JPS6047560A - Color image reading optical device - Google Patents

Abstract

PURPOSE:To read an image at a high speed without decreasing the quantity of light nor causing any position shift by guiding reflected light from an original surface to a photodetection sensor through plural lenses which are arranged successively and a color separation filter which is provided corresponding to the each lens, and projecting and forming an image of the overall slit length of an original surface. CONSTITUTION:The lenses 61, 62, and 63 are arrayed on the same plane in the optical paths from the mirrors 3, 4, and 5 in the lengthwise direction of the slit, the separation filters 71, 72, and 73 which differ in color from one another are arranged behind the lenses, and the photodetection sensors 81, 82, and 83 such as CCD are provided on image-formation positions in the optical paths from the filters. In this constitution, slit light of the overall width W of the original O is incident to the respective lenses 61, 62, and 63 and separated by the color separation filters 71, 72, and 73 into light components differing in color, and the sensors 81, 82, and 83 obtain respective pieces of color information on the overall width W of the original.

Description

Detailed Description of the Invention Technical Field The present invention relates to a color image reading device that reads a color image by combining a color separation filter and a light receiving sensor such as a CCD. It relates to a reading device.

Conventional technology A device that separates a color image into two or more colors and reads them with a light receiving sensor such as a COD uses, for example, three prisms whose contact surfaces are each a color filter such as a guichroic mirror, which are brought into surface contact with each other. The light emitted from one lens is made incident on one surface of the formed three-color separation optical system, and two beams of light reflected at the contact surface between each prism and one beam of light transmitted are formed on the imaging plane, respectively. A device equipped with a light receiving sensor is used.

However, in this configuration, two of the three light fluxes pass through the color filter twice, so the amount of light reaching the light receiving sensor is reduced to 1/4, and three prisms are installed behind the lens. JP-A-54-154348, which features a special lens that has a long back focus and prevents image deterioration caused by the prism, has improved the above drawbacks. In order to do this, a trapezoidal prism is installed in front of one lens, and color filters are installed on the three incident surfaces of the trapezoidal prism, and the three light beams emitted from the document are separated into three different colors, and then the three light beams are separated into three different colors. A device has been proposed that simplifies the drive circuit by transmitting the light through a lens and focusing the images on three line sensors fabricated on the same substrate, but in this case, the three light beams are Since different parts of the two lenses are used to form an image, the light intensity is reduced to approximately 1/3, and since three line sensors are made on the same substrate, manufacturing is difficult, yields are low, and costs increase. have

In addition, Japanese Patent Publication No. 57-46266 discloses that although it is not a color image reading device, a slit light beam from an original is divided into two optical paths by two plane mirrors that intersect at a slight angle, and a single lens is used to divide the beam into two optical paths. An apparatus is shown in which images are formed on short light-receiving sensors arranged in a staggered manner, and the entire width of the document is scanned and read by itself. However, in actual design, in order to prevent the two rows of sensors from overlapping, it becomes necessary to either increase the splitting angle of the optical path or use a lens with a long focal length, which increases the size of the mirror and increases the overall device size. This causes inconveniences such as an increase in size.

When reading high-speed color originals with high image quality, considering recent trends, the number of bits read by sensors is increasing, and devices with 3,000 to 4,000 pits have appeared, and short sensors are arranged in a staggered manner as described above. Although it is no longer necessary to connect the bit pitch into smaller bits, the bit pitch is becoming smaller, and the pitch is currently 7 to 8 microns. This makes lens design extremely difficult, and further increases the requirements for the lens, such as the need for a bright lens to increase speed.

Purpose: In view of the above-mentioned current situation, the present invention has been developed to prevent a color family document placed on a contact glass from decreasing in light intensity and causing unevenness in light intensity.
It is an object of the present invention to provide a compact color image reading optical device capable of reading high-quality images at high speed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail based on embodiments shown in the drawings. In the embodiment shown in FIG. 1, a document 0 is placed on a flat contact glass l provided on the top surface of the apparatus, and is illuminated by a white light source 2 such as a white fluorescent light. Manuscript O
The slit is scanned by a first traveling mirror 3 that moves at a constant speed in the direction of the arrow along with the light source lamp 2, and a second traveling mirror group 4 and 5 that moves synchronously in the same direction at a speed of 1/2 of the first traveling mirror 3. Ru.

Fig. 2 is a developed view of the optical path when Fig. 1 is viewed in direction B, and there are three lenses 6 (61
, 62, 63) are arranged in a row parallel to the longitudinal direction of the slit on the same plane, and color separation filters 7 (71, 72, 73) of different colors are arranged after each lens. A light receiving sensor 8 (81, 82, 83) such as a COD is provided at the imaging position of each optical path that has passed through.

Since this device is configured as described above, each lens,
Slit light having the full width W of the document 0 is incident on 61, 62, and 63, respectively, and is separated into different colors by color separation filters 71, 72, and 73, and sent to each light receiving sensor 81, 82, and 83.
Accordingly, each color information of the entire width W of the document can be read.

