JPH027547B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an image reading device, and particularly to a two-dimensional image reading device in which sensor elements are arranged two-dimensionally.

<Prior Art> To date, MOS type image sensors, CCD sensors, contact type image sensors, etc. have been proposed as devices for reading out images of facsimiles and the like. M.O.S.
A type image sensor is a device that converts an incident light image into an electric signal using a photoelectric conversion element, and reads it out by sequentially switching MOS transistors to scan it.A CCD sensor converts an incident light image into an electric signal using a photoelectric conversion element, and reads it out by sequentially switching MOS transistors to scan it.A CCD sensor converts an incident light image into an electric signal using a photoelectric conversion element. This is a device that uses a device (CCD) to transfer data.

Both the MOS type image sensor and the CCD sensor are fabricated using IC technology using a single crystal semiconductor as a substrate. Therefore, manufacturing a sensor with a large area is disadvantageous in terms of performance and cost, and an optical lens is generally used to form a reduced image of the document on the sensor. However, since this method uses an optical lens, the optical path length becomes long, making it difficult to miniaturize the device.

In order to miniaturize the device for the above-mentioned reduction image forming type image sensor, a photoelectric conversion element of the same size as the original is used and an optical fiber is used to form an image of the same size as the original onto the photoelectric conversion element. A close-contact image sensor has been devised. A contact image sensor usually requires a photoelectric conversion element of the same size as the original, which requires the formation of a uniform photoconductive film over a wide area.

Currently, a one-dimensional contact image sensor in which a CdS photoconductive layer is divided into islands has been proposed as a contact image sensor. However, this image sensor
Since the CdS photoconductive layer is divided, the structure is complicated and problems remain in terms of the manufacturing process. Furthermore, the reading speed is limited by the photoresponse speed of the photoconductive layer. In particular, photoconductive layers such as CdS have problems with photoresponse speed.
If an attempt is made to read two-dimensional image information using a one-dimensional image sensor, the one-dimensional sensor must be used repeatedly, which imposes considerable limitations.
Another drawback is that it is difficult to integrate the photoelectric conversion section and the switching element using IC technology, as in the case of a MOS type sensor or a CCD sensor, and the cost of the drive circuit becomes relatively high. Although MOS type sensors and CCD sensors have already been put into practical use, contact type sensors have not yet reached practical use due to the reasons mentioned above.

Furthermore, a close-contact sensor using a continuous band-shaped photoconductor made of amorphous silicon or the like has been proposed, but it is possible to use such a one-dimensional sensor to
If you want to read a dimensional image, you have to use the sensor repeatedly, and for that purpose, voltage is applied to the same sensor part at a certain period and the signal is read, so the current changes as the illuminance changes between "bright" and "dark". The increase or decrease of , that is, the falling characteristic, directly affects the signal. Therefore, in the above one-dimensional sensor, 1
The time required to scan a line must be longer than the response speed, which increases the time required to read a two-dimensional document, which poses a problem for practical use as a two-dimensional image sensor.

<Objective of the Invention> The present invention has been made in view of the above-mentioned problems of the conventional image sensor. The present invention provides a device that can perform high-speed reading regardless of the situation, and is a reading device that can be used not only as a contact type image sensor but also as a two-dimensional image sensor using a normal optical system.

<Embodiment> FIG. 1 is a perspective view showing the structure of a sensor 1 in an image reading device according to an embodiment of the present invention. The sensor 1 has a substrate 2 made of an insulating plate such as glass having an area at least as large as the two-dimensional image plane to be read, and a striped X electrode 3 formed by vapor-depositing Al or the like on one surface of the substrate 2. They are arranged parallel to each other at a constant pitch. The width and pitch of each X electrode 3 affects the resolution of the sensor 1. The above X electrode 3
are connected to the scanning circuit 4, and are sequentially selected and a voltage for reading is applied. A photoconductive layer 5 is formed over the substrate on which the X electrode 3 is formed. The photoconductive layer 5 is made by mixing and dispersing photoconductive powder mainly composed of CdS in a resin, and is formed to cover the substrate 2 and have a uniform thickness over almost the entire two-dimensional reading plane. The resistance of the CdS photoconductive layer is set to a value of 10 ⁸ Ωcm or more, which is high enough to maintain charge. In addition, the film thickness is determined by the charging voltage (500 V ~ in the dark)
The photoreceptor is designed to have a thickness (20 to 50μ) that does not cause dielectric breakdown when exposed to a voltage of 600 V), and is designed so that its characteristics do not change due to corona discharge.
A photoconductive layer that can be used in photoreceptors commonly used in copying machines and the like is used. A corona discharger 6 is placed opposite the photoconductive layer 5 formed into a planar shape. The corona wire 7 of the corona discharger 6 is connected to a high voltage generating circuit to charge the surface of the photoconductive layer 5, and is stretched in the Y direction perpendicular to the X direction in which the X electrode 3 extends, and A shield plate 8 covering the wire 7 has a slit 9 for exposing the surface of the photoconductive layer 5 to an image.

