JP2000188667A - Color image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of parts and adjusting work and to simplify and miniaturize the whole device by integrally constituting an image forming optical system and a color discomposing means, and properly setting respective elements constituting the device, thereby guiding each color light to be subjected to color reparation by the color discomposing means onto a corresponding line sensor surface without deviation, without adjusting the color discomposing means. SOLUTION: A color image is formed on the surface of a light-receiving means 4 obtained by arranging plural line sensors on the same substrate surface via a color discomposing means 3 by an image forming optical system 2. If (x) is set as the distance from the means 3 to a light-receiving means 4, (n) as the line interval of a means 4/the size of the subscanning direction of the single element of the means 4, (f) as the focal distance of the system 2. B as the image-forming magnification of the system 2, α as the variation (%) of the focal distance of the system 2 and (k) as a distance (a positive value) from the final surface of the system 2 to an image side main point, the condition n.f(1-β).α/100<x<f(1-β)-k is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image reading apparatus, and more particularly, to an image forming optical system and a color separating means which are integrally formed, and by appropriately setting each element constituting the apparatus, a color separating means is provided. The present invention relates to a color image reading apparatus suitable for an apparatus such as a color scanner or a color facsimile which can read color image information on a document surface with high accuracy by a reading optical system having a simple configuration without adjusting the image.

[0002]

2. Description of the Related Art Conventionally, color image information on a document surface is imaged on a line sensor (CCD) surface via an optical system, and color image information is converted using an output signal from the line sensor at this time. Various digital reading devices have been proposed.

[0003] For example, FIG. 3 is a schematic view of a main part of an optical system of a conventional color image reading apparatus. In the figure, when a light beam from a color image on a document surface 31 is condensed by an image forming lens 32 and formed on a line sensor surface described later, the light beam is transmitted through a 3P prism 33, for example, to red (R), green, and the like. (G) After color separation into three colors of blue (B), each line sensor 3
Light is guided on 4, 35, and 36 surfaces. The color images formed on the respective line sensors 34, 35, 36 are line-scanned in the sub-scanning direction, and reading is performed for each color light.

FIG. 4 is a schematic view of a main part of an optical system of a conventional color image reading apparatus. In this figure, when a light beam from a color image on a document surface 31 is condensed by an imaging lens 32 and formed on a line sensor surface described later, a wavelength selective transmission film having dichroism is added to the light beam. The light is separated into three color lights corresponding to three colors via two beam splitters (color separation means) 44 and 45 for color separation.

[0005] A color image based on the three color lights is converted into a color image.
Three line sensors are formed on a so-called monolithic three-line sensor (light receiving means) 43 provided on the same substrate surface. Thus, the color image is line-scanned in the sub-scanning direction, and reading is performed for each color light.

FIG. 5 is an explanatory view of the monolithic three-line sensor 43 shown in FIG. 4. The monolithic three-line sensor 43 has three line sensors (CCD) 51, 52, 53 parallel to each other as shown in FIG. Are arranged at a finite distance from each other on the same substrate surface, and a color filter (not shown) based on each color light is provided on the line sensor surface.

The distances S ₁ , S ₂ between the line sensors 51, 52, 53 are generally made to be, for example, about 0.064 to 0.2 mm due to various manufacturing conditions. The pixel width W1, W2 of 54 is, for example, 8 μm × 8
μm, about 10 μm × 10 μm.

As shown in FIG. 6, distances S ₁ and S ₂ between the other two lines 51 and 53 with respect to the center line 52 of the monolithic three-line sensor are generally equidistant in opposite directions, respectively. Pixel size in the sub-scanning direction (FIG. 5
(Refer to) W2. This is for the following reasons.

That is, as shown in FIG. 6, when a color image is read by the above-described monolithic three-line sensor using only the normal imaging optical system 32, the three line sensors 51, 52, 53 simultaneously operate. Original surface 3 that can be read
The three reading positions 51 are different from each other as shown in FIG.
', 52' and 53 '.

For this reason, the signal components of the three colors (R, G, B) at an arbitrary position on the document surface 31 cannot be read at the same time. Come up.

