CN111352097A - Laser Doppler echo signal processing method for laser radar and circuit system thereof - Google Patents
Laser Doppler echo signal processing method for laser radar and circuit system thereof Download PDFInfo
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- CN111352097A CN111352097A CN201811569585.3A CN201811569585A CN111352097A CN 111352097 A CN111352097 A CN 111352097A CN 201811569585 A CN201811569585 A CN 201811569585A CN 111352097 A CN111352097 A CN 111352097A
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- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
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- G01S7/486—Receivers
- G01S7/487—Extracting wanted echo signals, e.g. pulse detection
- G01S7/4873—Extracting wanted echo signals, e.g. pulse detection by deriving and controlling a threshold value
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Abstract
A laser Doppler echo signal processing method and a circuit system for a laser radar. The circuitry comprises an avalanche photodiode, wherein the avalanche photodiode converts acquired laser doppler echo signals into current signals; a variable gain transimpedance amplifier which converts the laser Doppler echo signal converted into the current signal into a voltage signal; and the signal control and processing module analyzes the voltage signal sample, and forms a gain adjusting instruction based on the corresponding relation between the light intensity information of the pre-calibrated laser Doppler echo signal and the amplification gain of the variable gain transimpedance amplifier, wherein the variable gain transimpedance amplifier adjusts the gain value according to the gain adjusting instruction so as to reduce the possibility of the occurrence of the saturation phenomenon.
Description
Technical Field
The present invention relates to laser measurement, and more particularly, to a laser doppler echo signal processing method for a laser radar and a circuit system thereof.
Background
The lidar is a radar system that detects characteristic quantities such as a position, a speed, and the like of a target by emitting a laser beam, and generally includes a transmission system, a reception system, a signal processing system, a control system, a display system, and the like. The working principle of the system is that a laser emits laser with certain frequency, the laser is scanned by an optical emission system through the modulation of a laser modulator and a laser controller and emitted to a space, and the laser is transmitted in the atmosphere or the ocean and radiated to the surface of a target. Then the laser scatters part of the optical signal, the echo optical signal is converged to a detection circuit through a receiving optical system, and then the target information is displayed on a display screen through signal processing such as photoelectric conversion, amplification, acquisition and the like.
In the existing laser radar, most of the detection circuits adopt high-sensitivity APD (Avalanche Photo Diode) detectors to achieve longer detection distance. However, for longer detection distances, the laser pulse peak power increases accordingly, and the reflected echo pulse average power also increases, which causes the APD detector to saturate the output signal when the detected echo signal is strong. The pulse signal saturation of the front-end detection circuit causes the pulse width of the detection pulse signal to be widened and lengthened, and the continuous saturation delay can reach even 1 us. Therefore, the distance measurement signal reflected by the near target is submerged in the saturated signal and the short-distance signal cannot be measured, so that the range of pulse distance measurement is limited, and a blind area which cannot be detected exists in the short distance.
In addition, the reflectivity of the target surface is high, or when the target is detected at a short distance, for example, less than 0.5m, the echo signal is also strong, and the output signal is saturated, and the echo signal cannot be detected. Therefore, the laser doppler echo signal processing of the existing laser radar has problems and needs to be solved.
Disclosure of Invention
An object of the present invention is to provide a laser doppler echo signal processing method for a laser radar and a circuit system thereof, so as to solve the problem of a range error caused by a pulse width broadening and stretching delay due to saturation of a detection circuit, especially an APD (Avalanche Photo Diode) detection circuit, when a short distance is detected or an echo signal is strong.
Another objective of the present invention is to provide a method and a circuit system for processing a laser doppler echo signal for a laser radar, so that a close-range target and a long-range target can accurately measure a recovery pulse signal, thereby avoiding a blind area.
Another objective of the present invention is to provide a laser doppler echo signal processing method for a laser radar and a circuit system thereof, so as to improve a ranging range of the laser radar.
Another objective of the present invention is to provide a method for processing a laser doppler echo signal for a laser radar and a circuit system thereof, so as to solve the problem that a conventional transimpedance amplifier cannot adapt to the situation that the peak power of a laser is continuously increased, thereby eliminating the saturation of an avalanche photodiode detection pulse signal.
Another objective of the present invention is to provide a method for processing a laser doppler echo signal for a laser radar and a circuit system thereof, wherein the circuit system utilizes a multi-channel switch logic control module to adjust a gain value of a variable gain transimpedance amplifier, so as to adjust the gain value of the variable gain transimpedance amplifier.
