Photoelectric detection circuit and photoelectric detection method

Abstract

The invention discloses a photoelectric detection circuit and a photoelectric detection method. The photoelectric detection circuit comprises a differential processing circuit, a frequency dividing circuit, a plurality of analog-to-digital conversion circuits and a main processor, the differential processing circuit performs differential amplification on the signal and sends the signal subjected to differential amplification to the frequency dividing circuit; the frequency dividing circuit carries out band-pass filtering processing on a signal through band-pass filters with different center frequencies and bandwidths to obtain a plurality of signal components with different frequencies, and the signal components are respectively sent to the corresponding analog-to-digital conversion circuits; each analog-to-digital converter performs analog-to-digital conversion on the received signal component and sends the converted data to the main processor for processing; and the main processor performs corresponding processing on the wavelet of each frequency band, and synthesizes small components of each frequency band after filtering and noise removal to obtain a total signal of an actual wide frequency range. According to the invention, influences generated by ambient temperature and a light source can be reduced, common-mode signals generated by an amplifier circuit can be eliminated, required differential-mode signals can be extracted, and deviation can be eliminated.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectric detection, and relates to a detection circuit, and in particular to a photoelectric detection circuit and a photoelectric detection method. Background Art

[0002] Photodiodes (photodetectors) convert light signals into electrical signals by absorbing photon energy and releasing charged particles in semiconductors, that is, photodiodes can generate electricity from light.

[0003] Since the internal photoelectric effect of diode semiconductors can be divided into photoconductivity effect and photovoltaic effect, two working modes, photovoltaic and photoconductivity, appear.

[0004] Photovoltaic mode: The photodiode is biased to zero, the operating current is limited, and the output forms a voltage. In this mode, the dark current (leakage current under no light conditions) is small and the linearity is poor.

[0005] Photoconductive mode: By applying a reverse bias to the photodiode, the junction capacitance of the diode is reduced and the responsivity is more linear, but more DC bias and noise will be generated, and because there is a voltage difference between the two ends of the diode, more leakage current will naturally be generated.

[0006] The current output of a photodiode has many advantages over the voltage output; for example, better response characteristics and smaller deviation.

[0007] Therefore, the current-to-voltage converter has more advantages than the voltage signal amplifier, with lower nonlinearity and DC bias, but there is an offset under high gain conditions. The feedback resistor value can be reduced through a T-type network to control this offset and reduce the offset error, but the input offset voltage will be amplified and the bandwidth will be reduced.

[0008] Li Hanchao et al. proposed an improved circuit based on feedback capacitor and composite amplifier in the Design of Low-Noise Amplifier Circuit of Photodiode. According to the simulation results, the bandwidth can be kept basically unchanged when the noise gain is reduced.

[0009] The above solutions and improvements are all aimed at ideal conditions, eliminating adverse factors such as temperature changes.

[0010] Although the unbiased, current-to-voltage conversion scheme is used to reduce the impact of the leakage current of the photodiode on the acquisition, and the leakage current relationship generated by photodiodes of different materials working at different temperatures is different, as the temperature rises, the dark current also increases exponentially, and the junction capacitance and response of the diode are also affected by temperature.

[0011] The background light will add a bias to the output of the diode, so that the final voltage measurement will add an additional bias voltage, which should also reduce the interference of background light.

[0012] In addition to excluding the influence of the detector and the corresponding detection circuit, the type of ADC (analog-to-digital converter), acquisition method, signal kickback, pre-stage low-pass or other signal processing methods will introduce new noise, distortion, ringing and other different influences.

[0013] In view of this, there is an urgent need to design a new photoelectric detection circuit and processing method to overcome at least part of the above-mentioned defects of the existing photoelectric detection circuit. Summary of the invention

[0014] The present invention provides a photoelectric detection circuit and a photoelectric detection method, which can reduce the influence of ambient temperature and light source, the acquisition fluctuation generated by the digital-to-analog converter and eliminate the common-mode signal generated by the amplifier circuit, extract the required differential-mode signal and eliminate the deviation.

[0015] To solve the above technical problem, according to one aspect of the present invention, the following technical solution is adopted:

[0016] A photoelectric detection circuit, the photoelectric detection circuit comprising: a differential processing circuit, a frequency division circuit, a plurality of analog-to-digital conversion circuits and a main processor;

[0017] The differential processing circuit is used to perform differential amplification on the signal, and send the differentially amplified signal to the frequency division circuit for frequency division processing;

[0018] The frequency division circuit is used to perform bandpass filtering on a signal through bandpass filters with different center frequencies and bandwidths to obtain a number of signal components with different frequencies, and send the signals with different frequencies, i.e., wavelet components of a number of frequency bands, to corresponding analog-to-digital conversion circuits respectively;

[0019] Each analog-to-digital converter performs analog-to-digital conversion on the received signal components and sends the converted data to the main processor for processing;

[0020] The main processor performs software filtering on the wavelet of each frequency band, and synthesizes the small components after noise removal to obtain the total signal with an actual wide frequency range.

