JP4957254B2 - Photoelectric sensor and photoelectric sensor light receiving unit - Google Patents

Description

  The present invention relates to a photoelectric sensor and a light receiving unit for the photoelectric sensor, and more particularly to a photoelectric sensor including a general-purpose photo IC and a light receiving unit for the photoelectric sensor.

  In general, a photoelectric sensor determines whether or not an object exists in a detection region by comparing the amount of received light signal with a predetermined threshold. However, the amount of received light varies depending on the surrounding environment. There are things to do.

  FIG. 10 is a diagram for explaining fluctuations in the amount of received light in the reflection regression photoelectric sensor. The reflection regression type photoelectric sensor is a sensor that detects a light output from an LED (Light Emitting Diode) and that is detected by blocking a light that is reflected by a reflecting plate.

  As shown in FIG. 10, the optical signal output from the LED through the light projecting lens is reflected by the reflecting plate and input to the photodiode through the light receiving lens. When dust adheres to the light projecting lens, light receiving lens, and reflector on the optical signal path, or the scratches are generated, the magnitude A of the light output from the LED is attenuated to A ′. Since the light is input to the photodiode, the amount of light received by the photodiode varies. Similarly, when the optical axis of the reflecting plate varies, the amount of light received by the photodiode also varies. Such a phenomenon is not only a reflection regression type photoelectric sensor, but also a regression type photoelectric sensor that detects light by irradiating a detection region and receiving reflected light from a detection object, and between the opposing projector and receiver. This also occurs in a transmissive photoelectric sensor that detects light by blocking the detected light by a detection object.

  When the amount of light received by the photodiode fluctuates in this way, the detection accuracy of the presence / absence of an object in the detection region deteriorates. Therefore, for example, Patent Document 1 describes a method for dealing with fluctuations in the amount of received light.

  FIG. 11 is a diagram for explaining a method for dealing with fluctuations in the amount of received light described in Patent Document 1. In FIG.

  As shown in FIG. 11, as the amount of received light attenuates, the threshold value, which is a target for comparison with the amount of received light, is reduced to determine the presence or absence of an object in the detection region without being affected by changes in the surrounding environment. be able to.

By the way, a function of comparing the amount of light received by the photodiode in the photoelectric sensor with a threshold value, and various other functions (for example, a mutual interference preventing function as described in Patent Document 2, as described in Patent Document 3). A general-purpose photo IC in which a noise reduction function or the like is mounted on one chip has been put into practical use (see, for example, Patent Document 4). By using such a general-purpose photo IC as a component, a photoelectric sensor can be designed and manufactured at a lower cost and with less labor than designing and manufacturing from scratch.
Japanese Patent No. 3684573 Japanese Patent No. 3358087 Japanese Patent No. 3454360 JP 2005-303264 A

  However, since the function for dealing with fluctuations in the amount of received light is still a special purpose, it has not been incorporated into a general-purpose photo IC (Integrated Circuit). For fixing, it is not possible to add a function for dealing with fluctuations in the amount of received light by changing the threshold value as described in Patent Document 1.

  Therefore, an object of the present invention is to provide a general-purpose photo IC that does not have a function for dealing with fluctuations in the amount of received light and that has a fixed threshold value, and the detection accuracy of an object does not deteriorate even if the amount of received light varies. A photoelectric sensor and a light receiving unit of the photoelectric sensor are provided.

In order to solve the above problems, the present invention provides a general-purpose IC including at least an amplifier, a threshold output unit, and a signal comparison unit, and receives a light output from a light projecting unit and processes it by a signal processing unit . a light receiving unit, receiving unit, internal or external to the general-purpose IC, receives the light incident from the detection area, comprising a light receiving element for outputting the magnitude of the signal corresponding to the amount of light received, the general-purpose IC The amplifier amplifies the signal output from the light receiving element , the threshold output unit outputs a threshold signal having a fixed magnitude , and the signal comparison unit compares the amplified signal with the threshold signal having a fixed magnitude. The signal processing unit outputs the determination result by determining the presence / absence of the target object in the detection region according to the comparison result output by the signal comparison unit, and the general-purpose IC outputs a signal to the outside in order to Comprises one output terminal, the amplifier, the amplified signal through a first output terminal to output to the outside of the universal IC, receiving unit is further to the general-purpose IC external, a first output terminal A light projecting element that receives and outputs an amplified signal, and a light receiving element within a predetermined range based on the amplified signal output from the capturing part. A projection light amount control unit that outputs a projection light amount control signal for changing the projection light amount to the projection unit.

Preferably, the general-purpose IC further includes a second output terminal for outputting a signal to the outside, and a light projection timing control unit for outputting a light projection timing signal indicating the timing of light projection, and performs light projection timing control. The unit outputs the light projection timing signal to the light projecting unit and the capture unit via the second output terminal, and the capture unit is connected to the second output terminal and outputs the light projection timing signal. Captures the amplified signal synchronously.

  Preferably, the capturing unit receives a light projecting timing signal indicating a light projecting timing from the light projecting unit, and captures an amplified signal in synchronization with the light projecting timing signal.

