A TOF-based laser ranging system

Abstract

The application discloses a kind of laser ranging systems based on TOF, it is related to laser ranging field.System includes data processing module, laser emission module, light splitting piece, reflector, reference receiving module and main receiving module;Laser emission module emits pulse measurement laser, after light splitting piece, it is divided into the main measurement laser of target measured for being shot, and reference measurement laser is shot to reflector;Main receiving module is used to receive the main measurement laser of target return, reference receiving module is used to receive the reference measurement laser reflected by reflector, both generate main, reference pulse induction signal respectively, and the circuit of two receiving modules is same or symmetrical;Data processing module is used to determine the time difference between two according to the time stamp information of main, reference pulse induction signal as initial differential flight time, and based on the initial differential flight time and speed of light, the ranging result of measured target is obtained by calculation.The application can effectively improve the accuracy and reliability of TOF ranging.

Description

Technical Field

[0001] This invention relates to the field of laser ranging technology, and more particularly to a time-of-flight (TOF) based laser ranging system. Background Technology

[0002] Time-of-Flight (TOF) laser ranging technology has been widely used in industrial automation, robot navigation, and level measurement due to its advantages such as simple structure, fast response speed, and relatively low cost. Its basic principle is to calculate the target distance by measuring the round-trip time of a laser pulse from emission to reflection back to the receiver, and then combining this with the speed of light.

[0003] In practical applications, the accuracy and stability of Time-of-Flight (TOF) ranging systems are affected by a variety of factors. One key technical challenge lies in the consistency of the delay times of the internal electronic components. Traditional TOF ranging systems typically employ a single-path receiver structure, where the emitted laser pulse is received and processed by a single photodetector (such as an avalanche photodiode, APD) and subsequent signal processing circuitry. This signal processing chain includes multiple stages such as photoelectric conversion, signal amplification, waveform shaping, and time discrimination.

[0004] However, the performance parameters of the electronic components that make up these circuits (such as APDs, operational amplifiers, high-speed comparators, etc.), such as gain, response time, and trigger threshold, are highly sensitive to the operating environment. In particular, fluctuations in ambient temperature and slight changes in supply voltage can cause the characteristics of these components to drift, resulting in small, unpredictable changes in the delay time of the entire signal processing chain. For example, an increase in temperature may lead to an increase in amplifier delay or a change in the comparator's switching threshold voltage, both of which will cause the final measured time of flight to include an error term that varies with the environment.

[0005] This internal delay drift caused by environmental factors directly manifests as jitter and zero-point drift in the ranging results, which seriously affects the accuracy and reliability of the measurement. Summary of the Invention

[0006] In view of the above-mentioned technical problems and defects, the purpose of this invention is to provide a time-of-flight (TOF) based laser ranging system that can effectively improve the accuracy and reliability of TOF ranging.

[0007] To achieve the above objectives, this invention provides a Time-of-Flight (TOF) based laser ranging system, comprising a data processing module, a laser emitting module, a beam splitter, a reflector, a reference receiving module, and a main receiving module. The laser emitting module emits a pulsed measurement laser. The beam splitter is positioned in the emission direction of the laser emitting module to split the pulsed measurement laser into a reference measurement laser and a main measurement laser. The reference measurement laser is directed towards the reflector, and the main measurement laser is directed towards the target being measured. The reflector reflects the reference measurement laser to the reference receiving module. The reference receiving module receives the reference measurement laser and generates a reference pulse sensing signal. The main receiving module receives the main measurement laser reflected back from the target being measured and generates a main pulse sensing signal. The circuitry of the main receiving module and the reference receiving module is identical or symmetrical. The data processing module is connected to both the reference receiving module and the main receiving module and is used to: determine the initial differential time of flight based on the timestamp information of the main pulse sensing signal and the reference pulse sensing signal; and calculate the ranging result of the target being measured based on the initial differential time of flight and the speed of light.

[0008] The system described in this invention effectively improves the accuracy and reliability of Time-of-Flight (TOF) ranging through its unique dual-path differential receiver architecture. This invention cleverly adds a reference receiver module that is "identical" or "symmetrical" to the main receiver module circuit, and constructs an internal reference optical path with a fixed optical path. When environmental factors such as temperature and voltage change, the signal processing delay drift caused to the main and reference receiver links is "common-mode," meaning that the two links will experience delay changes of the same magnitude and in the same direction. The data processing module calculates the timestamp difference between the main and reference pulse sensing signals (i.e., the initial differential time of flight). During this differential operation, the "common-mode" delay drift added to the two links due to environmental changes is precisely canceled out. This "differential offsetting" design ensures that the measurement results are no longer affected by the performance drift of electronic components, greatly improving the ranging system's resistance to environmental interference and long-term stability, laying a solid foundation for achieving high-precision ranging.

[0009] Optionally, in some embodiments, the data processing module is further specifically used to: determine the walking error parameter based on the pulse width of the main pulse sensing signal; generate a calibration flight time based on the initial differential flight time and the walking error parameter; and calculate the calibrated ranging result of the target based on the calibration flight time and the speed of light.

