JPH0678115A - Optical scanning image sensor - Google Patents

Abstract

PURPOSE:To obtain a reference signal which can be applied throughout the read width by reading the reference signal at every desired pixel density in the simple constitution. CONSTITUTION:An optical path changing member 19 can be inserted to the optical path from a light source to an original face 4, and total reflection and refraction of the member 19 are used to bend the scanning light in a direction intersecting orthogonally with the scanning direction. A white or black band- shaped part 6 formed on the surface of a platen glass 5 is irradiated by the totally reflected or refracted light, and the reflected light from the white or black band-shaped part 6 is made incident on a band-shaped photodetector 2, thus obtaining a white or black reference signal of the photodetector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor used in an input section of a facsimile or a copying machine, and more particularly, it scans light to irradiate the surface of an original document, and the confusion reflection light from the surface of the original document is strip-shaped light receiving element. The present invention relates to an optical scanning type image sensor for reading.

[0002]

2. Description of the Related Art Conventionally, as an optical scanning type image sensor, for example, as shown in FIG. 7, a fluorescent lamp light source 91 and a fluorescent lamp light source 91 are disposed below the fluorescent lamp light source 91 in a longitudinal direction and correspond to each pixel. An optical shutter 92 configured by linearly arranging a large number of liquid crystal switches, an equal-magnification imaging system lens 93 that collects light passing through the optical shutter 92, and an equal-magnification imaging system lens 93. There is a light-receiving element 96 formed on the transparent substrate 94 so that light passes through the transparent substrate 94 and illuminates the original 95, and reflected light from the original 95 enters. The light receiving element 96 is formed in a strip shape without being separated for each pixel, and the light receiving area is enlarged to increase the photoelectric conversion output to improve the S / N ratio. (See JP-A-61-218266).

According to the image sensor having the above-mentioned structure, the light from the fluorescent lamp light source 91 passes through the liquid crystal switch which opens and closes one by one, and the original document 94 through the same-magnification imaging system lens 93.
An image is formed in a spot shape on the surface, and the reflected light is received by the light receiving element 96.
Incident on. Therefore, the scanning density of light can be changed only by an integral multiple of the number of pixels, and the change of the reading density is limited. In addition, since the same-magnification imaging system lens 93 is used, the obtained depth of focus is at most about 1 mm at 400 DPI, and there is a drawback in that the original image is blurred and the original image cannot be read accurately.

Therefore, in order to eliminate the need for an equal-magnification imaging system lens, a strip-shaped light receiving element is formed on a substrate by a thin film process to improve productivity and reduce cost, and an optical element used in a laser printer or the like. A system, that is, an optical scanning type image sensor has been proposed in which a laser beam emitted from a laser diode is shaped by a collimator lens and a cylindrical lens, is scanned by a polygon mirror, and the scanning beam is irradiated onto the document surface through an f-θ lens. ing. The light receiving element is a thin film sandwich in which a lower electrode made of chromium (Cr), a photoelectric conversion layer made of hydrogenated amorphous silicon (a-Si: H), and an upper electrode made of indium tin oxide (ITO) are laminated in a strip shape. Type photodiode.

On the other hand, in the image sensor, the reference signals (white reference signal and black reference signal) are set for the bright output and the dark output in order to improve the image quality and the gradation reproducibility, and the image signal is corrected. Has been done. When obtaining the reference signal in the contact image sensor, for example, when reading the white reference signal, a white strip portion is formed on the platen glass (not shown) interposed between the transparent substrate 94 and the original 95, and the image sensor itself is formed. In the sub-scanning direction,
A white reference signal has been obtained by reading the reflected light from the white band. It has also been proposed that a light receiving element for a reference signal is provided in advance at the end of the light receiving element array and reflected light from a white original surface or the like is incident on the light receiving element to obtain a reference signal from its output. .

[0006]

However, in the case of the optical scanning type image sensor having the above structure, since the polygon mirror or the like is required, the scanning optical system becomes large and the number of parts increases, so that the image sensor itself is moved. However, the method of detecting the white reference signal due to the movement of the image sensor itself cannot be applied.

Further, in the case of the optical scanning type image sensor, since the reflected light from the original surface 4 has a substantially spherical intensity distribution, for example, as shown in FIG. When illuminating the end of the band-shaped light receiving element 2, the amount of reflected light at the end is smaller than the amount of reflected light at the central portion, and the relationship between the incident position of reflected light and the amount of reflected light is shown in FIG. It has a distribution like. Therefore, the amount of light incident on the end portion of the band-shaped light receiving element 2 decreases,
If all the signals output from the band-shaped light receiving element 2 to each pixel are corrected by the reference signal read at the end portion, there is a problem that accurate correction cannot be performed in most of the pixels near the center.

