CN117955482A - Circuit and method for actively eliminating light path noise - Google Patents
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Abstract
The invention belongs to the technical field of photoelectric sensing, and particularly relates to a circuit and a method for actively eliminating light path noise, wherein the circuit comprises an optical part, a hardware part and an algorithm part; the optical part is an optical channel P (z) from ambient light noise and light path noise to the photoelectric detector, and comprises a light source module and a photoelectric detector acquisition module, which are used for generating optical signals and receiving the optical signals and generating photocurrent; the hardware part is a path S (z) from an output signal to a return residual signal and comprises a circuit amplification filter, an ADC circuit, a DAC circuit, a hardware coupling circuit and a filter; the circuit amplification filter also comprises an amplification circuit and a filter circuit, and is used for amplifying the detected weak electric signal and performing primary filtering noise reduction treatment. The invention can autonomously eliminate noise in real time, thereby obtaining accurate signals to be detected, improving the reliability and sensitivity of the sensor and solving the problem of noise interference generated by ambient light and an optical path structure.
Description
Technical Field
The invention belongs to the technical field of photoelectric sensing, and particularly relates to a circuit and a method for actively eliminating light path noise.
Background
Photoelectric sensors are widely used, and the main principle is to convert the change of optical signals into the change of electric signals so as to realize the sensing function. The variations of the optical signal mainly include variations of the intensity, frequency and phase of the light. The photoelectric sensor is composed of three parts, including: a transmitter, a receiver and a detection circuit. The function of the transmitter is to aim the target to emit a light beam, which is typically derived from a semiconductor light source, a Light Emitting Diode (LED), a laser diode, and an infrared emitting diode. The beam is emitted without interruption or the pulse width is changed.
The receiver is generally composed of a photodiode, a phototriode and a photocell, and has the function of converting an optical signal into an electrical signal and transmitting the electrical signal to the next stage. Between the transmitter and the receiver, an optical path structure is generally designed in the form of an optical trap structure, an optical element such as a lens, an aperture, and the like. The detection circuit has signal processing functions such as weak signal amplification, filtering and the like.
The current common problems with various sensors are:
1. The influence of ambient light is large, and false alarm is easy to generate;
2. The ambient light noise changes in real time and has a large change range, so that the noise is very difficult to eliminate;
3. the influence of the noise of the optical path structure is larger, and the noise of the optical path structure and the signal to be detected are mixed together and cannot be distinguished;
the above problems limit the use conditions and use cases of the photoelectric sensor.
Disclosure of Invention
The invention aims to provide a circuit and a method for actively eliminating light path noise, which can automatically eliminate noise in real time, so as to obtain an accurate signal to be measured, improve the reliability and sensitivity of a sensor and solve the problem of noise interference generated by ambient light and a light path structure.
The technical scheme adopted by the invention is as follows:
A circuit for actively eliminating optical path noise comprises an optical part, a hardware part and an algorithm part;
The optical part is an optical channel P (z) from ambient light noise and light path noise to the photoelectric detector, and comprises a light source module and a photoelectric detector acquisition module, which are used for generating optical signals and receiving the optical signals and generating photocurrent;
The light source module further comprises a semiconductor light source, a light emitting diode, a laser diode and an infrared emitting diode;
The photoelectric detector acquisition module further comprises a photodiode and a photoresistor;
the hardware part is a path S (z) from an output signal to a return residual signal and comprises a circuit amplification filter, an ADC circuit, a DAC circuit, a hardware coupling circuit and a filter;
the circuit amplification filter also comprises an amplification circuit and a filter circuit, and is used for amplifying the detected weak electric signal and performing primary filtering noise reduction treatment;
the ADC circuit is used for reading the amplitude value of the output signal of the front-end circuit;
the DAC circuit is used for outputting the operated signal;
The filter is used for filtering and denoising the output signal;
the hardware coupling circuit is used for connecting two paths of signals to generate an error signal;
the algorithm part adopts FxLMS algorithm.
