JPS612032A - Photodetecting signal converter of two-dimensional pressure sensitive sensor - Google Patents

Abstract

PURPOSE:To suppress the variance of the sensitivity of a photodetector and to obtain a highly accurate device reduced at its pressure measuring error by forming circuits for respectively detecting a dark current of a photodetector which is obtained before the lighting of a light emitting element and an optical current of the photodetector which is obtained during the lighting of the light emitting element. CONSTITUTION:Many light emitting elements (light emitting diodes e.g.) are arranged like a matrix to constitute a pressure sensitive sensor of a light emitting element group 21 to be successively turned on with pulses by a light emitting element driving circuit 22 and a photodetector group 23 consisting of many photodetectors (amorphous silicon photodetectors e.g.) arranged correspondingly to respective light emitting elements. A dark current signal obtained by detecting a dark current of a photodetecting element corresponding to a light emitting element immediately before the lighting of the light emitting element by a photodetecting signal extracting circuit 24 and digitizing the detected signal through an amplifier 26, a sample holding circuit 28 and an A/D converter 29 and an optical current signal obtained by detecting an optical current of the corresponding photodetector during the lighting of the light emitting element by the circuit 24 and digitizing the detected signal through an amplifier 27, a sample holding circuit 30 and an A/D converter 31 are simultaneously inputted to a signal processing circuit 32, the valiance of sensitivity in each photodetector is corrected and the corrected signal is converted into a voltage signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a light reception signal conversion device for a planar two-dimensional pressure-sensitive sensor that can accurately detect the distribution of applied pressure.

(Prior Art) Conventionally, as a technology in this field, there has been a technology filed as Japanese Patent Application No. 59-63158 by the applicant of the present application.

The configuration will be explained below.

Figure 2 shows an example of the two-dimensional pressure-sensitive sensor introduced in the above-mentioned prior art, in which light from a plurality of light-emitting elements 1 arranged in a plane is transmitted through each light-receiving element. The light transmitted through the window 2 and the transparent flexible portion 3 is received by the light receiving element 5 corresponding to each light emitting element, and the reflected light from the light reflecting film 4 is received by the light receiving element 5 corresponding to each light emitting element.
An electric signal corresponding to a change in pressure corresponding to a change in the amount of light received is obtained from a change in the distance between the light emitting element and the light receiving element based on a change in the pressure F applied to the pressure receiving surface of the flexible part. FIG. 3 shows this two-dimensional pressure-sensitive sensor and its processing device. The two-dimensional pressure-sensitive sensor section 10 is composed of a light-emitting element group 11, a light-receiving element group 13, etc., and a large number of light-emitting elements 1 are arranged in a matrix. The provided light emitting element group 1 is sequentially pulse-lit by the light emitting element drive circuit 12. Further, the light receiving element output corresponding to the lighted light emitting element position in the light receiving element group 13 in which a large number of light receiving elements 5 provided corresponding to the light emitting elements 1 are arranged in a matrix is sent to the light receiving signal extraction circuit 14. It is selectively extracted. This light receiving element output is amplified by an amplifier 15, and a sample hold circuit 16
The signal is held at the A/l) converter 17.

Since the signal digitized by the four converters is a signal corresponding to the distance between the light receiving element and the reflecting surface, the signal processing circuit 18
is converted into a pressure value and output as a pressure signal.

These series of operations are timing controlled by the control circuit 19.

Here, it is convenient for the light-receiving element group 13 to form semiconductor light-receiving elements, such as conductive type amorphous silicon light-receiving elements, in a matrix on one substrate.

This amorphous silicon photodetector has the property that its resistance decreases as the amount of irradiated light increases.If a constant voltage is applied externally, the amount of irradiated light will change depending on the magnitude of the current flowing through the amorphous silicon photodetector. Furthermore, it is possible to know the pressure applied to the two-dimensional pressure-sensitive sensor.

(Problems to be Solved by the Invention) However, the photosensitivity characteristics of semiconductor light-receiving elements such as amorphous silicon are not uniform, and there is a drawback that variations in sensitivity among the light-receiving elements can result in variations in measured pressure.

