JPH05304579A - Close contact image sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to reduce the influence of the image around the reading position and generate an accurate signal corresponding to the image at the reading position. [Structure] Light-shielding plates 11a and 11b are attached to a lower surface of a glass material 4 at intervals of a predetermined length L with an optical axis of each rod lens of a rod lens array 5 interposed therebetween. Light shield 1
1a and 11b cover most of the lower surface of the glass material 4 except the region corresponding to the interval L.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact image sensor for obtaining an electric signal corresponding to an image formed on an original by photoelectrically converting reflected light from the original by a photoelectric conversion element.

[0002]

2. Description of the Related Art A contact type image sensor is a line sensor in which a large number of photoelectric conversion elements are arranged over a length substantially equal to the width of the original, which is a reflected light image of the original when the original is illuminated by a light source. , An image is formed at a magnification of 1: 1 by an equal-magnification erecting imaging optical system such as a rod lens array, and photoelectric conversion is performed by a line sensor to generate an electrical signal (image signal) corresponding to an image formed on a document. ) Is what you get.

In the rod lens array, a large number of rod lenses are arranged in the same direction as the arrangement direction of photoelectric conversion elements so that the optical axes of the rod lenses are parallel to each other. Further, the focus of each rod lens is determined at a position symmetrical with respect to the midpoint in the optical axis direction, and the original and the photoelectric conversion element are arranged so as to face each other at this focus position.

The positional relationship between the rod lens, the original and the photoelectric conversion element is shown in FIG. In the figure, 71 is a rod lens, 72 is a document, and 73 is a photoelectric conversion element. As shown in this figure, the reflected light from the point P1 for one pixel of the original 72 is imaged by the rod lens 71 on the photoelectric conversion element 73 located at the point P2 for one pixel facing the point P1.

At this time, if the rod lens 71 has ideal characteristics, the photoelectric conversion element 73 located at the point P2.
The reflected light imaged on should be only the reflected light from the point P1 on the original 72. Therefore, focusing on the reflected light A from the point P3 deviated from the point P1 as shown in FIG. 7B, if the rod lens 71 exhibits ideal characteristics as described above, the light passing through the rod lens 71 Should go to a point P4, which is symmetrical to the point P3, as indicated by the dashed arrow B. However, in the actual rod lens 71, it is difficult to obtain ideal characteristics due to the characteristics of the lens and the manufacturing accuracy, and stray light is generated when passing through the rod lens 71.
Therefore, for example, as indicated by an arrow C in FIG. 7B, the reflected light from the point P3 deviated from the point P1 is converted into the photoelectric conversion element 7.
There is a risk of leaking into 3. That is, not only the reflected light from the point P1 but also the reflected light from the peripheral position thereof enters the photoelectric conversion element 73, and an image signal including a signal component corresponding to a considerably wide area is generated.

Therefore, image information other than the position to be originally read is also read, and the obtained image signal has the stray light component of the rod lens 71 overlapping the original image signal component.

This problem will be specifically described below. FIG. 8A shows a state in which the white line portion of the image in which the white line is included in the black background (portion indicated by diagonal lines) of the original 72 is being read. The point P1 is located at the white line portion in order to read the white line portion, but there is a possibility that the reflected light from the original 72 may actually be imaged on the photoelectric conversion element 73 due to the influence of the leak in the rod lens 71. A certain area is an area indicated by a circle S in the figure. Therefore, some of the regions S1, S1,
S2 becomes a black background portion. Therefore, FIG. 8 (b)
As compared with the case where all of the area S is located in the white background portion as shown in (3), the amount of incident light on the photoelectric conversion element 73 decreases, and the output voltage of the photoelectric conversion element 73 decreases.

FIG. 9 is a diagram showing an example of the output characteristics of the photoelectric conversion element 3 in the respective states of FIG. 8 (a) and FIG. 8 (b). Thus, although the original reading position is the same white background portion, the voltage value output from the photoelectric conversion element 73 changes depending on the surrounding conditions.

[0009]

As described above, in the conventional contact-type image sensor, leakage occurs due to stray light generated in an optical system such as a rod lens, and the obtained signal is a signal of an image around the reading position. There was a problem that it became an affected and incorrect one.

The present invention has been made in consideration of such circumstances, and an object of the present invention is to reduce the influence of an image around the reading position and to generate an accurate signal corresponding to the image at the reading position. An object is to provide a contact-type image sensor that can be generated.