[0021] As an implementation mode of the present invention, the main processor performs different processing on the wavelet of each frequency band, and the processing method is at least one of a sliding average filter, a moving median filter algorithm, and a Gaussian weighted average filter algorithm;

[0022] In the Gaussian weighted average filtering algorithm, a single-channel signal collects m signals, the number of signals is an odd number, the corresponding weights are calculated for the m signals, the voltage of each signal point is weighted averaged, and finally the voltage of this collection point, i.e., (m+1) / 2, is obtained and the next point is calculated, and the voltage of each collection point is continuously output as a signal result after single-band filtering.

[0023] As an implementation of the present invention, after the signal is decomposed into wavelet signals and collected, the threshold of the corresponding frequency is set narrower or eliminated for the weights of different frequencies, and the signal at this frequency that is more needed is amplified.

[0024] As an implementation mode of the present invention, the signal is decomposed into wavelet signals of n frequency bands;

[0025] Each wavelet signal calculates the weight of the x-th point f(x) = A*exp^(-(xt)^2 / 2σ^2);

[0026] Among them, A is the amplitude of the peak, t is the coordinate of the current time point, and σ is the standard deviation of the Gaussian distribution; Gaussian weighted filtering is performed according to the weight, and the processed value is obtained;

[0027] Add n small signals at each moment:

[0028] V=a%*v1+b%*v2+……d%*vn; wherein a, b,…, d are the weights of the corresponding signals.

[0029] As an embodiment of the present invention, the differential processing circuit includes a first current-voltage converter A1, a second current-voltage converter A2, a differential amplifier circuit A3, a first diode D1, a second diode D2, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4 and a plurality of resistors;

[0030] The inverting input terminal of the first current-voltage converter A1 is respectively connected to the cathode of the first diode D1, the first end of the first capacitor C1, and the first end of the first resistor R1; the anode of the first diode D1 is grounded;

[0031] The non-inverting input terminal of the first current-voltage converter A1 is respectively connected to the first end of the second capacitor C2 and the first end of the fourth resistor R4; the second end of the second capacitor C2 and the second end of the fourth resistor R4 are respectively grounded;

[0032] The output end of the first current-voltage converter A1 is respectively connected to the second end of the first capacitor C1, the second end of the first resistor R1, and the first end of the second resistor R2;

[0033] The inverting input terminal of the second current-voltage converter A2 is respectively connected to the cathode of the second diode D2, the first terminal of the third capacitor C3, and the first terminal of the sixth resistor R6; the anode of the second diode D2 is grounded;

[0034] The non-inverting input terminal of the second current-voltage converter A2 is respectively connected to the first end of the fourth capacitor C4 and the first end of the eighth resistor R8; the second end of the fourth capacitor C4 and the second end of the eighth resistor R8 are respectively grounded;

[0035] The output end of the second current-voltage converter A2 is respectively connected to the second end of the third capacitor C3, the second end of the eighth resistor R8, and the first end of the fifth resistor R5;

[0036] The inverting input terminal of the differential amplifier circuit A3 is respectively connected to the second end of the second resistor R2 and the first end of the third resistor R3; the non-inverting input terminal of the differential amplifier circuit A3 is respectively connected to the second end of the fifth resistor R5 and the first end of the seventh resistor R7; the second end of the seventh resistor R7 is grounded; the output terminal of the differential amplifier circuit A3 is connected to the second end of the third resistor R3.

[0037] According to another aspect of the present invention, the following technical solution is adopted: a photoelectric detection method, the photoelectric detection method comprising:

[0038] The differential processing circuit performs differential amplification on the signal, and sends the differentially amplified signal to the frequency division circuit for frequency division processing;

[0039] The frequency division circuit performs bandpass filtering on a signal through bandpass filters with different center frequencies and bandwidths to obtain a number of signal components with different frequencies, and sends the signal components with different frequencies, i.e., wavelets of a number of frequency bands, to corresponding analog-to-digital conversion circuits respectively;

[0040] Each analog-to-digital converter performs analog-to-digital conversion on the received signal components and sends the converted data to the main processor for processing;

[0041] The main processor performs software filtering on the wavelet in each frequency band, and synthesizes the small components after noise removal to obtain the total signal in the actual wide frequency range.

