Anti-interference dynamically adjustable laser ranging system

Abstract

The application relates to the technical field of photoelectric distance measurement, in particular to an anti-interference laser distance measurement system capable of being dynamically adjusted, which comprises an optical structure unit, a main control and display unit, a laser modulation and emission unit, a laser receiving and conditioning unit and an APD avalanche diode module; the optical structure unit comprises a collimating lens and a converging lens; the main control and display unit comprises a signal generation module, a microprocessor module and a liquid crystal display module; through high-precision wide-range bias control, single-shot double-receiving full-dimension optical path calibration, dynamic hysteresis adjustment, hierarchical anti-interference and full-temperature compensation, the problems of low bias precision, poor optical path consistency, easy signal oscillation, large temperature drift and weak anti-interference of a traditional system are effectively solved; the application has high distance measurement precision, strong dynamic stability, outstanding anti-interference capability, good full-temperature adaptability, high reliability, and is modularized in structure and easy to integrate, and can meet the requirements of industrial high-precision distance measurement in a complex environment.

Description

Technical Field

[0001] This invention relates to the field of photoelectric ranging technology, specifically to an anti-interference and dynamically adjustable laser ranging system. Background Technology

[0002] Laser ranging technology, with its advantages of being non-contact, highly accurate, and fast-responding, has been widely applied in fields such as power line inspection, water conservancy monitoring, building construction, coal mining, railway maintenance, and geographic surveying. Among them, phase-matrix laser ranging indirectly calculates distance by measuring the phase difference between the transmitted and received signals. It has a significant accuracy advantage in short-range ranging scenarios and occupies a mainstream position in the market.

[0003] However, the reliability and measurement accuracy of existing laser ranging systems still need improvement in complex outdoor, wide temperature range, and strong interference environments, mainly in the following ways: Firstly, the APD bias control has low precision and narrow adjustable range: the external optical path mostly uses APD avalanche diodes as the core of photoelectric detection, and its reverse bias directly determines the avalanche multiplication gain; traditional solutions mostly use fixed bias or discrete component coarse adjustment mode, which makes it difficult to achieve wide-range continuous adjustment, and there is no current closed-loop monitoring mechanism, so the gain is easy to drift with the operating current, resulting in insufficient signal-to-noise ratio of weak echo at long distance and easy saturation distortion of strong echo at close distance, thus limiting the ranging range.

[0004] Secondly, the consistency and benchmark of optical paths need to be improved: the single-transmitter single-receiver architecture relies on mechanical toggle switches to switch between internal and external optical paths, which has problems such as mechanical wear and switching delay; some single-transmitter dual-receiver schemes have not carried out multi-point time difference, amplitude consistency and full-temperature drift calibration, resulting in large differences in delay and gain between internal and external optical paths, and significant accumulation of system errors.

[0005] Third, the dynamic adjustment stability is insufficient: If a conventional automatic gain control circuit does not have hysteresis control logic, small signal fluctuations may trigger frequent gain adjustments, leading to signal oscillation; it lacks a graded step size and adjustment locking mechanism, making it difficult to take into account both strong and weak echo scenarios.

[0006] Fourth, temperature drift has a significant impact: the breakdown voltage of the APD avalanche diode has a significant temperature coefficient, and the gain drift is severe in high and low temperature environments under fixed bias mode, which increases the ranging error; most existing compensation schemes are single-point room temperature calibration, and the adaptability over a wide temperature range needs to be improved.

[0007] Fifth, the anti-interference strategy is relatively simple: outdoor scenes are easily affected by interference from lasers of the same frequency, electromagnetic interference and background light noise. Existing technologies lack graded anti-interference strategies, and accuracy may decrease or work abnormally under interference environments.

[0008] Therefore, there is an urgent need for a laser ranging system that integrates high-precision bias control, full-dimensional optical path calibration, dynamic hysteresis adjustment, full-temperature gain compensation, and graded anti-interference mechanisms to improve the overall performance of the system. Summary of the Invention

[0009] To address the problems in the prior art, the present invention provides an anti-interference and dynamically adjustable laser ranging system.

[0010] The technical solution adopted by this invention to solve its technical problem is: an anti-interference and dynamically adjustable laser ranging system, comprising an optical structure unit, a main control and display unit, a laser modulation and emission unit, a laser receiving and conditioning unit, and an APD avalanche diode module. The optical structure unit includes a collimating lens and a converging lens; The main control and display unit includes a signal generation module, a microprocessor module, and a liquid crystal display module; The laser modulation and emission unit includes a laser modulation module and a laser emission circuit; The laser receiving and conditioning unit includes a photodetector, a photodetector, a preamplifier circuit, an automatic gain control circuit, a post-amplifier circuit, a mixer filter circuit, a phase-shifting amplifier circuit, and a waveform conversion circuit. The APD avalanche diode module includes a high voltage generation circuit, a bias control circuit, and a temperature compensation circuit. The collimating lens is connected to a laser emitting circuit at its rear end and emits laser light at its front end. The rear end of the converging lens is connected to a photodetector and a photodetector, respectively. The laser modulation module has its input end connected to the signal generation module, its power supply end connected to the laser emission circuit, and its output end connected to the collimating lens. The control terminal of the laser emitting circuit is connected to the microprocessor module; The control terminal of the signal generation module is connected to the microprocessor module, and the output terminal is connected to the laser modulation module and the mixing and filtering circuit, respectively. The output terminal of the microprocessor module is connected to the signal generation module, the liquid crystal display module, the automatic gain control circuit, and the bias control circuit, while the input terminal is connected to the waveform conversion circuit, the bias control circuit, and the temperature compensation circuit. The output terminals of both the photodetector and the photodetector are connected to a preamplifier circuit. The output of the preamplifier circuit is connected to the automatic gain control circuit. The output of the automatic gain control circuit is connected to the subsequent amplifier circuit; the output of the subsequent amplifier circuit is connected to the mixer filter circuit. The output of the mixing filter circuit is connected to the phase-shifting amplifier circuit. The output terminal of the phase-shifting amplifier circuit is connected to a waveform conversion circuit. The output of the waveform conversion circuit is connected to the microprocessor module. The output terminal of the high voltage generating circuit is connected to the bias control circuit. The output of the bias control circuit is connected to a photodetector, and the monitoring terminal is connected to a microprocessor module. The output of the temperature compensation circuit is connected to the microprocessor module. The system adopts a single-transmitter dual-receiver optical path structure, and achieves high-precision and high-stability ranging through high-precision bias control, single-transmitter dual-receiver optical path calibration, dynamic hysteresis adjustment, graded anti-interference and full-temperature compensation.