[0010] The technical solution adopted in the above embodiments significantly improves the measurement accuracy of the system by introducing a walking error calibration mechanism. It solves the measurement error problem introduced by signal amplitude variations due to differences in target reflectivity, which was not covered by the first-layer "differential offsetting" concept. The data processing module quantifies and compensates for walking errors by analyzing the pulse width of the main pulse signal—a feature that directly reflects the strength of the echo energy—enabling the system to output corrected, high-precision ranging results when facing targets of different materials, colors, and distances. This secondary calibration ensures that the system maintains high stability while further achieving high accuracy, a key step in achieving millimeter-level precision.

[0011] Optionally, in some embodiments, the data processing module is further specifically used to: calculate the pulse width ratio of the main pulse sensing signal to the reference pulse sensing signal or the pulse measurement laser; and determine the walking error parameter corresponding to the pulse width ratio based on a preset walking error correspondence relationship.

[0012] By adopting the technical solution of the above embodiments, a more robust method for determining walking error parameters is proposed, further enhancing the reliability of calibration. Instead of using the absolute pulse width of the main pulse, the method calculates the "pulse width ratio" between the main pulse and the reference pulse (or transmitted pulse), effectively resisting pulse width drift caused by overall system conditions (such as temperature changes). This relative measurement method isolates changes purely caused by differences in target reflectivity, making the determination of walking error parameters more accurate and stable. It utilizes existing reference signals in the system as a dynamic benchmark, establishing a more reliable walking error correspondence in the form of a "ratio" that is insensitive to environmental changes, thus improving the overall performance of the system under complex operating conditions.

[0013] Optionally, in some embodiments, the timestamp information of the main pulse sensing signal includes the rising edge time of the main pulse, and the timestamp information of the reference pulse sensing signal includes the rising edge time of the reference pulse; the data processing module is specifically used to calculate the time difference between the rising edge time of the main pulse and the rising edge time of the reference pulse to obtain the initial differential flight time.

[0014] The technical solution described in the above embodiments clarifies the specific calculation method for the initial differential flight time. By locking the rising edge of the pulse signal as a unified timing reference point, the stability and consistency of time measurement are ensured. The rising edge is the starting marker of the pulse signal; its position is relatively stable and not easily affected by subsequent waveform changes such as pulse broadening. By accurately calculating the time difference between the rising edges of the main and reference signals, a clean initial flight time value with low jitter can be obtained. This method is simple and efficient in hardware implementation, providing a high-quality raw data foundation for all subsequent calibration and calculation steps, which is the fundamental prerequisite for ensuring high-precision measurement of the entire system.

[0015] Optionally, in some embodiments, the incident angle of the pulse measurement laser on the beam splitter is 45°, and the incident angle of the reference measurement laser on the mirror surface of the reflector is 45°.

[0016] By employing the technical solution described in the above embodiments and limiting specific incident angles of the optical path, a compact and easily assembled optical layout is achieved. Setting the incident angle to a classic 45° ensures that the reference optical path undergoes two 90° deflections after passing through the beam splitter and mirror, allowing it to be arranged parallel to the main optical path. This "U"-shaped folded optical path design significantly reduces the physical distance between the transmitting and receiving modules, enabling the entire optical system to be integrated into a smaller space, perfectly meeting the demands for product miniaturization and integration. Simultaneously, using standard angles reduces the difficulty of manufacturing and installing optical components, which is beneficial for controlling production costs and improving assembly efficiency.

[0017] Optionally, in some embodiments, the energy of the master measuring laser is greater than the energy of the reference measuring laser.

[0018] By employing the technical solution described in the above embodiments and asymmetrically allocating laser energy, the overall performance of the system is optimized, particularly its maximum range and ability to detect weakly reflective targets. Allocating most of the energy to the main measurement laser, which requires long-distance travel and undergoes significant attenuation, significantly improves the signal-to-noise ratio of the returned signal, ensuring effective measurement even at long distances or under harsh conditions. Simultaneously, only a small portion of the energy is needed to generate a stable and clear reference signal for the internal fixed-path reference optical path. This "using the best resources wisely" design represents the optimal energy utilization strategy for maximizing the system's ranging capability within a limited total transmission power.

[0019] Optionally, in some embodiments, the energy of the master measurement laser accounts for 90% to 99% of the energy of the pulse measurement laser, and the energy of the reference measurement laser accounts for 1% to 10% of the energy of the pulse measurement laser.

[0020] The technical solution employed in the above embodiments provides a specific, engineering-achievable golden ratio range for asymmetric energy allocation, achieving an optimal balance between performance and efficiency. Limiting the main measurement laser energy to 90% to 99% is crucial to ensuring the system has a sufficiently long measurement range and robustness, guaranteeing that the returned signal remains valid even under extreme conditions. Simultaneously, limiting the reference laser energy to 1% to 10% ensures that the reference signal itself has a sufficiently high signal-to-noise ratio to serve as a stable time reference, while avoiding excessive energy allocation to the reference optical path and wasting valuable power that could be used to increase the measurement range. This range provides clear technical specifications for the design of the beam splitter, enabling the engineering implementation of theoretical concepts.

