JPH029499B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to an image reading device, and more particularly to a two-dimensional image reading device in which sensor elements are arranged two-dimensionally and a sensor surface is scanned optically and electrically.

<Prior Art> Conventionally, in devices such as facsimiles, MOS type image sensors, CCD sensors, contact type image sensors, etc. have been proposed as devices for reading out images. A MOS image sensor is a device that converts an incident light image into an electrical signal using a photoelectric conversion element, and switches and scans it using a MOS IC.A CCD sensor converts the electric charge generated in the photoelectric conversion unit by light into a charge-coupled device (CCD).
This is a device that uses .

This MOS type image sensor or CCD sensor is based on a single crystal substrate and is created using IC technology on this substrate, so manufacturing a sensor with a large area is disadvantageous in terms of performance and cost. . Therefore, 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 contrast to the reduction image sensor described above, a contact image sensor uses a sensor the same size as the original and uses optical fibers to form an image of the same size as the original in order to miniaturize the device. It has been devised. A contact image sensor requires a photoelectric conversion unit that is the same size as the original, and requires the formation of a uniform 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. Each electrode must be provided, the structure is complicated, and the reading speed is limited by the photoresponse speed of the photoconductive layer.
In particular, photoconductive layers such as CdS have a problem with photoresponse speed, and are severely limited as one-dimensional image sensors.

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 change in the rising and falling characteristics directly affects the signal. Therefore, in the one-dimensional sensor described above, it is necessary to take a time longer than the response speed to scan one line, and the time required to read a two-dimensional original becomes long, which poses a problem for practical use as an image sensor.

<Object of the Invention> The present invention has been made in view of the above-mentioned problems with conventional image sensors, and uses an image sensor with a novel structure to scan the sensor surface optically and electrically to detect This is a two-dimensional image reading device that reduces the number of lead-out terminals, 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. be.

<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 includes an insulating plate made of glass or the like having at least the same area as the two-dimensional image plane to be read on a substrate 2.
On one surface of the substrate 2, striped X electrodes 3 formed by vapor-depositing Al or the like are provided in parallel at a constant pitch. Although the width and pitch of each X electrode 3 affect the resolution of the sensor 1, it is desirable that the width and pitch be as fine as possible within the range allowed by the light output characteristics exhibited by a photoconductive layer having a desired thickness, which will be described later. A photoconductive layer 4 is formed over the substrate 2 on which the X electrode 3 is formed.
The photoconductive layer 4 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 the entire two-dimensional reading plane. Further, Y electrodes 5 are formed on the photoconductive layer 4 in a direction perpendicular to the X electrodes 3 at approximately the same pitch. The Y electrode 5 is made of a transparent electrode material to enable image reading. In addition, when the substrate 2 is made of a transparent insulating material and the X electrode 3 is made of a transparent electrode material, the substrate 2 side is the image input side, and the Y electrode 5 is made of a metal film such as Al, polycrystalline silicon, etc. You can also do that.

In this example, a striped conductor is simply formed on the side of the X electrode 3 made of an Al film.
There is no special wiring between them.

On the other hand, the Y electrode 5 side of the transparent electrode is composed of n Y electrodes.
At least one electrode in the electrode group, for example, the first Y ₁
One electrode from the X electrode group during image reading operation.
Let the X _i electrode be the electrode for selection, and the remaining Y ₂ ~
The Y _o electrode is used to configure an image sensor in which sensor elements are arranged in a matrix. Therefore, a switching light source 6 (such as a light emitting diode) that lights up an area corresponding to the width of one X electrode is placed opposite to the _Y1 electrode for selecting the X electrode, and the _Y1 electrode itself is the load resistance 7
It is connected to one end of the power supply 8 via. The remaining Y ₂ -Y _o electrodes forming the sensor element are commonly connected to the other terminal of the power source 8 via scanning switching elements 9 ₂ -9 _o , respectively. Y ₂ ~ _{Y o} To guide the image information to the electrode surface,
An optical fiber array 10 is provided opposite to the Y ₂ -Y _o electrodes. The optical fiber array 10 is connected to the switching light source 6.
The X electrodes are formed integrally with each other in a straight line so as to face the same X electrode. The switching elements 9 ₂ to 9 _o
are sequentially switched by a signal applied from the scanning circuit 11, and the switching elements ₉₂ to _9o are switched at the speed of one cycle while the optical fiber array 10 is facing one X electrode. At this time, the terminals of the Y electrodes that are not connected to the power source are connected to the ground via the switching element.
The OUT terminal in the figure is a terminal for deriving a read output signal from the Y electrode.

FIG. 2 is a layout diagram showing the relationship between the image sensor 1 and the optical system. The optical fiber array 10, which is integrated with the switching light source 6 facing the sensor 1, receives the reflected light from the original 12 to form an image. A light source 13 is provided for inputting light as information and illuminating the surface of the document 12. Since the image sensor 1 has a two-dimensional area in which the original 12 can be read, the optical system 10 is fed by the drive mechanism 14 at a predetermined speed to scan the reading area with respect to the original 12 and the sensor 1. . Furthermore, optical system 10
The image sensor 1 side may be moved while being fixed.

