JP2002043921A - Photoelectric sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectrie sensor that can increase a response speed without deteriorating its light emitting element. SOLUTION: The photoelectric sensor comprises a light projection means 14 and a light receiving means 23. The light projections means 14 emits a synthesis light with a half period of a reference pulse light having a prescribed period by emitting the reference pulse lights with a prescribed period from LED chips 3a, 3b and whose phases are shifted each other and synthesizing the phase- shifted reference pulses. Thus, the period of the synthesis light can be decreased more than the period of each emission light from each of the LED chips 3a, 3b. Then a light receiving means 8 detects the synthesis light on the basis of emission timing of the reference pulse lights to discriminate the presence of an object 100 to be detected on an optical path 24 formed between the light projection section 7 and the light receiving means 8 and provides an output of a discriminated result as a detection signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric sensor for detecting the presence or absence of an object to be detected by receiving light emitted from light projecting means by light receiving means.

[0002]

2. Description of the Related Art Conventionally, in a production line for mass-producing predetermined objects, the production management of the predetermined objects is performed by counting the number of produced predetermined objects (objects to be detected). Generally, there is a method in which the presence or absence of an object flowing on a line is detected by a photoelectric sensor, and the number of objects to be detected is counted by a control center for production line management based on the detected signal. Has been adopted. In this photoelectric sensor, for example, a light emitter and a light receiver are installed so as to sandwich a line through which an object flows, and an optical path is formed so that light emitted from the light emitter is received by the light receiver, and an object flowing through the line is formed. By using the fact that the emitted light is blocked by the object when passing through the optical path, the detection circuit detects whether or not the object on the optical path has passed.

[0003] In such a photoelectric sensor, a pulse light having a predetermined period is emitted from an LED provided in a light projector,
There is a configuration in which a photodetector detects a light receiving signal (pulse signal) obtained by photoelectrically converting the pulse light, and a detection circuit detects presence / absence of an object to be detected based on the pulse signal. In this photoelectric sensor, the detection circuit always detects (time-integrates) a pulse signal based on a predetermined period of the pulse light, and if the pulse signal is not continuously detected a predetermined number of times, the detection signal is detected on the optical path. It is determined that there is an object, and a detection signal indicating "there is an object to be detected" is output to the control center. In cases other than the above, it is determined that there is no object to be detected on the optical path, and a detection signal indicating "no object to be detected" is output. In such a photoelectric sensor, the detection light can be reduced by making the light emitted from the light emitter into pulse light and performing time integration of the pulse signal by the detector, so that the presence or absence of the object to be detected on the optical path can be reduced. Detection accuracy can be improved.

[0004] Meanwhile, in the production line, there is a tendency to increase the amount of the detected object per hour in order to increase the production efficiency. Therefore, the moving speed of the detection object flowing in the line is also increased, and accordingly, the detection speed (response speed) of the photoelectric sensor needs to be increased. In order to increase the response speed of the photoelectric sensor in response to such a request, the period of the pulse light may be shortened.

[0005]

However, the LED has a maximum rating which is the maximum amount of power supplied per unit time, and if the period of the pulsed light is shortened, the power supplied to the LED per unit time increases. In addition, when a power amount exceeding the maximum rating is applied to the LED, there is a problem that deterioration such as shortening of the life of the LED occurs. Therefore, in the conventional photoelectric sensor, the response speed cannot be increased without deteriorating the LED. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a photoelectric sensor capable of increasing a response speed without deteriorating a light emitting element.

[0006]

A photoelectric sensor according to claim 1, wherein said photoelectric sensor emits projection light from a light projecting means and receives said projection light emitted from said light projecting means by a light receiving means. The light projecting unit is configured to emit a combined light obtained by combining light emitted from a plurality of light emitting elements that emit light having substantially the same wavelength, and the light receiving unit is configured to emit light emitted from the plurality of light emitting elements. And receiving light having substantially the same wavelength as the light from the light emitting element based on the emission timing. According to such a configuration, the light emitting means is
By emitting light from a plurality of light emitting elements and emitting a combined light having a predetermined light amount level and a pulse width,
Since the cycle of the combined light can be shorter than the cycle of the similar pulsed light emitted from one light emitting element, the detection speed of the object to be detected (compared to a conventional photoelectric sensor composed of one light emitting element) ( Response speed).
This makes it possible to prevent the light emitting element from deteriorating while increasing the response speed of the photoelectric sensor.

