JPH06283992A - Pulse modulation type photoelectric switch - Google Patents

Abstract

PURPOSE:To prevent the pulse modulation type photoelectric switch from malfunctioning owing to pulse light such as projection pulse light from, for example, another photoelectric switch which is arranged nearby. CONSTITUTION:This photoelectric switch is provided with an oscillation period control circuit 9 which inputs both the inverted signal (g) of the photodetection pulse signal (2nd photodetection pulse signal) from a flip-flop 7 and the projection pulse signal (a) from a pulse oscillation circuit 1, detects the photodetection phase of the photodetection pulse light for the projection pulse signal from the signals, and outputs a control signal (h) for varying the pulse period of the projection pulse signal (a) for the pulse oscillation circuit 1 according to the photodetection phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a light projecting circuit and a light receiving circuit. The light projected from the light projecting circuit is changed in its light quantity by a target object, and the light receiving circuit receives the light quantity change. Thus, the present invention relates to a photoelectric switch for detecting the target object, and more particularly to a pulse modulation type photoelectric switch in which light emitted from a light projecting circuit is pulse-modulated.

[0002]

2. Description of the Related Art A photoelectric switch is capable of detecting a target object in a non-contact manner and is widely used for industrial purposes as well. Recently, it is projected from a light projecting circuit in order to remove the influence of noise light such as illumination. A pulse modulation type is generally used in which light is pulse-modulated and a light receiving circuit detects light from a light projecting circuit in a light receiving circuit.

FIG. 3 is a circuit diagram showing a conventional example of such a pulse modulation type photoelectric switch. In FIG. 3, the pulse modulation type photoelectric switch includes a pulse oscillation circuit 1 and a light emitting element 2.
A light projecting circuit 2 which is provided with 1 and receives a pulse signal (hereinafter referred to as a light projecting pulse signal) a from the pulse oscillation circuit 1
And the light receiving element 31 and the amplifier 3 which is a signal processing circuit
2, a filter 33, a comparator 34, and a light receiving circuit 3 for outputting a pulse signal (hereinafter referred to as a first light receiving pulse signal) c, and the first light receiving pulse signal c is projected onto the clock terminal CK thereof. A flip-flop 7 that outputs a pulse signal (hereinafter referred to as a second light-receiving pulse signal) d from the output terminal Q of the pulse signal a input to the clear terminal CL thereof, and a second light-receiving from the flip-flop 7 The pulse signal d is input, and the detection circuit 8 which outputs the detection signal e is comprised. OUT is a signal output terminal.

The operation of this pulse modulation type photoelectric switch will be described with reference to the operation waveform diagram shown in FIG. In FIG. 4, the period T ₀ from the pulse oscillating circuit 1 as shown in FIG.
The light emission pulse signal a of
As a result, pulsed light is projected from the light emitting element 21 of the light projecting circuit 2. The projected pulsed light is reflected by, for example, a target object, received by the light receiving element 31 of the light receiving circuit 3, and converted into an electric signal. This electric signal is amplified by the amplifier 32 and its DC component is removed by the filter 33. P of the output b of the filter 33 in FIG. 4B shows this waveform. The waveform P is further shaped by the comparator 34 and output from the light receiving circuit 3 as the first light receiving pulse signal c shown in FIG. The first light receiving pulse signal c and the light emitting pulse signal a are inputted to the clock terminal CK and the clear terminal CL of the flip-flop 7, respectively, so that the light receiving pulse signal c is emitted from the output terminal Q of the flip-flop 7. Signal a
The second light receiving pulse signal d is output when the output signal rises during the output period, ie, at time L ₀ (FIG. 4 (4)), and the second light receiving pulse signal d is input to the detection circuit 8.
The detection circuit 8 outputs the detection signal e of the target object indicated by D _p when the second light receiving pulse signal d is repeated a predetermined number of times, three times in FIG. 4 (5).

