JPH05268043A - Photoelectric switch - Google Patents

Abstract

PURPOSE:To improve detection accuracy of an object to be detected by averaging the luminous intensity of a sensing light radiating from a light emitting section without complicated circuit configuration. CONSTITUTION:Part of a light radiating from an LED 36 is used as a sensing light (p) to detect an object to be detected. Furthermore, part of the remaining light is used for a monitor light (v), it is led to a reception section 49 of a transmission optical signal (o) and a luminous quantity monitor circuit 4 connecting to the reception section detects a luminous quantity. Then, a driver circuit 5 of the LED 36 is driven in response to its output signal to adjust the luminous quantity of the radiation light. An LED 58 for radiation of a transmission optical signal (o) may be used in common for the LED 36 for radiation of the sensing light (p) and the monitor light (v).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric switch for determining the presence or absence of an object by projecting light and detecting the presence or absence of the reflected light, and a photoelectric switch in which a plurality of such photoelectric switches are sequentially arranged. Regarding the system.

[0002]

2. Description of the Related Art A photoelectric switch is known as a means for detecting the presence or absence of an object moving on a conveyor line or the like. This is to determine the presence / absence of an object by projecting light onto the path of the object and detecting the presence / absence of reflected light from the moving object. In such a photoelectric switch, in order to reduce power consumption and prevent mutual interference, the projection light is pulsed so as to be projected intermittently (in this specification, the projection light is sensed light). That). Usually, a plurality of photoelectric switches are used to detect the presence or absence of an object. For example, in a conveyor line, multiple photoelectric switches are installed in one place such as a photoelectric switch that projects light from the lateral direction, a photoelectric switch that projects light from below, and a photoelectric switch that projects light from above to enable more accurate object detection. I have to. However, when a plurality of photoelectric switches are installed at one location and each photoelectric switch continuously projects light, each photoelectric switch may receive the sensing light projected by the other photoelectric switches.
This is called mutual interference as described above.In a photoelectric switch, light is emitted intermittently so that the light emission timing does not overlap with other photoelectric switches, and the reflected light from its own light emission and the light emission of other photoelectric switches cause Light received (interference light)
Means are provided for distinguishing between.

However, even in this case, if each photoelectric switch operates independently, the timing of the sensing light may overlap in two or more photoelectric switches, and mutual interference will occur. Conventionally, various techniques for preventing such mutual interference have been proposed, but all of them require complicated and expensive means, and the influence of mutual interference cannot be completely eliminated.

Therefore, the present applicant first sent the synchronous timing signal to a series of photoelectric switches in sequence, and the SST system in which the timing of the sensing light in these photoelectric switches was made different from each other in accordance with this synchronous timing signal. We proposed a photoelectric switch to call (Japanese Patent Application No. 3-2388
64). The photoelectric switch will be briefly described below with reference to FIG.

In the figure, this photoelectric switch basically comprises a detection light projecting section 33 for generating a sensing light p.
The detection light receiving section 37, the gate circuit 41, the integration circuit 43, the determination circuit 45, and the pulse generation circuit 30 are included, but in order to make the pulse generation circuit 30 externally synchronizable, a transmission optical signal that is a synchronization timing signal The o receiving unit 49 and the transmitting unit 54 are added.

First, the basic components will be described. The pulse generating circuit 30 generates a clock having a constant period and a clock generating circuit 31 which divides the clock (for example, divides by 16) to generate a pulse d having a constant period. And a frequency dividing circuit 32, which can be reset by an output pulse c of a one-shot circuit 53 of the receiving section 49 described later, so that the pulse d can be synchronized with this pulse c. The pulse d is supplied to the transmitter 54, the detection light projector 33, and the integration circuit 43.

The light projecting section 33 for detection includes the one-shot circuit 3
4, a switching transistor 35, and a light emitting element (LED) 36. One-shot circuit 34
Is triggered at the falling edge of the output pulse d of the frequency dividing circuit 32, and an "H" (high level) pulse e having a narrow constant pulse width is generated at each trigger. This pulse e turns on the transistor 35 for that pulse period. Therefore, when the transistor 35 is turned on, a drive current flows through the LED 36,
The sensing light is emitted from the LED 36 with the same cycle and the same duty ratio as the pulse e.