[0042] As an implementation mode of the present invention, the main processor performs different processing on the wavelet of each frequency band, and the processing method is at least one of a sliding average filter, a moving median filter algorithm, and a Gaussian weighted average filter algorithm;

[0043] In the Gaussian weighted average filtering algorithm, a single-channel signal collects m signals, the number of signals is an odd number, the corresponding weights are calculated for the m signals, the voltage of each signal point is weighted averaged, and finally the voltage of this collection point, i.e., (m+1) / 2, is obtained and the next point is calculated, and the voltage of each collection point is continuously output as a signal result after single-band filtering.

[0044] As an implementation of the present invention, after the signal is decomposed into wavelet signals and collected, the threshold of the corresponding frequency is set narrower or eliminated for the weights of different frequencies, and the signal at this frequency that is more needed is amplified.

[0045] As an implementation mode of the present invention, the signal is decomposed into wavelet signals of n frequency bands;

[0046] Each wavelet signal calculates the weight of the x-th point f(x) = A*exp^(-(xt)^2 / 2σ^2);

[0047] Among them, A is the amplitude of the peak, t is the coordinate of the current time point, and σ is the standard deviation of the Gaussian distribution; Gaussian weighted filtering is performed according to the weight, and the processed value is obtained;

[0048] Add n small signals at each moment:

[0049] V=a%*v1+b%*v2+……d%*vn; wherein a, b,…, d are the weights of the corresponding signals.

[0050] As an embodiment of the present invention, the differential processing circuit includes a first current-voltage converter A1, a second current-voltage converter A2, a differential amplifier circuit A3, a first diode D1, a second diode D2, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4 and a plurality of resistors;

[0051] The inverting input terminal of the first current-voltage converter A1 is respectively connected to the cathode of the first diode D1, the first end of the first capacitor C1, and the first end of the first resistor R1; the anode of the first diode D1 is grounded;

[0052] The non-inverting input terminal of the first current-voltage converter A1 is respectively connected to the first end of the second capacitor C2 and the first end of the fourth resistor R4; the second end of the second capacitor C2 and the second end of the fourth resistor R4 are respectively grounded;

[0053] The output end of the first current-voltage converter A1 is respectively connected to the second end of the first capacitor C1, the second end of the first resistor R1, and the first end of the second resistor R2;

[0054] The inverting input terminal of the second current-voltage converter A2 is respectively connected to the cathode of the second diode D2, the first terminal of the third capacitor C3, and the first terminal of the sixth resistor R6; the anode of the second diode D2 is grounded;

[0055] The non-inverting input terminal of the second current-voltage converter A2 is respectively connected to the first end of the fourth capacitor C4 and the first end of the eighth resistor R8; the second end of the fourth capacitor C4 and the second end of the eighth resistor R8 are respectively grounded;

[0056] The output end of the second current-voltage converter A2 is respectively connected to the second end of the third capacitor C3, the second end of the eighth resistor R8, and the first end of the fifth resistor R5;

[0057] The inverting input terminal of the differential amplifier circuit A3 is respectively connected to the second end of the second resistor R2 and the first end of the third resistor R3; the non-inverting input terminal of the differential amplifier circuit A3 is respectively connected to the second end of the fifth resistor R5 and the first end of the seventh resistor R7; the second end of the seventh resistor R7 is grounded; the output terminal of the differential amplifier circuit A3 is connected to the second end of the third resistor R3.

[0058] The beneficial effects of the present invention are as follows: the photoelectric detection circuit and the photoelectric detection method proposed in the present invention can reduce the influence of ambient temperature and light source and eliminate the common mode signal generated by the amplifier circuit, extract the required differential mode signal and eliminate the deviation. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 Schematic diagram of the equivalent model of a photodiode.

[0060] Figure 2 FIG. 4 is a schematic diagram of the composition of a photoelectric detection circuit in one embodiment of the present invention.

[0061] Figure 3 FIG. 4 is a circuit diagram of a differential processing circuit in an embodiment of the present invention. DETAILED DESCRIPTION

[0062] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0063] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0064] The description in this section is only for several typical embodiments, and the present invention is not limited to the scope of the embodiments. The same or similar prior art means and some technical features in the embodiments are mutually replaced within the scope of the present invention.

[0065] The description of the steps in each embodiment in the specification is only for the convenience of explanation, and the implementation method of the present application is not limited by the order of implementation of the steps.

[0066] The term "connection" as used in the specification includes both direct connection and indirect connection, such as connection through some active devices, passive devices or electrically conductive media; it may also include connection through other active devices or passive devices known to those skilled in the art on the basis of achieving the same or similar functional purposes, such as connection through circuits or components such as switches and follower circuits.