[0011] Specifically, the bias control chip is an ADL5317; the ADL5317 is configured with a high-voltage power supply terminal, a digital power supply terminal, a control voltage terminal, and a current monitoring terminal; the high-voltage power supply terminal is connected to a high-voltage power supply and a filter capacitor in parallel, the digital power supply terminal is connected to a low-voltage power supply and configured with a decoupling capacitor; the control voltage terminal inputs an adjustable control voltage, so that the output bias voltage is in a fixed ratio with the control voltage, and the output is continuously adjustable reverse bias voltage over a wide range; the output terminal is connected to the photodetector cathode after being connected in series with a current limiting element and in parallel with a noise reduction element.

[0012] Specifically, the bias control chip has a built-in current mirror unit, and the current monitoring terminal is connected to an external sampling resistor. The working current of the photodetector is mirrored at a fixed ratio and converted into a voltage signal for sampling by the microprocessor module, thereby realizing wide-range current monitoring and closed-loop feedback.

[0013] Specifically, the microprocessor module pre-stores optical path calibration parameters obtained through the following methods: internal optical path reference calibration, external optical path time difference multi-point calibration, signal amplitude consistency calibration, and full-temperature drift calibration; internal optical path reference calibration uses the photodetector as a reference, and takes multiple samples and averages them to obtain the inherent delay of the system; external optical path time difference multi-point calibration synchronously collects internal and external optical path signals at multiple known distance points to establish a time difference compensation relationship; signal amplitude consistency calibration generates a full-range amplitude compensation relationship; full-temperature drift calibration establishes a time difference compensation model and a bias voltage compensation model at multiple typical temperature points.

[0014] Specifically, the dynamic adjustment mechanism sets a target signal level range; when the echo signal strength is lower than the lower limit of the target range and the signal-to-noise ratio is insufficient, the microprocessor module increases the reverse bias voltage of the photodetector by controlling the voltage, and at the same time increases the gain of the automatic gain control circuit; when the echo signal strength is higher than the upper limit of the target range and a saturation trend appears, the reverse bias voltage and the gain of the automatic gain control circuit are reduced simultaneously; the adjustment process introduces hysteresis logic, and the adjustment is only performed when the signal deviates from the target range a predetermined number of times, and a lock-in time is set after each adjustment.

[0015] Specifically, the graded anti-interference mechanism includes suppression of co-frequency / electromagnetic interference and suppression of background light noise; when co-frequency or electromagnetic interference is detected, multiple sampling averaging is enabled and the transmission frequency is switched; when the background light noise exceeds a preset threshold, the reverse bias voltage of the photodetector is reduced and the noise suppression capability of the automatic gain control circuit is improved; the dynamic adjustment process is completed in a short time, adapting to high-frequency pulse transmission scenarios.

[0016] Specifically, the temperature compensation circuit collects the ambient temperature in real time and generates a temperature-bias compensation relationship based on the temperature characteristics of the photodetector. The microprocessor module dynamically corrects the reverse bias based on the temperature-bias compensation relationship to suppress the influence of temperature drift on the gain of the photodetector and achieve stable ranging across the entire temperature range.

[0017] Specifically, the photodetector is a PIN photodiode and the photodetector is an APD avalanche diode; the PIN photodiode is used for internal optical path signal reception and provides a time reference, and the APD avalanche diode is used for external optical path echo signal reception, forming a single-transmitter dual-receiver structure without mechanical switches.

[0018] Specifically, the phase-shifting amplifier circuit is used to compensate for the additional phase difference introduced by the dual signal channels; the mixer filter circuit converts the high-frequency modulated signal into a low-frequency signal; and the waveform conversion circuit converts the analog signal into a digital square wave signal for the microprocessor module to perform phase difference calculation and distance calculation.

[0019] Specifically, the system is adapted to high-frequency pulse transmission frequency, and the optical path calibration, dynamic adjustment and temperature compensation processes work together to cover the entire range of scenarios from strong echoes at close range to weak echoes at long range, and maintain stable ranging accuracy over a wide temperature range.

[0020] The anti-interference and dynamically adjustable laser ranging system described in this invention has the following beneficial effects: 1. High bias control accuracy and wide adjustable range: The ADL5317 dedicated chip is used to realize a wide range of continuously adjustable reverse bias output. Combined with current closed-loop monitoring, it ensures that the APD avalanche diode (9) works in the best multiplication state, with high photoelectric conversion efficiency, effectively improving the signal-to-noise ratio of weak echo signals.

[0021] 2. Good optical path consistency and small system error: Through single-transmitter dual-receiver full-dimensional optical path calibration, the effects of time delay, signal amplitude difference and temperature drift of internal and external optical paths are eliminated. The signal consistency of internal and external optical paths is high, and the ranging error is small in the whole temperature range, which meets the requirements of high-precision ranging.

[0022] 3. Stable and oscillation-free dynamic adjustment: It adopts a graded step size adjustment + hysteresis lock mechanism to effectively avoid signal adjustment oscillation, has a fast response speed, adapts to high frequency pulse transmission frequency, covers all scenarios from strong echo at close range to weak echo at long range, and has strong signal stability.

[0023] 4. Excellent anti-interference capability and wide environmental adaptability: The graded anti-interference mechanism can effectively deal with co-frequency laser interference, electromagnetic interference and background light noise, and can still stably measure distance in complex outdoor environments, greatly improving environmental adaptability.

[0024] 5. Excellent stability and high reliability across the entire temperature range: The full-temperature gain compensation model effectively offsets the effects of temperature drift, ensuring stable performance across a wide temperature range. There is no significant parameter decay during long-term operation, making it suitable for complex industrial application scenarios.

