JPS61255062A - Optical sensor array - Google Patents

Abstract

PURPOSE:To make a photoelectric transfer characteristic uniform across an entire copy reading area and thereby to make output signals uniform by a construction wherein semiconductor elements not conducting photoelectric trans fer are disposed at the both ends of an array of optical sensors which conduct the photoelectric transfer. CONSTITUTION:A plurality of photoelectric transfer elements composed of a photodiode 101 and a capacity 102 of the diode 101 are arranged in an optical sensor array, and these elements are connected to a start pulse input terminal 110 through the intermediary of buffer amplifiers 103 and switching elements 105 respectively. Each of these elements is constructed of an amorphous silicon 201, a transparent electrode 202 and metal electrodes 203 and 205 and is ar ranged on a straight line. Moreover, adiode 111 having the same construction of each elements and elements with a capacitor 112 of the diode 111 and conducting no photoelectric transfer are connected to the both ends of the optical sensor array respectively. Thus, the photoelectric transfer characteristic of the optical sensors is made uniform covering an entire copy reading area, and thereby output signals are made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an optical sensor array for reading a document in close contact with a document in a facsimile machine or the like.

[Conventional technology]

Conventionally, in the facsimile document reading section or image league, COD (Charge Coup
led 1) IC such as device (charge-coupled device)
The main method used was an image sensor. In this case, a document with a width exceeding 200wM can be handled with an I
A reduction optical system is always required for reading with a C image sensor, and this has been the main reason for preventing miniaturization of devices such as facsimiles and image readers. In close proximity.

In order to solve these problems, a method has been proposed in which a document is read using an optical sensor array that uses an amorphous semiconductor and has approximately the same size as the width of the document.

According to this method, the document and the optical sensor array can be used in close contact with each other, so that the apparatus can be significantly downsized.

FIG. 3 is a circuit configuration diagram showing a conventional optical sensor array.
(October 21, 1982).

In the figure, 101 is a photodiode made of hydrogen-containing amorphous silicon (a-8i) as an optical sensor, 102 is the capacitance of the photodiode 101, and 103
is a buffer amplifier with a gain of 1, 104 and 105 are switch elements, 106 is a start pulse input terminal, 107 is a clock input terminal, 108 is an output terminal, 109 is a power supply, 1
10 is a shift register.

FIG. 4 is a diagram showing the configuration of a photodiode in the circuit configuration of the original sensor array in FIG. 3, and FIG. 4(a)
and (b) show a plan view and a cross-sectional view of the photodiode 101, respectively. In each figure.

201 is amorphous silicon containing hydrogen, 202 is a transparent electrode, 203 is a metal electrode, and 204 is an insulating substrate, and the amorphous silicon 201 is sandwiched between the transparent electrode 202 and the metal electrode 203. The insulating substrate 24
well formed.

FIG. 5 is a timing diagram showing waveforms of various parts for explaining the operation of the circuit configuration of the optical sensor array of FIG. 3. FIG. In the figure, 501 is the input to the clock input terminal 107, 502 is the input to the start pulse input terminal 106, 503 is the Q1 output of the shift register 110, and 504
is the Q2 output of the shift register 110, 505 is the Q1728 output of the shift register 110, and 506 is the output terminal 10.
The waveforms of the outputs from 8 are shown.

Next, the operation of the circuit configuration of the optical sensor array shown in FIG. 3 will be described with reference to FIG. 5. First, the first
Attention will be paid to the th photodiode 101. The switch element 104 connected to the cathode side of the photodiode 101 is closed when the Q2 output 504 of the shift register 110 becomes H level, and the voltage v8 of the power supply 109 is applied to both ends of the photodiode 101. be done. At this time, the capacity of the photodiode 101 is 1
02 is charged with charge qo (=CdVs).

Next, the Q2 output 504 of the shift register 110 is set to L.
When the level is reached, the cathode side of the photodiode 101 is opened. On the other hand, light corresponding to the density of a read document (not shown) is input to the photodiode 101.
@3 The former electrical engineer flows in the direction shown by the arrow in Figure 3. Due to this light flow, the charges accumulated in the capacitor 102 are discharged. After the time T shown in FIG. 5 has elapsed in this state, the voltage V between the terminals of the photodiode 101 is expressed by the following equation.