Next, the operation of the two-dimensional image reading device having the above structure will be explained. The switching light source 6 is turned on with the optical fiber array 10 facing the X _i electrode of the X electrode group due to the feeding of the drive mechanism 14, so that the photoconductive light sandwiched between the X _i electrode and the Y ₁ electrode is turned on. Part 5 _i-1 of the layer becomes conductive. At the same time, reflected light from the original 12 is incident on the optical fiber array 10, and Y ₂ to _{Y o} facing the X _i electrode are incident on the optical fiber array 10.
An optical signal corresponding to image information is input to the electrode portion. At this time, the photoconductive layer between the Y ₁ and Y ₂ electrodes is irradiated with light, and the Y ₁ and Y ₂ electrodes are either shielded from light to prevent conduction between the Y ₁ and Y ₂ electrodes, or , remove the photoconductive layer between the _Y1 and _Y2 electrodes.
In this state, the switching elements 9 ₂ to 9 _o connected to the Y ₂ to _{Y o} electrodes are sequentially turned on for a certain period of time by the signal from the scanning circuit 11, so that the Y Regarding _{the l} electrode, the photoconductive layer portion _5il under the _Yl electrode becomes conductive. The photoconductive layer portion 5 _il is electrically coupled to the photoconductive layer portion 5 i-1, which is in a conductive state by the switching light source 6, by the X _i electrode, and the power source 8 is connected to the photoconductive layer portion 5 _i-1 . Since this voltage is applied, an electric circuit is formed from the output terminal OUT, and an image reading signal is output. By switching the switching elements ₉₂ to _9o , the image on the i-th X electrode can be read, and by sequentially switching the X electrodes and performing the same operation as the optical system moves, the entire image can be read. A signal can be obtained from the output of the two-dimensional sensor 1. Also, switching element 9 ₂
The crosstalk current can be minimized by connecting the terminals of the Y electrodes other than those to which power is applied to the ground via ~ _9o .

8 lines/mm as a reading sensor for A4 document size
A two-dimensional image sensor with the number of electrodes was fabricated, and the reading operation was performed at an optical system movement speed of 100 mm/sec and a Y electrode switch frequency of 1.6 MHz. As a result, an A4 document could be read in about 3 seconds (about 1.2 msec/line) with a sufficient S/N ratio. same
In a conventional one-dimensional image sensor using CdS as a photoconductive layer, it was difficult to obtain an S/N ratio comparable to that of this embodiment at a speed of 50 msec/line or higher.

The photoconductive layer 4 is not limited to a resin-dispersed type using CdS or CdSe, and can also be used in an image sensor configured using amorphous Si, amorphous Se, an amorphous Se compound, an organic semiconductor, etc. in the same manner as in the above embodiment. Good results can be obtained.

<Effects> According to the present invention, in an image reading device in which sensor elements are arranged two-dimensionally, one of the X and Y electrodes sandwiching the photoconductive layer is optically switched, and the other is electrically switched. Since the entire two-dimensional sensor surface is scanned, the wiring for deriving the signals can be significantly simplified, and the optical switching means utilizes a photoconductive layer to form image reading signals. can be formed,
The configuration of the image reading device can be simplified,
It is possible to obtain an economically superior device with great practical value.

[Brief explanation of drawings]

FIG. 1 is a perspective view of essential parts of an embodiment according to the present invention;
FIG. 2 is an overall configuration diagram of the same embodiment. 1: Sensor, 2: Substrate, 3: X electrode, 4: Photoconductive layer, 5: Y electrode, 6: Switching light source, 9 ₂
~ _9o : Switching element, 10: Optical fiber array, 11: Scanning circuit, _Y1 : Y electrode for selecting X electrode.

Claims (1)

[Scope of Claims] 1. A photoconductive layer 4; X electrodes X ₁ to X _n formed of a plurality of conductors in parallel to each other on one surface of the photoconductive layer 4; and the other side of the photoconductive layer 4. A plurality of Y electrodes Y 1 to _{Y o} formed with a plurality of transparent conductors on the surface in a relationship orthogonal to the X electrodes X _{1 to} X _n , and relative movement along the Y electrodes Y ₁ to _{Y o} . a switching light source 6 for selecting the X electrodes X ₁ to X _n , which are provided to possibly face at least one electrode Y ₁ of the Y electrodes Y ₁ to Yo; and a switching light source 6 for selecting the X electrodes X ₁ to X _n ; at least one electrode Y ₁ of _o
scanning switches 9 ₂ - 9 _o connected to each of the other Y electrodes Y ₂ - _Yo except for the scanning switches 9 ₂ - 9 _o and the Y electrodes Y ₁ -
A power supply 8 connected between at least one electrode Y ₁ of Y _o and the Y electrodes Y _{1 -} movable relative to each other along the switching light source 6 along the Y electrodes Y ₁ -Y _o .
An optical system that guides image information to be read in a line along the X electrodes X ₁ to X _o , which are provided opposite to the other Y electrodes Y ₂ to Y _o excluding at least one electrode Y ₁ of the Y _o . 10, and the potential of the power source 8 is applied to the photoconductive layer portion 5 _i-1 selected by the switching light source ₆ and at least one electrode Y ₁ of the Y electrodes _Y 1 to Yo. A two-dimensional image reading device characterized in that the X electrodes X ₁ to _{X n} are selected by supplying a signal to one electrode Xi of the X electrodes X ₁ to X _n .