JPH04363607A - Two-dimensional light position detector - Google Patents

Abstract

PURPOSE:To obtain a two-dimensional light position detector which enables a position detection accuracy for a light incidence position to be improved. CONSTITUTION:A transparent resistance layer 3, a photovoltaic layer 4, and a first conductive layer 5 are laminated in sequence in a light position detector A. Two pair of crossing second conductive layers 2a-2d are provided at the transparent resistance layer 3. The transparent resistance layer 3 is constituted by a face-shaped resistance 32 and a thin-wire-shaped resistance 31 connecting between adjacent face-shaped resistances, thus enabling a position detection accuracy for a light incidence position to be improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a two-dimensional optical position detector for detecting the position of incidence of light.

0002

[Prior Art] In recent years, in order to detect the linear displacement of an object with high durability and reliability, position sensors using variable resistors that use electrical contact have been replaced with position sensors that emit radiation from a moving object or are reflected or transmitted by the moving object. A non-contact position sensor is used in which the light is received by an optical position detector having a resistive layer, and the displacement of the moving body is detected in a non-contact manner based on the light receiving position of the optical position detector. As such an optical position detector, for example, Japanese Patent Laid-Open No. 61-271413 and Japanese Patent Laid-open No. 63
There is one using an amorphous silicon semiconductor film as disclosed in Japanese Patent No. 32305 and the like. Such a conventional optical position detector will be described below with reference to the drawings.

FIG. 7(a) is a perspective view of a conventional optical position detector using an amorphous silicon semiconductor film, FIG. 7(b) is a cross-sectional view of the optical position detector taken along line O-O', and FIG. is a position sensor using a conventional optical position detector. below,
A conventional device will be explained using FIGS. 7 and 8.

In FIGS. 7(a) and 7(b), A is an optical position detector, 1 is a substrate, in this case a transparent plate glass, and 2a, 2b, 2c, and 2d are detection electrodes A.
3 is a transparent resistance layer formed of an indium tin oxide (ITO) film or a tin oxide (SnO2) film, and its four sides are sensing electrodes 2a, 2b. , 2c, and 2d are formed into a band shape by sputtering or vapor deposition.

4 is an amorphous silicon semiconductor (hereinafter referred to as
It is abbreviated as a-Si. ) photovoltaic layer, plasma CVD
A P layer, an I layer, and an N layer are deposited in this order on the transparent resistance layer 3 by a vapor deposition method such as a method to form a photovoltaic layer with a PIN structure. This is a conductive layer formed by vapor deposition on the detection area of the photovoltaic layer 4.

Next, in FIG. 8, 7 is a light source such as an LED, and a visible light source is usually used depending on the light-receiving sensitivity characteristics of the a-Si photovoltaic layer 4, and 8 is a hole 81 that allows light to pass through a part thereof. This is a two-dimensional moving plate having a two-dimensional moving plate, which is disposed between the light source 7 and the optical position detector A, and moves two-dimensionally over the optical position detector A.

Reference numeral 6 denotes a position detection circuit that outputs a position detection signal corresponding to the incident position of light on the X-Y orthogonal coordinates based on the output signal of the optical position detector A, and includes seven non-inverting amplifiers 61a to 61d. , 62a, 62c, 63, and a comparison amplifier 64 to which a reference voltage source 65 is connected.

Detection electrodes 2a, 2b, 2 of optical position detector A
c, 2d are non-inverting amplifiers 61a, 61b, 61c, 61
d, and the bias electrode 5 is connected to a bias potential (here, ground potential).

[0009] Also, one side of the outputs of the non-inverting amplifiers 61a and 61b (in this case, the output of 61a) is connected to the non-inverting amplifier 62a.
The output of the non-inverting amplifier 62a is connected to the inverting input of
It is output to the outside as a coordinate position output Vx. Also,
One side of the output of the non-inverting amplifiers 61c and 61d (here 6
1c) is connected to the inverting input of the non-inverting amplifier 62c, and the output of the non-inverting amplifier 62c is the Y-coordinate position output Vy.
is output externally as .

On the other hand, both the outputs of the non-inverting amplifiers 61a and 61b are connected to the inverting input of the non-inverting amplifier 63, and the output of the non-inverting amplifier 63 is connected to one input of the comparator amplifier 64. The reference voltage Vref of a reference voltage source 65 is connected to the other input of the reference voltage source 65, and the output of the comparison amplifier 64 is connected to the light source 7.

Next, the operation of this conventional example will be explained with reference to FIGS. 7 and 8. The light source 7 is driven by the comparator amplifier 64 to emit light, and a part of this light beam is transmitted to the two-dimensional moving plate 8.
The light passes through the hole 81 and enters the optical position detector A.