[0021] Optionally, in some embodiments, the data processing module is further configured to: determine the internal flight time of the system based on the timestamp information of the reference pulse sensing signal and the pulse measurement laser; and determine the health status of the device based on the internal flight time of the system.

[0022] The technical solution described above adds a crucial online self-diagnostic and predictive maintenance function to the system, significantly improving the reliability and maintainability of the equipment. By continuously monitoring the "internal flight time" from laser emission to the return of the reference signal, the health status of core components can be monitored in real time. This time value is like the equipment's "heart rate"; its stability indicates good equipment health, while slow drift or sudden changes indicate component aging or failure. This allows the system to "sense" its own health status and provide early warnings, avoiding losses caused by sudden equipment failures and meeting the needs of high-reliability application scenarios.

[0023] Optionally, in some embodiments, the data processing module is further configured to: calculate the difference between the rise time of the reference pulse of the reference pulse sensing signal and the rise time of the measurement pulse of the pulse measurement laser, to obtain the internal flight time of the system.

[0024] The technical solution described above provides a specific, stable, and effective method for determining the "system internal flight time." By calculating the time difference between the rising edge of the reference pulse and the rising edge of the transmitted pulse, an internal delay measurement benchmark based on the event "start point" is established. This method can accurately reflect the comprehensive delay of the entire link from electrical signal triggering to the return and processing of the optical signal. Since the rising edge serves as the start marker of the pulse, its timing is relatively stable and not easily affected by factors such as pulse width variations. Therefore, the internal flight time data calculated using the rising edge difference is more reliable, providing a high-quality and trustworthy basis for subsequent equipment health status diagnosis.

[0025] Optionally, in some embodiments, the data processing module is further configured to: calculate the difference between the falling edge time of the reference pulse of the reference pulse sensing signal and the falling edge time of the measurement pulse of the pulse measurement laser, to obtain the internal flight time of the system.

[0026] The technical solution described above provides another dimension of measurement for determining "internal flight time of the system," offering richer information for equipment health diagnosis. By calculating the time difference between the "falling edge" of the reference pulse and the transmitted pulse, not only can the signal transmission delay be monitored, but changes in the pulse waveform can also be indirectly reflected. Calculating the difference between the two can more precisely distinguish whether it is a simple change in transmission delay or pulse broadening or narrowing caused by component aging. This multi-dimensional monitoring capability makes the diagnosis of equipment health status more comprehensive and in-depth, enabling the identification of more complex potential fault modes.

[0027] One or more technical solutions provided by this invention have at least the following technical effects or advantages:

[0028] 1. Achieving high immunity to environmental interference and superior stability through a differential offset architecture: A unique dual-path differential architecture fundamentally solves the measurement drift problem caused by environmental changes. Unlike traditional single-path systems, this invention creatively establishes an internal reference path that is identical or symmetrical in circuit design to the main measurement path. When environmental factors such as temperature and supply voltage fluctuate, the resulting electronic component delay drift is applied equally to these two parallel signal links in the form of "common-mode noise." When calculating the final flight time, the data processing module does not measure an absolute value, but rather calculates the difference between the arrival times of the main and reference signals. In this differential operation, equal-sized and identically oriented common-mode drifts are precisely canceled out. This allows the system to be "immune" to environmental interference without any complex and expensive temperature control or frequent calibration, outputting an extremely stable measurement result, laying the most solid foundation for high-precision ranging.

[0029] 2. Achieving millimeter-level high-precision measurement of different targets through dual-layer feature calibration: While ensuring stability, this invention overcomes the "walking error" caused by the different reflectivity of the measured target through a sophisticated feature calibration mechanism, thereby achieving extremely high measurement accuracy. First, the system directly quantifies the energy intensity of the returned signal by measuring the pulse width of the main pulse sensing signal and compensates for the walking error according to a preset lookup table or functional relationship. Second, to make the calibration process more robust, this invention further optimizes the calculation of the "pulse width ratio" between the main pulse and the internal reference pulse. This ratio more purely reflects the target characteristics because it eliminates the influence of pulse broadening or narrowing caused by environmental changes in the calculation. This dual-layer progressive calibration strategy ensures that the system can obtain accurately corrected flight times regardless of whether facing bright metal surfaces or dark light-absorbing materials, which is a key guarantee for achieving millimeter-level accuracy.

[0030] 3. Proactive self-diagnosis and high reliability through internal time-of-flight monitoring: This invention goes beyond simple ranging, endowing the device with entirely new "self-awareness" and "health monitoring" capabilities, significantly improving the system's long-term reliability. By continuously measuring and analyzing the fixed "internal time of flight" from laser emission to the return of the reference signal, the system obtains a "health fingerprint" that accurately reflects the comprehensive performance of core optoelectronic components. Any minute changes caused by component aging, performance degradation, or potential faults will cause this internal time-of-flight value to deviate from its factory baseline. The data processing module can capture this deviation in real time, thereby enabling online diagnosis of the device's health status and predictive maintenance alerts. This upgrades the device from a passive measurement tool into an intelligent sensor capable of anticipating its own risks and ensuring highly reliable data, possessing immeasurable value in safety-critical fields such as autonomous driving and precision manufacturing. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the architecture of a TOF-based laser ranging system according to an embodiment of the present invention.

