JPS60209129A - Pressure sensor - Google Patents

Abstract

PURPOSE:To prevent light from being incident on the reverse surface of a photodetecting element and obtain a high-precision device which is easily manufactured by providing a means which converges luminous flux in a path through which light from a light emitting element travels to a pressure reception surface (reflecting surface). CONSTITUTION:The pressure sensor consists of a lens substrate 1 and a substrate 8 by forming the reflecting surface by vapor-depositing aluminum, etc., on a polyester film as the pressure reception surface 1 over one side, and providing a flexible layer 2 of light-transmittable silicone rubber, etc., and then a glass substrate 4. The light emitting element 7 is provided to the substrate 8 and a lens 10, etc., are provided to the substrate 11 so that light travels while converged. The light from the light emitting element 7 is converged by the lens 10 on a focus O and incident on a photodetecting element 3 through the pressure reception surface 10. At this time, even if pressure P is applied to the pressure reception surface 1 and the flexible layer 2 varies in thickness, the light travels from the focus O, so the light is incident on only the surface of the photodetecting element 3 and never strikes the reverse surface. Thus, the luminous flux means is provided, so reflected light incident on the reverse surface of the photodetecting element is prevented and the pressure is detected with high precision.

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 showing the configuration of a conventional pressure-sensitive sensor is shown in FIG. 1(a). 1 is a reflective surface made of a thin film such as a polyester film on which one side (the surface that does not come into direct contact with external pressure P) is vapor-deposited with aluminum, etc.; 2 is an elastic body made of silicone rubber or the like with good light transmittance; 3 is the light receiving element, 4 is the light receiving element 3
5 is a vapor-deposited film (hereinafter referred to as a light-shielding layer) made of a non-light-transmitting metal on the other surface of the glass substrate 4 (the surface on which the light-receiving element 3 is not formed), which allows light to pass through. It has a non-evaporated part (hereinafter referred to as a light transmission window) 6 for the purpose of the light transmission.

7 is a light emitting element, and 8 is a substrate made of ceramic or the like on which the light emitting element 7 is mounted. FIG. 1(b) shows a plan view of the light receiving element 3. The circles indicated by broken lines in the figure represent the positions of the light transmitting window 6 and the light emitting element 7.

Although only one set of light emitting and receiving elements is shown in FIGS. 1(a) and (b), in reality, the light emitting and receiving elements are arranged in multiple elements in a matrix. Electric circuit systems such as circuits and control circuits, supporting parts of various parts, etc. are not shown.

The operation will be explained below.

The light emitted from the light emitting element 7 passes through the light transmitting window 6, passes through the glass substrate 4 and the elastic body 2, is reflected at the reflective surface l, passes through the elastic body 2 again, and is irradiated onto the light receiving element 3. Here, the amount of light irradiated to the light receiving element 3 is
The relationship between the output of the light receiving element 3 and the distance has a characteristic as shown in FIG. On the other hand, the distance between the reflective surface 1 and the light receiving element 3 corresponds to the amount of distortion (amount of compression) of the elastic body 2 due to the applied external pressure P. Therefore, the external pressure applied can be converted from the output of the light receiving element 3. For a plurality of light receiving and emitting elements arranged in a matrix, pressures at multiple points can be detected by sequentially driving them and converting their outputs into pressure values.

The above is the operating principle of the conventional pressure-sensitive sensor, but the problems with the above configuration are listed below.

(1) Generally, a light emitting diode is used as a light emitting element, but the directionality of light is not very good, so a light transmitting window 6 is used.
Since the amount of light passing through the sensor is small, the quality of the detection signal becomes poor.

(2) If the diameter of the light transmitting window 6 is increased, the amount of transmitted light increases, but as shown in FIG.

(3) In addition to being incident on the surface of the light-receiving element 3, the light reflected by the reflective surface 1 also enters the glass substrate 4 as shown in FIG. 3(b).
The light enters the light receiving element 3 again, is reflected by the light shielding layer 5, and enters the back surface of the light receiving element 3.

Items (1) and (2) above create configuration constraints,
In order to increase the amount of transmitted light and improve the intensity, it is necessary to increase the light transmission outer diameter, which makes it difficult to arrange multiple elements at high density. Furthermore, even if the center positions of the light-emitting element, light-transmitting window, and light-receiving element are shifted relative to each other, as shown by the broken lines in Figure 3(a), light will directly enter the back surface of the light-receiving element, so these High precision was required for placement, which caused manufacturing problems. In addition, the above-mentioned item (3) causes deterioration of the sensor characteristics shown in FIG. 2, and has an adverse effect such as a decrease in the output change of the light receiving element with respect to a change in the distance between the reflecting surface and the light receiving element.

