JPH07212208A - Optical fiber type photoelectric switch - Google Patents

Abstract

PURPOSE:To confirm whether the optical axes of optical fibers are matched or not at a detection part by alternately projecting first and second flood pulses when the level of a photodetected pulse provided at a photodetection part exceeds a detective level. CONSTITUTION:When the optical axes of optical fibers are matched, the level of the photodetected pulse gets higher than the level to be detected by a comparator 23, and the comparator 23 outputs a pulse. This pulse output is inputted to a detection circuit 24, the pulse output of the comparator 23 at the time of outputting a pulse from an AND gate 16 is validized and when this valid pulse output is applied plural times such as continuously several times, for example, a detecting signal P1 is outputted. Since a pulse output b8 frequency- divided into eight stages is inputted from a frequency divider circuit 12 to one input terminal of an OR gate 42, the pulse output b8 is inputted to an input terminal (a) of a selector circuit 47, and the pulse output of the AND gate 16 with the narrow pulse duration and a pulse output b4 of the frequency divider circuit 12 with the wide pulse duration are alternately selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a light projecting section, a light receiving section and a detecting section. The light projecting section is connected to the detecting section, and the detecting section and the light receiving section are connected by an optical fiber. The present invention relates to an optical fiber type photoelectric switch that detects a subject based on the level of the received light pulse.

[0002]

2. Description of the Related Art FIG. 8 is a circuit diagram showing an example of a conventional optical fiber type photoelectric switch. In FIG. 8, the optical fiber type photoelectric switch includes a light projecting unit 1 and a light receiving unit 2. The light projecting unit 1 includes a pulse oscillation circuit 11 and the pulse oscillation circuit 1.
1 pulse output b1 is input, and this pulse output is frequency-divided by 2 divided pulse output b2, 4 divided pulse output b4, 8
A frequency dividing circuit 12 for outputting a frequency-divided pulse output b8 ...
A which outputs a logical sum pulse output of the pulse output b1, the divided pulse output b2, the divided pulse output b4, and the divided pulse output b8
The ND gate 13 and a light projecting pulse signal from the AND gate 13 are input via a current limiting resistor 14 and a light projecting element 15 such as an LED that projects a light projecting pulse. In the light receiving unit 2, a light receiving element 21 such as a photodiode, an amplifier circuit 22 for amplifying the output of the light receiving element 21, and an output of the amplifier circuit 22 (hereinafter referred to as a light receiving pulse signal) are set as a threshold. A comparator 23 that outputs a pulse when a value (hereinafter referred to as a detection level) is exceeded, a pulse output of this comparator 23, and a light projection pulse signal from the AND gate 13 of the light projecting unit 1 are input, and a light projection pulse is input. A detection circuit 24 that validates only the pulse output of the comparator 23 when a signal is being output, and outputs the detection signal P ₁ when this valid pulse output is repeated a plurality of times, for example, several times, and this detection signal P
₁ output circuit 25. And the light projecting section 1
The light projecting optical fiber 31 is coupled to the light projecting element 15 so that the front end face thereof opposes to the light receiving element 21 of the light receiving section 2.
The light-receiving optical fiber 32 is coupled so that its front end faces oppose each other, and the end faces of the light-projecting optical fiber 31 and the light-receiving optical fiber 32 on the front end side are the voids 33 as the detection part of the subject. Place it across.