In addition, the present invention is a light receiving unit of a photoelectric sensor that includes a general-purpose IC including at least a variable gain amplifier, a threshold value output unit, and a signal comparison unit, and receives light output from the light projecting unit and processes it by the signal processing unit. Te, the light receiving unit is inside or outside the general purpose IC, receives the light incident from the detection area, comprising a light receiving element for outputting the magnitude of the signal corresponding to the amount of light received, the variable gain amplifier of the general-purpose IC is The signal output from the light receiving element is amplified and the gain is changed in accordance with the gain control signal , the threshold output unit outputs a threshold signal having a fixed magnitude , and the signal comparison unit outputs the amplified signal and the magnitude. there outputs a comparison result by comparing the threshold signal fixed, the signal processing unit, to determine the presence or absence of a target object in the detection area according to the comparison result output by the signal comparing unit outputs a determination result, pan IC has a first output terminal for outputting a signal to the outside, and a input terminal for receiving an input signal from the outside, the variable gain amplifier, the amplified signal through a first output terminal Output to the outside of the general-purpose IC, the gain control signal is input via the input terminal and sent to the variable gain amplifier, and the light receiving unit is further connected to the first output terminal outside the general-purpose IC for amplification A capture unit that captures and outputs the received signal, and a gain control signal that changes the gain of the variable gain amplifier so that the magnitude of the amplified signal output from the capture unit is within a predetermined range. And a gain controller for outputting to the terminal.

Preferably, the general-purpose IC further includes a second output terminal for outputting a signal to the outside, and a light projection timing control unit for outputting a light projection timing signal indicating the timing of light projection, and performs light projection timing control. The unit outputs the light projection timing signal to the light projecting unit and the capture unit via the second output terminal, and the capture unit is connected to the second output terminal and outputs the light projection timing signal. Captures the amplified signal synchronously.

  Preferably, the capturing unit receives a light projecting timing signal indicating a light projecting timing from the light projecting unit, and captures an amplified signal in synchronization with the light projecting timing signal.

The present invention also includes a light projecting unit, and a light receiving unit including a general-purpose IC including at least an amplifier, a threshold output unit, and a signal comparing unit, and the light output from the light projecting unit is received by the light receiving unit. A photoelectric sensor that is processed by a processing unit, wherein the light projecting unit includes a light projecting element that outputs light toward the detection region, and the light receiving unit receives light incident from the detection region inside or outside the general-purpose IC. The general-purpose IC amplifier amplifies the signal output from the light receiving element , and the threshold output unit has a fixed threshold value. outputs a signal, the signal comparing section, the amplified signal and the magnitude is compared with a threshold signal of the fixed output a comparison result, the signal processing section, detected according to the comparison result output by the signal comparing unit area Versus And outputs the determination result to determine the presence or absence of an object, a general-purpose IC includes a first output terminal for outputting a signal to the outside, the amplifier via a first output terminal of the amplified signal The light receiving unit is further connected to the first output terminal outside the general-purpose IC , and takes in and outputs the amplified signal, and outputs from the take-in section. A light projection amount control unit that outputs a light projection amount control signal for changing the light projection amount of the light projecting element to the light projecting unit so that the amount of light received by the light receiving element falls within a predetermined range based on the amplified signal. Prepare.

Preferably, the general-purpose IC further includes a second output terminal for outputting a signal to the outside, and a light projection timing control unit for outputting a light projection timing signal indicating the timing of light projection, and performs light projection timing control. The unit outputs the light projection timing signal to the light projecting unit and the capturing unit via the second output terminal, the light projecting unit is connected to the second output terminal, and the light projecting element is output Light is output in synchronization with the light projection timing signal, and the capturing unit is connected to the second output terminal, and captures an amplified signal in synchronization with the output light projection timing signal.

  Preferably, the light projecting unit further includes a light projecting timing control unit that outputs a light projecting timing signal indicating a light projecting timing, and the light projecting element outputs light in synchronization with the light projecting timing signal, and receives the light. The capture unit captures the amplified signal in synchronization with the projection timing signal.

The present invention also includes a light projecting unit, a light receiving unit including a variable gain amplifier, a general-purpose IC including at least a threshold output unit and a signal comparing unit, and the light output from the light projecting unit is received by the light receiving unit. The light projecting unit includes a light projecting element that outputs light toward the detection region, and the light receiving unit is incident on the inside or outside of the general-purpose IC from the detection region. The variable gain amplifier of the general-purpose IC amplifies the signal output from the light receiving element and increases the gain according to the gain control signal. The threshold output unit outputs a threshold signal having a fixed magnitude , and the signal comparison unit compares the amplified signal with a threshold signal having a fixed magnitude and outputs a comparison result. The signal To determine the presence or absence of a target object in the detection area according to the comparison result output outputs a determination result by較部, general purpose IC includes a first output terminal for outputting a signal to the outside, an external signal The variable gain amplifier outputs the amplified signal to the outside of the general-purpose IC through the first output terminal, and the gain control signal is input through the input terminal and is variable. The light receiving unit is further connected to the first output terminal outside the general-purpose IC , and a receiving unit that receives and outputs the amplified signal, and an amplification that is output from the capturing unit. A gain control unit that outputs to the input terminal a gain control signal that changes the gain of the variable gain amplifier so that the magnitude of the received signal falls within a predetermined range.

