JPS60170254A - Original reading device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a document reading device. More specifically, the present invention relates to an improved document reading device that has improved reliability by eliminating the occurrence of failures in the contact type image sensor, which has made it possible to significantly reduce the size of the document reading device.

Conventional technology Contact image sensors have elements that are the same size as the original, so they read the original image by placing the element in close contact with the original or by one-to-one imaging using an optical system such as an optical fiber array or lens array. It is used for. Since a document reading device using a contact type image sensor can obtain a short imaging optical path length, it has an advantage in that it can be significantly miniaturized compared to a conventional MO8 type or CCD image sensor.

FIG. 1A shows an equivalent circuit diagram of a conventional contact type image sensor, FIG.

A document reading device using a contact image sensor (hereinafter simply referred to as a sensor in this specification) converts the amount of light incident on a light receiving element into an electric current, and detects the resulting current at an output terminal to obtain optical information. As shown in FIG. 1(a), the light receiving element (5)
is formed by a photodiode PPD and a capacitor CD, and is provided with a density necessary for resolving the document, for example, 8/dragon arranged in a row.

In addition, in FIGS. 1(b) and (C), the light receiving element (5) is made of an amorphous material such as Se-As-Te or a-8i:H, or a polycrystalline material such as CdS or CdSe. Above and below the conductive semiconductor thin film (3) are lower electrodes (2) made of conductive thin films of At, Au, Cr, etc., and SnO2+ ITO.
It is formed on a single substrate (1) in a sandwich-like manner with a continuous upper layer electrode (4) consisting of a transparent conductive thin film such as.

)□□□-I- The above sensor also has a clock start pulse input terminal (9a) for operating the shift register (8).
), (9b), power supply terminals (9c), (9d) of the drive circuit (6) constituted by a shift register (8) and a MOS transistor (7), and a signal output terminal (9e) from which optical information is read. ) and a bias terminal (9f) for applying a bias voltage to the light receiving element (5).

Further, the circuit unit 00) that drives the sensor has a built-in power supply Qll, (12), a noise generator (13), and an amplifier circle, respectively, and when testing the sensor, Each terminal (9a-f) is connected to the circuit unit (10). On the other hand, during storage without testing, the above sensor is in circuit unit 00).
Therefore, each terminal (9a=f) becomes electrically unstable, and the potential fluctuates greatly due to static electricity or the like. For example, when holding the device by hand for transportation, etc., or putting it in and out of a storage case, etc., there is a high risk that high voltage due to static electricity or the like will be applied. The drive circuit (6) part is made of MOS IC, and the terminals (9a=e) are protected by diodes between the IC substrates to prevent the elements from being destroyed by the application of the high voltage. There is. However, since the light-receiving element (5) is formed of an ordinary thin film, it has a fatal flaw in that the element (5) is destroyed by the application of the above-mentioned high voltage, which poses a major problem. was.

OBJECTS OF THE INVENTION An object of the present invention is to provide an improved document reading device that eliminates the drawbacks of the above-mentioned prior art and eliminates the occurrence of failures.

Structure of the Invention That is, the above-mentioned object of the present invention (d) In a document reading device comprising a plurality of lower layer electrodes provided on a substrate, and a photoconductor and a transparent conductive upper layer electrode sequentially provided thereon, the lower layer electrodes This is achieved by a document reading device characterized in that the upper layer electrode and the upper layer electrode are connected by a resistor or a diode to prevent high voltage from being applied to both electrodes. The above object is achieved by providing a resistor or diode to limit or release the applied voltage.

EXAMPLE Hereinafter, an example of the implementation of the present invention will be explained in detail with reference to the drawings.

FIGS. 2(a) and 2(b) show circuits and configurations of a contact type image sensor according to the present invention, respectively.

The present invention uses the wiring (17a) and (17b) to connect the terminal (9d) of the driving circuit (6) and the terminal ( 9f). In addition, a photodiode P is formed on a flat substrate (11) such as glass or ceramic by a method such as vapor deposition or photo-etching process.
the light receiving element (5) consisting of a capacitor CD and a capacitor CD;
The light-receiving element (5) is formed as an individual element and is connected to a drive circuit (6) including a MOS transistor (power and shift register (8)) mounted on the substrate (1) through connection means such as wire binding 0υ. connected to.

The sensor provided as described above discharges the charge collected in the capacitor CD by the photodiode (1'PD) according to the amount of light incident on the light receiving element (5), and also by the shift register (8). #) MOS that turns on sequentially) Run lister (
7) The capacitor CD is then recharged, and the current flowing at this time is detected at the output terminal (9e) and optical information is read out. In particular, as described in this embodiment, by inserting a shunt resistor (15) between the ground side terminals (9a) and lf) of the sensor, the lower electrode (
2) and the upper layer electrode (4) are electrically connected via the drive circuit (6) and the shunt resistor a9. Therefore, in a state where no external circuit is connected to the terminal (9a=f), , both of the cedars (2) and (4) are at the same potential, so no high voltage is applied to the light receiving element (5).

Note that the shunt resistor a can be formed by a thick film resistor or a chip resistor.

FIG. 3 shows a modification of the present invention, in which a diode (
16) has been inserted. Diode (16) like this
The same characteristics as in the first aspect of the present invention can be obtained even by inserting the above.

Effects of the Invention As described above, according to the present invention, by inserting a shunt resistor or diode between the output terminals of the contact type image sensor of a document reading device, high voltage can be applied during the manufacturing process or use of the sensor. This prevents the light-receiving element from being destroyed, which greatly improves reliability. Further, according to the present invention, by simply inserting a shunt resistor or diode, it is possible to prevent destruction of the light receiving element without changing the circuit and size of the conventional contact type image sensor.

[Brief explanation of drawings]

FIGS. 1(a), (b), and (c) are a circuit diagram, a planar configuration diagram, and a vertical sectional view of a conventional contact-type image sensor, and FIGS. 2(a) and (b) are an embodiment of the present invention. Circuit diagram and plan configuration diagram illustrating a contact type image sensor by
The figure is a circuit diagram showing a modification of the present invention. Symbols in the figure: 1...Substrate 2...Lower layer electrode 3...Photoconductive semiconductor thin film 4...Upper layer electrode 5...
- Light receiving element 6... Rough dividing circuit 9a to 9f... Output terminal 15... Shunt resistor 16.
...Diode agent patent attorney (8107) Kiyotaka Sasaki (and 6 others)

Claims (1)

[Claims] In an original reading device in which a plurality of lower layer electrodes are provided on a substrate, and a photoconductor and a transparent conductive upper layer electrode are sequentially provided thereon, the lower layer electrodes and the upper layer electrode are connected by a resistor or a diode. A document reading device characterized in that a high voltage is prevented from being applied to both electrodes.