The output signal of the amplifying filter and the output signal of the filter are used as two paths of input signals of a hardware coupling circuit.
The hardware coupling circuit comprises a first-stage matching resistor, a second-stage matching resistor, a first-stage feedback resistor, a second-stage feedback resistor, an inverting operational amplifier, a third-stage matching resistor, an inverting superposition operational circuit, a first-stage balance resistor and a second-stage balance resistor;
The first end of the second-stage matching resistor is electrically connected with the output end of the amplifying filter, the second end of the second-stage matching resistor is electrically connected with the first input end of the inverting operational amplifier, the first input end of the inverting operational amplifier is electrically connected with the first end of the first-stage feedback resistor, the second input end of the inverting operational amplifier is electrically connected with the first end of the first-stage balancing resistor, the second end of the first-stage balancing resistor is grounded, and the output end of the inverting operational amplifier is electrically connected with the second end of the first-stage feedback resistor and the first end of the third-stage matching resistor;
The first end of the first stage matching resistor is electrically connected with the output end of the amplifying filter, the second end of the first stage matching resistor is electrically connected with the first input end of the inverse superposition operation circuit, the first input end of the inverse superposition operation circuit is electrically connected with the first end of the second stage feedback resistor and the second end of the third stage matching resistor, the second input end of the inverse superposition operation circuit is electrically connected with the first end of the second stage balancing resistor, the second end of the second stage balancing resistor is grounded, and the output end of the inverse superposition operation circuit is electrically connected with the second end of the second stage feedback resistor.
The output signal of the amplifying filter is subjected to an inverting operational amplifier to obtain a first-stage output signal-U i2;
The output signal of the first stage and the output signal of the filter are used as the input signal of the second stage inverse superposition operation circuit together to obtain an output signal U O＝-(UO1+Ui1)＝Ui2-Ui1.
A method of actively canceling optical path noise, the canceling optical path noise comprising the steps of:
s1: dividing ambient light noise and light path noise into two paths of PD receivers for receiving to obtain a first path of signals and a second path of signals;
S2: amplifying and filtering the first path of signals by a hardware circuit to obtain amplified and filtered signals; the signals are collected through an ADC collecting circuit and are transmitted to an active noise reduction kernel module to be used as input signals x (n);
s3: the second path of signals are amplified and filtered by a hardware circuit amplification filter to obtain amplified and filtered signals; after the signal is coupled with the output signal of the filter through a hardware circuit, the signal is collected through an ADC collecting circuit and is transmitted to an active noise reduction kernel module, and the signal is an error signal e (n);
S4: the active noise reduction module inputs a signal x (n) and an error signal e (n) and outputs a signal y (n) after an FxLMS algorithm;
s5: and the signal y (n) output by the active noise reduction kernel module is output to a filter through a DAC circuit, and the filtered signal is output to a hardware coupling module for coupling after the filter.
In the step S4, based on the FxLMS algorithm, when the signal x (n) is input, after the signal is processed, each parameter is as follows:
d (n) is an expected value of x (n) after passing through P (z); e (n) is an error signal;
The objective function of the LMS is the square of the instantaneous error, e 2(n)＝(d(n)-y(n))2.
The FxLMS adopts a noise reduction kernel algorithm and comprises an adaptive filter, when each y (n) is generated, the weight coefficient w (n) is updated through a least mean square algorithm, namely, the FxLMS is automatically and continuously adapted to a given signal, the expected response is obtained, the residual signal is minimized, and the adaptive filtering is completed;
The FxLMS algorithm comprises the following operation steps:
S11: when the signal x (n) is input, the signal passes through ambient light noise and light path noise to an optical channel P (z) system of the PD and then outputs an expected value signal d (n);
S22: the signal x (n) passes through the adaptive filter W (z) and then outputs the y (n), and the signal y (n) passes through the path S (z) for returning the residual signal and then outputs the signal y' (n);
S33: the signal x (n) is processed by an S ^ (z) system to obtain a filtered-x signal v (n), and the v (n) and an error signal e (n) are input into an LMS algorithm system together to output a signal;
s44: the output signal y' (n) and the expected value signal d (n) are input into a hardware coupling circuit together to obtain an error signal e (n).