[0032] Figure 2 This is a pulse timing diagram of a laser measurement signal in an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the software interface of the laser ranging system in an embodiment of the present invention. Detailed Implementation

[0034] The terminology used in the following embodiments of the present invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the invention, the singular expressions “a,” “an,” “the,” “the,” and “this” are intended to include the plural expressions as well, unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in the invention refers to any or all possible combinations comprising one or more of the listed items.

[0035] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as implying relative importance or implicitly indicating the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature, and in the description of the embodiments of the present invention, unless otherwise stated, "a plurality of" means two or more.

[0036] It should also be noted that, unless otherwise explicitly specified and limited, the terms "setting" and "connection" in the embodiments of the present invention should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components; it can be a wired communication connection or a wireless communication connection. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances. The embodiments of the present invention will be described in detail below.

[0037] In single-channel receiver TOF systems, the performance of internal electronic components (such as APDs, amplifiers, and comparators) can drift slightly with changes in ambient temperature and supply voltage. This drift leads to uncertainty in signal processing delay time, resulting in measurement errors and affecting measurement accuracy.

[0038] Therefore, this invention provides a Time-of-Flight (TOF) based laser ranging system. Through an innovatively designed dual-path differential receiver architecture, it effectively solves the technical problem in related technologies where single-path receiver systems experience performance drift in electronic components due to environmental changes, leading to measurement errors.

[0039] This invention cleverly adds a reference receiving module with the same or symmetrical circuitry as the main receiving module, and constructs an internal reference optical path with a fixed optical path. When environmental factors (such as temperature) change, the signal processing delay drift caused by this change to the main and reference receiving links is "common-mode," meaning that the two links will produce delay changes of approximately the same magnitude and direction. The data processing module does not measure the absolute arrival time of the main received signal, but rather calculates the timestamp difference between the main pulse sensing signal and the reference pulse sensing signal, i.e., the initial differential time of flight. During differential calculation, the "common-mode" delay drift added to the two links is canceled out, thus effectively removing it from the final time of flight calculation. This "differential offsetting" design ensures that the measurement result purely reflects the actual flight time that the main measuring laser has compared to the reference measuring laser, and is no longer affected by the performance drift of electronic components, effectively improving the anti-environmental interference capability of the TOF laser ranging system and the accuracy and reliability of the measurement results.

[0040] The following is combined Figure 1 This invention provides a Time-of-Flight (TOF) based laser ranging system, comprising a data processing module 1, a laser emitting module 2, a beam splitter 3, a reflector 4, a main receiving module 5, and a reference receiving module 6. Wherein:

[0041] Laser emitting module 2 is used to emit pulse measurement laser.

[0042] In some embodiments, the laser emitting module 2 can generate short, high-peak-power optical pulses with pulse widths on the order of nanoseconds, which is crucial for achieving high distance resolution. The hardware of the laser emitting module 2 may include a pulsed laser diode (LD), a high-speed laser driver, and a collimating optical lens. The driver (typically a dedicated driver IC based on GaN FETs) receives a trigger signal from the data processing module 1 and instantaneously injects a large current into the LD, causing it to generate a concentrated laser pulse. The lens group collimates the diverging beam emitted by the LD into parallel light, ensuring that the energy is effectively projected onto distant targets.

[0043] In this embodiment, the product selection for the laser emitting module 2 can be as follows: the laser diode can be a 660nm red LD designed specifically for pulse applications, such as Osram's SPL PL90_3 or Ushio's HL65014DG; the driver can be an iC-HG series high-speed laser switch from iC-Haus, or a GaN driver such as Texas Instruments' LMG1020 can be used to build the module yourself.

[0044] The beam splitter 3 is positioned in the light output direction of the laser emitting module 2 to split the pulse measurement laser into a reference measurement laser and a main measurement laser. The reference measurement laser is directed toward the reflector 4, and the main measurement laser is directed toward the target being measured.

[0045] Specifically, in this embodiment, the function of the beam splitter 3 is to precisely distribute the energy of the laser beam in the optical path. The beam splitter 3 is precisely positioned after the laser emitting module 2, splitting the emitted pulse measurement laser into two parts according to a predetermined ratio. For example, it may transmit a portion of the laser energy as the main measurement laser, while reflecting the other portion of the laser energy into the internal optical path of the system to form a reference measurement laser.

[0046] In some embodiments, the beam splitter 3 can be an optical plate or cemented prism with a specific semi-transparent and semi-reflective dielectric film layer. The film layer needs to be designed to precisely match the laser wavelength (e.g., 660 nm) and the required splitting ratio, and has a high damage threshold and low absorption loss. The beam splitter 3 can be customized or purchased from specialized optical component manufacturers, such as Thorlabs' plate beam splitters (e.g., BSN10R) or related customized products from Edmund Optics.

[0047] The reflector 4 is used to reflect the reference measurement laser to the reference receiving module 6. Specifically, in this embodiment, the reflector 4 functions to construct a relatively stable and fixed-path internal reference optical path. It is used to accurately receive the reference measurement laser split by the beam splitter 3 and reflect the reference measurement laser to the reference receiving module 6 at a specific angle.

