JPH01280920A - Photoelectric switch - Google Patents

Abstract

PURPOSE:To prevent malfunction due to incidence of a disturbance light by making a light projected from the 2nd light emitting element incident on the 1st photodetector and making a light projected from the 1st light emitting element incident on the 2nd photodetector conversely if a passing object exists respectively. CONSTITUTION:If no passing object 11 exists, the light projected from a 1st light emitting element 12 is made incident on a 1st light receiving element 14 and a light projected from the 2nd light emitting element is made incident on the 2nd light receiving element 13 respectively. When the passing object 11 exists, the light projected from the 1st light emitting element 15 is made incident on the 1st light receiving element 14 and a light projected from the 2nd light emitting element 12 is made incident on the 2nd light receiving element 13 respectively conversely. That is, the light projected from any of the light emitting elements 12, 15 is always made incident on both the light receiving element 13, 14 and the light is discriminated depending on the difference from the frequency. Thus, malfunction due to the incident of a disturbance light or the like is prevented to attain sure operation.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a photoelectric switch in which a light emitting element and a light receiving element are arranged facing each other and detect the presence or absence of an object passing between them.

<Prior Art> A conventional photoelectric switch, as shown in FIG. 8, for example, is composed of a pair of light emitting element 1 and light receiving element 2 that are arranged opposite each other, and when an object 3 passes between them, the optical path is interrupted. The passing object 3 is detected by utilizing the fact that no light is incident on the light receiving element 2.

Further, as shown in FIG. 9, there is also one in which a plurality of sets of light-emitting elements and light-receiving elements are provided, and a light-emitting element group 4 is arranged on one side of the passing object 3, and a light-receiving element group 5 is arranged on the other side.

Problems to be Solved by the Invention In the above-mentioned prior art, ambient light may enter the light receiving element into the light pool from the light emitting element.

In this case, even if the passing object passes and the light from the light emitting element is blocked, disturbance light is incident on the light receiving element, and there is a problem that the passage of the passing object cannot be detected.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a photoelectric switch that can prevent malfunctions caused by the incidence of ambient light and that can operate reliably.

<Means for Solving the Problems> The means for solving the problems according to the present invention is as shown in FIGS. In a photoelectric switch for detecting a passing object 11, a first light emitting element 12 and a second light receiving element 13 are arranged on one side of the passing object 11, and a first light receiving element 14 and a second light emitting element 15 are arranged on the other side of the passing object 11. are arranged, and the first and second light emitting elements 12.15 and the first and second light receiving elements 13, 14 are arranged such that when there is no passing object 11, the light projected from the first light emitting element 12 is The light projected from the second light emitting element 15 to the light receiving element 14 enters the second light receiving element 13, and when there is a passing object 11,
The light projected from the first light emitting element 12 is transmitted to the second light receiving element 13.
Furthermore, the lights projected from the second light emitting elements 15 are arranged so as to be incident on the first light receiving elements 14, respectively.

<Operation> In the problem solving means described above, when there is no passing object 11, the light projected from the first light emitting element 12 is transmitted to the first light receiving element 14, and the light projected from the second light emitting element 15 is transmitted to the second light receiving element 13.
The light projected from the two is incident on each of them. In addition, the passing object 11
, conversely, the light projected from the second light emitting element 15 enters the first light receiving element 14, and the light projected from the first light emitting element 12 enters the second light receiving element 13.

That is, the light projected from either light emitting element 12.15 is always incident on both light receiving elements 13.14,
Since these lights are discriminated based on differences in frequency, etc., it is possible to prevent malfunctions due to the incidence of disturbance light, etc., and ensure reliable operation.

<Example> Hereinafter, a first example of the present invention will be described based on FIGS. 1 to 4. FIG. 1 is a layout diagram of a light emitting element and a light receiving element showing a photoelectric switch in a first embodiment of the present invention, FIG. 2 is a block diagram of a control circuit, and FIG. 3 is an electric circuit diagram of a pulse period detection circuit. FIG. 4 is an electric circuit diagram of the signal processing circuit, and FIG. 5 is a timing chart of pulse signals generated by the timing generation circuit.