[0011]

A first invention is a light source for irradiating a document with light, such as an LED array, and photoelectric conversion means for generating an electric signal according to incident light, such as a photoelectric conversion element. An optical system, such as a rod lens array, that causes reflected light from a predetermined position of the document illuminated by the light source to enter the photoelectric conversion means, and the optical system of reflected light from a position other than the predetermined position of the document. And a light-shielding means such as a light-shielding plate for reducing the amount of incidence on the light source.

The second invention is, for example, an original table made of glass or the like for setting an original to be read, and for irradiating the original set on the original table with light, for example, LE.
A light source such as a D array, a photoelectric conversion means such as a photoelectric conversion element that generates an electric signal according to incident light, a support means such as a support having a wall surface that linearly extends to the document table, and the support. An optical system, such as a rod lens array, which is fixed to the wall surface of the device and causes reflected light from a predetermined position of the document irradiated with light from the light source to enter into the photoelectric conversion device, and from the predetermined position of the document. A light blocking unit such as a light blocking plate that reduces the amount of reflected light from the position on the light source side incident on the optical system is provided.

[0013]

By taking these measures, the light reflected from other than the predetermined position of the document is blocked by the light blocking unit (also by the support in the second invention) and blocked from entering the optical system. Then, the reflected light from a predetermined position of the document enters the optical system, is incident on the photoelectric conversion means by the optical system, and an electric signal corresponding to the light is generated by the photoelectric conversion means.

[0014]

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the structure of the contact image sensor according to this embodiment. This contact image sensor includes an LED array 1, a support 3, a glass material 4, a rod lens array 5, a line sensor 6, a terminal 8, a circuit board 9, a connector 10 and a light shielding plate 11a.
11b.

The LED array 1 irradiates the original 2 placed on the glass material 4 with light. This LED array 1
A large number of LEDs are arranged slightly longer than the original reading width and are fixed to the support 3.

The support 3 has a length slightly larger than that of the LED array 1, and its cross-sectional shape is such that the central portion in the vertical direction (vertical direction in the drawing) is constricted as shown in the drawing. The wide portion on the lower end side forms sensor fixing portions 3a and 3b for fixing the line sensor 6. One side surface (left side in the figure) of the constricted portion near the central portion is an inclined surface that increases from the center in the width direction (left and right direction in the figure) toward the end portion. The LED fixing portion 3c for fixing is formed. A side surface (right side surface in the figure) opposite to the LED fixing portion 3c in the constricted portion near the center is a vertical surface, and forms a lens fixing portion 3d for fixing the rod lens array 5. .. A wide portion on the upper end side forms glass fixing portions 3e and 3f for fixing the glass material 4. The sensor fixing portion 3b
And the glass fixing portion 3f projects outward in the width direction from the lens fixing portion 3d. The glass material 4 transmits light well, and is fixed on the glass fixing portion 3d of the support body 3. The glass material 4 forms a document table on which the document 2 is placed.

The rod lens array 5 is a so-called gradient index type rod lens in which the refractive index continuously decreases from the center toward the peripheral edge in the radial direction, and the optical axis of the rod lens array 5 crosses the upper surface of the glass material 4. And a predetermined number of rod lenses are arranged such that the optical axes of the rod lenses are parallel to each other. Further, each rod lens is focused on a position symmetrical with respect to the midpoint in the optical axis direction. The rod lens array 5 includes a support body so that one focus of each rod lens is located at a point P near the upper surface of the glass material 4 and the rod lenses are arranged along the longitudinal direction of the support body 3. 3 is fixed to the lens fixing portion 3d.

The line sensor 6 is formed by arranging a large number of photoelectric conversion elements 7, and obtains an electric signal by serializing a signal output from each photoelectric conversion element 7. The line sensor 6 is arranged such that each photoelectric conversion element 7 is located at the other focal point of each rod lens of the rod lens array 5, and is fixed to the sensor fixing portions 3 a and 3 b of the support body 3. The line sensor 6 is electrically connected to the circuit board 9 via the terminal 8. The line sensor 6 is provided on the circuit board 9.
An electronic circuit including a drive circuit for driving and controlling the signal and a circuit for processing a signal obtained by the line sensor 6 is formed. Further, on the circuit board 9, there is mounted a connector 10 for exchanging signals with, for example, a facsimile machine to which the present contact image sensor is applied.

Reference numerals 11a and 11b denote light-shielding plates having a light-shielding property, which are attached to the lower surface of the glass material 4 at intervals of a predetermined length L, sandwiching the optical axis of each rod lens of the rod lens array 5. The light shielding plates 11a and 11b cover most of the lower surface of the glass material 4 except for the region corresponding to the distance L. That is, the light shielding plates 11 a and 11 b form slits having an interval L along the rod lens array 5.