The detection light receiving portion 37 is composed of the photodiode 3
8, an amplifier 39, and a comparator 40. Upon receiving the light, the photodiode 38 generates a pulse having a pulse width equal to the light receiving period. This pulse is amplified by the amplifier 39 and supplied to the comparator 40 as the pulse f. The comparator 40 compares the level of the pulse f with a reference level and outputs a binarized pulse g of "L" (low level). Object nearby (not shown)
If so, the sensing light p from the LED 36 is reflected by this object and received by the photodiode 38,
A pulse f whose timing coincides with the output pulse e of the one-shot circuit 34 is obtained, but when another photoelectric switch is installed in close proximity, the sensing light p is also received by the photodiode 38 as interference light, and as a result, ,
A pulse f due to the interference light is also obtained. All of these pulses f are binarized by the comparator 40, and an "L" pulse g is obtained. This pulse g is supplied to the gate circuit 41 together with the output pulse e of the one-shot circuit 34.

The gate circuit 41 comprises a D-FF circuit 42, and its data input D is an output pulse g of the comparator 40 and its clock input CK is an output pulse e of the one-shot circuit 34. The D-FF circuit 42 samples and holds the level of the pulse g at the rising edge (front edge) of the "H" pulse e. As a result, the comparator 40
Only the pulse of the output pulse g that matches the timing of the pulse e is extracted and held by the D-FF circuit 42. Therefore, the pulse g whose timing does not match the pulse e is removed by the D-FF circuit 42. When the pulse g whose timing coincides with the pulse e is sequentially supplied at the cycle T of N pulse e, the D-FF 42 rises at the timing of the first pulse of the N pulses, and the pulse width is N · T. The "h" pulse h is output.

The integrating circuit 43 comprises a 4-bit shift register 44, for example. This shift register 4
4 uses the falling edge of the output pulse d of the frequency dividing circuit 32 as a clock CK, and the D-FF circuit 4 for each clock CK.
The output of 2 is taken in and sequentially shifted. So now,
If the D-FF circuit 42 outputs a pulse h of "H", this pulse h is taken in by the clock CK, the Q _A output of the D-FF circuit 44 becomes "H", and then the clock CK is supplied. Q _B , Q _C ,
It becomes "H" in the order of Q _D output. Therefore, four or more pulses g whose timing matches the pulse e are consecutively D-
4N from the D-FF circuit 42 taken into the FF circuit 42
When · T or more pulses h pulse width is output, Q _A to Q _D output of the shift register 44 becomes "H" at the same time.

The determination circuit 45 is the Q of the shift register 44.
And _A to Q _D AND gate 46 for receiving the output, also set pulse output of the NOR circuit 47, and AND gate 46 and inputs these Q _A to Q _D output, the output of the NOR circuit 47 as a reset pulse R / S-FF circuit 4
It consists of eight. AND gate 46 rises to all Q _A to Q _D output of the shift register 44 becomes "H", and generates a set pulse i of falling "H" and the those of even one "L", the set Pulse i
The R · S-FF circuit 48 is set at the rising edge of. NOR circuit 47, the shift register 44 Q _A to Q _D
A reset pulse j of “L” is generated which falls when even one of the outputs becomes “H” and rises when all of these outputs become “L”, and R is generated at the rising edge of this reset pulse j.
-The S-FF circuit 48 is reset. This gives R
The output of the S-FF circuit 48, that is, the output k of the determination circuit 45
Q _A to Q _D output of the shift register 44 is all time from when the "H" until all become "L""H"
Becomes

By the operation of each of the above parts, the pulse g whose timing matches the output pulse e of the one-shot circuit 34
Is sequentially obtained from the comparator 40 in the cycle of the pulse e, the output k of the determination circuit 45 becomes “H”, which means that the sensing light p from the LED 36 is reflected by the object and is received by the photodiode 38. That is, it means that an object exists. When the output k of the decision circuit 45 becomes "H", this indicates the existence of an object.

The presence / absence of an object is determined as described above. Next, the transmitting unit 54 and the receiving unit 49 for causing this photoelectric switch to function as the SST system will be described.

