JPS60146173A - Reflection type photoelectric switch - Google Patents

Abstract

PURPOSE:To enable the detection of an object to be detected even when it is mirror finished or in the proximity by checking the object being detected depending on whether or not the polarized plane of the detection light was turned by 90 deg.. CONSTITUTION:When an object to be detected is not interposed between a transparent plate 7 and a reflex reflector, the detection light 3 of a (p) polarized light 3p has the polarized plane thereof turned by 90 deg. with a reflex reflector, is reflected as the detection light 3 of the (s) polarized light 3s and returned to the transparent plate 7 again as parallel light beam. On the other hand, when the object being detected is interposed between the transparent plate 7 and the reflex reflector, the detection light 3 passing through the transparent plate 7 scatters never returning to the transparent plate 7 and hence, will not enter a light receiving element 4. When the object being detected is mirror finished, the detection light 3 reflects on the surface thereof and returns to the transparent plate 7. Here, the detection light 3 passes therethrough without being reflected as the polarized plane is in noway turned. Thus, the light receiving element 4 outputs a signal depending on the presence of the detection light 3 to cause a switching operation.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of the Invention The present invention relates to a reflective optical switch that detects an object by reflecting projected detection light.

(b) Prior art and its problems Conventionally, a reflective optical switch has a light emitter and a light receiver that are integrally formed, and a reflex light that faces the light emitter and receiver.
A reflector is provided, and when an object to be detected passes between the light emitting/receiving part, the flex, and the reflector, the amount of reflected detection light decreases, and this decrease in light amount detects the object and operates the switch. There is something.

However, with this reflective optical switch, if the object to be detected has a high reflectance such as a mirror surface, there is a difference between the amount of detected light reflected by the reflex reflector and the amount of detected light reflected from the object. There is a problem in that the switch does not operate because the light intensity does not occur, that is, the light amount does not decrease, and it cannot be detected.

Furthermore, in a parallel twin-lens type reflective optical switch, since the light emitting element and the light receiving element are arranged side by side, the optical axes of the pixel elements do not coincide with each other. Therefore, a so-called dead zone due to parallax occurs at extremely short distances. In other words, if the detection light emitted from the light projecting element is near the object to be detected, it will be reflected back to the light projecting element and will not return to the light receiving element.

In this case, it is necessary to maintain the detection distance to a predetermined value or more, and there is a problem that the detection range becomes narrow.

(c) Purpose of the Invention This invention was made in view of the above points, and detects the object to be detected depending on whether the plane of polarization of the detection light is rotated by 90 degrees. The purpose of L1 is to provide a reflective photoelectric switch that can be detected even if the object is nearby.

(d) Structure and effect of the invention In order to achieve the above-mentioned object, the present invention includes a light projecting element that emits detection light, and a light projecting lens that is provided near the light projecting element and converts the detection light into parallel light. A transparent plate is provided to intersect this parallel ray at Brewster's angle, and the detection light transmitted through the transparent plate is provided at a distance from the transparent plate on the detection side, and the plane of polarization is rotated by 90 degrees. a reflective object that reflects;
It includes a light receiving element that receives the detection light reflected by the transparent plate on the other side of the detection light returning from the detection side, and detects the detection object between the transparent plate and the reflective object based on the presence or absence of rotation of the plane of polarization. It is composed of

Therefore, according to the present invention, the object to be detected can be detected regardless of the amount of light received by the light receiving element.
Even if the object to be detected has a high reflectance, such as a mirror surface, it can be reliably detected.

In other words, even if the amount of light does not decrease, the plane of polarization does not rotate, so the object to be detected can be detected accurately, and the switch operation can be performed accurately.

In addition, since the detection light reflected by the transparent plate is received by the light receiving element, even if the side ratio is All, it can be reliably detected without causing a so-called dead zone, and the detection range can be widened. .

(e) Description of Embodiment An embodiment of the present invention will be described in detail below with reference to the drawings.

As shown in FIG.
The device detects the detected object and operates the switch.

In this photoelectric switch 1, a light emitting element 2 and a light receiving element 4 are connected to a light emitting lens 5, a light receiving lens [j and a transparent plate 7,
It is housed in a main body case (not shown), and a reflex reflector 8 (offending object) is provided on the side to be detected.

The light projecting element 2 emits detection light 3, and the emitted detection light 3 is natural light having a random polarization plane.

The light projection lens 5 is provided near the light projection element 2,
The detection light 3 is made into parallel light beams.

The transparent plate 7a is formed by stacking a plurality of dielectric flat plates that are transparent isotropic media, for example, transparent polycarbonate 1 flat plates 7a. This transparent plate 7 is connected to the projection lens 5.
It is installed so that the detected parallel light beams 3 that have passed through it intersect at the Brewster angle θB, and the p-polarized light 3 of the detected light beams 3
The p-eyes are transparent.

In other words, as shown in FIG. 2, when the angle of incidence of the detection light 3 incident on the transparent plate 7 is equal to the Brewster angle θB,
The reflectance of the p-polarized light 3p vibrating within the incident plane at the boundary surface 7b becomes zero, and on the other hand, the detection light 3 reflected at the boundary surface 7b
Only the S-polarized light 3s vibrates in a plane perpendicular to the incident plane. Therefore, the proportion of the detection light 3b and the p-polarized light 3p passing through the transparent plate 7 increases. As shown in FIG. 3, a plurality of polycarbonate flat plates 7a (transparent dielectric plates)
When the transparent plate 7 is configured by arranging the light beam at the Brewster angle θB, the transmitted detection light 3 becomes almost only p-polarized light 3p.

