JPH09307699A - Color image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the color image reader by which an image with a small color slurring is obtained without the use of an expensive optical system. SOLUTION: The color image reader that reads an image recorded on an original 1 as a color image by using a 2-line sensor 48 to receive RGB components of a reflected light 3 in the original 1 while scanning the original 1 in the main scanning direction and the subscanning direction by a slit light, is provided with a luminous flux separation optical element 44 which is placed on an optical path of the reflected light 3 before the reflected light 3 reaches the 3-line sensor 48 and have three faces directed in three different directions from each other and separates the luminous flux of the reflected light 3 into three sets of luminous flux 48a, 48b, 48c toward the 3-line CCD 48 by utilizing the different face directions.

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 device for reading an image recorded on a document as a color image.

[0002]

2. Description of the Related Art Conventionally, in a color image forming apparatus, a color separation optical system as shown in FIG. 11 is widely used as a color separation system for reading an image recorded on a document as a color image. FIG. 11 is a schematic diagram of a color separation optical system of a conventional color image reading device.

As shown in FIG. 11, in the color separation optical system of this system, while the original 1 is scanned by the slit light from the lamp 2 in the direction of arrow A, the reflected light 3 from the original 1 is formed by the imaging lens 4. A method of forming an image on the 3-line CCD sensor 5 is adopted. The 3-line CCD sensor 5 is normally R
It is formed by three line sensors 5a, 5b, 5c combined with a color filter of three colors of GB, and the reflected light formed into an image is read out as image information by these line sensors 5a, 5b, 5c. When the reading by one scanning is completed, the original 1 is scanned (sub-scanning) in the direction perpendicular to the 3-line CCD sensor 5 and the image information of the next line is read, so that the entire original can be read. There is.

By the way, the three line sensors 5a, 5
Since b and 5c are arranged at a constant interval G to secure the transfer path of the CCD, there is a slight delay in the time when the reflected light from the same portion of the document 1 reaches each line sensor. That is, the reflected light at a certain part of the document 1 scanned in the direction of arrow A in FIG.
There is a time delay corresponding to the interval G between the two line sensors between the time t0 at which the sensor array 5b arrives and the time t1 at the next sensor array 5b. Time t2 at which the last line sensor 5c is reached is further delayed than time t1. In order to correct these time delays, it is usual that the signals read from each line sensor are temporarily stored in a memory and the time delay for each color is corrected and taken out. Therefore, this method has a problem that a memory for time delay correction is required. Further, in this method, there is also a problem that a slight deviation in the scanning speed is caused due to mechanical backlash of the drive mechanism, which tends to cause a color shift.

Further, in the case of forming an image by enlarging or reducing the image at an arbitrary magnification, there arises a problem that the image quality deteriorates if the interval between the three-line sensors is not an integral multiple of one pixel in the sub-scanning direction. . As a countermeasure against this, a number of methods have heretofore been proposed in which a prism or a dichroic mirror is used to form an image of reflected light from the same spot on a document on three sensor arrays.

[0006]

Among these many methods, it is easy to apply to a color separation method using a three-line color sensor which is widely used in color copiers, and an optical element is arranged in the optical path. As a method that can achieve color separation without misalignment, (1) color separation using a spectral phenomenon by a prism or diffraction grating, and (2)
There is a method of separating the light flux into three by using multiple reflection and a half mirror and reading the light with a 3-line color sensor.

As an example of the color separation method utilizing the spectral phenomenon (1), as disclosed in Japanese Patent Application Laid-Open No. 3-42686, a method of disposing a prism in an optical path to generate a spectrum ( (See FIG. 12), as disclosed in Japanese Utility Model Application Laid-Open No. 5-200533, a method using a prism having a saw-tooth cross section (see FIG. 13), and Japanese Patent Laid-Open No. 3-23415.
As disclosed in Japanese Patent No. 9, there is a method using a diffraction grating (see FIG. 14).

FIG. 12 is a schematic diagram of a color separation system in which a prism is arranged in the optical path to generate a spectrum. As shown in FIG. 12, in this method, the surface of the original 1 has three types of fluorescent lamps 2a, 2b, 2 having different emission line spectra.
Reflected light 3 which is emitted by c and scanned on the original 1 in the direction of arrow A is dispersed by the prism 6, and the dispersed light is received by the three optical sensors 5a, 5b, 5c and read as image information. .