The present invention suppresses variations in sensitivity of these light receiving elements,
An object of the present invention is to provide a highly accurate light reception signal conversion device for a two-dimensional pressure-sensitive sensor with little pressure measurement error.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a light source substrate having an array of a plurality of light sources, and a light source board that allows the light of the light sources to pass through, and a light source board that has a plurality of light sources arranged around the light passing area. A sensor substrate having arrayed light receiving elements, a pressure receiving part made of a flexible part, and a light reflecting film are laminated, and light from the light source is reflected by the light reflecting film and enters the light receiving element according to deformation of the pressure receiving part. As a light reception signal conversion device of a two-dimensional pressure sensitive sensor, there is provided a means for detecting a dark current output signal of a predetermined light receiving element corresponding to a predetermined light emitting element before the light emitting element is turned on, and a means for detecting a dark current output signal of a predetermined light receiving element corresponding to the light emitting element before the light emitting element is turned on; The apparatus includes means for detecting a photocurrent output signal of the predetermined light receiving element, and a signal processing circuit for processing the Okayama force signal and detecting the pressing force.

(Function) According to the present invention, in configuring the light reception signal conversion device of the two-dimensional pressure sensitive sensor as described above, the dark current of the corresponding light reception element is detected immediately before the light emitting element is turned on, and this is detected by the amplifier. , a sandal hold circuit, detects the digitized dark current signal through a converter, and the photocurrent of the corresponding light receiving element while the light emitting element is lit, and transmits it to an amplifier, a sandal hold circuit, and an A/D converter. The digitalized photocurrent signal is input to the signal processing circuit at the same time via the signal processing circuit, and the signal processing circuit corrects the sensitivity variation of each light receiving element and converts it into a pressure signal. Therefore, the above problem can be solved. be.

(Example) FIG. 1 shows one embodiment of the present invention.

In FIG. 1, 20 is a two-dimensional pressure-sensitive sensor section consisting of a light-emitting element group 21, a light-receiving element group 23, etc., and 2 is a light-emitting element in which a large number of light-emitting elements (e.g., light-emitting diodes) are arranged in a matrix. The light emitting element driving circuit 22 sequentially pulses the light emitting elements in groups.

Reference numeral 23 denotes a light receiving element group consisting of a large number of light receiving elements (for example, amorphous silicon light receiving elements) arranged corresponding to each light emitting element of the light emitting element group, and the light receiving element output is detected by the light receiving signal extraction circuit 24. Moreover, it can be selectively taken out. 25 is an analog switch that connects the output of the light receiving element to the dark current amplifier 26 and the photocurrent amplifier 27 at an appropriate timing.
It is distributed to The amplified dark current is held in a sample and hold circuit 28 and then digitized in a φ converter 29. Similarly, the amplified photocurrent is held in a sample and hold circuit 30 and then digitized in a φ converter 31. The digitized dark current signal and photocurrent signal are input to the signal processing circuit 32. These series of operations are timing controlled by the control circuit 33.

Note that from the light reception signal extraction circuit 24, the analog switch 2
5, amplifiers 26, 27, sample and hold circuit 2B,
30, A/D converter 29, 31, signal processing circuit 32'-
J, is a light receiving signal converter.

When a large number of light-receiving elements such as amorphous silicon are irradiated with a certain amount of light, the photocurrent obtained from each light-receiving element is unlikely to be uniform.

However, this photocurrent has a correlation with the light receiving element output (dark current) when no light is irradiated.

FIG. 4 shows an example of measurement data showing the relationship between dark current and photocurrent of an amorphous silicon light receiving element. This fourth
In the figure, the amount of light received by the light receiving element is 1mwcrn2*0.
It shows the relationship between the photocurrent and the dark current when it is 1 mwCrn2. According to FIG. 4, if the dark current of the light receiving element is known, the amount of light irradiation at that time can be determined by detecting the photocurrent.