The configuration of this embodiment eliminates errors in the position and scanning movement between the lamp 2 and the first optical path, reduces the number of parts, helps in cost reduction, and has the effect of reducing the space in the height direction in particular.

In FIG. 2, it is desirable that the distance P between the lenses 61, 62, and 63 is as small as possible.

The reason is as follows. Regarding the center lens 62, the angle of view on both sides is the same at θ3, but the angle of view on both sides is θ3.
Regarding No. 3, the angles of view θ1 and θ2 on both sides of the lens optical axis Q are different. This difference also affects the performance of the lens in use, but the biggest influence is the difference in illuminance at the imaging plane, where the amount of light decreases at the periphery of the image where the angle of view is large due to the so-called cosine fourth power law. It is. 1 lens
In a black-and-white image reading device that uses three lenses and produces equal images on both sides of the optical axis, a light amount correction means can be provided near the lamp. Such correction means cannot be adopted when the angles are different. Although it has been proposed to provide a peripheral illumination difference correcting device for each lens in the vicinity thereof, the effect is not good even though the installation requires high precision. An effective method for correcting this is called dynamic shading, which electrically corrects the output of the light receiving sensor, but it is expensive. Therefore, it is desirable to make the lens interval P as small as possible in order to make the difference between θ and θ2 as small as possible. However, when the lenses are arranged in a straight line, the lens interval P is actually determined by the length t of the sensors 81, 82, and 83, and it is necessary that t<P.

Figure 3 shows an example of a color image reading optical system using three lenses and a light receiving sensor provided corresponding to each lens, with a lens arrangement that can reduce the difference in angle of view on both sides of each lens. It is. FIG. 4 shows a view of the lens and sensor seen in direction C in FIG. 3. In these figures, the same members as in FIGS. 1 and 2 are designated by the same reference numerals and will be explained. 3
The lenses 61, 62, and 63 are not arranged in one row, but in two rows above and below parallel to the slit, and in a staggered manner, that is, two in the lower row.
lenses 62, 63 are arranged at intervals of P, and in the upper row, the lens 61 is arranged between the lenses 6263 in the lower example, each sensor 81, 82, 83 each filter 71, 72 .
73 is provided corresponding to each lens. In addition, the fifth
As shown in the figure, two lenses 62 and 63 are placed in the upper row.
One lens 61 may be provided on the lower side. As a result, as shown in FIG. 6, the distance between the lenses on both sides can be set to P, and the angles of view 'L+ and θ1. This makes it possible to make the difference smaller than that in the embodiment shown in FIG.

In FIG. 4, a difference in the angle of view is caused by the lens distance P2 in the vertical direction, but P2':P/2, and its influence is small. Further, since it is in the slit lateral direction (that is, the sub-scanning direction), the influence on light amount correction is small.

In the embodiment shown in FIG. 3, the second traveling mirrors 4 and 5 need to be larger than those in FIG. 1, and as a result, the height of the entire device becomes slightly larger.

In addition, the results of calculating the difference in the angle of view on both sides of the optical axes of the lenses on both sides in Figures 3 and 6 using actual examples show that the length t of Serena is 40 to 45 mW in most cases, so P-5.
0, document width W = 256 □ object distance a - 400 □, y in Fig. 2 = 11.0° θ2 - 24°, θ3 =
17, σ in Fig. 6 for 7°, = 14.4°θ,
2=20.9°, and with the arrangement shown in Figure 2 cos'σ1/
4θ2=0.779, whereas in the arrangement of FIG. 6, cos′θ11/CO3′θ,2=0.866, and the difference in illuminance on the imaging plane is reduced.

In the optical system of another embodiment shown in FIG. 7, the second traveling mirror is a single mirror 4 that is perpendicular to the document surface, and the three lenses are arranged in a staggered manner in two rows, one above the other. . Each lens is arranged so that the optical axes Qi and Q2 are parallel to the contact glass IIC.

On the other hand, in the embodiment shown in FIG. 8, the optical axes Q, , Q2 of each lens are not parallel to the contact glass l,
It lies within a plane that includes the longitudinal center line of the slit irradiation section on the document and the center point of each lens.

In the case of the embodiment shown in FIG. 3 as well, the lenses in the upper and lower stages are arranged in such a posture.

In these embodiments, the optical axis of the lens and the contact glass l
Since the difference in the absolute value of the angle (for example, the difference between β and γ in FIG. 8) is small, the difference in the amount of light reaching each light receiving sensor 8 can be practically ignored.

If the second traveling mirror is a single mirror perpendicular to the contact glass l, as in the embodiments shown in FIGS. 7 and 8, the mirror 5 can be omitted, and the decrease in the spectral amount will be less. The height will be slightly larger.

The color separation filter 7 may be provided before or after the lens 6, and may be determined by considering the size of the space before and after the lens 6.