According to a second aspect of the present invention, in the photoelectric sensor, the light projecting means is configured to make optical axes of the plurality of light emitting elements substantially coincide with each other. According to such a configuration, it is not necessary to adjust the position where the emitted lights from the plurality of light emitting elements are combined in accordance with the position of the object to be detected, so that the installation work of the light projecting means and the light receiving means is simplified. .

According to a third aspect of the present invention, in the photoelectric sensor, the light projecting means shifts the energization phase of the plurality of light emitting elements by a reciprocal cycle of the number of the light emitting elements so as to shift the cycle of the combined light to the respective light emission. It is characterized in that the period is shorter than the period of light emitted from the element. According to such a configuration, the power supply phases of the plurality of light-emitting elements are shifted from each other, and the cycle of the combined light is shorter than the cycle of the light emitted from each light-emitting element, so that a predetermined light amount level and a pulse width are obtained. Since the combined light can be emitted, the cycle of the combined light can be shorter than the cycle of the same pulsed light emitted from one light emitting element.

According to a fourth aspect of the present invention, in the photoelectric sensor, the light projecting means shortens an energizing cycle in a state where the energizing amount to the plurality of light emitting elements is reduced, thereby reducing the light intensity level of the combined light to the respective light emission levels. It is characterized in that the light intensity level is higher than the level of light from the element. According to such a configuration, the power supply cycle is shortened in a state where the power supply amounts of the plurality of light emitting elements are reduced, and the light amount level of the composite light is increased, so that the composite light having a predetermined light amount level and a pulse width is emitted. Therefore, the cycle of the combined light can be made shorter than the cycle of the same pulsed light emitted from one light emitting element.

According to a fifth aspect of the present invention, in the photoelectric sensor according to the fifth aspect, the light emitting means shifts the energization phases by the energization width in a state where the energization width and the energization cycle for the plurality of light emitting elements are shortened, and thereby the pulse width of the combined light. Is made longer than the pulse width of the light emitted from each of the light emitting elements. According to such a configuration, the energization phases are shifted from each other by the energization width in a state where the energization width and the energization cycle for the plurality of light emitting elements are shortened, and the pulse width of the combined light is set to be greater than the pulse width of the light emitted from each light emitting element. Also, by increasing the length of light, a combined light having a predetermined light amount level and a pulse width can be emitted. Therefore, the cycle of the combined light can be made shorter than the cycle of the same pulse light emitted from one light emitting element. it can.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] Hereinafter, a first embodiment in which the present invention is applied to a transmission type photoelectric sensor will be described.
This will be described with reference to FIGS. The photoelectric sensor 1 according to the present embodiment operates by being supplied with power from a power supply circuit (not shown). First, FIG. 1 shows a production line in which production and management of a predetermined object (object to be detected) 100 (see FIG. 2) is controlled by a control center for production line management (not shown), on a line 101 (see FIG. 2). FIG. 2 is a block diagram showing a configuration of a photoelectric sensor 1 installed near a line 101 to detect the presence or absence of an object moving at a predetermined speed at a predetermined position.

Although the details will be described later, the timing control circuit 2 uses the same light emitting element, an LED, that emits light of the same wavelength.
LED drive signals S1 and S2 for emitting pulsed light as emitted light from the chips 3a and 3b are generated. Further, a synchronization signal for synchronizing the emission timing of the pulse light emitted from the LED chips 3a and 3b with the detection timing of the pulse signal detected by the detection circuit 4 is generated. Then, the synchronization signal is output to the detection circuit 4, and the LED drive signals S1 and S2 are output to the light emitting circuits 5 and 6, which will be described later.

In the light emitting circuits 5 and 6, the LED driving signal S
When receiving the LED drive signals S1 and S2, drive currents for driving the LED chips 3a and 3b are generated in accordance with the pulse widths, periods and phases of the LED drive signals S1 and S2.
The LED chips 3a and 3b have a maximum rating, which is the amount of power that can be supplied per unit time, and are driven by the driving current.
Is set in advance so as to be less than the maximum rating. Then, the generated drive current is supplied to the LED chip 3
a and 3b.