FIG. 13 is a schematic diagram of a color separation system in which a prism having a saw-tooth cross section is arranged in the optical path to generate a spectrum. As shown in FIG. 13, in this method, after the reflected light 3 from the original 1 is condensed by the imaging lens 4, the prism 7 having a saw-tooth cross section disperses the light, and the dispersed light is detected by the sensor 8.
The light is received by and is read as image information.

FIG. 14 is a schematic diagram of a color separation system in which a diffraction grating is arranged in the optical path to generate a spectrum. As shown in FIG. 14, in this method, the reflected light 3 from the original 1 is condensed by the imaging lens 4 and then dispersed by the diffraction grating 9,
The dispersed light is received by the sensor 8 and read as image information.

In the color separation method (1) utilizing these spectroscopic phenomena, each RGB light after being dispersed is not projected onto the light receiving surface at equal intervals, so that the layout of the three-line sensor array is considered. Inevitably, there are major restrictions, and it is therefore necessary to develop special sensors. In addition, since the pixels of a commercially available 3-line CCD sensor have almost the same vertical and horizontal dimensions, a normal light source such as a halogen lamp can use only energy in the vicinity of a part of RGB wavelengths in the visible light region. There is a problem in that the sensor output at the level required to obtain the / N ratio cannot be obtained. Therefore, in the method shown in FIG. 12, three types of fluorescent lamps 2a, 2 having bright lines near the RGB center wavelength are used as light sources.
It has been proposed to use b, 2c. However, in this case, since the light source is a bright line, a wavelength range that cannot be read occurs, which may impair the color reproducibility. Also,
There is also a problem that the operation tends to become unstable because the emission line spectrum changes due to the deterioration of the fluorescent lamp over time.

The method using a prism having a sawtooth-shaped cross section shown in FIG. 13 has the advantage of being more compact than the method shown in FIG. 12, but FIG. It is similar to the method shown. Also in the case of the method using the diffraction grating shown in FIG.
Since the projection position of each RGB light on the light receiving surface after being separated is also determined by the wavelength of each light, the same problem as in the case of the system shown in FIG. 12 occurs.

On the other hand, in (2), the luminous flux is divided into three and divided into three.
As an example of a method of reading with a line color sensor, there is a method of separating a light beam by utilizing surface reflection and multiple reflection, which is disclosed in JP-A-5-328024. FIG. 15 is a schematic diagram of a method of performing color separation by the above light beam separation. As shown in FIG. 15, in this light beam separation method,
The optical path 11 is divided into three light fluxes 11a, 11b, and 11c by using the glass plate 10 in which one surface 10a is a half mirror and the other surface 10b is a total reflection mirror, and the sensor 8b for each RGB color of the 3-line sensor 8 is separated. , 8g, 8r. Therefore, the distance between the three separated light beams 11a, 11b, and 11c can be controlled by changing the thickness of the glass plate 10 or changing the incident angle θ. There is an advantage that the sensor interval is not particularly limited. Also, regarding the restriction on color reproducibility, which was a problem in the spectroscopic method using a prism or a diffraction grating, since each luminous flux after separation includes light of all wavelengths, in this luminous flux separation method,
By selecting the wavelength of this using a color filter, it is possible to obtain the same color reproducibility as in the conventional 3-line CCD sensor system. However, when a non-telecentric optical system is adopted in this system, there is a problem in that the image information obtained at the end of the imaging lens shifts in color depending on the wavelength of light, resulting in color shift.

FIG. 16 is an explanatory diagram of a color shift that occurs when a non-telecentric optical system is used in the color separation system by light beam separation. As shown in FIG. 16, when a non-telecentric optical system is used, the green light has an end portion of the imaging lens 4 from the optical path length of the blue light passing through the end portion 4a of the imaging lens 4 to the image forming point 12b. Image point 12g through 4a
The length of the optical path leading to is longer. Red light image point 12r
The optical path length to reach is longer than that. Therefore, there arises a problem that the image forming positions Fb, Fg, and Fr of the CCD line sensors for the respective colors are deviated from the image forming positions G1 and G2, and the obtained image information is deviated in color. Therefore, in the above-mentioned Japanese Patent Laid-Open No. 5-328024, a telecentric optical system is adopted to avoid this problem. However, since the telecentric optical system is more expensive than a normal non-telecentric optical system, the adoption of the telecentric optical system leads to an increase in the cost of the color image reading device, which causes a new problem.