As described above, in the contact type image sensor constructed as described above, as shown in FIG. 2, a point Pa deviated from the point P (reading position) which is the focal point of the rod lens array 5,
The light reflected by Pb is blocked by the light blocking plates 11a and 11b and does not reach the rod lens array 5. Therefore, even if the accuracy of each rod lens of the rod lens array 5 is low and stray light may be generated, most of the light that is the source of stray light is blocked, and the stray light is greatly reduced. Thus, leakage of reflected light around the point P, which is the reading position, into the photoelectric conversion element 7 is reduced, and the influence of the output signal of the photoelectric conversion element 7 on the image around the point P is reduced. Therefore, the photoelectric conversion element 7 can obtain an accurate signal corresponding to the image at the point P.

The distance L between the shading plate 11a and the shading plate 11b is set so that the reflected light at the point P is incident on each rod lens of the rod lens array 5 with a sufficient amount of light for generating an image signal. Make it as small as possible without disturbing it.

(Second Embodiment) A second embodiment of the present invention will be described below. FIG. 3 is a sectional view showing the structure of the contact image sensor according to this embodiment. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

The difference between this embodiment and the first embodiment is that the shading plate 11b is omitted and only the shading plate 11a on the LED array 1 side is omitted. With this configuration, as in the first embodiment, leakage of reflected light around the point P which is the reading position into the photoelectric conversion element 7 is reduced, and the photoelectric conversion element 7 responds to the image at the point P. A precise signal can be obtained.

However, since the light shielding plate 11b is omitted in the present embodiment, the amount of leak is slightly larger than that in the case of the first embodiment, but the light shielding plate 11b is omitted and the original document 2 is omitted. Since the reflected light from B is incident on the rod lens array 5 on the side away from the LED array 1, the illuminance by the LED array 1 is low and the amount of reflected light is low. Leakage into the conversion element 7 is sufficiently reduced.

(Third Embodiment) The third embodiment of the present invention will be described below. FIG. 4 is a sectional view showing the structure of the contact image sensor according to this embodiment. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

The difference between this embodiment and the first embodiment is that the light blocking plates 11 are provided on both sides of the upper end of the rod lens array 5.
This is the point where c and 11d are provided. With this configuration, as in the first embodiment, leakage of reflected light around the point P which is the reading position into the photoelectric conversion element 7 is reduced, and the photoelectric conversion element 7 responds to the image at the point P. A precise signal can be obtained. (Fourth Embodiment) The fourth embodiment of the present invention will be described below.

The contact type image sensor is required to be small in size depending on its application. FIG. 5 is a cross-sectional view showing the structure of a contact-type image sensor whose size is reduced. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

This contact image sensor includes an LED array 1, a glass material 4, a rod lens array 5, a line sensor 6, a terminal 8, a circuit board 9, a connector 10 and a shading plate 11.
a and the support 12.

The side of the support 12 on which the LED array 1 is fixed (the left side in the drawing) is the support portion 3 in the first embodiment.
It has the same shape as. However, on the side of the support 12 where the rod lens array 5 is fixed (on the right side in the drawing), the sensor fixing portion 3b and the glass fixing portion 3f of the supporting portion 3 in the first embodiment are removed, and the supporting portion 12 in the first embodiment is removed. The wall portion 12a has a shape obtained by vertically extending the lens fixing portion 3d of the support portion 3. A glass material is fixed to the upper end of the wall portion 12a, and the upper end of the wall portion 12a functions as a glass fixing portion. The rod lens array 5 is fixed to the center of the wall portion 12a, and the center of the wall portion 12a functions as a lens fixing portion. The line sensor 6 is fixed to the lower end of the wall portion 12a, and the lower end of the wall portion 12a functions as a sensor fixing portion.

As described above, the support 12 has a shape obtained by removing the sensor fixing portion 3b and the glass fixing portion 3f of the support 3 in the first embodiment. Since the sensor fixing portion 3b and the glass fixing portion 3f of the support body 3 project in the width direction, the width of the supporting body 12 of the present embodiment is shortened by the amount of protrusion of the sensor fixing portion 3b and the glass fixing portion 3f.
Now, in the contact type image sensor having such a structure, in this embodiment, the light shielding plate 11a on the LED array 1 side is provided.
Only provided.

Thus, according to this embodiment, the reflected light on the side near the LED array 1 around the point P which is the reading position is blocked by the light blocking plate 11a and does not reach the rod lens array 5. The reflected light on the side far from the LED array 1 is blocked by the wall 12a and does not reach the rod lens array 5. Therefore, leakage of the reflected light around the point P, which is the reading position, into the photoelectric conversion element 7 is reduced, and the photoelectric conversion element 7 can obtain an accurate signal corresponding to the image at the point P.