The incident light of this optical position detector A passes through the substrate 1 and the transparent resistance layer 3 and reaches the a-Si photovoltaic layer 4.
A part of it is further reflected by the bias electrode 5 and is again a-
It is returned to the Si photovoltaic layer 4. A photovoltaic force is generated in the a-Si photovoltaic layer 4 by this incident light flux, and a photocurrent I corresponding to the amount of incident light is generated.
Detection electrodes 2a, 2b and 2c, 2 provided at both ends thereof
Divided into d.

At this time, each branch photocurrent is Ia, Ib,
Ic, Id, the length between the detection electrodes 2 (light receiving length) is L
X (X-axis direction), LY (Y-axis direction), transparent resistance layer 3
, the distances from the detection electrodes 2b and 2d to the light incident position are x and y, respectively, and the resistance values of the transparent resistive layer 3 between them are Rx and Ry, then, for example, only the X coordinate of the X-Y coordinate Focusing on , the position x is given by the following equation 1.

[0014]

[Math 1]

The photocurrents Ia and Ib are converted into voltages by load resistors (resistance value R) in non-inverting amplifiers 61a and 61b, respectively, and become voltages Va and Vb, respectively, and these voltages V
a and Vb are added by a non-inverting amplifier 63, and the amount of light emitted from the light source 7 is controlled by a comparator amplifier 64 so that the added value (Va + Vb) becomes a predetermined reference voltage Vref.

On the other hand, the output of the non-inverting amplifier 61a is given a predetermined gain K by the non-inverting amplifier 62a, and the voltage V
Output as X. That is, Vx is expressed as shown in Equation 2 below.

[0017]

[Math 2]

The above equation 2 can be expressed as the following equation 3 from the above equation 1. Voltage Vx is X of optical position detector A
Corresponds to the incident position in the direction.

[0019]

[Math 3]

Similarly, the photocurrents Ic and Id are current-voltage converted by load resistors (resistance value R) in non-inverting amplifiers 61c and 61d, respectively, and become voltages Vc and Vd, respectively. The output of the non-inverting amplifier 61c is given a predetermined gain K by the non-inverting amplifier 62c and is output as a voltage Vy. This voltage Vy corresponds to the incident position of the optical position detector A in the Y direction.

Therefore, by moving the two-dimensional moving plate 8,
By detecting the incident position of the light transmitted through the hole 81 to the optical position detector A, the hole 8 of the two-dimensional moving plate 8 is detected.
You can know the position of 1.

[0022]

However, the conventional two-dimensional optical position detector has the following problems. That is, in addition to the photocurrent I, the transparent resistance layer 3 receives input offset voltages ΔVa and Δ of the non-inverting amplifiers 61a and 61b.
A current ΔI due to the difference in Vb flows as shown in equation 4 below.

[0023]

[Math 4]

For this reason, the non-inverting amplifiers 61a, 6
The currents Ia and Ib flowing through the load resistance 1b are, for example, (Ia +
.DELTA.I), (Ib - .DELTA.I), and the position output Vx becomes as shown in Equation 5 below, resulting in a position detection error .DELTA.x due to the error current .DELTA.I and the offset voltage.

[0025]

[Math 5]

However, since the resistance value Rt of the transparent resistive layer 3 of the conventional optical position detector A is small, the ratio of the error current ΔI to the photocurrent I cannot be ignored, and the error Δx of the position output Vx becomes large, causing detection There was a problem with poor accuracy.

In order to solve this problem, the transparent resistive layer 3
When the resistance value Rt is increased by decreasing the thickness of the transparent resistive layer 3, the ratio of the error current ΔI to the photocurrent I becomes small;
Since the uniformity of the film thickness is impaired, the position detection error becomes similarly large.

Furthermore, even if the resistance value Rt is increased by forming the transparent resistance layer 3 in the shape of a thin line, the error current ΔI will similarly become small; The region that contributes to the current is only the portion where the a-Si photovoltaic layer 4 and the transparent resistance layer 3 overlap, and if the overlapping area is small, the photocurrent I with respect to the amount of incident light will also be small. Eventually, the ratio of error current ΔI to photocurrent I becomes similarly large,
Furthermore, the ratio of R(Ia +ΔI) to the offset voltage becomes smaller, and the position detection error becomes larger.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a two-dimensional optical position detector that can improve the accuracy of position detection with respect to a light incident position.

