JPS5967480A - Optical fiber type photoelectric switch - Google Patents

Abstract

PURPOSE:To perform the adjustment of detection sensitivity in good workability by one person, by controlling the gain of a detect circuit by guiding light reflected in the vicinity of a detecting surface to a light receiving element other than a light receiving element for detecting an object to be detected. CONSTITUTION:The modulated light from a light receiving element 22 retrogrades through an optical fiber 24 by the driver 47 in the vicinity of the detecting surface of the optical fiber 24 to be received by a light receiving element 27 other than a light receiving element 26 for detecting an object 45 to be detected and, when the light receiving integrated value of the modulated light exceeds a discrimination level, an oscillation circuit 40 and a gain control circuit 41 respond to the level discrimination circuit 39 of a gain control means 30 to stepwise control the gain of the amplifier 31 of a detect circuit 29. On the other hand, when the object 45 to be detected is detected by the light receiving circuit 26 and the circuit 29 and the output from a level discrimination circuit 35 is present, a signal not synchronous to the drive pulse of a pulse oscillator 21 or a DC signal is piled up to a light emitter 23 and the detection of the object 45 is judged by the more brightness of the surface 43. By this mechanism, sensitivity adjustment to the object to be detected is performed in good workability by one person.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber type photoelectric switch, and more particularly to an optical fiber two photoelectric switch having a detection sensitivity adjustment function for an object to be detected.

Referring to FIG. 1, the prior art optical fiber type photoelectric switch includes a pulse oscillation circuit 1, a light emitting element 2, a light emitting circuit 3, optical fibers 4 and 5, a light receiving element 6, a light receiving circuit 7 and a detection circuit 8. Be prepared. In order to adjust the detection sensitivity of the detected object 9 in the detection area, the light emitting circuit 3 is provided with a variable resistor 10. By angularly displacing the slider 11 connected to the axis of the variable resistor 10, light is emitted. The driving current of the element 2 is controlled so that only the object 9 to be detected is detected. The object to be detected 9 and the knob 11 are within reach, that is, the optical fiber 4.
If the optical fiber 4.5 is short, it is possible to adjust the detection sensitivity by one person, but if the optical fiber 4.5 is long, the detection sensitivity can be adjusted by one person.
Detection sensitivity must be adjusted by talking to each other or using a transceiver, and if the two people are still not breathing in sync, the adjustment process takes time and is inefficient.

An object of the present invention is to provide an optical fiber photoelectric switch that solves the above-mentioned technical problems, improves workability, and allows one person to adjust detection sensitivity.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 2 is a block circuit diagram of one embodiment of the present invention. The reflective optical fiber 2 photoelectric switch has a pulse oscillation circuit 2.
1, light emitting element 22, light projection circuit 23, optical fiber 24, 2
5, light receiving elements 26, 27, light receiving circuit 28, detection circuit 29
and gain control means 30. The detection circuit 29 includes an amplifier circuit 31, a waveform shaping circuit 32, a signal processing circuit 33, an integrating circuit 34, and a level discrimination circuit 35. The gain control means 30 includes a light receiving circuit 36, an amplifier circuit 37, and an integrating circuit 3.
8, a level discrimination circuit 39, an oscillation circuit 40, and a gain control circuit 41. The power supply circuit 42 is the pulse oscillation circuit 2
1. The light emitting circuit 23, the light receiving circuit 28, the detection circuit 29, and the gain control means 30 are powered.

The pulse oscillation circuit 21 outputs a 2 KHz pulse signal with a predetermined duty of 10%, for example, to the light projection circuit 23 and the signal processing circuit 33 of the detection circuit 29. Light emitter circuit 2
3 drives a light-emitting element 22 such as a light-emitting diode that emits visible light in response to a pulse signal from a pulse oscillation circuit 21 . Modulated light corresponding to the pulse signal from the light emitting element 22 is projected onto the detection area via the detection surface 43 of one of the optical fibers 24 of the pair.

Light from the detection region via the detection surface 44 of the other optical fiber 25 is applied to a light receiving element 26 such as a phototransistor. A photocurrent flows through the light receiving element 26 according to the amount of light received, and this photocurrent is provided to the light receiving circuit 28. The light receiving circuit 28 passes only the photocurrent corresponding to the alternating current component, that is, the modulated light, and blocks the photocurrent corresponding to the external light, which is the direct current component.

The amplification factor of the amplification circuit 31 of the detection circuit 29 exceeds the discrimination level of the level discrimination circuit 35 when there is a detected object 45 in the detection area, so that a detection signal, for example, a signal of No. 1 level, is output from the level discrimination circuit 35. Further, the gain control means 30 controls the detection signal so that the detection signal does not exceed the discrimination level of the level discrimination circuit 35 and is not outputted from the level discrimination circuit 35 when there is no detected object 45 in the detection area.

The output from the light receiving circuit 28 that has been amplified by the amplifier circuit 31 is waveform-shaped by a waveform shaping circuit 32 and then provided to a signal processing circuit 33 . The waveform shaping circuit 32 also has a binary level discrimination function, and when the detection signal from the level discrimination circuit 35 is strong, it discriminates the level at a high discrimination level.
When there is a detection signal from the level discrimination circuit 35, level discrimination is performed at a low discrimination level. In other words, a single moving detection object 45 is prevented from being mistakenly detected as a plurality of objects.

The signal processing circuit 33 uses the pulse signal from the pulse oscillation circuit 21 as a synchronization signal, and sets the duty of only the signal from the waveform shaping circuit 32 synchronized with this synchronization signal to 80%, for example.
Extend it to. Further, signals due to pulsed external light that are not synchronized with this pulse signal are removed by this signal processing circuit 33. The output from the signal processing circuit 33 is sent to the integrating circuit 34.
and level discrimination is performed by a level discrimination circuit 35. The output from the level discrimination circuit 35 is given to an output circuit 46 such as an open collector for driving an external load such as a relay (not shown) and to the light projection circuit 23.