Preferably, the general-purpose IC further includes a second output terminal for outputting a signal to the outside, and a light projection timing control unit for outputting a light projection timing signal indicating the timing of light projection, and performs light projection timing control. The unit outputs the light projection timing signal to the light projecting unit and the capturing unit via the second output terminal, the light projecting unit is connected to the second output terminal, and the light projecting element is output Light is output in synchronization with the light projection timing signal, and the capturing unit is connected to the second output terminal, and captures an amplified signal in synchronization with the output light projection timing signal.

  Preferably, the light projecting unit further includes a light projecting timing control unit that outputs a light projecting timing signal indicating a light projecting timing, and the light projecting element outputs light in synchronization with the light projecting timing signal, and receives the light. The capture unit captures the amplified signal in synchronization with the projection timing signal.

  According to the photoelectric sensor and the light receiving unit of the photoelectric sensor of the present invention, a general-purpose photo IC that does not have a function to cope with fluctuations in the amount of received light and has a fixed threshold is used. The detection accuracy can be prevented from deteriorating.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
[First Embodiment]
The first embodiment relates to a reflection regression photoelectric sensor having a function of automatically adjusting the light projection amount of a light projecting element.

  The retroreflective photoelectric sensor is a sensor including a sensor body including a light projecting and receiving optical system and a circuit system, and a retroreflective plate (hereinafter referred to as a reflector). Retroreflective (also referred to as retroreflection or retroreflection) refers to reflection of light that is finally reflected in the same direction as the direction of projection, such as a corner cube.

  The retroreflective photoelectric sensor includes a sensor body and a reflector. The light projected from the light projecting portion of the sensor body is reflected by the reflector, and the reflected light is received by the light receiving portion of the sensor body.

  The retroreflective photoelectric sensor is used to detect an object to be detected that is carried on a belt conveyor in a factory production line, for example. When there is an object to be detected between the sensor main body and the reflector, the light from the sensor main body to the reflector is blocked by the object to be detected, and the light cannot reach the sensor light receiving unit, so that the object is detected.

FIG. 1 is a diagram illustrating a configuration of a photoelectric sensor according to a first embodiment of the present invention.
With reference to FIG. 1, the photoelectric sensor includes a light projecting unit 30 and a light receiving unit 40.

  The light projecting unit 30 includes a light projecting lens 71, a D / A converter 23, a drive circuit 2, and a light projecting element 1.

  The light projecting element 1 is composed of an LED, and outputs pulsed light in synchronization with a light projecting timing signal.

The light projecting lens 71 irradiates the light output from the light projecting element 1 toward the detection area.
The D / A conversion unit 23 converts the light projection amount control signal (digital signal) sent from the light projection amount control unit 22 into an analog signal and supplies the analog signal to the drive circuit 2.

  The drive circuit 2 drives the light projecting element 1 in synchronization with the light projection timing signal. The drive circuit 2 changes the light projection amount of the light projecting element according to the light projection amount control signal output from the D / A converter 23. More specifically, when the light emission amount control signal specifies an increase in the light emission amount, the drive circuit 2 increases the light emission amount of the light projecting element by a certain value, and the light emission amount control signal reduces the light emission amount. When specifying, the light projection amount of the light projecting element is decreased by a certain value.

  The light receiving unit 40 includes a general-purpose photo IC 11 including a light receiving element 5, an amplifier 6, a threshold output unit 4, a signal comparison unit 7, a signal processing unit 8, a light projection timing control unit 3, and an output processing unit 9; The A / D conversion unit 21 and the light projection amount control unit 22 are provided.

  The light receiving element 5 is composed of a photodiode, receives light incident from the detection region, and outputs a signal having a magnitude corresponding to the amount of light received.

  The amplifier 6 amplifies the signal output from the light receiving element 5, outputs the amplified signal (voltage) to the signal comparison unit 7, and outputs it to the outside of the general-purpose photo IC 11 through the first output terminal 12.

  The threshold output unit 4 outputs a threshold signal (voltage) having a fixed magnitude obtained by dropping the level by one step from the voltage of the power source of the general-purpose photo IC 11 (not shown).

  The signal comparison unit 7 compares the signal amplified by the amplifier 6 with the threshold signal supplied from the threshold output unit 4 and outputs a comparison result.

  The signal processing unit 8 instructs the light projection timing control unit 3 to output a light projection timing signal indicating the light projection timing of the light projection unit 30. The signal processing unit 8 determines the presence / absence of the target object according to the comparison result output from the signal comparison unit 7 immediately after the light projection timing of the light projection unit 30, and sends a determination signal to the output processing unit 9. That is, the signal processing unit 8 determines that the target object does not exist in the detection region when the magnitude of the amplified signal exceeds the magnitude of the threshold signal, and the magnitude of the amplified signal is the magnitude of the threshold signal. In the following cases, it is determined that the target object exists in the detection area.

  In addition, the signal processing unit 8 performs processing for preventing mutual interference with adjacent photoelectric sensors, and performs processing for preventing malfunction due to disturbance light such as a fluorescent lamp.

  The light projection timing control unit 3 outputs a light projection timing signal to the outside of the general-purpose photo IC 11 through the second output terminal 14 in accordance with an instruction from the signal processing unit 8. The light projection timing signal is sent to the A / D converter 21 of the light receiving unit 40 and the drive circuit 2 of the light projecting unit 30.