Another objective of the present invention is to provide a method for processing a laser doppler echo signal of an echo signal laser radar for a laser radar avalanche photodiode detection circuit and a circuit system thereof, wherein the magnitude of the gain of the variable gain transimpedance amplifier is adjusted based on a corresponding relationship between light intensity information of a pre-calibrated laser doppler echo signal and an amplification gain of the variable gain transimpedance amplifier, so as to avoid a saturation condition.
Another object of the present invention is to provide a laser doppler echo signal processing method for a laser radar and a circuit system thereof, wherein the magnitude of the current of the avalanche photodiode is inversely proportional to the magnitude of the gain of the variable gain transimpedance amplifier, thereby reducing the possibility of occurrence of a saturation condition.
In order to achieve at least one of the above objects, according to one aspect of the present invention, there is further provided a laser doppler echo signal processing method for a lidar, including:
processing the obtained laser Doppler echo signal through an avalanche photodiode to convert the laser Doppler echo signal into a current signal;
converting the laser Doppler echo signal converted into the current signal into a voltage signal through a variable gain trans-impedance amplifier, wherein the variable gain trans-impedance amplifier comprises the trans-impedance amplifier and a gain adjuster used for adjusting the gain value of the trans-impedance amplifier;
sampling the laser Doppler echo signal converted into a current signal;
processing the sampled laser Doppler echo signal to generate a gain adjusting instruction based on the corresponding relation between the light intensity information of the pre-calibrated laser Doppler echo signal and the amplification gain of the variable gain trans-impedance amplifier;
adjusting, by the gain adjuster, a gain value of the variable gain transimpedance amplifier in response to the gain adjustment instruction; and
and comparing the pulse signal output by the gain-adjusted variable gain trans-impedance amplifier with a preset level to generate a laser Doppler echo signal processing result.
According to an embodiment of the present invention, in the correspondence between the light intensity information of the laser doppler echo signal that is pre-calibrated and the amplification gain of the variable gain transimpedance amplifier, the light intensity information of the laser doppler echo signal and the amplification gain of the variable gain transimpedance amplifier have an inverse relationship.
According to one embodiment of the invention, sampling a laser doppler echo signal converted into a current signal comprises:
and sampling the laser Doppler echo signal converted into the current signal by a high-speed analog-to-digital converter, wherein the high-speed analog-to-digital converter can ensure that at least one sampling point is on the maximum value of the echo pulse peak value of the laser Doppler echo signal.
According to an embodiment of the present invention, the adjusting gain of the variable gain transimpedance amplifier in response to the gain adjustment command includes:
in response to the gain adjustment instruction, the multi-channel switch logic control module switches the resistor conducted with the transimpedance amplifier to adjust a gain value of the transimpedance amplifier.
According to one embodiment of the invention, the multi-channel switch logic control module is implemented as a multi-channel single pole single throw switch ADG 1611.
According to one embodiment of the invention, the transimpedance amplifier is implemented as LTC6268 or LTC 6269.
According to one embodiment of the invention, the high speed analog to digital converter is implemented as an AD 9430.
In another aspect of the present invention, the present invention further provides a circuit system for processing a laser doppler echo signal of a laser radar, comprising;
an avalanche photodiode, wherein the avalanche photodiode converts the acquired laser doppler echo signal into a current signal;
a variable gain transimpedance amplifier which converts the laser Doppler echo signal converted into the current signal into a voltage signal; and
and the signal control and processing module analyzes a voltage signal sample, and forms a gain adjusting instruction based on the corresponding relation between the light intensity information of the pre-calibrated laser Doppler echo signal and the amplification gain of the variable gain transimpedance amplifier, wherein the variable gain transimpedance amplifier adjusts the gain value according to the gain adjusting instruction.
According to an embodiment of the present invention, in the correspondence between the light intensity information of the laser doppler echo signal that is pre-calibrated and the amplification gain of the variable gain transimpedance amplifier, the light intensity information of the laser doppler echo signal and the amplification gain of the variable gain transimpedance amplifier have an inverse relationship.
According to an embodiment of the present invention, the variable gain transimpedance amplifier includes a transimpedance amplifier and a gain adjuster for adjusting a gain value of the transimpedance amplifier, wherein the gain adjuster further includes a multi-channel switch logic control module and a plurality of resistors, wherein the multi-channel switch logic control module is electrically connected to the plurality of resistors, and wherein the multi-channel switch logic control module controls on and off of switches thereof to control a resistance value in response to the gain adjustment command, thereby adjusting the gain value of the transimpedance amplifier.