The operation of this optical fiber type photoelectric switch will be described with reference to the waveform chart shown in FIG. In FIG.
(1) is the pulse output b1, (2) of the pulse oscillation circuit 11.
Is the frequency-divided pulse output b2 of the frequency dividing circuit 12, and (3) is the same as 4
Frequency-divided pulse output b4, (4) is the same frequency-divided pulse output b8
Indicates. FIG. 9 (5) shows the pulse output of the AND gate 13,
That is, it shows a light emission pulse signal, and each pulse output b
It is the logical sum output of 1, b2, b4 and b8.
This light projection pulse signal is input to the light projecting element 15, and a light projection pulse corresponding to this light projection pulse signal is generated.
It is projected to 1. FIG. 9 (6) shows the amplifier circuit 22 of the light receiving unit 2.
Of the light receiving pulse signal. The light receiving pulse signal is a light projecting pulse projected onto the light projecting optical fiber 31.
The light is received by the light receiving element 21 through 2 and amplified by the amplifier circuit 22. When the received light pulse signal exceeds the detection level, the comparator 23 outputs a pulse as shown in FIG. 9 (7), and the detection circuit 24 outputs the output pulse and the light emitting pulse signal of the light projecting unit 1 from the output pulse. When the optical pulse signal is being output, the pulse output of the comparator 23 is validated, and when the valid pulse output is repeated a plurality of times, for example, several times, the detection signal P ₁ shown in FIG. 9 (8) is output. . The detection signal P ₁ is input to the output circuit 10, amplified, and output from the signal terminal P. The detection circuit 24
However, the reason why the detection signal P ₁ is first output when the effective pulse output from the comparator 23 is a plurality of consecutive times is to prevent malfunction due to noise.

[0004]

By the way, in the optical fiber type photoelectric switch, it is necessary to align the optical axes of the end faces of the light projecting optical fiber and the light receiving optical fiber in the detecting section. Normally, the operation is performed while checking the operation indicator lamp provided in the light receiving section.
However, in the optical fiber type photoelectric switch, the light receiving part and the detecting part are generally arranged apart from each other, and therefore, when the optical axis of the optical fiber is aligned, the operation state of the operation indicator lamp of the light receiving part located far from the detecting part is changed. There is a problem that is very troublesome to check. In addition, if the optical axes of the light projecting optical fiber and the light receiving optical fiber are not aligned correctly, a malfunction may occur due to slight contamination of the end faces of these optical fibers.

An object of the present invention is to make it possible to confirm whether or not the optical axes of the optical fibers are matched with each other in the optical axis alignment of the optical fibers in the detecting section.

[0006]

In order to achieve the above-mentioned object, the present invention according to claim 1 comprises a light projecting section, a light receiving section and a detecting section, and the light projecting section, the detecting section and the detecting section. In the optical fiber type photoelectric switch, in which an optical fiber is connected between the light receiving unit and the light receiving unit, and the object is detected by the level of the light receiving pulse obtained by the light receiving unit, the light emitting unit includes the first light emitting pulse and the first light emitting pulse. Of the second light emitting pulse having a wider pulse width than the light emitting pulse of the second light emitting pulse, and the first light emitting pulse is emitted when the level of the light receiving pulse obtained by the light receiving unit is below the detection level. However, when the level of the light receiving pulse obtained by the light receiving unit exceeds the detection level, a selecting means for alternately projecting the first light projecting pulse and the second light projecting pulse is provided. To do.

According to the second aspect of the invention, the light projecting section projects the first light projecting pulse and the second light projecting pulse having a wider pulse width than the first light projecting pulse. Means and
When the level of the light receiving pulse obtained by the light receiving section is lower than the set level higher than the detection level, the first light emitting pulse is emitted, and when the level of the light receiving pulse obtained by the light receiving section exceeds the set level, , And selection means for alternately projecting the first light projection pulse and the second light projection pulse.

Further, in the invention described in claim 3, the light projecting section projects the first light projecting pulse and the second light projecting pulse having a pulse width wider than the first light projecting pulse. Means and
When the level of the light receiving pulse obtained by the light receiving unit is below the detection level, the first light emitting pulse is emitted, and when the level of the light receiving pulse obtained by the light receiving unit exceeds the detection level,
And a selecting unit for alternately selecting and projecting the first light projecting pulse and the second light projecting pulse. To do so.

Further, in the invention described in claim 4, the light projecting section projects the first light projecting pulse and the second light projecting pulse having a wider pulse width than the first light projecting pulse. Means and
When the level of the light receiving pulse obtained by the light receiving section is lower than the set level higher than the detection level, the first light emitting pulse is emitted, and when the level of the light receiving pulse obtained by the light receiving section exceeds the set level, A selecting means for alternately selecting and projecting the first light projecting pulse and the first light projecting pulse and the second light projecting pulse. Be prepared.

