JPS62253218A - Transmission type photoelectric switch - Google Patents

Abstract

PURPOSE:To eliminate the need for a synchronizing line and to attain high reliability by making the projecting direction of pulse lights for synchronization and detection opposite to each other and providing a phase difference between both the pulses. CONSTITUTION:A reference signal S from a reference signal generating circuit 23 is outputted to a synchronizing detection circuit 30 and fed also to a phase shift circuit 24 and a phase shift signal C retarded by a period Tp1 is obtained via a waveform shaping circuit 25. In lighting a light emitting element 27 in the generating timing of the signal C, the synchronizing pulse light I is made incident in a photodetector 32, an output with the same timing as the signal C is generated, the output is delayed in phase by a period Tp2 via the phase shift circuit 34 and a waveform shaping circuit 35 to form a phase shift demodulation signal R whose generating timing and the period retarded by one period to the signal S are ocincident. In light-emitting the light emitting element 37 in the generating timing of the signal R, a detection pulse D is made incident in the photodetector 28. When the pulse light I or D is shut, since the output of the element 28 is lost, the obstacle in the optical path is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wireless transmissive photoelectric switch that uses optical signals to increase synchronization between a light emitter and a light receiver.

For example, the standing limb blood-transmitting photoelectric switch has a light emitter (1) and a light receiver (2) facing each other with a detection space in between, as shown in Fig. 4. The presence or absence of a person or object is detected based on whether or not the directed light a is blocked.

In order to improve the detection accuracy of such a transmission type photoelectric switch, it is necessary to prevent malfunctions caused by ambient light or interference between adjacent photoelectric switches. As a means to prevent this, a photoelectric switch (
In 3), the light emitter (1) emits pulsed light, and the light receiver (2) performs synchronous detection to extract only the light incident at the timing of this light emission. This synchronous detection is
The reference signal output from the reference signal generation circuit (4) provided in the light projector is generated by synchronizing the operations of the light projector and the light receiver.

That is, in the projector (1), the light emitting element (6) is activated by the drive circuit (5) at the timing when the reference signal S is generated.
Make the pulse emit light. On the other hand, in the light receiver (2), after the output of the light receiving element (7) is amplified by the amplifier (8), only the output that matches the generation timing of the reference signal S is extracted by the synchronous detection circuit (9), and When a certain condition is satisfied, for example, when this detection continues a predetermined number of times, a control output C is generated from the output circuit (10).

Therefore, in the conventional transmission type photoelectric switch (3), in order to synchronize the emitter (1) and the receiver (2), it is necessary to connect them with an electric wire (11) for transmitting a reference signal. Ta.

The conventional transmission type photoelectric switch (3) shown above connects the electric wire (11) for transmitting the reference signal to the emitter (1) and the receiver (
2), which caused the following problems.

■This wiring makes installing the photoelectric switch complicated.

■If the wires cannot be housed within surrounding structures such as door supports or ceilings, the wires will become an obstruction to traffic, and furthermore, they will be exposed to the outside, which is not aesthetically pleasing.

(2) If the mounting positions of the projector and receiver move relative to each other, such as in a track vehicle, the electric wires will restrict movement, making practical use extremely difficult.

In view of the above-mentioned conventional problems, the present invention has been developed to improve and eliminate them.The means for solving the problems is to synchronize the emitter and receiver by transmitting and receiving pulsed light for synchronization. It is a transmission type photoelectric switch that detects the presence of an object between the emitter and receiver by transmitting and receiving pulsed light for detection with a phase different from that of the pulsed light for synchronization. The device includes a reference signal ordering circuit, a phase shift circuit that shifts the phase of this reference signal, and this phase shift signal [or the above reference signal].
A light emitting element for synchronization that emits pulsed light for synchronization at the timing of occurrence of pulsed light for synchronization, a light receiving element for detection, and an output of this light receiving element for detection at the timing of occurrence of the above reference signal [or the above phase shift signal]. The projector includes a synchronization detection circuit for detecting the synchronization, and the projector includes a synchronization light-receiving element facing the synchronization light-emitting element, and a synchronization light-receiving element that phase-shifts the output of the light-receiving element to generate the reference signal [or the phase-shifted signal]. A transmissive photoelectric switch comprising a phase shift circuit that generates signals with matching timing, and a light emitting element for detection that emits pulsed light for detection toward the light receiving element for detection at the timing of generation of this signal. It is.

In the above means, synchronizing pulsed light is transmitted from the light receiver to the projector by the synchronizing light emitting element and the light receiving element. The transmission and reception of the detection pulse light between the detection light emitting element and the light receiving element, which are synchronized by this, is carried out with a certain phase shift difference from the synchronization light pulse by the transfer circuit provided in the light receiver and the emitter, respectively. The synchronous detection circuit detects the presence of an object even if either the synchronization pulse light or the detection pulse light is interrupted.

1 difference ± The present invention will be explained below according to examples.