When the Q1 output 503 of the shift register 110 becomes H level after the above-mentioned time T8 has elapsed, the switch element 105 connected to the output of the first buffer amplifier 103 is closed, and the output voltage v0 of the following equation is applied to the output terminal 108. is output to.

In the above item (2) 2, the former electrician is connected between the terminals of the photodiode 101 '1. Assuming that it does not depend on the voltage V, when the amount of light is constant, the above equation (2) becomes as follows, and the output voltage V. is proportional to the amount of light.

Therefore, if start pulses are input at regular intervals as shown in FIG.
The output voltage V corresponding to the above (3) 2. are output to the output terminal 108 in chronological order.

Next, the configuration of the photodiode 101 in the circuit configuration of the optical sensor array shown in FIG. 4 will be described in detail. The amorphous silicon 201 shown in FIG. 4(b) is a non-doped film, and constitutes the photodiode 101 using a Schottky barrier at the interface with the transparent electrode 202. Further, the amorphous silicon 201 is not separated into each bit, but is separated only by the metal electrode 203. In such a configuration, since the amorphous silicon 201 layer is not separated as described above, (1) the mask alignment f111f is significantly relaxed in the manufacturing process;
■While it has the advantage that passivation is easy because there are fewer four sides of amorphous silicon 201,
It also has drawbacks as described below. That is, the fourth
In the electric field vector 207 shown by the arrow in FIG. 2B, the electric field vector 207 at the end of the first photodiode 101 has a component parallel to the surface of the insulating substrate 204, unlike the other photodiodes 101. Electric lines of force have a "curvature". Photocarriers generated in the amorphous silicon 201 by each particle 206a, 206b, 2Q6c incident on a certain area of the metal electrode 203 are transferred to the insulating substrate 204.
Therefore, along the electric field vector 207, the transparent electrode 20
2 or toward the metal electrode 203. here,
Let d be the distance between the electrodes (thickness of the amorphous silicon 201).

The maximum value tm of carrier travel time is expressed by the following equation.

However, V is the carrier velocity and μ is the carrier mobility.

E is the electric field strength. Normally, in the region of terminal voltage v, > 1 volt, trn < τ (τ is carrier lifetime)
Therefore, since the one-dimensional electric current does not depend on the electric current voltage V, the above equation (3) holds true. However, for the photocoat generated by the element 206d that is incident on the region where there is no metal electrode 203, the distance between the electrodes! is the above d
y) becomes longer, the condition 1m<τ no longer holds true, and the following characteristics appear for the photodiodes 101 at both ends.

(1) Photocarriers generated in areas where there is no metal electrode 203 also contribute to the original current flow, so the light-receiving area is larger than that of other photodiodes.

(2) The original current flow caused by the photocarriers generated in the area where there is no metal electrode 203 has a large voltage dependence, and the output signal is no longer proportional to the intensity of the incident light.

[Problem that the invention seeks to solve]

In the conventional optical sensor array as described above, one of the many photodiodes 101 constituting the one-element sensor array is
Since the photoelectric conversion characteristics of the photodiodes 101 arranged at both ends are different from the photoelectric conversion characteristics of the other photodiodes 101, there is a problem in that output uniformity deteriorates in terms of performance.

The present invention has been made in order to solve such problems, and an object of the present invention is to obtain an original sensor array whose photoelectric conversion characteristics as an optical centimeter array are uniform over the entire reading area of a document.

[Means for solving problems]

The optical sensor array according to the present invention has dummy sensors that do not convert one element and are made of semiconductor elements having the same configuration as the optical sensor at both ends of a row of optical sensors that perform photoelectric conversion. It is.

[Effect]

In the optical sensor array of the present invention, by arranging semiconductor elements that do not perform photoelectric conversion at both ends of the row of original sensors that perform photoelectric conversion, an electric field is uniformly applied to all optical sensors that perform photoelectric conversion. Therefore, the output signal can be made uniform.

