A lidar pulse peak adaptive detection and fitting ranging system

Abstract

The present invention relates to the field of active remote sensing technology and discloses a laser radar pulse peak adaptive detection and fitting ranging system. The system includes an improved constant ratio timing module, a peak hold and main control sampling module, a drive comparison module, and a moment identification fitting module. The improved constant ratio timing module is connected to the peak hold and main control sampling module and the drive comparison module, the peak hold and main control sampling module is connected to the drive comparison module, and the drive comparison module is connected to the moment identification fitting module. The present invention processes signals from various modules of the system to output a rectangular pulse signal that maintains the amplitude characteristics of the received signal and has a steep rising edge characteristic, while simultaneously outputting accurate pulse amplitude data. This rectangular pulse signal is used to trigger a moment identification signal, significantly reducing the running error caused by the different times when the rising edges of signals with different input amplitudes reach a fixed threshold. Ultimately, accurate ranging is achieved through time-to-digital conversion and fitting correction.

Description

Technical Field

[0001] The present invention relates to the field of active remote sensing technology, and in particular to a laser radar pulse peak adaptive detection and fitting ranging system. Background Art

[0002] LiDAR technology is primarily used in active remote sensing, offering advantages such as high precision, strong anti-interference capabilities, and a wide detection range. However, with the continuous advancement of laser technology, radar often operates over a wide range of distances. LiDAR's transmitted pulses have narrow pulse widths and high repetition rates, making the acquisition of received signals difficult and prone to signal loss. This also places extremely high demands on the processing speed and response time of the detection circuitry. When the target is far from the laser transmitter, the echo signal is weak, and the electrical signal output by the photodetector is also very weak. Therefore, reducing travel errors, improving ranging accuracy, and accurately detecting the peak value of the received pulse are currently challenging challenges.

[0003] Existing LiDARs primarily use avalanche photodiodes (APDs) to convert received laser light signals into current signals, and then use variable transconductance amplifiers (TIAs) for I / V conversion to obtain received pulses and transmit them to the subsequent time identification system. Based on existing research results, there are three typical signal time identification systems:

[0004] The first method is the leading edge moment identification method. A high-speed comparator compares the input pulse signal with a set reference voltage. A trigger signal is generated at the instant the input pulse signal exceeds the reference voltage, recording the moment the pulse is received. Because the received pulse amplitude has a large dynamic range, amplitude variations in this method can produce significant ranging errors, affecting ranging accuracy.

[0005] The second method is zero-crossing identification. By converting a unipolar pulse signal into a bipolar signal and using a zero-crossing comparator to record the moment the laser receives the pulse, zero-crossing identification is insensitive to changes in the input signal's amplitude and can address measurement errors caused by pulse amplitude variations. However, zero-crossing identification is affected by the slope near the pulse peak, and the pulse width can also introduce measurement errors.

[0006] The third method is the constant ratio timing identification method. The input signal is divided into two paths, one of which is attenuated and the other delayed. A high-speed comparator is used to compare the two signals, and the moment when the two signals are exactly equal is used as the moment of pulse reception. This method has a relatively good application effect for signals within a certain amplitude range. However, the design of a high-precision delay system in the constant ratio timing identification system is difficult. Existing methods use RC / LC network delays or delay lines, which respectively suffer from waveform distortion and long delay lines. Furthermore, this method cannot reduce the time jitter error generated by input signals with a large dynamic range, resulting in non-negligible ranging errors.

[0007] In terms of the detection of lidar narrow pulse signals, according to existing research results, there are currently two acquisition methods for narrow pulse detection: direct acquisition and indirect acquisition.

[0008] Direct acquisition methods primarily sample high-frequency signals through high-speed analog-to-digital converters (ADCs). While this method offers high accuracy, it also has significant drawbacks. First, high-speed ADCs are very expensive, significantly increasing design and application costs. Second, due to their high sampling frequency, conventional processors cannot analyze the data collected by the ADC in a timely manner, and even FPGAs are very difficult to process.

