Background suppression photoelectric sensor realized based on double PD

Abstract

The utility model discloses a background suppression photoelectric sensor realized based on double PD. The background suppression photoelectric sensor comprises an MCU control circuit, an LED drive circuit, an acquisition module, a target object, a differential amplification circuit, a voltage comparison circuit and a self-adaptive output circuit. The acquisition module is used for receiving reflected light signals of a target object and converting the reflected light signals, then the differential amplification circuit amplifies and converts PD signals received by the acquired signals, and then analog quantity signals are converted into pulse signals through the voltage comparison circuit, so that the MCU control circuit can be used for processing logic signals and modulating PWM signals. The LED driving circuit is arranged to drive the LED diode D6 to work; the background suppression photoelectric sensor realized by a photodiode PD1, a photodiode PD2, a differential amplification circuit, a voltage comparison circuit and an MCU control circuit adopts an automatic frequency conversion technology to solve the problem of optical crosstalk among multiple sensors, and is suitable for background suppression photoelectric sensing.

Description

Technical Field

[0001] The utility model relates to the technical field of sensors, in particular to a background suppression photoelectric sensor based on dual PD implementation. Background Technique

[0002] The background suppression sensor is one of the most widely used photoelectric sensors in the field of industrial automation. There are many types of it. Classified by light source: infrared photoelectric sensor, red light photoelectric sensor, laser photoelectric sensor. Classified by function: background suppression photoelectric sensor, foreground suppression photoelectric sensor, etc. Its main feature is to shield the background and is not affected by the background and object colors during operation.

[0003] There are various implementation methods for background suppression photoelectric sensors. One is to detect the target object and shield the background based on the triangulation method. Another is to detect the target object and shield the background based on the direct distance measurement method.

[0004] The following are three common measurement methods for improving the laser life as examples:

[0005] I. Dual PD background suppression. Dual PD is a photoelectric detection device integrating two photodiodes. The two photodiodes are arranged in parallel, and the distance between the two PDs is very small (micrometer level), which are respectively called the distal PD and the proximal PD. Its principle is that the sensor emits collimated light. After the light irradiates the detection target object and is reflected to the receiving lens, it is received by the PD photodetector. According to the principle of triangulation method, for different distances of the detection target object, the signals received by the two PD diodes are different. According to the difference of the PD signals, the distance of the target object can be judged.

[0006] II. PSD background suppression. The PSD optoelectronic device is an optoelectronic device with an array layout composed of multiple photodiodes, and the interval between each photodiode is very small (micrometer level), and it can convert the light intensity signal into an analog signal output. Its principle is that the sensor emits collimated light. After the light irradiates the detection target object and is reflected to the receiving lens, it is received by the PD photodetector. According to the principle of triangulation method, for different distances of the detection target object, the spot positions received by the PSD are different, and the signal intensities received by the PSD array are also different, and the output analog signal value changes.

[0007] III. Direct ranging background suppression. Based on the dToF or iToF ranging technology, directly measure the distance between the target object and the background. According to the distance between the two, distinguish the target object from the background, so as to realize the detection function of background suppression. For this reason, we propose a background suppression photoelectric sensor based on dual PD implementation. Content of the Utility Model

[0008] The purpose of the present utility model is to provide a background suppression photoelectric sensor based on dual PDs to solve the problems proposed in the background art.

[0009] To achieve the above object, the present utility model provides the following technical solution: A background suppression photoelectric sensor based on dual PDs, comprising an MCU control circuit, an LED driving circuit, a collection module, a target object, a differential amplification circuit, a voltage comparison circuit, and an adaptive output circuit;

[0010] The collection module includes an LED diode D6, a photodiode PD1, and a photodiode PD2. A lens is provided on one side of the LED diode D6, and lenses are also provided for the photodiode PD1 and the photodiode PD2. The output end of the LED driving circuit is connected to the LED diode D6. The target object is disposed in front of the LED diode D6, the photodiode PD1, and the photodiode PD2. The photodiode PD1 and the photodiode PD2 receive the reflected light of the target object. The photodiode PD1 and the photodiode PD2 are electrically connected to the input end of the differential amplification circuit. The output end of the differential amplification circuit is connected to the input end of the MCU control circuit through the voltage comparison circuit. The output end of the MCU control circuit is connected to the input end of the LED driving circuit. Another output end of the MCU control circuit is connected to the adaptive output circuit;