Here, the Brewster angle θB is expressed by the following equation, assuming that the refractive index of the transparent plate 7 is n, and the surrounding refractive index no is 1.

tanθB=n And in the case of the transparent polycarbonate flat plate 7a, the refractive index n
is 1.58, so the Brewster angle θB is 57.6
degree.

Further, the reflectance Rs of the S-polarized light 3S entering the boundary surface 7b is expressed by the following equation.

R3-(n2-1) 2/ (n2+1) 2 The reflex reflector 8 is provided on the detection side with a predetermined distance from the transparent plate 7, and the reflex reflector 8 and the transparent plate 7 A detected object (not shown) is interposed between them. This reflex reflector 8 reflects the detection light 3, which is a parallel light beam, and is configured to rotate the plane of polarization by 90 degrees. That is, the detection light 3 of p-polarized light 3p that has passed through the transparent plate 7 is polarized into S-polarized light 3S and reflected to the inner transparent plate 7.

The light-receiving lens 6 is provided near the light-receiving element 4 and is configured to focus the detection light 3 reflected from the detection side on the transparent plate 7 onto the light-receiving element 4 .

Of the detection light 3 returning from the detected side, the detection light 3 from the reflex reflector 8 is S polarized light 3s,
Moreover, since it is incident on the transparent plate 7 at the Bruscoux angle θB,
This detection light 3 is reflected and focused on the light receiving element 4 via the light receiving lens 6.

The light-receiving lens 4 is configured to output a signal based on the detected light 3 that it receives, and is configured to perform a switch operation based on this output signal.

Next, the operation of this photoelectric switch 1 will be explained.

First, the detection light 3 emitted from the light projecting element 2 is natural light having a random polarization plane, and passes through the light projecting lens 5 and enters the transparent plate 7 as parallel light rays as natural light.

Subsequently, this transparent plate 7 intersects the incident detection light 3 at the Brewster angle θB, so that the S-polarized light 3s of the detection light 3
is reflected, and only p-polarized light 3p is transmitted. In particular, the transparent plate 7
Since it is constructed by stacking a plurality of transparent polycarbonate flat plates 7a, only the p-polarized light 3p is transmitted and is irradiated onto the reflex reflector 8.

At this time, if there is no object to be detected between the transparent plate 7 and the reflex reflector 8, the detection light 3 of the p-polarized light 3p
The plane of polarization is rotated by 90 degrees by the reflex reflector 8, and the light is reflected as detection light 3 of S-polarized light 3S, and returns to the transparent plate 7 again in the state of parallel light rays.

Subsequently, this S-polarized light 3S detection light 3 is incident on the transparent plate 7 at the Brewster angle θB, so it is reflected by the transparent plate 7, and for example, about 30% of the detection light 3 is condensed by the light receiving lens 6. The light is incident on the light receiving element 4.

On the other hand, when the object to be detected is interposed between the transparent plate 7 and the reflex reflector 8, the p-polarized light 3p transmitted through the transparent plate 7
The detected light 3 does not return to the transparent plate 7 again but is scattered and does not enter the light receiving element 4. Further, when the object to be detected is a mirror surface, the detection light 3 is reflected by the mirror surface and returns to the transparent plate 7. At this time, since the detection light 3 remains p-polarized light 31) with its plane of polarization not rotated, it enters the transparent plate 7 at the Brewster angle θB and is transmitted without being reflected.

Therefore, the light does not enter the light receiving element 4.

Therefore, the light receiving element 4 outputs a signal depending on the detection light 3 (1), and performs a switch operation based on this signal.

In this embodiment, the reflex reflector 8 is used as the reflecting object, but the reflecting object of the present invention is not limited to the flex reflector 8 as long as the plane of polarization can be rotated by 90 degrees.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic diagram of a photoelectric switch, and FIG. 2 is a diagram showing the reflection and reflection of detection light on a transparent plate.
FIG. 3 is a principle diagram showing the state of reflection and transmission of detection light on a transparent plate made of a plurality of transparent polycarbonate flat plates. 1: Photoelectric switch, 2: Light emitting element, 3: Detection light, 3p: P polarized light, 3s: S polarized light, 4: Light receiving element, 5: Light emitting lens, 6: Light receiving lens, 7: Transparent plate, 7a: Transparent Polycarbonate flat plate, 8: Reflex reflector.

Claims (2)

[Claims] (1) A light emitting element that emits detection light, a light emitting lens provided near the light emitting element to convert the detected light into parallel light, and a transparent plate provided to intersect the parallel light at Brewster's angle. , a reflective object that is provided on the detection side with a gap from the transparent plate and reflects the detection light that has passed through the transparent plate with its polarization plane rotated by 90 degrees; 1. A reflective optical switch, comprising: a light-receiving element that receives detection light reflected by the transparent plate, and detects an object to be detected between the transparent plate and the reflective object based on the presence or absence of rotation of a plane of polarization. (2) The reflective optical switch according to claim 1, wherein the reflective object is comprised of a reflex reflector.