FIG. 2 shows a line 10 perpendicular to the flowing direction of the object 100 on the line 101.
1 schematically shows a configuration of a light projecting unit 7 and a light receiving unit 8 which are installed so as to face each other with the light receiving unit 1 interposed therebetween. In FIG. 2, the light projecting unit 7 includes an LED 3 on which two LED chips 3a and 3b are mounted, and an LED 3 on which the LED chips 3a and 3b are mounted.
And a light projecting lens 9 for condensing the pulse light emitted from the LED (the LED 3 is emphasized in the figure). The LED 3 is mounted so that two LED chips 3a and 3b are adjacent to each other on one base 10, and a transparent resin 1 is mounted on the base 10 and the LED chips 3a and 3b.
1 is covered and formed. Since these two LED chips 3a and 3b are mounted very close,
The pulse light emitted from each of the LED chips 3a and 3b is combined, passes through the light projecting lens 9, and is emitted as combined light having substantially the same optical axis.

The LED 3 is provided with two drive leads 12a and 12b for inputting a drive current and one ground lead 13.
2a and 12b are connected to the light emitting circuits 5 and 6, respectively, and the ground lead 13 is connected to the ground line. The timing control circuit 2, the light emitting circuits 5 and 6, and the light emitting section 7 constitute a light emitting means 14 (see FIG. 1).

The light receiving section 8 comprises a light receiving lens 15 for condensing the combined light emitted from the light projecting section 7 and a light receiving element 16 for detecting the condensed light (FIG. 2). Indicates the light receiving element 16). This light receiving element 16
A phototransistor 18 is mounted on the base 17, and a transparent resin 19 is formed on the base 17 and the phototransistor 18 so as to be covered. The light receiving element 16 has a signal lead 2 for outputting a light receiving signal (pulse signal) photoelectrically converted by the phototransistor 18.
0 and a ground lead 21 are provided, and the signal lead 20 is connected to a light receiving circuit 22 (see FIG. 1) described later.
The grounding lead 21 is connected to a ground line.

Returning to FIG. 1, the light receiving circuit 22 amplifies this pulse signal to a predetermined amplitude level and outputs it to the detection circuit 4. The light receiving section 8, the light receiving circuit 22, and the detecting circuit 4
Constitute light receiving means 23. Further, an optical path 24 is formed between the light projecting unit 7 and the light receiving unit 8 until the combined light emitted from the light projecting unit 7 is received by the light receiving unit 8.
The presence or absence of the detection target 100 is detected based on whether or not 4 is blocked.

As shown in FIG. 1, the detection circuit 4 receives the synchronization signal output from the timing control circuit 2 and constantly receives the synchronization signal from the LED chips 3a and 3b based on the emission timing of the pulse light from the LED chips 3a and 3b. Detection is performed. Then, the detection signal is time-integrated for a predetermined number of consecutive times, and when the detection signal is continuously at a "low level" for a predetermined number of times (when no pulse signal is detected), the detection signal is placed on the optical path 24 (see FIG. 2). Object to be detected 100 (see FIG. 2)
Is determined to exist, and in other cases, the optical path 24
It is determined that there is no detection object 100 above. The result of this determination is output as a detection signal to the control center via a signal output line 25 provided in the detection circuit 4. The light emitting means 14 and the light receiving means 23 make the photoelectric sensor 1
Is configured.

Next, the operation of the photoelectric sensor 1 will be described with reference to FIG.
This will be described with reference to FIG. FIG. 3 shows a timing chart of signals output from the respective parts of the photoelectric sensor 1 and pulse light emitted from the light projecting unit 14.

In the photoelectric sensor 1, the timing control circuit 2 first generates a synchronization signal shown in FIG. 3A, an LED drive signal S1 shown in FIG. 3B, and an LED drive signal S2 shown in FIG. The synchronization signal is a pulse signal having a predetermined period and a predetermined pulse width, and is used as a detection timing of the detection circuit 4. The detection speed (response speed) of the photoelectric sensor 1 is determined by the cycle of the synchronization signal. The LED drive signals S1 and S2 have a cycle twice that of the synchronization signal, have the same pulse width, and are shifted in phase by a reciprocal cycle of 2, which is the number of the LED chips 3a and 3b. Then, the synchronization signal is output to the detection circuit 4, and the LED drive signals S1 and S2 are output to the light emitting circuits 5 and 6.

