JP2557595B2 - Photoelectric sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric sensor which receives pulsed light output at a predetermined cycle and detects the presence or absence of an object based on the light receiving state.

[0002]

2. Description of the Related Art As photoelectric sensors of this type, for example,
There is a structure as shown in FIG. That is, this one is composed of a light projecting section 1 that outputs pulsed light at a predetermined cycle and a light receiving section 2 that receives the pulsed light from the light projecting section 1 and detects it. It is configured as follows.

The light receiving section 2 receives a pulsed light and converts it into a light receiving pulse signal, an amplifying circuit for amplifying the light receiving pulse signal, a comparator circuit 5, for binarizing the amplified light receiving pulse signal. It is composed of an integrating circuit 6 which outputs a detection signal when a predetermined number of digitized light receiving pulse signals are continuously input, and an output circuit 7 which outputs a signal to the outside based on the detection signal.

With such a structure, when the light projecting section 1 outputs pulsed light based on the light projecting pulse as shown in FIG. 6A, when there is no object to be shielded from the light receiving circuit 3. The light receiving circuit 3 receives the light, and the amplifier circuit 4 outputs a light receiving pulse signal corresponding to the light emitting pulse as shown in FIG.

When a predetermined number of, for example, four binarized light receiving pulse signals (see FIG. 4C) are output by the comparison circuit 5, the integrating circuit 6 outputs a detection signal as shown in FIG. Is output. As a result, it is detected that there is no light-shielding object such as an object between the light projecting section 1 and the light receiving section 2.

[0006]

However, the conventional structure as described above has the following problems.
That is, for example, as shown in FIG. 7A, when the two photoelectric sensors 8a and 8b are arranged with the optical axes adjacent to each other, the light projecting portions 1a and 1 of the photoelectric sensors 8a and 8b are arranged.
Since the pulsed light from b is output with a certain spread, each of the pulsed light is received by the light receiving portions 2a and 2b.
Will be received by.

Then, for example, as shown in FIG. 1B, even when the optical axis of the photoelectric sensor 8b is blocked by the object A, the pulsed light from the light projecting portion 1a of the photoelectric sensor 8a is photoelectrically converted. Since the light is received by the light receiving section 2b of the sensor 8b, it becomes impossible to detect that the optical axis is blocked in the light receiving section 2b.

Therefore, in order to avoid such a malfunction due to the interference of light, it is necessary to use the photoelectric sensors 8a and 8b in such a state that the optical axes of the photoelectric sensors 8a and 8b are apart from each other by a predetermined distance or more. Therefore, the following measures can be considered as measures for solving such a problem, but each of them also causes another problem as described later.

That is, firstly, as shown in FIG. 8, there is a method of narrowing the light beam of the pulsed light output from each of the light projecting portions 1a and 1b of the photoelectric sensors 8a and 8b. As a result, it is possible to narrow the optical axis pitch while avoiding malfunction due to light interference. However, in this case, since it is necessary to accurately adjust the optical axes of the photoelectric sensors 8a and 8b, it takes time, and there is a problem that the detection accuracy is lowered when the optical axes are displaced due to vibration or shock. .

Second, there is a method of providing a polarization filter having a different polarization direction on each of the photoelectric sensors 8a and 8b. A photoelectric filter of the first polarization direction is provided in the light projecting portion of the light projecting portion 1a of the photoelectric sensor 8a, and a polarizing filter of the same polarization direction is provided in the light receiving portion of the light receiving portion 2a facing the light receiving portion 2a to receive light. Similarly, the 8b is provided with a polarization filter of the second polarization direction, and pulsed lights from the light projecting sections 1b and 1a adjacent to each other are received by the light receiving sections 2a and 2b.
The light is prevented from being received by the light to prevent light interference.

However, in this case, since the pulsed light output from the light projecting section 1 passes through the two polarizing filters before reaching the light receiving section 2, there is a problem that the light intensity is lowered. For example, if the transmittance of the polarization filter is about 38%, the transmittance of the pulsed light reaching the light receiving unit 2 will be about 14.4%, which is converted into the detection distance. About 38% without
Will be reduced to.