[0030]

[Means for Solving the Problems] The two-dimensional optical position detector of the present invention has a transparent resistive layer, a photovoltaic layer, and a first conductive layer laminated, and the transparent resistive layer has two pairs of perpendicular second conductive layers. In an optical position detector provided with a conductive layer, the transparent resistive layer is composed of a large number of sheet resistors and thin wire resistors that connect adjacent sheet resistors.

[0031]

[Function] In the two-dimensional optical position detector of the present invention, the first conductive layer functions as a bias electrode, the second conductive layer functions as a detection electrode, and the incident light incident on the photovoltaic layer is The position is detected by photocurrent flowing into each of the two pairs of second conductive layers through a transparent resistive layer composed of a large number of sheet resistors and thin wire resistors.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. In each figure, the same or corresponding parts are given the same reference numerals. FIG. 1 is a block diagram of a two-dimensional optical position detector according to an embodiment of the present invention, in which (a) is a perspective view, and (b) is an O-
FIG. 2 is a cross-sectional view showing the cross section along the O' line, and FIG. 2 is a diagram showing an example of a pattern of a transparent resistive layer of an optical position detector.

This embodiment has the same basic structure as the conventional example, but the structure of the transparent resistance layer 3 is different. In FIG. 1, an optical position detector A includes two pairs of orthogonal detection electrodes 2a made of Al or the like on a substrate 1 such as a transparent glass plate.
, 2b, 2c, and 2d are formed by vapor deposition or the like, and then indium tin oxide (ITO) or tin oxide (SnO2) is formed on the substrate 1 by sputtering or the like so that the detection electrodes 2a, 2b, 2c, and 2d and their both ends overlap. hundreds~
A patterned transparent resistance layer 3 is formed to a thickness of 1,000 Å, and an a-Si photovoltaic layer 4 of approximately 1,000 Å is deposited on top of this by vapor deposition such as plasma CVD or sputtering.
A layer, I layer, and N layer are laminated in this order to have a width wider than the width of the transparent resistive layer 3, and finally, a bias electrode 5 made of Al or the like is formed by vapor deposition or the like to have a width approximately the same as that of the transparent resistive layer 3.

As shown in FIG. 2, the transparent resistive layer 3 is composed of a large number of sheet resistors 32 and thin wire resistors 31 connecting adjacent sheet resistors 32. In the case of this embodiment, the sheet resistors 32 each have a square shape with substantially the same size on each side, are arranged in a matrix, and the intermediate portions of each side of adjacent sheet resistors 32 are connected by thin wire resistors 31. ing. Moreover, within the sheet resistor 32, the detection electrodes 2a, 2b, 2c, 2d
The planar resistors 32 adjacent to each other are connected via thin wire resistors 31 to the adjacent detection electrodes 2a, 2b, 2c, and 2d in a superimposed manner. The operation of the optical position detector A and the like having such a configuration is the same as that of the conventional example, so a description thereof will be omitted.

It is advantageous in terms of resolution to set the width between the planar resistors 32 (portions where no resistors are formed) to be smaller than the diameter of the incident light. However, since the diameter of the incident light is usually set to about the area of the sheet resistor 32, it is not necessary to make it extremely small.

The sheet resistance 32 and the thin wire resistance 31 of the transparent resistance layer 3 may be determined as follows. That is, the area of the luminous flux incident on the a-Si photovoltaic layer 4 is S, the average illuminance is E, the photocurrent conversion efficiency is k, and the overlapping area ratio of the transparent resistance layer 3 to the a-Si photovoltaic layer 4 is m. Then, the average photocurrent I is given by Equation 6 below.

[0037]

[Math 6]

[0038] If we pay attention to only the X coordinate here, we can see FIG.
Non-inverting amplifiers 61a, 6 in the position detection circuit 6 shown in FIG.
For the offset voltages ΔVa and ΔVb of 1b, the average photocurrent I is determined by the above formula 5 to a predetermined error tolerance rate α (<<1
) is used to determine the superimposed area ratio m so as to satisfy the following formula 7, that is, the following formula 8, and furthermore, from the above formula 4, the total resistance value Rt of the transparent resistive layer 3 is determined as the error tolerance β (<<1
), determine the size of the sheet resistor 32 and the thin wire resistor 31 so that the following equation 9 is satisfied, that is, I >> ΔI for the error current ΔI in the above equation 5, and the total Adjust the resistance value Rt.

[0039]

[Math 7]

[0040]

[Math. 8]

[0041]

[Math. 9]

That is, according to this embodiment, the transparent resistive layer 3
It is possible to make the total resistance value Rt about 10 to 100 times higher than that of a conventional single-sided transparent resistance layer. Since the area ratio m can be increased, the ratio of photocurrent I to error current ΔI can be made larger than that of conventional optical position detectors without significantly reducing photocurrent I to the amount of incident light, greatly improving position detection accuracy. can.