The transmitting section 54 includes a frequency dividing circuit 55, one-shot circuits 56 and 57, a switching transistor 58,
And LED 59. The output pulse d of the frequency dividing circuit 32 is frequency-divided by the frequency dividing circuit 55. Here, the frequency dividing circuit 55 divides the pulse d into four, and the timing of the falling edge of the output pulse 1 of the frequency dividing circuit 55 coincides with the falling edge of the pulse d.
The one-shot circuit 56 outputs the output pulse l of the frequency dividing circuit 55.
Triggered by the falling edge of the pulse, a "L" pulse m having a width ΔT determined by the time constant of the capacitor 56a and the resistor 56b is generated. The one-shot circuit 57 in the next stage is triggered by the rising edge (rear edge) of the pulse m, and the capacitor 57a
And a narrow "H" pulse n determined by the time constant of the resistor 57b is generated. Therefore, the generation timing of the pulse n is delayed by the time ΔT from the generation timing of the output pulse e of the one-shot circuit 34, and one pulse n is intermittent every four output pulses e. Will be generated. During the “H” period of the output pulse n, the transistor 58 is turned on, a drive current flows through the LED 59, and a pulsed optical signal o for transmission is generated from the LED 59 and transmitted to the photoelectric switch of the next stage (slave side). ..

The receiving section 49 is for receiving the transmission optical signal o outputted from the transmitting section 54 of the photoelectric switch (not shown) at the preceding stage (master side) having the same structure, and is for receiving. It comprises a photodiode 50, an amplifier 51, a comparator 52, and a one-shot circuit 53. The photodiode 38 receives the pulsed optical signal for transmission o transmitted from the transmitter 54 of the photoelectric switch on the master side, and generates a pulse having a pulse width equal to the light receiving period. This signal is amplified by the amplifier 51 and becomes the synchronization timing signal a, which is binarized by the comparator 52. The one-shot circuit 53 is triggered by the binarized sync timing signal to generate a "H" sync timing signal c having a narrow constant pulse width. As described above, the frequency dividing circuit 32 of the pulse generating circuit 30 is reset at the leading edge of the synchronization timing signal c. Here, the transmission optical signal o output from the LED 58 of the transmission unit 54 is delayed in timing from the sensing light p output from the LED 36 of the detection light projecting unit 33, and the synchronization timing signal a received by the coil 50 is The synchronization timing signal c output from the one-shot circuit 53 is delayed by the time ΔT from the emission timing of the sensing light p of the master-side photoelectric switch because it is formed by the transmitter 54 of the master-side photoelectric switch. That is, the front edge of the synchronization timing signal c coincides with the falling edge of the output pulse d of the frequency dividing circuit 32, and the output pulse e of the one-shot circuit 34 and thus the emission timing of the sensing light p from the LED 36 is the frequency dividing circuit. Since it coincides with the falling edge of the output pulse d of 32, the emission timing of the sensing light p from the LED 36 is delayed by the time ΔT from the emission timing of the sensing light p from the master side photoelectric switch.

A plurality of such photoelectric switches are sequentially arranged,
When an optical signal for transmitting the synchronization timing signal is sent to the slave side to operate, the sensing light p of each photoelectric switch is
The timings are sequentially shifted by the time ΔT in the order of arrangement, and the timings of the sensing lights p can be prevented from overlapping by appropriately selecting the time ΔT. In this way, in each photoelectric switch, the pulse whose output pulse g of the comparator 40 is coincident with the output pulse e of the one-shot circuit 34 is always the sensing light p from its own LED 36.
This is because the photodiode 38 receives only the reflected light of, and the determination result of the determination circuit 45 becomes very accurate except for mutual interference.

[0017]

By the way, the LED 36
The intensity of the sensing light emitted from the device is preferably constant, but actually changes every moment. When the sensing light intensity becomes a certain value or less, the light receiving unit 37 does not output the light reception signal g, and the determination circuit 45 easily determines that there is no detected object despite the detected object.
In order to prevent such inconvenience, it is possible to monitor the intensity of the sensing light emitted from the LED 36 and automatically increase the intensity of the light emitted from the LED 36 when the intensity of the sensing light is low. preferable.
However, if the above monitor circuit is simply added to the conventional circuit shown in FIG. 12, the circuit configuration becomes complicated and the cost of the device increases. An object of the present invention is to solve such a problem and to provide a photoelectric switch which is inexpensive and has high detection accuracy.