In view of the above circumstances, it is an object of the present invention to provide a color image reading apparatus capable of obtaining a color image with less color shift without using an expensive optical system.

[0016]

A color image reading apparatus of the present invention that achieves the above object scans an original in a predetermined longitudinal direction intersecting the width direction with slit light extending in the predetermined width direction. , Each predetermined wavelength region component of the reflected light carrying the information of the image recorded on the original reflected from the original is formed in parallel with each other on one substrate, and the longitudinal direction corresponds to the width direction in which the slit light extends. In the color image reading device for reading the image recorded on the document as a color image, the reflected light reaches the line sensor by receiving light by each of the three line sensors arranged so as to face each other. Facing three mutually different directions arranged on the optical path of the previous reflected light, the luminous flux of the reflected light is directed to each of the three line sensors by the different directions. Forming a function of separating the three light beams Cow, characterized by comprising a light beam separating optical element having a plurality of surfaces to be repeated at each predetermined pitch for at least two orientations.

Here, the light beam splitting optical element may be one that splits the reflected light into three light beams by refracting the reflected light in a direction corresponding to the directions of the plurality of surfaces.
Further, the light beam splitting optical element may be one that splits the reflected light into three light beams by reflecting the reflected light in a direction corresponding to the directions of the plurality of surfaces. Further, the light beam splitting optical element may have the plurality of surfaces formed by anisotropic etching or a replica thereof.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a schematic view showing an embodiment of a color image reading apparatus of the present invention. As shown in FIG. 1, the color image reading apparatus 100 includes a first reflection unit 20 that guides reflected light 3 from an original 1 to a second reflection unit 30 by reflecting the light 3 from a document 1, and a first reflection unit 20. The second reflection unit 30 that guides the reflected light 3 from the reflecting unit 20 twice to the image reading unit 40 internally, and the image information carried by the reflected light 3 that receives the reflected light 3 from the second reflecting unit 30 An image reading unit 40 for reading the image, a signal processing unit (not shown) for processing and outputting signals from the image reading unit 40, and a housing 50 for housing these units.

In the housing 50, a reading window 14 having a glass surface on which the original 1 is placed, an original pressing member 15 for bringing the original 1 placed on the reading window 14 into close contact with the reading window 14, and an original pressing member. A drive mechanism (not shown) for reciprocating the reading window 15 and the reading window 14 in the direction of the arrow Sa is provided. In this embodiment, the direction of the arrow Sa is called the longitudinal direction of the document 1, the direction orthogonal to the direction of the arrow Sa is called the width direction of the document 1, and the scanning of the document 1 in the width direction is the main scan, the document 1 Scanning in the longitudinal direction of is called sub-scanning.

Next, the function of each unit and each device shown in FIG. 1 will be described. The reading window 14 installed on the upper part of the housing 50 is a transparent plate made of, for example, glass and is installed horizontally. Reading window 14
The original 1 is placed upside down so that the image information to be read can be clearly taken out, and the original surface of the original 1 is brought into close contact with the reading window 14 by the original holder 15. The document retainer 15 and the reading window 14 are configured to be reciprocally movable on the housing 50 in the sub-scanning direction Sa by a drive mechanism (not shown).

A first reflection unit 20 is installed in the housing 50 below the reading window 14. The first reflection unit 20 includes a lamp 24 that illuminates the original 1 that is in close contact with the reading window 14, and a concave reflection plate 26 that converges the light from the lamp 24 so that the light efficiently illuminates the original surface.
Illumination-side slit 29 that narrows down the illumination light in order to prevent the occurrence of ghost (a phenomenon in which light beams separated are multiply imaged) on the sensor, and reflected light 3 from document 1 is slit light that extends in the main scanning direction. Entrance side slit 2
7, a first reflection mirror 22 for guiding the reflected light 3 that has passed through the incident side slit 27 to the second reflection unit 30, and a light shielding for shielding the light source rays from the lamp 24 from directly entering the first reflection mirror 22. A plate 28 is provided.