Further, according to the invention described in claim 5, the light projecting section is responsive to the level of the first light projecting pulse and the light receiving pulse obtained by the light receiving section, if the level of the light receiving pulse is equal to or lower than the detection level. When the pulse width is narrower than the first light projecting pulse and the level of the light receiving pulse is equal to or higher than the detection level, the light projecting means projects the third light projecting pulse whose pulse width is wider than the first light projecting pulse. And a selecting means for alternately projecting the first light projection pulse and the third light projection pulse.

[0011]

According to the present invention, when the level of the light receiving pulse obtained by the light receiving section is below the detection level, the first light projecting pulse is projected, and when the level of the light receiving pulse exceeds the detection level, Since one light projecting pulse and the second light projecting pulse having a pulse width wider than the first light projecting pulse are alternately projected, the end face of the light projecting optical fiber becomes bright when the optical axes of the optical fibers coincide with each other. Become. Further, in the invention according to claim 3, the first light projection pulse is projected when the level of the light reception pulse obtained by the light receiving portion is equal to or lower than the detection level, and the first light projection pulse is emitted when the level of the light reception pulse exceeds the detection level. The state in which the light emission pulse is emitted, the first light emission pulse and the first light emission pulse
The second light projection pulse having a wider pulse width than the light projection pulse is alternately selected and projected. Therefore, if the optical axes of the optical fibers coincide with each other, It looks like the end face is blinking, and the visibility is improved.

Further, in the invention described in claim 2 or 4, instead of the detection level of the light receiving pulse in claim 1 or 3, a set level higher than this detection level is used, so that the optical axis of the optical fiber is used. At the time of alignment, there is a margin in the output level of the detection signal as the photoelectric switch, and the alignment of the optical axes of the optical fibers becomes more reliable. According to the fifth aspect of the invention, depending on the level of the light receiving pulse obtained by the light receiving section, when the light receiving level is below the detection level, the first light projecting pulse and the pulse width thereof are narrower than the first light projecting pulse. When the controlled third light emitting pulse is emitted alternately and the level of the light receiving pulse exceeds the detection level,
Since the first light projecting pulse and the third light projecting pulse whose pulse width is controlled to be wider than the first light projecting pulse are projected alternately, depending on the degree of coincidence of the optical axes of the optical fibers. The end face of the light projecting optical fiber becomes bright, and the optical axis alignment becomes easier.

According to these inventions, it is possible to confirm whether or not the optical axes of the optical fibers are coincident with each other in the detecting section for aligning the optical axes of the optical fibers.

[0014]

1 is a circuit diagram showing an embodiment of an optical fiber type photoelectric switch of the present invention. In FIG. 1, the optical fiber type photoelectric switch includes a light projecting unit 1 and a light receiving unit 2. The light projecting unit 1 receives a pulse oscillation circuit 11 and a pulse output b1 of the pulse oscillation circuit 11, and outputs the pulse output. Divided by 2 pulse output b2, divided by 4 pulse output b4
Frequency dividing circuit 12 for outputting divided-by-8 pulse output b8 ...
AND gate 16 which outputs a logical sum pulse output of these pulse output b1, frequency-divided pulse output b2 and frequency-divided-quarter pulse output b4, and frequency divider circuit 1 at one of its input terminals.
The OR gate 42 to which the 2 divided-by-8 pulse output b8 is input
An AND gate 43 to which the divide-by-four pulse output b4 of the frequency dividing circuit 12 is input to one input terminal and the pulse output of the OR gate 42 is input to the other input terminal via an inverter 44; The pulse output of the OR gate 42 is input to one input terminal and A is input to the other input terminal.
The pulse output of the ND gate 16 is supplied to the AND gate 45, the OR gate 46 to which the pulse outputs of the AND gates 43 and 45 are input to both input terminals thereof, and the pulse output of the OR gate 46 via the current limiting resistor 14. It is composed of a light projecting element 15 such as an LED, which projects a light projecting pulse which is input. Further, the light receiving section 2 includes a light receiving element 21 formed of, for example, a photodiode, an output of the light receiving element 21 and an amplifier circuit 22, and a threshold value (hereinafter referred to as a light receiving pulse signal) set by the output of the amplifier circuit 22 The comparator 23 that outputs a pulse when the detection level is exceeded), the pulse output of the comparator 23 and the pulse output from the AND gate 16 of the light projecting unit 1 are input, and the pulse output from the AND gate 16 is output. Only the pulse output of the comparator 23 that is being output is validated, and the detection circuit 24 that outputs the detection signal P ₁ when this valid pulse output is repeated a plurality of times, for example, several times, and the detection circuit 24. An inverter 48 for inverting the pulse output and inputting it to the other input terminal of the OR gate 42 of the light projecting unit 1, and a detection signal of the detection circuit 24. And an output circuit 25 for outputting the signal terminal P by amplifying the P _1.