According to an embodiment of the present invention, the circuit system further includes a high speed analog-to-digital converter, wherein the high speed analog-to-digital converter samples the voltage signal and transmits the voltage signal to the signal control and processing module, wherein the high speed analog-to-digital converter is capable of ensuring that at least one sampling point is at the maximum value of the peak value of the echo pulse of the laser doppler echo signal.
According to one embodiment of the invention, the signal control and processing module is implemented as an FPGA, a DSP, or a combination of both.
According to an embodiment of the present invention, the circuit system further includes a high speed comparator, wherein the high speed comparator uses a leading edge timing transmission mode to compare the voltage signal converted by the variable gain transimpedance amplifier with a preset fixed level, and output a corresponding digital pulse signal, and transmit the digital pulse signal to the signal control and processing module for analyzing a characteristic quantity of a target object.
Drawings
FIG. 1 is a system design block diagram of circuitry for processing an echo signal of a lidar avalanche photodiode detection circuit in accordance with a preferred embodiment of the present invention.
Fig. 2 is a schematic diagram of a transimpedance amplifier according to a preferred embodiment of the present invention.
Fig. 3 is a schematic diagram of a transimpedance amplifier according to a preferred embodiment of the present invention.
Fig. 4 is a circuit diagram of a variable gain transimpedance amplifier for a programmable gain function according to a preferred embodiment of the present invention.
FIG. 5 is a block diagram of a high speed data acquisition circuit design according to a preferred embodiment of the present invention.
FIG. 6 is a circuit diagram of a high speed comparator according to a preferred embodiment of the present invention.
FIG. 7 is a circuit diagram of a high speed comparator according to a preferred embodiment of the present invention.
Fig. 8 is a flowchart of a laser doppler echo signal processing method according to an embodiment of the present invention.
Detailed Description
The following description is presented to disclose the invention so as to enable any person skilled in the art to practice the invention. The preferred embodiments in the following description are given by way of example only, and other obvious variations will occur to those skilled in the art. The basic principles of the invention, as defined in the following description, may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.
It will be understood by those skilled in the art that in the present disclosure, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for ease of description and simplicity of description, and do not indicate or imply that the referenced devices or components must be in a particular orientation, constructed and operated in a particular orientation, and thus the above terms are not to be construed as limiting the present invention.
It is understood that the terms "a" and "an" should be interpreted as meaning that a number of one element or element is one in one embodiment, while a number of other elements is one in another embodiment, and the terms "a" and "an" should not be interpreted as limiting the number.
Nowadays, laser radar develops towards the direction of detecting farther distance, the peak power of a laser is increased correspondingly continuously, and the signal intensity of a reflected echo is also increased continuously. A problem that follows is that the echo signal of a conventional fixed-gain transimpedance Amplifier (TIA) increases to cause saturation of the transimpedance Amplifier. This saturation delay is too long, resulting in the reflected echo signal being drowned in a saturated signal and not being detected.
Analyzing the reasons of the above problems, the enhancement of the echo signal leads to the output current I of the avalanche photodiode detectorapdAnd the enhanced fixed-gain trans-impedance amplifier is saturated immediately when a large current is input. If the intensity of the echo signal cannot be detected and fed back, the transimpedance amplifier at the rear end cannot adjust the gain of the avalanche photodiode detector according to the intensity of the echo signal currently incident to the avalanche photodiode detector.
To solve the above problem, a block diagram of a system design of a circuit system for processing an echo signal of a lidar avalanche photodiode detection circuit is shown in fig. 1. The avalanche photodiode 40 receives the laser doppler echo signal of the lidar and converts it into a current signal. The variable gain transimpedance amplifier 10 converts and amplifies the current signal into a voltage signal. The comparator 50 compares the voltage pulse signal formed by the variable gain trans-impedance amplifier 10 with a preset fixed level to obtain a result represented by a binary, and transmits the result to the signal control and processing module 30. The signal control and processing module 30 analyzes the characteristic quantities such as the position, the speed and the like of the target according to the comparison result, and transmits the characteristic quantities to a display screen for display. However, as described above, when the detection is performed in a short distance or the echo signal is strong, the voltage pulse signal formed by the variable gain transimpedance amplifier 10 may be saturated, and the high speed comparator 50 may be saturated, so that the signal control and processing module 30 cannot analyze the correct characteristic quantity.