Thirdly, the pulse light from the other photoelectric sensors is not received, but the width of the pulse light output from the light projecting unit 1 is set to be different from that between the other photoelectric sensors, It is considered that when the light receiving unit 2 receives the pulsed light of the set width, the light receiving unit 2 determines that the light is the pulsed light from its own light projecting unit 1.

However, in this case, in order to determine the pulse width of the pulsed light to be received, it is necessary to use an amplifier circuit 4 having a wide frequency characteristic in the light receiving section 2, and for that purpose, a motor is used. There is a problem in that it is likely to be adversely affected by noise generated from the above and causes a malfunction.

Also, unlike the transmission type photoelectric sensor as described above, the reflection type photoelectric sensor has a similar situation. For example, when the reflection type photoelectric sensor is provided as a collision prevention sensor in a vehicle traveling on a track. When a disturbance light is incident from its vicinity or receives a pulsed light from another photoelectric sensor while moving on the orbit, it is erroneously detected as reflected light of its own projection.

The present invention has been made in view of the above circumstances, and an object thereof is to simplify the optical axis adjustment and reduce the detection distance and noise resistance while preventing malfunctions due to interference of light from others as much as possible. It is an object to provide a photoelectric sensor that can perform a detection operation without causing it.

The photoelectric sensor of the present invention is a means for setting the number of output pulses of pulsed light, and a light projecting operation at a predetermined cycle, and the projecting operation is performed in a single projecting operation. A light projecting means for sequentially outputting the pulsed light of the number set by the light pulse number setting means at a constant time interval; a light receiving means for receiving the pulsed light from the light projecting means and converting it into a light receiving pulse signal; The number of light receiving pulse signals for judging the light receiving of pulsed light by the optical operation is the number of light emitting pulses.
At the timing of the light emitting operation, the light receiving pulse number setting means is set corresponding to the number set by the setting means .
It is characterized in that it is provided with a detecting means for outputting a light receiving detection signal when the number of light receiving pulse signals output from the light receiving means within a predetermined period matches the number set by the light receiving pulse number setting means. Have.

[0017]

According to the photoelectric sensor of the present invention, the light projecting means is
In a single projecting operation, the pulsed light of the output number set by the projecting pulse number setting means is sequentially output at a constant time interval. At this time, when the set number of outputs is “1”, only one pulsed light is output. When the light receiving means receives this pulsed light, it sequentially converts the light into a light receiving pulse signal and outputs the light receiving pulse signal, and the detecting means uses the light receiving pulse number setting means to determine the number of light receiving pulse signals within a predetermined period of the timing of the light projecting operation. A light reception detection signal is output when the number matches the set number. Thus, if the set number of the received light pulse number setting means is made to match the set number of the projected light pulse number setting means, for example, when a different number of pulsed light beams are input to the light receiving means from another projecting means. In addition, since the numbers of the received light pulse signals do not match, it can be determined that it is not the pulsed light from the light projecting means to be detected, and erroneous detection due to light interference can be prevented.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to a transmission type photoelectric switch will be described below with reference to FIGS.

FIG. 1 shows an electrical block configuration. In FIG. 1, the light projecting section 11 includes a light projecting pulse number setting circuit 12 as a light projecting pulse number setting means and a light projecting means as a light projecting means. The output terminal of the projection pulse number setting circuit 12 is connected to the setting input terminal of the projection circuit.

The light emitting pulse number setting circuit 12 sets the number of pulsed lights output by one light emitting operation as the light emitting pulse number n, and can be set to an integer of "1" or more. It has become.

The light projecting circuit 13 is one light projecting operation, and the number of light projecting pulses n set by the light projecting pulse number setting circuit 12 is n.
The light emitting element such as a light emitting diode sequentially emits a number of pulsed lights at a constant time interval, and such a light emitting operation is repeated at a predetermined light emitting cycle.