[0067] Figure 1 is a schematic diagram of the equivalent model of a photodiode; where C D is the zero bias junction capacitance (parasitic capacitance), which changes with the bias voltage and is affected by temperature; R D is the dark resistance across the diode (junction resistance at 0 bias, which is very large and can be ignored); R S is the internal resistance in series, which is very small and can be ignored; I P It is the photocurrent generated by the photodiode receiving the light signal.

[0068] The present invention discloses a photoelectric detection circuit. Figure 2 FIG. 1 is a schematic diagram of a photoelectric detection circuit according to an embodiment of the present invention; please refer to FIG. Figure 2 The photoelectric detection circuit includes: a differential processing circuit 1, a frequency division circuit 2, a plurality of analog-to-digital conversion circuits 3 and a main processor 4 (MCU).

[0069] The differential processing circuit 1 is used to perform differential amplification on the signal, and send the differentially amplified signal to the frequency division circuit for frequency division processing; the signal processed by the differential processing circuit 1 can be a fixed value or a variable value (such as a sawtooth wave, a sine wave, etc.). The frequency division circuit 2 is used to perform bandpass filtering on a signal through a bandpass filter with different center frequencies and bandwidths to obtain a number of signal components with different frequencies, and send the signal components with different frequencies, i.e., wavelets of a number of frequency bands, to the corresponding analog-to-digital conversion circuits respectively;. Each analog-to-digital converter 3 performs analog-to-digital conversion on the received signal components, and sends the converted data to the main processor for processing; the main processor 4 performs software filtering on the wavelets of each frequency band, and synthesizes the small components after noise removal to obtain the total signal with an actual wide frequency range.

[0070] In one embodiment of the present invention, the main processor 4 performs different processing on the wavelet of each frequency band, and the processing method can be at least one of sliding average filtering, moving median filtering algorithm, and Gaussian weighted average filtering algorithm. The wavelet of each frequency band is processed differently: different degrees of filtering are performed for different frequency bands; for example, the signal is decomposed into wavelets of different frequencies from 1 to n, and Gaussian weighted filtering is performed on each wavelet signal; if the noise impact at the middle a (0<=a<=n) frequency is particularly large, the weight can be reduced by filtering, so that the final noise impact is reduced; the various filtering algorithms described later are some software digital filtering methods commonly used worldwide, and the signals are different, the requirements are different, and the processing methods are different; the processing methods are not limited to sliding, median filtering and Gaussian filtering.

[0071] In the Gaussian weighted average filtering algorithm, signal characteristics are retained and the processing effect is better. A single-channel signal collects m signals, and the number of signals is an odd number. The corresponding weights are calculated for the m signals, and the voltage of each signal point is weighted averaged. Finally, the voltage of this collection point, that is, (m+1) / 2, is obtained and the next point calculation is performed. The voltage of each collection point is continuously output as a signal result after single-band filtering.

[0072] After the signal is decomposed into wavelet signals and collected, the threshold of the corresponding frequency is set narrower or eliminated according to the weights of different frequencies, and the signal at this frequency that is more needed is amplified.

[0073] In one embodiment of the present invention, the signal is decomposed into wavelet signals of n frequency bands; each wavelet signal calculates the weight of the x-th point f(x) = A*exp^(-(xt)^2 / 2σ^2); wherein A is the amplitude of the peak, t is the coordinate of the current time point, and σ is the standard deviation of the Gaussian distribution; Gaussian weighted filtering is performed according to the weight to obtain the processed value; the n small signals at each moment are added together: V = a%*v1+b%*v2+…d%*vn; wherein a, b,…,d are the weights of the corresponding signals.

[0074] The present invention discloses a photoelectric detection circuit. Figure 3 is a circuit diagram of a differential processing circuit in one embodiment of the present invention; please refer to Figure 3 The differential processing circuit includes: a first current-voltage converter A1, a second current-voltage converter A2, a differential amplifier circuit A3, a first diode D1, a second diode D2, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4 and a plurality of resistors.

[0075] The inverting input terminal of the first current-voltage converter A1 is respectively connected to the cathode of the first diode D1, the first end of the first capacitor C1, and the first end of the first resistor R1; the anode of the first diode D1 is grounded.

[0076] The non-inverting input terminal of the first current-voltage converter A1 is connected to the first end of the second capacitor C2 and the first end of the fourth resistor R4 respectively; the second end of the second capacitor C2 and the second end of the fourth resistor R4 are grounded respectively.

[0077] The output end of the first current-voltage converter A1 is respectively connected to the second end of the first capacitor C1, the second end of the first resistor R1, and the first end of the second resistor R2.

[0078] The inverting input terminal of the second current-voltage converter A2 is respectively connected to the cathode of the second diode D2, the first terminal of the third capacitor C3, and the first terminal of the sixth resistor R6; the anode of the second diode D2 is grounded.