(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 small, easy to configure, and has high detection accuracy. A flexible elastic layer having a reflective surface, a plurality of light receiving elements provided on the other surface of the layer, and a light emitting element that illuminates the light reflecting surface from the back side of the light receiving element, The pressure-sensitive sensor obtains an output corresponding to deformation due to external pressure from the light-receiving element, and the pressure-sensitive sensor is provided with a focusing means for focusing the light beam from the light-emitting element toward the light-reflecting surface.

(Structure and operation of the invention) FIG. 4 is a sectional view showing the structure of the first embodiment of the invention, and only shows the vicinity of one set of light receiving and emitting elements.

The difference between this embodiment and the conventional structure shown in FIGS. 1(a) and 1(b) is that a lens array plate 11 having a lens section 10 is provided at a position corresponding to a light receiving element 3 and a light emitting element 7. be. The light beam emitted from the light emitting element 7 passes through the glass substrate 4 so as to be focused by the lens 10 at a point 0, and after converging at the point 0, it becomes a diffused light beam, passes through the elastic body 2, and reaches the reflective surface. 1, and is irradiated onto the light receiving element 3 via the elastic body 2 again. Here, the amount of light passing through the lens portion 1° is determined by the numerical aperture of the lens, and by using a lens with a large numerical aperture, the amount of light passing through can be increased. Furthermore, since the light from the light emitting element 7 that does not pass through the lens section 10 has a large incident angle on the glass substrate 4 as indicated by the broken line in the figure, it is reflected on the back surface of the glass substrate. In order to eliminate light incidence from the back surface of the light-receiving element 3, the aperture of the lens portion 10 may be increased; however,
By increasing the aperture, the amount of light passing through the lens section 10 also increases, and the S/N ratio of the detection signal can be improved. Therefore, the degree of freedom in configuration settings for eliminating light incidence from the back surface of the light-receiving element 3 is greater than in the conventional example, and the tolerance range for positional accuracy is also greater. On the other hand, as shown in FIG. 3(b) in the conventional example, the problem of the reflected light from the reflective surface passing through the glass substrate again, being reflected by the light-shielding layer, and entering from the back surface of the light-receiving element has been solved. Needless to say, it will be done.

In this example, a so-called "fly's eye lens" is used as the lens array plate. Although the convex surface of the lens portion is shown on the light receiving element side in Fig. 4, it is conversely arranged on the light emitting element side. You may do so.

Next, other embodiments of the present invention will be described.

FIGS. 5(a) and 5(b) are cross-sectional views showing the configuration of a second embodiment of the present invention. The difference from the first embodiment is that a lens and a substrate forming the light receiving element 3 are used. This is because the array plate 11 is used. Fig. 5<) shows a lens array plate in which the ``No.Engine's eye lens'' described in the first embodiment is used as having a convex surface on the light emitting element side. Selfoc lens play plates are used as lenses and array plates.

Note that the SELFOC lens array plate has a lens section 10.
may be provided only at a position corresponding to the light receiving element 3, or may be provided over the entire surface.

FIG. 6 is a sectional view showing the configuration of a third embodiment of the present invention, in which a light emitting element 7 is connected to a concave mirror 21 via an electrical insulator 20.
This is an addition to the second embodiment of the present invention in which the light emitted from the light emitting element 7 has a directionality toward the concave mirror 21, and therefore the light from the light emitting element Most of the light can be guided to the lens section 10, making it possible to further increase the amount of light passing through the lens.

FIG. 7 is a perspective view showing the overall configuration of the above embodiment, and is an example in which 4×4 light emitting and receiving elements are arranged at intervals of 2 Wrm. In the embodiment, the reflective part 1 is a thin film several tens of micrometers thick, the elastic body 2 is transparent silicone rubber with a thickness of 2rrrm, the light receiving element 3 is amorphous silicon, and the light emitting element 7
is LED', lens array plate 10 Haselfotz
Consisting of a lens array and a lens array plate (
A light receiving element (amorphous silicon) 3 is formed on the selfoc lens array (selfoc lens array) 10 by a step-by-step method or the like. Further, the light receiving element 3 and the light emitting element 7 are each driven in a matrix by an electric circuit section (not shown).

FIG. 8 is a block diagram showing the electric circuit system.

100 and 110 are a light emitting element group and a light receiving element group arranged in an IJ array, 120 and 130 are analog multiplexers, 140 is a control circuit, 150 is an amplifier, 1
60 is a sample and hold circuit, 170 is a φ converter, 1
80 is a signal processing circuit, and each of the light emitting element group 100 and the light receiving element group 110 is an analog multiplexer 12.
0.130 and is matrix driven.