As shown in the figure, the photoelectric switch of the present invention is a photoelectric switch in which a light emitting element and a light receiving element are arranged facing each other, and detects the presence or absence of an object passing between them. A light emitting element 12 and a second light receiving element 13 are arranged, and a first light receiving element 14 and a second light emitting element 15 are arranged on the other side with respect to the passing object 11. When there is no passing object 11, the first and second light receiving elements 13 and 14 transmit the light projected from the first light emitting element 12 to the first light receiving element 14, and the light projected from the second light emitting element 15 to the first light receiving element 14. When the light is incident on the two light receiving elements 13 and there is a passing object 11, the light projected from the first light emitting element 12 is incident on the second light receiving element 13, and the light projected from the second light emitting element 15 is on the first light receiving element. 14, respectively.

The light emitting elements 12.15 are constituted by general light emitting diodes and the like, and the light receiving elements 13.14 are constituted by general phototransistors and the like.

As shown in FIG. 1, the first light emitting element 12, the first light receiving element 14, the second light emitting element 15, and the second light emitting element 12, A light-receiving element 13 is arranged, and the first light-emitting element 12 and the first light-receiving element 14 are arranged to face each other with the passing object 11 in between on a straight line passing through the center of the passing object 11 . Further, the second light emitting element 15 and the second light receiving element 13 intersect at an acute angle (a right angle or an obtuse angle) with a straight line passing through the center of the passing object 11 and connecting the first light emitting element 12 and the first light receiving element 14. They are arranged facing each other on a straight line with the passing object 11 in between.

As shown in FIG. 2, a control circuit 1 drives these light emitting elements 12 and 15 and detects the outputs of the light receiving elements 13 and 14.
6 is two different frequencies that are not integral multiples of each other [
Timing generation circuit 1 that generates pulse signals of 1 and f2
7 and the frequency r1 generated by the timing generation circuit 17.
a first light emitting element driving circuit 18 that drives the first light emitting element 12 in synchronization with a pulse signal of; and a first light emitting element driving circuit 18 that drives the second light emitting element 15 in synchronization with a pulse signal of frequency f2 generated by the timing generation circuit 17. Second light emitting element drive circuit 1
9, a first current-voltage conversion circuit 20 that converts the output current of the first light receiving element 14 into voltage, and the second light receiving element 13.
a second current-voltage conversion circuit 21 that converts the output current of
, a first amplification circuit 22 that amplifies the output voltage of the first current-voltage conversion circuit 20, and a second current-voltage conversion circuit 21.
a second amplification circuit 23 that amplifies the output voltage of the first amplification circuit 22; a first pulse period detection circuit 24 that detects the frequency of the output signal of the first amplification circuit 22; It consists of a second pulse period detection circuit 25, and a signal processing circuit 26 and an output circuit 27 that output a detection signal based on the detection results of the first pulse period detection circuit 24 and the second pulse period detection circuit 25. and,
The pulse signal generated by the timing generation circuit 17 is
For example, as shown in Fig. 5, the pulse signal of frequency r1 is 'H
” level time is 6 microseconds, “L” level time is 0
．． The pulse signal of frequency r2 is a signal of 1 milliseconds, and the time of 'H' level is the same +, and the time of 'L' level is about 3
It is considered to be a signal of 2 times.

As shown in FIG. 3, the first pulse period detection circuit 24 has an AND input terminal in which the output signal of the first amplification circuit 22 is input to the input terminal on the negative side, and a sampling signal r3 is input to the input terminal on the positive side. The data input terminal is connected to the output terminal of the sampling gate 28, and the data input terminal is connected to the output terminal of the sampling gate 28. 1 minute (3 microseconds)
A first synchronization detection circuit 29 is composed of 70 D-7 rip circuits to which pulse signals of the same waveform delayed by a certain amount of time are input, and a data input terminal is connected to the output terminal of the sampling date 28, and a taro clock input terminal is connected to the timing detection circuit 29. "H" from the pulse signal of frequency 12 generated by the generation circuit 17
A second synchronization detection circuit 30 constituted by a D-7 lip 70 to which a pulse signal of the same waveform delayed by one-half (3 microseconds) of the level time is input, and a data input terminal connected to the first synchronization At least three stages of first registers 31 connected to the two output terminals of the detection circuit and having a clock input terminal inputted with a pulse signal of frequency 11 generated by the timing generation circuit 17, and a data input terminal connected to the second synchronization The frequency f generated by the timing generation circuit 17 is connected to the output terminal of the detection circuit 30 and is connected to the clock input terminal.
At least three stages of Ni 7 to which the pulse or signal of No. 2 is input.
a third frequency coincidence detection circuit 33 constituted by an AND gate that takes the AND gate of at least three of the output terminals of the first seventh register 31; and at least three of the output terminals of the second seventh register 32; and a second frequency-number construction circuit 34 configured by AND-DATE, which performs the logical product of books. Further, the second pulse period detection circuit 25 also has a similar configuration. As shown in FIG. 5, the sampling signal f3 is obtained by ORing the pulse signal of frequency r1 and the pulse signal of frequency r2.

