JPS61150522A - Photoelectric switch - Google Patents

Abstract

PURPOSE:To detect exactly a distance without being influenced by a reflection factor of a body to be detected, by making a switch contain plural photodetecting means for outputting a signal of a level corresponding to an incident light quantity, when a position of the body to be detected, and an operating means for executing an operation processing related to an output from the photodetecting means. CONSTITUTION:A light which has been transmitted in optical fibers 26a, 26b is made incident to photodetectors 27a, 27b being photodetecting means. The electrodes 27a, 27b output a signal of a level corresponding to an incident light quantity. This output is amplified by amplifying circuits 28a, 28b, respectively, and voltages V1, V2 are inputted to an operating circuit 29, respectively. In the operating circuit 29, an operation for deriving the V1/V2 is executed. An output of the operating circuit 29 is provided to a non-inversion terminal of a comparing circuit 30, and to an inversion terminal of the comparing circuit 30, a reference voltage VC is applied. An output from the comparing circuit 30 is connected to, for instance, a display device, and whether a body to be detected 24 has been detected or not, etc. are displayed.

Description

TECHNICAL FIELD The present invention relates to a photoelectric switch, and more particularly to a photoelectric switch constructed using optical fibers.

BACKGROUND ART FIG. 4 is a system diagram showing the configuration of a photoelectric switch 1 according to the prior art. Light from a light source 2 realized by, for example, a light emitting diode is transmitted to a detected object via an optical fiber 3 for projecting light. 4.

The reflected light from the detected object 4 is guided to the light receiving element 6 via the light receiving optical fiber 5. The output of the light receiving element 6 is applied to one input terminal of the comparator 7, and the reference voltage 1 is input to the other input terminal of the comparator 7.

FIG. 5 is a graph showing the relationship between the distance X between the detected object 4 and the light emitting optical fiber 5 in FIG. 4 and the amount of light received by the light receiving element 6. The operating state of the photoelectric switch 1 will be explained using FIGS. 4 and 5, in which line No. 1 in FIG. 5 shows this relationship. If the detected object 4 is too close to the light receiving optical fiber 5, the reflected light of the light irradiated onto the detected object 4 from the light emitting light 7 fiber 3 may enter the optical fiber 5 from an oblique direction, for example. Therefore, the amount of light received is at a low level. As ff1MX gradually increases, the amount of light incident on the optical fiber 5 increases, but if the distance The light intensity decreases again.

Here, the amount of received light corresponding to the reference voltage V1 applied to the other input side of the comparator 7 and ν is expressed by the imaginary line ! in FIG. 2
Indicated by This amount of received light corresponds to the reference distance defined as X=XO at the distance.

That is, the level of the amount of light received by the light receiving cable 6 is
Beyond the line 12 in the figure, it is determined that the detected object 4 exists at a distance equal to or less than X=XO.

In such prior art, whether or not the object to be detected 4 is detected is determined based on whether or not the amount of light incident on the light receiving probe 6 exceeds a predetermined level.
Distance in Figure 4 corresponding to the level of Line No. 2 in Figure 4 = X
Even if the object 4 to be detected is present at O, if the reflectance of the light irradiated from the projecting light 7 eyeper 3 is low, for example, the light receiving element 6 will receive the light as shown by the line 12 in FIG. This means that only the amount of light that is below the level will be incident. Therefore, there is a problem in that the comparator 7 determines that the detected object 4 is not within the distance X=XO.

Conversely, even if the detected object 4 exists at the distance @X = teeth,
The level of the amount of light will be at a distance closer than the distance X=XO. In this way, ill! There is a problem in that erroneous recognition of distance may occur.

Purpose An object of the present invention is to solve the above-mentioned problems and provide a photoelectric switch that can reliably detect distance without being affected by the reflectance of the object to be detected.

Embodiment FIG. 1 is a system diagram showing the configuration of a photoelectric switch 20 according to an embodiment of the present invention. The configuration of the photoelectric switch 20 will be explained. For example, light from a light source 21 realized by a light emitting diode or the like is transmitted via a light projecting light 7 eyeper 22, is focused by a sphere X'23, and is directed to the object to be detected.
4.

The reflected light from the object to be detected 24 is focused by a ball lens 25 and input into a pair of light receiving optical fibers 26a and 26b. Here, the bulb X'25 and a pair of light receiving lights 7
Eyebars 26a and 26b constitute optical means.

The light transmitted through the optical fiber 26 is transmitted to light receiving elements 27a and 27b (collectively referred to as 27) which are light receiving means.
is incident on the The light receiving elements 27m+ and 27b output signals at a level corresponding to the amount of incident light.