Further, the present invention employs the variable gain transimpedance amplifier 10 and an Analog-to-Digital Converter 20 (ADC). The analog-to-digital converter 20 is used as an intensity signal acquisition system, samples the electrical signal converted by the variable gain transimpedance amplifier 10, and passes through the signal control and processing module 30, such as an FPGA/DSP. The signal control and processing module 30 generates a gain adjustment instruction based on the corresponding relationship between the light intensity information of the pre-calibrated laser doppler echo signal and the amplification gain of the variable gain transimpedance amplifier, and feeds back the current echo signal information. The variable gain transimpedance amplifier 10 adjusts the gain thereof in response to the gain adjustment command. Thereby changing the amplitude of the output pulse signal of the variable gain trans-impedance amplifier 10 by changing the gain thereof.
In particular, the magnitude of the current of the avalanche photodiode 40 is inversely proportional to the magnitude of the gain of the variable gain transimpedance amplifier 10, thereby ensuring that the variable gain transimpedance amplifier 10 exhibits a low gain when the echo signal is strong. Namely, the signal saturation phenomenon in the range of distance measurement is realized by calibrating the light intensity information output by the analog-to-digital converter 20 and adjusting the gain of the variable gain trans-impedance amplifier 10 with variable gain. That is, the pulse signal at the input terminal of the comparator 50 will change with the adjustment of the gain of the variable gain transimpedance amplifier 10, so as to avoid the occurrence of saturation.
According to a preferred embodiment of the present invention, the circuitry includes an avalanche photodiode 40, a variable gain transimpedance amplifier 10, an analog-to-digital converter 20 and a signal control and processing module 30. The avalanche photodiode 40, the variable gain transimpedance amplifier 10, the analog-to-digital converter 20 and the signal processing module 30 are electrically and/or communicatively connected with each other, and cooperate with each other to process the laser doppler echo signal received by the avalanche photodiode detection circuit (APD detection circuit).
The avalanche photodiode 40, i.e., APD, is used to receive and collect the laser doppler echo signal of the lidar. As previously described, laser light reflected from the target surface is scattered, and a portion of the scattered light signal is passed through a receiving optical system to focus the laser doppler echo signal onto the avalanche photodiode 40. Further, the laser doppler echo signal represents a doppler shift signal generated by mutual interference of the measurement light reflected by the target surface and the reference light. The avalanche photodiode is a PN junction type optical diode, and under the action of an applied reverse bias voltage, the initial photocurrent is increased due to an avalanche multiplication effect, so that the photoelectric detection is facilitated. The basic operating principles of doppler and avalanche photodiodes are known to those skilled in the art and will not be described in detail herein.
The variable gain trans-impedance amplifier 10 is a front-end amplifier of the avalanche photodiode 40, and is used for converting the output current I of the avalanche photodiode 40apdConverted into a voltage VoTIA. The variable gain transimpedance amplifier 10 converts the current into a voltage by operating a Resistor (RF) fed back across the transimpedance amplifier using ohm's law Vout-Ipd RF, as shown in fig. 2 and 3. Specifically, the avalanche photodiode APD can convert an optical signal carrying related information into an electrical signal, but the converted signal is in the form of a current signal, which is difficult to be directly processed by an analog circuit, so that it is necessary to convert the signal into an easily processed voltage signal by using an I/V conversion circuit, i.e., the variable gain transimpedance amplifier 10. The variable gain transimpedance amplifier 10 converts the current signal output from the avalanche photodiode 40 into a voltage signal with a predetermined amplification factor. Furthermore, the introduction of a feedback Capacitor (CF) can suppress circuit oscillation possibly generated in the transimpedance amplifier circuit, and increase the stability of the circuit. The feedback capacitor may be connected in parallel to a certain resistor of the transimpedance amplification circuit.
The variable gain transimpedance amplifier 10 further comprises a transimpedance amplifier and a gain adjuster for adjusting a gain value of the transimpedance amplifier. The transimpedance amplifier can be implemented as LTC6268 or LTC 6269. LTC6268/LTC6269 is a 500MHz, single/dual channel, FET input operational amplifier (Field effect transistor) with very low input bias current and low input capacitance. In addition, LTC6268/LTC6269 also has low input reference current noise and voltage noise, so the transimpedance amplifier is preferably LTC6268 or LTC 6269.