[0048] To ensure the stability of the reference optical path and signal quality, the reflector 4 can be a high-quality first surface mirror, meaning the reflective coating is deposited on the first surface of the substrate to eliminate ghosting and optical path errors. The coating is typically a multilayer dielectric high-reflectivity coating optimized for the operating wavelength (660nm) to achieve a reflectivity greater than 99.5% and extremely high durability.

[0049] In this embodiment, the model of the reflector 4 can be selected from Thorlabs' -AG (enhanced silver film) or -P01 (protective dielectric film) series reflectors 4, or Newport's high-precision optical reflector 4.

[0050] The main receiving module 5 is used to receive the main measuring laser reflected back from the target under test and generate the main pulse sensing signal. The circuits of the main receiving module 5 and the reference receiving module 6 are the same or symmetrical.

[0051] In this embodiment, the main receiving module 5 is responsible for detecting the main measurement laser, which is typically weak and uncertain in signal strength, diffusely reflected from the target. Its core hardware chain consists of an avalanche photodiode (APD), a transimpedance amplifier (TIA), and a high-speed comparator. The APD, as a photodetector, utilizes its internal avalanche multiplication effect to convert weak light signals into measurable current signals, exhibiting extremely high sensitivity. The TIA rapidly and with low noise converts the high-impedance current signal output by the APD into a voltage signal. Finally, the high-speed comparator compares the amplified analog pulse signal with a set threshold voltage, generating a steep-edge digital logic signal (main pulse sensing signal), which is sent to the data processing module 1 for timestamping. Commonly used devices include Hamamatsu's S-series APDs, Analog Devices' high-speed, low-noise TIAs (such as the LTC6561), and high-speed comparators (such as the ADCMP582).

[0052] In this embodiment, the circuits of the main receiving module and the reference receiving module are designed to be "identical or symmetrical." The core objective is to ensure precise electrical matching between the two signal processing links, thereby laying the physical foundation for subsequent differential offsetting. "Identical" mainly refers to the use of completely identical hardware in both modules at the component level, including but not limited to the same type of avalanche photodiode (APD), transimpedance amplifier (TIA), high-speed comparator, and resistors and capacitors with the same nominal values ​​and tolerance levels. "Symmetrical" goes further, emphasizing that at the physical layout level of the printed circuit board (PCB), the traces of the two signal links should be mirrored or translated symmetrically. This requires that the length, width, and impedance of the signal paths be strictly equal, the relative positions of key components achieve symmetrical heat distribution, and the grounding and power paths also need to be carefully designed to maintain consistency.

[0053] This rigorous matching, from component selection to physical layout, aims not only to ensure that the two links have equal initial delays, but more importantly, to guarantee that the delay drift they experience is equal in magnitude and direction when factors such as ambient temperature and supply voltage change. Only in this way can this drift become a true "common-mode error," cleanly canceled out in the final differential calculation, thereby achieving a high degree of immunity to environmental interference.

[0054] Reference receiver module 6 is used to receive the reference measurement laser and generate a reference pulse sensing signal. The main function of reference receiver module 6 is to provide the system with an extremely stable internal time reference that is unaffected by external targets, in order to compensate for electronic delay drift caused by temperature and voltage changes.

[0055] In this embodiment, the hardware circuit design of the reference receiving module 6 needs to be "the same or symmetrical" as that of the main receiving module 5. This means that it uses the same avalanche photodiode, transimpedance amplifier, high-speed comparator, and peripheral circuit layout as the main receiving module 5. The reference receiving module 6 receives the reference measurement laser with relatively stable light intensity reflected by the reflector 4, and also generates a digital logic signal (i.e., a reference pulse sensing signal).

[0056] Due to the hardware consistency between the two modules, delay drift caused by environmental changes will appear equally on both signals, thus being effectively eliminated in subsequent differential time calculations. Therefore, the component selection for reference receiver module 6 can reuse the scheme of main receiver module 5, such as Hamamatsu's APD, Analog Devices' TIA, and comparators.

[0057] The data processing module 1 is connected to the reference receiving module 6 and the main receiving module 5 respectively, and is used to: determine the initial differential flight time based on the timestamp information of the main pulse sensing signal and the reference pulse sensing signal; and calculate the ranging result of the target based on the initial differential flight time and the speed of light.

[0058] In this embodiment, the core of the calculation process performed by the data processing module 1 lies in its integrated high-precision timing unit, typically a time-to-digital converter (TDC). When the reference pulse sensing signal from the reference receiving module 6 arrives first, the timing unit immediately captures its arrival time and records it as a high-resolution digital timestamp, denoted as T_reference. Subsequently, when the main pulse sensing signal reflected back from the target arrives at the main receiving module 5 and is sent to the data processing module 1, the timing unit again captures its arrival time in the same manner and records it as a timestamp T_main. Next, the module performs the core differential operation, subtracting the timestamp of the first-arriving reference pulse (i.e., T_main - T_reference) from the timestamp of the later-arriving main pulse to obtain a time difference value. This difference value is the "initial differential flight time" ΔT. Physically, ΔT precisely represents the extra pure flight time compared to the internal reference optical path, which is consumed by the main measuring laser as it travels from the beam splitter 3, rounds the target, and returns to the system. Finally, in order to calculate the distance to the target, the data processing module 1 divides the initial differential flight time ΔT by 2 (because ΔT is the round-trip time, dividing by 2 gives the one-way flight time), and then multiplies it by the speed of light c. That is, by using the formula (distance = (ΔT / 2) × c), a high-precision ranging result is finally calculated.