The light receiving section 14 is arranged so as to face the light projecting section 11 at a predetermined interval so as to receive the pulsed light from the light projecting circuit 13, and outputs a light receiving detection signal in accordance with the light receiving state. , Is constructed as follows. The light receiving circuit 15 as a light receiving means outputs light as a light receiving pulse signal when receiving light from the outside by a light receiving element such as a photodiode, and is connected to the comparison circuit 17 via the amplifier circuit 16. Has been done.

The amplifier circuit 16 amplifies the light receiving pulse signal output from the light receiving circuit 15 and supplies it to the comparison circuit 17, and the comparison circuit 17 binarizes the light receiving pulse signal input at a predetermined level and outputs it. Has become. The amplifier circuit 1
In No. 6, the frequency characteristic is set to a narrow frequency band so that only the band of the fundamental frequency of the received light pulse signal is amplified.

The detection circuit 18 as a detection means comprises a timer circuit 19, a counter circuit 20 and a judgment circuit 21. The timer circuit 19 has its input terminal connected to the output terminal of the comparison circuit 17, and outputs a signal of "H" level for a predetermined time T every time a binarized light receiving pulse signal is given from the comparison circuit 17. It has a function as a monostable multivibrator of the formula.

In the counter circuit 20, the input terminal A is connected to the output terminal of the comparison circuit 17, the control input terminal B is connected to the output terminal of the timer circuit 19, and the setting input terminal C is the light receiving pulse number setting means. It is connected to the output terminal of the received light pulse number setting circuit 22, and the output terminals D and E are connected to the input terminals A and B of the determination circuit 21, respectively. Further, the input terminal C of the determination circuit 21 is the timer circuit 19
Is connected to the output terminal of.

The light receiving pulse number setting circuit 22 sets the light receiving pulse number N for the light receiving determination, and the setting signal is input to the counter circuit 20. Then, the value of the received light pulse number N in the received light pulse number setting circuit 22 is set to the same number as the projected light pulse number n set in the projected light pulse number setting circuit 12.

The counter circuit 20 counts the number of binarized light receiving pulse signals input from the input terminal A,
When the counted number reaches the received light pulse number N set by the received light pulse number setting circuit 22, the output terminals D and E are output.
To output an "H" level signal. In this case, the counter circuit 20 holds the outputs of the output terminals D and E at the “H” level while the signal of the “H” level is given from the timer circuit 19, but the received light pulse signal is the number of received light pulses. When input exceeds N, only the output of the output terminal E is inverted to "L" level.

The determination circuit 21 outputs a light reception detection signal based on the signals input from the timer circuit 19 and the counter circuit 20 when the number of light reception pulse signals matches the set light reception pulse number N. The output terminal is connected to the input terminal of the integrating circuit 23.

The integrator circuit 23 integrates the received light detection signal from the determination circuit 21, and integrates the received light detection signal when the number of continuously received pulsed light detection signals exceeds a predetermined number. An output signal is generated when it reaches a predetermined value, and its output terminal is connected to the output circuit 24. The output circuit 24 is a circuit for outputting the signal given from the integration circuit 23 to the outside.

Next, the operation of this embodiment will be described with reference to FIG. In the present embodiment, the values of the number n of light projection pulses in the light projection pulse number setting circuit 12 and the number N of light reception pulses in the light receiving pulse number setting circuit 22 are “3”.
The case where it is set to will be described.

In the light projecting section 11, the light projecting circuit 13 determines that the value of the light projecting pulse number n set by the light projecting pulse number setting circuit 12 is "3". Three continuous pulsed lights are output by a light projecting element with a certain time interval. Then, the light projecting circuit 13 repeats such a light projecting operation at a predetermined cycle.

On the other hand, in the light receiving section 14, when there is no object that blocks the optical axis, the light receiving operation is performed as follows. First, in the light receiving circuit 15, the pulsed light incident on the light receiving element is converted into a light receiving pulse signal and amplified by the amplification circuit 16, and then the amplified signal Sa (FIG. 2).
(See (a)) is input to the comparison circuit 17.