These outputs are amplified by amplifier circuits 28a and 28b, respectively, and voltages Vl and V2 are input to an arithmetic circuit 29, respectively. The arithmetic circuit 29 performs an arithmetic operation to obtain V2/v1. The output of the arithmetic circuit 29 is given to the non-inverting terminal of the comparator circuit 30, and the inverting terminal of the comparator circuit 30 is given to the
A reference voltage VC is provided. The output from the comparator circuit 30 is connected to a display device, for example, and displays whether or not the object to be detected 24 is detected. Here, the calculation circuit 29 and the 1 comparison circuit 30 constitute calculation means.

FIG. 2 is a simplified system diagram illustrating the operating state of the charging switch 20, and FIG. 3 is a graph illustrating the operating state of the charging switch 20. The operating state of the charging switch 20 will be explained with reference to FIGS. 1 to 3. Light projecting optical fiber 22, ball lens 23, and detected object 2 shown in the first diagram
4. A ball lens 25 and a pair of optical fibers 2 for receiving light.
6 a=26 b are arranged as shown in the second diagram. That is, the sphere X'23.25 and the detected object 24 are placed at a position where J triangulation can be performed.

When the detected object 24 is at the position indicated by virtual IIIA73, its reflected light enters near the midpoint between the optical fibers 26a and 26b. The detected object 24 is a solid line! It is closer to the ball lens 23 than the position indicated by 3, and is virtual! If it is at the position indicated by f4, most of the reflected light will be reflected by light 7.
The light enters the eyeper 26b. Also, the solid line J! in Figure 2! Regarding 3, the detected object 24 is opposite to the ball lens 23!
! , and is located at the position indicated by virtual #1!5, most of the reflected light is reflected by the optical
incident on .
'The object to be detected 24 is located on the virtual line J! At the position indicated by 4, the levels of the voltages V1 and V2 output from the amplifier circuits 28a and 28b in FIG. 11 are respectively shown by the line noro and the NOR in FIG. 3(1). Here, the reference voltage VC applied to the comparator circuit 30 is determined by the solid line in FIG. It is set as a level corresponding to the state at the position indicated by 3.

Therefore, the way the comparison circuit 30 appears is that the detected object 24 is shown in the solid line in FIG. 2 on the display device (not shown). It is displayed that it is not in the position indicated by 3.

When the detected object 24 is at the position indicated by the solid line 13 in FIG. 2, the levels of the output voltages Vl and V2 from the amplifier circuits 28a and 28b in FIG.
．． ! 9. Therefore, at this time, the value of the ratio of voltages Vl and V2 obtained by calculation in the calculation circuit 29 of FIG. 1 is basically 1, and the output from the comparison circuit 30
It is displayed on the display device that the detected object 24 is located at the position indicated by the symbol $1'3 in FIG.

The detected object 24 is the virtual line in FIG. 2! 5, the voltages Vl and V2 output from the amplifier circuits 28a and 28b in FIG. 1 are on the line 3) in FIG. io,
, pii. Therefore, the value of the ratio of the voltages V] and V2 obtained by calculation in the arithmetic circuit 29 is basically smaller than 1. Therefore, the output from the comparator circuit 30 causes the detected object 24 to correspond to the solid line 13 in FIG. It is displayed that it is not in the indicated position.

In this manner, in the charging switch 20 shown in the first diagram, when the detected object 24 is at the position indicated by the solid line No. 3 in FIG. It is possible to detect the location without any problem.

Effects As described above, according to the present invention, light from an object to be detected is received and transmitted via optical means.

The plurality of light receiving means that receive light from the optical means are arranged so that the amount of incident light from the optical means changes when the position of the object to be detected changes. Also, from this light receiving means,
A signal at a level corresponding to the amount of incident light is output and given to the calculation means. The calculation means performs calculation processing related to the level of the output from each light receiving means. In this way, calculations related to the position of the detected object can be reliably detected without being hindered by, for example, the reflectance of the detected object.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing the configuration of a photoelectric switch 20 according to an embodiment of the present invention, FIG. 2 is a system diagram explaining the operating state of the photoelectric switch 20, and FIG. 3 is a system diagram showing the operating state of the charging switch 20. 4 is a system diagram illustrating the configuration of the prior art photoelectric switch 1, and FIG. 5 is a graph showing the relationship between the distance X in FIG. 4 and the amount of light received by the light receiving element 6. 20... Photoelectric switch, 21... Light source, 22...
Optical fiber for light projection, 24... Detected object, 26a, 26
b... Light receiving light 7 eyeball, 27a, 27b... Light receiving element, 29... Arithmetic circuit, 30... Comparison circuit, Vl
, V2...Voltage agent Patent attorney Shisan Keiichi part operator a engineer Figure 3 Figure 4 ■1 Figure 5 pressure'#X

Claims (1)

[Claims] Optical means that is interposed in the optical path of light from an object to be detected and that receives and transmits the light; and when the position of the object to be detected changes, the amount of incident light from the optical means changes. What is claimed is: 1. A photoelectric switch comprising: a plurality of light-receiving means arranged as shown in FIG.