JPS63278284A - Two-dimensional light-position detection device - Google Patents

Abstract

PURPOSE:To form a simply constituted two-dimensional light-position detection device which can obtain a big output voltage in proportion to a position of the incident light by forming a photoconductive film between a square transparent resistive film which is equipped with input electrodes at two sets of opposite edge parts at right angles to each other and a common output electrode composed of a conductive film formed directly on an insulating substrate. CONSTITUTION:Out of two sets of facing input electrodes on a detection device 1 by keeping a distance X0 and another distance Y0, one set, i.e., the electrodes 6a, 6c as grounding electrodes to a negative side of a power supply 82 and the other electrodes 6b, 6d are connected to a positive side via a switch S1. If this switch is changed over, an input voltage V0 is impressed on the input electrode 6b for X- coordinates use and on the input electrode 6d for Y-coordinates use alternately. If a luminous spot is incident on a point P inside a detection region in this state, a photoconductive film 4 becomes conductive in this point; a common output electrode 3 formed as a lower layer is connected to a transparent resistive film 5 on the surface via the conductive part; output voltages Vx, Vy in proportion to x, y are generated between the grounding electrodes and the common output electrode 2 synchronously with a changeover cycle of the switch. The signals are separated into two systems by using a switch S2 and can be taken out easily as independent signals.

Description

[Detailed Description of the Invention] [Summary] Light is transmitted between two sets of orthogonal rectangular transparent resistive films with input electrodes on opposing edges and an output electrode of a conductive film formed on an insulating substrate. This is a two-dimensional optical position detection device in which a conductive photoconductive film is formed and the X and Y coordinates of a light spot irradiated are extracted as an output voltage of a potentiometer.

[Industrial application field]

The present invention relates to a two-dimensional optical position detection device using a photoconductive film.

A detection device that determines the position coordinates of a light spot on a plane is
It is used as a detection means in a measuring device that measures the spatial position coordinates of an object to be measured in contact with it and performs motion analysis of a moving object.

Recently, there has been an increasing demand for this type of detection device that has a large output and can be used with a simple detection circuit, such as a digitizer that converts the coordinates of drawings etc. into electrical signals and inputs them into a computer system.

[Conventional technology]

2. Description of the Related Art Conventionally, optical two-dimensional position detection devices that use the photovoltaic effect of semiconductors are known.

First, the principle of operation will be explained with reference to a schematic cross-sectional view of a conventional one-dimensional optical position detection device shown in FIG.

In FIG. 4, a uniform resistance layer 92 made of P-type silicon is formed on a high-resistance semiconductor substrate (silicon) 91, and a pair of electrodes 93a and 93b for signal extraction are provided at both ends of the resistance layer 92. It is also provided with silicon 9
A common electrode 94 made of an n-soil layer is formed on the lower surface of the substrate 1 .

The bonding surface between the silicon 91 and the resistance layer 92 is a PN junction,
forming a photovoltaic cell.

Let the distance between both electrodes 93a and 93b be, and let the resistance be RL,
Let X be the distance from the electrode 93a to the point of incidence of the light spot l-H, and let Rx be the resistance of that portion. The photogenerated charge generated at the light incident position is a photocurrent I that is proportional to the incident energy of the light.
It reaches the resistance layer 92 as O, and is divided inversely proportional to the resistance value to each electrode, and is divided into electrodes 93a and 93b.
taken from.

Let these currents be Ia and Ib, respectively. Assuming that the resistance layer 92 is uniform and its length and resistance value are proportional, the above equation can be expressed as follows. When calculating the Ia and IbO ratio, it becomes Ia
, the incident position of light can be known from the IbO value regardless of the incident energy.

FIG. 5 is a diagram showing a conventional two-dimensional optical position detection device for performing two-dimensional measurement using the above principle.

In the figure, on a resistance layer 92 formed in a rectangular planar shape, X1X', Y, and Y' electrodes are provided on each of the four sides corresponding to the orthogonal coordinate axes. Although the above description has been made for a one-dimensional case having only the X axis, in a two-dimensional case where the electrodes are arranged in this manner, the photocurrent IO due to the incident spot light is divided and flows into the four electrodes. The value of these currents changes depending on the distance between the point of incidence and the electrode.
In other words, since it contains position information, two sets of output current pairs Ix, lx' and Iy, Iy from opposing electrodes
By performing calculations in each pair using ', it is possible to detect the X and Y coordinates of the point of incidence of the light spot.

