JPH0426413B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a pressure sensitive sensor that is small in size and has high detection accuracy.

(Background Art) A cross-sectional view of the configuration of a conventional pressure-sensitive sensor is shown in FIG. 10 is a pressure-receiving part made of a thin film such as a polyester film and made into a reflective surface by vapor-depositing aluminum or the like on one side (the surface that does not come into direct contact with the external pressure F); 20;
is a flexible part made of silicone, rubber, etc. with good light transmittance. 30a, 30b, and 30c are light receiving elements, 40 is a transparent glass substrate, and 50 is a glass substrate 40 with a non-light-transmitting metal deposited on one side (hereinafter referred to as a light-shielding layer); Non-evaporated portions (hereinafter referred to as light transmission windows) 60a, 6
It has 0b and 60c. 70 is an air layer, 80a,
80b and 80c are light emitting elements; 90 is a light emitting element 80
This is a substrate made of ceramic or the like on which elements a, 80b, and 80c are mounted.

FIG. 2 shows the shape of the light receiving elements 30a, 30b, 30c viewed from the top (external pressure F side). In addition, the light transmitting windows 60a, 60b, 60c and the light emitting element 8
0a, 80b, and 80c are approximately circular. In addition, in FIG. 1, the electrode parts of the light receiving elements 30a, 30b, 30c and the light emitting elements 80a, 80b, 80c,
The supporting parts of each part are not shown, and although the receiving and emitting elements are originally arranged in a matrix, three elements are shown each, and the electric circuits such as the driving part and the control part of the receiving and emitting elements are shown. The system is also not shown.

In this operation, when the light emitting element 80a is electrically driven to light up, the light emitted from the light emitting element 80a is transmitted through the light transmission window 60a, and the glass substrate 40,
The light passes through the flexible section 20, is reflected at the pressure receiving section (reflection surface) 10, and passes through the flexible section 20 again to be irradiated onto the light receiving element 30a. Here, the amount of light irradiated to the light receiving element 30a changes depending on the distance between the light receiving element 30a and the pressure receiving part 10, and the output of the light receiving element 30a changes as shown in FIG. 3 according to the distance. Since this distance corresponds to the amount of distortion (amount of compression) of the pressure receiving section 10 due to the applied external force F, the output of the light receiving element can be converted into a pressure value. The light emitting element is 80a, 80
b, 80c sequentially and at the same time the light receiving element 3
By sequentially selecting 0a, 30b, and 30c and converting the output into a pressure value, pressure at multiple points can be detected.

The above is the principle of the pressure sensitive sensor, but the problems with the above configuration are shown below.

(1) Generally, a light emitting diode or the like is used as a light emitting element, but since it does not have much directivity, the amount of light passing through the light transmission window 60a is small and the S/N ratio is poor. In addition, in order to increase the amount of light passing through, use the light transmitting window 6.
The diameter of 0a may be increased, but if it is increased, light will directly enter from the back surface of the light-receiving element 30a, as shown in FIG. 4a.

(2) The light reflected by the pressure receiving part (reflection surface) 10 not only enters the surface of the receiving element 30a but also enters the glass substrate 40 again as shown in FIG. The light is reflected and enters the back surface of the light receiving element 30a.

Item (1) above creates constraints on the configuration; in order to increase the diameter of the light transmission window, it is necessary to increase the inner and outer diameters of the light-receiving element, and therefore it is necessary to arrange multiple elements at high density. It becomes difficult to
As shown by the middle broken line, even if the relative positions of the light-receiving element and the light-emitting element deviate, the light enters directly from the back side of the light-receiving element, which requires high precision in the relative position of the light-receiving and emitting elements, which causes manufacturing problems. It was hot. In addition, item (2) above is a major cause of deterioration of the sensor characteristics shown in Figure 3, and the light receiving element and pressure receiving part (reflecting surface)
This has had an adverse effect, such as not allowing a large change in the output of the light-receiving element with respect to a change in distance between the two.

