JPH0341867A - Picture reader - Google Patents

Abstract

PURPOSE:To read a color picture with high accuracy even when more or less luminous unevenness exists due to the manufacture error of the original lighting system by arranging an anamophic lens to an optional position in a picture reading optical system and a slit in front of an original face. CONSTITUTION:A luminous flux in a meridional cross section shown in figure among emitting luminous flux from a point B on an optical axis of a projecting lens 6 on an original 4 is collected by the lens 6 and made incident in a cylindrical lens 7. Since no refracting force exists in the meridional cross section of the lens 7, the luminous flux passes as it is and a picture of the point B is formed on a face of a picture read means 8. On the other hand, the luminous flux in a sagittal cross section shown in figure in emitting luminous flux from the point B of the face of the original 4 is collected by the lens 6 and made incident in the lends 7. Since divergence exists in the sagittal cross section of the lens 7, the luminous flux receives the divergent action and is spread and nearly collimated to provide a spectral characteristic as shown in figure. The light is made incident simultaneously in 3 CCDs 81, 82, 83 on the means 8. Thus, the color picture information of the B, G, R color of the point B on the face of the original 4 is read simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image reading device, and in particular to a color copying machine that uses a plurality of line sensors to read color image information on a document surface with high precision. The present invention relates to an image reading device suitable for use in color scanners, color facsimiles, and the like.

(Prior art) Conventionally, color image information on the document surface is transmitted through a projection system.
Many proposals have been made for image reading devices that form an image on the surface of a line sensor such as a CD and read color image information using the output signal from the line sensor at this time.

FIG. 5 is a schematic diagram of a conventional image reading device.

In the figure, 1a is a light source, and tb is a concave mirror, which efficiently focuses the light from the light source 1a onto the document 4 side. Reference numeral 3 denotes a document table glass for supporting the document, and 6 a projection lens which projects the image document 4 onto the surface of an image reading means 8 comprising a line sensor such as a COD.1 The image reading means 8 has three CCDs 81 on a substrate. ．．
It consists of a 3-line monolithic COD with 82.83 arranged.

On the light-receiving surfaces of the three CCDs 81, 82, and 83, color filters of B, G, and R having the spectral characteristics shown in FIG. 9, for example, are provided by vapor deposition or the like.

The relative sensitivity of the device to the document in the same figure is the spectral energy phase separation of the light source la (Figure 7) and C0D81.82.8
For example, the 6th
The spectral distribution is as shown in the figure.

At this time, when reading the image on the document surface using a CCD, the distance between each of the three lines on CC and D and the projection lens 6
The image reading position shifts for each color on the document surface by an amount outside the dimension obtained by printing the reciprocal of the imaging magnification.

For example, if the distance between the CCDs 81, 82, and 83 is 0.2 mm as shown in FIG. 11, the projection magnification of the projection lens 6 is 17.
10, the amount of deviation M of the image reading position on the fourth side of the original in FIG. 5 is M=0.2×10=2 (mm). Now, when reading the original 4, in the same 1iI -
When moving downward in the direction of the arrow Y from the force, the image of the tip of the document 4 is formed on the CCD 83, t: on the means 8 by the projection lens 6 when it reaches the point . do. The spectral characteristics when read with CCD83 are 61st M.
If the spectral characteristic B is obtained, image information of blue light is detected from the light beam that falls on the dotted document.

Next, move the rX document 4 by 2 mm in the direction of arrow Y, and when it reaches the 4th point, the above-mentioned point will be captured by the CCD using the projection lens 6.
The image is formed on 82. When the spectral characteristic when read by the CCD 82 is the spectral characteristic G shown in FIG. 6, image information of green light is detected.

When the document 4 is further moved by 2 mm and positioned at the division point, the CCD 81 is used in the same manner as described above to obtain the spectral characteristics R1, shown in Figure 56.
Based on this, six image information of h color light is detected.