The present invention has been made in view of the above circumstances, and in an optical scanning image sensor, a reference signal applicable to the entire reading width is obtained by reading the reference signal for each desired pixel density with a simple structure. It is intended to provide a structure for.

[0009]

In order to solve the above-mentioned problems of the conventional example, the present invention provides a light source for irradiating a document surface with light, and a scanning means for scanning the light from the light source on the document surface.
An image sensor including a band-shaped light receiving element that receives reflected light from the document surface and a platen glass interposed between the document surface and the band-shaped light receiving element is characterized by the following configuration. A white or black strip having a width substantially equal to the original width is formed at a position parallel to the optical scanning line on the platen glass surface. An optical path direction changing mechanism capable of inserting an optical path changing member is provided in the optical path from the light source to the document surface. The optical path changing member has a property of shifting a light beam in a direction orthogonal to the scanning direction by reflecting or refracting the light.

[0010]

According to the present invention, an optical path changing member is inserted in the optical path from the light source to the document surface, and when the light beam from the light source enters the optical path changing member, the scanning light beam is scanned by utilizing total reflection and refraction. The light beam is shifted in a direction orthogonal to the direction, and the totally reflected or refracted light beam irradiates the white or black strip portion formed on the platen glass surface. Since the reflected light from the white or black strip portion is incident on the strip light receiving element, a white or black reference signal for the light receiving element can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 2, the optical scanning image sensor according to the present embodiment includes a scanning optical system 1 for scanning a laser beam on a document surface 4 and a strip-shaped light receiving element 2 for receiving the reflected light reflected by the document surface 4. And an optical system 3 for guiding the reflected light to the band-shaped light receiving element 2.

The scanning optical system 1 has a structure similar to that of an optical system used in a laser printer or the like, and includes a laser diode 11, a collimating lens 12, a cylindrical lens 13, a polygon mirror 14, and an f-θ lens 1.
5. Half mirror (or mirror with slit)
It is composed of 16 parts. The laser diode 11 emits pulsed light (laser light) modulated at a predetermined modulation frequency. By controlling the oscillation frequency of this laser light and the rotation speed of the polygon mirror 14, the document surface 4
The scanning speed and scanning density of the light above can be controlled. That is, the laser light from the laser diode whose frequency is controlled by the main scanning control means (not shown) is shaped by the collimator lens 12 and the cylindrical lens 13 and reflected by the surface on one side around the hexagonal polygon mirror 14. To do. Since the polygon mirror 14 is rotated at a predetermined rotation by the main scanning control means (not shown), the laser light becomes a scanning light beam having a predetermined beam width, and the scanning light beam passes through the f-θ lens 15. The document surface 4 is scanned at a predetermined speed, and a desired reading density can be obtained in the main scanning direction. The half mirror 16 bends the optical path of the reflected light including the image information of the document surface 4,
The light is condensed via the cylindrical lens 17 and guided to the band-shaped light receiving element 2 formed on the insulating substrate 21.

An optical path direction changing mechanism 19 which allows a flat plate 18 made of glass and having a width substantially the same as the width of the original surface 4 to be inserted in the optical path between the f-θ lens 15 and the half mirror 16. Is provided. Long flat plate 18
Is formed so that it can be inserted into the optical path when a reference signal is read by a plane plate moving means (not shown) inside the optical path direction changing mechanism 19. Further, the flat plate 18 can be inserted so that its longitudinal direction is along the scanning direction of the scanning light. As shown in FIG. 1, the plane plate 18 has an upper surface inclined by a few degrees (θ) with respect to the optical axis of the scanning light, so that f
The scanning light transmitted through the -θ lens 15 is totally reflected.

The structure of the optical system 3 for guiding the reflected light to the band-shaped light receiving element 2 will be described in detail with reference to FIG. 1. When the plane plate 18 is not inserted in the optical path, the scanning light incident from the light source is used. Passes through the half mirror 16 and the platen glass 5 to reach the document surface 4, and the reflected light from the document surface 4 containing the image information passes through the platen glass 5 and
The light is reflected by the half mirror 16 to change the optical path, and is condensed by the cylindrical lens 17 on the band-shaped light receiving element 2 (the optical path indicated by the solid line in FIG. 1).

When the flat plate 18 is inserted in the optical path, the scanning light incident from the light source is totally reflected by the upper surface of the flat plate 18 and the light beam is bent in the direction orthogonal to the scanning direction (sub scanning direction). It is bent and passes through the half mirror 16 and the platen glass 5, and becomes a light beam (dotted line) deviated in the sub-scanning direction with respect to the light beam (solid line) when the plane plate 18 is not inserted in the optical path. To reach. On the surface of the platen glass 5 on which the light rays (dotted lines) reach, a white strip portion 6 is formed along the light scanning direction. The white strip portion 6 is formed, for example, by applying white paint or the like to the platen glass 5. The reflected light from the white strip 6 is
The light is reflected by the half mirror 16 to change the optical path, and is condensed on the band-shaped light receiving element 2 by the cylindrical lens 17 (optical path indicated by a dotted line in FIG. 1).