In addition, since the light receiving element is formed on one side of the glass substrate and the light shielding layer is formed on the other side, the manufacturing process is increased and it is necessary to align them (aligning the centers of the light receiving element and the light transmitting window).

(Problems to be solved by the invention) An object of the present invention is to eliminate the above-mentioned drawbacks, and to provide a pressure-sensitive sensor that is easy to configure and has high detection accuracy. a light-transmissive flexible member layer having a light-reflecting surface on one side, a substrate layer provided in contact with the other surface of the layer, a light-receiving element mounted on the surface of the substrate layer in contact with the flexible member layer, and the other side of the substrate. a substantially circular light-receiving element mounted on the surface of the substrate and having a light-transmitting window formed in the center; and a substantially circular light-receiving element mounted on the surface of another substrate disposed opposite to the other surface different from the light-receiving element mounting surface of the substrate layer. and a substantially circular light emitting element located approximately in the center of the light transmitting window of the light transmitting element of the light receiving element projected onto the surface, and the light emitted from the element is reflected by the light reflecting surface according to the deformation of the flexible member layer. In the pressure-sensitive sensor that provides a light-receiving pressure corresponding to external pressure by receiving light with the light-receiving element, the pressure-sensitive sensor includes an optical fiber plate in which the substrate layer has fibers in the longitudinal direction in the thickness direction.

(Structure and operation of the invention) FIG. 5 is a cross-sectional view showing the structure of an embodiment of the invention, and only the periphery of one set of light receiving and emitting elements is shown. The present invention differs from the conventional example in that a fiber plate is used as the substrate forming the light receiving element 30a. Reference numeral 100 is a fiber plate whose thickness direction is in the direction of the fiber bundle, and a light receiving element 30a is formed on the upper surface of the fiber plate 100 (on the pressure receiving part 10 side) by sputtering or the like. The light emitted from the light emitting element 80a enters the fiber plate 100, propagates within each fiber, becomes light that spreads from the other end, passes through the flexible part 20, is reflected by the pressure receiving part (reflecting surface), and is reflected by the light receiving element 30a. irradiated.

The spread angle of light exiting from the fiber to the upper surface (towards the pressure receiving section 10) is determined by the numerical aperture of the fiber, and by selecting this numerical aperture, various spread angles can be set.

Here, in the fiber plate 100,
The incident angle of the light emitted from the light emitting element 80a becomes large with respect to the fiber fiber corresponding to the position of the light receiving element 30a, and the light is not propagated within the fiber fiber, so that light is incident on the light receiving element 30 from the bottom surface. almost disappears.

Further, even if the relative positions of the light-receiving element 30a and the light-emitting element 80a are shifted as shown by the broken line in FIG. 5, there is almost no light incident from the bottom surface.

Setting elements for eliminating light incidence from the bottom include the fiber plate 100 and the light emitting element 80.
Although there are the distance from the light receiving element 30a, the inner diameter of the light receiving element 30a, the dimensions of the light emitting element 80a, etc., the degree of freedom in setting these is greater than in the conventional example.

On the other hand, as shown in FIG. 4b in the conventional example, there is a problem in which the reflected light from the pressure receiving part (reflecting surface) passes through the glass substrate again, is reflected by the light shielding layer, and enters the lower surface of the light receiving element. Needless to say, it can be solved.

FIG. 6 is a perspective view showing a schematic configuration of this embodiment, and is an example in which 4×4 light receiving and emitting elements are arranged at intervals of 2 mm. In the embodiment, the pressure receiving part 10 has a thickness of
The flexible part 20 is made of transparent silicone rubber with a thickness of 2 mm, the light receiving element 30 is made of amorphous silicon, and the light emitting element 80 is made of LED. In addition, the light receiving element 30 and the light emitting element 80
are each driven in a matrix by an electric circuit section (not shown).

FIG. 7 is a block diagram showing the electric circuit system.
200 and 210 are a light emitting element group and a light receiving element group arranged in a matrix, 200 and 230 are analog multiplexers, 240 is a control circuit, and 25
0 is an amplifier, 260 is a sample and hold circuit,
270 is an A/D converter, 280 is a signal processing circuit, a light emitting element group 200 and a light receiving element group 210
are analog multiplexers 220 and 230, respectively.
is matrix-driven.