To this end, the distances S ₁ and S ₂ between each line of the three-line sensor are set to be an integral multiple of each pixel size W2, and a redundant line memory is provided in accordance with the distances. By delaying each of the G and R signals (signal components based on the G and R color lights) with respect to the (signal components based on the B color light), a composite signal component of three colors can be obtained relatively easily.

Therefore, as described above, the distances S ₁ and S ₂ between the other two line sensors 51 and 53 with respect to the center line sensor 52 of the three line sensors are set to be an integral multiple of the pixel size W2 in the sub-scanning direction. It is doing.

As still another method, as shown in FIG.
4, a transmission type one-dimensional blazed diffraction grating 73 as a color separating means is arranged in the image forming optical path away from the exit pupil of the image forming lens (projection lens) 32 in the direction of the light receiving means 74 to perform transmission diffraction. A color image reading apparatus that reads out the color image information by performing color separation by using the color image information of one line on the original surface 31 on the three-line sensor 74 surface in the sub-scanning direction to form an image. Proposed.

A color image reading apparatus using a one-dimensional blazed diffraction grating as the color separation means has the following problems.

The diffraction efficiency of the one-dimensional blazed diffraction grating is
For example, when the wavelength characteristic shown in FIG. 8 is used as an example, no matter how the grating pitch of the one-dimensional blazed diffraction grating is set, the angles of the ± 1st-order diffracted light with respect to the 0th-order diffracted light do not match, and the asymmetry remains. For this reason, the intervals between the color lights (color light intervals) on the three-line sensor surface are different.

Therefore, as a correction means for correcting the deviation of the imaging position caused by the difference in the wavelength of each color light (diffracted light) color-separated by the one-dimensional blazed diffraction grating using the difference in the refractive index due to the difference in the wavelength. By arranging the flat glass at an angle with respect to the optical axis of the imaging optical system and integrally forming the flat glass and the one-dimensional blazed diffraction grating, each color light on the three-line sensor surface can be easily configured. The intervals are made equal.

[0017]

The color image reading apparatus shown in FIG. 3 requires three independent line sensors,
Further, high precision is required, and a 3P prism which is difficult to manufacture is required, so that the entire apparatus becomes complicated and expensive. In addition, it is necessary to perform matching adjustment between the imaged light beam and each line sensor three times independently, and there is a problem that assembly adjustment is troublesome.

In the color image reading apparatus shown in FIG. 4, when the thickness of the beam splitters 44 and 45 is x, the distance between each line of the line sensor is 2√2x. now,
If the distance between the lines of the line sensor, which is preferable for manufacturing, is about 0.064 to 0.2 mm, the plate thickness x of the beam splitters 44 and 45 is about 23 to 70 μm.

In general, it is very difficult to construct a beam splitter having such a small thickness and good optically flatness. If a beam splitter having such a thickness is used, an image is formed on a line sensor surface. There is a problem that the optical performance of a color image is reduced.

In the color image reading apparatus having the color separating means shown in FIGS. 4 and 7, the light receiving means ( In addition to performing optical adjustment such as shifting the three-line sensor in the optical axis direction, the color separation unit is also adjusted so that each color light separated by the color separation unit is guided onto the corresponding line sensor surface. Necessary independently.
For this reason, the cost is increased due to the increase in the number of parts and the adjustment work, and the entire apparatus is complicated and large.

A first object of the present invention is to integrally form the image forming optical system and the color separation means and to appropriately set the respective elements constituting the apparatus so that the color separation means is not adjusted. Can also guide each color light separated by the color separation means onto the corresponding line sensor surface without shifting, thereby reducing the number of parts and adjustment work, and simplifying and miniaturizing the entire apparatus. Another object of the present invention is to provide a color image reading device capable of performing the above-described operations.

The second object of the present invention is the same as the first object, except that the correction means provided in the optical path causes a difference in the wavelength of each color light (diffracted light) separated by the color separation means. By correcting the deviation of the image position by using the difference in the refractive index due to the difference in the wavelength, it is possible to make the interval between a plurality of color lights separated in the sub-scanning direction on the light receiving means surface equal. An image reading device is provided.