In the light emitting circuits 5 and 6, the LED driving signal S
Based on 1 and S2, a drive current for driving the LED chips 3a and 3b is generated. Specifically, the pulse width, the power cycle, and the power phase of these drive currents are determined by the LED drive signals S1 and S2.
, The pulse width, the period and the phase. The current amplitude, which is the amount of the drive current, is determined by the LED chip 3a.
And 3b have a predetermined value such that the amount of energized power is less than the maximum rating. The respective drive signals generated in this way differ only in phase and have the same pulse width, cycle, and current amplitude. Then, the generated drive current is LE
D3 is output to the driving leads 12a and 12b.

From the LED chips 3a and 3b, based on the driving current, the basic pulse light as the emitted light as shown in FIGS. 3D and 3E is emitted. These basic pulse lights have a light intensity level (light intensity) corresponding to the current amplitude of the drive current.
The period, pulse width and phase are ideally equal to those of the LED drive signals S1 and S2. Therefore, the respective basic pulse lights differ only in phase, and have substantially the same light amount level, cycle, and pulse width. Then, the respective basic pulse lights are synthesized and condensed by the light projecting lens 9 to be emitted as synthesized light having substantially the same optical axis. As shown in FIG. 3 (f), the combined light has the same pulse width as the basic pulse light and a cycle of 1/2 of the basic pulse light emitted from the LED chips 3a and 3b. Times (the reciprocal multiple of 2)
The phase and the pulse width are equal and the phase is synchronized with the synchronization signal. Then, the combined light passes through the optical path 24 and is received by the light receiving section 8.

In FIG. 3, a period from time A to time B (AB period) is a state in which the object 100 is not on the optical path 24. Then, at time B, the optical path 24
The object 100 appears in the optical path 24 during the period from time B to time C (BC period). Therefore, in the AB period, the combined light is transmitted to the light receiving section 8.
And the light-receiving signal photoelectrically converted by the light-receiving unit 8 is shown in FIG.
A pulse signal as shown in the AB period of (g) is obtained. In the BC period, the combined light is blocked by the detection target 100 and does not reach the light receiving unit 8, so that the light receiving signal is as shown in FIG.
It becomes a “low level” as shown in the BC period of (g). The light receiving signal is amplified by the light receiving circuit 22 to a predetermined amplitude level and output to the detection circuit 4.

In the detection circuit 4, in accordance with the rising timing of the synchronization signal received from the timing control circuit 2,
The detection of the light receiving signal is always performed. Then, the detection signal is repeatedly time-integrated so as to be a predetermined number of continuous times (for example, four times). In FIG. 3, for example, time A
In the time integration performed from the point of time, the 'high level' is detected four times in succession, so that at the time X when the fourth detection is performed, it is determined that the object 100 is not present in the optical path 24, The output state of the “low level” detection signal indicating that there is no object 100 from the signal output line 25 is continued. In addition, for example, in the time integration performed from the time Y, the “low level” is detected four times in succession. Therefore, the object 100 is present in the optical path 24 at the time Z when the fourth detection is performed. Is determined, and the object 1 is detected.
A “high level” detection signal indicating that there is 00 is output.

The detection circuit 4 does not judge that the object 100 is present on the optical path 24 unless the low level is detected four times in succession.
As a result, detection errors are reduced, and the detection accuracy of the presence / absence of the object 100 in the optical path 24 is increased. And always,
The detection of the presence or absence of the detection target 100 is performed, and FIG.
A detection signal as shown in (h) is output to the control center.

As described above, in the present embodiment, in the light projecting means 14, the energization phase for each of the LED chips 3a and 3b is shifted by the reciprocal cycle of 2, which is the number of LED chips, and the cycle of the combined light is changed for each LED chip. By making the light shorter than that of the basic pulse light emitted from 3a and 3b, it is possible to emit a combined light having a predetermined light amount level and a pulse width. Therefore, the cycle of the combined light is emitted from one light emitting element. It is possible to shorten the period of a similar pulsed light, and to increase the detection speed (response speed) of the detection target 100 as compared with, for example, a photoelectric sensor including one LED chip. This makes it possible to prevent the LED 3 from deteriorating while increasing the response speed of the photoelectric sensor 1.