In this way, the original 4 is moved in the Y direction on the original platen glass 3, and the CCD 81, 82, 8 having each spectral characteristic is
3, the color image on the four sides of the R document is read using three color lights.

(Problems to be Solved by the Invention) In the conventional image reading device shown in FIG. 5, it is necessary that the light intensity distribution be uniform in the reading width from point K to point i when reading the original 4. . FIG. 8 shows an example of the light amount distribution on the four sides of the document at this time. The light amount distribution E is obtained when the positions of the light source 1a and the concave surface Ill 1b are adjusted to improve the light collection efficiency.

When the light intensity distribution is E, points t and J on the surface of the image reading means 8
, the light intensity value at point J is shown in Figure 1O.As shown in the same figure, assuming the light intensity value at point J is 100, the distance il! At point i, which is reduced by 1M, the light intensity value becomes 70, which is a decrease of about 30% in light intensity.

However, in reality, due to mounting errors of the light source 1a and the concave surface jl 1b, the peak value of the light amount distribution E° on the four surfaces of the document deviates, for example, by a distance of 1IId. The deviation lld at this time is not uniform on the back side of the document and on the front side of the center 2, and therefore the light amount distribution changes. For example, the light amount distribution E shown in Figure 1Q
It becomes like °.

This result is light at point i! The a value is 30, which may be about 70% lower than the maximum value. Also, this deviation ff
1d is not uniform at the back, front, and center of the document, which may result in light intensity unevenness of up to -70%.

For this reason, each element of the illumination system is generally set so that the efficiency of condensing light onto the document surface is reduced to obtain the light amount distribution F shown in FIG. 8. Figure 10 shows the light ffi fJ at points i, J, and
According to this, even if the light intensity distribution becomes F° due to assembly errors, the unevenness of the light intensity at points i, J, can be reduced to about 10% as shown in FIG. 1O.

However, this method reduces light collection efficiency, which reduces the light layer on the surface of the document, requires a large light source to obtain the desired brightness, increases power consumption, and requires a projection lens with a large aperture ratio. The problem arises that it is necessary to use other materials.

The present invention uses a slit in front of the document surface and an anamorphic lens that is appropriately placed at any position in the optical path of the image reading optical system, thereby maintaining high illumination efficiency on the document surface with a simple configuration. An object of the present invention is to provide an image reading device that can read highly detailed color images by uniformizing the light amount distribution.

(Means for Solving the Problems) The image reading device of the present invention projects an image illuminated by an illumination system onto an image reading means surface having a plurality of line sensors through a projection system, and In an image reading device configured to read the image in at least 62 colors, a slit is arranged in front of the image so that its long side is in the same direction as the arrangement direction of the elements of the line sensor, and The present invention is characterized in that an anamorphic lens is disposed in the optical path between the image and the image reading means, with its refractive surface facing the direction in which the line sensor of the ?I line sensor is juxtaposed.

(Embodiment) FIG. 1(A) is a schematic diagram of a main part of an optical system according to a first embodiment of the present invention. FIG. 1(B) is a schematic diagram of the main parts when viewed from the direction of arrow P in FIG. 1(A).

In the figure, numeral 1 is a light source, for example, a halogen lamp or the like. Reference numeral 2 denotes a slit which limits the area over which the surface of the document 4 held on the document table glass 3 is illuminated by the light beam from the light film. Reference numeral 6 denotes a projection lens which projects an area limited by the opening of the slit 2 of the original onto the surface of the image reading means 8 through an anasophic lens 7 (described later). Three CCDs (
It consists of a 3-line monolithic CCD with 81, 82, and 83 line sensors (line sensors) arranged, and images are read using three color lights of R, G, and B.

B, G, and R color filters having spectral characteristics shown in FIG. 9, which are similar to the conventional example shown in FIG. 5, are provided on the light-receiving surfaces of the three CCDs.

The spectral characteristics of image reading by each CCD 81, 82, 83 are as shown in FIG. 6, for example, as in the conventional case.