It is worth mentioning that, in order to realize the gain adjustability of the transimpedance amplifier, the gain adjuster of the circuit system includes a multi-channel switch logic control module and a plurality of corresponding resistors, such as R1, R2, R3 and R4 in fig. 4. The multi-channel switch logic control module is connected with the resistors in an electrifyable mode, and the resistance value is controlled by utilizing the opening and closing of the switch in the multi-channel switch logic control module, so that the gain value of the trans-impedance amplifier is adjusted. The regulating circuit formed by connecting the multi-channel switch logic control module and the resistor in combination can be arranged at the input end or the output end of the transimpedance amplifier. That is to say, the invention utilizes the multi-channel switch logic control module, the corresponding plurality of resistors and the transimpedance amplifier to form a TIA system with programmable gain function.
In one embodiment of the present invention, as shown in fig. 4, the multi-channel switch logic control module is implemented as a multi-channel single-pole single-throw switch (ADG 1611). The ADG1611 has ultra-low on-resistance characteristics, so a boost switch with low on-resistance and low distortion performance is a preferred embodiment. The single pole, single throw switch ADG1611 is connected to a plurality of precision resistors, and the gain value is set by controlling an external gain setting resistance value RF using these switches. Specifically, each switch in the ADG1611 is electrically connected to a corresponding resistor to form a parallel and/or series circuit. By controlling the number of closed switches or the closing of a certain switch, whether the corresponding resistor is connected into a circuit or not is controlled, so that the resistance value is controlled. Alternatively, other types of multi-channel switch logic control modules may be used by those skilled in the art, and the design and combination of resistors may be varied accordingly, and the invention is not limited thereto.
Through the cooperation of the multi-channel switch logic control module, the corresponding resistors and the transimpedance amplifier, the gain of the transimpedance amplifier can be controlled through switch control and resistance value setting, and the variable-gain transimpedance amplifier is formed. That is, the circuitry of the present invention provides a low power consumption, low cost programmable variable gain transimpedance amplifier solution.
When the output current I of the avalanche photodiode 40apdIs converted into a voltage VoTIAThe analog-to-digital converter 20 then samples it. In the process of collecting and processing the echo intensity data, the sampling rate of the collecting system has direct influence on the data precision of the echo signal and the analysis of the pulse signal. The general index pulse width is about 10ns, the repetition frequency is about 50kHz, and the rising time is about 5 ns. In order to ensure undistorted acquisition, at least one sampling point is ensured to be on the maximum value of the echo pulse amplitude when each echo comes, so that the data transmission and data processing capacity of the system are comprehensively considered, and an ADC with high sampling rate and high resolution is required. Preferably, the analog-to-digital converter 20 is a high-speed analog-to-digital converter, AD9430, available from ADI (analog devices) Inc. The AD9430 has 12 bits, 170/210MSPS, 3.3V supply, 700MHz full power analog bandwidth, and signal-to-noise ratio (SNR): 65dB (Fin is 70MHz at most, 210MSPS) and the like.
In one embodiment of the present invention, a block diagram of a high speed data acquisition circuit design is shown in fig. 5. The high speed data acquisition circuit includes a transformer and the AD 9430. The transformer receives a voltage signal transmitted from the variable gain transimpedance amplifier 10 at the front end. At this time, the voltage signal transmitted by the variable gain transimpedance amplifier 10 is an intermediate frequency signal single-ended signal. The intermediate frequency single-ended signal is converted to a differential signal by the transformer and transmitted to the AD 9430. That is, the AD9430 uses differential signal input, which has good rejection of common mode signals.
Simply stated, a single-ended signal is the difference in level between ground and the signal transmitted on a single conductor; and the differential signal refers to a signal transmitted by two lines, and a level difference between the two signals is transmitted. The conversion method and principle of single-ended signal to differential signal are known to those skilled in the art and will not be described herein.
The AD9430 collects the pulse intensity signal and transmits the signal to the signal control and processing module 30 for analysis and processing. The signal control and processing module 30 determines whether the pulse intensity signal acquired by the AD9430 is saturated or not, or the variation trend thereof, and forms the gain adjustment instruction based on the corresponding relationship between the light intensity information of the pre-calibrated laser doppler echo signal and the amplification gain of the variable gain transimpedance amplifier. The gain adjustment command is fed back to the multi-channel switch logic control module of the variable gain transimpedance amplifier 10. The multichannel switch logic control module controls the on and off of the corresponding switch according to the gain adjusting instruction, adjusts the TIA gain and effectively eliminates the problem of saturation of the APD strong echo signal.
The Signal control and Processing module 30 is preferably an FPGA (Field-Programmable gate array), a DSP (Digital Signal Processing), or a combination thereof. The basic working principle and working mode of the FPGA/DSP will be known to those skilled in the art, and will not be described herein.