[0005]

The pulse-modulation type photoelectric switch described above operates without any problem with respect to noise light such as illumination, but when a plurality of these same photoelectric switches are arranged close to each other, Since the pulse periods of the projected pulsed lights of the photoelectric switches are the same or similar to each other, they may interfere with each other and malfunction. FIG. 5 is an operation waveform diagram in such a case. In FIG.
The left part of FIG. 5 shows the normal case as in FIG. 4 and the normal detection signal e indicated by D _p is output, but the right part of FIG. 5 is from another photoelectric switch having a similar cycle, for example. The case where the light receiving pulse light of is received is shown. The light-receiving pulsed light from another photoelectric switch outputs the output b indicated by E in FIG. 5B from the filter 33 of the light-receiving circuit 3, and the first light-receiving pulse signal c is output from the comparator 34 at time L _1. {FIG. 5 (3)}. The rising time L _{1 of} the first light receiving pulse signal c is the light emitting pulse signal a.
Within the output period of, the flip-flop 7 outputs the second light receiving pulse signal d as shown in FIG. 5 (4).
In this case, since the period of the light emitting pulse light of the other photoelectric switch is the same as or close to the light emitting pulse signal of this photoelectric switch, the second light receiving pulse signal d is subsequently output, and the second light receiving pulse signal d is output. If the light receiving pulse signal d of is continuous for a predetermined number of times, an erroneous detection signal indicated by D _e is output as shown in FIG. 5 (5).

An object of the present invention is to prevent malfunctions due to pulsed light such as projected pulsed light of other pulse modulation type photoelectric switches when a plurality of the same pulse modulation type photoelectric switches are arranged close to each other. It is to provide a pulse modulation type photoelectric switch.

[0007]

In order to achieve the above-mentioned object, the present invention provides a pulse oscillating circuit and a pulse signal from the pulse oscillating circuit (hereinafter referred to as a light emitting pulse signal) for projecting pulsed light. A light projecting circuit, a light receiving circuit for receiving pulsed light projected from the light projecting circuit and outputting a pulse signal (hereinafter referred to as a first light receiving pulse signal), the light projecting pulse signal and the first light receiving A pulse signal and a flip-flop that outputs a pulse signal (hereinafter referred to as a second light receiving pulse signal) when the first light receiving pulse signal is output during the output period of the light emitting pulse signal; A pulse modulation type photoelectric switch comprising a detection circuit which receives a second light receiving pulse signal and outputs a detection signal when a predetermined number of the second light receiving pulse signals are continuous, Detecting the received phase with respect to the scan light projecting optical pulse signal to be provided to the oscillation period control circuit for outputting a control signal for changing the pulse period of the projection pulse signal to the pulse oscillation circuit in response to the received phase.
And, for example, the above pulse oscillation circuit includes a capacitor,
A first inverter whose input terminal is connected to one terminal of the capacitor, and a control terminal between the output terminal of the first inverter and the other terminal of the capacitor have an output of the first inverter. Between the charging resistor connected via the first switch connected to the terminal and the output terminal of the first inverter and the other terminal of the capacitor, the control terminal is connected via the second inverter. Discharge resistor connected through a second switch connected to the output terminal of the first inverter, a third inverter whose output terminal is connected to one terminal of the capacitor, and the input of the third inverter The output terminal is connected to a terminal, and the input terminal is composed of a fourth inverter connected to the other terminal of the capacitor, and light is emitted from the output terminal of the first inverter. A pulse signal is output, and the oscillation cycle control circuit receives a light projecting pulse signal from the pulse oscillating circuit and an inverted signal of the second light receiving pulse signal from the flip flop, and an output terminal of the flip flop. A first current limiting resistor and a capacitor connected to the control terminal of the light emitting pulse signal via a first switch; a connection point between the capacitor and the first current limiting resistor; and the pulse oscillation. A light projecting pulse signal is connected to a capacitor of the circuit at its control terminal and is connected to a second current limiting resistor connected via a second switch through an inverter. Also, the first and second switches of these pulse oscillator circuits and the first switch of the oscillation cycle control circuit
The second switch and the second switch are each composed of a contactless analog switch.