[0059] In this embodiment, the data processing module 1 uses the differential hedging principle to eliminate the performance drift problem of electronic components:

[0060] When the ambient temperature changes, the time delay drift (Δt_drift) generated by the main receiving module 5 and the reference receiving module 6 is basically the same because the circuits of the main receiving module 5 and the reference receiving module 6 are the same or symmetrical. This is a common-mode error.

[0061] The flight time calculated by data processing module 1 is not directly based on the flight time of the main measurement laser, but rather by subtracting the time of the reference pulse sensing signal (t_reference) from the time of the main pulse sensing signal (t_main). During this subtraction, the common-mode drift (i.e., common-mode error Δt_drift) between the two signals is precisely canceled out.

[0062] (t_main - t_reference) = (actual flight time + circuit delay + Δt_drift) - (fixed internal optical path time + circuit delay + Δt_drift) = actual flight time - fixed internal optical path time.

[0063] In this way, measurement jitter and drift caused by factors such as temperature and circuit delay are effectively eliminated, thus providing an accurate data basis for calculating the final distance measurement result.

[0064] In some embodiments, the data processing module 1 may employ a field-programmable gate array (FPGA) module, whose primary responsibility is to perform high-precision time measurements at the nanosecond or even picosecond level. The data processing module 1 integrates time-to-digital converter (TDC) logic, which is capable of capturing the rising or falling edges of the pulse signals transmitted from the main and reference receiving modules with extremely high resolution and stamping them with precise timestamps.

[0065] Meanwhile, data processing module 1 is also responsible for generating the high-frequency pulse sequence required to drive laser emission module 2, performing differential time calculations, and finally outputting the distance value through a standard interface (such as SPI or UART). For field frequency selection, products with low-jitter clock management units and abundant logic resources can be used, such as the Xilinx (AMD) Artix-7 / Zynq-7000 series or Intel (Altera) Cyclone V / Arria series FPGAs, which can provide the hardware resources required to implement high-performance TDC and complex real-time algorithms.

[0066] In some embodiments, the data processing module 1 may also employ a microcontroller (MCU) + dedicated time-to-digital converter (TDC) chip, or a system-on-a-chip (SoC) or other alternatives.

[0067] The working principle of the laser ranging system in this embodiment can be referred to as follows:

[0068] First, data processing module 1 issues a start command for one measurement cycle. Data processing module 1 sends a trigger signal to laser emission module 2, which then emits a short, high-peak-power pulse measurement laser. This laser pulse first encounters beam splitter 3 on its outgoing optical path, where it is precisely split in two. A portion of the laser energy is reflected by beam splitter 3, forming a reference measurement laser, which travels along a fixed-length optical path within the system towards reflector 4. The other portion of the laser energy passes through beam splitter 3, forming the main measurement laser, which continues to travel along the main optical axis towards the distant target.

[0069] Next, events occur in parallel on both optical paths. In the internal reference optical path, the reference measurement laser is precisely reflected back to the reference receiving module 6 by the reflector 4. Upon receiving the optical signal, the reference receiving module 6 immediately generates a reference pulse sensing signal with precise timing characteristics using its internal photodetector and processing circuitry, and sends it to the data processing module 1. Almost simultaneously, in the external main optical path, the main measurement laser undergoes diffuse reflection upon reaching the surface of the target object. A portion of the reflected light returns along the original path and is eventually captured by the main receiving module 5. Similar to the reference receiving module 6, the main receiving module 5 also generates a main pulse sensing signal upon receiving this weak return light, and similarly sends it to the data processing module 1.

[0070] Data processing module 1 is the core of the entire process. It simultaneously receives two pulse sensing signals from reference receiving module 6 and main receiving module 5. Its internal high-precision timing unit (such as a time-to-digital converter TDC) accurately timestamps the arrival of these two signals, denoted as T_reference and T_main. The key technical step is that data processing module 1 does not use T_main alone to calculate the distance, but instead calculates the difference between the two timestamps, i.e., the initial differential flight time ΔT = T_main - T_reference. Since the circuit design of main receiving module 5 and reference receiving module 6 is identical or symmetrical, any signal processing delay drift caused by changes in ambient temperature or supply voltage will appear equally in both links, forming common-mode drift. During differential operation, this common-mode drift is canceled out, resulting in a pure time difference unaffected by environmental factors.

[0071] Finally, data processing module 1 uses this highly stable initial differential flight time ΔT, which directly corresponds to the extra round-trip time traveled by the main measuring laser compared to the reference measuring laser. Combined with the speed of light c, data processing module 1 can accurately calculate the distance from the system to the target using the formula (distance = ΔT * c / 2).

