JPH06123782A - Retro-reflective photoelectric switch - Google Patents

Abstract

PURPOSE:To enable detecting a body to be detected regardless of being a mirror body without using an expensive polarization filter by placing a plurality of light casting parts and light receiving parts with some intervals while making their emitting lights not parallel. CONSTITUTION:The emitting light 17 from a light casting part 12 and the emitting light 19 from a light emitting part 15 are constituted not to be in parallel. The emitting lights 17, 19 reflect at a regressive reflection plate 14 in the same direction as each incidence direction to be reflection lights 18, 20 and are received at light receiving parts 13, 16. If a detected body exists between a case 11 and the reflection plate 14, the emitting lights 17, 19 are shielded and never return to the light receiving parts 13, 16. In the case where the detected body is a mirror body, it causes normal reflection (with the same incidence angle and reflection angle), the light returns to one of light receiving parts 13, 16 and never returns to two light receiving parts 13, 16 at the same time (the first reflection light 18 and the second reflection light 20 are not in parallel). With this reason, by detecting the receiving light intensity at the light receiving part 13 and 16, the existence of a mirror body is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retroreflective photoelectric switch, and more particularly to a structure for detecting an object to be detected having a good surface reflection such as a mirror surface.

[0002]

2. Description of the Related Art In a retroreflective photoelectric switch, as shown in FIG. 3, a light projecting section 2 and a light receiving section 3 are housed in a case 1, and the light projecting section 2 and the light receiving section 3 are arranged so that their optical axes are parallel to each other. It is arranged. A regressive reflection plate 4 that returns reflected light in parallel with the incident light is installed at a predetermined distance from the light emitting / receiving units 2 and 3. When the object to be detected is not in the optical path, the light emitted from the light projecting unit 2 is reflected by the return reflection plate, and the reflected light is received by the light receiving unit 3
To receive light. As shown by the alternate long and short dash line in the figure, when the object B blocks its optical path and the reflected light is no longer given to the light receiving section 3, the object B is detected thereby. As described above, in the retroreflective photoelectric switch, if the surface reflection of the object B is small, the light from the light projecting unit is blocked, so that the object B can be detected. However, if the object to be detected is an object B having a large surface reflection such as a mirror, the light from the light projecting portion is directly reflected by the object to be detected B as shown by the broken line in FIG. 3, and the reflected light is received by the light receiving portion 3. It may be incident, causing malfunctions in relation to the position of the detected object B, the angle with the optical path, and the like.

FIG. 4 shows a photoelectric switch for detecting an object having a large surface reflection such as a mirror in order to prevent the above-mentioned malfunction. That is, polarizing filters 5 and 6 are provided in front of the light projecting unit 2 and the light receiving unit 3, respectively, and the return reflection plate 4 is installed facing the polarizing filters 5 and 6 at a predetermined distance. The polarization filter 5 installed in the front part of the light projecting part 2 has a function of transmitting only the P-polarized component (vertical polarization component) of the emitted light, and the polarization filter 6 installed in the front part of the light-receiving part 3 reflects it. It has a function of transmitting only the S-polarized component (horizontal polarized component) of the light. Projector 2
The light emitted from is polarized by the polarization filter 5 and only the light of the P polarization component is transmitted and travels. At this time, the light emitting / receiving unit 2,
When there is no object between the 3 and the retro-reflecting plate 4, the light of the P-polarized component arrives at the retro-reflecting plate 4 and is reflected there, and becomes the light of the P-polarized component and the S-polarized component. The reflected light reaches the polarization filter 6. This reflected light is polarized by the polarization filter 6 and only the S-polarized component is transmitted, and the light receiving unit 3
Is received by.

If there is an object between the light projecting units 2 and 3 and the return reflection plate 4 and it is a specular body, the light of the P-polarized component from the polarization filter 5 is reflected by the specular body. Is a P-polarized light component only, so that even if it reaches the polarization filter 6, it is blocked here and is not transmitted. Therefore, the light receiving unit 3
Does not receive reflected light, that is, it can detect the presence of an object (mirror surface).

[0005]

In the regressive reflection type photoelectric switch using the polarization filter, the light quantity emitted from the light projecting section 2 passes through the polarization filter 5 so that the light quantity is reduced to less than half, and the light receiving section 3 has the same structure. Also, since the amount of light is further reduced to half or less by passing through the polarization filter 6, the loss of the amount of light is large, and long-distance detection is impossible due to insufficient amount of light. Further, the polarization filter is expensive.

An object of the present invention is to provide a recursive reflection type proximity switch which does not use an expensive polarizing filter when detecting an object to be detected such as a mirror surface and does not reduce the light amount.