In this embodiment, the longitudinal opening of the slit 2 is, for example, in the direction in which the elements of the line sensor 82 are arranged (perpendicular to the paper surface).
are arranged in the same direction.

Anamorphic lens 7 is line sensor 81.82.8
It is made up of a diverging cylindrical lens having a refractive surface in the juxtaposed direction (parallel to the plane of the paper) of 1 and is disposed in front of the image reading means 8. FIG. 1(C) is a perspective view of the cylindrical lens 7 used in this example.

In this embodiment, among the light beams emitted from point B on the optical axis of the projection lens 6 on the fourth surface of the document, the light beam within the meridional cross section shown in FIG. incident on . Cylindrical lens 7
Since there is no refractive power in the meridional cross section of , the light beam passes through as it is and forms an image of point B on the image reading means 8 surface.

On the other hand, the same figure (A) of the light beam emitted from point B on the fourth surface of the original.
The light beam within the sagittal section shown in is condensed by the projection lens 6 and enters the cylindrical lens 7.

Since there is a diverging effect in the sagittal cross section of the cylindrical lens 7, the light beam is spread by the diverging effect and becomes approximately parallel light, which is transmitted to the three CCDs 81° 82 on the surface of the image reading means 8 having the spectral characteristics shown in FIG. .83 simultaneously.

As a result, the color image information of the B, G, and R color lights at the point B on the four sides of the document are simultaneously read.

The three CCDs 81, 82, and 83 of the image reading means 8 also provide color image information to points corresponding to off-axis points on the four sides of the draft.
Therefore, reading is performed simultaneously as at point B.

As described above, in this embodiment, the reading section of the original 4 is arranged through the slit 2.
By using the cylindrical lens 7 and the cylindrical lens 7, the position is set at l in the scanning direction, that is, the point J in FIG.
Even if there is some light intensity distribution on the four sides of the original, for example, the light intensity distribution E° will vary from the light intensity distribution E shown in Fig. 8.
Even if there is variation due to assembly errors, etc., the variation is 10%.
This can be made extremely small compared to the conventional method.

In this embodiment, the width of the slit 2 in the direction of the arrow 5 is the width of the document 4.
When the reading resolution is, for example, 16 bells/mm, it is approximately 62.5°.

In this embodiment, when reading the original 4 using two-color light, for example, red and black, it is sufficient to dispose a cyan color filter on the CCD 82 without providing a color filter on the CCD 81.

FIG. 2(A) is a schematic diagram of the main parts of an optical system according to a second embodiment of the present invention, and FIG. 2(B) is a schematic diagram of the main parts when viewed from the direction of arrow P in FIG. 2(A). .

This embodiment is characterized in that a diverging cylindrical lens as an anamorphic lens is arranged in the optical path between the slit 2 and the projection lens 6.

In this embodiment, as shown in FIG. 2(A), the sagittal image plane is set at a position r1121 farther than the image reading means 8, and C
A convergent beam of light is incident on CD81.82.83i+j.

This allows the image reading means 8 to simultaneously read one point on the four sides of the original as described above. The other structure is the same as the first embodiment shown in FIG. 1 (Al, (B)).

No. 31a (A) is f of the optical system of the third embodiment of Kokuhatsu IJ1.
fKBm! It is Showa IA. In this embodiment, a lenticular lens 73 in which minute cylindrical lenses are arranged side by side as shown in FIG. 3(B) is disposed as an anamorphic lens at 1111 between the projection lens 6 and the image reading means 8.

This expands the incident light beam and makes it incident on both ft reading means 8 to read the image. The diffusing effect of the light beam by this lenticular lens 73 does not spread in the depth direction (in the direction perpendicular to the plane of the paper, within the meridional cross section) as shown in FIG. It has a positive effect.

In this embodiment, the first UA
This is the same as the first embodiment (A) and (B).

No. 4121(A) is fJTJ4'J! of the present invention! Cost department of optical system of example! Case diagram, Figure 4 (B) is the same II (A)
FIG. 2 is a schematic diagram of main parts when viewed from the direction of arrow P.