The invention has the technical effects that:
According to the circuit and the method for actively eliminating the light path noise, the sensor can automatically eliminate the noise in real time according to the method, so that an accurate signal to be measured is obtained, the reliability and the sensitivity of the sensor are improved, and the noise interference problem generated by the ambient light and the light path structure is solved. Meanwhile, a hardware coupling method is adopted, so that the system cost is reduced.
The circuit and the method for actively eliminating the optical path noise creatively propose to apply the FxLMS algorithm to the optical path noise reduction scheme of the photoelectric sensor, the algorithm can realize self-adaptive noise elimination, solve the problem that noise generated by ambient light and an optical path structure has great influence on the performance of the sensor, skillfully eliminate the optical path noise, break the coupling mode of signals in the traditional FxLMS algorithm and adopt hardware circuit coupling.
Drawings
FIG. 1 is a block diagram of the overall structure of an embodiment of the present invention;
FIG. 2 is a system block diagram of an FxLMS algorithm of an embodiment of the present invention;
Wherein, P (z): an optical path from ambient light noise and optical path noise to the PD; w (z): an adaptive filter; s (z): a path for outputting a signal to return a residual signal; s ^ (z): is an approximate estimate of the S (z) system;
FIG. 3 is a schematic diagram of a hardware coupling circuit according to an embodiment of the invention;
fig. 4 is a data diagram of Matlab software validation in accordance with an embodiment of the present invention.
In the drawings, the list of components represented by the various numbers is as follows:
601. A first stage matching resistor; 602. a second stage matching resistor; 603. a first stage feedback resistor; 604. a second stage feedback resistor; 605. an inverting operational amplifier; 606. a third stage matching resistor; 607. an inverse superposition operation circuit; 608. a first stage balancing resistor; 609. and a second stage balancing resistor.
Detailed Description
The present invention will be specifically described with reference to examples below in order to make the objects and advantages of the present invention more apparent. It should be understood that the following text is intended to describe only one or more specific embodiments of the invention and does not limit the scope of the invention strictly as claimed.
Example 1:
As shown in fig. 1-3, a circuit for actively eliminating optical path noise comprises an optical part, a hardware part and an algorithm part;
The optical part is an optical channel P (z) from ambient light noise and light path noise to the photoelectric detector, and comprises a light source module and a photoelectric detector acquisition module, which are used for generating optical signals and receiving the optical signals and generating photocurrent;
The light source module further comprises a semiconductor light source, a light emitting diode, a laser diode and an infrared emitting diode;
The photoelectric detector acquisition module further comprises a photodiode and a photoresistor;
the hardware part is a path S (z) from an output signal to a return residual signal and comprises a circuit amplification filter, an ADC circuit, a DAC circuit, a hardware coupling circuit and a filter;
the circuit amplification filter also comprises an amplification circuit and a filter circuit, and is used for amplifying the detected weak electric signal and performing primary filtering noise reduction treatment;
the ADC circuit is used for reading the amplitude value of the output signal of the front-end circuit;
the DAC circuit is used for outputting the operated signal;
The filter is used for filtering and denoising the output signal;
the hardware coupling circuit is used for connecting two paths of signals to generate an error signal;
the algorithm part adopts FxLMS algorithm.
The output signal of the amplifying filter and the output signal of the filter are used as two paths of input signals of a hardware coupling circuit.