As shown in FIG. The output signal B1 of the output circuit 34, the output signal A2 of the second frequency coincidence detection circuit (not shown) of the second pulse period detection circuit 25, and the second frequency-number configuration circuit (not shown) of the second pulse period detection circuit 25 an input date circuit 35 to which the output signal B2 (not shown) is input, and the input date circuit 3
and an RS latch circuit 36 connected to the output terminal of No. 5. The input date circuit 35 has a first input terminal connected to the output signal A1, and a second input terminal connected to the inverter 37.
a four-input terminal type first AND date 39 whose third input terminal is connected to the output signal A2 via the inverter 38, and whose fourth input terminal is connected to the output signal B2 through the inverter 38; The first input terminal receives the output signal A1 via the inverter 40, and the second input terminal receives the output signal B1 (this,
It consists of a four-input terminal type second AND date 42 whose third input terminal is connected to the output signal A2 and whose fourth input terminal is connected to the output signal B2 via an inverter 41. Also,
The set input terminal of the RS latch circuit 36 is connected to the output terminal of the first AND date 39, and the reset input terminal is connected to the output terminal of the second AND date 42, respectively.

In the above configuration, when there is no passing object 11, the light projected from the first light emitting element 12 travels straight and enters the first light receiving element 14, as shown by the solid line in FIG. The light projected from the light receiving element 15 travels straight and enters the second light receiving element 13.

Furthermore, when there is a passing object 11, the light projected from the first light emitting element 12 is reflected by the passing object 11 and enters the second light receiving element 13, as shown by the two-dot chain line in FIG.
The light projected from the second light emitting element 15 is reflected by the passing object 11 and enters the first light receiving element 14.

That is, when there is no passing object 11, the pulsed light of frequency f1 is transmitted to the first light receiving element 14, and the pulsed light of frequency f1 is transmitted to the second light receiving element 1.
Pulse light of frequency f2 is incident on each of the passing objects 11 and 3.
exists, pulsed light of frequency f2 enters the first light-receiving element 14, and pulsed light of frequency 11 enters the second light-receiving element 13.

Then, this light is exchanged into an electric signal by each light receiving element 13, 14, the output current is converted into voltage by current-voltage conversion circuits 20 and 21, and after amplification is performed by amplifier circuits 22 and 23, the pulse period is detected. Enter circuit 24.25.

The signal entering the pulse period detection circuit 24.25 is detected to be in synchronization with the pulse signals of frequencies fl and f2 by the internal synchronization detection circuit 29.30, and the signal is sent to the shift reno star 31.32.
When all of the past three detection results stored in the output signal 33 match the "H" level, the minus number output circuits 33 and 34 generate output signals.

That is, when the frequency of the input signal matches fl, the output terminal of the first frequency match detection circuit 33 goes to "H" level, and when it matches r2, the output terminal of the second frequency match detection circuit 34 goes to "H" level. When the output terminals are at the "H" level, and they do not coincide with each other (such as when disturbance light is incident), the output terminals of the two-number output circuits 33 and 34 are both at the "L" level.

Then, in the signal processing circuit 26, the pulse period detection circuit 24.25 outputs a normal output signal (if there is no passing object 11, A1=H, B1=L, A2=L, B2=H
So, if there is a passing object 11, A1=L, B1
=H%A2=H, B2=L), the output of the RS latch circuit 36 is switched, and the output circuit 27 is switched.
send the output signal to.

In addition, if an abnormal output signal is obtained from the pulse period detection circuit 24 or 25 (if the same pulse signal is incident on the first light receiving element 14 and the second light receiving element 13, or when the same pulse signal is incident on the first light receiving element 14 or the second light receiving element 13, Since the output of the RS latch circuit 36 is not switched when ambient light is always incident on the light receiving element 13, stable operation can be obtained without being affected by the ambient light.