[0023]

According to the present invention, there is provided a color image reading apparatus comprising: (1-1) a plurality of lines through a color separating means for separating an incident light beam into a plurality of color lights by an image forming optical system; A color image reading device that forms a sensor on a light receiving means surface arranged on the same substrate surface, scans the color image and the light receiving means relatively in the sub-scanning direction, and reads the color image with the light receiving means X: distance from the color separation means to the light receiving means n: line spacing of the light receiving means / size of a single element of the light receiving means in the sub-scanning direction f: focal length of the imaging optical system β: imaging of the imaging optical system Magnification α: Variation of focal length of imaging optical system (%) k: Distance from positive surface of imaging optical system to principal point on image side (positive value): n · f (1−β) · Characterized by satisfying the condition of α / 100 <x <f (1−β) −k You.

In particular, (1-1-1) the above conditional expression is expressed as follows: 5 · n · f (1-β) · α / 100 <x <f (1-β)
-K, (1-1-2) the variation α of the focal length of the imaging optical system was set to 0.5% or less, and (1-1-3) the color separation means A one-dimensional blazed diffraction grating, which separates the incident light beam into three color lights in a direction orthogonal to the arrangement of the pixels of the line sensor; and (1-1-4) the imaging optical system and the color The disassembly means is attached to the same frame, and (1-1-5) the light receiving means comprises a monolithic three-line sensor.

(1-2) A plurality of line sensors are arranged on the same substrate surface through a color separation means comprising a one-dimensional blazed diffraction grating for separating an incident light beam into a plurality of color lights by an image forming optical system. An image is formed on the surface of the light receiving means disposed, and the color image and the light receiving means are relatively scanned in the sub-scanning direction, and the color image is read by the light receiving means. Correction means is provided for correcting the deviation of the imaging position on the light receiving means surface caused by the difference in the wavelength of each color light color-separated by the separation means, and the correction means utilizes the difference in the refractive index due to the difference in wavelength. The optical path of each color light is changed so that the intervals between a plurality of color lights separated in the sub-scanning direction on the light receiving means surface are made equal; x; the distance from the color separating means to the light receiving means n; Line spacing of light receiving means / The size of the single element of the optical means in the sub-scanning direction f; the focal length of the imaging optical system β; the imaging magnification of the imaging optical system α; the variation in the focal length of the imaging optical system (%) k; When the distance from the final surface of the system to the image-side principal point (positive value) is satisfied, the following condition is satisfied: n · f (1-β) · α / 100 <x <f (1-β) -k It is characterized by.

In particular, (1-2-1) the above conditional expression is given by: 5 · n · f (1-β) · α / 100 <x <f (1-β)
-K, (1-2-2) the variation α of the focal length of the imaging optical system was set to 0.5% or less, and (1-2-3) the color separation means It consists of a transmission type one-dimensional blazed diffraction grating, separates an incident light beam into three color lights in a direction orthogonal to the arrangement of the pixels of the line sensor, and the correction means is made of flat glass. The one-dimensional blazed diffraction grating is integrally formed, and is arranged obliquely with respect to the optical axis of the imaging optical system.
4) The color separation means comprises a reflection type one-dimensional blazed diffraction grating, separates an incident light beam into three color lights in a direction orthogonal to the arrangement of the pixels of the line sensor, and the correction means comprises a prism. The prism and the one-dimensional blazed diffraction grating are integrally formed,
(1-2-5) that the imaging optical system and the color separation means are attached to the same frame, (1-2-6) that the light receiving means is a monolithic three-line sensor, And so on.

[0027]

(Embodiment 1) FIG. 1 is a sectional view (sub-scan sectional view) of a main portion of a first embodiment of the present invention in the sub-scanning direction.

In FIG. 1, reference numeral 1 denotes a document surface on which a color image is formed. 2 is an imaging optical system (imaging lens),
A light beam based on a color image is imaged on four surfaces of light receiving means (monolithic three-line sensor) via a transmission type one-dimensional blazed diffraction grating described later.