Here, the AND gate 43 and the inverter 4
4, AND gate 45 and OR gate 46 form a selector circuit 47, and a connection point between the input terminal of the inverter 44 and the AND gate 45 (hereinafter referred to as a selection terminal).
When the signal input to a is "H" level, the OR gate 46 selects and outputs the signal input to the other terminal of the AND gate 45, and the signal input to the input terminal of the inverter 44 is "L". , The OR gate 46 selects and outputs the signal input to one terminal of the AND gate 43.

Others are the same as those of the conventional optical fiber type photoelectric switch shown in FIG. The operation of this optical fiber type photoelectric switch will be described with reference to the waveform chart shown in FIG. In FIG. 6, (1) is the pulse output b1 of the pulse oscillator circuit 11, (2) is the frequency-divided pulse output b2 of the frequency dividing circuit 12, (3) is the same frequency division pulse output 4 and (4) is the same frequency division pulse output b4. The divided pulse output b8 is shown. FIG. 6 (5) shows the pulse output of the AND gate 16, and each pulse output b1,
This is the logical sum output of b2 and b4. Since the pulse output of the AND gate 16 is input to the detection circuit 24 of the light receiving section 2, the detection circuit 24 validates only the pulse output of the comparator 23 when this pulse output is output, and the effective pulse output Is output a plurality of times, for example, several times in succession, the detection signal P ₁ is output.

Here, assuming that the optical axis of the optical fiber is aligned in the detecting section 33, when the optical axis of the optical fiber does not match, the level of the received light pulse is lower than the detection level of the comparator 23, and the comparator 23 No pulse is output. Therefore, since the detection signal P ₁ is not output from the detection circuit 24, that is, the output terminal of the detection circuit 24 is at “L” level, the other input terminal of the OR gate 42 becomes “H” level and the input of the selector circuit 47. The terminal a becomes "H" level. Therefore, this selector circuit 4
The pulse output of the AND gate 16 is output from the OR gate 46 of No. 7 and is input to the light projecting element 15. Since this pulse output is a narrow pulse as shown in FIG. 6 (5), the end face of the light projecting optical fiber is dark. Next, when the optical axes of the optical fibers coincide with each other, the level of the light receiving pulse becomes higher than the detection level of the comparator 23 as shown in FIGS. 6 (7) and (8), and the comparator 23 outputs a pulse.
This pulse output is input to the detection circuit 24, and the pulse output of the comparator 23 when the pulse is output from the AND gate 16 is validated, and this valid pulse output is detected a plurality of times, for example, several times in succession. The signal P ₁ is output. That is, the output terminal of the detection circuit 24 is "H".
Since it becomes the level, the other input terminal of the OR gate 42 becomes the "L" level. Since the divide-by-eight pulse output b8 of the frequency dividing circuit 12 is input to one input terminal of the OR gate 42, the pulse output b8 is input to the input terminal a of the selector circuit 47, and the pulse width is narrow. The pulse output of the AND gate 16 and the pulse output b4 of the frequency dividing circuit 12 having a wide pulse width are alternately selected, and the light projecting element 15 has the pulse output b4 shown in FIG.
The light projecting pulse signal shown in (6) is input, and the end surface of the light projecting optical fiber in the detecting section becomes bright.