It is worth mentioning that Avalanche Photodiodes (APDs) convert the magnitude of the current IapdIs inversely proportional to the front-end variable gain trans-impedance amplifier (TIA) gain magnitude. That is, when IapdThe larger the value of (3), the smaller the gain of the transimpedance amplifier is, the smaller the possibility that the voltage converted by the corresponding transimpedance amplifier is saturated is, and therefore the possibility of occurrence of the saturation phenomenon of the APD detection circuit is reduced.
Further, the circuitry includes the comparator 50. The weak pulse analog signal (millivolt level) output by the variable gain transimpedance amplifier 10 is subjected to one-bit analog-to-digital conversion by the comparator 50, and a digital signal is provided for the signal control and processing module 30. The comparator 50 is a circuit that compares an analog voltage signal with a reference voltage, and has an input of the analog signal and an output of the binary signal 0 or 1, and the output is kept constant when the difference between the input voltages increases or decreases and the signs are unchanged. In the present invention, the comparator 50 is utilized to compare the output signal of the avalanche photodiode 40 with a preset fixed level by adopting a leading edge time timing transmission mode, and the output result of the comparator 50 is a TTL level (Transistor-Transistor Logic), i.e. a binary representation data result is the signal control sum of the back endThe processing module 30 provides a processing signal. That is, the output current I of the avalanche photodiode 40apdIs converted into a voltage VoTIAThis is then compared by the comparator 50 with a preset fixed level, resulting in a binary signal representation. The preset fixed level value can be obtained according to inherent noise calibration of the detection circuit.
In one embodiment of the present invention, the comparator 50 is a rail-to-rail, 2.5V to 5.5V, single power TTL/CMOS ultra fast comparator with a transmission delay of 3.5ns, using a high speed comparator ADCMP600 from adi (analog devices) inc. As shown in the figure. The ADCMP600 pin Q is a comparator output end, the pin VCCI/VCCO is a power supply end, the pin Vp is a non-inverting input end, and the pin Vn is an inverting input end. When the circuit works, when Vp is larger than Vn, the pin Q is set to be high level; if Vp < Vn, the pin Q is set to low level, and a corresponding digital pulse signal is formed.
In use, as shown in fig. 6, the pulse signal converted by the variable gain transimpedance amplifier 10 has the pin Vp as an input port, and the voltage input at the pin Vn as a reference voltage. The ADCMP600 converts the analog signal to a digital pulse digital level signal quickly via internal conversion.
That is, the variable gain transimpedance amplifier 10 adjusts the gain in accordance with the gain adjustment instruction of the signal control and processing module 30 in inverse proportion to the current of the avalanche photodiode. Correspondingly, the converted voltage signal of the variable gain trans-impedance amplifier 10 is adjusted correspondingly. The adjusted voltage pulse signal is inputted through the Vp terminal of the ADCMP600, and the voltage inputted through the Vn terminal is used as a reference voltage. The comparator 50 compares the adjusted voltage pulse signals to form corresponding digital pulse signals, so that the signal control and processing module 30 can analyze the characteristic quantity of the target object. Compared with the existing processing circuit system, the current magnitude of the APD has less influence on the measurement result and can be correspondingly and controllably adjusted, so that the detection distance of the whole APD detection circuit is increased, especially when the short-distance detection and the echo signal are stronger.
According to another aspect of the present invention, the present invention further provides a laser doppler echo signal processing method for a laser radar. Fig. 8 is a flowchart of a laser doppler echo signal processing method for a lidar according to the present invention. The echo signal processing method of the present invention can be implemented by using the aforementioned circuit system, thereby achieving the objects and advantages of the present invention.
Step 110: the echo signal of the avalanche photodiode detection circuit is converted into a current.
The conversion of the echo signal into a current signal may be performed by an avalanche photodiode in the above-described circuitry. The echo signal of the avalanche photodiode detection circuit is received and collected to the avalanche photodiode, and is converted into a current signal through the avalanche photodiode.
Step 120: converting the current into a voltage through a variable gain trans-impedance amplifier;
the transimpedance amplifier converts a current signal into a voltage signal by operating a Resistor (RF) fed back across the transimpedance amplifier using ohm's law Vout — Ipd RF.
Step 130: and sampling and analyzing the converted voltage signal, and forming a gain adjusting instruction based on the corresponding relation between the light intensity information of the pre-calibrated laser Doppler echo signal and the amplification gain of the variable gain trans-impedance amplifier.