[0009] The indirect acquisition method primarily pre-processes the narrow pulses received by the lidar to perform peak hold and ADC processing, thereby reducing ADC acquisition performance requirements and processor processing power. Its advantages of large design space and low design cost have led to its widespread adoption. However, due to the slow voltage drop during the peak hold process, improper sampling timing can lead to inaccurate amplitude data.

[0010] In summary, the existing moment identification scheme has problems such as insufficient ranging accuracy and large walking error. The existing narrow pulse peak detection scheme has problems such as difficulty in direct sampling and inaccurate indirect sampling. To this end, we proposed a lidar pulse peak adaptive detection and fitting ranging system. Summary of the Invention

[0011] (1) Technical problems solved

[0012] In view of the shortcomings of the existing technology, the present invention provides a laser radar pulse peak adaptive detection and fitting ranging system to solve the above problems.

[0013] (2) Technical solution

[0014] To achieve the above-mentioned purpose, the present invention provides the following technical solutions:

[0015] A laser radar pulse peak adaptive detection and fitting ranging system includes an improved constant ratio timing module, a peak hold and main control sampling module, a drive comparison module and a moment identification and fitting module. The improved constant ratio timing module is connected to the peak hold and main control sampling module and the drive comparison module, the peak hold and main control sampling module is connected to the drive comparison module, and the drive comparison module is connected to the moment identification and fitting module.

[0016] Preferably, the improved constant ratio timing module is composed of a two-stage feedback amplifier OPA2652 to form a delay circuit, a fixed gain amplifier AD8009 to form an amplification circuit, a dual high-speed comparator TLV3501 to form a high-speed comparison circuit and a monostable trigger 74LV123 to form a synchronous trigger circuit. The delay circuit and the amplification circuit are both connected to the high-speed comparison circuit, and the high-speed comparison circuit is connected to the synchronous trigger circuit.

[0017] Preferably, the peak hold and main control sampling module is composed of a transconductance amplifier, a Schottky diode, a holding capacitor, a voltage buffer and a main control sampling unit for obtaining a synchronous trigger signal and a peak hold signal. The transconductance amplifier includes a first-stage transconductance amplifier and a second-stage transconductance amplifier connected to the front end of the laser radar. The voltage buffer is connected to the main control sampling unit, and the main control sampling unit is connected to the synchronous trigger circuit.

[0018] Preferably, the drive comparison module is composed of a logic NOT gate for obtaining an initial drive signal, a high-speed switch NMOS tube for obtaining a peak hold signal, a high-speed comparator for obtaining an amplitude characteristic rectangular pulse signal, and a voltage follower connected to the high-speed comparator.

[0019] Preferably, the moment identification fitting module is composed of a time-to-digital converter GP22, a main control unit and a terminal fitting device. The time-to-digital converter uses the START signal emitted by the laser radar as a start signal, and the moment identification STOP signal received and generated by the receiving end is used as a stop signal.

[0020] (3) Beneficial effects

[0021] Compared with the existing technology, the present invention provides a laser radar pulse peak adaptive detection and fitting ranging system, which has the following beneficial effects:

[0022] 1. The laser radar pulse peak adaptive detection and fitting ranging system maintains the peak value of the Gaussian pulse signal and intercepts the stable amplitude portion by driving the high-speed on-off of the NMOS tube, generating a rectangular pulse signal with the stable amplitude characteristic of the Gaussian pulse signal, which has steep rising and falling edges. This signal is used to identify the signal at the triggering moment of the comparator, thereby significantly reducing the walking error caused by the different times when Gaussian pulse signals of different amplitudes reach the fixed threshold, and achieving accurate ranging.