[0079] The non-inverting input terminal of the second current-voltage converter A2 is connected to the first end of the fourth capacitor C4 and the first end of the eighth resistor R8 respectively; the second end of the fourth capacitor C4 and the second end of the eighth resistor R8 are grounded respectively.

[0080] The output end of the second current-voltage converter A2 is respectively connected to the second end of the third capacitor C3, the second end of the eighth resistor R8, and the first end of the fifth resistor R5.

[0081] The inverting input terminal of the differential amplifier circuit A3 is respectively connected to the second end of the second resistor R2 and the first end of the third resistor R3; the non-inverting input terminal of the differential amplifier circuit A3 is respectively connected to the second end of the fifth resistor R5 and the first end of the seventh resistor R7; the second end of the seventh resistor R7 is grounded; the output terminal of the differential amplifier circuit A3 is connected to the second end of the third resistor R3.

[0082] In one embodiment of the present invention, two identical 0-bias photodiodes are respectively connected to a current-voltage amplifier, and voltage signals are output through RF (R1 and R6) conversion resistors of the same resistance value. A differential circuit is used to perform a subtraction operation to eliminate the common-mode signal generated by the circuit and the environment, and the differential-mode signal required for the test is extracted and amplified.

[0083] Among them, D1 is the reference photodiode, D2 is the photodiode to be measured, A1 and A2 are current-voltage converters corresponding to D1 and D2 respectively, which can convert the photocurrent into the corresponding output voltages V1 and V2. Set the compensation resistors R4 and R8 to be equal to the corresponding RF, so that the bias voltage generated by the bias current on RF is deducted from the compensation resistor on R4, so that the deviation is reduced to I B-*R1-I B+*R4. However, the introduction of a new resistor in the circuit will generate additional noise under the influence of the input current. Connecting a suitable capacitor in parallel at both ends of the compensation resistor can eliminate most of the noise generated by the bias current on the resistor. There will be a very small parallel stray capacitance CS on the feedback resistor. As the frequency increases, the stray capacitance and the feedback resistor RF will generate additional noise, and the noise gain will reach 1+CI / CS (CI includes the diode parasitic capacitance CD and the operational amplifier input capacitance). Therefore, a CF feedback capacitor is connected in parallel to the RF feedback resistor, which can reduce the noise gain to 1+CI / (CS+CF) and perform phase compensation.

[0084] A3 is a differential amplifier circuit, which is used to subtract and amplify signals V1 and V2. Among them, setting resistors R2=R5, R3=R7, that is, satisfying the balance condition, can reduce the impact of offset current on circuit operation error and can also reduce the calculation and design workload. The specific formula is: VOUT=R3 / R2*(V2-V1). Under low frequency conditions, assuming that the temperature rise makes the leakage current of the photodiode IL, the photocurrents generated by the photodiode through ambient light and the measured light are IP1 and IP2 respectively, and the current generated by the optical signal to be measured is IP2-IP1, so the V1 generated by the A1 operational amplifier is (IP1+IL)*RF+I B-*RF-I B+*RC, and the V2 generated by the A2 operational amplifier is (IP1++IL)*RF+I B-*RF-I B+*RC, that is, when RC=RF is the balance resistor, V2-V1=(IP2-IP1)*RF. Therefore, the output signal of the differential amplifier circuit is a differential mode signal, which has a strong ability to suppress common mode signals and eliminates the influence of deviations such as leakage current and background light.

[0085] The current-to-voltage conversion circuit of part A1 is used to collect the signal of the ambient reference light, while the current-to-voltage conversion circuit of part A2 is used to collect the signal of the light source to be tested.

[0086] Under ideal conditions such as constant temperature, airtight shading, etc., the photodiode works with a current-voltage converter and a T-type resistor network to obtain a very suitable correspondence between the responsivity, output current, and output voltage. However, factors such as leakage current, junction capacitance, and bias voltage that are out of these conditions will be superimposed on the output voltage, causing the final output to have deviations and drifts. Since the two photodiodes are the same, the effects of temperature on leakage current and responsivity, changes in junction capacitance, etc. are the same, and the circuit adopts a symmetrical structure, so that in the final differential amplifier circuit, the measured mixed signal can be deducted from the same common-mode signal formed by the superposition of various unfavorable conditions, eliminating the deviation.

[0087] The differential amplified signal is Figure 3 The processed signal has a smaller error than the ordinary photoelectric detection current-voltage conversion circuit, and greatly reduces the influence of factors such as temperature. However, the signal will still generate additional noise and mutation values ​​in different frequency bands during the acquisition process, which is unfavorable and undesirable for the signal. The subsequent frequency division acquisition and algorithm processing can optimize the impact in this aspect.