  The output processing unit 9 is connected to the mode input terminal 15 and receives an L / D signal from the outside through the mode input terminal 15. When the input L / D signal indicates the light mode, the output processing unit 9 outputs a signal that is turned on when the target object is present and turned off when the target object is not present, through the third output terminal 16. Output to the circuit 10. When the input L / D signal represents the dark mode, the output processing unit 9 outputs, through the third output terminal 16, a signal that is turned off when the target object exists and turned on when the target object does not exist. Output to the circuit 10.

The output circuit 10 is a circuit that manages an interface with the outside of the photoelectric sensor.
The light receiving lens 72 condenses the light from the detection region and outputs it to the light receiving element 5.

  The A / D conversion unit 21 is connected to the first output terminal 12, samples the signal amplified by the amplifier 6 in synchronization with the light projection timing signal, and outputs the sampled signal to the light projection amount control unit 22.

  Based on the amplified signal sampled by the A / D conversion unit 21, the light projection amount control unit 22 changes the light projection amount of the light projection element 1 so that the light reception amount of the light reception element 5 falls within a predetermined range. A projection light amount control signal (digital signal) is sent to the projection unit 30. More specifically, the light projection amount control unit 22 obtains the light reception amount of the light receiving element 5 based on the amplified signal sampled by the A / D conversion unit 21, and the light reception amount of the light receiving element 5 is the lower limit of a predetermined range. When the received light amount is smaller than the (predetermined value), a light projection amount control signal (digital signal) for increasing the light projection amount of the light projecting element 1 until the amount of received light becomes equal to or greater than the lower limit (prescribed value) of the predetermined range. Send to. Further, the light projection amount control unit 22 projects the light when the light receiving amount of the light receiving element 5 is larger than the upper limit (specified value) of the predetermined range until the received light amount becomes equal to or higher than the upper limit (specified value) of the predetermined range. A light projection amount control signal (digital signal) for reducing the light projection amount of the element 1 is sent to the light projection unit 30.

(Photoelectric sensor structure)
Next, the structure of the reflection regression photoelectric sensor described above will be described.

FIG. 2 is an external perspective view of the reflection regression photoelectric sensor according to the first embodiment of the present invention.
Referring to FIG. 2, the reflection regression photoelectric sensor has a transmission / reception integrated type structure in which a light projecting unit and a light receiving unit are accommodated in a common housing. The sensor body is provided with a light receiving and projecting window 203 on the front surface of the case 206. The window 203 is held by a protective member 202 so as not to drop off. An indicator lamp 205 is provided on the upper surface of the case 206 so that the detection result can be understood.

(Following operation of light intensity)
FIG. 3 is a diagram for explaining the follow-up of the light projection amount by the photoelectric sensor according to the first embodiment of the present invention.

  Referring to FIG. 3, conventionally, since the light projection amount is constant as shown in S <b> 1, it is impossible to cope with the decrease in the amount of received light R <b> 1. On the other hand, in the embodiment of the present invention, the received light amount R2 can be kept constant by increasing the light projection amount as shown in S2 while keeping the threshold value constant.

  As described above, the reflection regression photoelectric sensor of the first embodiment does not have a function for dealing with fluctuations in the amount of received light, and uses a general-purpose photo IC with a fixed threshold value to reduce the amount of received light. Therefore, it is possible to prevent the detection accuracy of the object from deteriorating. If a general-purpose photo IC having a noise reduction function, a mutual interference prevention function, etc. is used, a photoelectric sensor having both of these functions and a function to cope with fluctuations in the amount of received light is designed and manufactured at low cost and with low labor. be able to.

[Second Embodiment]
The second embodiment relates to a reflection regression photoelectric sensor having a function of automatically adjusting the gain of an amplifier.

FIG. 4 is a diagram illustrating the configuration of the photoelectric sensor according to the second embodiment of the present invention.
With reference to FIG. 4, the photoelectric sensor includes a light projecting unit 50 and a light receiving unit 60.

The light projecting unit 50 includes a light projecting lens 71, a drive circuit 2, and a light projecting element 1.
The light projecting element 1 is composed of an LED, and outputs pulsed light in synchronization with a light projecting timing signal.

The light projecting lens 71 irradiates the light output from the light projecting element 1 toward the detection area.
The drive circuit 2 drives the light projecting element 1 in synchronization with the light projection timing signal.

  The light receiving unit 60 includes a general-purpose photo IC 29 including a light receiving element 5, a variable gain amplifier 56, a threshold output unit 4, a signal comparison unit 7, a signal processing unit 8, a light projection timing control unit 3, and an output processing unit 9, and an A / A A D conversion unit 21 and a gain control unit 24 are provided.

  The light receiving element 5 is composed of a photodiode, receives light incident from the detection region, and outputs a signal having a magnitude corresponding to the amount of light received.

  The variable gain amplifier 56 amplifies the signal output from the light receiving element 5, outputs the amplified signal (voltage) to the signal comparison unit 7, and outputs it to the outside of the general-purpose photo IC 29 through the first output terminal 12. To do. The variable gain amplifier 56 changes the gain according to the gain control signal sent from the gain input terminal 13. More specifically, the variable gain amplifier 56 increases the gain by a fixed value when the gain control signal specifies an increase in gain, and increases the gain when the gain control signal specifies a decrease in gain. Decrease by a certain value.

  The threshold output unit 4 outputs a threshold signal (voltage) having a fixed magnitude obtained by dropping the level by one step from the power supply voltage of the general-purpose photo IC 29 (not shown).