[0025] 6. Modular design, easy integration and maintenance: The system adopts a modular architecture, with each unit having independent functions and a compact structure, which facilitates integration, debugging and maintenance, reduces production costs, and is suitable for large-scale production. Attached Figure Description

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] Figure 1 A system block diagram of an anti-interference and dynamically adjustable laser ranging system provided by the present invention; Figure 2 The diagram shows an APD avalanche diode module of an anti-interference and dynamically adjustable laser ranging system provided by the present invention.

[0028] In the diagram: 1. Collimating lens; 2. Converging lens; 3. Laser modulation module; 4. Laser emitting circuit; 5. Signal generation module; 6. Microprocessor module; 7. Liquid crystal display module; 8. Photodetector; 9. Photodetector; 10. Preamplifier circuit; 11. Automatic gain control circuit; 12. Post-amplifier circuit; 13. Mixer and filter circuit; 14. Phase-shifting amplifier circuit; 15. Waveform conversion circuit; 16. High voltage generation circuit; 17. Bias control circuit; 18. Temperature compensation circuit. Detailed Implementation

[0029] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0030] like Figures 1-2 As shown, the present invention provides the following technical solution: An anti-interference and dynamically adjustable laser ranging system includes an optical structure unit, a main control and display unit, a laser modulation and emission unit, a laser receiving and conditioning unit, and an APD avalanche diode module. The optical structure unit includes a collimating lens 1 and a converging lens 2; The main control and display unit includes a signal generation module 5, a microprocessor module 6, and an LCD display module 7; The laser modulation and emission unit includes a laser modulation module 3 and a laser emission circuit 4; The laser receiving and conditioning unit includes a photodetector 8, a photodetector 9, a preamplifier circuit 10, an automatic gain control circuit 11, a post-amplifier circuit 12, a mixer and filter circuit 13, a phase-shifting amplifier circuit 14, and a waveform conversion circuit 15. The APD avalanche diode module includes a high voltage generation circuit 16, a bias control circuit 17, and a temperature compensation circuit 18. The collimating lens 1 is connected to the laser emitting circuit 4 at its rear end and emits laser light at its front end. The rear end of the converging lens 2 is connected to the photodetector 8 and the photodetector 9, respectively. The input terminal of the laser modulation module 3 is connected to the signal generation module 5, the power supply terminal is connected to the laser emitting circuit 4, and the output terminal is connected to the collimating lens 1. The control terminal of the laser emitting circuit 4 is connected to the microprocessor module 6; The control terminal of the signal generation module 5 is connected to the microprocessor module 6, and the output terminal is connected to the laser modulation module 3 and the mixing and filtering circuit 13, respectively. The output of microprocessor module 6 is connected to signal generation module 5, LCD display module 7, automatic gain control circuit 11, and bias control circuit 17, and the input is connected to waveform conversion circuit 15, bias control circuit 17, and temperature compensation circuit 18. The output terminals of both photodetector 8 and photodetector 9 are connected to the preamplifier circuit 10. The output of the preamplifier circuit 10 is connected to the automatic gain control circuit 11; The output of the automatic gain control circuit 11 is connected to the subsequent amplifier circuit 12; the output of the subsequent amplifier circuit 12 is connected to the mixer filter circuit 13. The output of the mixer filter circuit 13 is connected to the phase shift amplifier circuit 14; The output of phase-shifting amplifier circuit 14 is connected to waveform conversion circuit 15; The output of waveform conversion circuit 15 is connected to microprocessor module 6; The output terminal of the high voltage generating circuit 16 is connected to the bias control circuit 17. The output of the bias control circuit 17 is connected to the photodetector 9, and the monitoring terminal is connected to the microprocessor module 6. The output of temperature compensation circuit 18 is connected to microprocessor module 6; The system adopts a single-transmitter dual-receiver optical path structure, and achieves high-precision and high-stability ranging through high-precision bias control, single-transmitter dual-receiver optical path calibration, dynamic hysteresis adjustment, graded anti-interference and full-temperature compensation.

[0031] The bias control chip is ADL5317. The ADL5317 is configured with a high-voltage power supply terminal, a digital power supply terminal, a control voltage terminal, and a current monitoring terminal. The high-voltage power supply terminal is connected to the high-voltage power supply and a filter capacitor in parallel. The digital power supply terminal is connected to the low-voltage power supply and configured with a decoupling capacitor. The control voltage terminal inputs an adjustable control voltage so that the output bias voltage is in a fixed ratio with the control voltage, and the output is continuously adjustable reverse bias voltage over a wide range. The output terminal is connected to the cathode of the photodetector 9 after being connected in series with a current limiting element and in parallel with a noise reduction element.

[0032] The bias control chip has a built-in current mirror unit, and the current monitoring terminal is connected to an external sampling resistor. The working current of the photodetector 9 is mirrored according to a fixed ratio and converted into a voltage signal for sampling by the microprocessor module 6, so as to realize wide-range current monitoring and closed-loop feedback.

[0033] The microprocessor module 6 pre-stores optical path calibration parameters obtained through the following methods: internal optical path reference calibration, external optical path time difference multi-point calibration, signal amplitude consistency calibration, and full-temperature drift calibration. The internal optical path reference calibration uses the photodetector 8 as a reference and takes multiple samples to average them to obtain the inherent delay of the system. The external optical path time difference multi-point calibration synchronously collects the signals of the internal and external optical paths at multiple known distance points to establish a time difference compensation relationship. The signal amplitude consistency calibration generates a full-range amplitude compensation relationship. The full-temperature drift calibration establishes a time difference compensation model and a bias voltage compensation model at multiple typical temperature points.

[0034] The dynamic adjustment mechanism sets the target signal level range. When the echo signal strength is lower than the lower limit of the target range and the signal-to-noise ratio is insufficient, the microprocessor module 6 increases the reverse bias voltage of the photodetector 9 by controlling the voltage, and at the same time increases the gain of the automatic gain control circuit 11. When the echo signal strength is higher than the upper limit of the target range and a saturation trend appears, the reverse bias voltage and the gain of the automatic gain control circuit 11 are reduced simultaneously. The adjustment process introduces hysteresis logic, and the adjustment is only performed when the signal deviates from the target range for a predetermined number of consecutive times. A lock-in time is set after each adjustment.