Next, a second embodiment of the present invention will be described.

In this embodiment, the light emitting element 12.15 and the light receiving element 13
．． 14 is different from the first embodiment.

That is, as shown in FIG. 6, the first light emitting element 12 and the first light receiving element 14 are arranged facing each other on a straight line perpendicular to the traveling direction of the passing object 11, and the second light emitting element 15 is arranged opposite to the first light receiving element 14. The second light receiving element 13 is arranged adjacent to the first light emitting element 12, and their optical paths do not intersect.

When there is no passing object 11, the light projected from the first light emitting element 12 travels straight and enters the first light receiving element 14, as shown by the solid line in FIG.
The projected light travels straight and enters the second light receiving element 13.

Furthermore, when there is a passing object 11, the light projected from the first light emitting element 12 is diffusely reflected by the passing object 11 and enters the second light receiving element 13, as shown by the two-dot chain line in FIG. ,
The light projected from the second light emitting element 15 is diffusely reflected by the passing object 11 and enters the first light receiving element 14 .

At this time, if the passing object 11 specularly reflects light like a mirror, the light emitting element 12.15 and the light receiving element 13.1
It is preferable to use one with slightly wide-angle directional characteristics as No. 4.

Next, a third embodiment of the present invention will be described.

According to this embodiment, the first light emitting element 12 and the second light emitting element 1
5 alternately emit light, which simplifies the configuration of the control circuit 16 and makes it possible to detect the occurrence of an abnormal $ state.

In this embodiment, the light emitting elements 12.15 and the light receiving elements 13.14 may be arranged in either the first embodiment or the second embodiment, or in another arrangement.

As shown in FIG. 7, the control circuit 16 includes a timing generation circuit 17 that generates a pulse signal of a frequency 14 with a duty ratio of 50%, and a timing generation circuit 17 that drives the first light emitting element 12 in synchronization with the pulse signal. One light emitting element drive circuit 1
8, a second light emitting element drive circuit 19 that drives the second light emitting element 15 in synchronization with a signal obtained by inverting the pulse signal by an inverter (inversion circuit) 43, and a first current-voltage conversion circuit similar to the first embodiment. circuit 20, second current-voltage conversion circuit 21,
The first amplifier circuit 22 and the second amplifier circuit 23 have a negative input terminal connected to the output terminal of the first amplifier circuit 22, and a pulse signal of frequency f4 generated by the timing generation circuit 17 at the other input terminal. The first exclude to be entered is
The input terminal on the negative side of the positive or date 44 (EX-OR date) is connected to the output terminal of the second amplifier circuit 23, and the pulse signal of frequency "4" generated by the timing generation circuit 17 is input to the input terminal on the other side. a second EX-OR date 45 which is connected to the output terminal of the -EX-OR date 44; a second integration circuit 47 with a relatively small time constant connected to the output terminal;
and an RS latch circuit 48 whose reset input terminal is connected to the first integrating circuit 46 and whose set input terminal is connected to the second integrating circuit 47, and whose negative input terminal is connected to the -EX
- a third EX-OR date 49 whose input terminal on the other side is connected to the output terminal of the OR date 44 and the output terminal of the second EX-OR date 45; and the third EX-OR date 49;
and a third integrating circuit 50 connected to the output terminal of 9. The first integrating circuit 46 includes a resistor 51 and a capacitor 52, and the second integrating circuit 47 similarly includes a resistor 53 and a capacitor 54. Further, the third integrating circuit 50 includes a diode 55, resistors S6, 57, a capacitor 58, and a buffer date 59, and the output terminal of the buffer date 59 serves as an abnormality notification output terminal.

If the passing object 11 does not exist, the -EX
- Since the plane input terminals of OR date 44 always match, its output terminal continuously outputs "L" level, and the second EX
- Since the surface input terminals of OR date 45 do not always match,
The output terminal continuously outputs the "H" level.

In addition, if there is a passing object 11, conversely, the -th
The output terminal of the EX-OR date 44 continuously outputs the "H" level, and the output terminal of the second EX-OR date 45 continuously outputs the "L" level.