Only when the light emitting circuit 23 receives a detection signal from the level discrimination circuit 35, it detects a signal that is not synchronized with the pulse signal shown by the broken line in Fig. 3+1) or a DC signal shown by the broken line in Fig. 37 (2). The light emitting element 22 is driven by superimposing the two. Note that the solid line indicates a pulse signal. Therefore, when the detection signal is output from the level discrimination circuit 35, the detection surface 43 of the optical fiber 24 appears to be very bright.

The optical fiber 24 is Y-branched. In adjusting the detection sensitivity of the detected object 45, the detection surface 43 of the optical fiber 24
When an object 47 such as a screwdriver is placed nearby, the light emitting element 22
The modulated light is reflected by the object 47 and guided to the light receiving element 27 via the branch portion 48 of the optical fiber 24 .

The output from the light receiving element 27 is applied to a gain control means 30. The light receiving circuit 36 of the gain control means 30 is similar to the light receiving circuit 2.
8, only the AC component is allowed to pass. The output of the light receiving circuit 36 is amplified by the amplifier circuit 37 and
and level discrimination is performed by a level discrimination circuit 39.

When the output of the integration circuit 38 exceeds the discrimination level of the level discrimination circuit 39, the level discrimination circuit 39 causes the oscillation circuit 40 to output two pulses as shown in FIG. 4 (+), for example. The gain control circuit 41 increases the amplification factor of the amplifier circuit 31 of the detection circuit 29 by 1 within a predetermined range as shown in FIG. 4(2) every time two pulses are input from the oscillation circuit 40.
Control to increase/decrease in steps. Note that the amplifier circuit 3
The amplification factor of 1 may be increased or decreased as shown in FIG. 4(3) to FIG. 4(6).

Therefore, the detection level adjustment of the detected object 45 can be performed by one person in the detection area according to the flow shown in FIG. In the first step n1, the object to be detected 45 is placed in the detection area. Then, in a second step n2, an object 47 is placed on the detection surface 43. In the third step n3, the amplification factor of the amplifier circuit 31 is automatically changed. 4th step n
4, the object 47 is removed. In the fifth step n5, it is determined whether the object to be detected 45 has been detected.

That is, the determination is made based on whether the detection surface 47 has become bright. If the object to be detected 45 is not detected, the second step n2
Go back and repeat.

If the object to be detected is detected, the process proceeds to a sixth step n6, and the object to be detected 45 is removed from the detection area. Then the seventh step n7
Then, it is determined whether other objects in the detection area have been detected. That is, if the detection surface 47 remains bright, the amplification factor has increased too much, and the process returns to the first step n1 and repeats.

If the detection surface 47 becomes dark, that is, if no other object in the detection area is detected, the detection level adjustment is finished.

As another embodiment of the present invention, another optical fiber may be interposed between the detection surface 43, 44 and the light receiving element 27, or an optical splitter may be used as the optical fiber means. Further, although the present embodiment has been described as a reflection type switch, it may be operated as a transmission type optical fiber type photoelectric switch.

As described above, according to the present invention, detection sensitivity adjustment can be performed by one person with good work efficiency. The optical fiber can be made much longer, the installation range of the optical fiber-to-photoelectric switch can be expanded, and the influence of electrical noise can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of the prior art, FIG. 2 is a block circuit diagram of an embodiment of the present invention, FIG. 3 is a waveform diagram showing the drive current for driving the light emitting element 22, and FIG. 4 is the amplifier circuit 31. FIG. 5 is a diagram showing a flow of adjusting the detection level of the object 45 to be detected. 21... Pulse oscillation circuit, 22... Light emitting element, 23
...Light projection circuit, 24.25...Optical fiber, 26,
27... Light receiving element, 28.36... Light receiving circuit, 29
...Detection circuit, 30...Gain control means, 31.37
...Amplification circuit, 32...Waveform shaping circuit, 33...
Signal processing circuit, 34.38...Integrator circuit, 35.39
...Level discrimination circuit, 40...Oscillation circuit, 41...
・Gain control circuit, 45...Detected object, 47...Object, 48...Branch partial agent Patent attorney Kei Nishi Ichibu/+T+1/S
/S-to

Claims (1)

[Claims] A pulse oscillation circuit that outputs a pulse signal with a predetermined duty, drives a light emitting element that emits visible light in response to the pulse signal, and detects one of the optical fibers forming a pair from the light emitting element. A light projecting circuit that projects modulated light to a detection area through a surface, a light receiving element that receives light from the detection area through the detection surface of the other optical fiber, and a light receiving device that allows only the alternating current component of the output of the light receiving element to pass through. amplifying the output of the circuit and the light receiving circuit, and extending and smoothing the duty of the amplified output from the light receiving circuit in synchronization with the pulse signal,
In an optical fiber photoelectric switch equipped with a detection circuit for detecting an object to be detected in a detection area based on a detection signal obtained by further level discrimination, the detection of another light receiving element different from the light receiving element and the object to be detected is performed. an optical fiber means for guiding the modulated light reflected from the vicinity of the detection surface to the other light receiving element during sensitivity adjustment; gain control means for sequentially changing the amplification factor of the detection circuit to an amplification factor for detecting the object to be detected; and a signal or direct current that is not synchronized with the pulse signal from the light projecting circuit to the light emitting element in accordance with the detection signal. An optical fiber type photoelectric switch characterized in that it is provided with means for superimposing.