The light emitter (2) of the transmission type photoelectric switch (20) shown in Figure 1
1), a light receiver (21), and a light receiver (22) are arranged to face each other with a detection space in between.

In this photoreceiver (22), (23) is a reference signal generation circuit which generates a reference signal S of a predetermined frequency (period T) having a waveform as shown in FIG. 2(A), for example. (24) is a phase shift circuit, (25) is a waveform shaping circuit, and by passing through these, the reference signal S becomes a phase shift signal C [see FIG. 2 (b)] delayed by a period Tpt. (26) is a drive circuit, (27) is a light emitting element for synchronization such as an LED, and the drive circuit (26) emits pulsed light for synchronization toward the projector (21) at the generation timing of the phase shift signal C. Emits light.
(28) is a light receiving element for detection, and a photodiode or the like is used. (29) is an amplifier circuit, and the light receiving element (28
) amplify the output.

(30) is a synchronous detection circuit which extracts only the output of the amplifier circuit (29) that coincides with the generation timing of the reference signal S generated by the reference signal generation circuit (23), and this detects only the output that matches the generation timing of the reference signal S generated by the reference signal generation circuit (23). The detection operation is performed by n consecutive shots.

(31) is based on the detection signal of the synchronous detection circuit (30),
This is an output circuit that generates an external control output of 0.

- In the power projector (21), (32) is a light receiving element for synchronization, (33) is an amplifier circuit, and (34) is a TP2 [However,
A phase shift circuit that delays the phase by T-Ppt+Tp2), (35
) is the waveform shaping circuit, (36) is the drive circuit, (37) is the L
This is a light projecting element for detecting ED, etc. Here, a photodiode or the like is used as the synchronization light receiving element (32), and is arranged opposite to the synchronization light projecting element (27).

In the above configuration, the reference signal S generated by the °C1 reference signal generation circuit (23) is output to the synchronous detection circuit (30), is also sent to the phase shift circuit (24), and is sent to the waveform shaping circuit (25). The waveform is shaped into a phase-shifted signal C delayed by a period TP as shown in FIG. 2(b).

When the synchronizing light emitting element (27) is caused to emit light by the drive circuit (26) at the timing of generation of this phase shift signal C, if there is no obstacle between the light emitter (21) and the light receiver (22),
This synchronizing pulse light enters the synchronizing light receiving element (32), and the synchronizing light receiving element (32) outputs an output at the same timing as this phase shift signal C [see Fig. 2 (b)]. This output is generated by a phase shift circuit (34) and a waveform shaping circuit (
35), the phase is delayed by TP2, and the period and generation timing completely match with respect to the reference signal S by only -period delay? 5jt7A signal R [see FIG. 2 (c)]. At the timing of generation of this phase-shifted demodulation signal R, the drive circuit (36) drives the light emitting element (37) for detection.
If there is no obstacle between the emitter (21) and the receiver (22), this pulsed light D(?lR) for detection will emit light.
2 (d)] enters the detection light receiving element (28).

After the output of the light receiving element (28) is amplified by the amplifier circuit (29), the output is synchronously detected at the generation timing of the reference signal S in the synchronous detection circuit (30). It is possible to detect that there is no object or the like between the light projector (21) and the light receiver (22) without being affected by external disturbance light or the like.

On the other hand, if a person, object, etc. is located between the emitter (21) and the receiver (22) and either the synchronization pulsed light or the detection pulsed light is blocked, the detection light receiving element (
Since the output of 28) disappears, an object detection operation is performed, and a control output is output from the output circuit (31).

In the above embodiment shown in FIG. 1, while the reference signal S is directly input to the synchronous detection circuit (30) in the photoreceiver (22), this reference signal S is passed through the phase shift circuit (24).
Since the output of the detection light receiving element (28) is transmitted through a loop passing through the emitter (21), the output of this detection light receiving element (28) is delayed by the delay in the phase shift circuit (24). This is accompanied by a delay of Tpl''Tp2, which is the sum of the phase TP1 and the delayed phase TP2 in the phase shift circuit (34).In this case, the period T of the reference signal S generated by the reference signal generation circuit (23) is always constant, and T”TP1+
There is no problem if the conditions of TP2 are maintained.

However, in reality, there are instrumental differences in mass-produced charging switches, and the period T of the reference signal S varies, resulting in T # TP
, + There is a possibility that synchronization with TP2 cannot be achieved.

In order to avoid this problem, the following measures can be taken.

The first avoidance means is to input the phase-shifted signal C generated by the waveform shaping circuit (25) receiving the output of the phase-shifting circuit (24) into the synchronous detection circuit (30), and send the reference signal S to the drive circuit (26). The configuration is such that you can input the information directly. However, it is assumed to be TPI-TP2. In this case, both the gate opening timing of the synchronous detection circuit (30) and the output timing of the detection light receiving element (28) are always set within a predetermined time TPI""TP with respect to the reference signal S.
Late by 2. Therefore, it is not affected by variations in the period T. The reason why the emitter (21) and the receiver (22) are provided with phase shift circuits (24) and (34), respectively, is to send and receive the pulsed light for synchronization with a phase shift from that of the pulsed light for detection. The pulsed light I for synchronization is the reference signal S
The timing may be made to match either of the phase shift signal C and the phase shift signal C described above.