  The signal comparison unit 7 compares the signal amplified by the amplifier with the magnitude of the threshold signal supplied from the threshold output unit 4 and outputs a comparison result.

  The signal processing unit 8 instructs the light projection timing control unit 3 to output a light projection timing signal indicating the light projection timing of the light projection unit 50. The signal processing unit 8 determines the presence or absence of the target object according to the comparison result output from the signal comparison unit 7 immediately after the light projection timing of the light projection unit 50, and sends a determination signal to the output processing unit 9. That is, the signal processing unit 8 determines that the target object does not exist in the detection region when the magnitude of the amplified signal exceeds the magnitude of the threshold signal, and the magnitude of the amplified signal is the magnitude of the threshold signal. In the following cases, it is determined that the target object exists in the detection area.

  The light projection timing control unit 3 outputs a light projection timing signal to the outside of the general-purpose photo IC 29 through the second output terminal 14 in accordance with an instruction from the signal processing unit 8. The light projection timing signal is sent to the A / D converter 21 of the light receiving unit 60 and the drive circuit 2 of the light projecting unit 50.

  The output processing unit 9 is connected to the mode input terminal 15 and receives an L / D signal from the outside through the mode input terminal 15. When the input L / D signal indicates the light mode, the output processing unit 9 outputs a signal that is turned on when the target object is present and turned off when the target object is not present, through the third output terminal 16. Output to the circuit 10. When the input L / D signal represents the dark mode, the output processing unit 9 outputs, through the third output terminal 16, a signal that is turned off when the target object exists and turned on when the target object does not exist. Output to the circuit 10.

The output circuit 10 is a circuit that manages an interface with the outside of the photoelectric sensor.
The light receiving lens 72 condenses the light from the detection region and outputs it to the light receiving element 5.

  The A / D conversion unit 21 is connected to the first output terminal 12, samples the signal amplified by the amplifier in synchronization with the projection timing signal, and outputs the sampled signal to the gain control unit 24.

  The gain controller 24 sends a gain control signal for changing the gain of the variable gain amplifier 56 to the gain input terminal 13 so that the magnitude of the amplified signal sampled by the A / D converter 21 falls within a predetermined range. send. More specifically, when the magnitude of the amplified signal sampled by the A / D conversion unit 21 is smaller than the lower limit (specified value) of a predetermined range, the gain control unit 24 A gain control signal for increasing the gain of the variable gain amplifier 56 is sent to the gain input terminal 13 until it reaches the lower limit (specified value) of the predetermined range. Further, the gain control unit 24 sets the amplified signal to be equal to or less than the upper limit (specified value) of the predetermined range when the magnitude of the sampled amplified signal is larger than the upper limit (specified value) of the predetermined range. Until that time, a gain control signal for decreasing the gain of the variable gain amplifier 56 is sent to the gain input terminal 13.

  As described above, the reflection regression photoelectric sensor of the second embodiment does not have a function to cope with fluctuations in the amount of received light, and the output of the variable gain amplifier uses a general-purpose photo IC with a fixed threshold value. When it decreases, control is performed so as to increase the gain of the variable gain amplifier, so that the detection accuracy of the object can be prevented from deteriorating. In addition, if a general-purpose photo IC having a noise reduction function, a mutual interference prevention function, etc. is used, a photoelectric sensor having both of these functions and a function to cope with fluctuations in the amount of received light can be designed at low cost and with low labor. Can be manufactured.

[Third Embodiment]
The third embodiment relates to a transmissive photoelectric sensor having a function of automatically adjusting a light projection amount.

FIG. 5 is a diagram for explaining the outline of the photoelectric sensor according to the third embodiment of the present invention.
Referring to FIG. 5, in the transmissive photoelectric sensor, a light projecting unit and a light receiving unit are arranged to face each other. When there is no detection object, the light output from the light projecting unit is input to the light receiving unit. When the detection object exists, the light output from the light projecting unit is blocked by the detection object, so that the amount of light input to the light receiving unit is reduced. The light projecting unit and the light receiving unit are connected by a synchronization signal line A and a synchronization signal line B.

FIG. 6 is a diagram illustrating a configuration of a photoelectric sensor according to the third embodiment of the present invention.
Referring to FIG. 6, this photoelectric sensor is different from the photoelectric sensor of the first embodiment in FIG. 1 in that a light projection timing control unit 93 is included in the light projection unit 130.

Hereinafter, differences from the photoelectric sensor of the first embodiment will be described.
The light projection timing control unit 93 spontaneously outputs a light projection timing signal to the drive circuit 2 in the light projection unit 130 without being controlled by the signal processing unit 98 of the light receiving unit 140. The projection timing control unit 93 and the A / D conversion unit 21 are connected by a synchronization signal line A, and a projection timing signal is transmitted from the projection timing control unit 93 to the A / D conversion unit 21 through the synchronization signal line A. Sent to.

  Further, the projection light quantity control unit 22 and the D / A conversion unit 23 are connected by a synchronization signal line B. A projection light amount control signal is sent from the projection light amount control unit 22 to the D / A conversion unit 23 through the synchronization signal line B.