[0018]

In order to achieve the above object, the present invention provides an LE circuit in the conventional circuit shown in FIG.
The intensity of the monitor light emitted from D is detected and the L
A light amount monitor circuit that adjusts the intensity of the sensing light emitted from the ED is provided, and both the optical signal for transmission from the master side and its own monitoring light are received by the photodiode provided in the receiving section and transmitted. The photodiode that receives the optical signal for use and the photodiode for the sensing light are shared. Further, the synchronization timing signal output from the reception unit is delayed by a delay circuit, and the emission timing of the sensing light from the detection light projection unit and the transmission timing from the transmission light projection unit are based on the delayed synchronization timing signal. A pulse signal that determines the emission timing of the transmission optical signal is generated, and the emission timing of the sensing light and the transmission optical signal from the master side and the emission timing of the sensing light and the transmission optical signal from the slave side are set for a predetermined time. I tried to move it. In addition to the above-mentioned configuration, the transmission light projecting unit is omitted, and the sensing light projecting unit transmits the sensing light, the transmission optical signal, and the monitoring light from one light projecting unit. It is also used as a light projecting unit.

[0019]

When the light quantity monitor circuit is provided in the circuit, L
Since the sensing light of almost constant intensity can be emitted from the ED, the disadvantage that the reflected light from the detected object is not detected despite the detected object is improved,
The detection accuracy of the detected object can be improved. Further, if both the transmission optical signal from the master side and its own monitoring light are received by the photodiode provided in the receiving section, the photodiode for receiving the transmission optical signal and the monitoring photodiode are shared. Since the number of parts is reduced, the cost can be reduced.

When the synchronization timing signal output from the receiver is delayed and a pulse signal is generated from the pulse generation circuit based on this delayed synchronization timing signal, the sensing output from the photoelectric switch on the master side is detected. The emission timings of the light and the transmission optical signal and the emission timings of the sensing light and the transmission optical signal emitted from the photoelectric switch on the slave side can be shifted by the delay time. In addition, there is a possibility that the sensing light from the photoelectric switch on the master side (hereinafter, this is referred to as interference light) and the sensing light emitted by itself may enter the detection light receiving portion at a timing shifted by the delay time. However, the received signal corresponding to the interference light cannot pass through the gate circuit. Therefore, by appropriately selecting the delay time, mutual interference between photoelectric switches can be prevented.

Further, the transmitting light projecting unit is omitted, and the sensing light projecting unit and the transmitting light projecting unit are configured so that the sensing light, the transmitting light signal, and the monitor light are emitted from one light projecting unit. By sharing, the number of parts can be further reduced and the cost of the device can be reduced.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a circuit configuration example of a photoelectric switch according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the entire circuit configuration, FIG. 2 is a circuit diagram showing a configuration example of a light amount monitor circuit, and FIG. 3 is a waveform diagram showing waveforms of signals generated from respective parts of the apparatus of FIG.

In FIG. 1, reference numeral 1 is an electronic switch, reference numeral 2 is a detection circuit, reference numeral 3 is a delay circuit, reference numeral 4 is a light amount monitor circuit, reference numeral 5 is an LED driver circuit, and others correspond to FIG. 12 described above. The same symbol is displayed in the part to be performed. As is apparent from this figure, the photoelectric switch of the present embodiment is different from the photoelectric switch of the conventional example shown in FIG. 12 in that the electronic switch 1 and the detection circuit 2 are provided between the amplifier 51 and the comparator 52 of the receiver 49. Is provided, the light amount monitor circuit 4 for sensing light is provided at one switching contact of the electronic switch 1, and the detection light projecting unit 33 is provided.
Is provided with a driver circuit 5 for the LED 36 adjusted by the light amount monitor circuit 4, and a delay circuit 3 is provided between the receiving section 49 and the pulse generating circuit 30.

The contacts of the electronic switch 1 are alternately switched by the output pulse d from the pulse generating circuit 30,
The light reception signal a of the photodiode 50 amplified by the amplifier 51 is supplied to the detection circuit 2 side or the light amount monitor circuit 4 side. The delay circuit 3 sets the emission timing of the sensing light and the transmission optical signal emitted from the master side photoelectric switch and the emission timing of the sensing light and the transmission optical signal emitted from the next stage photoelectric switch for a predetermined time. It has a function of shifting and constructing the SST type photoelectric switch system. The light amount monitor circuit 4 includes an amplifier 6 and
It comprises a peak hold circuit 7 and a low-pass filter 8. The peak hold circuit 7 has an attenuation characteristic,
The time constant used is about 1 to 100 times the clock cycle. A specific configuration example of the light amount monitor circuit 4 is as shown in FIG.