In operation, first, one light emitting element in the light emitting element group 100 and a light receiving element corresponding to the light emitting element in the light receiving element group 110 are switched by analog multiplexers 120 and 130, respectively, by a signal from the control circuit 140. Selection driven by. A voltage ■ is applied to the selected light emitting element via the analog multiplexer 130, and when the light emitting element emits light, the output of the selected light receiving element is amplified by the amplifier 150 via the analog multiplexer 140. Sample/hold circuit 16
It is input to 0. A hold signal synchronized with the simatrix drive from the control circuit 40 is input to the sample/hold circuit 160, and the signal from the amplifier 150 is held and sent to the φ converter 170. In the ψ converter 170,
The hold signal is converted into a digital signal according to the timing set from the control circuit 140. Since this digital signal is a signal corresponding to the distance between the selectively driven light receiving element and the reflecting surface, it is converted into a pressure value at the position of the light receiving element by the signal processing circuit 180 and output as a pressure signal. .

Here, conversion to a pressure value can be easily performed by preparing a table representing the relationship, for example, (applying force→compressibility of elastic body→reflecting surface displacement→light receiving element output→).

The above is the operation for one set of light receiving/emitting elements, but for all the elements, the control circuit 140 drives and detects each light receiving/emitting element sequentially in the same manner, and therefore the entire pressure receiving surface is scanned. .

(Effects of the Invention) As explained above, the present invention makes it possible to eliminate light incident from the back surface of the light-receiving element without forming a light-shielding layer by providing a means for converging the emitted light flux from the light-emitting element. , the amount of available light can be increased, which can improve the detection accuracy of the pressure-sensitive sensor and increase the tolerance for structural positional accuracy, thus reducing manufacturing time and increasing the It has the advantage of being able to be arranged in a dense array, and can be used as a small tactile sensor that can be mounted on a robot hand or the like.

[Brief explanation of the drawing]

Figures 1 (,) and (b) are diagrams showing the configuration of a conventional pressure-sensitive sensor, Figure 2 is a diagram showing the output characteristics of the light-receiving element with respect to distance changes between the light-receiving element and the reflecting surface, and Figure 3 (a) ) and (b)
4 is a diagram showing the light irradiation path to the back surface of the light-receiving element in the conventional example.
The figure is a cross-sectional view showing the structure of the first embodiment of the present invention, FIGS. 5(a) and (b) are cross-sectional views showing the structure of the second embodiment of the present invention, and FIG. FIG. 7 is a sectional view showing the structure of the third embodiment, FIG. 7 is a perspective view showing the overall structure of the present invention, and FIG. 8 is a block diagram showing the electric circuit system in the embodiment of the present invention. 1... Reflective surface, 2... Elastic body, 3... Light receiving element,
4... Glass substrate, 5... Light shielding layer, 6... Light transmitting window, 7... Light emitting element, 8... Light emitting element mounting substrate,
10... Lens section, 11... Lens array plate, 2
0... Electric insulator, 21... Concave mirror, 100...
Light emitting element group, 110''-light receiving element group, 1.20, 130
... Analog multiplexer, 140 ... Control circuit, 150 ... Amplifier, 160 ... Sample and hold circuit, 170 ... A/D converter, 180 ... Signal processing circuit. Hou 1 zu ρ Kei, 2 zu funeral, 3 zu arithmetic, 4 zu p ゛/ Qin bU! J Hayabusa, Ro map U Qin 7 map

Claims (5)

[Claims] (1) A flexible elastic layer having a light-reflecting surface on one surface, a plurality of light-receiving elements provided on the other surface of the layer, and a light-emitting element that illuminates the light-reflecting surface from the back side of the light-receiving element. The pressure-sensitive sensor obtains an output from the light-receiving element corresponding to the deformation of the elastic body due to external pressure, further comprising a focusing means for focusing the light beam from the light-emitting element toward the light-reflecting surface. pressure-sensitive sensor. (2) Claim 1, wherein the focusing means is a lens array plate having an array of convex lenses.
Pressure-sensitive sensor described in section. (3) The pressure-sensitive sensor according to claim 1, wherein the focusing means is a lens array plate having an array of self-hock lenses. (4) The pressure-sensitive sensor according to claim 1, wherein the focusing means is a concave mirror provided on the back surface of the light emitting element. (5) The sensor according to claim 2 or 3, wherein the light receiving elements are arranged on the surface of the lens array plate that faces the light reflecting surface of the elastic layer. pressure sensor.