[0035] The graded anti-interference mechanism includes suppression of co-frequency / electromagnetic interference and suppression of background light noise; when co-frequency or electromagnetic interference is detected, multiple sampling averaging is enabled and the transmission frequency is switched; when the background light noise exceeds the preset threshold, the reverse bias voltage of the photodetector 9 is reduced and the noise suppression capability of the automatic gain control circuit 11 is improved; the dynamic adjustment process is completed in a short time, adapting to high-frequency pulse transmission scenarios.

[0036] Among them, the temperature compensation circuit 18 collects the ambient temperature in real time and generates a temperature-bias compensation relationship by combining it with the temperature characteristics of the photodetector 9; the microprocessor module 6 dynamically corrects the reverse bias based on the temperature-bias compensation relationship, suppresses the influence of temperature drift on the gain of the photodetector 9, and realizes stable ranging across the entire temperature range.

[0037] Among them, photodetector 8 is a PIN photodiode and photodetector 9 is an APD avalanche diode; the PIN photodiode is used for internal optical path signal reception and provides a time reference, and the APD avalanche diode is used for external optical path echo signal reception, forming a single-transmitter dual-receiver structure without mechanical switches.

[0038] Among them, the phase-shifting amplifier circuit 14 is used to compensate for the additional phase difference introduced by the dual signal channels; the mixer filter circuit 13 converts the high-frequency modulated signal into a low-frequency signal; and the waveform conversion circuit 15 converts the analog signal into a digital square wave signal for the microprocessor module 6 to perform phase difference calculation and distance calculation.

[0039] The system is adapted to high-frequency pulse transmission frequency, and the optical path calibration, dynamic adjustment and temperature compensation processes work together to cover the entire range of scenarios from strong echoes at close range to weak echoes at long range, and maintain stable ranging accuracy over a wide temperature range.

[0040] Example 1: Overall System Setup and Basic Function Verification This embodiment completes the modular construction of the system, optical path calibration, and basic ranging function verification. It focuses on verifying the improved accuracy and stability brought about by the high-precision bias control of ADL5317, single-transmitter dual-receiver optical path calibration, and current closed-loop monitoring.

[0041] 1. Hardware selection and circuit construction Optical structure unit: Collimating lens 1 is a spherical lens with a focal length of 10mm and an aperture of 5mm, which is compatible with a semiconductor laser diode with a wavelength of 905nm; Converging lens 2 is an aspherical lens with a focal length of 25mm and an aperture of 10mm, which improves the convergence efficiency of weak echoes and enhances the echo signal strength.

[0042] Main control and display unit: Microprocessor module 6 uses STM32F407 high-performance microprocessor, with built-in 12-bit ADC and DAC to meet the requirements of signal sampling, control voltage output and data operation; Signal generation module 5 uses AD9833 direct digital frequency synthesizer to generate 10MHz high-frequency sine modulation signal; LCD display module 7 uses 1.3-inch OLED screen to display ranging results, signal strength, operating temperature and system operating status in real time.

[0043] Laser modulation and emission unit: The semiconductor laser diode is a 905nm pulsed laser with a peak power of 75W; the laser modulation module 3 builds a driving circuit to load a 10MHz high-frequency sinusoidal modulation signal onto the laser, so that the emitted laser carries phase information; the laser emission circuit 4 is equipped with a constant current driving chip to control the laser's operating current to be stable at 1.5A, ensuring stable laser emission.

[0044] Laser receiving and conditioning unit: Photodetector 8 is a PIN photodiode with a response wavelength of 800-1100nm and a response time of 1ns, used for internal optical path signal reception; photodetector 9 is a 905nm dedicated APD avalanche diode with a typical breakdown voltage of 120V, used for external optical path echo signal reception; preamplifier circuit 10 is a transimpedance amplifier (TIA) to convert the photoelectric converted current signal into a voltage signal; automatic gain control circuit 11 is a variable gain amplifier with a gain adjustment range of 0-60dB; post-amplifier circuit 12, mixer-filter circuit 13, phase-shifting amplifier circuit 14, and waveform conversion circuit 15 are built according to conventional photoelectric signal processing circuits to complete secondary signal amplification, filtering, phase compensation, and waveform conversion.

[0045] APD avalanche diode module: The high voltage generation circuit 16 uses a DC-DC boost module, with a 12V DC power input and an 80V high voltage output; the bias control circuit 17 uses the ADL5317 dedicated chip, and the peripheral circuits for filtering, current limiting, and current monitoring are designed according to the technical solution; the temperature compensation circuit 18 uses an NTC thermistor to collect the ambient temperature in real time and connect it to the sampling terminal of the microprocessor module 6 ADC.

[0046] 2. System assembly and debugging Optical assembly: The collimating lens 1 is fixed to the front end of the laser with a spacing of 1mm to ensure the collimation effect of the beam; the converging lens 2 is fixed to the front end of the APD avalanche diode with a spacing of 5mm to ensure that the reflected light is focused on the APD photosensitive surface; the internal optical path directly couples the laser and the PIN photodiode 8 through an optical fiber to reduce optical signal loss and ensure the stability of the internal optical path signal.

[0047] Circuit connection and debugging: Connect each unit circuit according to the system architecture, focusing on debugging the ADL5317 circuit: connect the high voltage power supply terminal to 80V high voltage, the digital power supply terminal to 5V power supply, the control voltage terminal to the output terminal of the microprocessor module 6DAC, and the current monitoring terminal to the sampling terminal of the microprocessor module 6ADC after connecting a 10kΩ precision resistor; debug the filter circuit to ensure that the power supply ripple is ≤10mV; calibrate the current monitoring circuit to ensure that the sampling error is ≤2%.

[0048] Firmware initialization: The microprocessor module 6 writes the initialization program, configures the initial bias voltage of ADL5317 to 40V, the initial gain of the automatic gain control circuit 11 to 20dB, and sets the target signal level range to 100mV-1V; writes the basic parameters for optical path calibration, and prepares to enter the calibration process.