[0011] The collection module is used for receiving and converting the reflected light signal of the target object;

[0012] The differential amplification circuit is used for amplifying and converting the PD signal received by the collection signal;

[0013] The voltage comparison circuit is used for converting the analog signal into a pulse signal;

[0014] The MCU control circuit is used for logic signal processing and PWM signal modulation;

[0015] The LED driving circuit is used for driving the LED diode D6 to work;

[0016] The adaptive output circuit is used for outputting the logic signal processed by the MCU control circuit.

[0017] Further, a resistor R2 and a capacitor C4 are connected to the photodiode PD1 and the photodiode PD2. A resistor R9 and a resistor R10 are respectively connected to the photodiode PD1 and the photodiode PD2. A capacitor C5 and a capacitor C9 are respectively connected between the photodiode PD1 and the resistor R9 and between the photodiode PD2 and the resistor R10. A reference voltage REF1 is further included, and the reference voltage REF1 includes a resistor R5, a resistor R8, and a capacitor C10. The resistor R5 is connected to the resistor R8, and the resistor R8 is connected to the capacitor C10.

[0018] Further, the differential amplifier circuit includes an amplifier U2.1, an amplifier U2.2, a resistor R3, a capacitor C1, a resistor R11, a capacitor C11, a capacitor C13, a resistor R1, and a capacitor C2. The reference voltage REF1 is loaded to the positive terminals of the amplifier U2.1 and the amplifier U2.2. The amplifier U2.1 is connected to the resistor R3 and the capacitor C1. The capacitor C5 is connected to the negative terminal of the amplifier U2.1. The capacitor C9 is connected to the positive terminal of the amplifier U2.1. The capacitor C9 is connected to the capacitor C11 and the resistor R11. A capacitor C7 and a resistor R6 are connected between the amplifier U2.1 and the amplifier U2.2. The amplifier U2.2 is connected to the resistor R1 and the capacitor C2. The signal amplified by the amplifier U2.1 is input to the amplifier U2.2 for secondary amplification through the capacitor C7 and the resistor R2. The amplifier U2.2 is connected to the resistor R7.

[0019] Further, a diode D1 and a diode D2 are further included. The diode D1 is forward - biased, and the diode D2 is reverse - biased. The diode D1 and the diode D2 form an amplitude circuit and are connected to the capacitor C2.

[0020] Further, the voltage comparison circuit includes a low - voltage comparator U7, a resistor R22, a resistor R21, and a capacitor C17. The signal amplified by the amplifier U2.2 is input to the positive terminal of the low - voltage comparator U7 through the resistor R7. The resistor R22 is connected to the resistor R21, and the resistor R21 is connected to the capacitor C17. The resistor R22, the resistor R21, and the capacitor C17 form a reference voltage REF2 and are connected to the negative terminal of the low - voltage comparator U7.

[0021] Further, the MCU control circuit includes a chip U5, a power indicator D9, and a power status indicator D10. The PD4 pin of the chip U5 is connected to the power indicator D9. The PD5 pin of the chip U5 is connected to the power status indicator D10. The PD3 pin of the chip U5 is connected to the voltage comparison circuit. The PC4 pin of the chip U5 is the output of the modulated PWM signal.

[0022] Further, the LED driving circuit includes an NPN transistor Q2, a current limiting resistor R13, and a bypass capacitor C14. The PC4 pin of the chip U5 is connected to the NPN transistor Q2 through a resistor R15. The NPN transistor Q2 is connected to an LED diode D6. The LED diode D6 is connected to a capacitor C14 and a resistor R13.