FIG. 2 is a circuit diagram showing another embodiment of the optical fiber type photoelectric switch of the present invention. The difference between the embodiment shown in FIG. 2 and the embodiment shown in FIG.
Has a long pulse output width at the input terminal of, for example,
The point is that the 28-divided pulse output b128 is additionally connected. Although the operation waveform diagram of this optical fiber type photoelectric switch is omitted, when the optical axis is aligned with the optical axis of the optical fiber and the output terminal of the detection circuit 24 becomes the “H” level, the AND gate 16 having a narrow pulse width. Of the AND circuit 16 having a narrow pulse width and the pulse output b4 having a wide pulse width of the frequency dividing circuit 12 are alternately output. Since the circular pulse output b128 is alternately selected with a long cycle, the end surface of the light projecting optical fiber in the detection unit looks like blinking, and the visibility is improved.

FIGS. 3 and 4 are circuit diagrams showing further different embodiments of the optical fiber type photoelectric switch of the present invention. The difference between FIG. 3 and FIG. 4 from FIG. 1 and FIG. (Hereinafter referred to as the first comparator) 23, and a second comparator 26 whose threshold level is higher than the detection level of the first comparator 23 are provided in parallel, and the detection circuit 24 uses the AND gate 1
When the pulse output from 6 is output, the pulse output of the second comparator 26 is validated, and when this valid pulse output is repeated a plurality of times, for example, several times, the detection signal is input to the input terminal of the inverter 48. The point is that P ₂ is output.

In these optical fiber type photoelectric switches, the detection signal P ₂ having a higher level than the detection signal P ₁ is supplied to the inverter 4
Since the signal is input to the selection terminal a of the selector circuit 47 via 8, the output level of the detection signal as the photoelectric switch can have a margin when the optical axis of the optical fiber is aligned, and the optical axis alignment becomes more reliable. FIG. 5 is a circuit diagram showing a further different embodiment of the optical fiber type photoelectric switch of the present invention. In FIG. 5, the optical fiber type photoelectric switch includes a light projecting unit 1 and a light receiving unit 2.
The light projecting unit 1 is provided with a pulse oscillating circuit 11 and a pulse output b1 of the pulse oscillating circuit 11, and divides the pulse output by a divided-by-2 pulse output b2, a divided-by-4 pulse output b4. A frequency divider circuit 12 for outputting a divided-by-8 pulse output b8 ... And an AND gate 16 for outputting a logical sum pulse output of these pulse outputs b1, b2 and b4 and b4, The divide-by-4 pulse output b4 of the divider circuit 12 is connected to one of the input terminals of the resistor 63.
Integrator circuit 65 in which capacitor 64 and capacitor 64 are connected in an inverted L shape
AND gate 61 in which the pulse output of the comparator 62 is input to one of its input terminals and the divide-by-4 pulse output b4 of the frequency dividing circuit 12 is input to the other input terminal. And the pulse output of the AND gate 61 is input to one of its input terminals,
Frequency divider circuit 1 via the inverter 44 to the other input terminal
AND gate 4 to which the 2 divided-by-8 pulse output b8 is input
3 and an AND gate 45 to which the divide-by-8 pulse output b8 of the divider circuit 12 is input to one input terminal and the output pulse of the AND gate 41 is input to the other input terminal.
And an OR gate 46 into which the output pulses of the AND gate 43 and the AND gate 45 are input to both input terminals, and the pulse output of this OR gate 46 is the current limiting resistor 1
4 is input to emit a light emitting pulse, for example, L
It is composed of a light projecting element 15 such as an ED. In addition, the light receiving unit 2 includes a light receiving element 21 including a photodiode, for example.
When the output of the light receiving element 21 and the output of the amplifier circuit 22 (hereinafter referred to as a light receiving pulse signal) exceed a set threshold value (hereinafter referred to as a detection level), a pulse is output. The comparator 23, the pulse output of the comparator 23, and the pulse output from the AND gate 16 of the light projecting unit 1 are input to the AND gate 1
Only the pulse output of the comparator 23 when the pulse output from 6 is being output is effective, and when this effective pulse output is repeated a plurality of times, for example, several times, the detection signal P
_The detection circuit 24 that outputs ₁ and a pulse output of the amplification circuit 22 are composed of a capacitor 67 that is input via an analog switch 66 that is turned on by the output of the AND gate 16. The charging voltage of this capacitor 67 is the other of the comparator 62. Sample hold circuit 68 input to the input terminal
And the detection signal P ₁ of the detection circuit 24 is amplified to a signal terminal P
And an output circuit 25 for outputting from. The integration circuit 65, the comparator 62, and the sample hold circuit 68 form a light reception level pulse width conversion circuit 69 that converts the level of the light reception pulse signal into a pulse width.
The ND gate 43, the inverter 44, the AND gate 45 and the OR gate 46 form a selector circuit 47.