[0049] 3. Implementation of Single-Transmitter Dual-Receiver Optical Path Calibration Internal optical path PIN reference calibration: With the external optical path signal reception turned off, the system emits 100 single-pulse lasers, and the emission time of each pulse and the signal reception time of the PIN photodiode 8 are recorded synchronously to calculate the inherent delay of the internal optical path; the average value of the 100 measurement results is taken to obtain the inherent delay of the system as 2.4ns, which is written into the firmware as a time reference. The measurement error is 0.08ns, which meets the accuracy requirement of ≤±0.1ns.

[0050] Multi-point calibration of time difference in external optical path: The standard corner cube prism reflector target is fixed at known distances of 1m, 10m, 20m, 50m, and 100m in sequence. The signals of the PIN photodiode 8 in the internal optical path and the echo signals of the APD avalanche diode in the external optical path are collected simultaneously. The theoretical flight time and the actual flight time of the external optical path are calculated to obtain the time difference. A compensation curve for the time difference as a function of distance is established by fitting multiple sets of data and written into the system firmware. After calibration, the time difference error at a distance of 50m is reduced from 1.2ns before calibration to 0.15ns, effectively eliminating the system delay error.

[0051] Signal amplitude consistency calibration: At each calibration distance point from 1m to 100m, the signal amplitudes of PIN photodiode 8 and APD avalanche diode are synchronously acquired, and the amplitude compensation coefficients at different distances are calculated. A full-range amplitude compensation table is generated through polynomial fitting and written into the firmware. After compensation, the amplitude consistency error between the APD avalanche diode signal and the PIN photodiode 8 signal is ≤4.2%, which meets the accuracy requirement of ≤±5%.

[0052] Temperature drift calibration and modeling: The above calibration process was repeated at typical temperature points such as −20℃, 0℃, 25℃, 40℃, and 60℃, and the time difference and amplitude compensation coefficient at different temperatures were recorded; a linear compensation model for time difference and a temperature-bias compensation curve were established and written into the firmware of microprocessor module 6; under the high temperature environment of 60℃, the ranging error after temperature compensation was reduced from 8cm to 2.8cm, effectively suppressing the influence of temperature drift.

[0053] 4. Basic performance testing of this invention Test conditions: ambient temperature 25℃, standard atmospheric environment, no strong interference; test distances are standard distance points of 5m, 20m, 50m, 80m, and 100m.

[0054] Distance measurement accuracy: ±1.2cm at 5m, ±1.8cm at 20m, ±2.5cm at 50m, ±3.0cm at 80m, and ±3.8cm at 100m, meeting the accuracy requirement that the error range does not exceed ±3cm within a measurement distance of 50m.

[0055] Signal stability: In a close-range 5m strong echo scenario, the APD avalanche diode signal amplitude is stable at 800mV-950mV with no saturation distortion; in a long-range 100m weak echo scenario, the signal amplitude is stable at 150mV-250mV with a signal-to-noise ratio of ≥12dB and no noise overload.

[0056] Bias control accuracy: The microprocessor module 6DAC outputs control voltage, and the ADL5317 outputs reverse bias voltage with a range of 6V-75V and an output accuracy of ≤±0.4%, meeting the requirements for high-precision control.

[0057] Compare with Example 1, Traditional Fixed Bias + Single Transmitter / Single Receiver System Structural differences: The APD avalanche diode uses a fixed 40V reverse bias, which is not adjustable; it only retains the external optical path APD avalanche diode receiving channel, and there is no internal optical path PIN photodiode 8 reference. The optical path is switched by a mechanical toggle switch; there is no multi-point time difference, amplitude consistency and full-temperature drift calibration process; there is no current closed-loop monitoring mechanism and dynamic gain adjustment algorithm.

[0058] Results of the same test conditions: Distance measurement accuracy: ±4.5cm at 5m, ±6.2cm at 20m, ±8.5cm at 50m, ±12.1cm at 80m, and ±15.2cm at 100m, which is far lower than that of this invention.

[0059] Signal stability: In close-range strong echo scenarios, the signal is prone to saturation clipping, with amplitude fluctuations ≥ ±15%; in long-range weak echo scenarios, the signal-to-noise ratio is <8dB, the probability of noise overload is high, and stable ranging cannot be achieved.

[0060] Optical path consistency: There is no internal optical path reference and calibration process, the delay error of the internal and external optical path systems is >2ns, the signal amplitude deviation is >20%, and the optical path consistency is extremely poor.

[0061] Compare with Example 2: Fixed bias + single transmitter / dual receiver, no calibration system Structural differences: The APD avalanche diode uses a fixed 40V reverse bias, which is not adjustable; it adopts a single-transmitter dual-receiver structure, including an internal optical path PIN photodiode 8 and an external optical path APD avalanche diode; however, it has not carried out multi-point time difference, amplitude consistency and full-temperature drift calibration processes; and it lacks a current closed-loop monitoring mechanism.

[0062] Results of the same test conditions: Distance measurement accuracy: ±3.2cm at 5m, ±4.5cm at 20m, ±6.8cm at 50m, ±9.5cm at 80m, and ±12.3cm at 100m. The accuracy is still far lower than that of this invention.

[0063] Optical path consistency: time delay difference between internal and external optical paths >1ns, signal amplitude deviation >15%; ranging error >7cm under high and low temperature environments, with significant impact from temperature drift.

[0064] Compare with Example 3, Discrete Component Bias + Single Transmitter Dual Receiver, Single-Point Calibration System Structural differences: The APD avalanche diode bias circuit is built with discrete components, which only supports 10V step coarse adjustment and cannot be continuously adjusted; it adopts a single-transmitter dual-receiver structure; single-point optical path calibration is only carried out at room temperature of 25℃, without multi-point calibration and full-temperature drift calibration; there is no current closed-loop monitoring mechanism.

[0065] Results of the same test conditions: Distance measurement accuracy: ±2.8cm at 5m, ±3.9cm at 20m, ±5.5cm at 50m, ±7.8cm at 80m, and ±10.2cm at 100m. The accuracy is lower than that of this invention.

[0066] Bias control accuracy: Bias output error >3%, unable to accurately match the optimal gain of the APD avalanche diode; ranging error >6cm under high and low temperature environments, resulting in severe gain drift; insufficient gain and low signal-to-noise ratio in long-distance weak echo scenarios.