Reference numeral 21 denotes an optical member, which integrally comprises a transmission type one-dimensional blazed diffraction grating 3 as a color separating means and a flat glass 11 as a correcting means, and an optical axis of the image forming optical system 2. Are arranged at a predetermined angle with respect to.

The transmission type one-dimensional blazed diffraction grating 3 has a grating pitch P of 226.26 μm, and converts the incident light beam into predetermined color light, for example, R (red), G ( The light is decomposed into three primary colors, green (green) and blue (B), and transmitted and diffracted. In the present embodiment, -1
B-color light is obtained as the 5th-order diffracted light 5, R-color light is obtained as the 0th-order diffracted light 6, and G-color light is obtained as the + 1st-order diffracted light 7.

The flat glass 11 is made of S-TIH11 material (OH
ARA Co., Ltd.) and changes the optical path of each color light by utilizing the difference in the refractive index due to the difference in the wavelength of each color light to the deviation of the imaging position in the sub-scanning direction caused by the difference in the wavelength of the diffracted light. The intervals S ₁ and S _{2 of the} plurality of color lights separated in the sub-scanning direction on the surface of the light receiving means 4 are made equal to each other.

In the present embodiment, the above-described imaging optical system 2 and the optical member 11 are mounted on the same frame (barrel) 20.

The inclination angle θ of the optical member 21 with respect to the optical axis of the imaging optical system 2 is preferably set to 1 ° or more and 40 ° or less. The thickness d of the flat glass 11 is 1 mm.
It is better to set it to 25 mm or less. In the present embodiment, the angle θ of the optical member 21 is inclined to the optical axis of the imaging optical system 2 by θ = 8.44 °, and the thickness d of the flat glass 11 is set to d = 5.0 mm. ing.

Reference numeral 4 denotes a light receiving means, which is a so-called monolithic three-line sensor (hereinafter also referred to as "three-line sensor") in which three line sensors (CCD) 8, 9, and 10 are arranged on the same substrate surface so as to be parallel to each other. ), And each pixel is 8 μm × 8 μm and is separated by eight lines.

In this embodiment, a color image on the original surface 1 is line-scanned by a scanning means (not shown) such as a mirror, and a light beam (information light) from the color image is formed into an image forming optical system 2.
And then color-separated into three color lights (for example, R, G, B) via a transmission type one-dimensional blazed diffraction grating 3 and form respective color images on the corresponding line sensors 8, 9, and 10 respectively. I have an image. At this time, in the present embodiment, the diffracted light of each order that has been color-separated by the one-dimensional blazed diffraction grating 3 is transmitted through the flat glass 11, so that three color lights that are color-separated in the sub-scanning direction on the surface of the three-line sensor 4. Are corrected so that the intervals S ₁ and S ₂ are equal. The color image 1 and the three-line sensor 4 are relatively scanned in the sub-scanning direction, and the three-line sensor 4 digitally reads a color image based on each color light.

The transmission type one-dimensional blazed diffraction grating as the color separation means is disclosed in Applied Optics, Vol. 17, No. 15, pp. 2273-2279 (August 1, 1978). Meanwhile, the incident light beam incident on the transmission type diffraction grating is transmitted and diffracted, and is mainly separated into three directions.

This transmission type one-dimensional blazed diffraction grating 3
Is a light beam incident on the transmission type diffraction grating and diffracted by transmission.
The first-order diffracted light 5, the 0th-order diffracted light 6, and the + 1st-order diffracted light 7 are separated in three directions, and are imaged on the surface of the three-line sensor 4 as light beams of a focused spherical wave by the imaging optical system 2. In this embodiment, as described above, B color light is obtained by the -1st order diffracted light 5, R color light is obtained by the 0th order diffracted light 6, and G color light is obtained by the + 1st order diffracted light 7.

In FIG. 1, x is the distance from the position on the axis of the one-dimensional blazed diffraction grating 3 to the three-line sensor 4, and Δx is the deviation of the focal length of the imaging optical system 2 from the imaging plane. This is the amount of the variation.