[0072] The above workflow is executed multiple times at a very high frequency, thereby achieving continuous, real-time, and high-precision distance measurement of the target.

[0073] To address the performance drift problem of electronic components in laser ranging systems, solutions typically employ complex temperature control systems or frequent periodic calibrations. However, this not only increases system cost and power consumption but also makes the system structure more complex, making it difficult to meet the requirements of miniaturization and low cost applications.

[0074] The embodiments of this invention employ the aforementioned system architecture design. By constructing a reference receiving module 6 with the same or symmetrical circuitry as the main receiving module 5, and utilizing an internally fixed optical path to form a reference optical path, an intrinsic, real-time self-calibration mechanism is cleverly established. The essence of this "differential offsetting" architecture lies in the fact that any performance drift of electronic components caused by factors such as ambient temperature and supply voltage will be simultaneously and equally applied to both the main and reference receiving links in the form of "common-mode" noise. When the data processing module 1 calculates the timestamp difference between the main and reference pulse signals, these drifts of equal magnitude and in the same direction are precisely canceled out in mathematical operations. In this way, the embodiments of this invention do not require additional, bulky temperature control hardware (such as heating elements or cooling fans) or periodic calibration procedures that interrupt measurements, fundamentally avoiding or greatly reducing interference from environmental factors. This not only simplifies system design and significantly reduces material costs and operating power consumption, but also makes the entire system more compact, perfectly meeting the application requirements of miniaturization and low cost.

[0075] Ultimately, this embodiment improves and ensures the measurement accuracy and long-term operational reliability of the TOF ranging system in a more efficient and cost-effective manner without increasing the system's additional complexity.

[0076] In some embodiments, the data processing module 1 is also connected to the laser emitting module 2. When the laser emitting module 2 emits a pulse to measure the laser, it also sends an emission feedback pulse signal to the data processing module 1.

[0077] This embodiment establishes an extremely accurate and reliable "zero time" (T0) reference, which significantly improves the absolute accuracy and long-term stability of the entire ranging system from the source.

[0078] Without this design, the data processing module 1 can only use the moment of the drive command it issues as the starting point of timing, but this ignores the inherent response delay of the internal electronic components (such as the drive chip) of the laser emission module 2, which is subject to environmental changes.

[0079] This embodiment fundamentally solves the problem by adding a connection between the laser emission module 2 and the data processing module 1, and transmitting back a transmission feedback pulse signal that is strictly synchronized with the actual optical pulse emission in real time.

[0080] Specifically, the laser emitting module 2 integrates a signal "pick-off" or monitoring circuit that directly monitors the current pulses driving the laser diode. The circuit generates a high-fidelity synchronization pulse and sends it to the data processing module 1 the instant the driving current actually flows through the laser diode. In this way, the data processing module 1 can use this returned pulse signal, representing the actual physical emission event, as the authoritative T0 reference point for all time-of-flight calculations, effectively eliminating the delay drift of the laser driver itself due to temperature, voltage, or aging from the entire measurement chain. This provides a precise time reference for subsequent differential offsetting and travel error calibration.

[0081] In some embodiments, the timestamp information of the main pulse sensing signal includes the rising edge time of the main pulse, and the timestamp information of the reference pulse sensing signal includes the rising edge time of the reference pulse; the data processing module 1 is specifically used to calculate the time difference between the rising edge time of the main pulse and the rising edge time of the reference pulse to obtain the initial differential flight time.

[0082] Specifically, the time-to-digital converter (TDC) inside the data processing module 1 is precisely configured to capture only the rising edge of the input pulse signal. When the voltage of the digital pulse signal generated by the reference receiving module 6 transitions from low to high, the TDC immediately records this precise moment as the "reference pulse rising edge time". Similarly, when the pulse signal generated by the main receiving module 5 transitions from low to high, the TDC also records its "main pulse rising edge time".

[0083] Subsequently, data processing module 1 performs a simple subtraction operation, that is, subtracting the first-arriving "reference pulse rise time" from the later-arriving "main pulse rise time". The result of this calculation is the initial differential flight time.

[0084] The advantage of this technique, which uses only the rising edge for time measurement, is that it greatly simplifies the time measurement logic, reduces the demand for TDC channel resources, and standardizes the measurement reference point. By using the starting point (rising edge) of the pulse as the timing basis, it effectively avoids unstable factors such as falling edge jitter that may be introduced due to changes in pulse width. This results in a more stable and consistent time difference value in the fundamental step of calculating the initial differential flight time, providing a more reliable raw data for subsequent travel error calibration.

[0085] The following is combined Figure 2 To explain in detail the calculation principle of the initial differential flight time in this embodiment:

[0086] The rise and fall times of the transmitted feedback pulse signal are t1 and t2, respectively. The rise and fall times of the reference pulse sensing signal are t3 and t4, respectively. The rise and fall times of the main pulse sensing signal are t5 and t6, respectively.