[0023] 2. This LiDAR pulse peak adaptive detection and fitting ranging system leverages the capacitance differences of the charging and discharging components of a two-stage peak hold circuit to achieve fast charging, precise amplitude, and long-term hold. Finally, a synchronous trigger signal triggers the main controller to perform A / D conversion and output amplitude data. Simultaneously, a rectangular pulse signal with stable Gaussian pulse amplitude characteristics is used for oscilloscope peak reading, providing dual assurance of accurate reading.

[0024] 3. The laser radar pulse peak adaptive detection and fitting ranging system provides an amplification and delay scheme with the advantages of no distortion of the delayed waveform and a large difference between the amplified signal and the delayed signal at the same time. It achieves the compression of the error range of the triggering comparator and ensures the identity of the intersection of the two signals.

[0025] 4. The laser radar pulse peak adaptive detection and fitting ranging system adopts a two-stage transconductance peak holding circuit. By improving the differences between the two charging and discharging circuits, the first-stage peak holding mainly realizes the functions of fast charging and accurate peak holding, and the second-stage peak holding mainly realizes the function of accurately maintaining the peak for a long time.

[0026] 5. This lidar pulse peak adaptive detection and fitting ranging system uses an improved constant timing module to output an initial drive signal. This signal is in the period of accurate peak hold, and the drive signal is obtained by amplitude inversion through a logic NOT gate. When the peak hold signal is in the amplitude rising phase or in the amplitude gradually declining phase, the NMOS transistor is turned on, and the output signal is grounded to zero. When the peak hold signal is in the accurate peak hold phase, the NMOS transistor is turned off, and the output is a stable rectangular pulse signal with steep rising and falling edges. The pulse amplitude is the input signal amplitude and there is no amplitude droop.

[0027] 6. The laser radar pulse peak adaptive detection and fitting ranging system, for the Gaussian pulse signal output by the laser radar receiving front end, the traditional solution always maintains the Gaussian characteristics of the received signal for signal conditioning and ranging. The present invention, through signal processing of each module of the system, outputs a rectangular pulse signal that maintains the amplitude characteristics of the received signal and has a steep rising edge characteristic, while outputting precise pulse amplitude data. This rectangular pulse signal is used to trigger the identification signal, significantly reducing the walking error caused by the different times when the rising edges of signals with different input amplitudes reach the fixed threshold. Ultimately, accurate ranging is achieved through time-to-digital conversion and fitting correction. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of the system module structure and flow chart of an embodiment of the present invention;

[0029] Figure 2This is a schematic structural diagram of an improved constant ratio timing module according to an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the structure of the peak hold and master control sampling module according to an embodiment of the present invention;

[0031] Figure 4 Schematic diagram of the drive comparison module structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] Example

[0034] See also Figure 1-4 The laser radar pulse peak adaptive detection and fitting ranging system provided by the embodiment of the present invention includes an improved constant ratio timing module, a peak hold and main control sampling module, a drive comparison module and a time identification fitting module. Its core modules and working principles are as follows: Figure 1 As shown in the figure, the Gaussian pulse signal output by the lidar receiver front-end undergoes three signal processing steps. Two of the signals enter the improved constant-ratio timing module, where they are conditioned by a delay circuit consisting of a two-stage broadband feedback amplifier and an amplification circuit consisting of a fixed-gain amplifier. The processed signals then enter a dual comparator to generate the initial drive signal. This signal triggers the master control sampling function through a synchronous trigger circuit and obtains the drive signal through a logic NOT gate. The third signal passes through a peak-hold circuit consisting of a two-stage transconductance amplifier, a two-stage charge-discharge circuit, and a one-stage buffer. This circuit generates a long-term, accurate peak-hold signal by charging and discharging the hold capacitor. This signal is input to an NMOS transistor driven by the drive signal for signal interception, outputting a rectangular pulse signal with the amplitude characteristics of the received pulse. This signal is then fed into a fixed-threshold high-speed comparator module to generate a time-to-digital converter (STOP) signal for time identification. This signal, along with the time-to-digital converter (START) signal, is then fed into the time-to-digital converter (TCC) to obtain measurement data. Finally, the fitting function is obtained by fitting the actual data and then burned into the lidar main control unit for automatic fitting ranging.