[0088] like Figure 3 , the differentially amplified signal is divided by a frequency division circuit. This frequency division circuit is different from the frequency division / multiplication circuit. It passes a signal through a bandpass filter with different center frequencies and bandwidths to obtain n different frequency components of the signal. After the signal is decomposed by wavelet, the threshold of the corresponding frequency can be set narrower or eliminated for the weights of different frequencies, and the signal at this frequency that is more needed can be amplified.

[0089] Here, the bandpass filter can be built by a switched capacitor filter, multiple multi-order bandpass filters or other methods. The advantage of the switched capacitor filter is that the center frequency is easy to adjust, but if the input signal frequency range is large, the filtering effect of this filter is not ideal and it will introduce noise in additional frequency bands. The use of multiple multi-order bandpass filters reduces this concern, but the calculation and resistance-capacitance matching for different bandpass filters are more troublesome when selecting frequencies, and the influence of phase shift needs to be considered.

[0090] Since the frequency division circuit divides a signal into n components, multiple analog-to-digital converters are used to collect the signals and hand them over to the MCU for processing.

[0091] After the data of each frequency band is collected, the MCU can process the wavelet of each frequency band differently. For example, sliding average filtering, moving median filtering algorithm, etc. The following is Gaussian weighted average filtering. This method can retain signal characteristics and has a good processing effect. A single signal collects m signals, and the number of signals is an odd number. The corresponding weights are calculated for the m signals, and the voltage of each signal point is weighted averaged. Finally, the voltage of this acquisition point, that is, (m+1) / 2, is obtained and the next point is calculated. The voltage of each acquisition point is continuously output as the signal result after single-band filtering. Finally, the small components after filtering and removing noise in each frequency band are synthesized to obtain the total signal of the actual wide frequency range. This filtering method can well retain the trend of the signal and reduce the influence of noise and mutation values. In some fast-changing circuits, the influence of hysteresis effect is also very small.

[0092] Combining the front-stage dual-channel sensor differential subtraction and frequency division filtering acquisition method can greatly reduce the interference caused by various environments and itself.

[0093] The present invention further discloses a photoelectric detection method, the photoelectric detection method comprising:

[0094] The differential processing circuit performs differential amplification on the signal, and sends the differentially amplified signal to the frequency division circuit for frequency division processing;

[0095] The frequency division circuit performs bandpass filtering on a signal through bandpass filters with different center frequencies and bandwidths to obtain a number of signal components with different frequencies (i.e., wavelets with several frequency bands), and sends the signal components with different frequencies to the corresponding analog-to-digital conversion circuits respectively;

[0096] Each analog-to-digital converter performs analog-to-digital conversion on the received signal components and sends the converted data to the main processor for processing;

[0097] The main processor performs software filtering on the wavelet in each frequency band, and synthesizes the small components after noise removal to obtain the total signal in the actual wide frequency range.

[0098] In one embodiment of the present invention, the main processor performs different processing on the wavelet of each frequency band, and the processing method is at least one of a sliding average filter, a moving median filter algorithm, and a Gaussian weighted average filter algorithm; in the Gaussian weighted average filter algorithm, a single-channel signal collects m signals, the number of signals is an odd number, and the corresponding weights are calculated for the m signals, and the voltage of each signal point is weighted averaged, and finally the voltage of this collection point, i.e., (m+1) / 2, is obtained and the next point calculation is performed, and the voltage of each collection point is continuously output as a signal result after single-band filtering.

[0099] After the signal is decomposed into wavelet signals and collected, the threshold of the corresponding frequency is set narrower or eliminated according to the weights of different frequencies, and the signal at this frequency that is more needed is amplified.

[0100] In one embodiment of the present invention, the signal is decomposed into wavelet signals of n frequency bands; each wavelet signal calculates the weight of the x-th point f(x) = A*exp^(-(xt)^2 / 2σ^2); wherein A is the amplitude of the peak, t is the coordinate of the current time point, and σ is the standard deviation of the Gaussian distribution; Gaussian weighted filtering is performed according to the weight to obtain the processed value; the n small signals at each moment are added together: V = a%*v1+b%*v2+…d%*vn; wherein a, b,…,d are the weights of the corresponding signals.

[0101] In summary, the photoelectric detection circuit and the photoelectric detection method proposed in the present invention can reduce the influence of ambient temperature and light source and eliminate the common-mode signal generated by the amplifier circuit, extract the required differential-mode signal, and eliminate the deviation.