The operation of the circuit shown in FIG. 1 will be described below with reference to FIG. As shown in FIG. 1, one photoelectric switch S ₁
In the case where the other photoelectric switch S ₂ of the same type is installed on the master side, when the transmission optical signal o ₂ is emitted from the light projecting unit 33 of the master side photoelectric switch S ₂ , the transmission optical signal S ₂ is transmitted. O ₂ is received by the photodiode 50 provided in the receiver 49 of the photoelectric switch S ₁ on the slave side, and the photodiode 50 outputs a pulsed light reception signal according to the amount of received light. The received light signal is amplified by the amplifier 51 and becomes the synchronization timing signal a.

When the contact of the electronic switch 1 is switched to the detection circuit 2 side, this synchronization timing signal a
Flows to the detection circuit 2, the comparator 51, and the one-shot circuit 53, and is output from the one-shot circuit 53 as a synchronization timing signal c having a narrow constant pulse width. The delay circuit 2 outputs a delay signal q obtained by delaying the synchronization timing signal c by a time Δd. Delay time Δd
Is set to a value that can prevent the above mutual interference.

From the pulse generation circuit 30, the pulse d synchronized with the delay signal q is obtained as described above. This pulse d is applied to the contact switching section of the electronic switch 1 and the transmitting light projecting section 5
4, the light projecting unit 33 for detection, and the gate circuit 41, respectively. Then, as described above, in synchronization with the pulse d supplied from the pulse generation circuit 30, the sensing light p and the monitoring light v are transmitted from the detection light projecting unit 33 to the transmission light projecting unit 5.
The optical signals for transmission o ₁ are emitted from the optical fiber 4 at the same timing. Along with this, the contact of the electronic switch 1 is switched to the light quantity monitor circuit 4 side by the pulse d supplied from the pulse generation circuit 30.

When the object to be detected is present at a predetermined position, the sensing light p is reflected by the object to be detected, and the light receiving section 37 for detection is used.
And the monitor light v emitted from the detection light projecting unit 33 is received by the photodiode 50 provided in the receiving unit 49 of the photoelectric switch S ₁ of its own and is received by the amplifier 5
1 is output as a monitor signal r. The output timing of the monitor signal r is delayed from the output timing of the synchronization timing signal a by a delay time Δd. The monitor signal r is amplified by the amplifier 6 of the light quantity monitor circuit 4, peak-detected by the peak hold circuit 7 to become the peak detection signal s, the high-frequency component thereof is removed by the low-pass filter 8, and sinusoidal amplitude control is performed. The light amount monitor circuit 4 outputs the signal t.

The driver circuit 5 is servo-controlled by the amplitude control signal t, and when the amplitude of the amplitude control signal t is large, the light amount of the sensing light p emitted from the LED 36 is decreased so that the amplitude of the amplitude control signal t is reduced. L if small
The light amount of the sensing light p emitted from the ED 36 is increased. As a result, as shown in FIG.
The peak value of the sensing light p is adjusted every moment so that the intensity of the sensing light detected at 7 is always almost constant.

It is considered that only the sensing light p reflected by the object to be detected is normally incident on the detection light receiving section 37. However, depending on the arrangement of a plurality of photoelectric switches, the photoelectric switch on the master side or the slave side may be used. In some cases, the interference light u from is incident. However, the gate circuit 41
As described above, the output pulse e of the one-shot circuit 34
And the detection pulse g of the detection light receiving section 37 are input and only the pulse whose timing coincides with the output pulse e of the one-shot circuit 34 is extracted from the detection pulse g.
Are removed by this gate circuit 41. For this reason,
The determination circuit 45 does not malfunction due to the interference light u. For example, as shown in FIG. 3, when the sensing light p reflected by the object to be detected enters the detection light receiving unit 37 three times in a row, In the determination circuit 45 that determines that there is a detected object, the determination signal k that the detected object is present is output at the third pulse regardless of whether the interference light u is incident.

Next, an example of the internal structure of the photoelectric switch according to the first embodiment will be described with reference to FIGS.
FIG. 4 is a side view of the photoelectric switch, FIG. 5 is a cross-sectional view of the photoelectric switch as seen from a plane direction, and FIG. 6 is an explanatory diagram of an LED.
4 and 5, 11 is a case, 12 is a cover plate, and 1
3 is an optical fiber for projecting light, 14 is an optical fiber for receiving light, 15
Is a circuit board, 36 is an LED provided in the detection light projecting unit,
50 is a photodiode provided in the receiver, 16 is an LE
Reference numeral 17 denotes a first mirror for guiding the monitoring light v from D36 to the photodiode 50, and reference numeral 17 denotes a second mirror for guiding the transmission optical signal from the master side photoelectric switch to the photodiode 50.