  As described above, according to the transmission photoelectric sensor of the third embodiment, similarly to the reflection regression photoelectric sensor of the first embodiment, it does not have a function to cope with fluctuations in the amount of received light and has a threshold value. Since a fixed general-purpose photo IC is used to control the light projection amount to increase with respect to the decrease in the amount of received light, the detection accuracy of the object can be prevented from deteriorating. In addition, if a general-purpose photo IC having a noise reduction function, a mutual interference prevention function, etc. is used, a photoelectric sensor having both of these functions and a function to cope with fluctuations in the amount of received light can be designed at low cost and with low labor. Can be manufactured.

[Fourth Embodiment]
The fourth embodiment relates to a transmissive photoelectric sensor having a function of automatically adjusting the gain of an amplifier.

FIG. 7 is a diagram for explaining the outline of the photoelectric sensor according to the fourth embodiment of the present invention.
Referring to FIG. 7, in this transmissive photoelectric sensor, a light projecting unit and a light receiving unit are arranged to face each other as in the third embodiment. Further, the light projecting unit and the light receiving unit are connected by a synchronization signal line A.

FIG. 8 is a diagram illustrating the configuration of a photoelectric sensor according to the fourth embodiment of the present invention.
Referring to FIG. 8, this photoelectric sensor is different from the photoelectric sensor of the second embodiment in FIG. 4 in that a light projection timing control unit 93 is included in the light projection unit 150.

Hereinafter, differences from the photoelectric sensor of the second embodiment will be described.
The light projection timing control unit 93 spontaneously outputs a light projection timing signal to the drive circuit 2 in the light projection unit 150 without being controlled by the signal processing unit 98 of the light receiving unit 160. The projection timing control unit 93 and the A / D conversion unit 21 are connected by a synchronization signal line A, and a projection timing signal is transmitted from the projection timing control unit 93 to the A / D conversion unit 21 through the synchronization signal line A. Sent to.

  As described above, according to the transmission photoelectric sensor of the fourth embodiment, similarly to the reflection regression photoelectric sensor of the second embodiment, it does not have a function to deal with fluctuations in the amount of received light and has a threshold value. When the output of the amplifier is decreased using a fixed general-purpose photo IC, the gain of the amplifier is controlled to increase, so that the detection accuracy of the object can be prevented from deteriorating. In addition, if a general-purpose photo IC having a noise reduction function, a mutual interference prevention function, etc. is used, a photoelectric sensor having both of these functions and a function to cope with fluctuations in the amount of received light can be designed at low cost and with low labor. Can be manufactured.

(Modification)
The present invention is not limited to the above-described embodiment, and includes, for example, the following modifications.

(1) In the case of DC light In the embodiment of the present invention, the light projection timing control unit outputs a light projection timing signal, and the light projecting element outputs pulse light in synchronization with the light projection timing signal. The A / D converter samples the output of the amplifier or the variable gain amplifier in synchronization with the above, but the present invention is not limited to this. When the light projecting element outputs DC light, the photoelectric sensor may not include the light projecting timing control unit. The light projecting element and the A / D conversion unit may output and sample light at an appropriate timing without being controlled by the light projecting timing control unit.

(2) Inside of general-purpose photo IC The light-receiving element, the signal processing unit, and the output processing unit described in the embodiment of the present invention are not necessarily inside the general-purpose photo IC, and may be outside the general-purpose photo IC. Good. On the other hand, a general-purpose photo IC must include an amplifier (or a variable gain amplifier), a threshold output unit, and a signal processing unit.

(3) Structure of photoelectric sensor In the first and second embodiments of the present invention, the detection method is a reflection regression type photoelectric sensor. However, the present invention is not limited to this, and the detection method is a reflection type. There may be. The reflection regression type and reflection type photoelectric sensors may have a fiber type structure.

