JPH0452919Y2 - - Google Patents

Description

[Detailed Description of the Invention] <<Technical Field of the Invention>> The present invention relates to a reflective photoelectric switch in which a light emitting part and a light receiving part are housed in one case. This invention relates to a reflective photoelectric switch that is improved.

<Prior art and its problems> A twin-lens reflective photoelectric switch that has a light emitter and a light receiver detects the reflective object by reflecting the light from the light emitter on a reflective object and entering the light receiver. conduct,
This switch operation is performed when an object that blocks light enters between the reflecting object and the reflecting object. In this reflective photoelectric switch, as the reflective object is located closer than a certain distance to the light projector and the light receiver, the amount of light received by the light receiving element out of the light reflected by the reflective object decreases due to parallax. In particular, if a reflective tape is used as a reflex reflector, the amount of light received by the reflex reflector does not reach the detection level of the light receiving element, as shown in the graph of received light amount vs. distance of the reflex reflector shown in Figure 1. This method has the disadvantage of creating a distance that cannot be set, a so-called dead zone.
This problem is caused by the inability to align the optical axes of the light projecting section and the light receiving section. Also, when the light receiving section receives light diffusely reflected from a reflective object, the relationship between this distance and the amount of received light is reversed when the reflecting object is closer than a certain distance from the light projecting section and the light receiving section. Depending on the detection level of the light receiving section, an undetectable distance, so-called dead zone, occurs as shown in the graph of the amount of received light versus the distance to the reflecting object shown in FIG.

Therefore, for example, there is a method of narrowing the gap between the light emitting part and the light receiving part so that the reflected light from a reflective object located at a close distance can be detected, or by widening the directivity angle of the lenses of the light emitting part and the light receiving part A method or the like is devised to enable detection of reflected light from a reflective object located at a close distance. However, these methods result in sacrificing the performance of the reflective photoelectric switch when the reflective object is located far away from the light receiving part, and even when the reflective object is located at a close distance. The above drawbacks cannot be sufficiently improved. In other words, a problem has arisen in which the reflective photoelectric switch cannot operate accurately.

[Purpose of the invention] The present invention was developed in view of the above-mentioned problems, and its purpose is to make it possible for the light receiving element to It is an object of the present invention to provide a reflective photoelectric switch which prevents a decrease in the amount of received light and eliminates or reduces the unsettable distance of a reflex reflector and the undetectable distance of a reflective object that diffusely reflects, so-called dead zone.

<<Configuration and Effects of the Invention>> In order to achieve the above object, the reflective photoelectric switch of the present invention includes a light emitting element, a light receiving element, and a light emitting element located opposite to and adjacent to each of the elements. A reflective photoelectric switch comprising a lens and a light-receiving lens, including a transmission optical element that is provided adjacent to each of the lenses and changes the traveling direction of the emitted light passing through the light-emitting lens to the light-receiving lens. Therefore, when the reflective object is far away, the emitted light passes through the projecting lens and the receiving lens, and when the reflecting object is close, the emitted light passes through the projecting lens and the projecting/receiving lens. Since light can enter the light-receiving element through the transmitting optical element and the light-receiving lens provided adjacent to the lens, no dead zone of reflective objects occurs, and the reflective photoelectric switch can operate accurately.

<<Example of the invention>> Hereinafter, an example of the invention will be described in detail based on the drawings.

FIG. 3 is a diagram illustrating the principle of a reflective photoelectric switch according to an embodiment of the present invention. In the figure, 1 is a light projecting element, and the light emitted from the light projecting element 1 is directed at a predetermined angle to the central part of the projecting lens 3 and the reflective object 2 side so that the light emitted from the light projecting element 1 is incident on a reflective object 2, for example, a reflective tape. Transparent resin flat plates 5 each having a cylindrical lens 4, which is a transmissive optical element that refracts light, are arranged close to each other. A light-receiving lens 6 is arranged so that the incident light is reflected by the reflective object 2, and after the reflected light passes through the resin flat plate 5, it is condensed. A light-receiving element 7 is arranged to receive the light collected by the light-receiving lens 6.
Incidentally, the light projecting element 1 and the light receiving element 7 are arranged on the optical axes of the light projecting lens 3 and the light receiving lens 6, respectively. That is, they are located at the focal points of the light projecting lens 3 and the light receiving lens 6, respectively. FIG. 4 is a sectional view of a reflective photoelectric switch in which the above-mentioned structure is housed in a single case.