As shown in FIG. 3, the strip-shaped light receiving element 2 has a strip-shaped lower electrode 22 made of chromium (Cr), a strip-shaped photoelectric conversion layer 23 made of hydrogenated amorphous silicon (a-Si: H), and an oxide. Upper electrodes 24 each of which is composed of an indium tin (ITO) layer and supplies a reverse bias voltage are laminated on an insulating substrate 21. As shown in FIG. 2, the lower electrode 22 is connected to the integrator 7, and reads the charge accumulated in the band-shaped light receiving element 2 by the reflected light while synchronizing with the oscillation frequency of the laser light. The output from the integrator 7 is input to the arithmetic circuit 8 having a storage unit, and the signals generated by the scanning light beam in the band-shaped light receiving element 2 are output in time series. Since the document surface 4 is configured to be movable in a sub-scanning direction orthogonal to the optical scanning direction by a document feeding means (not shown) such as a roller, the main surface and the sub-scanning of the document surface 4 are performed. The entire image can be read. Further, the reading density in the sub-scanning direction can be changed by controlling the feed speed in the sub-scanning direction.

Next, a reading method of the optical scanning type image sensor of this embodiment will be described. First, at the beginning of reading, the plane plate 18 is inserted in the optical path by the optical path direction changing mechanism 19. When the image sensor is driven in this state, the scanning light beam from the light source is totally reflected by the plane plate 18 and bent in the direction orthogonal to the scanning direction, and the white band-shaped portion 6 formed on the platen glass 5 surface is irradiated. Therefore, the reflected light from the white strip portion 6 enters the strip light receiving element 2. Since the strip-shaped light receiving element 2 is designed to always read out electric charges without being reset, the output from the strip-shaped light receiving element 2 is
The photocurrent generated according to the reflected light from the white strip portion 6 changes with time. When this photocurrent is input to the integrator 7, a current corresponding to the integrator cycle is output as a voltage.
If this integration period is matched with the oscillation frequency of the laser light, an output can be obtained corresponding to the scanning density. That is, if the read clock of the integrator 7 is synchronized with the frequency (modulation frequency of laser light) corresponding to the read density in the main scanning direction (reading density by optical scanning), a photocurrent proportional to the amount of reflected light is obtained. The white reference output having a desired pixel density can be obtained by being taken into the integrator 7 every cycle of the modulation frequency of the laser light. The white reference output correction signal is stored in the storage unit inside the arithmetic circuit 8.

Next, when the image sensor is driven with the flat plate 18 removed from the middle of the optical path, the scanning light beam from the light source illuminates the document surface 4. Therefore, the reflected light containing the image information of the document surface 4 is incident on the band-shaped light receiving element 2. Since the strip-shaped light receiving element 2 is designed to always read out electric charges without being reset, the output from the strip-shaped light receiving element 2 changes with time as the photocurrent generated according to the reflected light from the document surface 4. . Then, the integrator 7 reads the image signal at a desired pixel density as described above. Arithmetic circuit 8
In the above, by outputting the difference between the image signal and the correction signal for each pixel density, it is possible to output a true image signal with the bright output corrected.

FIG. 4 shows another embodiment of the present invention.
Instead of the flat plate 18, a rectangular column 28 made of glass or the like can be inserted in the optical path. In addition, square pillar 2
8 can be inserted such that its longitudinal direction is along the scanning direction of the scanning light. In the rectangular column 28, at least a first surface 28a and a second surface 28b through which an optical path penetrates are formed parallel to each other, and the first surface 28a forms an angle α (α
Is less than 90 degrees) and can be inserted at an angle. Therefore, when the scanning light from the light source is incident on the first surface 28a and when the scanning light passing through the rectangular column 28 is emitted on the second surface 28b, it is refracted twice to enter the scanning light. The scanning light beam emitted with respect to the light beam can be shifted in parallel to the direction orthogonal to the main scanning direction.
The shift amount is determined by the refractive index of the rectangular column 28 and the angle α. According to this embodiment, the scanning light beam emitted from the rectangular column 28 is parallel to the incident scanning beam, so that the deviation amount in the sub-scanning direction can be made constant regardless of the distance between the platen glass 5 and the rectangular column 28. The advantage is that it is not necessary to make the design of the insertion position of the rectangular column 28 strict. Since other configurations are similar to those of the embodiment of FIG. 1, detailed description will be omitted by giving the same reference numerals to the same components.