The operation of this optical fiber type photoelectric switch will be described with reference to the waveform chart shown in FIG. 7 (1) to 7 (5) are the same as FIGS. 6 (1) to 6 (5), and FIG. 7 (6) shows the integration circuit 65 of the pulse width conversion circuit 69.
And the dotted line A in this figure indicates the threshold value determined by the sample hold circuit 68. This threshold value A is low as shown by the threshold value Aa when the level of the light receiving pulse is low, and is low when the level of the light receiving pulse is high.
It becomes higher as shown in b. Therefore, the pulse output from the comparator 62 has a pulse width of, for example, A when the threshold A is low as Aa as shown in FIG. 7 (7).
A pulse narrower than the pulse output of the ND gate 16 has a pulse width wider than that of the pulse output of the AND gate 16 when the threshold value A is as high as Ab.
The pulse output of the comparator 62 is the AND gate 6
1 is input to one input terminal of the AND gate 61. Therefore, the output of the AND gate 61 is input to one terminal of the AND gate 43 of the selector circuit 47 only while the divide-by-4 pulse output b4 of the divider circuit 12 is being output. Is entered. On the other hand, the other terminal of the AND gate 45 of the selector circuit 47 has an AND
The pulse output of the gate 16 is input to the selector circuit 47.
To the select terminal a of the dividing circuit 12 divided by 8 pulse output b8
Is input to the OR gate 46 of the selector circuit 47.
7 (8), the pulse output of the AND pulse output from the AND gate 41 and the pulse width of the pulse output from the AND gate 41 are smaller than the pulse output from the AND gate 41 as shown in FIG. 7 (8). Narrow pulses are alternately output, and when the level of the received light pulse is equal to or higher than the detection level, a pulse output from the AND gate 16 and a pulse having a wider pulse width than the pulse output from the AND gate 16 are alternately output. Therefore, in this photoelectric switch, the end face of the light projecting optical fiber becomes brighter according to the degree of matching of the optical axes of the optical fibers, and the optical axis alignment becomes easier.

[0022]

In the optical fiber type photoelectric switch of the present invention, since it can be confirmed from the brightness of the light projecting optical fiber in the detecting section whether or not the optical axis of the optical fiber matches, it is provided in the light receiving section. Even when you can't see the operation indicator light,
In addition, the optical axis of the optical fiber can be surely aligned.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing another embodiment of the optical fiber type photoelectric switch of the present invention.

FIG. 3 is a circuit diagram showing a further different embodiment of the optical fiber type photoelectric switch of the present invention.

FIG. 4 is a circuit diagram showing still another embodiment of the optical fiber type photoelectric switch of the present invention.

FIG. 5 is a circuit diagram showing a further different embodiment of the optical fiber type photoelectric switch of the present invention.

6 is a waveform diagram showing the operation of the optical fiber type photoelectric switch of the present invention shown in FIG.

FIG. 7 is a waveform diagram showing the operation of the optical fiber type photoelectric switch of the present invention shown in FIG.

FIG. 8 is a circuit diagram showing an example of a conventional optical fiber type photoelectric switch.

9 is a waveform chart showing the operation of the conventional optical fiber type photoelectric switch shown in FIG.