Voltage signal sampling can be achieved by using a high sampling rate, high resolution high speed analog to digital converter ADC. Preferably, the ADC is a high speed ADC, AD9430, of ADI (analog devices) USA. The analysis and processing of the sampled signals can be realized by using FPGA and/or DSP, and the invention is not limited.
Preferably, in the correspondence between the pre-calibrated light intensity information of the laser doppler echo signal and the amplification gain of the variable gain transimpedance amplifier, the light intensity information of the laser doppler echo signal and the amplification gain of the variable gain transimpedance amplifier have an inverse relationship.
Step 140: and the multi-channel switch logic control module adjusts the gain value of the variable gain trans-impedance amplifier according to the gain adjusting instruction.
The adjustment of the gain value of the trans-impedance amplifier is realized by controlling the correspondingly connected resistors through the multi-channel switch logic control module. According to the adjustment scheme, the current value of the echo signal after being converted by the avalanche photodiode is inversely proportional to the gain value of the transimpedance amplifier, and after the multichannel switch logic control module is executed according to the adjustment scheme, the gain value of the variable gain transimpedance amplifier is inversely proportional to the current value, so that the saturation condition is avoided.
Step 150: and comparing the adjusted pulse signal output by the variable gain trans-impedance amplifier with a preset fixed level to form a corresponding digital pulse signal.
The formation of the digital pulse signal may be accomplished by a high speed comparator, preferably an ADCMP600 using the ADI (analog devices) high speed comparator.
Step 160: and analyzing the characteristic quantity of the target object according to the digital pulse signal.
The foregoing describes the general principles of the present application in conjunction with specific embodiments, however, it is noted that the advantages, effects, etc. mentioned in the present application are merely examples and are not limiting, and they should not be considered essential to the various embodiments of the present application. Furthermore, the foregoing disclosure of specific details is for the purpose of illustration and description and is not intended to be limiting, since the foregoing disclosure is not intended to be exhaustive or to limit the disclosure to the precise details disclosed.
The block diagrams of devices, apparatuses, systems referred to in this application are only given as illustrative examples and are not intended to require or imply that the connections, arrangements, configurations, etc. must be made in the manner shown in the block diagrams. These devices, apparatuses, devices, systems may be connected, arranged, configured in any manner, as will be appreciated by those skilled in the art. Words such as "including," "comprising," "having," and the like are open-ended words that mean "including, but not limited to," and are used interchangeably therewith. The words "or" and "as used herein mean, and are used interchangeably with, the word" and/or, "unless the context clearly dictates otherwise. The word "such as" is used herein to mean, and is used interchangeably with, the phrase "such as but not limited to".
It should also be noted that in the devices, apparatuses, and methods of the present application, the components or steps may be decomposed and/or recombined. These decompositions and/or recombinations are to be considered as equivalents of the present application.
The previous description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departing from the scope of the application. Thus, the present application is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
The foregoing description has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit embodiments of the application to the form disclosed herein. While a number of example aspects and embodiments have been discussed above, those of skill in the art will recognize certain variations, modifications, alterations, additions and sub-combinations thereof.
It will be appreciated by persons skilled in the art that the embodiments of the invention described above and shown in the drawings are given by way of example only and are not limiting of the invention. The objects of the invention have been fully and effectively accomplished. The functional and structural principles of the present invention have been shown and described in the examples, and any variations or modifications of the embodiments of the present invention may be made without departing from the principles.
Claims (17)
1. A laser Doppler echo signal processing method for a laser radar is characterized by comprising the following steps:
processing the obtained laser Doppler echo signal through an avalanche photodiode to convert the laser Doppler echo signal into a current signal;
converting the laser Doppler echo signal converted into the current signal into a voltage signal through a variable gain trans-impedance amplifier, wherein the variable gain trans-impedance amplifier comprises the trans-impedance amplifier and a gain adjuster used for adjusting the gain value of the trans-impedance amplifier;
sampling the laser Doppler echo signal converted into a current signal;
processing the sampled laser Doppler echo signal to generate a gain adjusting instruction based on the corresponding relation between the light intensity information of the pre-calibrated laser Doppler echo signal and the amplification gain of the variable gain trans-impedance amplifier;
adjusting, by the gain adjuster, a gain value of the variable gain transimpedance amplifier in response to the gain adjustment instruction; and
and comparing the pulse signal output by the gain-adjusted variable gain trans-impedance amplifier with a preset level to generate a laser Doppler echo signal processing result.