Each component in the first reflection unit 20, that is, the lamp 24, the concave reflection plate 26, the illumination side slit 29, the incident side slit 27, the light shielding plate 28, and the first reflection mirror 22 are the original document 1 The width of the surface, that is, the width in the main scanning direction, is the same as the width in the main scanning direction. Thus, the entire original surface of the original 1 can be scanned.

The second reflecting unit 30 reflects the reflected light 3 from the first reflecting unit 20 and the image reading unit 40.
The second reflection mirror 32 and the third reflection mirror 34 that lead to Here, the second reflecting mirror 32 is arranged in parallel with the first reflecting mirror 22, and the third reflecting mirror 34 is arranged in a direction orthogonal to the first reflecting mirror 22 and the second reflecting mirror 32. .

Each component in the second reflection unit 30, that is, the second reflection mirror 32 and the third reflection mirror 34 also has the same width as the original surface of the original 1, that is, the width in the main scanning direction. The reflected light 3 emitted from the third reflecting mirror 34 toward the image reading unit 40 is introduced into the image reading unit 40 as slit light having the same width as that of the illumination side slit 29 and the incident side slit 27.

The image reading unit 40 includes an imaging lens unit 42 composed of a plurality of lenses, a light beam separating optical element 44 having a light beam separating function, and three CCD line sensors 48a, 48b and 48c. A sensor 48 is provided. The reflected light 3 emitted from the second reflection unit 30 is imaged by the imaging lens unit 42 and is incident on the light beam splitting optical element 44. The light beam splitting optical element 44 splits the incident light beam into three light beams corresponding to the three colors of R, G, and B. The three light beams separated by the light beam separation optical element 44 are guided to the three-line sensor 48. The 3-line sensor 48 is composed of three CCD line sensors 48a, 48b, 48c which are formed parallel to each other on one substrate and are arranged so that their longitudinal directions correspond to the width direction in which the slit light extends. Has been done. These three CCD line sensors 48a, 48b, 48c
Is configured to cover three wavelength range components corresponding to RGB selected from the wavelength range of the reflected light 3.

The three RGB light fluxes are converted into electric signals by the three CCD line sensors 48a, 48b, 48c, and subjected to predetermined processing by a signal processing unit (not shown), and then an external image forming apparatus (not shown) or It is output to a storage device or the like. FIG. 2 is a schematic view of an optical system around the light beam splitting optical element used in this embodiment.

This optical system, as shown in FIG.
The imaging lens 4 (corresponding to the imaging lens unit 42 in FIG. 1) that forms an image of the reflected light 3 from
A light beam splitting optical element 44 that splits the light beam into three light beams, and a light beam receiving optical signal that receives each of the three split light beams and converts the light beams into an electrical signal
And a line sensor 48. FIG. 3 is a cross-sectional view of the light beam splitting optical element used in this embodiment.

As shown in FIG. 3, the light beam splitting optical element 44.
Are three different directions A, corresponding to RGB three colors.
Consists of a base 45 formed of a transparent plate having three types of surfaces 45a, 45b, 45c facing B and C and repeating at a constant pitch in each direction, and a dielectric film 46 covering the base 45. Has been done. The first surface 45a of the substrate 45 forms an angle θ1 (5
Direction (A) (4.7 °), and the second surface 45b forms a direction B (angle −θ1 (−54.7 °)) with respect to the luminous flux 47 of the incident light.
The third surface 45c faces the direction C at an angle of 0 ° with respect to the luminous flux 47 of the incident light. Then, three types of surfaces 45a, 45b, 4 facing these three directions A, B, C
5c are arranged so as to repeat at a constant pitch in each direction. The three types of surfaces 45a, 45b, 45c have different directions, so that the light flux 47 of the light incident on the light flux separating optical element 44 is transferred to the three CCD line sensors 48a, 48b ,.
48c (see FIG. 1) three light fluxes 47 respectively directed
It acts to separate into a, 47b and 47c. The light beam splitting optical element 44 is formed with a width corresponding to the above-described main scanning width in the direction perpendicular to the drawing while maintaining the sectional shape shown in FIG.