[0102] It should be noted that the present application can be implemented in software and / or a combination of software and hardware; for example, it can be implemented using an application-specific integrated circuit (ASIC), a general-purpose computer, or any other similar hardware device. In some embodiments, the software program of the present application can be executed by a processor to implement the above steps or functions. Similarly, the software program of the present application (including related data structures) can be stored in a computer-readable recording medium; for example, a RAM memory, a magnetic or optical drive or a floppy disk and the like. In addition, some steps or functions of the present application can be implemented in hardware; for example, as a circuit that cooperates with a processor to perform various steps or functions.

[0103] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0104] The description and application of the present invention here are illustrative, and it is not intended to limit the scope of the present invention to the above-mentioned embodiments. The effects or advantages involved in the embodiments may not be embodied in the embodiments due to interference from various factors, and the description of the effects or advantages is not used to limit the embodiments. The deformation and change of the embodiments disclosed here are possible, and the replacement of the embodiments and the various equivalent parts are well known to those of ordinary skill in the art. It should be clear to those skilled in the art that the present invention can be implemented in other forms, structures, arrangements, proportions, and with other components, materials and parts without departing from the spirit or essential features of the present invention. Other deformations and changes can be made to the embodiments disclosed here without departing from the scope and spirit of the present invention.

Claims

1. A photoelectric detection circuit, characterized in that: The photoelectric detection circuit includes: a differential processing circuit, a frequency division circuit, a plurality of analog-to-digital conversion circuits and a main processor; The differential processing circuit is used to perform differential amplification on the signal, and send the differentially amplified signal to the frequency division circuit for frequency division processing; The frequency division circuit is to perform bandpass filtering on a signal through bandpass filters with different center frequencies and bandwidths to obtain a number of signal components with different frequencies, i.e., wavelets of a number of frequency bands; Sending a number of signal components of different frequencies to corresponding analog-to-digital conversion circuits respectively; Each analog-to-digital converter performs analog-to-digital conversion on the received signal components and sends the converted data to the main processor for processing; The main processor performs software filtering on the wavelet of each frequency band, and synthesizes the small components after noise removal to obtain the total signal with an actual wide frequency range.

2. The photoelectric detection circuit according to claim 1, characterized in that: The main processor performs different processing on the wavelet of each frequency band, and the processing method is not limited to sliding average filtering, moving median filtering algorithm, and Gaussian weighted average filtering algorithm; In the Gaussian weighted average filtering algorithm, a single-channel signal collects m signal points, where the number of signal points is an odd number. The corresponding weights are calculated for the m signal points, and the voltage of each signal point is weighted averaged. Finally, the voltage of this collection point, i.e., (m+1) / 2, is obtained and the next point is calculated. The voltage of each collection point is continuously output as a signal result after single-band filtering.

3. The photoelectric detection circuit according to claim 1, characterized in that: After the signal is decomposed into wavelet signals and collected, the threshold of the corresponding frequency is set narrower or eliminated according to the weights of different frequencies, and the signal at this frequency with a larger signal proportion is amplified.

4. The photoelectric detection circuit according to claim 3, characterized in that: After the signal is decomposed, it becomes a wavelet signal of n frequency bands; Each wavelet signal calculates the weight of the x-th point f(x) = A*exp^(-(xt)^2 / 2σ^2); Among them, A is the amplitude of the peak, t is the coordinate of the current time point, and σ is the standard deviation of the Gaussian distribution; the wavelet signal is Gaussian weighted filtered according to the weight, which is the processed value; Add n small signals at each moment: V=a%*v1+b%*v2+……d%*vn; wherein a, b,…, d are the weights of the corresponding signals.

5. The photoelectric detection circuit according to claim 1, characterized in that: The differential processing circuit includes a first current-voltage converter A1, a second current-voltage converter A2, a differential amplifier circuit A3, a first diode D1, a second diode D2, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4 and a plurality of resistors; The inverting input terminal of the first current-voltage converter A1 is respectively connected to the cathode of the first diode D1, the first end of the first capacitor C1, and the first end of the first resistor R1; the anode of the first diode D1 is grounded; The non-inverting input terminal of the first current-voltage converter A1 is respectively connected to the first end of the second capacitor C2 and the first end of the fourth resistor R4; the second end of the second capacitor C2 and the second end of the fourth resistor R4 are respectively grounded; The output end of the first current-voltage converter A1 is respectively connected to the second end of the first capacitor C1, the second end of the first resistor R1, and the first end of the second resistor R2; The inverting input terminal of the second current-voltage converter A2 is respectively connected to the cathode of the second diode D2, the first terminal of the third capacitor C3, and the first terminal of the sixth resistor R6; the anode of the second diode D2 is grounded; The non-inverting input terminal of the second current-voltage converter A2 is respectively connected to the first end of the fourth capacitor C4 and the first end of the eighth resistor R8; the second end of the fourth capacitor C4 and the second end of the eighth resistor R8 are respectively grounded; The output end of the second current-voltage converter A2 is respectively connected to the second end of the third capacitor C3, the second end of the eighth resistor R8, and the first end of the fifth resistor R5; The inverting input terminal of the differential amplifier circuit A3 is respectively connected to the second end of the second resistor R2 and the first end of the third resistor R3; the non-inverting input terminal of the differential amplifier circuit A3 is respectively connected to the second end of the fifth resistor R5 and the first end of the seventh resistor R7; the second end of the seventh resistor R7 is grounded; the output terminal of the differential amplifier circuit A3 is connected to the second end of the third resistor R3.