Effects As described above, according to the present invention, a compact color image reading optical device can be obtained that can read color images with high image quality and high speed without a decrease in light amount, uneven light amount, or positional deviation of each color image.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention, and FIG.
FIG. 3 is a longitudinal sectional view showing another embodiment, and FIG. 4 is a plan view in the direction of arrow C in FIG. 3. The side of the lens and sensor seen in
5 is a side view showing a modified embodiment similar to that in FIG. 4, FIG. 6 is a plan view showing an expanded view of the optical path of the embodiment shown in FIG. 3, and FIGS. 7 and 8 are respectively FIG. 6 is a vertical cross-sectional view of another embodiment of the present invention. 0...Color original l...Contact glass 2...
・White light source lamp 3...First traveling mirror 4.5...
Second traveling mirror 6 (6t, 62.63)... Lens 7 (71, 72, 73)... Color separation filter 8 (8
1, 82, 83)... Light receiving sensor (COD) 1982
Kazuo Wakasugi, Commissioner of the Japan Patent Office, January 12, 1998 Patent Application No. 155780 2 Name of the invention Color image reading optical device 3 Relationship with the person making the amendment Patent Applicant Name (Name) (674) Ricoh Co., Ltd. 4 Agent Address Kaji Kogyo Building 2-32-4 Nishi-Shinbashi, Minato-ku, Tokyo Telephone (433) 4564 Postal code 105F--m
--5-1 t-t-, 1 Name Patent attorney (6313) Takehisa Ito"'+ ,
5. Date of amendment order (voluntary) Date of dispatch: Month, Day 6, 1920. Columns for the scope of claims and detailed description of the invention of the specification to be amended. 7. Contents of amendment (1) The scope of the claims shall be amended as shown in the attached sheet. (2) "As a result, as shown in FIG. 6" on page 9, lines 4-5 of the specification is corrected as follows. ``Figure 6 is a developed view of the optical path when viewed in the E direction from Figure 5, but by doing as described above'' (3) Ibid., p. 10, 13.
Lines 1 and 14 “Slit irradiation area on the original...”
...is within the plane. ” is corrected as follows. "The slits are slanted and arranged so that they intersect with each other on the manuscript surface when viewed in the longitudinal direction. -1 (4) Add the following sentence in a new line after line 20 of the same page of the same book. [In addition, as shown in Fig. 8, the reading optical system has a second traveling mirror as one mirror 4 perpendicular to the document surface, and the optical axis of the reflected light from this mirror (when viewed from a side view) In the case where the optical axis of the lens is arranged with the optical axis aligned with 2-, the angle α between the first traveling mirror 3 and the contact glass 1 is usually as follows, when the angle between the optical axis of the lens and the contact glass is θ. The optical axis is set so that the light is emitted from the document at right angles.However,
If the angles β and γ between the upper lens and the lower lens with the contact glass are different, as in the example shown in Fig. 8, the value of α should be set to “-45° + (β1′)/4. It is best to set Since the width of the light-receiving area is minute, it can be ignored.'' Attachment [2, Claims (1) White light source and first traveling device capable of moving an original placed on a flat contact glass at a constant speed The slit is scanned by a mirror and a second traveling mirror that can be moved synchronously in the same direction at half the speed of the mirror, and the reflected light beam from the document surface is reflected by a plurality of lenses arranged in parallel with each other and provided for each lens. A color image reading optical device characterized in that the color image reading optical device is configured such that the entire slit length of the document surface is projected and imaged onto the light receiving sensors provided respectively through color separation filters of different colors. . (2) The apparatus according to claim 1, wherein the plurality of lenses are arranged in a row parallel to the original irradiation slit. (3) The apparatus according to claim 1, wherein the plurality of lenses are arranged in a staggered manner in two rows parallel to the document irradiation slit. When viewed in the longitudinal direction of the radiation slit, the document surface (5) l
4. The device according to claim 1, wherein the lenses are arranged such that their optical axes are parallel to each other. ” 2-357-

Claims (5)

[Claims] (1) A white light source and a first running mirror that can move an original placed on a flat contact glass at a constant speed, and a second running mirror that can move synchronously in the same direction at half the speed. According to the slit scanning I1, the reflected light beam from the document surface is passed through a plurality of lenses arranged in parallel with each other and color separation filters of different colors provided for each lens, and a light receiving sensor provided corresponding to each lens. 1. A color image reading optical device, characterized in that it is configured to project and image the entire slit length of a document surface, respectively. (2) The apparatus according to claim 1, wherein the plurality of lenses are arranged in a row parallel to the original irradiation slit. (3) The apparatus according to claim 1, wherein the plurality of lenses are arranged in a staggered manner in two rows parallel to the document irradiation slit. (4) A patent claim characterized in that each lens is arranged such that the optical axis of the plurality of lenses set forth in item (1) is within a plane that includes the longitudinal center line of the slit irradiation section on the document and the center point of the lens. The device according to item 1 or 3 of the scope. (5) Claim 1, characterized in that the lenses are arranged so that their optical axes are parallel to each other.
The device according to paragraph 3 or paragraph 3.