5(a) and 5(b) are time charts showing the operating time of one set of light emitting/light receiving elements, and FIGS. 5(c) and 5(d) are time charts showing the operating time of the analog switch 25. Figure 5 (
a) shows the lighting time of one light emitting element, and FIG.
b) shows the driving time of the corresponding light receiving element. Here, the lighting start time of the light emitting element is delayed from the driving start time of the corresponding light receiving element, and the light receiving element outputs a dark current at timing (A) and a photocurrent at timing 0).

The analog switch 25 is connected to the contact A side (FIG. 1) at the ON timing shown in FIG. 5(C), and to the contact B side (FIG. 1) at the ON timing shown in FIG. 5(d). . In this way, the dark current output of the light receiving element is transmitted to the dark current amplifier 26, and the photocurrent output is transmitted to the photocurrent amplifier 27. The amplified dark current is held in the sample and hold circuit 28 at an appropriate point during the ON timing shown in FIG. 5(c), and the amplified photocurrent is held at an appropriate point during the ON timing shown in FIG. 5(d). The sample and hold circuit 30 holds the sample at an appropriate point in time. The held dark current signal and photocurrent signal are simultaneously converted into dinotal signals by the φ converters 29 and 31, and transmitted to the signal processing circuit 32. If the signal processing circuit 32 is prepared with a table for calculating the light irradiation amount from the dark current signal and the photocurrent signal, and a table for converting the light irradiation amount → deformation amount of the sensor pressure receiving surface → pressurizing force, the pressure value can be output. can do.

The above is the operation for one set of light receiving and emitting elements, and similarly, by sequentially driving all the light receiving and emitting elements, a pressure signal corresponding to the pressure distribution over the entire surface of the pressure receiving surface is obtained.

(Effects of the Invention) As explained above, the present invention includes a circuit that detects the dark current of the light receiving element before the light emitting element is lit, and a circuit that detects the photocurrent of the light receiving element while the light emitting element is lit. The light irradiation amount is determined from both signals by correcting variations in the sensitivity of the light receiving element, enabling highly accurate pressure detection with small measurement errors, and a two-dimensional sensing method that uses light to detect the amount of deformation of the pressure receiving surface. It can be used in a light reception signal conversion device for a pressure sensor.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a sectional view showing the configuration of a two-dimensional pressure-sensitive sensor, and Fig. 3 is a conventional two-dimensional pressure-sensitive sensor and its processing device. 4 is a diagram showing the relationship between the dark current and photocurrent of the light receiving element, and FIG. 5 is a time chart explaining the operation timing. 2θ... Two-dimensional pressure sensitive sensor, 21... Light emitting element group,
22... Light emitting element drive circuit, 23... Light receiving element group,
24... Light reception signal extraction circuit, 25... Analog switch, 26... Dark current amplifier, 27... Photocurrent amplifier, 28... Sample hold circuit, 29... Female converter, 30... ... Sandal hold circuit, 31...A
/]) converter, 32... signal processing circuit, 33... control circuit. Patent Applicant Oki Electric Industry Co., Ltd. Agent Toshiaki Suzuki 3 Figure 3 Figure 5 Temporary Figure 4 Figure 4 8 unit 1 Tan [xlσ8A] Procedural amendment (voluntary) Showa 0° February 13

Claims (1)

[Scope of Claims] A light source board having an array of a plurality of light sources, a sensor board that allows light from the light sources to pass through and has light receiving elements arranged around the light passing area, and a pressure receiving part made of a flexible part. ,
A light-receiving signal conversion device for a two-dimensional pressure-sensitive sensor, in which light from the light source is reflected by the light-reflecting film and enters the light-receiving element according to deformation of the pressure-receiving part, the light-receiving signal converting device comprising: a light-reflecting film; means for detecting a dark current output signal of a predetermined light-receiving element corresponding to the light-emitting element before lighting the element; and means for detecting a photocurrent output signal of the predetermined light-receiving element while the predetermined light-emitting element is turned on. and a signal processing circuit that processes both of the output signals and detects the applied force.