In general, the imaging lens (imaging optical system) 2 has a focal length f which varies by several% due to the degree of curvature of a single lens and the degree of formation of a lens barrel.
Optical adjustment is required to shift the imaging lens 2 or 3 line sensor 4 in the optical axis direction so that the line sensor 4 coincides with the best imaging plane A. At this time, the three color lights 5, 6, 7 color-separated by the one-dimensional blazed diffraction grating 3 have a line interval S at a position A ′ shifted by Δx shown in FIG.
₁ ', S _2' for respectively imaged at, the one-dimensional blazed diffraction grating 3 is also by a predetermined amount shifted in the optical axis direction of the imaging lens 2, line spacing is not adjusted to be S _1, S ₂ I had to.

Therefore, in the present embodiment, x: the distance from the one-dimensional blazed diffraction grating 3 to the three-line sensor 4 n; the line interval of the three-line sensor 4 / the size of a single element of the three-line sensor 4 in the sub-scanning direction f ; Focal length of the imaging optical system 2 β; imaging magnification of the imaging optical system 2 α; variation in the focal length of the imaging optical system 2 (%) k; N · f (1−β) · α / 100 <x <f (1−β) −k (1) (Δx = f (1−β) · α / 100) is set so as to satisfy | S ₁ ′ −S ₁ | <L ₁ (where L ₁ is the size of _one CCD pixel), and the three-line sensor 4 is used as the optical axis. By shifting by a predetermined amount in the direction, the focus and the line interval are both satisfied.

If the above conditional expression (1) is not satisfied, the position where the color image is read by the three-line sensor 4 is shifted by one pixel or more on the original surface 1, and the read color image is greatly colored in the sub-scanning direction. Is not good.

[0042] Further, conditional expression (1), by setting 5 · n · f (1- β) · α / 100 <x < and f (1-β) -k ‥ (2), | S 1 '-S ₁ | <L ₂ (where L ₂ is the size of 1/5 pixel of the CCD), whereby higher-precision and higher-quality color images can be read.

In the present embodiment, the variation α in the focal length of the imaging optical system 2 is set to 0.5% or less in the conditional expressions (1) and (2).

Next, numerical examples of the present embodiment will be described.

X = 30.0 (mm) n = 8.0 f = 40.0 (mm) β = −0.18898 α = 0.5 (%) k = 13.3 (mm) This is a conditional expression. (1) and conditional expression (2) are satisfied.

As described above, in the present embodiment, the imaging optical system 2 and the color separation means 3 are integrally formed as described above, and the respective elements are so set as to satisfy the conditional expression (1) or the conditional expression (2). By appropriate setting, each color light separated by the color separation means 3 can be guided without being shifted on the corresponding line sensor surface without adjusting the color separation means 3. Due to the flat glass 11 as a correcting means provided in the optical path between the light receiving means 3 and the light receiving means 4, the deviation of the imaging position caused by the difference in the wavelength of each color light (diffraction light) color-separated by the color separating means 3 is obtained. Is corrected using the difference in the refractive index due to the difference in wavelength, the intervals between a plurality of color lights that are color-separated in the sub-scanning direction on the surface of the light receiving means 4 can be made equal, thereby increasing the height. Read high-precision color images with high accuracy Going on.

In this embodiment, the transmission type one-dimensional blazed diffraction grating 3 and the flat glass 11 are integrally formed. However, the present invention is not limited to this, and they may be formed independently. In this case, the flat glass 11 may be arranged at a predetermined angle with respect to the optical axis of the imaging optical system 2.

(Embodiment 2) FIG. 2 shows Embodiment 2 of the present invention.
3 is a sectional view (sub-scan sectional view) of a main part in the sub-scan direction. In the figure, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

The present embodiment differs from the first embodiment in that a reflection type one-dimensional blazed diffraction grating is used as color separation means, a prism is used as correction means, and a reflection type one-dimensional blazed diffraction grating and a prism are used. Are integrally configured. Other configurations and optical functions are substantially the same as those of the first embodiment, and thus, similar effects are obtained.