[Problem that the invention seeks to solve]

In the conventional detection device described above, the energy of incident light is converted into a current by the photovoltaic effect and used as an output signal. The photocurrent is usually extremely weak, on the order of several tens of nanoamps.
A highly sensitive preamplifier was required to perform subsequent calculations.

In addition, although the output current includes information about the position, the current value itself is not proportional to the position, so it is necessary to perform complex arithmetic processing to convert it into a value proportional to the position. Since this directly affects the output current, normalization processing is also required.

These processes include, for example, calculating the difference and sum of outputs from opposing electrodes and calculating the ratio.
This calculation required an analog calculation system that performs addition, subtraction, and division for the X and Y axes.

As described above, the conventional two-dimensional optical position detection device using a semiconductor has the problem that the signal processing circuit becomes complicated and the device becomes large-scale and expensive.

[Means for solving problems]

FIG. 1 is a plan view of a two-dimensional optical position detection device according to the present invention;
FIG. 2 is a sectional view taken along the line AA' in FIG.

In order to solve the above-mentioned problems, the present invention uses a rectangular transparent resistive film 5 having input electrodes 6a, 6b and 6c, 6d on two sets of orthogonal opposing edges, and a conductive film formed directly above an insulating substrate. A two-dimensional optical position detection device is provided in which a photoconductive film 4 is formed between a common output electrode 3 and a common output electrode 3.

[Function] The resistance value of the photoconductive film 4 in the absence of light irradiation (dark resistance)
It is a highly insulating material, and when irradiated with light, its resistance value (bright resistance) decreases by 5 to 7 orders of magnitude, indicating conductivity.

Therefore, as shown in FIG. 2, when the spot light H is incident on the surface of the detection device configured as described above, it passes through the transparent resistive film 5 and reaches the photoconductive film 4 in the lower layer, and the spot light H passes through the transparent resistive film 5 and reaches the photoconductive film 4 in the lower layer.
a, the transparent resistive film 5 and the common output electrode 3 at the bottom layer are connected.

By the way, an input voltage is applied between opposing input electrodes on the transparent resistive film 5 (for example, between 6a and 6b), and a current flows. Since the transparent resistive film has a uniform resistivity distribution over the entire surface, a voltage drop occurs inside the transparent resistive film in proportion to the distance from the electrode.

That is, each point on the transparent resistive film wheel has a potential proportional to the distance from the electrode.

When the spot light H enters in this state, the conductive portion 4a
The potential at the point of incidence appears on the common output electrode 3 through.

That is, in this detection device shown in Fig. 2, the portion 4a irradiated with the spot light has the effect of extracting a voltage proportional to the position on the transparent resistive film +, that is, it is equivalent to a brush (slider) in a potentiometer. Therefore, a voltage proportional to the position of the incident point can be extracted from the common output electrode.

At this time, the resistance of the conductive part, which corresponds to the brush resistance, is about several hundred Ω, and it changes slightly depending on the intensity fluctuation of the spot light, but M
Since only the voltage is measured with a normal detection circuit having an input impedance on the order of Ω, the influence of resistance variation can be ignored.

Then, for example, the same input terminal is alternately applied between two sets of opposing electrodes for X-coordinate and Y-coordinate detection by switching with a switch, and the voltage from the common output electrode is synchronized with the switching timing of the switch. By dividing the system into two systems, position information regarding the two coordinate axes can be extracted separately in a time-sharing manner.

As described above, the two-dimensional optical position detection device according to the present invention using a photoconductive film can increase the non-contact potentiometer voltage in proportion to the input voltage supplied from the outside.
In addition, since the output voltage is proportional to the position of the incident light, there is no need for a preamplifier or a complicated analog calculation circuit as in the conventional detection device using the photovoltaic effect of the semiconductor.

〔Example〕

The present invention will be explained in detail below with reference to the accompanying drawings.

FIG. 1 is a plan view of a two-dimensional optical position detection device according to the present invention;
FIG. 2 is a sectional view taken along the line A-A'' in FIG. 1, and FIG. 3 is a detection circuit connection diagram.

In FIGS. 1 and 2, reference numeral 2 denotes an insulating substrate made of alumina or the like, on which a common output electrode 3 made of a conductive thin film such as NiCr-Au is formed.