[0067] Comparative conclusions: This invention, through high-precision wide-range bias control using the ADL5317, single-transmitter dual-receiver full-dimensional optical path calibration, and current closed-loop monitoring, reduces the ranging error at a distance of 50m from 8.5cm to 2.5cm in the traditional fixed bias + single-transmitter single-receiver system, significantly improving signal stability and optical path consistency. The three control examples respectively exposed the underlying technical defects of lacking precise bias control, full-dimensional optical path calibration, and bias control chip. Their ranging accuracy, signal stability, and optical path consistency were progressively inferior to this invention, fully verifying the innovation and necessity of the core technical solution of this invention.

[0068] Example 2: Dynamic Adjustment and Anti-interference Performance Optimization Based on Example 1, this embodiment optimizes the dynamic hysteresis adjustment algorithm parameters and hierarchical anti-interference strategy to further improve the system response speed, anti-oscillation capability, and robustness in complex environments.

[0069] 1. Dynamic adjustment of algorithm parameters optimization Target level range optimization: The target signal level range is optimized from 100mV-1V to 150mV-900mV, taking into account both the signal-to-noise ratio of weak echo signals and the saturation margin of strong echo signals, thereby reducing the probability of signal distortion.

[0070] Optimized step size adjustment: In scenarios with weak echoes at long distances and insufficient signal-to-noise ratio, the reverse bias voltage boost step size of the APD avalanche diode is optimized to 0.3V-0.5V to avoid signal overshoot; the single gain boost step size of the automatic gain control circuit 11 is optimized to 4dB-6dB to accelerate the boosting speed of weak signals; In scenarios with strong echoes at close distances and signal saturation, the reverse bias voltage down step size is optimized to 0.5V-0.8V to quickly exit the saturation state, and the single gain down step size of the automatic gain control circuit 11 is optimized to 5dB-8dB to prevent signal overshoot.

[0071] Hysteresis control parameters optimization: The number of times the signal deviates from the target range is determined is reduced from 3 consecutive times to 2 consecutive times, shortening the adjustment response time; the lock-in time after a single adjustment is reduced from 10μs to 8μs, improving the adaptability of the adjustment frequency and meeting the requirements of high-frequency pulse transmission.

[0072] Linkage compensation optimization: Strengthen the linkage mechanism between the dynamic adjustment algorithm and the single-transmitter dual-receiver optical path calibration amplitude compensation table. Based on the current ranging distance, accurately query the corresponding amplitude compensation coefficient and pre-compensate the gain of the automatic gain control circuit 11 to reduce the number of adjustments and improve the response speed.

[0073] 2. Optimization of hierarchical anti-interference enhancement mode Co-frequency / electromagnetic interference suppression optimization: When signal glitches caused by co-frequency laser or electromagnetic interference are detected, a 10-sample averaging algorithm is enabled to further suppress signal glitches; two sets of backup transmission frequencies are configured, and the switching is fast after interference is detected, with a switching response time of ≤5μs, improving interference avoidance capability; a signal spectrum analysis module is added to identify electromagnetic interference frequency components and enable digital filtering algorithms to filter out interference frequency bands.

[0074] Background light noise suppression optimization: The background light noise trigger threshold is optimized from 100nA to 80nA, allowing for earlier intervention in the noise suppression process; during noise suppression, while reducing the reverse bias voltage of the APD avalanche diode 9, the noise suppression ratio of the automatic gain control circuit 11 is increased by 20%, enhancing the noise filtering effect.

[0075] Interference graded response optimization: Establish an interference graded response mechanism. For mild interference, only filtering and sampling averaging are used; for moderate interference, the bias voltage is reduced and the transmission frequency is switched simultaneously; for severe interference, the laser emission power is reduced for a short time and multiple cumulative decisions are made to ensure accurate detection of effective echo signals.

[0076] 3. Optimized overall performance test Test conditions: ambient temperature 25℃, complex scenarios including strong background light, co-frequency laser interference, and electromagnetic interference; test distances are 1m, 10m, 50m, and 100m.

[0077] Dynamic adjustment response speed: The completion time of the dynamic closed-loop adjustment process has been optimized from 100μs to 75μs, which can be adapted to a 15kHz pulse transmission frequency, and the ranging refresh rate has been improved by 50%.

[0078] All-scenario signal stability: In close-range 1m-10m strong echo scenarios: the signal amplitude is stable at 700mV-900mV, with no clipping distortion, and the adjustment response time is ≤20μs; In a medium-range (10m-50m) normal echo scenario: the signal amplitude is stable between 300mV and 700mV, with fluctuations ≤ ±5%; In long-distance 50m-100m weak echo scenarios: the signal amplitude is stable at 150mV-300mV, the signal-to-noise ratio is stable at ≥12dB, and there is no noise submersion phenomenon.

[0079] Anti-interference performance in complex environments: In environments with interference from lasers of the same frequency: signal glitch elimination rate ≥95%, ranging error ≤±3.5cm; In environments with strong background light and noise of 150nA: effective echo signal recognition rate ≥98%, ranging error ≤±3.8cm; Electromagnetic interference environment: Signal-to-noise ratio improved by 15%, ranging error ≤ ±3.2cm.

[0080] Compare with Example 1: ADL5317 bias + simple AGC, hysteresis-free system Structural differences: It adopts the ADL5317 high-precision bias control circuit, which supports wide-range continuously adjustable reverse bias; it is equipped with a basic automatic gain control circuit 11; however, it lacks hysteresis control logic, graded adjustment step size, and adjustment locking mechanism; and it is not linked with the single-transmitter dual-receiver optical path calibration amplitude compensation table.

[0081] Results of the same test conditions: Dynamic adjustment stability: Small signal fluctuations trigger frequent gain adjustments, resulting in obvious signal oscillations with amplitude fluctuations ≥ ±12%; there is no lock-in mechanism after a single adjustment, the stabilization time is >200μs, and it only supports a maximum pulse transmission frequency of 5kHz, resulting in poor adaptability.

