JPS5866879A - Reflection type photoelectric switch - Google Patents

Abstract

PURPOSE:To elevate an S/N ratio in the photodetecting side, and to widen a detecting range, by using plural light emitting elements, and giving a difference to light emission of the light emitting element so that a photodetecting state of a photodetector becomes a differential type. CONSTITUTION:Lenses 3, 3' of a projector 1 and a photodetector 2 are turned to a wall surface 4, respectively, and the photodetector 2 is fitted to such a position as receives both modulated light P1, P2. In this case, the modulated light P1 and P2 which a photodetector R1 receives are adjusted so that the intensity becomes same, but in case when it does not become equal by only adjusting the direction, the degree of light emission of a light emitting element D1 or D2 is adjusted. Only when the photodetecting intensity is same, an output of the element R1becomes a DC portion only. In case when it is set as a stationary state, when a substance to be inspected enters into the beam of light of the modulated light P1 or P2, photodetecting balance of each modulated light P1, P2 which the element R1 receives gives way, and from the element R1, an AC portion is outputted. Accordingly, by detecting these DC and AC portions, a desired detecting output signal can be obtained.

Description

Detailed Description of the Invention The present invention is mainly used for intruder detection, in which light emitted from a projector is reflected by an object, this reflected light is received by a receiver, and a signal is issued by detecting a change in the amount of received light. This invention relates to a reflective photoelectric switch used as a reflective photoelectric switch.

Conventional reflective photoelectric switches are generally integrated, with the emitter and receiver housed in one container. Those that do not use a reflector have a short detection distance, and those that do use a reflector have a short detection distance. However, they have the disadvantage that objects with high reflectance cannot be detected reliably.Furthermore, both have narrow detection ranges due to their structure, and changes in the amount of light received are of the differential detection type, so it is difficult for objects to be detected to stop. If the state continues, the detection signal will no longer be output, making it difficult to use it for intruder detection.

The present invention solves the above-mentioned conventional drawbacks, and aims to provide a reflective photoelectric switch that has a wide detection range and can reliably detect an object to be detected regardless of its moving speed, and is described in detail below. .

FIG. 1 shows the basic form of the present invention, in which a convex lens 3 is used as the optical system of the projector 1, and two light emitting elements +DI are used as light sources at or near the focus.

D2 is arranged, each light emitting element + DI, D2 is
As shown in O), modulated lights PI and P2 (infrared pulsed lights) having mutually opposite phases are emitted. Also, receiver 2
A convex lens 3' is also used in the optical system, and a light receiving element R1 is arranged at or near the focal point of the convex lens 3'.

The lenses 3 and 3' of the emitter 1 and the receiver 2 are connected to the wall surface 4, respectively.
The light receiver 2 receives the two-way dimming signal P1. reflected from the wall surface 4. It is attached at a position to receive P2. In this case, the direction of the emitter 1 or the receiver 2 is adjusted so that the intensity and pulse height of one modulated light received by the light receiving element R1 is the same as that of the other modulated light P2, but it is not possible to adjust the direction alone. If the received light intensities of the modulated lights PI and P2 are not equal, the luminous intensity of the light emitting element D1 or D2 is adjusted. When the received light intensity of P2 is the same each time the light receiving element R1 receives the modulation, the output of the light receiving element R1 becomes only the DC component as shown in FIG. 3(C). If this is a steady state, if a detected object (such as an intruder) enters the beam of the previous modulation or P2, the reception balance of each modulated light PI and P2 received by the light receiving element R1 will be disrupted, and the light receiving element R1 will
From 1, the exchange meeting is output. Therefore, an electric port for distinguishing between direct current and alternating current is provided after the light receiving cable R1: 18 (not shown)
By connecting , the desired output signal can be obtained.

Contrary to the above, in a steady state, a difference is set in the received light intensity of R2 before each modulation received by the light receiving element R1, and the detected object receives the modulated light P! Or when you enter the beam of light on P2,
The received light intensity may be the same. In this case, the output from the light receiving element R1 becomes as shown in FIGS. 3(d) to (c).

Moreover, the same thing can be said even if the light emission wavelengths of the light emitting elements DI and D2 are made different. In this case, if the light receiving element R1 receives light of different wavelengths at the same time, the light receiving element R1
Since the output current flows from the upper light receiving element R1 where the light of one of the wavelengths is blocked, the output current no longer flows from the upper light receiving element R1.
This provides the desired output.

In Fig. 2, the optical system of the emitter 1 and the receiver 2 is composed of a plurality of concave mirrors 5.5' (curved mirrors, parabolic mirrors, etc.), and each optical axis XI, X2..., X1lX2・・・・・・
are facing in different directions, and two light receiving elements R1 and R2 are arranged at or near the focal point of the optical system 5' of the light receiver 2, so as to receive light corresponding to each light emitting element DI+D2. . In this case, which light receiving element R1
, R2 is blocked first, the moving direction of the object to be detected can be detected.
It is also possible to amplify the output from 2 and balance the two on the light receiving side.

Although the above description has been made using two light-emitting elements and two light-receiving elements, the present invention is not limited to this, and even if each element has three or four elements, the same effect can be achieved.

As described above, in the present invention, a plurality of light emitting elements are used, and the light emission of each light emitting element is made different so that the light receiving state of the light receiving cable is a differential type, so that the SNh on the light receiving side is improved. However, the detection distance can be increased, and the optical axes of the projector and receiver can be set in a plurality of directions in different directions, making it possible to widen the detection range. Roughly speaking, if the object to be detected remains stopped within the detection range, the balance of light reception is different from the initial one, so the detection signal has the characteristic of being continuously output.

[Brief explanation of the drawing]

FIG. 1 is a diagram of the photoelectric switch according to the present invention, FIG. 2 is a diagram of the same according to another embodiment, and FIG. 3 is a waveform diagram showing an explanation of the operation. 1... Floodlight. 2... Light receiver. 3...
····Optical system. 4...Wall surface. DI-, D2・
...Light emitting element. R1, R2... Light receiving element patent applicant

Claims (1)

[Claims] 1) A reflective photoelectric switch in which light emitted from a projector is reflected by an object, the reflected light is received by a receiver, and a change in the amount of received light is detected and a signal is output. A reflective photoelectric switch characterized in that a plurality of light emitting elements that emit modulated light of mutually opposite phases are arranged at or near the focal point of the system. 2) In a reflective photoelectric switch, the light emitted from the projector is reflected by an object, the reflected light is received by the receiver, and a change in the amount of received light is detected and a signal is output. Nearby is a reflective photoelectric switch featuring several light-emitting elements, each of which emits the light of a rising wave. 3) A reflective photoelectric switch according to claim 1 or 2, wherein the optical system of the projector and/or receiver has optical axes in a plurality of different directions. 4) A reflective photoelectric switch characterized in that a plurality of light receiving elements are arranged at or near the focal point of the optical system of the light receiver.