Here, the refractive index of the dielectric film 46 is n1, the refractive index of the substrate 45 is n2, and the angle of incidence on the first surface 45a is θ.
1, assuming that the refraction angle is θ2 and the exit angle is θ3, from the Snell equation, sin θ1 / sin θ2 = n2 / n1 sin θ3 / sin (θ1 −θ2) = n2 θ3 = sin ⁻¹ (n2 · (sin θ1 · cos θ2 −c
os θ1 · sin θ2)).

Here, if θ1 = cos ⁻¹ (1 / √3) = 54.7 °, θ3 = sin ⁻¹ (n2 · (√ (2/3) · cos θ2 −
√ (1/3) · sin θ2)) = sin ⁻¹ (n2 · (√
2/3) ・ √ (1-sin ² θ2) -√ (1/3) ・ s
in θ2)) = sin ⁻¹ (n2 · √ (2/3) · √ (1
-2/3 ・ (n1 / n2) ² ) -√ (1/3) ・ √ (2
/ 3) · n1 / n2)).

Here, for example, when n2 = 1.7 and n1 = 1.6, θ3 = 7.7 °, and when n2 = 1.7 and n1 = 1 (air), θ3 = 48. ．
It becomes 3 °.

Here, the optical path length difference that is important in optical design is evaluated from the lengths of the line segments of the g line and the b line in FIG. Now, ignoring the optical path length difference in the light beam splitting optical element 44, the distance from the light beam splitting optical element 44 to the image plane of the CCD sensor is set to L, and the light emitted from the light beam splitting optical element 44 is la.
When the difference .DELTA.L between the optical path length of the line and the optical path length of the perpendicular line lc is obtained, .DELTA.L = L.times. (1-cos .theta.3) For example, L = 2 mm, n2 = 1.7, n1 = 1.6.
When the value of .theta.3 = 7.7.degree. Is used, .DELTA.L = 18.0 .mu.m, and the difference in optical path length on the image plane hardly poses a problem. This can be said to be a major feature of the method of separating the light flux by changing the emission angle from the light flux separation optical element 44 into three ways as in the present embodiment.

Next, a method of manufacturing the light beam splitting optical element will be described. When manufacturing the light beam splitting optical element of the present embodiment, a technique for accurately controlling the emission angle is particularly important. Anisotropic etching is a technique suitable for this.
The anisotropic etching utilizes the fact that the etching rate of a semiconductor depends on the crystal orientation of the semiconductor. In the case of a silicon crystal, the etching rate of the (100) orientation is much higher than that of the (111) orientation. By utilizing the fact that it is extremely fast, it is possible to realize an optical element having a highly accurate three-dimensional structure composed of the (111) plane and the (100) plane.

As the etching solution for anisotropic etching, for example, an alkaline aqueous solution such as an aqueous potassium hydroxide solution or ethylenediaminepyrocatechol can be used. As the etching mask, a silicon nitride film (Si ₃ N ₄ film) or a silicon oxide film (SiO ₂ film)
Etc. can be used. FIG. 4 is a manufacturing process diagram of the light beam splitting optical element of the present embodiment.

4 (a) and 4 (c) are top views in the process of manufacturing the light beam splitting optical element, and FIGS. 4 (b) and 4 (d) are FIGS. 4 (a) and 4 (a), respectively. Figure 4 (c)
FIG. 4 is a cross-sectional view seen in the direction of arrow AA ′ in FIG. As shown in FIGS. 4 (a) and 4 (b), a silicon substrate 61 having a (100) surface has a thickness of 15 as an etching mask.
After forming a 0 nm Si ₃ N ₄ film, the Si ₃ N ₄ film is patterned by a photolithography process and a dry etching process to form an opening 63 having a width W 1. Opening 6
An etching mask portion 62 having a width W2 is provided between the three. Next, this silicon substrate 61 is anisotropically etched using a heated potassium hydroxide aqueous solution as an etching solution. Thus, as shown in FIGS. 4C and 4D, the groove 64 having a V-shaped cross section formed by the four (111) planes is formed.