In Uni, the first integrating circuit 46 is the -EX-OR date 4
Due to the slight difference in transmission time of the signals applied to the surface input terminals No. 4, extremely thin pulse signals generated from the output terminals are removed. The second integrating circuit 47 also has a similar function.

The output of the RS latch circuit 48 is switched by this output signal, and an operating signal can be obtained.

During the normal operation, the -EX-OR gate 44
Since the output terminal of the third EX-OR gate 49 and the output terminal of the second EX-OR gate 45 are always opposite to each other, the output terminal of the third EX-OR gate 49 continuously maintains the "L" level.

However, if some abnormal operation occurs, the third EX-O
If the output terminal of the R gate 49 remains at "H" level continuously (such as when the same light is incident on both light receiving elements 13 and 14), a pulse signal with a frequency of "4" is output (when only one light receiving element (e.g. when continuous light is incident).This signal is used as an abnormality notification signal and can notify the user of the abnormality.

Note that the control circuit 16 of this embodiment does not output an abnormality notification signal when light continues to enter one of the light receiving elements and no light enters the other light receiving element; however, in this case, the RS An abnormal operation can be detected because the output of the latch circuit 48 switches abnormally quickly (same frequency as frequency f4).

As described above, according to this embodiment, the configuration of the control circuit 16 is simplified, and the occurrence of an abnormal situation can be detected.

It should be noted that the present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

For example, two or more sets of light-emitting elements and light-receiving elements may be provided, and it can be determined which light-emitting element the light projected from has entered the light-receiving element by a method such as making each light-emitting element emit light in a different color. You may.

<Effects of the Invention> As is clear from the above description, according to the present invention, the first light emitting element and the second light receiving element are arranged on one side with respect to the passing object, and the first light receiving element is arranged on the other side with respect to the passing object. and a second light emitting element are disposed, and the first and second light emitting elements and the first and second light receiving elements are arranged so that when there is no passing object, the first light receiving element receives the light projected from the first light emitting element. However, the light projected from the second light emitting element enters the second light receiving element, respectively,
Conversely, when there is a passing object, the arrangement is such that the light projected from the second light emitting element enters the first light receiving element, and the light projected from the first light emitting element enters the second light receiving element. The light emitted from either light emitting element always enters both light receiving elements, and these lights are discriminated based on differences in frequency, etc., which prevents malfunctions due to the incidence of external light and ensures reliable operation. It has excellent effects such as:

[Brief explanation of the drawing]

FIG. 1 is a layout diagram of a light emitting element and a light receiving element showing a photoelectric switch in a first embodiment of the present invention, FIG. 2 is a block diagram of a control circuit, and FIG. 3 is an electric circuit diagram of a pulse period detection circuit. FIG. 4 is an electrical circuit diagram of the signal processing circuit, FIG. 5 is a timing chart of pulse signals generated by the timing generation circuit, and FIG. 6 is a light emitting element and light receiving device showing a photoelectric switch in a second embodiment of the present invention. FIG. 7 is a block diagram of a control circuit in a third embodiment of the present invention, and FIGS. 8 and 9 are layout diagrams of a light emitting element and a light receiving element showing a conventional photoelectric switch. 11: Passing object, 12: First light emitting element, 13: Second light receiving element, 14: First light receiving element, 15: Second light emitting element, 16
2. Control circuit, 17: Timing generation circuit, 18.19:
Light emitting element drive circuit, 20.21: Current voltage conversion circuit, 2
2, 23: amplifier circuit, 24, 25: pulse period detection circuit, 26: signal processing circuit, 27: output circuit. Applicant Sharp Corporation

Claims (1)

[Claims] In a photoelectric switch in which a light emitting element and a light receiving element are arranged facing each other and detecting the presence or absence of an object passing between them, the first light emitting element and the second light receiving element are arranged on one side with respect to the passing object, and the first light emitting element and the second light receiving element are arranged on one side with respect to the passing object. A first light-receiving element and a second light-emitting element are arranged on the other side with respect to the object, and the first and second light-emitting elements and the first and second light-receiving elements are arranged so that when there is no passing object, the first light-receiving element and the second light-emitting element The projected light is directed to the first light receiving element,
The light projected from the second light emitting element enters the second light receiving element, and when there is a passing object, the light projected from the first light emitting element enters the second light receiving element. A photoelectric switch characterized in that the light is arranged so that the light is incident on each of the first light receiving elements.