The hardware coupling circuit comprises a first-stage matching resistor 601, a second-stage matching resistor 602, a first-stage feedback resistor 603, a second-stage feedback resistor 604, an inverting operational amplifier 605, a third-stage matching resistor 606, an inverting superposition operational circuit 607, a first-stage balancing resistor 608 and a second-stage balancing resistor 609;
The first end of the second-stage matching resistor 602 is electrically connected with the output end of the amplifying filter, the second end of the second-stage matching resistor 602 is electrically connected with the first input end of the inverting operational amplifier 605, the first input end of the inverting operational amplifier 605 is electrically connected with the first end of the first-stage feedback resistor 603, the second input end of the inverting operational amplifier 605 is electrically connected with the first end of the first-stage balancing resistor 608, the second end of the first-stage balancing resistor 608 is grounded, and the output end of the inverting operational amplifier 605 is electrically connected with the second end of the first-stage feedback resistor 603 and the first end of the third-stage matching resistor 606;
the first end of the first stage matching resistor 601 is electrically connected with the output end of the amplifying filter, the second end of the first stage matching resistor 601 is electrically connected with the first input end of the inverse superposition operation circuit 607, the first input end of the inverse superposition operation circuit 607 is electrically connected with the first end of the second stage feedback resistor 604 and the second end of the third stage matching resistor 606, the second input end of the inverse superposition operation circuit 607 is electrically connected with the first end of the second stage balancing resistor 609, the second end of the second stage balancing resistor 609 is grounded, and the output end of the inverse superposition operation circuit 607 is electrically connected with the second end of the second stage feedback resistor 604.
The output signal of the amplifying filter is subjected to an inverting operational amplifier to obtain a first-stage output signal-U i2;
The output signal of the first stage and the output signal of the filter are used as the input signal of the second stage inverse superposition operation circuit together to obtain an output signal U O＝-(UO1+Ui1)＝Ui2-Ui1, so that differential operation of signals is realized.
The hardware coupling circuit has a multiple amplifying function and can be matched with a noise reduction kernel algorithm FxLMS algorithm to carry out parameter adjustment.
Example 2:
A method of actively canceling optical path noise, the canceling optical path noise comprising the steps of:
s1: dividing ambient light noise and light path noise into two paths of PD receivers for receiving to obtain a first path of signals and a second path of signals;
S2: amplifying and filtering the first path of signals by a hardware circuit to obtain amplified and filtered signals; the signals are collected through an ADC collecting circuit and are transmitted to an active noise reduction kernel module to be used as input signals x (n);
s3: the second path of signals are amplified and filtered by a hardware circuit amplification filter to obtain amplified and filtered signals; after the signal is coupled with the output signal of the filter through a hardware circuit, the signal is collected through an ADC collecting circuit and is transmitted to an active noise reduction kernel module, and the signal is an error signal e (n);
S4: the active noise reduction module inputs a signal x (n) and an error signal e (n) and outputs a signal y (n) after an FxLMS algorithm;
s5: and the signal y (n) output by the active noise reduction kernel module is output to a filter through a DAC circuit, and the filtered signal is output to a hardware coupling module for coupling after the filter.
In the step S4, based on the FxLMS algorithm, when the signal x (n) is input, after the signal is processed, each parameter is as follows: d (n) is an expected value of x (n) after passing through P (z); e (n) is an error signal;
The objective function of the LMS is the square of the instantaneous error, e 2(n)＝(d(n)-y(n))2. To minimize the objective function, gradient descent is applied to it to get an updated formula for the algorithm. The update formula of the LMS algorithm using FIR filters is: w (n+1) =w (n) - μe (n) x (n), where μ is the step size.
The FxLMS algorithm ensures the convergence characteristic of LMS, and x (n) is input to the LMS module after S (z), wherein S (z) is the estimation of S (z).
e2(n)＝(d(n)-s(n)*[WT(n)x(n)])2
The gradient is obtained:
gradient＝-2e(n)s(n)*x(n)
The updated formula for FXLMS is:
w(n+1)＝w(n)-2μe(n)v(n)
wherein v (n) =s (n) ×x (n).
When the adaptive filter W (z) converges, E (z) =x (z) P (z) -X (z) W (z) S (z) ≡0, thereforeThe weight coefficients of the adaptive filter are determined by P (z) and S (z). The optical channels and hardware parts of the system are relatively stable, so the weighting coefficients of the filters are also relatively stable.