That is, in the figure, reference numeral 22 denotes a reflection type one-dimensional blazed diffraction grating 13 and an S-TIH11 material (OHAR
This is an optical member integrally formed with a prism 12 made of a company A (trade name). In the present embodiment, the optical member 22
And the imaging optical system 2 are mounted on the same frame (barrel) 25 as in the first embodiment.

In this embodiment, the first embodiment is used.
In the same manner as described above, an optical member that obtains B-color light with the -1st-order diffracted light 5, R-color light with the 0th-order diffracted light 6, and G-color light with the + 1st-order diffracted light 7, and integrates the one-dimensional blazed diffraction grating 13 and the prism 12 22 is arranged in the optical path, the grating pitch P of the blazed diffraction grating 13 is P = 323.2 μm, and the angle θ of the prism surface 12 a on the exit side of the prism 12 with respect to the optical axis of the imaging optical system 2 is θ = It is configured to be tilted by 0.683 °. As a result, the deviation of the imaging position in the sub-scanning direction caused by the difference in the wavelength of the diffracted light is corrected.
The interval S between a plurality of color lights separated in the sub-scanning direction on the surface
_1, so as to the S ₂ equal intervals is performed a color image reading precision.

Further, in the present embodiment, similarly to the first embodiment, the imaging optical system 2 and the color separation means 13 are integrally formed, and the conditional expression (1) or the conditional expression (2) is satisfied. By setting each element, each color light separated by the color separation means 3 can be guided without shifting on the corresponding line sensor surface without adjusting the color separation means 3, thereby simplifying the operation. A three-line sensor 4 reads a color image with high accuracy.

Next, numerical examples of the present embodiment will be shown.

X = 26.0 (mm) n = 8.0 f = 40.0 (mm) β = −0.18898 α = 0.5 (%) k = 13.3 (mm) This is a conditional expression. (1) and conditional expression (2) are satisfied.

In this embodiment, the reflection type blazed diffraction grating 13 and the prism 12 are integrally formed. However, the present invention is not limited to this, and they may be formed independently.

In each of the above embodiments, a flat glass plate or a prism is used as the correction means. However, any optical element that can change the optical path of each color light using the difference in the refractive index due to the difference in wavelength is used. Even if it is used, the present invention can be applied similarly to the above-described embodiments.

[0057]

According to the first aspect of the present invention, the image forming optical system and the color separation means are integrally formed as described above, and the respective elements are set so as to satisfy the conditional expression (1) or (2). By appropriately setting, it is possible to guide each color light to be separated by the color separation unit without shifting on the corresponding line sensor surface without adjusting the color separation unit,
As a result, it is possible to achieve a color image reading apparatus capable of reducing the number of components and adjustment work, and simplifying and reducing the size of the entire apparatus.

According to the second aspect of the present invention, the first aspect of the present invention is achieved as described above, and the difference in the wavelength of each color light (diffracted light) color-separated by the color separation means by the correction means provided in the optical path. By correcting the deviation of the imaging position caused by the difference in the refractive index due to the difference in wavelength, the intervals between a plurality of color lights separated in the sub-scanning direction on the light receiving means surface are made equal. And a color image reading apparatus that can perform the above-described operations.

[Brief description of the drawings]

FIG. 1 is a sectional view of a sub-scanning direction according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view in the sub-scanning direction according to a second embodiment of the present invention.

FIG. 3 is a schematic view of a main part of an optical system of a conventional color image reading apparatus.

FIG. 4 is a schematic view of a main part of an optical system of a conventional color image reading apparatus.

FIG. 5 is an explanatory diagram of a monolithic three-line sensor.

FIG. 6 is a schematic view of a main part of an optical system of a conventional color image reading apparatus.

FIG. 7 is a schematic view of a main part of an optical system of a conventional color image reading apparatus.