Finally, the silicon substrate 6 is heated with phosphoric acid.
The Si ₃ N ₄ film on 1 is removed, and a replica mold is completed. Furthermore, a replica is created using this mold. FIG.
FIG. 6 is an explanatory diagram of a replica for manufacturing the light beam splitting optical element of the present embodiment. As shown in FIG. 5A, the replica 60 has a plurality of V-shaped grooves 64 formed of two (111) planes.

Since the refractive index of the substrate of the light beam splitting optical element of this embodiment is 1.7 as described above, when glass is used as the material of the replica, heavy flint, barium flint, lanthanum crown or the like is used. be able to. On this replica 60, as shown in FIG.
The light beam splitting optical element 44 is completed by pouring the plastic 65. As the plastic 65 to be poured, since the refractive index of the dielectric film of the light beam splitting optical element of this embodiment is 1.6, methylmethacrylate or the like is suitable as the material of the dielectric film. The thickness of the plastic 65 is the same as the plastic 6 on the replica 60.
It is preferable that the thickness is at least equal to or larger than the above-mentioned repeated pitch W1 + W2 so that the surface is smoothed by the surface tension of the plastic 65 when the resin 5 is poured. If there is a problem with the flatness of the plastic 65 surface,
Alternatively, if it is desired to further reduce the thickness of the plastic 65, the surface of the plastic 65 may be polished.

As described above, by appropriately combining the refractive indexes of the two kinds of materials, the replica material and the plastic material, it is possible to control the emission angle θ 3 (see FIG. 3) from the light beam splitting optical element. The above-mentioned anisotropic etching is suitable for accurately controlling the emission angle, but the angle obtained by anisotropic etching depends on the crystal structure of the material used, so the refraction angle is too large for a single material, The optical path length difference also becomes large. However, in the case of a composite material composed of two kinds of materials, the exit angle can be controlled very easily by appropriately combining the refractive indexes of the two materials.

Further, if the mold of the substrate of the light beam splitting optical element is first produced as in the present embodiment, the CC material can be changed by changing the replica material and the plastic material.
It is possible to manufacture a 3-line sensor in which the distance between the D sensors is set to various intervals. In this embodiment, the Si ₃ N ₄ film is used as the etching mask.
The etching mask is not limited to the Si ₃ N ₄ film, and may be any one having resistance to the etching liquid such as a silicon oxide film (SiO ₂ film). The etching solution is not limited to the potassium hydroxide aqueous solution, and any other etching solution may be used as long as it is an anisotropic etching solution similar to the potassium hydroxide aqueous solution.

By the way, regarding the specific dimensions of the light beam splitting optical element, assuming that the width W1 of the opening 63 in FIG. 4 is 10 .mu.m and the distance W2 between the adjacent openings 63 is 10 .mu.m, the V-shaped groove 64 after completion is formed. The depth D is 7.1 μm.
Here, W1 + W2 corresponds to the above-mentioned repetition pitch, but when W1 + W2 is reduced to about 1 μm, diffraction in the visible light region is increased, and conversely, W1
If 1 + W2 increases to a length close to the viewing angle on the beam splitting optical element, the optical performance deteriorates.
It is necessary to determine the dimensions of W1 and W2 in consideration of these balances. The ratio of W1 and W2 can be determined from the sensitivity of the CCD sensor as follows.

FIG. 6 is an explanatory view of the dimensions of the light beam splitting optical element of this embodiment. For example, considering the sensitivity difference between RGB of a three-line sensor when a document is illuminated with a halogen lamp, the sensitivity difference between RGB is R: G: B =
There is a large sensitivity difference such as 2: 3: 1, and the sensitivity ratio reaches up to 3 times. Therefore, a wide dynamic range is required in the subsequent signal processing stage.

Therefore, the CC with the blue sensor having the lowest sensitivity is arranged in the center of the three-line sensor.
As shown in FIG. 6, an etching mask portion 62 is used in accordance with the CCD line sensor using the D line sensor.
The width W2 (see FIG. 4) is made equal to the width W1 of the opening 63, and the surface 61a of the base 61 corresponding to the width W2 portion is used as a blue region, and the base 61 corresponding to the width W1 portion is formed.
The inclined surface 61b of the base body 61 corresponding to the width W1 is defined as the green area.
c is used as the area for red. That is, the area for blue light is made twice as large as the area for green light and red light. By doing so, assuming that the amount of light received by the entire sensor is 1, the amount of light to each of the RGB CCD line sensors is R: 1/4 B: 1/2 G: 1/4.