The FxLMS adopts a noise reduction kernel algorithm and comprises an adaptive filter, when each y (n) is generated, the weight coefficient w (n) is updated through a least mean square algorithm, namely, the FxLMS is automatically and continuously adapted to a given signal, the expected response is obtained, the residual signal is minimized, and the adaptive filtering is completed; the algorithm can well eliminate ambient light noise and light path structure noise.
Example 3:
as shown in fig. 4, based on the embodiment 2, this embodiment makes further verification for FxLMS algorithm:
The FxLMS algorithm comprises the following operation steps:
S11: when the signal x (n) is input, the signal passes through ambient light noise and light path noise to an optical channel P (z) system of the PD and then outputs an expected value signal d (n);
S22: the signal x (n) passes through the adaptive filter W (z) and then outputs the y (n), and the signal y (n) passes through the path S (z) for returning the residual signal and then outputs the signal y' (n);
S33: the signal x (n) is processed by an S (z) system to obtain a filtered-x signal v (n), and the v (n) and an error signal e (n) are input into an LMS algorithm system together to output a signal;
s44: the output signal y' (n) and the expected value signal d (n) are input into a hardware coupling circuit together to obtain an error signal e (n).
After Matlab software verification, the operation results of the embodiment are as follows:
the primary noise is set as broadband and narrowband composite noise, the blue curve is the original noise power spectrum density curve, the red curve is the noise power spectrum density curve after active noise reduction, and the measured noise is attenuated by 15.6dB after calculation.
Through the process, the method for actively eliminating the light path noise is realized, the influence of the ambient light and the light path structure noise on the photoelectric sensor is eliminated, and the signal to be detected can be detected more accurately; the method can also detect weak signals submerged in noise, so that the sensitivity and resolution of the sensor are improved; and the hardware circuit coupling mode is adopted, so that the cost is reduced.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention. Structures, devices and methods of operation not specifically described and illustrated herein, unless otherwise indicated and limited, are implemented according to conventional means in the art.
Claims (8)
1. The circuit for actively eliminating the light path noise is characterized in that: comprises an optical part, a hardware part and an algorithm part;
The optical part is an optical channel P (z) from ambient light noise and light path noise to the photoelectric detector, and comprises a light source module and a photoelectric detector acquisition module, which are used for generating optical signals and receiving the optical signals and generating photocurrent;
the hardware part is a path S (z) from an output signal to a return residual signal and comprises a circuit amplification filter, an ADC circuit, a DAC circuit, a hardware coupling circuit and a filter;
the circuit amplification filter also comprises an amplification circuit and a filter circuit, and is used for amplifying the detected weak electric signal and performing primary filtering noise reduction treatment;
the ADC circuit is used for reading the amplitude value of the output signal of the front-end circuit;
the DAC circuit is used for outputting the operated signal;
The filter is used for filtering and denoising the output signal;
the hardware coupling circuit is used for connecting two paths of signals to generate an error signal;
the algorithm part adopts FxLMS algorithm.
2. The circuit for actively canceling optical noise of claim 1 wherein: the light source module further comprises a semiconductor light source, a light emitting diode, a laser diode and an infrared emitting diode;
The photodetector acquisition module further comprises a photodiode and a photoresistor.
3. The circuit for actively canceling optical noise of claim 1 wherein: the output signal of the amplifying filter and the output signal of the filter are used as two paths of input signals of a hardware coupling circuit.