FIG. 2 is a schematic diagram showing a reading device using a sensor 1 equipped with a corona discharger 6. In addition to the sensor 1, an optical system 10 for guiding image information to the slit 9 of the corona discharger 6 is arranged. ing. The optical system 10 includes a fiber optic lens 11 facing the slit 9 and a light source 13 including a reflector for making reflected light from the original 12 incident on the lens 11.
It is composed of. The optical system 10 and the corona discharger 6 move at a predetermined speed in the X direction to scan the two-dimensional plane of the original 12 with respect to the sensor 1 and the original 12 which are stationary.

Here, the surface of the photoconductive layer 5 is scanned over the entire area by the movement of the optical system 10 and the corona discharger 6 and the scanning of the X electrode 3. To enable this scanning, the X The scanning speed of the electrodes 3 is designed to be at least M times the moving speed of the optical system 10 and the corona discharger 6 (M: X number of electrodes).

In the reading device having the above structure, the image reading operation is performed by making the image of the original 12 enter the sensor 1 surface through the slit 9 of the corona discharger 6 through the optical system 10 and exposing the image. Simultaneously with this image exposure, a high voltage is applied to the corona wire 7 to apply charges to the surface of the photoconductive layer 5. The scanning circuit 4 is activated while the photoconductive layer 5 is being charged with a corona discharger 6 or while the charge applied to the surface of the photoconductive layer 5 does not significantly attenuate.
A voltage is applied to the X electrode group by sequentially switching the X electrode group so as to make at least one round. If the photoconductive layer 5 is irradiated with light, conductivity corresponding to the light intensity is generated, and the charges charged on the surface can be detected by the X electrode 3 below the light irradiation point, resulting in photoconductivity corresponding to the brightness and darkness of the incident image. The optical output current of the layer is read out to form an image signal for one line exposed to the slit. At this time, by performing corona discharge at the same time as exposure, a larger current can be extracted, and the brightness ratio of the output signal increases. Further, even if the surface of the photoconductive layer is charged in advance by corona discharge and then imagewise exposed, the S/N ratio will be lower than in the case of simultaneous exposure, but brightness and darkness can be sufficiently distinguished. After reading one line in the Y direction, the corona discharger 6 and the optical system 10 are moved in the X direction, and the next line of document image is irradiated onto the surface of the photoconductive layer to which corona discharge has been applied, and the same operation as described above is performed. The optical output current is taken out to the output terminal by the output terminal and used as an image reading signal.

8 lines/mm as a device for reading A4 size documents
Two-dimensional sensor (320mm x 230mm,
8 electrodes/mm, 1840 electrodes) were created. The two-dimensional sensor was scanned with the X electrode at a frequency of 4MHz, the optical system moved at a speed of 300mm/sec, and
When a voltage of -6KV was applied to a corona wire with a diameter of
It was possible to read with a sufficient S/N ratio in a time of 0.5 msec/line). In the case of a one-dimensional sensor using a photoconductive layer made of the same material, a time of at least 10 msec/line is required to obtain the same S/N ratio or resolution as the reading device to which the present invention is applied. It takes about 30 seconds to scan an A4 size document.

In addition to the above examples, amorphous amorphous can be used as the photoconductive layer.
It can also be carried out using a photoconductor such as Si or an organic semiconductor. In addition, in the case of an amorphous Se photoconductive layer, instead of moving the optical system, the original and Even if the sensors are moved in conjunction with each other in the Y direction, it can be carried out in exactly the same way.

<Effects> As described above, according to the present invention, two-dimensional
It is possible to read dimensional images, the structure of the device is very simple, and it can also be configured as a close-contact type using an optical fiber lens or the like, making it possible to reduce the size and weight of the reading device. In addition, the sensor section is formed two-dimensionally, and the influence of the photoresponse characteristics is reduced by sequentially moving the position of the photoelectric conversion section that reads the image, so it can support high-speed reading operations regardless of the photoresponsiveness. It can be used as a terminal for various electronic devices.

Furthermore, one surface of the photoconductive layer is charged by corona discharge, and exposure and signal reading are performed at the same time, so there is no need to form electrodes on both sides of the photoconductive layer, and it is also possible to read out signals. There is no need to irradiate light for reading.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a sensor section of an embodiment according to the present invention, and FIG. 2 is a side view showing an overview of the entire embodiment. 1: Sensor, 3: X electrode, 4: Scanning circuit, 5:
Photoconductive layer, 6: Corona discharger, 9: Slit, 1
0: optical system, 12: manuscript.

Claims (1)

[Claims] 1. An insulating substrate, an electrode on which a plurality of conductors are formed in parallel to each other, a photoconductive layer integrally formed to cover the electrode surface, and the photoconductive layer. a corona discharger equipped with an exposure slit in which the direction of a corona wire for charging the layer is perpendicular to the parallel direction of the electrode; and an optical system that guides an image to the photoconductive layer through the exposure slit. and a circuit that sequentially switches and scans the electrodes, and a mechanism that moves the corona discharger and the optical system relative to the photoconductive layer along a direction parallel to the electrodes, A two-dimensional image reading device characterized in that corona discharge is performed at the same time as image exposure is performed, and the scanning circuit sequentially switches the electrodes to derive a read signal.