FIGS. 3 to 5 show other examples of patterns of the transparent resistance layer 3. In FIG. 3, the transparent resistance layer 3 is
A large number of square-shaped sheet resistors 32 each having approximately the same size and arranged in a matrix, and a thin wire resistor 3 that connects adjacent sheet resistors 32, including those on the diagonal, between their corners.
It consists of 1.

In FIG. 4, only the transparent resistive layer 3 of the pattern shown in FIG. 3 is rotated by 45°, and the transparent resistive layer 3
The sheet resistance 32 around the outer periphery of the detection electrodes 2a, 2b, 2c,
2d, or to adjacent detection electrodes 2a, 2b, 2c, and 2d at the corners via thin wire resistors 31.

In FIG. 5, the transparent resistive layer 3 includes a large number of hexagonal resistors 32 arranged in a honeycomb shape, each surface having approximately the same size, and a corner portion between the adjacent resistors 32. It is composed of a thin wire resistor 31 connected between the two. In this case, the sheet resistance 32 on the outer periphery is also the detection electrode 2a, 2b, 2c.
, 2d, either directly or via a thin wire resistor 31.

FIG. 6 is a block diagram of an optical position detector according to another embodiment of the present invention, in which (a) is a perspective view of the optical position detector, and (b) is a perspective view of the optical position detector.
is a cross-sectional view showing the cross section along the line O-O'. In this embodiment, the substrate 1 is made of a resin with a smooth surface such as epoxy or polyimide, a ceramic such as alumina, or an opaque metal such as stainless steel.

On this substrate 1, bias electrodes 5,
an a-Si photovoltaic layer 4, a transparent resistance layer 3 composed of a large number of sheet resistors 32 and thin wire resistors 31 connecting adjacent sheet resistors 32, two orthogonal pairs of detection electrodes 2a, 2b,
2c and 2d are stacked. In this case, the a-Si photovoltaic layer 4 is formed into a PIN structure by forming an N layer, an I layer, and a P layer in this order on the bias electrode 5.

In this embodiment as well, the same effects as in the embodiment of FIG. 1 can be obtained, and if the substrate 1 is made of metal, it can also serve as the bias electrode 5, and the number of parts can be reduced. Further, when the substrate 1 is made of resin or plastic, there is an advantage that the position detection circuit 6 for the optical position detector A can be mounted on the same substrate.

[0049]

As described above, according to the two-dimensional optical position detector of the present invention, a transparent resistive layer formed on one side of a photovoltaic layer is connected to a large number of planar resistors and an adjacent planar resistor. Since it is constructed with a thin wire resistor connected between the By treating this as a minimum, it is possible to extend the lifespan.

Furthermore, since the influence of temperature drift from the non-inverting amplifier can be reduced, there are no restrictions on model selection, so the configuration of the detector can be simplified, and in addition, costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a two-dimensional optical position detector according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a pattern of a transparent resistive layer according to the above embodiment.

FIG. 3 is a diagram showing an example of a pattern of a transparent resistive layer according to another embodiment of the present invention.

FIG. 4 is a diagram showing an example of a pattern of a transparent resistive layer according to another embodiment of the present invention.

FIG. 5 is a diagram showing an example of a pattern of a transparent resistive layer according to another embodiment of the present invention.

FIG. 6 is a configuration diagram of a two-dimensional optical position detector according to another embodiment of the present invention.

FIG. 7 is a configuration diagram of a conventional two-dimensional optical position detector.

FIG. 8 is a configuration diagram of an optical position sensor.

[Explanation of symbols]

1 Substrate 2 Detection electrode (second conductive layer) 3 Transparent resistance layer 31 Thin wire resistance 32 Planar resistance 4 a-Si photovoltaic layer (photovoltaic layer) 5 Bias electrode (first conductive layer)

Claims (1)

[Claims] 1. A transparent resistance layer, a photovoltaic layer, and a first conductive layer are sequentially laminated, and the transparent resistance layer is provided with two pairs of second conductive layers orthogonal to each other, and the transparent resistance layer is In a two-dimensional optical position detector that detects the position of incident light that has entered the photovoltaic layer through the photovoltaic layer using a photocurrent divided into four parts and flowing into the two pairs of orthogonal second conductive layers, the transparent resistive layer is A two-dimensional optical position detector comprising a large number of planar resistors and a thin wire resistor connecting adjacent planar resistors.