Next, the operation of the reflective photoelectric switch will be explained based on the above-mentioned principle. First, let's talk about the case where the reflective object 2 is located far away from the reflective photoelectric switch.The light emitted from the light projecting element 1 becomes almost parallel light 8 at the light projecting lens 3, and most of this is reflected by the resin flat plate. 5. Go straight without bending. Subsequently, the parallel light 9 transmitted through the resin flat plate 5 enters the reflective object 2, becomes reflected light 10 in substantially the same direction, and is transmitted through the resin flat plate 5. Most of the light that has passed through the flat resin plate 5 on the side of the light receiving lens 6 is focused on the light receiving element 7 by the light receiving lens 6. At this time, the light receiving element 7 can receive a sufficient amount of light for the detection level. It should be noted that almost no light is refracted by the cylindrical lens 4 provided at the center of the resin flat plate 5 and focused on the light receiving element 2 . That is, since the parallel light 8 is refracted by the cylindrical lens 4, the position where it connects with the light receiving lens 6 is shifted from the light receiving element 7.

On the other hand, when the reflective object 2 is located at a close distance from the reflective photoelectric switch as shown by the broken line, the light emitted from the light emitting element 1 becomes almost parallel light 8 at the light emitting lens 3, and most of this is made of resin. It passes straight through the flat plate 5. This transmitted light becomes substantially parallel light 11 at the reflecting object 2. However, since the reflecting object 2 is located at a close distance, this parallel light 11 hardly reaches the light receiving lens. Furthermore, a portion of the parallel light 8 is refracted by the cylindrical lens 4 and reflected by the reflecting object 2.
The incident light 12 has a slight angle with respect to the incident light 12. Therefore, this light 12 becomes reflected light 13 that is reflected at substantially the same reflection angle as the above-mentioned angle, and becomes substantially parallel light at the cylindrical lens 4. Then, this parallel light is focused on the light receiving element 7 by the light receiving lens 6, and the reflecting object 2 is detected. At this time, although only a portion of the light emitted from the light emitting element 1 is received by the light receiving element 7, the density of the light is high because the reflective object 2 is located at a close distance, so the light receiving element 7 receives the light. A sufficient amount of light can be received for the detection level of the reflective object 2. The above is also clear from the graph of the distance to the reflective object versus the amount of received light reflected from the reflective object shown in FIG. In the graph, (I) is the amount of light received by the cylindrical lens 4, () is the amount of light received using most of the light emitting lens 3 and the light receiving lens 6, and () is the amount of light received by the cylindrical lens 4. It shows the total amount of received light obtained as the sum of the graphs I) and (). In other words, as the reflective object 2 approaches the reflective photoelectric switch, the amount of received light decreases sharply as shown in graph (), and the amount of received light in graph (I) compensates for this. Therefore, the amount of light received by the light receiving element 7 sufficiently reaches the detection level, and the dead zone is removed.

Further, although the cylindrical lens 4 extends over the light projecting lens 3 and the light receiving lens 6, it may be biased to either side. In other words, the same effect as described above can be obtained even if the optical path of only one of the light projecting lens 3 and the light receiving lens 6 is provided to be changed. Further, a prism or a lens having a shape different from the shape described above may be used so that the light receiving element 7 receives an amount of light corresponding to the detection level. The reflective photoelectric switch configured as described above can perform switching operations accurately over a short distance to a long distance.

[Brief explanation of the drawing]

Figures 1 and 2 are graphs showing the results detected using a conventional reflective photoelectric switch;
Figure 4 is a diagram explaining the principle of an embodiment of the present invention.
This figure is a sectional view of a reflective photoelectric switch constructed based on the principle of FIG. 3, and FIG. 5 is a graph showing the results of detection using the reflective photoelectric switch of the present invention. 1... Light projecting element, 2... Reflective object, 3... Light projecting lens, 4... Cylindrical lens, 5... Resin flat plate, 6... Light receiving lens, 7... Light receiving element.

Claims (1)

[Scope of utility model registration request] A reflective photoelectric switch comprising a light emitting element, a light receiving element, and a light emitting lens and a light receiving lens provided opposite each of the elements and adjacent to each other; . A reflective photoelectric switch comprising: a transmission optical element that changes the traveling direction of the emitted light passing through the light projecting lens to the light receiving lens.