In addition, the above-mentioned sensitivity ratio R: G: B = 2:
When multiplied by 3: 1, R: G: B = 2/4: 3/3: 1/2 = 1/2: 1: 1
/ 2 = 1: 2: 1, and the sensitivity ratio can be suppressed to a maximum of 2 times. Strictly speaking, since the reflectance and the transmittance at the dielectric film interface depend on the refraction angle, this sensitivity ratio does not actually hold as it is, but it is understood that it is considerably effective as a mere guide.

Next, another embodiment of the color image reading apparatus of the present invention will be described. FIG. 7 is a schematic diagram showing a second embodiment of the color image reading device of the present invention. Figure 7
As shown in FIG. 3, in this embodiment, after the reflected light 3 from the original 1 is condensed by the imaging lens 4, the three reflected mirror surfaces (described later) on the surface of the reflection mirror type light beam splitting optical element 70 are temporarily provided. Is reflected by the laser beam and is separated into three light beams (described later) to form an image on the 3-line sensor 48. Various specific examples of the reflection mirror type light beam splitting optical element 70 will be described below.

FIG. 8 is a schematic view showing a specific example of the light beam splitting optical element of the second embodiment. As shown in FIG. 8A, three reflection mirror surfaces 71a, 71b, 71c are formed on the surface of the light beam splitting optical element 70. The light incident on the light beam splitting optical element 70 is reflected by these reflection mirror surfaces, split into three light beams 72a, 72b, 72c, and then emitted to a three-line sensor. FIG.
FIG. 8B shows the three reflection mirror surfaces 71 in FIG.
This is a modified example in which only the arrangement order of a, 71b, and 71c is changed.

FIG. 9 is a schematic view showing another specific example of the light beam splitting optical element of the second embodiment. As shown in FIG. 9, the light beam splitting optical element 70 'is composed of two half mirrors 73 and 74 combined in a laminated shape. Sawtooth-shaped semitransparent mirror surfaces 73a and 74b are formed on the surface of the first half mirror 73 and the surface of the second half mirror 74, respectively. The light that has entered the light beam splitting optical element 70 'is reflected by the two semitransparent mirror surfaces 73a and 74b and the bottom surface 74c of the second half mirror 74, and after being split into three light beams 75a, 75b and 75c. It is emitted to the 3-line sensor.

FIG. 10 is a schematic diagram showing still another specific example of the light beam splitting optical element of the second embodiment. As shown in FIG. 10, the light beam splitting optical element 70 ″ includes two dichroic mirrors 76 and 77 which are combined in a laminated shape.
Consists of On the surface of the first dichroic mirror 76, for example, a semitransparent mirror surface 76a that reflects only blue light and transmits green light and red light is formed, and on the surface of the second dichroic mirror 77, for example, only red light is formed. A semi-transparent mirror surface 77c that reflects and transmits green light is formed, and a reflective surface 77b that reflects green light is formed on the bottom surface of the second dichroic mirror 77. The incident light is 3
The light beams 78a, 78b, and 78c of the book are separated and emitted to the 3-line CCD sensor. As described above, by using the dichroic mirror for the light beam separating optical element, the color filter on the sensor is unnecessary, the cost of the apparatus is reduced, and the decrease in the light amount due to the color filter is eliminated. Increase S / N
The ratio can be improved.

In each of the above embodiments, only the case of reading the reflected light from the original has been described.
The color image reading apparatus of the present invention is not limited to the case of reading the reflected light from the original document, but can be applied to the case of reading the light transmitted through the original document. Further, in each of the above embodiments, the CC is used as the optical sensor.
Although only the example of the D line sensor has been described, the optical sensor of the color image reading apparatus of the present invention is not limited to the CCD line sensor, and other optical sensors such as a MOS sensor may be used.

[0049]

As described above, according to the color image reading apparatus of the present invention, each color has a plurality of surfaces facing in three different directions, and the reflected light from the original document is divided into three light fluxes. By providing a light beam separating optical element for separating, color misregistration of an image caused by reading image information of each color at different positions is optically prevented, and a color image reading capable of obtaining an image with little color misregistration The device can be obtained.