Further, since the light projecting means 14 is configured to emit the combined light, it is necessary to adjust the position where the basic pulse lights from the two LED chips 3a and 3b are combined in accordance with the position of the object 100 to be detected. Therefore, the work of installing the light projecting unit 7 and the light receiving unit 8 is simplified. Further, within a range where the light receiving unit 23 can detect the combined light, the light projecting unit 7 and the light receiving unit 8
Can be set arbitrarily.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIG. Since the second embodiment is a modification of the process of generating the combined light in the photoelectric sensor 1 shown in the first embodiment, the photoelectric sensor 1 is the same as that shown in the first embodiment. , The description of the configuration is omitted, and only the process of generating the combined light will be described.

In the photoelectric sensor 1, first, in the timing control circuit 2, a synchronization signal shown in FIG. 4A, an LED drive signal T1 shown in FIG. 4B, and an LED drive signal T2 shown in FIG. The synchronization signal is a pulse signal having a predetermined period and a predetermined pulse width, and is used as a detection timing of the detection circuit 4. The LED drive signals T1 and T2 are signals equivalent to the synchronization signal. Then, the synchronization signal is output to the detection circuit 4
, And the LED drive signals T1 and T2 are
And 6 are output.

In the light emitting circuits 5 and 6, the LED driving signal T
A drive current for driving the LED chips 3a and 3b is generated based on 1 and T2. Specifically, the pulse width, the conduction period, and the conduction phase of these drive currents are equivalent to the pulse width, period, and phase of the LED drive signals T1 and T2. The current amplitude, which is the amount of drive current, is a predetermined value such that the amount of power supplied to the LED chips 3a and 3b is less than the maximum rating. Then, the generated drive current is output to the LED drive leads 12a and 12b.

From the LED chips 3a and 3b, based on the driving current, the basic pulse light as the emission light as shown in FIGS. 4D and 4E is emitted. These basic pulse lights have a light intensity level (light intensity) corresponding to the current amplitude of the drive current.
The period, pulse width and phase are ideally equal to those of the LED drive signals T1 and T2. Then, the respective basic pulse lights are combined and condensed by the light projecting lens 9 to be emitted as combined light having substantially the same optical axis. This combined light is, as shown in FIG.
The pulse width and the period are equal to the basic pulse light emitted from a and 3b and the light amount level is doubled, and the period, the pulse width and the phase are equal to the synchronization signal. Then, the combined light passes through the optical path 24 and is received by the light receiving section 8.

According to such a configuration, in the light projecting means 14, the power supply cycle is shortened in a state where the power supply to each of the LED chips 3a and 3b is reduced, and the light amount level of the combined light is set to each of the LED chips 3a and 3b. Since the combined light having a predetermined light amount level and a pulse width can be emitted by increasing the pulse width from that of the basic pulse light emitted from the light source, the cycle of the combined light can be changed to the same pulse emitted from one light emitting element. The period can be shorter than the light cycle. For example, the detection speed (response speed) of the detection target 100 can be higher than that of a photoelectric sensor including one LED chip. Thereby, the response speed of the photoelectric sensor 1 can be increased. In the second embodiment, the LED
Although the drive current is individually supplied to the chips 3a and 3b, the present invention is not limited to this.
The LED 3 may be configured so that the LED chips 3a and 3b mounted on the ED 3 can be driven by one common driving lead, and a driving current may flow through this one driving lead. Can generate a combined light with a single light emitting circuit.

[Third Embodiment] Next, a third embodiment of the present invention will be described with reference to FIG. Since the third embodiment is a modification of the process of generating the combined light in the photoelectric sensor 1 shown in the first embodiment, the photoelectric sensor 1 is the same as that shown in the first embodiment. , The description of the configuration is omitted, and only the process of generating the combined light will be described.