[0008]

In the pulse modulation type photoelectric switch of the present invention, the light receiving phase of the received light pulse with respect to the light emitting pulse signal is detected, and the pulse oscillation circuit changes the pulse period of the light emitting pulse signal in accordance with the light receiving phase. An oscillation cycle control circuit that outputs a signal is provided. As a result, when the light-emission pulse light from another photoelectric switch is received, the pulse cycle of the light-emission pulse signal is changed each time in accordance with the light-receiving phase, so that the light-emission pulse signal is continuously received during the output period. The probability that the pulse signal rises is extremely small, and malfunctions due to pulsed light projected from other photoelectric switches are prevented. Then, for example, by inputting an inverted signal of the light receiving pulse signal (second light receiving pulse signal) from the flip-flop and the light emitting pulse signal from the pulse oscillating circuit to the flip flop of the oscillation cycle control circuit, the light receiving pulse light Detects the light receiving phase for the light emitting pulse signal of
The charge level of the capacitor of the same oscillation cycle control circuit was changed by this light reception phase, and the capacitor with the voltage between both terminals changed was connected to the capacitor of the pulse oscillation circuit, so the discharge speed of the capacitor of this pulse oscillation circuit changed. , The pulse cycle of the light emitting pulse signal changes. Further, since each of the switches is a contactless analog switch, reliability is improved.

[0009]

1 is a circuit diagram showing an embodiment of a pulse modulation type photoelectric switch of the present invention. The pulse-modulated photoelectric switch of the present invention shown in FIG. 1 is the same as the conventional pulse-modulated photoelectric switch shown in FIG. 3, except that the light-emission pulse signal a from the pulse oscillation circuit 1 and the second light-receiving pulse signal d from the flip-flop 7 are provided. And an oscillation period control circuit 9 for outputting a control signal h for changing the pulse period of the light emission pulse signal to the pulse oscillation circuit 1. It is a thing.

In FIG. 1, the pulse oscillation circuit 1 includes, for example, a capacitor 11 and one terminal R of this capacitor.
An inverter 17 whose input terminal is connected to (hereinafter simply referred to as terminal R), and an output terminal of the inverter 17 and the other terminal S of the capacitor 11 (hereinafter simply referred to as terminal S)
A charging resistor 1 whose control terminal is connected via a switch 14 connected to the output terminal of the inverter 17
2, a discharge resistor 13 whose control terminal is connected between the output terminal of the inverter 17 and the terminal S of the capacitor 11 via the switch 15 whose control terminal is connected to the output terminal of the inverter 17 via the inverter 16, and the capacitor 11 Terminal R
The output terminal of the inverter 17 is composed of an inverter 18 having its output terminal connected to the inverter 18, and an inverter 19 having its output terminal connected to the input terminal of the inverter 18 and having its input terminal connected to the terminal S of the capacitor 11. The light emitting pulse signal a is output from the. Further, the oscillation cycle control circuit 9 has a flip-flop 9 to which the light projection pulse signal a from the pulse oscillation circuit 1 and the second light reception pulse inversion signal g from the flip-flop 7 are input to its input terminals.
1, a capacitor 94 connected between the output terminal of the flip-flop 91 and the ground terminal via the switch 92 and the current limiting resistor 93 to which the light projection pulse signal a is input to the control terminal G, and the capacitor 94. And a current limiting resistor 96 connected to a control terminal G of the current limiting resistor 93 via a switch 95 to which a light projection pulse signal a is input via an inverter 97. The current limiting resistor 96 oscillates a pulse. It is connected to the terminal S of the capacitor 11 of the circuit 1.

