below the red on-chip filter) on the light receiving element. Since the distance from the SLA end to the image forming position is the longest in the red image forming position compared to the green and blue image forming positions, the green and blue image forming positions are closer to the front than the red image forming position. become. At this time, the amount of green image shift and the amount of blue image shift that occur with respect to the red image position are determined in advance by the physical properties of the SLA, and the convex lens-like transparent film attached on the G on-chip filter is obtained. The image forming distance of R and the image forming distance of G are made equal by the refractive index of R, and the image formation of R, G and B is made by the refractive index of the convex lens-like transparent film attached on the on-chip filter of B. Since the distance is set to be the same, by attaching a convex lens-shaped transparent film having a different refractive index for each color, the amount of light received by the light receiving element is made more sensitive than in the second embodiment, and It becomes possible to correct an imaging position shift due to chromatic aberration caused by SLA.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention. An example is shown below. (1) In the first, second, and third embodiments, the R, G, and B on-chip filters have been described. However, Y (yellow), M (magenta), C (cyan) ) Etc. can obtain the same effect. (2) In the first embodiment, the second embodiment, and the third embodiment, for example, instead of a long shape such as a G (green) on-chip filter in FIG. ), B
On-chip filters such as (blue) scattered for each light receiving element may be used. (3) In the second embodiment, it has been described that the on-chip filter is pasted on the light receiving element and the transparent film is further pasted. However, the transparent film is pasted on the light receiving element and the on-chip filter is pasted. It may be a configuration. (4) In the second embodiment, it has been described that a transparent film is attached. However, for example, an infrared cut filter may be used. (5) In the third embodiment, it has been described that the convex lens-shaped transparent film is attached. However, for example, a convex lens-shaped transparent film made of an infrared cut filter may be used. (6) In the third embodiment, it has been described that the convex lens-shaped transparent film is mounted on the on-chip filter. However, a convex lens-shaped transparent film formed of a color filter may be used. (7) In the embodiment of FIG. 3, it has been described that the convex lens-like transparent films having different refractive indexes are attached for each color, but the achromatic lens-like transparent film (the lens-like transparent film whose refractive index changes depending on the color wavelength) is used. May be used.

[0075]

As described above in detail, according to the first aspect, the subject of the original is illuminated using the white light source,
In a color image sensor that forms an image of the subject on a light receiving element with a selfoc lens at an equal size, attaches an on-chip filter on the light receiving element, and outputs color information separated by the on-chip filter, By using red, green, and blue on-chip filters and using on-chip filters with different film thicknesses or materials with different refractive indices for each color, simple manufacturing process changes (Change the film thickness or change the refractive index of each filter when attaching red, green and blue on-chip filters)
The imaging position shift due to the chromatic aberration of A can be eliminated, and even an SLA with a short conjugate length can be used as an imaging lens of a contact color image sensor.

According to the second aspect of the present invention, in the color image sensor, an on-chip filter having a thin film shape having a uniform thickness is attached on the light-receiving element, and furthermore, the on-chip filter is color-coded. By attaching transparent films with different thicknesses and refractive indices, green or blue images can be formed by adding a simple manufacturing process (pasting a transparent film with a predetermined thickness on green and blue on-chip filters). The position can be extended to be the same as the red imaging position, and the imaging position shift due to the chromatic aberration of the SLA can be eliminated. In addition to the above effects, transmission attenuation due to the on-chip filter film particularly in green and blue can be reduced. Can be reduced. Therefore, higher sensitivity, higher S / N, and higher speed can be expected.

Further, according to the third aspect of the invention, in the color image sensor, an on-chip filter having a thin film shape having a uniform film thickness is attached on the light-receiving element, and the on-chip filter is further classified by color. By attaching the convex lens-shaped transparent films having different refractive indices, it is possible to correct the imaging position shift due to the chromatic aberration caused by the SLA and to improve the sensitivity of the light receiving element.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a basic principle of a color image sensor according to a first embodiment.

FIG. 2 is a diagram illustrating a configuration and a cross-sectional shape of a picture element of the color image sensor according to the first embodiment.

FIG. 3 is a diagram showing a modification of the first embodiment.

FIG. 4 is a diagram illustrating the principle of the first embodiment.

FIG. 5 is a sectional view illustrating a basic principle of a color image sensor according to a second embodiment.

FIG. 6 is a diagram illustrating a configuration and a cross-sectional shape of a picture element of a color image sensor according to a second embodiment.

FIG. 7 is a diagram showing a modification of the second embodiment.

FIG. 8 is a diagram illustrating the principle of the second embodiment.

FIG. 9 is a diagram illustrating a configuration and a cross-sectional shape of a picture element of a color image sensor according to a third embodiment.

FIG. 10 is a diagram illustrating the principle of the third embodiment.

FIG. 11 is a sectional view showing the basic principle of a conventional contact-on-chip filter type color image sensor.

FIG. 12 is a sectional view of a basic optical arrangement of a contact image sensor using an SLA.

FIG. 13 is a sectional view showing the optical arrangement of a contact image sensor using an SLA.

FIG. 14 is an explanatory diagram of chromatic aberration due to SLA.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 White light source 2 Platen glass 3 Document 4 Document reading position 5 Selfoc lens array (SLA) 6 Sensor plate 7 Light receiving element 8 On-chip filter

Claims (3)

[Claims] 1. An object on a document is illuminated using a white light source, an image of the object is formed on a light receiving element by a selfoc lens at an equal size, and an on-chip filter is attached on the light receiving element. In a color image sensor that outputs color information separated by color, red, green, and blue on-chip filters are used as the filters.
A color image sensor using a material having a different thickness or a material having a different refractive index. 2. The color image sensor according to claim 1, wherein an on-chip filter having a uniform film thickness is affixed on the light receiving element, and the thickness and refraction of each color are formed on the on-chip filter. A color image sensor having transparent films of different rates attached. 3. The color image sensor according to claim 1, wherein an on-chip filter having a uniform thickness and a thin film shape is attached on the light receiving element, and a refractive index of each color is formed on the on-chip filter. A color image sensor having different transparent transparent lenses.