In the photoelectric sensor 1, first, the timing control circuit 2 generates a synchronization signal shown in FIG. 5A, an LED drive signal U1 shown in FIG. 5B, and an LED drive signal U2 shown in FIG. The synchronization signal is a pulse signal having a predetermined period and a predetermined pulse width, and is used as a detection timing of the detection circuit 4. The LED driving signals U1 and U2 are signals having the same period, a pulse width of 1/2 times, and a phase shift by the pulse width with respect to the synchronization signal. Then, the synchronization signal is output to the detection circuit 4, and the LED drive signals U1 and U1
2 is output to the light emitting circuits 5 and 6.

In the light emitting circuits 5 and 6, the LED driving signal U
A drive current for driving the LED chips 3a and 3b is generated based on 1 and U2. Specifically, the pulse width, the conduction period, and the conduction phase of these drive currents are equivalent to the pulse width, period, and phase of the LED drive signals U1 and U2. The current amplitude, which is the amount of drive current, is a predetermined value such that the amount of power supplied to the LED chips 3a and 3b is less than the maximum rating. Then, the generated drive current is output to the drive leads 12 a and 12 b of the LED 3.

In the LED chips 3a and 3b, based on the driving current, the basic pulse light, which is the emitted light, as shown in FIGS. 5D and 5E is emitted. These basic pulse lights have a light amount level (light intensity) according to the drive current.
The period, pulse width and phase are ideally equal to those of the ED drive signals U1 and U2. Then, the respective basic pulse lights are synthesized and condensed by the light projecting lens 9 to be emitted as synthesized light having substantially the same optical axis. This combined light is, as shown in FIG.
The period and the light amount level are equal and the pulse width is doubled with respect to the basic pulse light emitted from b, and the period, pulse width and phase are ideally equal with respect to the synchronization signal. Then, the combined light passes through the optical path 24 and is received by the light receiving section 8.

According to such a configuration, in the light projecting means 14, the energizing phases are shifted from each other by the energizing width in a state where the energizing width and the energizing cycle for each of the LED chips 3a and 3b are made equal to each other, and the pulse width of the combined light is changed. By making the length longer than that of the basic pulse light emitted from the LED chips 3a and 3b, it is possible to emit a synthesized light having a predetermined light amount level and a pulse width.
The period of the same pulsed light emitted from one light emitting element can be made shorter, and the detection speed (response speed) of the detection target 100 is increased as compared to, for example, a photoelectric sensor including one LED chip. be able to. Thereby, the response speed of the photoelectric sensor 1 can be increased.

Fourth Embodiment Next, a fourth embodiment of the present invention will be described with reference to FIG. The same parts as those of the photoelectric sensor 1 shown in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Hereinafter, only different parts will be described.

FIG. 6 shows a line 1 in a direction perpendicular to the moving direction of the object 100 on the line 101.
1 shows a configuration of a light projecting unit 30 and a light receiving unit 8 installed so as to be opposed to each other via a light emitting device 01. In FIG.
The light projecting unit 30 includes two LEDs 33 and 34 on which LED chips 31 and 32, which are the same light emitting elements, are mounted, and a fiber coupler 35 that combines pulse lights emitted from the LED chips 31 and 32. I have. LE
D33 and 34 are formed by mounting one LED chip 31 and 32 on one base 36 and 37, respectively, and covering transparent resins 38 and 39 on these bases 36 and 37 and LED chips 31 and 32, respectively. Have been. In addition, the fiber coupler 35 is configured such that one end of each of the two fibers 35a and 35b is bundled, so that the lights incident from the two incident end faces 40a and 40b are combined on substantially the same optical axis to form one fiber. It is formed so as to exit from the exit end face 41.

The resin 38 of each LED 33 and 34
And 39, each incident end face 4 of the fiber coupler 35 near the surface.
With the installation of Oa and 40b, the pulsed light emitted from each of the LED chips 31 and 32 is synthesized by being emitted from the emission end face 41 of the fiber coupler 35, and emitted as combined light. The LEDs 33 and 34 are provided with drive signal leads 42 and 43 for inputting LED drive signals and ground leads 44 and 45, respectively. The drive signal leads 42 and 43 are 6 and the ground leads 44 and 45 are connected to a ground line.

According to such a configuration, the combined light can be generated by using the fiber coupler 35, so that one LED chip with a built-in LED chip, which is a general-purpose LED, is used.
3 and 34 can be used.