[0023] Compared with the prior art, the present utility model has the following beneficial effects: The acquisition module provided by the present utility model is used to receive and convert the reflected light signal of the target object. Subsequently, the differential amplification circuit amplifies and converts the PD signal received by the acquisition signal. Then, the analog signal is converted into a pulse signal through the voltage comparison circuit. In this way, the MCU control circuit can process the logic signal and modulate the PWM signal, and the LED driving circuit is provided to drive the LED diode D6 to work. The background suppression photoelectric sensor realized by the provided photodiode PD1, photodiode PD2, differential amplification circuit, voltage comparison circuit, and MCU control circuit adopts an automatic frequency conversion technology to solve the problem of optical crosstalk between multiple sensors and is applicable to background suppression photoelectric sensing. Description of the Drawings

[0024] Figure 1 It is a schematic diagram of the system principle of the present utility model;

[0025] Figure 2 It is a schematic diagram of the circuit structure of the system of the present utility model;

[0026] Figure 3 It is a schematic diagram of the circuit structure of the acquisition module and the differential amplification circuit of the present utility model;

[0027] Figure 4 It is a schematic diagram of the circuit structure of the ignition comparison circuit of the present utility model;

[0028] Figure 5 It is a schematic diagram of the circuit structure of the MCU control circuit of the present utility model;

[0029] Figure 6 It is a schematic diagram of the circuit structure of the LED driving circuit of the present utility model;

[0030] Figure 7 It is a schematic diagram of the circuit structure of the adaptive output circuit of the present utility model. Detailed Embodiments

[0031] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. Based on the embodiments of the present utility model, those of ordinary skill in the art

[0032] All other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present utility model.

[0033] Please refer to Figures 1-7 , the present utility model provides a technical solution: a background suppression photoelectric sensor based on dual PD, including an MCU control circuit, an LED driving circuit, a collection module, a target object, a differential amplification circuit, a voltage comparison circuit, and an adaptive output circuit;

[0034] The collection module includes an LED diode D6, a photodiode PD1, and a photodiode PD2. A lens is provided on one side of the LED diode D6, and lenses are also provided for the photodiode PD1 and the photodiode PD2. The output end of the LED driving circuit is connected to the LED diode D6. The target object is arranged in front of the LED diode D6, the photodiode PD1, and the photodiode PD2. The photodiode PD1 and the photodiode PD2 receive the reflected light of the target object. The photodiode PD1 and the photodiode PD2 are electrically connected to the input end of the differential amplification circuit. The output end of the differential amplification circuit is connected to the input end of the MCU control circuit through the voltage comparison circuit. The output end of the MCU control circuit is connected to the input end of the LED driving circuit. Another output end of the MCU control circuit is connected to the adaptive output circuit;

[0035] The collection module is used for receiving and converting the reflected light signal of the target object;

[0036] The differential amplification circuit is used for amplifying and converting the PD signal received by the collection signal;

[0037] The voltage comparison circuit is used for converting the analog signal into a pulse signal;

[0038] The MCU control circuit is used for logic signal processing and PWM signal modulation;

[0039] The LED driving circuit is used for driving the LED diode D6 to work;

[0040] The adaptive output circuit is used for outputting the logic signal processed by the MCU control circuit.

[0041] Among them, the set acquisition module is used to receive and convert the reflected light signal of the target object. Subsequently, the differential amplification circuit amplifies and converts the PD signal received by the acquisition signal. Then, the voltage comparison circuit converts the analog signal into a pulse signal. In this way, the MCU control circuit can process the logic signal and modulate the PWM signal, and the set LED drive circuit drives the LED diode D6 to work. The background suppression photoelectric sensor implemented by the set photodiode PD1, photodiode PD2, differential amplification circuit, voltage comparison circuit, and MCU control circuit adopts an automatic frequency conversion technology to solve the problem of optical crosstalk between multiple sensors and is applicable to background suppression photoelectric sensing.

