Photoelectric sensor for realizing light interference resistance based on modulation and demodulation technology

Abstract

The utility model relates to the technical field of photoelectric sensors, in particular to a photoelectric sensor capable of resisting light interference based on modulation-demodulation technology, which comprises a light emitter and a light receiver, and is characterized in that the light emitter can change luminance and modulate sine wave signals with fixed frequency; the light receiver receives a sine wave signal of the light emitter and a superposed light signal of an ambient light signal, the signal output end of the light receiver is connected with a band-pass filter, and the band-pass filter filters out the light signal with the frequency lower than or higher than the fixed frequency until a clean sine alternating current signal is obtained. The signal output end of the band-pass filter is connected with a peak-to-peak value detection circuit used for converting sine alternating-current signals into direct-current signals, signals of other frequencies are filtered out through the band-pass filter by means of frequency selectivity, only frequency signals modulated by the illuminator are reserved, and then the signals are converted into the direct-current signals through the peak-to-peak value detection circuit. The purpose of effectively resisting ambient light interference is achieved.

Description

Technical Field

[0001] This utility model relates to the field of photoelectric sensor technology, specifically a photoelectric sensor that achieves anti-light interference based on modulation and demodulation technology. Background Technology

[0002] A photoelectric sensor probe typically consists of a light-emitting diode (LED) and a photodetector, often referred to as a photodiode pair. Light emitted by the photodiode is reflected and eventually detected by the photodetector, generating an analog electrical signal. This analog signal is then processed and output, and can be used to detect color differences or the presence or absence of objects. It is commonly used in industrial production or in vehicle photoelectric tracking scenarios.

[0003] In traditional photoelectric sensors, ideally, the photodetector only receives light emitted by the light-emitting diode. However, in most scenarios, ambient light is also received by the photoelectric sensor, affecting the output signal and causing misjudgments. Usually, if the photoelectric sensor malfunctions, we recalibrate the sensor based on changes in ambient light to achieve accurate results again, but this consumes a lot of manpower and resources and affects normal production. Utility Model Content

[0004] The purpose of this invention is to provide a photoelectric sensor based on modulation and demodulation technology to achieve anti-light interference, so as to solve the problems mentioned in the background art.

[0005] The technical solution of this utility model is: a photoelectric sensor based on modulation and demodulation technology to achieve anti-light interference, including a light emitter and a light receiver. The light emitter can change the brightness of the light emission and modulate a sinusoidal wave signal of a fixed frequency. The light receiver receives the superimposed light signal of the sinusoidal wave signal of the light emitter and the ambient light signal. The signal output terminal of the light receiver is connected to a bandpass filter. The bandpass filter filters out light signals below or above a fixed frequency until a clean sinusoidal AC signal is obtained. The signal output terminal of the bandpass filter is connected to a peak-to-peak detection circuit for converting the sinusoidal AC signal into a DC signal.

[0006] The effect achieved by the above components is as follows: after the sinusoidal signal of the light emitter is superimposed with the ambient light signal, the bandpass filter uses frequency selectivity to filter out signals of other frequencies, retaining only the frequency signal modulated by the light emitter, which is then converted into a DC signal by the peak-to-peak detection circuit. This achieves the purpose of effectively resisting ambient light interference, increasing the stability and accuracy of the output signal of the photoelectric sensor, and avoiding misjudgment caused by the influence of ambient light.

[0007] Preferably, the bandpass filter is provided with a bandpass selective operational amplifier circuit, which consists of an operational amplifier, capacitors and resistors forming a bandpass filter network to selectively amplify spurious signals and output a clean sinusoidal AC signal.

[0008] The effect achieved by the above components is as follows: the bandpass frequency-selective operational amplifier circuit performs frequency-selective amplification of the superimposed optical signal. By utilizing the frequency selection characteristics of the bandpass filter, it suppresses other frequency signals while amplifying the target frequency signal, thereby further improving the signal purity and enhancing the sensor's ability to identify target signals and its anti-interference performance.

[0009] Preferably, the light emitter is a light-emitting diode and can be modulated to produce a sine wave of a fixed frequency, the light receiver is a photodetector, and a focusing lens or filter is provided in the optical path between the light-emitting diode and the photodetector.