4. A circuit for actively canceling optical noise according to claim 3, wherein: the hardware coupling circuit comprises a first-stage matching resistor (601), a second-stage matching resistor (602), a first-stage feedback resistor (603), a second-stage feedback resistor (604), an inverting operational amplifier (605), a third-stage matching resistor (606), an inverting superposition operational circuit (607), a first-stage balancing resistor (608) and a second-stage balancing resistor (609);
The first end of the second-stage matching resistor (602) is electrically connected with the output end of the amplifying filter, the second end of the second-stage matching resistor (602) is electrically connected with the first input end of the inverting operational amplifier (605), the first input end of the inverting operational amplifier (605) is electrically connected with the first end of the first-stage feedback resistor (603), the second input end of the inverting operational amplifier (605) is electrically connected with the first end of the first-stage balancing resistor (608), the second end of the first-stage balancing resistor (608) is grounded, and the output end of the inverting operational amplifier (605) is electrically connected with the second end of the first-stage feedback resistor (603) and the first end of the third-stage matching resistor (606);
The first end of the first-stage matching resistor (601) is electrically connected with the output end of the amplifying filter, the second end of the first-stage matching resistor (601) is electrically connected with the first input end of the inverse superposition operation circuit (607), the first input end of the inverse superposition operation circuit (607) is electrically connected with the first end of the second-stage feedback resistor (604) and the second end of the third-stage matching resistor (606), the second input end of the inverse superposition operation circuit (607) is electrically connected with the first end of the second-stage balancing resistor (609), the second end of the second-stage balancing resistor (609) is grounded, and the output end of the inverse superposition operation circuit (607) is electrically connected with the second end of the second-stage feedback resistor (604).
5. The circuit for actively canceling optical noise of claim 4 wherein: the output signal of the amplifying filter is subjected to an inverting operational amplifier (605) to obtain a first-stage output signal-U i2;
The first-stage output signal and the output signal of the filter are used as input signals of a second-stage inverse superposition operation circuit (607) together to obtain an output signal U O＝-(UO1+Ui1)＝Ui2-Ui1.
6. A method of actively canceling optical path noise based on the circuit of any of claims 1-5, wherein: the elimination of the optical path noise comprises the following steps:
s1: dividing ambient light noise and light path noise into two paths of PD receivers for receiving to obtain a first path of signals and a second path of signals;
S2: amplifying and filtering the first path of signals by a hardware circuit to obtain amplified and filtered signals; the signals are collected through an ADC collecting circuit and are transmitted to an active noise reduction kernel module to be used as input signals x (n);
s3: the second path of signals are amplified and filtered by a hardware circuit amplification filter to obtain amplified and filtered signals; after the signal is coupled with the output signal of the filter through a hardware circuit, the signal is collected through an ADC collecting circuit and is transmitted to an active noise reduction kernel module, and the signal is an error signal e (n);
S4: the active noise reduction module inputs a signal x (n) and an error signal e (n) and outputs a signal y (n) after an FxLMS algorithm;
s5: and the signal y (n) output by the active noise reduction kernel module is output to a filter through a DAC circuit, and the filtered signal is output to a hardware coupling module for coupling after the filter.
7. The method of claim 6, wherein the method comprises the steps of: in the step S4, based on the FxLMS algorithm, when the signal x (n) is input, after the signal is processed, each parameter is as follows:
d (n) is an expected value of x (n) after passing through P (z); e (n) is an error signal;
The objective function of the LMS is the square of the instantaneous error, e 2(n)＝(d(n)-y(n))2.
8. The method of claim 6, wherein the method comprises the steps of: the FxLMS adopts a noise reduction kernel algorithm and comprises an adaptive filter, when each y (n) is generated, the weight coefficient w (n) is updated through a least mean square algorithm, namely, the FxLMS is automatically and continuously adapted to a given signal, the expected response is obtained, the residual signal is minimized, and the adaptive filtering is completed;
The FxLMS algorithm comprises the following operation steps:
S11: when the signal x (n) is input, the signal passes through ambient light noise and light path noise to an optical channel P (z) system of the PD and then outputs an expected value signal d (n);
S22: the signal x (n) passes through the adaptive filter W (z) and then outputs the y (n), and the signal y (n) passes through the path S (z) for returning the residual signal and then outputs the signal y' (n);
S33: the signal x (n) is processed by an S ^ (z) system to obtain a filtered-x signal v (n), and the v (n) and an error signal e (n) are input into an LMS algorithm system together to output a signal;
s44: the output signal y' (n) and the expected value signal d (n) are input into a hardware coupling circuit together to obtain an error signal e (n).
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