[0042] During use, the MCU control circuit modulates a PWM signal with a voltage of 8 kHz and a duty cycle of 90% and sends it to the LED drive circuit. The LED drive circuit drives the LED diode D6 to emit light. The frequency of this light is the same as the signal modulated by the MCU control circuit. The light emitted by the LED diode D6 is collimated by a lens and then irradiated onto the target object. The light emitted by the LED diode D6 forms a diffuse reflection light at the target object. Another group of lenses converges the light to form a light spot and irradiates it at the positions of the photodiode PD1 and the photodiode PD2. The change in the position of the light spot will cause the light signal intensities received by a set of proximally arranged photodiode PD1 and distally arranged photodiode PD2 to change, thereby forming two electrical signals with inconsistent intensities. At this time, the differential amplification circuit receives the electrical signals of the photodiode PD1 and the photodiode PD2 and performs differential amplification on the two, and it can be obtained that the current position of the light spot is at the photodiode PD1 and the photodiode PD2, so as to obtain the relative position of the target object from the photodiode PD1 and the photodiode PD2.

[0043] What the differential amplification circuit amplifies is a voltage signal, which is compared with the reference voltage of the voltage comparison circuit. When the voltage of the differential amplification circuit is less than the reference voltage of the voltage comparison circuit, it means that the signal of the photodiode PD1 is greater than the signal of the photodiode PD2. At this time, the detected target object is the background. When the voltage of the differential amplification circuit is greater than the reference voltage of the point smoke comparison circuit, it means that the signal of the photodiode PD1 is less than the signal of the photodiode PD2. At this time, what is detected is the target object.

[0044] Anti-optical crosstalk principle: When the voltage of the differential amplification circuit is less than the reference voltage of the voltage comparison circuit, that is, when the detected object is the background of the target, the MCU control circuit modulates a PWM signal of 8 kHz. When the voltage of the differential amplification circuit is greater than the reference voltage of the voltage comparison circuit, that is, when the detected object is the target, the MCU control circuit modulates a PWM signal of 12 kHz, and uses the frequency difference to distinguish the stray light reflected by adjacent sensors.

[0045] Please refer to Figure 1 、 Figure 2 、 Figure 3 、Figure 4 and Figure 5 The photodiodes PD1 and PD2 are connected with a resistor R2 and a capacitor C4. The photodiodes PD1 and PD2 are respectively connected with a resistor R9 and a resistor R10. A capacitor C5 and a capacitor C9 are respectively connected between the photodiode PD1 and the resistor R9 and between the photodiode PD2 and the resistor R10. A reference voltage REF1 is further included. The reference voltage REF1 includes a resistor R5, a resistor R8 and a capacitor C10. The resistor R5 is connected with the resistor R8. The resistor R8 is connected with the capacitor C10. The differential amplifier circuit includes an amplifier U2.1, an amplifier U2.2, a resistor R3, a capacitor C1, a resistor R11, a capacitor C11, a capacitor C13, a resistor R1, a capacitor C2. The reference voltage REF1 is loaded to the positive terminals of the amplifier U2.1 and the amplifier U2.2. The amplifier U2.1 is connected with the resistor R3 and the capacitor C1. The capacitor C5 is connected with the negative terminal of the amplifier U2.1. The capacitor C9 is connected with the positive terminal of the amplifier U2.1. The capacitor C9 is connected with the capacitor C11 and the resistor R11. A capacitor C7 and a resistor R6 are connected between the amplifier U2.1 and the amplifier U2.2. The amplifier U2.2 is connected with the resistor R1 and the capacitor C2. The signal amplified by the amplifier U2.1 is input into the amplifier U2.2 for secondary amplification through the capacitor C7 and the resistor R2. The amplifier U2.2 is connected with the resistor R7. A diode D1 and a diode D2 are further included. The diode D1 is set in the forward direction. The diode D2 is set in the reverse direction. The diode D1 and the diode D2 form an amplitude circuit and are connected with the capacitor C2.