FIG. 8 is an explanatory diagram showing the diffraction efficiency of each order of the blazed diffraction grating.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Original surface 2 Imaging optical system 3,13 Color separation means (one-dimensional blazed diffraction grating) 4 Light receiving means (monolithic three-line sensor) 5,6,7 Color light (diffraction light) 8,9,10 Line sensor 11,12 correcting means 21 and 22 the optical member 20, 25 frame member 12a prism surfaces S _1, S ₂ line spacing S ₁ ', S _2' line spacing

Claims (13)

[Claims] 1. A color image is formed on a light receiving means surface on which a plurality of line sensors are arranged on the same substrate surface via a color separating means for separating an incident light beam into a plurality of color lights by an image forming optical system. A color image reading apparatus for scanning the color image and the light receiving means relatively in the sub-scanning direction and reading the color image with the light receiving means; x; a distance from the color separation means to the light receiving means n; Line spacing / size of a single element of the light receiving means in the sub-scanning direction f; focal length of the imaging optical system β; imaging magnification of the imaging optical system α; variation in the focal length of the imaging optical system (%) k; When the distance (positive value) from the final surface of the imaging optical system to the image-side principal point is set, the condition of n · f (1-β) · α / 100 <x <f (1-β) -k is satisfied. A color image reading apparatus characterized by satisfying. 2. The conditional expression: 5 · n · f (1−β) · α / 100 <x <f (1−β)
2. The color image reading device according to claim 1, wherein -k is set. 3. A variation α in the focal length of the imaging optical system.
Is 0.5% or less.
Color image reading device. 4. The color separation means comprises a one-dimensional blazed diffraction grating, and separates an incident light beam into three color lights in a direction orthogonal to an arrangement of pixels of the line sensor. Color image reading device. 5. The color image reading apparatus according to claim 1, wherein said imaging optical system and said color separation means are mounted on a same frame. 6. A color image reading apparatus according to claim 1, wherein said light receiving means comprises a monolithic three-line sensor. 7. A light receiving device in which a plurality of line sensors are arranged on the same substrate surface through a color separating means comprising a one-dimensional blazed diffraction grating for separating an incident light beam into a plurality of color lights by a focusing optical system for a color image. A color image reading device which forms an image on a device surface, scans the color image and the light receiving unit relatively in the sub-scanning direction, and reads the color image with the light receiving unit; Correction means for correcting the deviation of the imaging position on the light receiving means surface caused by the difference in the wavelength of each color light, and the correction means changes the optical path of each color light using the difference in the refractive index due to the difference in wavelength. The intervals of the plurality of color lights separated in the sub-scanning direction on the surface of the light receiving means are made equal, and x: the distance from the color separating means to the light receiving means n; Light receiving means Element size in the sub-scanning direction f; Focal length of imaging optical system β; Magnification magnification of imaging optical system α; Variation of focal length of imaging optical system (%) k; Final surface of imaging optical system Where the distance from the image to the image-side principal point (positive value) satisfies the following condition: n · f (1−β) · α / 100 <x <f (1−β) −k Color image reading device. 8. The conditional expression: 5 · n · f (1−β) · α / 100 <x <f (1−β)
The color image reading device according to claim 7, wherein -k is set. 9. The variation α of the focal length of the imaging optical system
Is set to 0.5% or less.
Color image reading device. 10. The color separation means comprises a transmission type one-dimensional blazed diffraction grating, and separates an incident light beam into three color lights in a direction orthogonal to the arrangement of pixels of the line sensor. 8. The flat glass according to claim 7, wherein said flat glass and said one-dimensional blazed diffraction grating are integrally formed, and are arranged obliquely with respect to the optical axis of said imaging optical system. Color image reading device. 11. The color separation means comprises a reflection type one-dimensional blazed diffraction grating, and separates an incident light beam into three color lights in a direction orthogonal to the arrangement of the pixels of the line sensor. 8. The color image reading apparatus according to claim 7, comprising a prism, wherein said prism and said one-dimensional blazed diffraction grating are integrally formed. 12. The color image reading apparatus according to claim 7, wherein said imaging optical system and said color separation means are mounted on the same frame. 13. A color image reading apparatus according to claim 7, wherein said light receiving means comprises a monolithic three-line sensor.