The present invention is not limited to the embodiment described above and shown in the drawings.
Extension is possible. In the present embodiment, the combined light is generated by combining two pulse lights. However, the present invention is not limited to this, and the combined light may be generated by combining three or more pulse lights. Good. The light emitting element is LED
(LED chip) is not limited to, for example,
A laser, a lamp, or the like may be used. In short, any light source that can emit pulsed light may be used.

In the present embodiment, the combined light is generated and emitted by the light projecting means. However, the present invention is not limited to this. For example, a plurality of light emitting elements may be installed at different remote places. Pulse light may be emitted from each light emitting element, and each pulse light may be combined at the position of the detection object and the light receiving unit. In the present embodiment, the combined light is generated using an LED in which two LED chips are mounted adjacently or a fiber coupler. However, the present invention is not limited to this. For example, a dichroic mirror may be used. The optical system may be used, that is, an optical system that combines a plurality of pulsed lights may be used. In the present embodiment, the present invention is applied to a transmission type photoelectric sensor in which the light projecting unit and the light receiving unit are arranged to face each other. However, the present invention is not limited to this. May be applied to a reflection-type photoelectric sensor arranged so that the light is reflected by the light receiving unit.

[0044]

As is apparent from the above description, in the photoelectric sensor of the present invention, the light emitting means combines the basic pulse lights from the plurality of light-emitting elements to form a combined light having a predetermined light amount level and pulse width. , The cycle of the combined light can be made shorter than the cycle of the same pulsed light emitted from one light-emitting element. Can be increased in detection speed (response speed). This makes it possible to prevent the light emitting element from deteriorating while increasing the response speed of the photoelectric sensor.

[Brief description of the drawings]

FIG. 1 is a block diagram of a photoelectric sensor according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a light projecting unit and a light receiving unit;

FIG. 3 is a timing chart showing the operation of each part of the photoelectric sensor.

FIG. 4 is a view corresponding to FIG. 3, showing a second embodiment of the present invention;

FIG. 5 is a view corresponding to FIG. 3, showing a third embodiment of the present invention.

FIG. 6 is a view corresponding to FIG. 2, showing a fourth embodiment of the present invention;

[Explanation of symbols]

In the drawing, 1 is a photoelectric sensor, 2 is a timing control circuit,
3, 33, 34 are LEDs, 3a, 3b, 31, 32 are L
ED chip (light emitting element), 4 is a detection circuit, 5 and 6 are light emitting circuits, 7 and 30 are light emitting sections, 8 is a light receiving section, 14 is a light emitting means, 16 is a light receiving element, 22 is a light receiving element, 22 is a light receiving circuit, 23 Denotes a light receiving means, 24 denotes an optical path, 35 denotes a fiber coupler, 100 denotes an object to be detected, and 101 denotes a line.

Claims (5)

[Claims] 1. A photoelectric sensor for emitting projection light from a light projecting means and receiving the projection light emitted from the light projecting means by a light receiving means, wherein the light projecting means projects light having substantially the same wavelength. The light receiving unit is configured to emit combined light obtained by combining the emitted light from the plurality of light emitting elements that emit light, and the light from the light emitting element based on the emission timing of the emitted light from the plurality of light emitting elements. A photoelectric sensor for receiving light having substantially the same wavelength. 2. The photoelectric sensor according to claim 1, wherein said light projecting means is configured to make optical axes of said plurality of light emitting elements substantially coincide with each other. 3. The light projecting means shifts the energization phase of the plurality of light emitting elements by a reciprocal cycle of the number of light emitting elements, thereby changing the cycle of the combined light to the cycle of light emitted from each of the light emitting elements. The photoelectric sensor according to claim 1, wherein the photoelectric sensor is shorter than the first sensor. 4. The light projecting means shortens an energization cycle in a state where the energization amount to the plurality of light emitting elements is reduced, so that the light intensity level of the combined light is higher than the light intensity level from each of the light emitting elements. The photoelectric sensor according to claim 1, wherein the photoelectric sensor is increased. 5. The light emitting means shifts an energization phase by an energization width in a state in which an energization width and an energization cycle for the plurality of light emitting elements are shortened, thereby changing a pulse width of the combined light from each of the light emitting elements. 3. The photoelectric sensor according to claim 1, wherein the pulse width is longer than the pulse width of the emitted light.