[0046] Among them, the resistor R2, the photodiodes PD1 and PD2, the capacitor C4, the resistor R9, the resistor R10 form a collection module to realize the conversion of optical signals. The DC components of the photodiodes PD1 and PD2 are filtered out by the isolation capacitors C5 and C9. The resistor R5, the resistor R8, the capacitor C10 form a reference voltage. This reference voltage is loaded to the positive terminal of the comparator U2.1 and the positive terminal of the comparator U2.2 to bias the signal with the reference voltage REF1. The comparator U2.1, the resistor R3, the capacitor C1, the resistor R11, the capacitor C11 and the capacitor C13 form a differential amplifier circuit. The comparator U2.2, the resistor R1 and the capacitor C2 form a secondary amplifier circuit. The diode D1 and the diode D2 are respectively set in the forward and reverse directions to form a limiting circuit. The signals at the positive and negative terminals of the comparator U2.1 are input by the capacitors C5 and C9. After being differentially amplified by the comparator U2.1, they are input into the comparator U2.2 through the capacitor C7 and the resistor R2 for secondary amplification. The amplified signal is output by the resistor R7.

[0047] Please refer to Figure 1 、 Figure 2 、 Figure 3 andFigure 4 , the voltage comparison circuit includes a low-voltage comparator U7, a resistor R22, a resistor R21, and a capacitor C17. The amplified signal of the amplifier U2.2 is input to the positive terminal of the low-voltage comparator U7 through the resistor R7. The resistor R22 is connected to the resistor R21, and the resistor R21 is connected with a capacitor C17. The resistor R22, the resistor R21, and the capacitor C17 form a reference voltage REF2 and are connected to the negative terminal of the low-voltage comparator U7.

[0048] Among them, the amplified signal of the comparator U2.2 is input to the positive terminal of the low-voltage comparator U7, while the resistor R22, the resistor R21, and the capacitor C17 generate a path of reference voltage and transmit it to the negative terminal of the low-voltage comparator U7. When the input voltage of the IN1+ pin of the low-voltage comparator U7 is greater than the reference voltage REF2, the OUT pin of the low-voltage comparator U7 outputs a low level. When the input voltage of the IN1+ pin of U7 is less than the reference voltage REF2, the OUT pin of U7 outputs a high level, thereby realizing the conversion of the square-wave signal.

[0049] Please refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 , the MCU control circuit includes a chip U5, a power indicator D9, and a power status light D10. The PD4 pin of the chip U5 is connected with the power indicator D9, the PD5 pin of the chip U5 is connected with the power status light D10, the PD3 pin of the chip U5 is connected to the voltage comparison circuit, and the PC4 pin of the chip U5 is the output of the modulated PWM signal.

[0050] Among them, the set power indicator D9 can indicate the power situation of the entire device, and the setting of the power status light D10 can display the working state of the entire device.

[0051] Please refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 , the LED driving circuit includes an NPN transistor Q2, a current-limiting resistor R13, and a bypass capacitor C14. The PC4 pin of the chip U5 is connected with the NPN transistor Q2 through a resistor R15. The NPN transistor Q2 is connected to the LED diode D6, and the LED diode D6 is connected with a capacitor C14 and a resistor R13.

[0052] Among them, the PWM signal generated by the chip U5 is input through the resistor R15 to control the base of the NPN transistor Q2 to turn the NPN transistor Q2 on or off, thereby controlling the on or off of the LED diode D6.

[0053] Please refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 , the adaptive output circuit includes an NPN output triode Q1, a PNP output triode Q3, a unidirectional diode D5, a TVS protection diode D8, and a current-limiting fuse U4. The PA3 pin of the chip U2 is connected to the PNP output triode Q2 through a resistor R17. The PNP output triode Q2 is connected to a unidirectional diode D5. The unidirectional diode D5 is connected to the NPN output triode Q1. The NPN output triode Q1 is connected to a resistor R14. The unidirectional diode D5 is connected to a current-limiting fuse U4. A TVS protection diode D8 is connected between the current-limiting fuse U4 and the unidirectional diode D5.

[0054] Among them, the output of the adaptive output circuit includes NPN output and PNP output;

[0055] NPN output: When OUT is at a high level, the PNP output triode Q3 conducts, and the unidirectional diode D5 conducts to pull down the emitter of the NPN output triode Q1. At this time, the current-limiting fuse U4 outputs a low-level signal;

[0056] PNP output. When OUT is at a low level, the PNP output triode Q3 is cut off, the unidirectional diode D5 is cut off, the resistor R14 pulls up, the base of the NPN output triode Q1 is at a high level, and the NPN output triode Q1 conducts. At this time, the current-limiting fuse U4 outputs a high-level signal.