〔Example〕

FIG. 1 is a circuit configuration diagram showing an original sensor array which is an embodiment of the present invention, and each reference numeral 101 to 110 is the same as the conventional example shown in FIG. 3 above.

In the figure, 111 is a diode (semiconductor element) connected to the outside of each of the first and 1728th photodiodes 101, and 112 is a diode 11
It has a capacity of 1.

FIG. 2 is a diagram showing the configuration of photodiodes and diodes in the circuit configuration of the optical sensor array of FIG.
Figure 2 (a) and (bl) are photodiodes 1, respectively.
01 and a plan view and a cross-sectional view of the diode 111, each reference numeral 201 to 204, 206a to 206c, and 207 are the same as the conventional example shown in FIG. It is light. here,
The diode 111 has a transparent electrode 202. Amorphous silicon 2
01 and a metal electrode 205.

Next, the operation of the circuit configuration of the original sensor array shown in FIG. 1 will be described with reference to FIG. 2. The diode 111 has its cand side grounded, and its node side connected to the voltage V of the power supply 109 through the transparent electrode 202. Therefore, the circuit operation is exactly the same as the conventional example shown in FIG. 3 above. Since the configuration of the diode 111 is as shown in FIG. 2(b), a power source 1 is connected between the metal electrode 205 and the transparent electrode 202.
Therefore, the electric field vector 207 becomes as shown by the arrow in FIG. 2(b). As a result, the "curvature" of the electric lines of force observed in the conventional example is shifted to the end of the diode 111 where photoelectric conversion is not actually performed. For this reason, for all the bits of the optical sensor in the one-dimensional sensor array, the
) formula holds true, and as a result, uniform photoelectric conversion characteristics can be obtained.

In the above embodiment, a case has been described in which one diode 111 is provided at each end of the row of optical sensors, but a plurality of diodes 111 may be provided.

Further, in the above embodiment, the metal 1ya 205 and the metal electrode 20
Although the case where each size is the same as that of 3 is shown, it is not necessary to make each size the same.

〔Effect of the invention〕

As explained above, this invention has a configuration in which semiconductor elements that do not perform photoelectric conversion are arranged at both ends of a row of optical sensors that perform photoelectric conversion in the optical sensor array, so that the photoelectric conversion characteristics as a one-element sensor array are improved. This provides an excellent effect in that the reading area of the document is uniformly scanned over the entire reading area, and as a result, the output signal can be made uniform.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing a photosensor array that is an embodiment of the present invention, FIG. 2 is a diagram showing the configuration of photodiodes and diodes in the circuit configuration of the photosensor array shown in FIG. 1, and FIG. 4 is a circuit configuration diagram showing a conventional photosensor array, FIG. 4 is a diagram showing the configuration of a photodiode in the circuit configuration of the photosensor array shown in FIG. 3, and FIG.
FIG. 3 is a timing chart showing waveforms of various parts for explaining the operation of the circuit configuration of the optical sensor array shown in the figure. In the figure, 101...photodiode, 101
. 112... Capacity, 103... Buffer amplifier, 10
4゜105...Switch element, 106...Start pulse input terminal, 107...Clock input terminal, 10
8... Output terminal, 109... Power supply, 110... Shift register, ]11-... Diode, 20]...
・Amorphous silicon, 202...Transparent electrode, 203,2
05... Metal electrode, 204... Insulating substrate, 206
a to 206 d--light, 207... electric field vector. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (4)

[Claims] (1) In a photosensor array in which a plurality of photosensors consisting of a semiconductor material sandwiched between a transparent electrode and a metal electrode are arranged in a line, both ends of the row of photosensors perform photoelectric conversion. An optical sensor array characterized in that one or more semiconductor elements that do not perform photoelectric conversion and have the same configuration as the optical sensor are disposed. (2) The optical sensor array according to claim 1, wherein both the optical sensor and the semiconductor element are elements that utilize a Schottky barrier at the interface between the transparent electrode and the semiconductor material. . (3) Claim 1 or 2, wherein the semiconductor material is amorphous silicon containing hydrogen.
Optical sensor array described in Section 1. (4) The optical sensor array according to claim 2, wherein a bias voltage is constantly applied to the semiconductor element so that the Schottky barrier is reverse biased.