[0035] The improved constant ratio timing module is as follows: Figure 2As shown in the figure, the delay circuit consists of a two-stage feedback amplifier OPA2652, the amplification circuit consists of a fixed-gain amplifier AD8009, the high-speed comparison circuit consists of a dual high-speed comparator TLV3501, and the synchronous trigger circuit consists of a 74LV123 monostable flip-flop. The OPA2652 is a dual low-power, wideband voltage feedback operational amplifier. Each channel is internally compensated to provide unity-gain stability. Two OPA6752 operational amplifiers are cascaded, each forming a single-pole active all-pass filter, resulting in an overall gain of +1. The total delay through the filter is:

[0036] t=n(2RC) (1)

[0037] Where n is the number of cascade stages, R is the value of the parallel resistor, and C is the value of the series capacitor. The parallel resistors R must be equal to maintain a constant gain. The module operates by delaying the Gaussian pulse signal received by the lidar by 8ns through a two-stage feedback amplifier and then amplifying it with a small gain through a fixed-gain amplifier. The two processed signals then pass through a high-speed dual comparator. When the delayed signal amplitude exceeds the amplified signal amplitude, the comparator is triggered, outputting a high-level signal. This signal serves as the initial drive signal to the driver switching circuit. Simultaneously, it is triggered by the 74LV123 monostable trigger to become the synchronous trigger signal. Since narrow pulses cannot trigger the main control module, the 74LV123 adjusts the pulse width of the high-level signal to trigger the main control module for sampling.

[0038] The peak hold and master sampling modules are as follows Figure 3As shown, the module consists of a MAX436ESD transconductance amplifier, a BAT17 Schottky diode, a hold capacitor, an OPA2354 voltage buffer, and an STM32F103ZET6 master sampling unit. The MAX436ESD used in the module is a high-speed, wideband transconductance operational amplifier with positive differential high-impedance inputs. It provides stable and accurate current gain without any feedback. Its function is to convert voltage input into current output and control the operating current of the op amp via an external bias voltage, allowing the output current to vary over a wide range. Its wide passband and excellent stability make it suitable for processing nanosecond-speed signals. The OPA2354 voltage buffer in the module is a high-speed voltage-feedback CMOS operational amplifier that improves the circuit's drive capability and interference immunity. The most critical characteristics of a peak sampling circuit are its linearity and stability. Peak hold linearity refers to the linearity of the ratio of the output signal to the input signal and is determined by the amplifier, diode, and sample-and-hold capacitor. The larger the linear output range of the amplifier, the shorter the reverse recovery time of the diode, the smaller the capacitance, and the better the linearity of the peak sampling output. The stability of peak hold refers to the fluctuation of the sampling signal and the length of time it is held when the input signal remains unchanged. It is determined by the holding capacitor. The larger the capacitance, the more stable the peak sampling and the longer the hold time. There is a contradiction between the linearity and stability of the peak sampling circuit, that is, the size of the capacitor. If it is too large, the linearity is poor, and if it is too small, it is unstable. Therefore, after experimental analysis, for a laser pulse signal with a rise time of about 15ns, the holding capacitor is generally 30 to 100pF. The voltage Vc and charging current It across the holding capacitor can be expressed as:

[0039]

[0040] I t =G(V i (t)-V o (t)) / Z (3)