The operation of this pulse modulation type photoelectric switch is as follows.
Is the street. First, the operation of the pulse oscillation circuit 1 is explained.
Reveal In FIG. 1, the inverter 1 of the pulse oscillation circuit 1
If the voltage of the input terminal of 9 is “H”, the inverter 18
The voltage of the output terminal of is to "H", and the output terminal of the inverter 17
The voltage of the child becomes "L", and the light emission pulse signal a becomes "L".
Become. Also, the voltage of "L" at the output terminal of the inverter 17
Is input to the control terminal G of the switch 15, so the switch
14 turns off. Furthermore, this "L" voltage is the inverter
Is input to the control terminal G of the switch 15 via 16
Then the switch 15 is turned on. At this time, capacitor 1
Since the voltage of the terminal S of 1 is "H" (inverter 19
Since the voltage of the input terminal of is "H"),
Inverter 1 from terminal S of terminal 11 through discharge resistor 13
This capacitor 11 is connected to the output terminal of the voltage of "L" of 7.
Quantity C₁₁And the resistance value R of the discharge resistor 13₁₃Time constant determined by and
(Hereinafter referred to as discharge time constant) R₁₃・ C₁₁To discharge. Ko
According to the discharge of the capacitor 11, the voltage of its terminal S, that is,
The voltage at the input terminal of the inverter 19 drops and this voltage
Reaches the threshold value of the inverter 19, the inverter 19
The voltage at the output terminal of switches from "L" to "H",
The voltage of the output terminal of the inverter 18 is “L”, the inverter 1
The voltage of the output terminal of 7 becomes "H". Of the inverter 17
When the voltage of the output terminal becomes “H”, the light emitting pulse signal a becomes
Switch to "H". At the same time, the switch 14 is turned off.
Then, the switch 15 is turned off. In addition, the inverter 1
The output terminal of 8 is connected to the terminal R of the capacitor 11.
Therefore, the voltage of the output terminal of the inverter 18 becomes "L".
As a result, the voltage at the terminal S of the capacitor 11 is changed accordingly.
Withdraw to. By this, the "H" of the inverter 17
Capacitor 1 from voltage output terminal through charging resistor 12
The capacitor S of this capacitor 11 is connected to the terminal S for the voltage of "L" of 1.
Quantity C₁₁And the resistance value R of the charging resistor 12₁₂Time constant determined by and
(Hereinafter referred to as charge time constant) R₁₂・ C₁₁Charge with. Ko
As the capacitor 11 is charged, the voltage at its terminal S, that is,
The voltage at the input terminal of the inverter 19 rises and this voltage
Reaches the threshold value of the inverter 19, the inverter 19
The voltage of the output terminal of switches from "H" to "L",
The voltage of the output terminal of the inverter 18 is “H”, the inverter 1
The voltage of the output terminal of 7 becomes "L", and the light emitting pulse signal a
Switches to "L". At the same time, switch 14 is turned off.
Then, the switch 15 is turned on. In addition, the inverter 1
The output terminal of 8 is connected to the terminal R of the capacitor 11.
Therefore, the voltage of the output terminal of the inverter 18 becomes “H”.
As a result, the voltage at the terminal S of the capacitor 11 is changed accordingly.
Rise to. As a result, “H” of the capacitor 11
Inverter 1 from S terminal of voltage
Discharge starts again at the output terminal of the "L" voltage of 7. this
The charge / discharge operation is repeated and the pulse oscillation continues. This
Here, the pulse cycle of the light-emission pulse signal a is set to these charging and
R of the sum of discharge time constants₁₂・ C₁₁+ R₁₃・ C ₁₁Determined by
Pulse width is the charging time constant R₁₂・ C₁₁Determined by.

Next, the operation of this pulse modulation type photoelectric switch including the oscillation cycle control circuit 9 will be described. The light projecting pulse signal a from the pulse oscillation circuit 1 is output to the light projecting circuit 2, and the pulsed light is projected from the light emitting element 21 of the light projecting circuit 2. The light projection pulse signal a is also input to the clear terminal CL of the flip-flop 7 and one input terminal of the flip-flop 91 of the oscillation cycle control circuit 9, and the flip-flop 91 can be set by the rising of the light projection pulse signal a. It will be in a state. The flip-flop 91 is set when the second received light pulse inversion signal g from the flip-flop 7 is input to the other input terminal, and is reset at the trailing edge of this signal at the end of the light-emission pulse signal a. It Further, since the light projection pulse signal a is directly input to the control terminal G of the switch 92 and to the control terminal G of the switch 95 via the inverter 97, the switch 92 is turned on during the output period of the light projection pulse signal a. Switch 9
5 is off. When the switch 92 is turned on, the flip-flop 91 is connected from the capacitor 94 through the current limiting resistor 93.
Of the capacitor 94 is discharged, and the voltage between both terminals of the capacitor 94 drops. Then, the light receiving circuit 3 receives the light and outputs the first light receiving pulse signal c, and if the first light receiving pulse signal c is within the output period of the light emitting pulse signal a, the second light receiving pulse inversion signal g is output. To be done. When the second light reception pulse inversion signal g is output, the flip-flop 91 is set, and the capacitor 94 is charged from this output terminal via the current limiting resistor 93, and this charging reaches the end of the light emission pulse signal a. It continues until the flip-flop 91 is reset. When the light emitting pulse signal a reaches the end, the switch 92 is turned off and the switch 95 is turned on, and the capacitor 94 is conducted to the capacitor 11 of the pulse oscillation circuit 1 through the current limiting resistor 96. The transfer of electric charges occurs in the capacitor 11 of the pulse oscillation circuit 1.
Affect the charging time of. That is, when the phase of the second light receiving pulse inversion signal g advances from the predetermined phase (the phase when the light from the light projecting circuit of itself is received), the set time of the flip-flop 91 becomes early and the capacitor 94 is charged. The time becomes longer and the voltage between both terminals becomes higher. Then, from the capacitor 94 to the capacitor 1 of the pulse oscillation circuit 1.
A current flows into the capacitor 1 to reduce the discharge speed of the capacitor 11, and the period of the light projection pulse signal becomes longer than the set period. On the contrary, when the phase of the second light reception pulse inversion signal g is delayed from the predetermined phase, the set time of the flip-flop 91 becomes late, the charging time of the capacitor 94 becomes short, and the voltage between both terminals thereof becomes low. Then, a current flows from the capacitor 11 of the pulse oscillation circuit 1 to the capacitor 94, the discharge speed of the capacitor 11 increases, and the period of the light projection pulse signal becomes shorter than the set period.