On top of that, a thickness of 1 mm containing Cd (SeS) etc. as the main component is added.
A photoconductive film 4 with a thickness of ~4 μm and a layer of SnO2, ITO, etc., which does not extend beyond the formation area of the photoconductive film 4, are in contact with the four sides (the figure shows the top surface, but the end surfaces may also be used) and are perpendicular to each other. Two pairs of input electrodes 6a, 6b and 6c, 6d
are arranged by patterning a conductive film such as NiCr-Au, and are used as electrodes for the X and Y coordinates, respectively.

The lengths of the manual electrodes 6a, 6b, 6c, and 6d are determined in order to eliminate nonlinearity of the potential gradient within the resistive film (due to edge effect) due to the presence of electrodes for other orthogonal coordinate axes on the transparent resistive film. , is set to be appropriately short compared to the distance between the electrode pairs for other coordinates.

The area 7 surrounded by the dotted line in the figure shows the detection area of the optical sensor of the detection device formed as described above, and inside this area, x,
In both the y direction, the relationship between the coordinates of the incident position of the light spot and the output voltage maintains linearity.

Next, with reference to FIG. 3, the operation of the two-dimensional optical position detection device configured as described above will be explained.

In the figure, reference numeral 8 denotes a detection circuit, which includes a coordinate axis switching circuit 81 consisting of two sets of interlocking changeover switches Sl and S2, and a power source 82 for supplying an input voltage VO to the detection device 1.

2 facing each other at distances XO and YO on the detection device 1
One of each pair of input electrodes 6a, 6c is connected to the negative side of the power supply 82 as a ground electrode, and the other one 6. b and 6d are connected to the positive side via switch Sl, and by switching the switch, the input voltage vO becomes
The voltage is applied alternately to the coordinate input electrode 6b and the Y coordinate input electrode 6d.

In this state, when a light spot enters a point P within the detection area (a point where the distances in the X and Y directions from the ground electrode are x and y, respectively), the photoconductive film becomes conductive at that point and is formed as a lower layer. The common output electrode 2 is connected to the transparent resistive film on the surface through the conductive part, and the output voltage v×, Vy proportional to x, y is applied between the ground electrode and the common output electrode 2 at the switching period of the switch. occur alternately in sync with This signal can be separated into two systems by a switch S2 operating in synchronization with the switch Sl, and can be easily taken out as two independent outputs.

〔Effect of the invention〕

According to the present invention, it is possible to provide a two-dimensional optical position detection device with a simple structure that can obtain a large output voltage proportional to the position of incident light, and the detection circuit can have a simple configuration. Its economic effects are significant.

[Brief explanation of drawings]

FIG. 1 is a plan view of a two-dimensional optical position detection device according to the present invention, FIG. 2 is a sectional view taken along line A-A'' in FIG. 1, and FIG.
Detection circuit connection diagram: FIG. 4 is a schematic diagram of a conventional one-dimensional optical position detection device; FIG. 5 is a diagram showing a conventional two-dimensional optical position detection device. In the figure, 1-two-dimensional optical position detection device, 2-insulating substrate, 3-common electrode, 4-photoconductive film, 4a-conducting part,
5-Transparent resistive film, 6a, 6b, 6c, 6cl--
Single power electrode, 7-detection area, 8-detection circuit,
81-coordinate axis switching circuit, 82-power supply, 9
1- silicon, 92- resistance layer, 93a,
93b - electrode, 94 - common electrode; 1st layer

Claims (1)

[Claims] On the insulating substrate (2), a common output electrode (
3), a photoconductive film (4), and a rectangular transparent resistive film (5) are sequentially formed in layers, and the edges of two opposing sides of the transparent resistive film (5) are perpendicular to the two sides. Two sets of input electrodes (6_a, 6_b) connected to the transparent resistive film (5) are connected to the edges of the other two sides.
and 6_c, 6_d), and the two sets of input electrodes (6_c, 6_d) are provided.
_a, 6_b and 6_c, 6_d), a light spot is irradiated on the detection area (7),
The light spot brings the photoconductive film (4) of the irradiation part into a conductive state, and the two sets of input electrodes (6_a, 6_b and 6_a) become conductive.
_c, 6_d) and a common output electrode (3) to determine the position of a light spot from the voltage value generated between the common output electrode (3).