A second avoidance means is that in the embodiment shown in FIG. 1, the phase shift operation in the phase shift circuit (24) is a phase advancing operation of tl,
The phase shift operation in the phase shift circuit (34) is a phase delay operation of tl. In this way, as a result of the phase advance and phase delay canceling each other out, the gate opening timing of the synchronous detection circuit (30) and the output timing of the detection light receiving element (28) are always the same as each pulse of the reference signal S. It completely matches the onset timing and is not influenced by variations in the period T. Incidentally, the advance and yn% operation in the phase shift circuit (24) is performed based on the period T of the reference signal S determined from a few co-cycles.

In addition, in the above embodiment shown in Fig. 1, the pulsed light for detection and the pulsed light for synchronization (2) were sent and received through separate optical paths, but as shown in Fig. 3, the pulsed light for detection and the pulsed light for synchronization Each half mirror (38) (39) is placed 4 times relative to the optical path.
By arranging them at an angle of 5°, the optical paths can be made coaxial. Here, the light emitting element and the light receiving element are the first
Components that are the same as those in the figures are given the same reference numerals and their explanations will be omitted. If the optical paths are both jM in this way, there is an advantage that the photoelectric switch (40) can be manufactured in a small size even if there are two pairs of light emitting element and light receiving element.

According to the present invention, it is possible to synchronize the light receiver and light receiver of a pass-through photoelectric switch in a completely wireless manner.
Since there is no need to route synchronization cables, the emitter and receiver can be completely independent. Therefore, the workability of mounting is greatly improved, and the degree of freedom in installation is greatly increased compared to conventional ones, and the range of use thereof can be expanded.

Furthermore, since the synchronization pulsed light I and the detection pulsed light are projected in opposite directions, there is no danger of misunderstanding whether they are one or the other. In particular, a phase difference is given between these pulsed lights Even if it is incident on
This has the effect of preventing malfunctions and can provide high reliability.

Furthermore, as shown in Fig. 1, in the case where the pulsed light I for synchronization and the pulsed light for detection are transmitted through separate optical paths, the detection operation is performed even if either one is interrupted.
One transmissive photoelectric switch essentially has two light detection lines. Therefore, when multiple charging switches are arranged to surround the mold position and many light detection lines are set in parallel, as in the case of safety devices for press machines, the number of photoelectric switches installed can be reduced by approximately half. There is an effect.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a transmission type photoelectric switch which is an embodiment of the present invention, Fig. 2 is a signal waveform diagram of the main part of the circuit shown in Fig. 1, and Fig. 3 is a diagram of the emitter and receiver in the present invention. FIG. 4 is a diagram illustrating a case where the optical paths of pulsed light for detection and synchronization are coaxial. FIG. 4 is a diagram illustrating a conventional transmission type photoelectric switch in which a synchronizing signal is transmitted and received by an electric wire wired between a light projector and a light receiver. (20) (40)-One transmission type photoelectric switch, C21
)・− Emitter, (22) −・− Receiver, (23) ~
Reference signal generation circuit, (24)--transfer circuit, (27)--light emitting element for synchronization, (28)--light receiving element for detection, (30)--synchronous detection circuit, (32) - Light receiving element for one synchronization, (34) - One phase shift circuit, (37) - Light emitting element for detection, S - Reference signal, C - Phase shift signal, 1 - Pulse light for one synchronization, R - ...Demodulated phase-shifted signal, pulsed light for D-1 detection. Patent applicant Hokuyo Electric Co., Ltd. Agent Gangwon Province
7?1 Figure 3 4ha Figure 4

Claims (1)

[Claims] (1) Synchronize the emitter and receiver by transmitting and receiving pulsed light for synchronization, and transmitting and receiving pulsed light for detection with a phase different from the synchronizing pulsed light, and connect the emitter and receiver to each other. This is a transmission type photoelectric switch that detects the presence of an object, etc. between ]
A light emitting element for synchronization that emits pulsed light for synchronization at the timing of occurrence of pulsed light for synchronization, a light receiving element for detection, and an output of this light receiving element for detection at the timing of occurrence of the above reference signal [or the above phase shift signal]. The projector includes a synchronization detection circuit for detecting the synchronization, and the projector includes a synchronization light-receiving element facing the synchronization light-emitting element, and a synchronization light-receiving element that phase-shifts the output of the light-receiving element to generate the reference signal [or the phase-shifted signal]. The present invention is characterized by comprising a phase shift circuit that generates signals with matching timing, and a light emitting element for detection that emits pulsed light for detection toward the light receiving element for detection at the generation timing of this signal. Transmissive photoelectric switch.