In the comparison circuit 17, the input signal Sa is compared at a predetermined level and is output to the detection circuit 18 as a binarized light reception pulse signal Sb (see FIG. 7B).

The detection circuit 18 determines whether the received light pulse signal Sb is due to the pulsed light from the light projecting circuit 13 as described below. Now, for three consecutive pulsed lights emitted from the light emitting circuit 13,
A case where the interference light as shown in FIG. 2A is superimposed will be described as an example. That is, this is the case where one pulsed light (a), four continuous pulsed lights (c) and three discontinuous pulsed lights (e) are input to the detection circuit 18 as light reception pulse signals.

The interference light generated by one pulse light is detected by the detection circuit 1 as the received light pulse signal Sb (see (a) in FIG. 2A).
8 is input to the timer circuit 19, the timer circuit 19 is triggered and the signal Sc of "H" level for a certain time T
Is output (see (c) in the figure), and since the counter circuit 20 has not reached the number N of received light pulses, the output terminal D
And E do not output signals Sd and Se, and are "L".
It remains at the level (see (d) and (e) in the same figure).

In the judgment circuit 21, since the signal Sc from the timer circuit 19 is inverted to the "L" level, the output terminal E of the counter circuit 20 does not output the "H" level signal. , The light reception detection signal Sf is not output (see (f) in the figure).

Next, as shown in (b) and (d) of FIG. 7A, three continuous pulse lights from the light projecting circuit 13 are input to the detecting circuit 18 as the light receiving pulse signal Sb. In this case, the timer circuit 19 is triggered each time the received light pulse signal Sb is input, but since the time interval is shorter than the period in which the output is once at the “H” level, the same result is obtained. Continuous "H" as shown in Figure (c)
The level signal Sc continues to be output.

On the other hand, in the counter circuit 20, the input number of the received light pulse signal Sb is the received light pulse number setting circuit 22.
When the light receiving pulse number "3" set by is reached, the output terminals D and E output "H" level signals Sd and Se. In this case, since the continuous light receiving pulse signals Sb are "3" and are not input to the counter circuit 20 thereafter, the output signals Sd, Sd, S
At the same time, e is inverted to "L" level.

In the determination circuit 21, the timer circuit 19
Signals Sc from the output terminals D and E of the counter circuit 20 at the time when the signal Sc from the counters is inverted to the “L” level.
Since both e are at the "H" level, the "H" level light reception detection signal Sf (see (f) in the figure) is output.

Next, when four continuous pulsed lights due to the interference light shown in (c) of FIG. 7A are input to the detection circuit 18 as the received light pulse signal Sb, the timer circuit 19
In the same manner as described above, continues to output the "H" level signal Sc that is continuous during the period in which the four light receiving pulse signals Sb are input.

In the counter circuit 20, when three light receiving pulse signals are input, the output terminals D and E output "H" level signals Sd and Se, and thereafter, the output signal Sd from the output terminal D. Holds the output state of "H" level as it is even when the fourth light receiving pulse signal is input, but the output signal Se of the output terminal E is "L" at the time when the fourth light receiving pulse signal is input. It will be flipped to the level.

As a result, in the decision circuit 21, the signal Se from the output terminal E of the counter circuit 20 is reached when the signal Sc from the timer circuit 19 is inverted to the "L" level.
Is at the “L” level, the received light detection signal S
f is no longer output. That is, it is determined that the received light pulse signal Sb is not the light reception pulse signal Sb generated by the pulsed light from the light projecting circuit 13.

Next, as shown in (e) of FIG.
The number of pulsed lights is three, but when one pulsed light is incident as interference light at a time interval after the incidence of two continuous pulsed lights, the following operation is performed.

When two consecutive light receiving pulse signals Sb are input, the timer circuit 19 is continuously "H" during that time.
After the level Sc signal is output, the level returns to the “L” level, and subsequently, when one light receiving pulse signal Sb is applied with a time interval, the “H” level signal Sc is output again for the fixed time T.