FIG. 5 shows another embodiment of the present invention.
Wedge-shaped column 3 made of glass or the like instead of the flat plate 18
8 can be inserted in the optical path. Further, the wedge-shaped column 38 can be inserted so that its longitudinal direction is along the scanning direction of the scanning light. The wedge-shaped column 38 is formed such that extension surfaces of the first surface 38a and the second surface 38b through which the optical path penetrates overlap with each other at an angle β (β is several degrees), and the first surface 38a with respect to the optical path. Can be inserted at 90 degrees. Therefore, the scanning light from the light source is emitted from the first surface 38a.
Incident on the first surface 38a, the light ray goes straight on
By being refracted at the surface 38b when it is emitted, the scanning light beam emitted with respect to the incident scanning light beam can be bent in a direction orthogonal to the main scanning direction. The amount of bending is
It is determined by the refractive index of the wedge-shaped column 38 and the angle β.

In each of the above-mentioned embodiments, the structure for obtaining the white reference signal is used. However, if the black belt-like portion is formed on the platen glass 5 instead of the white belt-like portion 6, the black reference signal can be obtained. Further, in order to obtain the black reference signal with the structure of each of the above-described embodiments, if the image sensor is driven with the power of the laser diode 11 turned off before or after reading the white reference signal, light is incident on the band-shaped light receiving element 2. The black reference signal can be obtained because it is not.

In each of the above embodiments, the optical path changing member (the plane plate 18, the rectangular column 28, the wedge column 3) made of glass is used.
Although 8) can be inserted in the middle of the optical path, a metal, ceramics, or the like can be used as long as it is a member having an optically reflective or refracting property such as plastic. In each of the above embodiments, the optical path changing member is the f-θ lens 1.
5 can be inserted between the half mirror 16 and the half mirror 16, but it may be arranged anywhere between the document surface and the light source.

[0023]

According to the present invention, by allowing the optical path changing member to be inserted in the optical path from the light source to the original surface, the scanning light beam can be moved in the scanning direction by utilizing the total reflection or refraction of the optical path changing member. About the light receiving element by shifting in the orthogonal direction, irradiating the white or black band-shaped portion formed on the platen glass surface with this totally reflected or refracted light beam and making the reflected light from the white or black band-shaped portion incident on the band-shaped light receiving element White or black reference signal can be obtained. Therefore, a white or black reference signal can be obtained with a desired pixel density with a simple structure, and a reference signal for the entire document surface can be obtained, and accurate correction is performed for each pixel density in reading by the optical scanning image sensor. be able to.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of an optical system of an optical scanning type image sensor according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating the overall configuration of an optical scanning image sensor according to an embodiment.

FIG. 3 is a cross-sectional explanatory view of a strip-shaped light receiving element of an example.

FIG. 4 is a structural explanatory view of an optical system of an optical scanning image sensor according to another embodiment.

FIG. 5 is a structural explanatory diagram of an optical system of an optical scanning image sensor according to another embodiment.

6A and 6B are diagrams for explaining the light amount in the scanning direction of the optical scanning type image sensor, FIG. 6A is an explanatory view of a cross section of the image sensor, and FIG. 6B is a graph showing a light amount distribution according to a sensor position.

FIG. 7 is a perspective explanatory view showing a configuration of a conventional optical scanning image sensor.

[Explanation of symbols]

1 ... Scanning optical system, 2 ... Band-shaped light receiving element, 3 ... Optical system,
4 ... Original surface, 5 ... Platen glass, 6 ... White band portion, 8 ... Integrator, 9 ... Operation circuit, 11 ... Laser diode, 12 ... Collimating lens, 13 ... Cylindrical lens, 14 ... Polygon mirror, 15 ... f
-Θ lens, 16 ... Half mirror, 17 ... Cylindrical lens, 18 ... Plane plate, 19 ... Optical path direction changing mechanism, 21 ... Insulating substrate, 22 ... Lower electrode, 23 ... Photoelectric conversion layer, 24 ... Upper electrode, 28 ... Square Pillar, 38 ... Wedge-shaped pillar

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H04N 1/028 Z 9070-5C

Claims (1)

[Claims] 1. A light source for irradiating a document surface with light, a scanning means for scanning the light from the light source on the document surface, a strip-shaped light receiving element for receiving reflected light from the document surface, and a document surface. In an image sensor including a platen glass interposed between a band-shaped light receiving element, a white or black band-shaped portion having a width substantially equal to the document width is formed at a position parallel to the optical scanning line on the platen glass surface, An optical path direction changing mechanism that allows an optical path changing member to be inserted in the optical path from the light source to the document surface is provided, and the optical path changing member reflects or refracts light to shift the light beam in a direction orthogonal to the scanning direction. An optical scanning type image sensor having.