[0041] Where It is the charging current, T0 is the charging start time, Tc is the charging duration, C is the charging capacitor value, Vi(t) and Vo(t) are the input and output signal amplitudes, G represents the transconductance amplification factor, and Z is the equivalent impedance of the diode and peak-hold capacitor. The module's operating principle is that when the output signal Vout is less than the input signal Vin, the transconductance amplifier amplifies the difference between the input and output voltages. The input voltage or current charges the holding capacitor through the diode. When the capacitor voltage equals the input voltage, the amplifier's voltage output reverses, the diode cuts off, and the capacitor discharges through the bleeder resistor. The module utilizes a two-stage peak-hold circuit, enabling fast charging while ensuring the accuracy of the peak-hold voltage. Therefore, for the first-stage charge-discharge circuit, the holding capacitor has a small capacitance to ensure fast charging and accurate peak value. For the second-stage charge-discharge circuit, the holding capacitor has a larger capacitance to increase the peak-hold time and stabilize the peak value. Finally, the peak hold signal is output through the buffer, and the master sampling unit performs sampling, holding, quantization, and encoding under the action of the synchronous trigger signal to realize A / D conversion, accurately read the pulse peak value and output the amplitude data.

[0042] The driving comparison module is as follows Figure 4 As shown, it consists of a 74LS04 logic NOT gate, a high-speed NMOS switch, a high-speed comparator TLV3501, and an ADA4665 voltage follower. The TLV3501 can be used to waveform-shape the input signal and output a TTL-level signal. It has a fast 4.5ns propagation delay and a wide input signal bandwidth, accepting signals from 0.1Hz to 230MHz, meeting the requirements of the present invention. The ADA4665 rail-to-rail chip is used to increase input impedance. Because the output impedance of the external input is relatively low, this is necessary to improve threshold voltage accuracy. The module's operating principle is that the initial drive signal output by the constant ratio timing module is converted into a drive signal through a logic NOT gate, performing level inversion. When the drive signal is high, the NMOS turns on, and the signals during the amplitude rise and amplitude fall phases of the peak hold process are grounded. When the drive signal is low, the NMOS turns off, outputting the signal during the stable peak phase of the peak hold signal, thereby capturing the signal waveform during the peak hold period. Because the captured waveform is relatively stable in amplitude, corresponding to the amplitude of the Gaussian pulse output by the LiDAR's front-end receiver, this processing yields a rectangular pulse signal with the amplitude characteristics of the received signal. This signal also exhibits steep rising and falling edges, with a rise time in the picosecond range. Therefore, this signal is fed into a fixed-threshold high-speed comparator, significantly reducing the travel error caused by varying signal amplitudes leading to different threshold-reaching times. The STOP signal is then identified at the moment of a stable output with a short rise time.

[0043] The moment identification and fitting module consists of a time-to-digital converter (GP22), a main control unit, and a terminal fitting device. The time-to-digital converter uses the START signal emitted by the laser radar as a start signal, and the moment identification STOP signal received and generated by the receiving end as a stop signal. Utilizing the digital delay line technology of complementary metal oxide semiconductor gate delays within the time-to-digital converter, after the start signal enters the time-to-digital converter's delay system, it propagates along the delay line, and the number of delay units passed between the start signal and the stop signal is calculated. The time difference between the transmitted pulse and the received pulse is thus calculated, and this time difference is stored in the main control module STM32, providing the laser radar system with high-precision time difference information for distance calculation. Initial ranging is performed using the initial algorithm in the STM32, and terminal fitting is performed on the actual distance to generate a linear fitting function. The re-burned STM32 completes the subsequent reception of self-fitting and precise ranging.