6. A photoelectric detection method, characterized in that: The photoelectric detection method comprises: The differential processing circuit performs differential amplification on the signal, and sends the differentially amplified signal to the frequency division circuit for frequency division processing; The frequency division circuit performs bandpass filtering on a signal through bandpass filters with different center frequencies and bandwidths to obtain a number of signal components with different frequencies, and sends the signal components with different frequencies to the corresponding analog-to-digital conversion circuits respectively; the signal components with different frequencies form wavelets with several frequency bands respectively; Each analog-to-digital converter performs analog-to-digital conversion on the received signal components and sends the converted data to the main processor for processing; The main processor processes the wavelet in each frequency band accordingly, filters the wavelet in each frequency band, removes the small components after the noise, and synthesizes the total signal in the actual wide frequency range.

7. The photoelectric detection method according to claim 6, characterized in that: The main processor performs different processing on the wavelet of each frequency band, and the processing method is at least one of a sliding average filter, a moving median filter algorithm, and a Gaussian weighted average filter algorithm; In the Gaussian weighted average filtering algorithm, a single-channel signal collects m signals, the number of signals is an odd number, the corresponding weights are calculated for the m signals, the voltage of each signal point is weighted averaged, and finally the voltage of this collection point, i.e., (m+1) / 2, is obtained and the next point is calculated, and the voltage of each collection point is continuously output as a signal result after single-band filtering.

8. The photoelectric detection method according to claim 6, characterized in that: After the signal is decomposed into wavelet signals and collected, the threshold of the corresponding frequency is set narrower or eliminated according to the weights of different frequencies, and the signal at this frequency that is more needed is amplified.

9. The photoelectric detection method according to claim 8, characterized in that: After the signal is decomposed, it becomes a wavelet signal of n frequency bands; Each wavelet signal calculates the weight of the x-th point f(x) = A*exp^(-(xt)^2 / 2σ^2); Among them, A is the amplitude of the peak, t is the coordinate of the current time point, and σ is the standard deviation of the Gaussian distribution; Gaussian weighted filtering is performed according to the weight, and the processed value is obtained; Add n small signals at each moment: V=a%*v1+b%*v2+……d%*vn; wherein a, b,…, d are the weights of the corresponding signals.

10. The photoelectric detection method according to claim 6, characterized in that: The differential processing circuit includes a first current-voltage converter A1, a second current-voltage converter A2, a differential amplifier circuit A3, a first diode D1, a second diode D2, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4 and a plurality of resistors; The inverting input terminal of the first current-voltage converter A1 is respectively connected to the cathode of the first diode D1, the first end of the first capacitor C1, and the first end of the first resistor R1; the anode of the first diode D1 is grounded; The non-inverting input terminal of the first current-voltage converter A1 is respectively connected to the first end of the second capacitor C2 and the first end of the fourth resistor R4; the second end of the second capacitor C2 and the second end of the fourth resistor R4 are respectively grounded; The output end of the first current-voltage converter A1 is respectively connected to the second end of the first capacitor C1, the second end of the first resistor R1, and the first end of the second resistor R2; The inverting input terminal of the second current-voltage converter A2 is respectively connected to the cathode of the second diode D2, the first terminal of the third capacitor C3, and the first terminal of the sixth resistor R6; the anode of the second diode D2 is grounded; The non-inverting input terminal of the second current-voltage converter A2 is respectively connected to the first end of the fourth capacitor C4 and the first end of the eighth resistor R8; the second end of the fourth capacitor C4 and the second end of the eighth resistor R8 are respectively grounded; The output end of the second current-voltage converter A2 is respectively connected to the second end of the third capacitor C3, the second end of the eighth resistor R8, and the first end of the fifth resistor R5; The inverting input terminal of the differential amplifier circuit A3 is respectively connected to the second end of the second resistor R2 and the first end of the third resistor R3; the non-inverting input terminal of the differential amplifier circuit A3 is respectively connected to the second end of the fifth resistor R5 and the first end of the seventh resistor R7; the second end of the seventh resistor R7 is grounded; the output terminal of the differential amplifier circuit A3 is connected to the second end of the third resistor R3.

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