[0082] Ranging accuracy: ±5.2cm at 50m and ±9.8cm at 100m; insufficient gain and low signal-to-noise ratio in long-distance weak echo scenarios; prone to overshoot and signal distortion in short-distance strong echo scenarios.

[0083] Compare with Example 2, ADL5317 bias + AGC, system without anti-interference strategy. Structural differences: Employs the ADL5317 high-precision bias control circuit and optimized dynamic hysteresis adjustment algorithm; however, it lacks a graded anti-interference mechanism, multiple sampling averaging, and transmit frequency switching function; only a basic filter circuit is configured. Test results under the same conditions: Anti-interference performance: Under the same frequency laser interference environment, the ranging error is ±6.5cm; under the strong background light noise of 150nA, the effective echo signal recognition rate is only 88%; under the electromagnetic interference environment, the signal-to-noise ratio drops significantly, the ranging error is >5cm, and the robustness is poor.

[0084] Comparative conclusions: This invention achieves rapid, stable, and oscillation-free closed-loop regulation through graded adjustment step size, hysteresis locking mechanism, graded anti-interference strategy, and linkage amplitude compensation, maintaining high-precision ranging even in complex interference environments. Comparative Example 1 reveals the defects of signal oscillation and slow response speed caused by hysteresis-free control, while Comparative Example 2 reveals the defect of poor robustness without graded anti-interference strategy. Both the dynamic adjustment performance and anti-interference capability are significantly weaker than those of this invention, fully verifying the advanced nature of the optimized technical solution.

[0085] Example 3: Verification of adaptability and long-term reliability in all-temperature environments Based on Example 2, this embodiment conducts full-temperature environment adaptability tests and long-term stability tests to verify the system's temperature compensation effect and industrial-grade reliability.

[0086] 1. Full-temperature environment adaptability test Test conditions: Temperature range: −20℃ to 60℃, with 10℃ intervals; ambient humidity: 50%; test distances: 5m, 20m, 50m, and 80m.

[0087] Test results: -20℃ low temperature environment: ranging error ≤ ±3.2cm, signal amplitude fluctuation ≤ ±6%, ADL5317 output reverse bias voltage stabilized at 38V-42V; At 25℃ ambient temperature: ranging error ≤ ±2.5cm, signal amplitude fluctuation ≤ ±4%, the overall system performance is optimal; In a high-temperature environment of 60℃: ranging error ≤ ±3.0cm, signal amplitude fluctuation ≤ ±5%, and significant temperature compensation effect.

[0088] Conclusion: The system's ranging accuracy and signal stability meet the design requirements under full temperature conditions. The temperature compensation technology effectively suppresses the impact of temperature drift on the gain of the APD avalanche diode 9, and it has strong adaptability over a wide temperature range.

[0089] 2. Long-term stability test Test conditions: ambient temperature 25℃, standard atmospheric environment, continuous system operation for 1000 hours, test interval of 100 hours, test distance fixed at 50m; monitoring indicators include ranging error, signal strength, and ADL5317 output bias voltage.

[0090] Test results: Ranging error: stable within ±2.3cm~±2.8cm, with no obvious drift; Signal strength: stable within the range of 400mV-500mV, with fluctuation range ≤±3%; APD reverse bias: stable within the range of 40V±0.2V, with no reduction in control accuracy.

[0091] Conclusion: The system exhibits good long-term stability, with no significant degradation in core parameters, high reliability, and is suitable for industrial-grade long-term continuous operation scenarios.

[0092] Compared to Example 1, the complete architecture with single-point 25°C calibration and no full-temperature compensation system. Structural differences: It includes ADL5317 high-precision bias control, single-transmitter dual-receiver optical path calibration, dynamic hysteresis adjustment, and graded anti-interference mechanism; however, it only performs single-point optical path calibration at room temperature of 25℃, and has not established a full-temperature time difference compensation model and temperature-bias compensation curve, and has no full-temperature compensation function.

[0093] Results of the same test conditions: Full-temperature ranging accuracy: At a normal temperature of 25℃, the ranging error at a distance of 50m is ±2.8cm; at a low temperature of −20℃, the ranging error is ±6.5cm; at a high temperature of 60℃, the ranging error is ±7.2cm; the error increases sharply under high and low temperature conditions, and the effect of temperature drift is significant.

[0094] Signal stability: Signal amplitude fluctuation is ≥±8% under high and low temperature environments, APD avalanche diode 9 gain drift is severe, signal-to-noise ratio is low in weak echo scenarios, and distortion is easy in strong echo scenarios.

[0095] Comparative conclusions: The full-temperature compensation model of this invention effectively offsets the influence of temperature drift on the gain of the APD avalanche diode 9, and the ranging accuracy is stable and the signal fluctuation is small in a wide temperature range of −20℃ to 60℃. The performance of the control example 3-1 is close to that of this invention under normal temperature conditions, but the ranging error increases sharply and the signal stability decreases significantly under high and low temperature conditions. This fully verifies the necessity and core value of the full-temperature compensation mechanism. The industrial-grade reliability of this invention is significantly better than that of the existing technical solutions.

