JPS61731A - Light-receiving signal lead-out circuit of 2-dimensional pressure sensitive sensor - Google Patents

Abstract

PURPOSE:To lead out a pressure signal with low noise level corresponding to pressure distribution, by differentiating an output signal of a light-receiving element in a position corresponding to an ignited light emitting element and an output signal of a light- receiving element in a position beyond the reach of a beam of light of the ignited light emitting element. CONSTITUTION:A beam of light emitted from a plurality of light emitting elements arranged on a plane is, after passing, reflected by a pressure load part of a soft unit and pressure distribution of the pressure loaded surface by the change of outputs of the light-receiving elements 5 of the light-receiving element group 13. A light-receiving element position selecting signal 20b is applied to an address setting circuit 36 as an output and an address signal is applied to an analog-multiplexer 34 for correcting signals for extracting noise element generated in connection with traverse line selecting decoder 32, longitudinal line selecting analog-multiplexer 33 and light-receiving element. An differential arithmetic circuit 35, after taking a difference of the light-receiving element output issued from the multiplexers 33, 34 allows a correcting light-receiving output deprived of the noise element to be issued as an output. Thus, a pressure signal with low noise level corresponding to the pressure distribution covering the whole pressure loaded area can be led out.

Description

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

(Prior Art) Conventionally, as such a technology in the field of women, there was a technology filed by the applicant of the present application as Japanese Patent Application No. 63158 of 1983.

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 circuit.
The light emitting element group 11, which includes a large number of light emitting elements 1 arranged in a matrix, is sequentially pulse-lit by a light emitting element driving circuit 12. Out of the light receiving element group 13 in which a large number of light receiving elements 5 provided corresponding to each light emitting element are arranged in a matrix, the light receiving element output corresponding to the lighted light emitting element position is outputted to the light receiving signal extraction circuit 1.
4 is selectively extracted. This light-receiving element output is amplified by an amplifier 15, held by a sample-and-hold circuit 16, and inputted to a power converter 17. The A
Since the signal converted into a digital signal by the /D converter is a signal corresponding to the distance between the light receiving element and the reflecting surface, it is converted into a pressure value by the signal processing circuit 18 and output as a pressure signal.

These series of operations are performed by each control signal 20 of the control circuit 19 and h.
The timing is controlled by a to 2θe.

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, and if a constant voltage is applied from the outside, the amount of irradiated light, and even It is possible to know the pressure applied to the two-dimensional pressure sensor. The light-receiving signal extracting circuit shown in FIG. 4 is well known for reducing the influence of rotation in the matrix circuit when driving a large number of amorphous silicon light-receiving elements in a matrix and extracting the light-receiving signals.

The light receiving element group 13 can be expressed as a resistance matrix whose resistance value changes depending on the irradiated light. The light reception signal extraction circuit 14 performs address setting to specify the addresses of the row selection decoder 21 and the column selection analog multiplexer 22 in accordance with the control signal 20b of the row selection decoder 2, the column selection analog multiplexer 22, and the control circuit 19. circuit 24
It consists of etc.

(Problem to be Solved by the Invention) However, in the sensor configuration shown in Figure 2, the light-emitting element group and the light-receiving element group are brought close together, and the pulsed lighting current of the light-emitting element is induced onto the signal line leading to the light-receiving element. If noise is generated, induced noise from the outside world may be generated in the cable connecting the light receiving element group and the light receiving signal extraction circuit, and furthermore, a slight disturbance light transmitted through the light reflection film may be generated in the light receiving element. There has been a drawback that φ of the detection signal tends to decrease, such as signal noise.The present invention eliminates the noise components generated in these light receiving element output signal lines, and improves the S/N of the detection signal.
An object of the present invention is to provide a light reception signal extraction circuit for a two-dimensional pressure-sensitive sensor that is inexpensive and highly accurate.

(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 changes to the light receiving element according to the deformation of the pressure receiving part. A first multiplexer that selects and outputs an output signal of a light receiving element located at a position corresponding to a lighted light emitting element is used as a light receiving signal extraction circuit of the two-dimensional pressure sensitive sensor that is incident on the light emitting element, and a first multiplexer that selects and outputs an output signal of a light receiving element located at a position corresponding to a lighted light emitting element; The second multiplexer selects and outputs the output signal of the light-receiving element located at a different position, and the difference calculation means detects a difference signal between the output signals of the two light-receiving elements.

(Function) According to the present invention, since the light reception signal extraction circuit for the two-dimensional pressure sensitive sensor is configured as described above, the output signal of the light reception element located at the position corresponding to the lighted light emitting element is sent to the first multiplexer. The output signal of the light-receiving element located far enough away that the light from the lit light-emitting element cannot reach is outputted through the second multiplexer, and each of these output signals is calculated by a difference calculator. It works to remove noise components generated in the light receiving element output signal line by calculation, thus solving the above problem.