Further, in the color image reading apparatus of the present invention,
Since it is possible to simultaneously read three images of the same place on the original, it is possible to omit the memory required for line-to-line correction and the correction process associated with the image reduction / enlargement process, which have been conventionally required. Furthermore, an ordinary inexpensive optical system can be used without using an expensive optical system such as a telecentric optical system.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a color image reading device of the present invention.

FIG. 2 is a schematic diagram of an optical system around a light beam separation optical element used in this embodiment.

FIG. 3 is a cross-sectional view of a light beam splitting optical element used in this embodiment.

FIG. 4 is a manufacturing process diagram of the light beam splitting optical element of the present embodiment.

FIG. 5 is an explanatory diagram of a replica for manufacturing the light beam splitting optical element of the present embodiment.

FIG. 6 is an explanatory diagram of dimensions of the light beam splitting optical element of the present embodiment.

FIG. 7 is a schematic view showing a second embodiment of the color image reading device of the present invention.

FIG. 8 is a schematic view showing a specific example of the light beam splitting optical element of the second embodiment.

FIG. 9 is a schematic view showing another specific example of the light beam splitting optical element of the second embodiment.

FIG. 10 is a schematic diagram showing still another specific example of the light beam splitting optical element of the second embodiment.

FIG. 11 is a schematic diagram of a color separation optical system of a conventional color image reading device.

FIG. 12 is a schematic diagram of a color separation system in which a prism is arranged in an optical path to generate a spectrum.

FIG. 13 is a schematic diagram of a color separation system in which a prism having a saw-tooth cross section is arranged in the optical path to generate a spectrum.

FIG. 14 is a schematic diagram of a color separation system in which a diffraction grating is arranged in an optical path to generate a spectrum.

FIG. 15 is a schematic diagram of a method of performing color separation by light beam separation.

FIG. 16 is an explanatory diagram of color misregistration that occurs when a non-telecentric optical system is used in a color separation method using light beam separation.

[Explanation of symbols]

 1 Original 3 Reflected Light 40 Image Reading Unit 42 Imaging Lens Unit 44 Luminous Flux Separation Optical Element 45 Substrate 45a, 45b, 45c Surface 46 Dielectric Film 47, 47a, 47b, 47c Luminous Flux 48 3 Line Sensor 48a, 48b, 48c CCD Line Sensors 70, 70 ', 70 "Light flux separation optical elements 71a, 71b, 71c Reflection mirror surfaces 72a, 72b, 72c Light fluxes 73, 74 Half mirrors 73a, 74b Semi-transparent mirror surface 74c Bottom surface 76, 77 Dichroic mirrors 76a, 77c Semi-transparent mirror surface 77b Reflective surface 78a, 78b, 78c Luminous flux

Claims (4)

[Claims] 1. A document is carried by a slit light beam extending in a predetermined width direction in a predetermined longitudinal direction intersecting with the width direction while carrying information of an image recorded on the document reflected from the document. Three line sensors, each of which has a predetermined wavelength region component of reflected light and is formed in parallel with each other on one substrate and arranged such that the longitudinal direction thereof corresponds to the width direction in which the slit light extends. In the color image reading device for reading the image recorded on the original document as a color image by receiving the light, the three different light beams are arranged on the optical path of the reflected light before the reflected light reaches the line sensor. Facing in one direction,
A light beam splitting optical having a plurality of surfaces which repeat at a predetermined pitch in at least two directions, and which has a function of separating the light beam of the reflected light into three light beams directed to each of the three line sensors by different directions. A color image reading device comprising an element. 2. The light beam splitting optical element splits the reflected light into three light beams by refracting the reflected light in a direction corresponding to the directions of the plurality of surfaces. The described color image reading device. 3. The light beam splitting optical element splits the reflected light into three light beams by reflecting the reflected light in a direction corresponding to the directions of the plurality of surfaces. The described color image reading device. 4. The color image reading apparatus according to claim 1, wherein the light beam splitting optical element has the plurality of surfaces formed by anisotropic etching or a replica thereof.