[0057] In use, first, the set acquisition module is used to receive and convert the reflected light signal of the target object. Subsequently, the differential amplification circuit amplifies and converts the PD signal received by the acquisition signal. Then, the analog signal is converted into a pulse signal through the voltage comparison circuit. In this way, the MCU control circuit can process the logic signal and modulate the PWM signal, and the set LED driver circuit drives the LED diode D6 to work. The background suppression photoelectric sensor implemented by the set photodiode PD1, photodiode PD2, differential amplification circuit, voltage comparison circuit, and MCU control circuit adopts an automatic frequency conversion technology to solve the problem of optical crosstalk between multiple sensors and is applicable to background suppression photoelectric sensing. When in use, the MCU control circuit modulates a PWM signal with a voltage of 8 kHz and a duty cycle of 90% and sends it to the LED driver circuit. The LED driver circuit drives the LED diode D6 to emit light. The frequency of this light is consistent with the signal modulated by the MCU control circuit. The light emitted by the LED diode D6 is collimated by a lens and then directed towards the target object. The light emitted by the LED diode D6 forms a diffuse reflection light at the target object. Another set of lenses converges the light to form a light spot and irradiates it at the positions of the photodiode PD1 and the photodiode PD2. The change in the position of the light spot will cause the light signal intensities received by the set of proximal photodiode PD1 and the distal photodiode PD2 to change, thereby forming two electrical signals with inconsistent intensities. At this time, the differential amplification circuit receives the electrical signals of the photodiode PD1 and the photodiode PD2 and performs differential amplification on the two, and it can be obtained that the current position of the light spot is at the photodiode PD1 and the photodiode PD2, thereby obtaining the relative position of the target object from the photodiode PD1 and the photodiode PD2.

[0058] The signal obtained after amplification by the differential amplification circuit is a voltage signal, which is compared with the reference voltage of the voltage comparison circuit. When the voltage of the differential amplification circuit is less than the reference voltage of the voltage comparison circuit, it means that the signal of the photodiode PD1 is greater than the signal of the photodiode PD2. At this time, the detected target object is the background. When the voltage of the differential amplification circuit is greater than the reference voltage of the voltage comparison circuit, it means that the signal of the photodiode PD1 is less than the signal of the photodiode PD2. At this time, the detected object is the target object.

[0059] Principle of anti-optical crosstalk: When the voltage of the differential amplification circuit is less than the reference voltage of the voltage comparison circuit, that is, when the detected object is the background of the target object, the MCU control circuit modulates a PWM signal of 8 kHz. When the voltage of the differential amplification circuit is greater than the reference voltage of the voltage comparison circuit, that is, when the detected object is the target object, the MCU control circuit modulates a PWM signal of 12 kHz, and uses the frequency difference to distinguish the stray light reflected by adjacent sensors.

[0060] Although embodiments of the present utility model have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present utility model. The scope of the present utility model is defined by the appended claims and their equivalents.

Claims

1. A background suppression photoelectric sensor based on dual PD, characterized in that: It includes an MCU control circuit, an LED drive circuit, a collection module, a target object, a differential amplifier circuit, a voltage comparison circuit, and an adaptive output circuit; The collection module includes an LED diode D6, a photodiode PD1, and a photodiode PD2. A lens is provided on one side of the LED diode D6, and lenses are also provided on the photodiode PD1 and the photodiode PD2. The output end of the LED drive circuit is connected to the LED diode D6. The target object is arranged in front of the LED diode D6, the photodiode PD1, and the photodiode PD2. The photodiode PD1 and the photodiode PD2 receive the reflected light of the target object. The photodiode PD1 and the photodiode PD2 are electrically connected to the input end of the differential amplifier circuit. The output end of the differential amplifier circuit is connected to the input end of the MCU control circuit through the voltage comparison circuit. The output end of the MCU control circuit is connected to the input end of the LED drive circuit. Another output end of the MCU control circuit is connected to the adaptive output circuit; The collection module is used for receiving and converting the reflected light signal of the target object; The differential amplifier circuit is used for amplifying and converting the PD signal received by the collection signal; The voltage comparison circuit is used for converting the analog signal into a pulse signal; The MCU control circuit is used for logic signal processing and PWM signal modulation; The LED drive circuit is used for driving the LED diode D6 to work; The adaptive output circuit is used for outputting the logic signal processed by the MCU control circuit.