The case 11 is formed in a rectangular box shape having no top plate. Front plate 11a of this case 11
Includes a light projecting optical fiber 13 and a light receiving optical fiber 1.
4 is connected. The light projecting optical fiber 13 is for guiding the sensing light from the LED 36 built in the case 11 to irradiate an object to be detected (not shown),
The light receiving optical fiber 14 guides the reflected light from the object to be detected to the photodiode 38 incorporated in the case 11. The left and right side plates 11b and 11c of the case 1 are formed in parallel and in a planar shape, and a transmission light projecting window 18 and a transmission light receiving window 19 are opened at positions facing each other.

The circuit board 15 is mounted with the circuit of FIG. 1 and is formed in a size that can be housed in the case 11. The cover plate 12 is formed in a flat plate shape having a size capable of sealing the opening of the case 11, and after the circuit board 15 is housed in the case 11, the cover 12 is detachably attached to the opening of the case 11. ..

By housing the circuit board 15 in the case 11, the LED 59 of the transmitting light projecting portion 54 is disposed inside the transmitting light projecting window 18, and the photodiode 50 is disposed inside the transmitting light receiving window 19. The LE of the detection light projecting unit 33 is arranged at a portion facing the inner end of the light receiving optical fiber 14.
D36 is arranged. Further, the first mirror 16 is arranged between the side surface of the LED 36 and the photodiode 50, and the inside of the light receiving window 19 for transmission and the photodiode 5 are arranged.
A second mirror 17 is arranged between the second mirror 17 and 0. LED3
6, the light emitting element 21 is connected to the two lead wires 22a and 22b as shown in FIG.
The light is emitted not only in the front direction of the transparent resin 23 but also in the side direction of the transparent resin 23. The ratio of the intensity of the light emitted from the front direction to the intensity of the light emitted from the side direction can be appropriately adjusted by changing the shape of the transparent resin 23. Therefore, the light emitted from the front direction of the transparent resin 23 is incident on the light projecting optical fiber 13, and the light emitted from the side direction is incident on the photodiode 50 via the first mirror 16, so that one LED 36 is emitted. The sensing light p and the monitoring light v can be emitted, and the single photodiode 50 can detect the transmission optical signal o and the monitoring light v.

As described above, since the photoelectric switch of this embodiment is provided with the light quantity monitor circuit 4 for monitoring and adjusting the intensity of the sensing light p emitted from the detection light projecting unit 33 in the circuit, the detection light projection circuit 4 is provided. Sensing light p emitted from the light section 33
Can be made substantially constant, and the detection accuracy of the detected object can be improved. Further, since the monitoring light v is also detected by the receiving section 49 of the transmission optical signal o, the circuit configuration is not complicated and the cost can be reduced.

Next, another example of the internal structure of the photoelectric switch according to the first embodiment will be described with reference to FIGS. 7 and 8. FIG. 7 is an exploded perspective view of the photoelectric switch, and FIG. 8 is a sectional view of the photoelectric switch as seen from the front side. In these figures, 20 is a light mixer, 38 is a photodiode provided in the detection light-receiving section 37, and the other parts corresponding to those in FIG. 4 or FIG. There is.

The light mixer 20 has a mirror surface 20a and a half mirror surface 20b, and these mirror surfaces 20a.
And a surface forming 45 degrees with respect to the half mirror surface 20b is set so as to face the light receiving window 19 for transmission. This light mixer 2
On the lower surface of 0, the photodiode 50 provided in the receiver 49 is set. The LED 36 is set such that its front surface portion faces the light projecting optical fiber 13 and its side surface portion faces the half mirror surface 20b of the light mixer 20. Photodiode 38 provided in the detection light receiving section 37
Is set so as to face the inner end of the light-receiving optical fiber 14.

In the case of this example, the monitor light v emitted from the side surface portion of the LED 36 is incident on the photodiode 50 via the half mirror surface 20b of the light mixer 20, and is also transmitted from the light receiving window 19 for transmission. The incident transmission optical signal o is incident on the photodiode 50 via the mirror surface 20a and the half mirror surface 20b of the light mixer 20. Therefore, the same effect as in the case of the above example can be obtained.