[0007]

According to the present invention, a case is provided with a first light projecting section, a first light receiving section, and a second light projecting section and a second light receiving section. A return reflection plate is installed at a position facing the installation surface of the light emitting / receiving unit and the second light emitting / receiving unit and separated by a predetermined distance, in which case the first light emitting / receiving unit and the second light emitting / receiving unit have a certain distance. The light is emitted from the first light projecting portion and the light emitted from the second light projecting portion is not parallel to each other.

[0008]

The light incident on the specular surface is specularly reflected (incident angle = reflection angle) to be reflected light, so that light having different incident angles has different reflection angles. Therefore, the reflected light emitted from the first and second light projecting portions and reflected by the mirror surface body does not return to the first and second light receiving portions at the same time. Further, as shown in FIG. 2, the retroreflective plate is composed of three orthogonal mirrors. Therefore, if outgoing light enters, it is reflected three times and reflected in the same direction as the incident direction. The light emitted from the light projecting portion is reflected by the retroreflective plate and enters the first light receiving portion and the second light receiving portion, respectively.

[0009]

1 is a schematic view showing an embodiment of the present invention. In the figure, a case 11 includes a first light projecting unit 12, a first light receiving unit 13, and a second light projecting unit 15 and a second light receiving unit 16.
2 sets of the light emitting and receiving parts are housed, and the first light emitting and receiving parts 12, 1
3, and the second light projecting / receiving sections 15 and 16 are installed with a space therebetween, and the light emitted from the first light projecting section 12 and the light emitted from the second light projecting section 15 are not parallel to each other. Is configured. Further, a regressive reflection plate 14 is installed at a position facing the light emitting / receiving surface of the case 11 and separated by a predetermined distance. Here, when the first emission light 17 and the second emission light 19 are emitted from the first light emission unit 12 and the second light emission unit 15, respectively, the second emission light is emitted from the first emission light 17. The light rays 19 are not parallel, and the respective light rays are reflected by the recursive reflection plate 14 in the same direction as the respective incident directions to become the first reflected light rays 18 and the second reflected light rays 20, respectively. , And is received by the second light receiving unit 16. The light reflected by the retroreflection plate 14 is reflected in the same direction as the incident direction, as shown in FIG. When a detected object is present between the case 11 and the return reflection plate 14, the first and second emitted lights are blocked by the detected object, and the reflected light does not return to the first and second light receiving portions 13 and 16. . When the object to be detected is a specular body, the reflected light is specularly reflected (the incident angle is equal to the reflection angle), so that it should return to either the first or second light receiving unit 13 or 16 in the direction of the plane of the specular body. At the same time, the first and second light receiving portions 13,
Since it does not return to 16 (the first reflected light 18 and the second reflected light 20 are not parallel), the amount of light received by the first light receiving unit 13 and the second light receiving unit 16 is detected to detect the mirror surface. It is possible to detect the presence.

[0010]

As described above, according to the present invention, two sets of light emitting / receiving parts are used so that the first emitted light and the second emitted light are not parallel to each other, thereby detecting the mirror surface without using an expensive polarization filter. Therefore, there is an advantage that the loss of light amount is eliminated, the set distance between the case and the retroreflector can be lengthened, and long distance detection can be performed.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention.

2A and 2B are diagrams showing a retroreflective plate, FIG. 2A being a diagram showing a state in which light is incident on and reflected by three orthogonal mirror surfaces; FIG.
Is a diagram showing a state in which two outgoing lights of the retroreflective plate are incident and reflected to be two reflected lights.

FIG. 3 is a schematic diagram of a conventional retroreflective photoelectric switch.

FIG. 4 is a schematic diagram of a retroreflective photoelectric switch having polarization filters on the front faces of the light projecting unit and the light receiving unit shown in FIG. 3, respectively.

[Explanation of symbols]

 11 Case 12 First Light Emitting Section 13 First Light Receiving Section 14 Regression Reflecting Plate 15 Second Light Emitting Section 16 Second Light Receiving Section

Claims (1)

[Claims] 1. A first light projecting portion and a first light receiving portion and a second light projecting portion and a second light receiving portion are built in a case, and the first light projecting and receiving portion and the second light receiving portion of this case are incorporated. A return reflection plate is installed at a position spaced apart from the installation surface of the light emitting and receiving unit by a predetermined distance, and the first light emitting and receiving unit and the second light emitting and receiving unit are installed with a certain distance.
A retroreflective photoelectric switch, wherein each of the light projecting and receiving parts is installed so that the light emitted from the first light projecting part and the light emitted from the second light projecting part are not parallel to each other.