2. The method of claim 1, wherein an inverse relationship exists between the light intensity information of the laser doppler echo signal and the amplification gain of the variable gain transimpedance amplifier in a correspondence relationship between the light intensity information of the laser doppler echo signal and the amplification gain of the variable gain transimpedance amplifier.
3. The laser doppler echo signal processing method according to claim 2, wherein sampling the laser doppler echo signal converted into the current signal includes:
and sampling the laser Doppler echo signal converted into the current signal by a high-speed analog-to-digital converter, wherein the high-speed analog-to-digital converter can ensure that at least one sampling point is on the maximum value of the echo pulse peak value of the laser Doppler echo signal.
4. The laser doppler echo signal processing method according to claim 2 or 3, wherein the gain adjuster includes a multi-channel switch logic control module, and a plurality of resistors having different resistance values corresponding to the number of channels and electrically connectable to the multi-channel switch logic control module, wherein adjusting the gain value of the variable gain transimpedance amplifier by the gain adjuster in response to the gain adjustment instruction includes:
in response to the gain adjustment instruction, the multi-channel switch logic control module switches the resistor conducted with the transimpedance amplifier to adjust a gain value of the transimpedance amplifier.
5. The laser doppler echo signal processing method according to any one of claims 1 to 4, wherein the multi-channel switch logic control module is implemented as a multi-channel single-pole single-throw switch (ADG) 1611.
6. A laser Doppler echo signal processing method according to any one of claims 1 to 4, wherein the transimpedance amplifier is implemented as LTC6268 or LTC 6269.
7. The laser doppler echo signal processing method of claim 3, wherein the high-speed analog-to-digital converter is implemented as AD 9430.
8. Circuitry for processing a laser doppler echo signal of a lidar comprising;
an avalanche photodiode, wherein the avalanche photodiode converts the acquired laser doppler echo signal into a current signal;
a variable gain transimpedance amplifier which converts the laser Doppler echo signal converted into the current signal into a voltage signal; and
and the signal control and processing module analyzes a voltage signal sample, and forms a gain adjusting instruction based on the corresponding relation between the light intensity information of the pre-calibrated laser Doppler echo signal and the amplification gain of the variable gain transimpedance amplifier, wherein the variable gain transimpedance amplifier adjusts the gain value according to the gain adjusting instruction.
9. The circuitry of claim 8, wherein the light intensity information of the laser doppler echo signal is in an inverse relationship with the amplification gain of the variable gain transimpedance amplifier in a correspondence between light intensity information of a pre-calibrated laser doppler echo signal and the amplification gain of the variable gain transimpedance amplifier.
10. The circuitry of claim 8, wherein the variable gain transimpedance amplifier comprises a transimpedance amplifier and a gain adjuster for adjusting a gain value of the transimpedance amplifier, wherein the gain adjuster further comprises a multi-channel switch logic control module and a corresponding plurality of resistors, wherein the multi-channel switch logic control module is electrically connectable to the plurality of resistors, wherein the multi-channel switch logic control module controls opening and closing of its switches to control resistance values in response to the adjust gain command to adjust the gain value of the transimpedance amplifier.
11. The circuitry of claim 10, wherein the multi-channel switch logic control module is implemented as a multi-channel single pole single throw switch (ADG) 1611.
12. The circuitry of any one of claims 8 to 11, further comprising a high speed analog to digital converter, wherein the high speed analog to digital converter samples the voltage signal and transmits the sampled voltage signal to the signal control and processing module, wherein the high speed analog to digital converter is capable of ensuring that at least one sample point is at a maximum of an echo pulse peak of the laser doppler echo signal.
13. The circuitry of claim 12, wherein the high-speed analog-to-digital converter is implemented as AD 9430.
14. The circuitry of claim 10, wherein the transimpedance amplifier is implemented as LTC6268 or LTC 6269.
15. The circuitry of any of claims 8 to 11, wherein the signal control and processing module is implemented as an FPGA, a DSP, or a combination of both.
16. The circuit system according to any one of claims 8 to 11, further comprising a high speed comparator, wherein the high speed comparator uses a leading edge timing transmission mode to compare the voltage signal converted by the variable gain transimpedance amplifier with a preset fixed level, and outputs a corresponding digital pulse signal to the signal control and processing module for analyzing a characteristic quantity of a target.
17. The circuitry of claim 16, wherein the high speed comparator is implemented as ADCMP 600.
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