The photoelectric switch according to the second embodiment will be described below with reference to FIGS. 9 is a block diagram showing a circuit configuration, FIG. 10 is a cross-sectional view showing an example of the internal configuration as seen from a plane direction, and FIG. 11 is a cross-sectional view showing another example of the internal configuration as seen from a plane direction.

As shown in FIG. 9, in the photoelectric switch of the second embodiment, the transmitting light projecting portion 54 of the photoelectric switch according to the first embodiment shown in FIG. 1 is omitted and the detecting light projecting portion 33 is omitted. LE
It is characterized in that the sensing light p, the transmission optical signal o, and the monitoring light v are emitted from D36. That is, as described above, light is emitted from the LED 36 not only in the front direction but also in the side direction. Therefore, these lights are extracted separately and used as the sensing light p, the transmission optical signal o, and the monitoring light v, respectively. By doing the first
The same operation as that of the embodiment can be performed.

In FIG. 10, 11 is a case, 18 is a transmitting light projecting window, 19 is a transmitting light receiving window, 13 is a light projecting optical fiber, 36 is an LED provided in the light projecting section 33, and 50 is a receiving section. Photodiode provided in 49, 16 LED3
The first to guide the monitoring light from 6 to the photodiode 50
, 17 is a second mirror for guiding the transmission optical signal incident from the transmission light receiving window 19 to the photodiode 50, 25
Indicates a light guide body for guiding the transmission optical signal from the LED 36 to the transmission light projecting window 18.

In this example, the inner end of the light projecting optical fiber 13 and the front portion of the LED 36 are arranged so as to face each other, and
The inner end of the light guide 25 and the first mirror 16 are arranged so as to face the side surface portion of D36. In addition, the transmission light receiving window 1
A second mirror 17 is arranged inside 9 and faces the first and second mirrors 16 and 17 and the photodiode 5
0 is placed. The other parts are the same as those in FIG. 5, and therefore the description thereof is omitted to avoid duplication.

In the photoelectric switch of this example, the light emitted from the front surface of the LED 36 is incident on the light projecting optical fiber 13 as the sensing light p, and a part of the light emitted from the side surface is guided as the transmission optical signal o. By emitting a part of the light emitted from the transmission light projecting window 18 through the light body 25 and in the opposite direction to the transmission light projecting window 18 through the first mirror 16 to the photodiode 50, The same operation as in the case of the first embodiment can be performed.

As described above, in the photoelectric switch of this example, the circuit for emitting the transmission optical signal o is omitted, so that the photoelectric switch can be implemented at a lower cost.

Next, another example of the internal structure of the photoelectric switch according to the second embodiment will be described with reference to FIG. The photoelectric switch of this example includes the front portion of the LED 36 and the light guide 2.
An optical branching device 26 is arranged between the inner end of the LED 5, and the light emitted from the front portion of the LED 36 is branched by the optical branching device 26.
One of them is used as the sensing light p and the optical fiber 13 for projecting light is used.
And the other is emitted as a transmission optical signal o from the transmission light projecting window 18 via the light guide 25. In FIG. 11, reference numeral 26 denotes an optical branching device, and other parts corresponding to those in FIG.
The same code is displayed.

The optical branching device 26 is a transparent member 26 having a triangular cross section.
a and 26b are joined together via a multilayer film 27, and the intensity of light emitted from the two light emitting surfaces 28a and 28b can be changed by changing the film thickness, laminated structure, material, etc. of the multilayer film 27. The ratio of can be set almost freely. Since the photoelectric switches are arranged close to each other, the transmission optical signal o may be weak. Therefore, regarding the optical branching device 26 applied to the photoelectric switch of this example, the first light emitting surface is 28a and the intensity of light emitted from 28a and the second light emission surface 28b.
It is possible to use a light having an intensity ratio of about 99: 1.

This optical branching device 26 has a first light emitting surface 28.
It is set in the photoelectric switch by a being opposed to the inner end of the light projecting optical fiber 13 and the second light emission surface 28b being opposed to the inner end of the light guide 25. Others are the same as those of the photoelectric switch of FIG. 10, and thus description thereof will be omitted.