[0010] The effects achieved by the above components are as follows: the fixed frequency of the light emitter modulation facilitates targeted filtering by the bandpass filter; the focusing lens enhances the signal directionality of the light-emitting diode and photodetector; and the filter weakens ambient light interference. The three components work together to reduce the interference of ambient light on sensor detection, improve the reliability and stability of sensor detection, and reduce the probability of misjudgment caused by ambient light.

[0011] Preferably, the peak-to-peak detection circuit includes a rectifier diode, a filter capacitor, and an operational amplifier.

[0012] The above components achieve the following effects: the rectifier diodes rectify the sinusoidal AC signal, the filter capacitors convert it into a DC signal, and the operational amplifiers perform level conversion and stable output. This achieves the goal of converting the sinusoidal AC signal into a DC signal familiar to the market, increasing the versatility of the sensor signal and facilitating compatibility with other devices.

[0013] Preferably, the driving circuit of the light emitter includes a frequency modulation module, which is composed of a crystal oscillator or phase-locked loop circuit and an RC sine wave oscillation circuit.

[0014] The aforementioned components achieve the following effects: the crystal oscillator or phase-locked loop circuit and the RC sine wave oscillation circuit ensure that the flashing frequency of the light-emitting diode is stable within the frequency error range of the modulation signal, avoid the bandpass filter from failing to accurately filter the signal due to frequency drift, achieve the goal of ensuring the stability of the sensor's anti-interference performance, and improve the reliability and consistency of the sensor's operation.

[0015] Preferably, a signal amplification unit is provided between the bandpass filter and the peak-to-peak detection circuit, and the signal amplification unit is composed of an operational amplifier forming an in-phase or out-of-phase amplification circuit.

[0016] The effect achieved by the above components is as follows: the signal amplification unit compensates for signal attenuation during the filtering process, ensuring that the signal strength entering the peak-to-peak detection circuit meets the conversion requirements, thereby improving the strength and quality of the sensor output signal and enhancing the sensor's sensitivity and detection performance.

[0017] This invention provides an improved photoelectric sensor based on modulation and demodulation technology to achieve anti-light interference, which has the following improvements and advantages compared with the prior art:

[0018] Firstly, this invention uses a bandpass filter to filter out signals of other frequencies by superimposing the sinusoidal signal of the light emitter with the ambient light signal, and retaining only the frequency signal modulated by the light emitter. The peak-to-peak detection circuit then converts the signal into a DC signal, thereby effectively resisting ambient light interference, increasing the stability and accuracy of the output signal of the photoelectric sensor, and avoiding misjudgments caused by ambient light.

[0019] Secondly, this utility model uses a rectifier diode to rectify the sinusoidal AC signal, a filter capacitor to convert it into a DC signal, and an operational amplifier to achieve level conversion and stable output. This achieves the purpose of converting the sinusoidal AC signal into a DC signal familiar to the market, increasing the versatility of the sensor signal and facilitating compatibility with other devices. Attached Figure Description

[0020] The present invention will be further explained below with reference to the accompanying drawings and embodiments:

[0021] Figure 1 This is a schematic diagram of signal transmission of this utility model;

[0022] Figure 2 This is a schematic diagram of the peak-to-peak detection circuit of this utility model;

[0023] Figure 3 This is a schematic diagram of the bandpass frequency-selective operational amplifier circuit of this utility model. Detailed Implementation

[0024] The present invention will now be described in detail, and the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0025] This invention provides an improved photoelectric sensor based on modulation and demodulation technology to achieve anti-light interference. The technical solution of this invention is as follows:

[0026] In embodiments of this utility model, such as Figures 1-3 As shown, a photoelectric sensor based on modulation and demodulation technology to achieve anti-light interference includes a light emitter and a light receiver. The light emitter is a light-emitting diode (LED) that can be modulated to produce a sine wave of a fixed frequency. The light receiver is a photodetector. A focusing lens or filter is provided in the optical path of the LED and the photodetector. The fixed frequency modulated by the light emitter facilitates targeted filtering by the bandpass filter. The focusing lens enhances the signal directionality of the LED and the photodetector, and the filter weakens ambient light interference. The three work together to reduce the interference of ambient light on sensor detection. The driving circuit of the light emitter includes a frequency modulation module, which consists of a crystal oscillator or phase-locked loop circuit and an RC sine wave oscillation circuit. The light emitter can change its brightness and modulate a sine wave signal of a fixed frequency. The light receiver receives the superimposed light signal of the sine wave signal from the light emitter and the ambient light signal. The signal output terminal of the light receiver is connected to a bandpass filter. The device filters out optical signals with frequencies below or above a fixed value until a clean sinusoidal AC signal is obtained. The bandpass filter contains a bandpass selective operational amplifier circuit, which consists of an operational amplifier, capacitors, and resistors forming a bandpass filter network. This circuit selectively amplifies stray signals and outputs a clean sinusoidal AC signal. The bandpass selective operational amplifier circuit also selectively amplifies superimposed optical signals. Utilizing the frequency selection characteristics of the bandpass filter, it suppresses other frequency signals while amplifying the target frequency signal, thus further improving signal purity. The signal output terminal of the bandpass filter is connected to a peak-to-peak value detection circuit for converting the sinusoidal AC signal into a DC signal. This peak-to-peak value detection circuit includes a rectifier diode, a filter capacitor, and an operational amplifier. The rectifier diode rectifies the sinusoidal AC signal, the filter capacitor converts it into a DC signal, and the operational amplifier performs level conversion and stable output, achieving the goal of converting the sinusoidal AC signal into a familiar DC signal.

[0027] The working principle of the photoelectric sensor based on modulation and demodulation technology for anti-light interference provided by this utility model is as follows: The light-emitting diode (LED) flashes light according to the modulation frequency, while the ambient light is a relatively stable light signal. These two light signals are superimposed and detected by the photodetector, generating a spurious electrical signal. This signal passes through a bandpass filter composed of operational amplifiers to obtain a pure sine wave. At this point, low-frequency ambient light and spurious signals higher than the modulation signal have been eliminated. This achieves anti-light interference technology. However, since the familiar signal in the market is a DC signal, the sinusoidal AC signal is converted by a peak-to-peak detection circuit composed of operational amplifiers, outputting a DC signal, thus obtaining the same signal as familiar products in the market, thereby achieving anti-light interference technology.

[0028] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A photoelectric sensor based on modulation and demodulation technology to achieve anti-light interference, comprising a emitter and a receiver, characterized in that: The emitter can change its brightness and modulate a sinusoidal signal of a fixed frequency. The receiver receives the superimposed light signal of the sinusoidal signal from the emitter and the ambient light signal. The signal output terminal of the receiver is connected to a bandpass filter. The bandpass filter filters out light signals with frequencies lower or higher than a fixed frequency until a clean sinusoidal AC signal is obtained. The signal output terminal of the bandpass filter is connected to a peak-to-peak detection circuit for converting the sinusoidal AC signal into a DC signal.

2. The photoelectric sensor based on modulation and demodulation technology to achieve anti-optical interference according to claim 1, characterized in that: The bandpass filter is equipped with a bandpass frequency-selective operational amplifier circuit. The bandpass frequency-selective operational amplifier circuit consists of an operational amplifier, capacitors, and resistors forming a bandpass filter network, which selectively amplifies stray signals and outputs a clean sinusoidal AC signal.

3. A photoelectric sensor based on modulation and demodulation technology to achieve anti-optical interference according to claim 1, characterized in that: The light emitter is a light-emitting diode that can be modulated to produce a sine wave of a fixed frequency. The light receiver is a photodetector. A focusing lens or filter is provided in the optical path between the light-emitting diode and the photodetector.

4. A photoelectric sensor based on modulation and demodulation technology to achieve anti-optical interference according to claim 1, characterized in that: The peak-to-peak detection circuit includes a rectifier diode, a filter capacitor, and an operational amplifier.

5. The photoelectric sensor of claim 1, wherein: the modulation technique is a frequency shift keying (FSK) modulation technique. The driving circuit of the light emitter includes a frequency modulation module, which consists of a crystal oscillator or phase-locked loop circuit and an RC sine wave oscillation circuit.

6. The photoelectric sensor of claim 1, wherein: A signal amplification unit is provided between the bandpass filter and the peak-to-peak detection circuit. The signal amplification unit is composed of an operational amplifier forming an in-phase or out-of-phase amplifier circuit.

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