FIG. 9 is an external perspective view of the fiber photoelectric sensor with the upper cover opened.
As shown in the figure, the photoelectric sensor has a multi-package plastic casing 101. A light projecting fiber 302 and a light receiving fiber 303 are inserted into the front portion of the housing 101, and are fixed to be detached by operating the clamp lever 103. The electric cord 4 is drawn out from the rear part of the casing 101. The illustrated electric cord 304 includes a grounding core wire 141, a positive power source core wire 142, a detection output core wire 143, and a diagnostic output core wire 144. The casing 101 is fixed to a mounting surface such as a control panel via a DIN rail (not shown). What is indicated by reference numeral 104 is a DIN rail fitting groove. A transparent upper cover 102 is attached to the top of the housing 101 so as to be openable and closable. On the upper surface of the casing 101 exposed with the upper cover 102 opened, a first display 105, a second display 106, a first operation button 107, a second operation button 108, A third operation button 109, a first slide operator 110, and a second slide operator 111 are provided. Further, a head portion 120 including a lens and the like that can be attached to and detached from the fiber is provided at the ends of the light projecting fiber 2 and the light receiving fiber 3. Although not shown, the fiber photoelectric sensor includes an amplifier that clamps the fiber and incorporates a light projecting element and a light receiving element.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure showing the structure of the photoelectric sensor of the 1st Embodiment of this invention. It is an external appearance perspective view of the reflective regression type photoelectric sensor of the 1st Embodiment of this invention. It is a figure for demonstrating the tracking of the light projection amount by the photoelectric sensor of the 1st Embodiment of this invention. It is a figure showing the structure of the photoelectric sensor of the 2nd Embodiment of this invention. It is a figure for demonstrating the outline of the photoelectric sensor of the 3rd Embodiment of this invention. It is a figure showing the structure of the photoelectric sensor of the 3rd Embodiment of this invention. It is a figure for demonstrating the outline of the photoelectric sensor of the 4th Embodiment of this invention. It is a figure showing the structure of the photoelectric sensor of the 4th Embodiment of this invention. It is an external appearance perspective view in the state where the upper cover of the fiber photoelectric sensor was opened. It is a figure for demonstrating the fluctuation | variation of the light reception amount in a reflection regression type photoelectric sensor. It is a figure for demonstrating the method corresponding to the fluctuation | variation of the light reception amount described in patent document 1. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Light emitting element, 2 Drive circuit, 3,93 Light projection timing control part, 4 Threshold output part, 5 Light receiving element, 6 Amplifier, 7 Signal comparison part, 8,98 Signal processing part, 9 Output processing part, 10 Output circuit 11, 29, 121, 129 General-purpose photo IC, 12 First output terminal, 13 Gain input terminal, 14 Second output terminal, 15 Mode input terminal, 16 Third output terminal, 21 A / D converter, 22 Light Emitting Control Unit, 23 D / A Conversion Unit, 24 Gain Control Unit, 30, 50, 130, 150 Light Emitting Unit, 40, 60, 140, 160 Light Receiving Unit, 56 Variable Gain Amplifier, 71 Projecting Lens, 72 Light-receiving lens, 101 Plastic housing, 102 Top cover, 103 Clamp lever, 104 DIN rail fitting groove, 105 First indicator, 106 Second indicator 107 1st operation button, 108 2nd operation button, 109 3rd operation button, 110 1st slide operation element, 111 2nd slide operation element, 120 head part, 141 Core wire for grounding, 142 Positive power supply 143 core wire for detection output, 144 core wire for diagnosis output, 202 protective member, 203 light receiving window, 205 indicator lamp, 206 case, 302 light projecting fiber, 303 light receiving fiber, 304 power cord.

Claims (12)