[0096] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. An anti-interference, dynamically adjustable laser ranging system, comprising an optical structure unit, a main control and display unit, a laser modulation and emission unit, a laser receiving and conditioning unit, and an APD avalanche diode module, characterized in that, The optical structure unit includes a collimating lens (1) and a converging lens (2); The main control and display unit includes a signal generation module (5), a microprocessor module (6), and a liquid crystal display module (7). The laser modulation and emission unit includes a laser modulation module (3) and a laser emission circuit (4). The laser receiving and conditioning unit includes a photodetector (8), a photodetector (9), a preamplifier circuit (10), an automatic gain control circuit (11), a post-amplifier circuit (12), a mixer filter circuit (13), a phase-shifting amplifier circuit (14), and a waveform conversion circuit (15). The APD avalanche diode module includes a high voltage generation circuit (16), a bias control circuit (17), and a temperature compensation circuit (18). The collimating lens (1) is connected to the laser emitting circuit (4) at the rear end and emits laser light at the front end; The converging lens (2) is connected to the photodetector (8) and the photodetector (9) at its rear end. The laser modulation module (3) has its input end connected to the signal generation module (5), its power supply end connected to the laser emitting circuit (4), and its output end connected to the collimating lens (1). The control terminal of the laser emitting circuit (4) is connected to the microprocessor module (6). The signal generation module (5) has its control terminal connected to the microprocessor module (6) and its output terminal connected to the laser modulation module (3) and the mixing and filtering circuit (13), respectively. The output terminal of the microprocessor module (6) is connected to the signal generation module (5), the liquid crystal display module (7), the automatic gain control circuit (11), and the bias control circuit (17), and the input terminal is connected to the waveform conversion circuit (15), the bias control circuit (17), and the temperature compensation circuit (18). The output terminals of the photodetector (8) and the photodetector (9) are both connected to the preamplifier circuit (10). The output of the preamplifier circuit (10) is connected to the automatic gain control circuit (11). The output of the automatic gain control circuit (11) is connected to the subsequent amplifier circuit (12); the output of the subsequent amplifier circuit (12) is connected to the mixer filter circuit (13). The output of the mixing filter circuit (13) is connected to the phase shift amplifier circuit (14). The output of the phase-shifting amplifier circuit (14) is connected to the waveform conversion circuit (15). The output of the waveform conversion circuit (15) is connected to the microprocessor module (6). The output terminal of the high voltage generating circuit (16) is connected to the bias control circuit (17). The output of the bias control circuit (17) is connected to the photodetector (9), and the monitoring end is connected to the microprocessor module (6). The output of the temperature compensation circuit (18) is connected to the microprocessor module (6). The system adopts a single-transmitter dual-receiver optical path structure, and achieves high-precision and high-stability ranging through high-precision bias control, single-transmitter dual-receiver optical path calibration, dynamic hysteresis adjustment, graded anti-interference and full-temperature compensation.

2. The anti-interference and dynamically adjustable laser ranging system according to claim 1, characterized in that: The bias control chip is ADL5317; ADL5317 is configured with a high-voltage power supply terminal, a digital power supply terminal, a control voltage terminal and a current monitoring terminal; the high-voltage power supply terminal is connected to the high-voltage power supply and a filter capacitor in parallel, the digital power supply terminal is connected to the low-voltage power supply and configured with a decoupling capacitor; the control voltage terminal inputs an adjustable control voltage so that the output bias voltage is in a fixed ratio with the control voltage, and the output is a wide-range continuously adjustable reverse bias voltage; the output terminal is connected in series with a current limiting element and in parallel with a noise reduction element and then connected to the cathode of the photodetector (9).

3. The anti-interference and dynamically adjustable laser ranging system according to claim 1, characterized in that: The bias control chip has a built-in current mirror unit and an external sampling resistor connected to the current monitoring terminal. The working current of the photodetector (9) is mirrored in a fixed ratio and converted into a voltage signal for sampling by the microprocessor module (6), thereby realizing wide-range current monitoring and closed-loop feedback.

4. The anti-interference and dynamically adjustable laser ranging system according to claim 1, characterized in that: The microprocessor module (6) has pre-stored optical path calibration parameters obtained in the following ways: internal optical path reference calibration, external optical path time difference multi-point calibration, signal amplitude consistency calibration and full-temperature drift calibration; The internal optical path reference calibration uses the photodetector (8) as the reference and takes the average of multiple samples to obtain the inherent delay of the system; the external optical path time difference multi-point calibration collects the signals of the internal and external optical paths at multiple known distance points simultaneously to establish the time difference compensation relationship; the signal amplitude consistency calibration generates the full range amplitude compensation relationship; the full temperature drift calibration establishes the time difference compensation model and the bias voltage compensation model at multiple typical temperature points.

5. The anti-interference and dynamically adjustable laser ranging system according to claim 1, characterized in that: The dynamic adjustment mechanism sets the target signal level range; when the echo signal strength is lower than the lower limit of the target range and the signal-to-noise ratio is insufficient, the microprocessor module (6) increases the reverse bias of the photodetector (9) by controlling the voltage, and at the same time increases the gain of the automatic gain control circuit (11); when the echo signal strength is higher than the upper limit of the target range and a saturation trend appears, the reverse bias and the gain of the automatic gain control circuit (11) are reduced at the same time; the adjustment process introduces hysteresis logic, and the adjustment is only performed when the signal deviates from the target range for a predetermined number of consecutive times, and a lock-in time is set after each adjustment.

6. The anti-interference and dynamically adjustable laser ranging system according to claim 1, characterized in that: The graded anti-interference mechanism includes suppression of co-frequency / electromagnetic interference and suppression of background light noise; when co-frequency or electromagnetic interference is detected, multiple sampling averaging is enabled and the transmission frequency is switched; when the background light noise exceeds the preset threshold, the reverse bias voltage of the photodetector (9) is reduced and the noise suppression capability of the automatic gain control circuit (11) is improved; the dynamic adjustment process is completed in a short time, adapting to high-frequency pulse transmission scenarios.

7. The anti-interference and dynamically adjustable laser ranging system according to claim 1, characterized in that: The temperature compensation circuit (18) collects the ambient temperature in real time and generates a temperature-bias compensation relationship by combining the temperature characteristics of the photodetector (9). The microprocessor module (6) dynamically corrects the reverse bias based on the temperature-bias compensation relationship, suppresses the influence of temperature drift on the gain of the photodetector (9), and realizes stable ranging across the entire temperature range.

8. The anti-interference and dynamically adjustable laser ranging system according to claim 1, characterized in that: The photodetector (8) is a PIN photodiode, and the photodetector (9) is an APD avalanche diode; the PIN photodiode is used for internal optical path signal reception and provides a time reference, and the APD avalanche diode is used for external optical path echo signal reception, forming a single-transmitter dual-receiver structure without mechanical switches.

9. The anti-interference and dynamically adjustable laser ranging system according to claim 1, characterized in that: The phase-shifting amplifier circuit (14) is used to compensate for the additional phase difference introduced by the dual signal channels; the mixing filter circuit (13) converts the high-frequency modulation signal into a low-frequency signal; the waveform conversion circuit (15) converts the analog signal into a digital square wave signal for the microprocessor module (6) to perform phase difference calculation and distance calculation.

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