[Explanation of symbols]

 1 Light Emitting Section 2 Light Receiving Section 31 Light Emitting Optical Fiber 32 Light Receiving Optical Fiber 33 Void (Detecting Section)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Setsuo Makino 2-12-12 Sonezaki, Kita-ku, Osaka City, Osaka Prefecture Hokuyo Electric Co., Ltd. No. 1 inside Fuji Electric Co., Ltd.

Claims (5)

[Claims] 1. A light emitting section, a light receiving section, and a detecting section, wherein the light projecting section and the detecting section, and the detecting section and the light receiving section are connected by an optical fiber, and a light receiving pulse of the light receiving section is connected. In an optical fiber type photoelectric switch for detecting an object according to a level, a light projecting section projects a first light projecting pulse and a second light projecting pulse having a pulse width wider than the first light projecting pulse. And the level of the light receiving pulse obtained by the light receiving unit is below the detection level, the first light emitting pulse is emitted, and when the level of the light receiving pulse obtained by the light receiving unit exceeds the detection level, An optical fiber type photoelectric switch, comprising: a selection unit that alternately projects the first light projection pulse and the second light projection pulse. 2. A light projecting section, a light receiving section and a detecting section, wherein the light projecting section and the detecting section, and the detecting section and the light receiving section are connected by an optical fiber, and a light receiving pulse obtained by the light receiving section is connected. In an optical fiber type photoelectric switch for detecting an object according to a level, a light projecting section projects a first light projecting pulse and a second light projecting pulse having a pulse width wider than the first light projecting pulse. And the level of the light receiving pulse obtained by the light receiving unit is equal to or lower than the set level higher than the detection level, the first light emitting pulse is emitted, and the level of the light receiving pulse obtained by the light receiving unit exceeds the set level. And a selecting means for alternately projecting the first light projecting pulse and the second light projecting pulse. 3. A light projecting section, a light receiving section and a detecting section, wherein the light projecting section and the detecting section, and the detecting section and the light receiving section are connected by an optical fiber, and the light receiving pulse of the light receiving section is connected. In an optical fiber type photoelectric switch for detecting an object according to a level, a light projecting section projects a first light projecting pulse and a second light projecting pulse having a pulse width wider than the first light projecting pulse. And the level of the light receiving pulse obtained by the light receiving unit is below the detection level, the first light emitting pulse is emitted, and when the level of the light receiving pulse obtained by the light receiving unit exceeds the detection level, And a selecting unit for alternately selecting and projecting the first light projecting pulse and the second light projecting pulse. An optical fiber type photoelectric switch characterized in that 4. A light projecting section, a light receiving section and a detecting section, wherein the light projecting section and the detecting section, and the detecting section and the light receiving section are connected by an optical fiber, and a light receiving pulse obtained by the light receiving section is connected. In an optical fiber type photoelectric switch for detecting an object according to a level, a light projecting section projects a first light projecting pulse and a second light projecting pulse having a pulse width wider than the first light projecting pulse. And the level of the light receiving pulse obtained by the light receiving unit is equal to or lower than the set level higher than the detection level, the first light emitting pulse is emitted, and the level of the light receiving pulse obtained by the light receiving unit exceeds the set level. In this case, the state of emitting the first light emitting pulse and the state of alternately emitting the first light emitting pulse and the second light emitting pulse are alternately selected to emit light. An optical fiber type photoelectric conversion device characterized by comprising: Pitch. 5. A light emitting section, a light receiving section, and a detecting section, wherein the light projecting section and the detecting section, and the detecting section and the light receiving section are connected by an optical fiber, and a light receiving pulse of the light receiving section is connected. In an optical fiber type photoelectric switch for detecting an object according to a level, the light projecting unit responds to the level of the first light projecting pulse and the light receiving pulse obtained by the light receiving unit, when the level of the light receiving pulse is below the detection level, The pulse width is the first
Is narrower than the light projecting pulse of, and the level of the light receiving pulse is equal to or higher than the detection level, the light projecting means for projecting a third light projecting pulse having a pulse width wider than the first light projecting pulse; An optical fiber type photoelectric switch comprising: a light projecting pulse and a selecting means for alternately projecting the third light projecting pulse.