In operation, first, one light emitting element in the light emitting element group 200 and a light receiving element corresponding to the light emitting element in the receiving element group 210 are connected to the analog multiplexers 220 and 230 by the control circuit 24.
Selective driving is performed by switching with a signal from 0. A selected light emitting element in the light emitting element group 200 is connected to an analog multiplexer 220.
When a voltage V is applied to the element and the element emits light, the output of the light receiving element corresponding to the light emitting element in the light receiving element group 210 is amplified by the amplifier 250 via the analog multiplexer 230 and sent to the sample and hold circuit 260. is input. A hold signal synchronized with driving is inputted to the sample/hold circuit 260 by the control device 240, and the signal from the amplifier 250 is held and sent to the A/D converter 270. The A/D converter 270 converts the hold signal into a digital signal (conversion timing is set by the control circuit 240). 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 280 and output as a pressure signal.

Here, the conversion to a pressure value is performed, for example, by creating a table representing the relationship (applying force→compressibility of flexible portion→displacement amount of reflective surface→light receiving element output).

The above is the operation for one set of light receiving and emitting elements,
For all the elements, each light receiving element is sequentially driven by the control circuit 240 in the same manner, so that the entire pressure receiving surface is scanned (Advantageous Effects of the Invention) As explained above, the present invention has the following features: By forming a light-receiving element on one side of a fiber plate having fiber bundles in the thickness direction, light incident from the back surface of the light-receiving element can be removed without forming a light-shielding layer, and detection accuracy of the pressure-sensitive sensor can be improved. , there are advantages in that the tolerance for structural positional accuracy can be increased, therefore manufacturing time can be shortened, and it is possible to arrange at high density.
For example, it can be mounted on a robot hand or the like and used as a tactile sensor.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the configuration of a conventional pressure-sensitive sensor, Fig. 2 is a plan view showing the shape of the light receiving element, and Fig. 3 is a cross-sectional view showing the configuration of a conventional pressure-sensitive sensor.
The figures show the output characteristics of the light receiving element with respect to changes in the distance between the light receiving element and the reflecting surface, Figures 4a and b show the light irradiation path to the back surface of the light receiving element in the conventional example, and Figure 5
6 is a perspective view showing the structure of the embodiment of the present invention, and FIG. 7 is a block diagram showing the electric circuit system in the embodiment of the present invention. 10...Pressure receiving part (reflection surface), 20...Flexible part,
30, 30a, 30b, 30c...light receiving element, 4
0... Glass substrate, 50... Light shielding layer, 60a, 6
0b, 60c...Light transmission window, 70...Air layer, 8
0, 80a, 80b, 80c... light emitting element, 90
...Light emitting element mounting board, 100... Fiber plate, 200... Light emitting element group, 210... Light receiving element group, 220, 230... Analog multiplexer, 240... Control device, 250... Amplifier, 260... ...Sample and hold circuit, 270
...A/D converter, 280...signal processing circuit.

Claims (1)

[Claims] 1. A light-transmitting flexible member layer that is deformable by external pressure and has a light-reflecting surface on one surface, a substrate layer formed in contact with the other surface of the layer, and a surface of the substrate layer in contact with the flexible member layer. A substantially circular light-receiving element is mounted and has a light-transmitting window formed in the center thereof, and a light-receiving element is mounted on the surface of another substrate disposed opposite to the other surface of the substrate layer that is different from the light-receiving element mounting surface, and the light is projected onto the surface. and a substantially circular light emitting element located approximately in the center of the light transmission window of the light receiving element, and the light emitted from the element is reflected by a light reflecting surface according to the deformation of the flexible member layer, and the light is received by the light receiving element. 1. A pressure sensitive sensor that provides a light receiving output corresponding to an external pressure, wherein the substrate layer is constituted by an optical fiber plate having a longitudinal direction of the fibers in the thickness direction.