2. The background suppression photoelectric sensor implemented based on dual PD according to claim 1, characterized in that: The photodiode PD1 and the photodiode PD2 are connected with a resistor R2 and a capacitor C4. The photodiode PD1 and the photodiode PD2 are respectively connected with a resistor R9 and a resistor R10. Capacitors C5 and C9 are respectively connected between the photodiode PD1 and the resistor R9 and between the photodiode PD2 and the resistor R10. A reference voltage REF1 is also included. The reference voltage REF1 includes a resistor R5, a resistor R8, and a capacitor C10. The resistor R5 is connected to the resistor R8, and the resistor R8 is connected with the capacitor C10.

3. The background suppression photoelectric sensor based on dual PD according to claim 2, characterized in that: The differential amplifier circuit includes an amplifier U2.1, an amplifier U2.2, a resistor R3, a capacitor C1, a resistor R11, a capacitor C11, a capacitor C13, a resistor R1, and a capacitor C2. The reference voltage REF1 is loaded to the positive ends of the amplifier U2.1 and the amplifier U2.

2. The amplifier U2.1 is connected with the resistor R3 and the capacitor C1. The capacitor C5 is connected to the negative end of the amplifier U2.

1. The capacitor C9 is connected to the positive end of the amplifier U2.

1. The capacitor C9 is connected with the capacitor C11 and the resistor R11. A capacitor C7 and a resistor R6 are connected between the amplifier U2.1 and the amplifier U2.

2. The amplifier U2.2 is connected with the resistor R1 and the capacitor C2. The signal amplified by the amplifier U2.1 is input into the amplifier U2.2 for secondary amplification through the capacitor C7 and the resistor R2. The amplifier U2.2 is connected with the resistor R7.

4. The background suppression photoelectric sensor based on dual PD according to claim 3, characterized in that: It also includes diode D1 and diode D2. Diode D1 is forward - biased, and diode D2 is reverse - biased. Diode D1 and diode D2 form an amplitude circuit and are connected to capacitor C2.

5. The background suppression photoelectric sensor implemented based on dual PD according to claim 4, characterized in that: The voltage comparison circuit includes low - voltage comparator U7, resistor R22, resistor R21, and capacitor C17. The amplified signal of amplifier U2.2 is input to the positive terminal of low - voltage comparator U7 through resistor R7. Resistor R22 is connected to resistor R21, and resistor R21 is connected with capacitor C17. Resistor R22, resistor R21, and capacitor C17 form a reference voltage REF2 and are connected to the negative terminal of low - voltage comparator U7.

6. The background suppression photoelectric sensor based on dual PD as claimed in claim 5, characterized in that: The MCU control circuit includes chip U5, power - on indicator D9, and power - status indicator D10. The PD4 pin of chip U5 is connected to power - on indicator D9, the PD5 pin of chip U5 is connected to power - status indicator D10. The PD3 pin of chip U5 is connected to the voltage comparison circuit, and the PC4 pin of chip U5 outputs the modulated PWM signal.

7. The background suppression photoelectric sensor based on dual PD according to claim 6, characterized in that: The LED driving circuit includes NPN - type triode Q2, current - limiting resistor R13, and bypass capacitor C14. The PC4 pin of chip U5 is connected to NPN - type triode Q2 through resistor R15. NPN - type triode Q2 is connected to LED diode D6, and LED diode D6 is connected with capacitor C14 and resistor R13.

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