(Fifth Embodiment) The fifth embodiment of the present invention will be described below. FIG. 6 is a sectional view showing the structure of the contact image sensor according to this embodiment. The same parts as those in FIGS. 1 and 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

The contact-type image sensor of this embodiment has substantially the same structure as that of the fourth embodiment, except that the upper end of the rod lens array 5 is closer to the LED array 1 (left side in the figure).
In addition, the light shielding plate 11c is provided.

Also with this configuration, as in the fourth embodiment, the leak of reflected light around the point P which is the reading position into the photoelectric conversion element 7 is reduced, and the photoelectric conversion element 7 has the point P.
An accurate signal corresponding to the image at is obtained.

The present invention is not limited to the above embodiments. For example, in the above-described first and second embodiments, the light-shielding plates 11a and 11b are used as the light-shielding means, but instead of the light-shielding plates 11a and 11b, a light-shielding paint is applied or printed on the glass material 4. Alternatively, a light-shielding film may be attached. Further, instead of the glass material 4, a light-shielding member such as a metal plate having a slit may be provided.

In each of the above embodiments, LE as a light source is used.
The D array 1, the line sensor 6 as the photoelectric conversion means, the rod lens array 5 as the optical system, and the light shielding plates 11a, 11b, 11c, 11d as the light shielding means are integrally arranged to form a contact type image sensor. However, it is also possible to form the contact-type image sensor by separately arranging it in, for example, a facsimile machine to which it is applied. In addition, various modifications can be made to the specific configuration and the like without departing from the spirit of the present invention.

[0037]

According to the first aspect of the present invention, there is provided photoelectric conversion means, such as a photoelectric conversion element, for generating an electric signal according to incident light.
For example, an optical system such as a rod lens array that causes reflected light from a predetermined position of the document to enter the photoelectric conversion unit, and, for example, light blocking that reduces the amount of reflected light from other than the predetermined position of the document that enters the optical system. It was equipped with a light-shielding means such as a plate.

A second aspect of the present invention is, for example, an original table such as a glass material for setting an original to be read, and for irradiating the original set on the original table with light, for example, LE.
A light source such as a D array, a photoelectric conversion means such as a photoelectric conversion element that generates an electric signal according to incident light, a support means such as a support having a wall surface that linearly extends to the document table, and the support. An optical system, such as a rod lens array, which is fixed to the wall surface of the device and causes reflected light from a predetermined position of the document irradiated with light from the light source to enter into the photoelectric conversion device, and from the predetermined position of the document. A light blocking unit such as a light blocking plate that reduces the amount of reflected light from the position on the light source side incident on the optical system is provided.
These reduce the influence of the image around the reading position,
The contact-type image sensor can generate an accurate signal corresponding to the image at the reading position.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a contact image sensor according to a first embodiment of the invention.

FIG. 2 is an enlarged view showing a main part in FIG.

FIG. 3 is a sectional view showing the structure of a contact image sensor according to a second embodiment of the invention.

FIG. 4 is a sectional view showing the structure of a contact image sensor according to a third embodiment of the invention.

FIG. 5 is a sectional view showing the structure of a contact image sensor according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view showing the structure of a contact image sensor according to a fifth embodiment of the present invention.

FIG. 7 is a diagram illustrating a conventional technique.

FIG. 8 is a diagram illustrating a conventional technique.

FIG. 9 is a diagram illustrating a conventional technique.

[Explanation of symbols]

1 ... LED array, 2 ... Original, 4 ... Glass material, 5 ... Rod lens array, 6 ... Line sensor, 7 ... Photoelectric conversion element, 11a, 11b, 11c, 11d ... Light-shielding plate.

Claims (2)

[Claims] 1. A light source for irradiating a document with light, a photoelectric conversion unit for generating an electric signal according to incident light, and a photoelectric conversion of reflected light from a predetermined position of the document irradiated with light from the light source. A contact type image sensor, comprising: an optical system for making light incident on the means; and a light-shielding means for reducing an incident amount of reflected light from other than the predetermined position of the document on the optical system. 2. A document table for setting a document to be read, a light source for irradiating the document set on the document table with light, and a photoelectric conversion means for generating an electric signal according to incident light. Supporting means having a wall surface that extends linearly to the document table, and light reflected from a predetermined position of the document, which is fixed to the wall surface of the supporting means and is irradiated with light from the light source, is incident on the photoelectric conversion means. A contact image sensor, comprising: an optical system; and a light-shielding unit that reduces the amount of reflected light from a position closer to the light source than the predetermined position of the original to the optical system.