In the counter circuit 20, after the two received light pulse signals Sb are counted, the counter circuit 20 is reset when the "H" level signal Sc from the timer circuit 19 disappears. At the time when the signal Sb is input, the first light receiving pulse signal Sn is counted again, and neither the output terminals D and E output the “H” level signals Sd and Se. .

Therefore, when such three pulse lights which are not continuous are input, the judgment circuit 21 does not output the light reception detection signal Sf either, and thereby the erroneous detection state due to the interference light is generated. It will disappear.

When three continuous pulsed lights from the light projecting circuit 13 as shown in (b) and (d) above are repeatedly input with a predetermined period, the integrating circuit 23 causes the judging circuit 21 to output. Since the result of integrating the received light detection signal Sf of S reaches the predetermined level, it is determined that the light receiving state and the output signal S
g (see (g) in the figure) is applied to the output circuit 24.

According to the present embodiment as described above, the timer circuit 19, the counter circuit 20 and the judging circuit 21 constitute the detecting circuit 18, and the light receiving pulse signal Sb by n pulse lights which are continuous at a constant time interval is inputted. Since the light reception detection signal Sf is output only when the light is emitted,
By setting the light emitting pulse number n and the light receiving pulse number N between 1 and the light receiving unit 14 to be the same value, it is possible to reliably prevent erroneous detection even when interference light is received.

As a result, it is not necessary to narrow down the light beam of the pulsed light from the light projecting unit 11, the optical axis adjustment becomes simple, and the detection accuracy against vibrations and shocks can be prevented from lowering.
Moreover, since it is not necessary to provide a polarization filter, the intensity of the pulsed light does not decrease, and the detection distance does not decrease. Furthermore, since the frequency band of the amplifier circuit 16 can be narrowed by receiving the pulsed light of a fixed time width, it is possible to prevent the adverse effect of external noise generated from the motor or the like.

When the number n of light projection pulses and the number N of light reception pulses are set to a value of "2" or more, external noise light due to, for example, a fluorescent lamp or spatter is sporadically received.
Even if the noise light is incident on the light source 5, the noise light can be nullified, so that erroneous detection due to ambient light can be prevented as much as possible.

FIGS. 3 and 4 show a second embodiment of the present invention. The difference from the first embodiment is that a detection circuit 25 is provided instead of the detection circuit 18, which will be described below. Will be described.

That is, in FIG. 3 showing the electrical configuration of the detection circuit 25, the input terminal of the first timer circuit 26 is connected to the output terminal of the comparison circuit 17, and the output terminal thereof is one input terminal of the AND circuit 27. And an input terminal of the second timer circuit 28. AND circuit 2
The other input terminal of 7 is connected to the output terminal of the comparison circuit 17, and its output terminal is connected to the input terminal A of the counter circuit 29.

The first timer circuit 26 is a retrigger type monostable multivibrator which outputs an "H" level signal for a fixed time T each time the binarized light receiving pulse signal is given from the comparison circuit 17. It has a function. Further, the second timer circuit 28 outputs an "H" level signal for a certain period of time at the timing when the "H" level input signal from the first timer circuit 26 falls.
The output terminal is connected to the input terminal of the third timer circuit 30.

The third timer circuit 30 outputs an "H" level signal for a certain period of time at the timing when the "H" level input signal from the second timer circuit 28 falls, and its output terminal is a counter. It is connected to the reset input terminal R of the circuit 29.

The counter circuit 29 counts the number of pulses given from the input terminal A and sequentially outputs "H" level signals to a plurality of output terminals B1 to B6 corresponding to the count value. B1 to B6 are connected to the respective switching terminals a1 to a6 of the changeover switch 31 which is the light receiving pulse number setting means. The movable contact terminal c of the changeover switch 31 is connected to the data input terminal D of the D-type flip-flop 32 and also to the first input terminal of the AND circuit 33 having three input terminals.

The reset input terminal R of the flip-flop 32 is connected to the output terminal of the third timer circuit 30, and the output terminal Q is connected to the second input terminal of the AND circuit 33. Further, the third input terminal of the AND circuit 33 is connected to the output terminal of the second timer circuit 28, and its AN
The output terminal of the D circuit 33 is connected to the input terminal of the integrating circuit 23.