Here, whether the light receiving circuit 3 is the light projecting circuit 2 of itself.
When receiving the pulsed light from the
Of the light receiving pulse signal (second light receiving pulse signal)
Since the rising is within the output period of the light emitting pulse signal,
The operation is similar to the conventional one shown in FIG. That
The light receiving circuit 3 emits pulsed light from another photoelectric switch.
When the light is received,
Prevent malfunction. In FIG. 2, the light receiving circuit 3 is another photoelectric switch.
Of the operation when receiving the pulsed light emitted from the switch
It is a waveform diagram shown. In FIG. 2, the light projecting circuit 2 of its own is
A₁, A₂, A₃The light emission pulse signal a indicated by
{Fig. 2 (1)}, the light receiving circuit 3 emits light from another photoelectric switch.
Receiving pulsed light and E₁, E₂, E₃Filter 3 shown in
3 outputs b and C₁, C₂, C₃The first light receiving part shown in
It outputs the loose signal c (FIG. 2 (2) and FIG. 2).
(3)}. Here, the first received light pulse signal C₁The rise of
Time L ₁Is the light emission pulse signal A₁Out of the output period of
Therefore, the flip-flop 7 outputs the second light receiving pulse signal.
Since d is not output, this first received light pulse signal C₁Is
Not detected. At the same time, flip-flop 7 receives the second
Since the optical pulse inversion signal g is not output, the condenser 94
Is a light emitting pulse signal A when the switch 92 is turned on.₁of
During the output period, discharge occurs and the voltage between both terminals drops.
It Light emission pulse signal A ₁Switch reaches the end, switch 9
2 is turned off and switch 95 is turned on.
Capacitor 94 with low voltage between terminals conducts to capacitor 11.
Therefore, the projection pulse signal A₂Pulse period up to T₁
Will be shorter. As a result, the first received light pulse signal C
₂Rising time L₂Is the light emission pulse signal A₂Output period
The second light receiving pulse from the flip-flop 7 when entering
The signal d and its inverted signal g are output. This second
The flip-flop 91 is set by the light receiving pulse inversion signal g.
Light emission pulse signal A₂Turned on by
The capacitor 94 is charged through the switch 92 (Fig. 2
(5) and FIG. 2 (6)}. Light emission pulse signal A₂Ends
Switch 92 turns off and switch 95 turns on
Switch to a capacitor 94 with a high voltage between both terminals.
Is conducted to the capacitor 11, the light emitting pulse signal A
₃Pulse period up to T₂Becomes longer. This makes the first
Received light pulse signal C₃Rising time L₃Is flood pal
Signal A₃Is out of the output period of
The second light receiving pulse signal d and its inverted signal g are output.
Disappear. In this way, the projection from another photoelectric switch
When light pulsed light is received, the
Since the pulse period of the light emitting pulse signal a is changed each time,
During the output period of the light emitting pulse signal a as shown in FIG.
To another photoelectric switch, for example, three times in succession.
The second light receiving pulse signal d rises due to the light pulse light
The probability of a drop is extremely small, as shown in Fig. 2 (7).
Detection signal D due to malfunction_eIs prevented.

The switches 14, 15, 92,
Reference numeral 95 is, for example, a non-contact analog switch. This improves operational reliability.