[0044] The measurement data fitting scheme of the present invention uses the CFTOOL toolbox of Matlab software to call the power approximation function model f=a*x b +c, where f is the fitting data, a is the weight of the measurement data x, and c is the compensation constant. The measurement data is obtained through lidar ranging, and the real data is obtained through standard lidar ranging. By performing terminal fitting of the test data and the real data in MATLAB, a linear fitting function is derived, and finally the fitting function is input into the main control unit to realize the automatic fitting and accurate ranging of the lidar system. In order to better reflect the ranging performance of the system, ranging accuracy is introduced as a performance indicator. Ranging accuracy is used to estimate the system error of the lidar ranging system. Generally, the average value of the difference between the measured value and the true value of the distance is taken as the accuracy of the system. Let E acu is the accuracy, R j is the measured value, R true is a real value, and its expression is as follows:

[0045]

[0046] The principle of reducing the running error of the improved constant ratio timing module is as follows: the traditional constant ratio timing is to input the received signal into the delay and attenuation circuit. The two signal waveforms intersect at the rising edge of the attenuation signal. The comparator flip point is located at the intersection of the attenuation signal and the delayed signal, generating a trigger time independent of the peak height, thereby reducing the timing error. However, because the traditional delay circuit adopts an RC structure, the rising structure will cause a certain degree of waveform distortion, which is easy to cause intersection error. Although the traditional resistor divider circuit can well realize the attenuation function of the pulse signal, the pure resistor divider structure will cause the synchronous attenuation of the signal DC level, which easily prevents the attenuation signal and the delayed signal from generating an intersection, and the comparator cannot flip. And because the comparator does not have an ideal zero-crossing response characteristic, when the delayed signal is greater than the attenuation signal, the comparator cannot be triggered immediately. The comparator can only be triggered when the difference between the two is greater than a certain value. Therefore, at the same time, the larger the signal, the greater the difference, and the easier it is to trigger the comparator; similarly, the smaller the signal, the smaller the difference, and it is necessary to delay for a certain time before triggering the comparator. The above reasons thus cause the running error of received signals of different amplitudes. The present invention is different from traditional solutions. Not only does it use a two-stage broadband feedback amplifier to achieve a distortion-free waveform delay with a gain of +1, but its delay degree can also be adjusted over a wide range by changing the capacitance and resistance values. At the same time, due to the use of a solution in which the delayed and amplified two-way signals intersect at the falling edge for comparison, the difference between the two signals at the same time is greater than that of the traditional solution, making it easier to trigger the high-speed comparator, thereby reducing the running error and generating an initial drive signal for the subsequent stage, ensuring that the stage of the initial drive signal is the optimal stage for maintaining the signal peak.

[0047] The driving comparison module reduces running errors and adaptively and accurately reads pulse amplitudes using the following principles: The initial driving signal and synchronous trigger signal provided by the constant ratio timing module determine the timing for driving the NMOS high-speed switch and the timing for the main control unit's A / D conversion. This timing falls during the precise peak hold period, allowing a portion of the peak hold signal waveform, which maintains constant amplitude, to be intercepted. This results in a rectangular pulse signal with picosecond-level rising and falling edges and a stable amplitude. The pulse peak is then accurately read using an oscilloscope, achieving dual peak adaptive detection for both main control acquisition and oscilloscope reading. Furthermore, because the rising and falling edges of this rectangular pulse signal are steep and change in picosecond time, even for signals with a large dynamic range, the problem of different amplitudes triggering the comparator at different times due to different rising edges reaching the fixed threshold is significantly improved, thereby reducing ranging running errors.

[0048] The principle of reducing the difficulty of peak sampling by the peak hold and master sampling modules is that traditional diode-type and voltage-type peak hold circuits have large nonlinearity, small dynamic range and passband, and are not suitable for processing narrow pulse high-speed signals. Compared with the other two types of peak hold circuits, the transconductance peak hold circuit has better dynamic characteristics, faster response speed, and low loss. It has significant advantages in high-sensitivity measurement applications and is suitable for processing high-speed narrow pulse signals. However, the traditional transconductance peak hold is a single-stage peak hold. Due to the short peak hold time, if the hold time is increased by increasing the hold capacitance, the increase in capacitor discharge time will affect the accuracy of the peak hold of the next-stage signal; if the hold capacitance is reduced to achieve the purpose of accurate peak hold, the peak hold time will be short due to the fast discharge speed. Therefore, the traditional single-stage peak hold has difficulty in achieving both fast charging and long-term accurate peak voltage maintenance. The two-stage peak hold solution provided by the present invention selects a smaller capacitor in the first-stage charge and discharge circuit to achieve fast charging and accurate peak hold, and selects a larger capacitor in the second-stage charge and discharge circuit to increase the peak hold time. The signal input through the two-level peak hold is sampled, held, quantized and encoded by the main control unit STM32, which reduces the requirements for the sampling frequency and thus reduces the difficulty of sampling. The long-term precise peak hold also significantly improves the sampling accuracy.