Next, the operation of this embodiment will be described with reference to FIG. Also in this embodiment, the number n of projection pulses in the projection pulse number setting circuit 12 is set to "3", and the changeover switch 31 is also set to the position B3 where the number N of received light pulses is "3". The case where it is performed will be described.

First, the interference light as one pulsed light enters the light receiving circuit 15, and the received light pulse signal Sh (see FIG. 4).
When (a) (see (a)) is input to the detection circuit 25, the operation is as follows. That is, the first timer circuit 26 outputs the signal Si at the “H” level for a certain period of time T (see FIG. 7B), and when the signal Si inverts to the “L” level, the second timer circuit 28. "H" for a certain time
When the signal Sj of the level is output (see (c) in the figure), and then the signal is inverted to the "L" level, the third timer circuit 30 outputs the signal Sk of the "H" level for a certain period of time. (See (d) in the figure).

However, since only one received light pulse signal Sh is input to the counter circuit 29, no "H" level signal is output to the output terminal B3 of the changeover switch 31, and therefore the AND circuit 33 is used. The output terminal of is still at "L" level, and no light reception detection signal is output.

Also, when the interference light as two continuous pulse lights shown in (b) of FIG. 2A is input as the light reception pulse signal Sh, the light reception detection signal is output in the same manner as described above. Not done.

Next, as shown in (c) of FIG.
When three consecutive pulsed lights from the light projecting circuit 13 are input to the detecting circuit 25 as the light receiving pulse signal Sh,
The counter circuit 29 outputs an “H” level signal from the output terminal B3 when the third light receiving pulse signal Sh is input.

As a result, the "H" level signal Sm is applied to the data input terminal D of the flip-flop 32 via the changeover switch 31, and the "H" level signal Sn is output from the output terminal Q. The "H" level signal is applied to the first and second input terminals of the AND circuit 33. After this, since the light receiving pulse signal Sh is not given, the counter circuit 29 outputs "H" from the output terminal B3.
Continues to output the level signal.

On the other hand, the first timer circuit 26 outputs the signal Si at the "H" level for a fixed time T after the third light receiving pulse signal Sh is input, and then sets the output to the "L" level. Invert. Then, the second timer circuit 2
8 outputs an "H" level signal Sj for a certain period of time. At this time, the “H” level signal Sj from the second timer circuit 28 is given to the third input terminal of the AND circuit 33, and A
The ND circuit 33 outputs the received light detection signal Sp at the “H” level (see (g) in the figure).

Thereafter, when the output signal Sj from the second timer circuit 28 is inverted to the "L" level, the AND circuit 33.
Inverts the output to the “L” level, and the third timer circuit 30
Outputs the signal Sk of "H" level for a certain period of time. As a result, the counter circuit 29 and the flip-flop 32 are reset when the reset terminal R is supplied with the “H” level signal Sk.

Next, when the interference light as four continuous pulsed lights shown in (d) of FIG. 9A is input to the detection circuit 25 as the light reception pulse signal Sh, the third light reception is performed. The same operation as described above is performed until the pulse signal Sh is input, but when the fourth light receiving pulse signal Sh is input, the output signal Si is output in the first timer circuit 26.
Is held at the "H" level for a certain time T, and the counter circuit 29 inverts the output signal from the output terminal B3 to the "L" level.

As a result, when the output signal Si of the first timer circuit 26 is inverted to the "L" level and then the "H" level signal Sj is output from the second timer circuit,
Counter circuit 29 to the first input terminal of AND circuit 33
Since the signal Sm from the signal is inverted to the "L" level, the light reception detection signal is not output.

Further, the interference light in which two continuous pulsed lights and one pulsed light shown in (e) of FIG. When input to, it operates as follows. That is, in the same manner as in the case (b) of FIG.
Since the counter circuit 29 is reset by the reset signal Sk from the third timer circuit 30 after the two light receiving pulse signals Sh are input and before the third light receiving pulse signal Sh is input, At the time when the second light reception pulse signal Sh is input, the same operation as in the case of (a) of FIG. 4A is performed again, and the light reception detection signal is not output after all.