A light receiving unit of a photoelectric sensor that includes a general-purpose IC including at least an amplifier, a threshold output unit, and a signal comparison unit, receives light output from a light projecting unit, and processes the light by a signal processing unit ,
The light receiving unit is inside or outside the general-purpose IC ,
A light receiving element that receives light incident from the detection region and outputs a signal having a magnitude corresponding to the amount of light received,
The amplifier of the general-purpose IC amplifies a signal output from the light receiving element ,
The threshold output unit outputs a threshold signal having a fixed magnitude ,
The signal comparison unit compares the amplified signal with a threshold signal having a fixed magnitude, and outputs a comparison result.
The signal processing unit determines the presence or absence of the target object in the detection region according to the comparison result output by the signal comparison unit, and outputs a determination result,
The general purpose IC includes a first output terminal for outputting a signal to the outside,
The amplifier outputs the amplified signal to the outside of the general-purpose IC through the first output terminal,
The light receiving unit is further external to the general-purpose IC .
A capture unit connected to the first output terminal for capturing and outputting the amplified signal;
Based on the amplified signal output from the capturing unit, a light projection amount control signal for changing the light projection amount of the light projecting element so that the amount of light received by the light receiving element falls within a predetermined range is sent to the light projecting unit. A photoelectric sensor light receiving unit including an output light intensity control unit. The general-purpose IC further includes:
A second output terminal for outputting a signal to the outside;
A projection timing control unit that outputs a projection timing signal representing the timing of projection ,
The light projection timing control unit outputs the light projection timing signal to the light projection unit and the capture unit via the second output terminal,
The light receiving unit of the photoelectric sensor according to claim 1, wherein the capturing unit is connected to the second output terminal and captures the amplified signal in synchronization with the output light projection timing signal.   2. The photoelectric sensor according to claim 1, wherein the capturing unit receives a light projection timing signal representing a light projection timing from the light projecting unit, and captures the amplified signal in synchronization with the light projection timing signal. Light receiving unit. A light receiving unit of a photoelectric sensor that includes a general-purpose IC including at least a variable gain amplifier, a threshold output unit, and a signal comparison unit , receives light output from a light projecting unit, and processes it by a signal processing unit ,
The light receiving unit is inside or outside the general-purpose IC ,
A light receiving element that receives light incident from the detection region and outputs a signal having a magnitude corresponding to the amount of light received,
The variable gain amplifier of the general-purpose IC amplifies the signal output from the light receiving element, and changes the gain according to a gain control signal ,
The threshold output unit outputs a threshold signal having a fixed magnitude ,
The signal comparison unit compares the amplified signal with a threshold signal having a fixed magnitude, and outputs a comparison result.
The signal processing unit determines the presence or absence of the target object in the detection region according to the comparison result output by the signal comparison unit, and outputs a determination result,
The general-purpose IC includes a first output terminal for outputting a signal to the outside,
Including an input terminal for receiving an input of an external signal ,
The variable gain amplifier outputs the amplified signal to the outside of the general-purpose IC through the first output terminal,
The gain control signal is input via the input terminal and sent to the variable gain amplifier,
The light receiving unit is further external to the general-purpose IC .
A capture unit connected to the first output terminal for capturing and outputting the amplified signal;
A gain control unit that outputs a gain control signal that changes the gain of the variable gain amplifier to the input terminal so that the magnitude of the amplified signal output from the capturing unit is within a predetermined range. Light receiving unit for photoelectric sensor. The general-purpose IC further includes:
A second output terminal for outputting a signal to the outside;
A projection timing control unit that outputs a projection timing signal representing the timing of projection ,
The light projection timing control unit outputs the light projection timing signal to the light projection unit and the capture unit via the second output terminal,
The light receiving unit of the photoelectric sensor according to claim 4, wherein the capturing unit is connected to the second output terminal and captures the amplified signal in synchronization with the output light projection timing signal.   5. The photoelectric sensor according to claim 4, wherein the capture unit receives a light projection timing signal representing a light projection timing from the light projection unit, and captures the amplified signal in synchronization with the light projection timing signal. Light receiving unit. Including a light projecting unit, a light receiving unit including a general-purpose IC including at least an amplifier, a threshold output unit, and a signal comparing unit, and the light output from the light projecting unit is received by the light receiving unit and processed by the signal processing unit. A photoelectric sensor,
The light projecting unit is
It has a light projecting element that outputs light toward the detection area,
The light receiving unit is inside or outside the general-purpose IC ,
A light receiving element that receives light incident from the detection region and outputs a signal having a magnitude corresponding to the amount of light received,
The amplifier of the general-purpose IC amplifies a signal output from the light receiving element ,
The threshold output unit outputs a threshold signal having a fixed magnitude ,
The signal comparison unit compares the amplified signal with a threshold signal having a fixed magnitude, and outputs a comparison result.
The signal processing unit determines the presence or absence of the target object in the detection region according to the comparison result output by the signal comparison unit, and outputs a determination result,
The general purpose IC includes a first output terminal for outputting a signal to the outside,
The amplifier outputs the amplified signal to the outside of the general-purpose IC through the first output terminal,
The light receiving unit is further external to the general-purpose IC .
A capture unit connected to the first output terminal for capturing and outputting the amplified signal;
Based on the amplified signal output from the capturing unit, a light projection amount control signal for changing the light projection amount of the light projecting element so that the amount of light received by the light receiving element falls within a predetermined range is sent to the light projecting unit. A photoelectric sensor provided with an output light intensity control unit. The general-purpose IC further includes:
A second output terminal for outputting a signal to the outside;
A projection timing control unit that outputs a projection timing signal representing the timing of projection ,
The light projection timing control unit outputs the light projection timing signal to the light projection unit and the capture unit via the second output terminal,
The light projecting unit is connected to the second output terminal, and the light projecting element outputs light in synchronization with the output light projecting timing signal.
The photoelectric sensor according to claim 7, wherein the capturing unit is connected to the second output terminal and captures the amplified signal in synchronization with the output light projection timing signal. The light projecting unit further includes:
A projection timing control unit for outputting a projection timing signal representing the timing of projection,
The light projecting element outputs light in synchronization with the light projection timing signal,
The photoelectric sensor according to claim 7, wherein the capturing unit captures the amplified signal in synchronization with the light projection timing signal. A light-receiving unit including a general-purpose IC including at least a light projecting unit, a variable gain amplifier, a threshold output unit, and a signal comparing unit, and the signal processing unit receives light output from the light projecting unit by the light receiving unit. A photoelectric sensor for processing by :
The light projecting unit is
It has a light projecting element that outputs light toward the detection area,
The light receiving unit is inside or outside the general-purpose IC ,
A light receiving element that receives light incident from the detection region and outputs a signal having a magnitude corresponding to the amount of light received,
The variable gain amplifier of the general-purpose IC amplifies the signal output from the light receiving element, and changes the gain according to a gain control signal ,
The threshold output unit outputs a threshold signal having a fixed magnitude ,
The signal comparison unit compares the amplified signal with a threshold signal having a fixed magnitude, and outputs a comparison result.
The signal processing unit determines the presence or absence of the target object in the detection region according to the comparison result output by the signal comparison unit, and outputs a determination result,
The general-purpose IC includes a first output terminal for outputting a signal to the outside,
Including an input terminal for receiving an input of an external signal,
The variable gain amplifier outputs the amplified signal to the outside of the general-purpose IC through the first output terminal,
The gain control signal is input via the input terminal and sent to the variable gain amplifier,
The light receiving unit is further external to the general-purpose IC .
A capture unit connected to the first output terminal for capturing and outputting the amplified signal;
A gain control unit that outputs a gain control signal that changes the gain of the variable gain amplifier to the input terminal so that the magnitude of the amplified signal output from the capturing unit is within a predetermined range. Photoelectric sensor. The general-purpose IC further includes:
A second output terminal for outputting a signal to the outside;
A projection timing control unit that outputs a projection timing signal representing the timing of projection ,
The light projection timing control unit outputs the light projection timing signal to the light projection unit and the capture unit via the second output terminal,
The light projecting unit is connected to the second output terminal, and the light projecting element outputs light in synchronization with the output light projecting timing signal.
The capture unit, which is connected to the second output terminal, the photoelectric sensor of the synchronization with the outputted light projection timing signals taking said amplified signal,請 Motomeko 10 wherein. The light projecting unit further includes:
A projection timing control unit for outputting a projection timing signal representing the timing of projection,
The light projecting element outputs light in synchronization with the light projection timing signal,
The photoelectric sensor according to claim 10, wherein the capturing unit captures the amplified signal in synchronization with the light projection timing signal.

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