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

The received light signal extraction circuit according to the present invention is an improvement of the received light signal extraction circuit 14 shown in FIG. 3, and will be explained using FIG. 3 for convenience of explanation.

In FIG. 1, numeral 31 indicates a light receiving signal extraction circuit, which includes a row selection decoder 32, a column selection analog multiplexer 33, a correction signal analog multiplexer 34 for extracting noise components generated in the signal line connected to the light receiving element, A difference calculation circuit 35 for canceling noise components from the light receiving element output signal including noise components, the row selection decoder 32, and analog multiplexers 33, 3.
It is composed of four address setting circuits 36.

Next, the operation of this circuit will be explained.

Now, when the light receiving element position selection signal 20b is sent from the control circuit 19 (FIG. 3), the decoder 32 and the address setting circuit 36 of the analog multiplexers 33 and 34 output the row selection address signal 37 and the column selection address signal 38. .39 are provided to decoder 32 and analog multiplexer 3334, respectively.

For example, when the light-receiving elements in the first horizontal row and the first vertical row of the light-receiving element group are selected, the switch connected to the first horizontal row of the decoder 32 is turned OFF and all the others are turned ON, and the analog multiplexer 33 is turned on. The switch connected to the first vertical column is turned on and all the others are turned off.

Further, for example, the third vertical
The switch connected to the row is turned on, and the remaining nine are all turned off. Here, the analog multiplexer 34 extracts the dark current of the light-receiving element, and it is only necessary to select a light-receiving element at a position where the light of the lit light-emitting element does not reach.
The address input to multiplexer 34 is an analog
It may be the address input to the multiplexer 33 plus a certain constant.

Thus, the output of analog multiplexer 33 is
The output of the light receiving element corresponding to the lit light emitting element is obtained,
The dark current output of the light receiving element is obtained as the output of the analog multiplexer 34, but if noise such as induced noise occurs, the signal line of the light receiving element corresponding to the lighted light emitting element and the signals of other light receiving elements are obtained. Since noise is uniformly superimposed on the line, by calculating the difference between the two in the difference calculation circuit 35, a corrected light receiving element output from which noise components have been removed can be obtained.

The corrected light-receiving element output is amplified by an amplifier 15 shown in FIG. 3 and input to a sample-and-hold circuit 16. The light receiving element signal held by the timing signal from the control circuit 19 is converted into a digital signal by the digital converter 17. Since this digital signal is a signal corresponding to the distance between the light receiving element and the reflecting surface, it is converted into a pressure value by the signal processing circuit 18 and output as a pressure signal.

The above is the operation for one set of light receiving and emitting elements, and all of the light receiving and emitting elements are driven in sequence in the same way.By this, a pressure signal with less noise is obtained in accordance with the pressure distribution over the entire surface of the pressure receiving surface.

(Effects of the Invention) As explained above, the present invention uses a two-circuit analog multiplexer to connect the output signal of the light receiving element at the position corresponding to the lighted light emitting element to the extent that the light from the lighted light emitting element does not reach. Take out the output signal of the light receiving element located far away,
By taking these differential signals in a differential calculation circuit, it is possible to remove noise components generated in the output signal line of the light receiving element, and to improve the light reception of a high-precision two-dimensional pressure-sensitive sensor with improved S/'N. A signal extraction circuit can be realized.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a sectional view showing the configuration of a two-dimensional pressure-sensitive sensor, FIG. 3 is a diagram showing a two-dimensional pressure-sensitive sensor and its processing device, and FIG. Figure 4' is a diagram showing a conventional light reception signal extraction circuit. 5... Light receiving element, 13... Light receiving element group, 31...
Receiving signal appearance, output circuit / ``Parameter side''] selection data
Ta 33°°. Column selection analog multiplexer, 34... Analog multiplexer for correction signal, 35... Difference calculation circuit,
36...Address setting circuit. Patent Applicant: Oki Electric Gengyo Co., Ltd. Figure 4, 20b: Written amendment to Seiseiyu No. procedure (Seiseiyu, September 13, 1999)

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 extraction circuit 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 extraction circuit comprising: a light-reflecting film; a first multiplexer that selects and outputs an output signal from a light-receiving element located at a position corresponding to the element; and a second multiplexer that selects and outputs an output signal from a light-receiving element located at a position where light from the light-emitting element that is lit does not reach. multiplexer and
A light-receiving signal extraction circuit for a two-dimensional pressure-sensitive sensor, comprising: a difference calculation means for detecting a difference signal between the output signals of the two light-receiving elements.