Therefore, also in such a second embodiment, the same effect as that of the first embodiment can be obtained.

In each of the above embodiments, the case where the present invention is applied to the transmission type photoelectric sensor has been described.
The invention is not limited to this, and may be applied to, for example, a reflective photoelectric sensor.

Further, in each of the above embodiments, the light receiving detection signal from the detection circuit 18 or 25 is integrated by the integrating circuit 23 to output the output signal, but the present invention is not limited to this, and for example, at a predetermined timing. It may be configured by a circuit that digitally counts continuous light receiving detection signals and outputs an output signal.

Furthermore, in each of the above-described embodiments, the case where the whole is configured by a hardware circuit has been described, but the present invention is not limited to this, and for example, by a microcomputer or the like,
The same function may be configured as a software program.

[0072]

As described above, in the photoelectric sensor of the present invention, the output number of pulsed light in the light projecting means is set by the light projecting pulse number setting means, and the light receiving pulse is set by the light receiving pulse number setting means accordingly. Set the number and by the detection means
The light receiving detection signal is output by determining whether or not the light receiving pulse signal output from the light receiving means matches the set number of light receiving pulses within a predetermined period of the timing of the light projecting operation . Thus, if the set number of the received light pulse number setting means is made to match the set number of the projected light pulse number setting means, for example, when a different number of pulsed light beams are input to the light receiving means from another projecting means. In this case, since the numbers of the received light pulse signals do not match, it can be determined that it is not the pulsed light from the light projecting means to be detected. Therefore, it is possible to prevent erroneous detection due to the interference of other light from the outside, and it is possible to simplify the optical axis adjustment by eliminating the need to narrow the light beam, and further reduce the detection distance and noise resistance. It has an excellent effect of eliminating.

[Brief description of drawings]

FIG. 1 is a block diagram of an electrical configuration showing a first embodiment of the present invention.

FIG. 2 is a time chart showing a signal output state of each part.

FIG. 3 is a block diagram of an electrical configuration of a detection circuit showing a second embodiment of the present invention.

FIG. 4 is a view corresponding to FIG.

FIG. 5 is a view corresponding to FIG. 1 showing a conventional example.

FIG. 6 is a view corresponding to FIG.

FIG. 7 is a layout view of a photoelectric sensor for explaining a conventional defect

FIG. 8 is a view corresponding to FIG.

[Explanation of symbols]

11 is a light projecting unit, 12 is a light projecting pulse number setting circuit (light projecting pulse number setting means), 13 is a light projecting circuit (light projecting unit), 14 is a light receiving unit, 15 is a light receiving circuit (light receiving unit), and 16 is Amplifier circuit, 17 is a comparison circuit, 18 is a detection circuit (detection means), 1
Reference numeral 9 is a timer circuit, 20 is a counter circuit, 21 is a determination circuit, 22 is a light receiving pulse number setting circuit (light receiving pulse number setting means), 23 is an integrating circuit, 24 is an output circuit, 25 is a detecting circuit (detecting means), 26. Is a first timer circuit and 28 is a second
, 29 is a counter circuit, 30 is a third timer circuit, 31 is a switching circuit, 32 is a D-type flip-flop, and 27 and 33 are AND circuits.

Claims (1)

(57) [Claims] 1. A projection pulse number setting means for setting the output number of pulsed light, and a projection operation at a predetermined cycle, wherein the projection pulse number setting means is performed in one projection operation. And a light receiving means for receiving pulsed light from the light emitting means and converting it into a light receiving pulse signal, and a pulsed light for the light emitting operation. the light projection pulse the number of pulses received signal for the received determination
The number of light-receiving pulses set by the number set by the number-of- lights setting means, and the number of light-receiving pulse signals output from the light-receiving means within a predetermined period at the timing of the light-projecting operation is the number of light-receiving pulses. A photoelectric sensor, comprising: a detection unit that outputs a light reception detection signal when the number matches the number set by the setting unit.