In the photoelectric switch of this example, the light emitted from the first light emitting surface 28a of the optical branching device 26 is incident on the light projecting optical fiber 13 as the sensing light p, and the optical branching device 26 is also used.
Of the light emitted from the second light emission surface 28b of the LED 36 is emitted as the transmission optical signal o from the transmission light projecting window 18 via the light guide 25, and a part of the light emitted from the side surface portion of the LED 36 is monitored. When the incident light v is incident on the photodiode 50 via the first mirror 16, the same operation as in the case of the first embodiment can be performed.

[0049]

As described above, according to the present invention,
Since the light amount monitor circuit for monitoring the intensity of the light emitted from the LED and keeping it constant is provided, the detection accuracy of the detected object can be improved. Further, since the photodiode for receiving the monitoring light emitted from the LED is also used as the photodiode for receiving the transmission optical signal, the circuit is not complicated and can be implemented at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of a photoelectric switch according to a first embodiment.

FIG. 2 is a circuit diagram showing a configuration example of a light amount monitor circuit.

3 is a waveform chart of a signal output from each unit of the apparatus of FIG.

FIG. 4 is a side view of a photoelectric switch.

FIG. 5 is a cross-sectional view showing a first example of the internal configuration of the photoelectric switch as seen from the plane direction.

FIG. 6 is an explanatory diagram of an LED.

FIG. 7 is an exploded perspective view of a photoelectric switch.

FIG. 8 is a cross-sectional view showing a second example of the internal configuration of the photoelectric switch as seen from the front side.

FIG. 9 is a block diagram showing a circuit configuration of a photoelectric switch according to the first embodiment.

FIG. 10 is a cross-sectional view showing a third example of the internal configuration of the photoelectric switch as seen from the plane direction.

FIG. 11 is a cross-sectional view showing a fourth example of the internal configuration of the photoelectric switch as seen from the plane direction.

FIG. 12 is a circuit diagram of a photoelectric switch according to a conventional example.

[Description of symbols] 1 electronic switch 2 detection circuit 3 delay circuit 4 light intensity monitor circuit 5 LED driver circuit 30 pulse generation circuit 33 light emitting unit 37 detection light receiving unit 49 transmission optical signal receiving unit o transmission optical signal p Sensing light v Monitor light

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ikuro Ouchi 1-13-10 Nishi-Odori, Hanamaki-shi, Iwate Shanpol 203

Claims (2)

[Claims] 1. A receiving unit that receives a transmission optical signal from a master side and its own monitoring light, generates a synchronization timing signal from the transmission optical signal and outputs the synchronization timing signal, and delays the synchronization timing signal. A delay circuit, a pulse generation circuit for generating a pulse synchronized with the delayed synchronization timing signal, and a detection projection unit for emitting sensing light to an object to be detected in synchronization with an output pulse of the pulse generation circuit. , A transmission light projecting unit for emitting a transmission light signal to the slave side in synchronization with the output pulse of the pulse generation circuit, and self-sensing from a signal corresponding to the monitoring light detected by the receiving unit. A light amount monitor circuit that detects the light intensity and adjusts the intensity of the sensing light emitted from the detection light projecting unit, and a detection light receiving unit that receives the sensing light reflected by the object to be detected, A gate unit that extracts a signal synchronized with the sensing light from an output signal of the detection light receiving unit, and a determination unit that determines the presence or absence of an object to be detected based on the output signal of the gate unit. And photoelectric switch. 2. A receiving unit that receives a transmission optical signal from the master side and its own monitoring light, generates a synchronization timing signal from the transmission optical signal and outputs the synchronization timing signal, and delays the synchronization timing signal. A delay circuit, a pulse generation circuit for generating a pulse synchronized with the delayed synchronization timing signal, and a sensing light for an object to be detected and an optical signal for transmission to a slave side in synchronization with an output pulse of the pulse generation circuit. And a light projecting unit that emits monitoring light to the receiving unit, and detects the intensity of its own sensing light from a signal corresponding to the monitoring light detected by the receiving unit, and the detecting light projecting unit A light amount monitor circuit that adjusts the intensity of the sensing light emitted from the sensor, a detection light receiving unit that receives the sensing light reflected by the object to be detected, and the sensing signal from the output signal of the detection light receiving unit. A photoelectric switch comprising: a gate unit that extracts a signal synchronized with light; and a determination unit that determines the presence or absence of an object to be detected based on an output signal of the gate unit.