In the present embodiment, a cylindrical lens 74, which is formed by integrating two convergent cylindrical lenses 74a and 74b, is arranged near the original 4.

The cylindrical lens 74b effectively guides the light beam from the light source 1a to the opening of the slit 2, thereby illuminating the original 4.

Figure 4 (C) shows the cylindrical lens 74 in Figure 4 (A).
FIG. As shown in the figure, the refractive surface in the area indicated by the length d of the lens surface of the cylindrical lens 74b efficiently directs the direct light from the light @1a and the reflected light flux from the concave surface tilb to the opening of the slit 2. It is guiding light.

In this embodiment, among the light beams emitted from the opening of the slit 2 of the document 4, the light beam within the sagittal section shown in FIG.
After forming an image at a point 41 in front of the image reading means 8,
The light becomes a complete beam of light and enters the image reading means 8. As shown in the one-way surface (B), the light beam within the meridional cross section passes through the cylindrical lens 74a without being converged, and is imaged by the projection lens 6 onto the surface of the image reading means 8.

As a result, the color image information of one point on the original H44 surface is read in CGDB 1.82.83 of the image reading means 8 as shown in FIG.
, (B) are read simultaneously as in the first embodiment.

In this embodiment, the cylindrical lens 74a may be formed of a diverging refractive surface so that the image forming point 41 in FIG.

(Effects of the Invention) According to the present invention, as described above, by arranging the slit in front of the document surface and the anamorphic lens at an arbitrary position in the image reading optical system, there may be some unevenness in the amount of light due to manufacturing errors in the document illumination system. It is also possible to achieve an image reading device that can read color images with low power consumption and high accuracy while maintaining high light collection efficiency.

[Brief explanation of drawings]

1 to 4 are schematic diagrams of the main parts of the first to fourth embodiments of the present invention, FIG. 5 is a schematic diagram of the main parts of a conventional image reading device, and FIG. 6 is a diagram of the spectral characteristics of color image reading. Explanatory diagrams: Figure 7 is an explanatory diagram of spectral energy phase separation of a halogen lamp, m8 diagram is an explanatory diagram of illuminance distribution on the document surface, Figure 9 is an explanatory diagram of the spectral characteristics of a color filter, and Figure 1O is an explanatory diagram of Figure 5. IIJ] I2y, FIG. 11 is an explanatory diagram of a part of FIG. 5. In Figures 1 and 4, (A) is an optical path diagram in the sagittal cross section, (B) is an optical path diagram in the meridional cross section, (C) is a perspective view of the anamorphic lens, and in Figure 2 (A) is a sagittal cross section. Optical path diagram inside (B)
is the optical path diagram in the meridional section, and in Figure 3 (A
) is an optical path diagram in a sagittal section, and (B) is a perspective view of an anamorphic lens. In the figure, 1 is a light source, 2 is a slit, 3 is an original table glass, 4 is an original, 6 is a projection lens, 7, 73.74 are anamorphic lenses, 8 is an image reading means, 81, 82, 83 are CCs
D. Figure (A) Figure (B) Figure (A) Figure (B) Figure (A) Figure (8) Figure (A') Figure (B) Figure 5 Figure Figure 0

Claims (2)

[Claims] (1) Image reading in which an image illuminated by an illumination system is projected via a projection system onto an image reading means having a plurality of line sensors, and the image is read in at least two colors by the image reading means. In the apparatus, a slit is arranged near the front of the image so that its longitudinal opening is in the same direction as the arrangement direction of the elements of the line sensor, and an anamorphic lens is provided in the optical path between the image and the image reading means. An image reading device characterized in that the plurality of line sensors are arranged with their refracting surfaces facing in the direction in which the plurality of line sensors are arranged side by side. (2) The image reading device according to claim 1, wherein the anamorphic lens is composed of a diverging cylindrical lens or a lenticular lens.