[0049] The operating principle of the system described in the present invention is to achieve a trigger point at a constant ratio by improving the constant ratio timing module, adaptively generating an initial drive signal and a synchronous trigger signal at the peak-overshoot stage. Simultaneously, the received pulse is precisely held for a long period of time through the combined action of a two-stage peak hold module. The synchronous trigger signal triggers the main control unit to perform A / D conversion. The peak hold signal, combined with the initial drive signal, a logical NOT gate, and a drive switch, generates a rectangular pulse signal with stable Gaussian pulse peak characteristics and a steep rising edge. This signal is then compared with a high-speed fixed threshold to rapidly identify the trigger moment. Ultimately, precise distance measurement is achieved through a time-to-digital converter and terminal fitting.

[0050] The laser radar pulse peak adaptive detection and fitting ranging system provided by the above-mentioned embodiment of the present invention, for the Gaussian pulse signal output by the laser radar receiving front end, the traditional solution always maintains the Gaussian characteristics of the received signal for signal conditioning and ranging. However, the present invention outputs a rectangular pulse signal that maintains the amplitude characteristics of the received signal and has a steep rising edge characteristic through signal processing of each module of the system, while outputting precise pulse amplitude data and using this rectangular pulse signal to trigger the moment identification signal, significantly reducing the walking error caused by the different times when the rising edges of signals with different input amplitudes reach the fixed threshold, and finally achieving accurate ranging through time-to-digital conversion and fitting correction.

[0051] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A laser radar pulse peak adaptive detection and fitting ranging system, characterized in that: It includes an improved constant ratio timing module, a peak hold and main control sampling module, a drive comparison module and a time identification and fitting module. The improved constant ratio timing module is connected to the peak hold and main control sampling module and the drive comparison module, the peak hold and main control sampling module is connected to the drive comparison module, and the drive comparison module is connected to the time identification and fitting module. The improved constant ratio timing module is composed of a two-stage feedback amplifier OPA2652 forming a delay circuit, a fixed gain amplifier AD8009 forming an amplification circuit, a dual-channel high-speed comparator TLV3501 forming a high-speed comparison circuit, and a monostable trigger 74LV123 forming a synchronous trigger circuit. The delay circuit and the amplification circuit are both connected to the high-speed comparison circuit, and the high-speed comparison circuit is connected to the synchronous trigger circuit. The peak hold and master sampling module is composed of a transconductance amplifier, a Schottky diode, a holding capacitor, a voltage buffer, and a master sampling unit that obtains a synchronous trigger signal and a peak hold signal. The transconductance amplifier includes a first-stage transconductance amplifier and a second-stage transconductance amplifier connected to the laser radar receiving front end. The voltage buffer is connected to the master sampling unit, and the master sampling unit is connected to the synchronous trigger circuit. The drive comparison module is composed of a logic NOT gate for obtaining the initial drive signal, a high-speed switch NMOS tube for obtaining the peak hold signal, a high-speed comparator for obtaining the amplitude characteristic rectangular pulse signal, and a voltage follower connected to the high-speed comparator; The moment identification fitting module is composed of a time-to-digital converter GP22, a main control unit and a terminal fitting device. The time-to-digital converter uses the START signal emitted by the laser radar as a start signal, and the moment identification STOP signal received and generated by the receiving end is used as a stop signal.

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