[0015]

According to the pulse modulation type photoelectric switch of the present invention, malfunction of other photoelectric switches arranged close to each other due to the projected light pulse is prevented, so that the reliability of the operation is significantly improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a pulse modulation type photoelectric switch of the present invention.

FIG. 2 is an operation waveform diagram for explaining a malfunction prevention operation of the pulse modulation type photoelectric switch of the present invention shown in FIG.

FIG. 3 is a circuit diagram showing an example of a conventional pulse modulation photoelectric switch.

FIG. 4 is an operation waveform diagram of the conventional pulse modulation photoelectric switch shown in FIG.

5 is an operation waveform diagram when a malfunction occurs in the conventional pulse modulation type photoelectric switch shown in FIG.

[Explanation of symbols]

 1 Pulse Oscillation Circuit 11 Capacitor 12 Charging Resistance 13 Discharging Resistance 14 Switch, Non-contact Analog Switch (first) 15 Switch, Non-contact Analog Switch (second) 16 Inverter (second) 17 Inverter (first) 18 Inverter (third) 19 Inverter (fourth) 2 Light emitting circuit 3 Light receiving circuit 7 Flip-flop 8 Detection circuit 9 Oscillation cycle control circuit 91 Flip-flop 92 Switch, non-contact analog switch (first) 93 Current limiting Resistance (first) 94 Capacitor 95 Switch, solid state analog switch (second) 96 Current limiting resistance (second) 97 Inverter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naohiro Shimaji 2-12-1, Sonezaki, Kita-ku, Osaka City, Osaka Prefecture Hokuyo Electric Co., Ltd. (72) Inventor Kiyo Tanigawa 1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture No. 1 within Fuji Electric Co., Ltd.

Claims (3)

[Claims] 1. A pulse oscillating circuit, a light projecting circuit for projecting pulsed light by a pulse signal (hereinafter referred to as a light projecting pulse signal) from the pulse oscillating circuit, and pulsed light projected by the light projecting circuit. A light receiving circuit that receives a pulse signal (hereinafter referred to as a first light receiving pulse signal) and outputs the light projecting pulse signal and the first light receiving pulse signal,
A flip-flop that outputs a pulse signal (hereinafter referred to as a second light receiving pulse signal) when the first light receiving pulse signal is output during the output period of the light emitting pulse signal, and the second light receiving pulse signal In a pulse modulation type photoelectric switch consisting of a detection circuit which outputs a detection signal when a predetermined number of the second received light pulse signals are continuously input, a light receiving phase of the light receiving pulse light with respect to the light emitting pulse signal is detected. A pulse modulation type photoelectric switch is provided with an oscillation cycle control circuit for outputting a control signal for changing the pulse cycle of the light projection pulse signal to the pulse oscillation circuit according to the light receiving phase. 2. The pulse oscillating circuit according to claim 1, wherein a capacitor, a first inverter having an input terminal connected to one terminal of the capacitor, and the first inverter.
A charging resistor having a control terminal connected between the output terminal of the inverter and the other terminal of the capacitor through a first switch connected to the output terminal of the first inverter; and the first inverter. A discharge resistor whose control terminal is connected between a second switch connected to the output terminal of the first inverter via the second inverter, and the other output terminal of the capacitor, and the other terminal of the capacitor, A third inverter having an output terminal connected to one terminal of the capacitor, and a third inverter having an output terminal connected to an input terminal of the third inverter and an input terminal connected to the other terminal of the capacitor. 4 inverter, the light emitting pulse signal is output from the output terminal of the first inverter, and the oscillation cycle control circuit outputs the light emitting pulse signal from the pulse oscillating circuit. A flip-flop to which an inversion signal of the second light receiving pulse signal from the lip-flop is input, a first current limiting resistor at an output terminal of the flip-flop, and the light-projecting pulse signal at a control terminal thereof. The light emitting pulse signal is input to the control terminal between the capacitor connected via the first switch, the connection point of the capacitor and the first current limiting resistor, and the capacitor of the pulse oscillation circuit via the inverter. A pulse-modulated photoelectric switch comprising a second current limiting resistor connected via a second switch. 3. The one according to claim 2, wherein the first and second switches of the pulse oscillation circuit and the first and second switches of the oscillation cycle control circuit are each a contactless analog switch. Pulse modulation type photoelectric switch.