[0087] The core principle of calculating the initial differential flight time lies in using an internal reference optical path as a stable and unchanging "ruler" to accurately measure the length expansion and contraction of the main measurement optical path (the "ruler") caused by changes in target distance. The entire calculation process ingeniously isolates the time consumed purely by the target's round-trip flight, while simultaneously offsetting the system's own electronic delays that vary with the environment. The specific implementation is as follows:

[0088] First, the high-precision timing unit inside the data processing module captures the moments of all critical events. When the laser emitting module actually emits light, a synchronous emission feedback pulse signal arrives at the data processing module, and its rising and falling edges are recorded as t1 and t2. This is a marker of the system's "zero moment," primarily used for equipment health diagnostics.

[0089] Following this, after a very short, fixed optical path within the system, the reference measurement laser reaches the reference receiving module. The rising and falling edges of the generated reference pulse sensing signal are recorded as t3 and t4. The timestamp (reference pulse rise time) t3 represents the total time required for the beam to propagate within the system and be processed by the electronic link; it is a relatively fixed reference value.

[0090] Finally, the main measurement laser, having traveled a considerable external distance and reflected back from the target, reaches the main receiving module. The rising and falling edges of the generated sensing signal are recorded as t5 and t6. The timestamp (main pulse rise time) t5 includes the same internal electronic link delay as t3, plus the additional, and truly important, clean flight time of the beam to and from the target.

[0091] The key step in calculating the "initial differential time of flight" is performing a core differential operation. The rising edge of the signal can be chosen as the most stable timing reference. Therefore, the data processing module will use the rising edge time t5 of the later-arriving main pulse to subtract the rising edge time t3 of the earlier-arriving reference pulse. That is: Initial differential time of flight ΔT = t5 - t3.

[0092] The essence of this subtraction operation lies in the fact that, since the circuit designs of the main and reference receiving modules are identical or symmetrical, their inherent electronic delay (the part that drifts with environmental factors such as temperature) exists as a "common-mode" term in t5 and t3. During the process of subtracting t3 from t5, this common, variable delay can be precisely canceled out and eliminated.

[0093] Therefore, the final difference ΔT is a highly stable time value that has been freed from the influence of environmental drift. It physically corresponds directly to the time taken by the main optical path to travel an extra portion of the clean optical path to the target compared to the reference optical path. The two falling edge times, t4 and t6, can be used to calculate the pulse width (t4-t3 and t6-t5).

[0094] In some embodiments, the data processing module 1 is further specifically used to: determine the walking error parameter based on the pulse width of the main pulse sensing signal; generate a calibration flight time based on the initial differential flight time and the walking error parameter; and calculate the calibrated ranging result of the target based on the calibration flight time and the speed of light.

[0095] First, after capturing the rising and falling edges of the main pulse sensing signal, the data processing module 1 calculates the pulse width of the signal by the difference between these two timestamps (t_falling edge - t_rising edge).

[0096] Because targets with different reflectivities return different light signal intensities at the same distance, this causes variations in the amplitude of the analog pulses output by the receiver amplifier. Consequently, the width of the digital pulses generated by the comparator at a fixed threshold also varies, which is the root cause of walk error. During the system design phase, the specific time correction values ​​corresponding to different pulse widths are pre-calibrated experimentally. This calibration data is created as a look-up table (LUT) or a fitted mathematical function and pre-stored in the memory of data processing module 1. Therefore, during actual measurement, data processing module 1 only needs to use the real-time measured pulse width value as an index to look up this pre-stored LUT or substitute it into the function for calculation to quickly and directly obtain the walk error parameters required under the current measurement conditions. This parameter is usually a time value that needs to be compensated.

[0097] Then, after obtaining the initial differential flight time (ΔT_initial) calculated by the differential offset principle and the walking error parameters (ΔT_correction) obtained from the pulse width lookup table, data processing module 1 performs an arithmetic correction operation. It adds or subtracts the initial differential flight time from the walking error parameters to offset the time measurement deviation introduced by signal amplitude variations. Specifically, the operation is: ΔT_calibration = ΔT_initial - ΔT_correction. This step further refines the initial flight time, which previously only addressed common-mode drift, generating a more accurate "calibrated flight time" that simultaneously eliminates the effects of environmental drift and target reflectivity.

[0098] Finally, after obtaining the final calibrated flight time (ΔT_calibration) after two-step calibration (differential offsetting and travel error correction), data processing module 1 performs the final distance conversion. This process is similar to the previous calculations, but uses a fully corrected time value. It divides this high-precision calibrated flight time by 2 to obtain the one-way flight time, and then multiplies it by the speed of light constant c. That is, the final calibrated ranging result = (ΔT_calibration / 2) × c.

[0099] Compared to results obtained using only the initial differential time of flight, this calculation result is more accurate because it not only eliminates drift caused by environmental factors but also compensates for measurement errors introduced by differences in the optical characteristics of the target itself, thus achieving truly high-precision and high-accuracy ranging.

[0100] In some embodiments, the data processing module 1 is further specifically used to: calculate the pulse width ratio of the main pulse sensing signal to the reference pulse sensing signal or the pulse measurement laser; and determine the walking error parameter corresponding to the pulse width ratio based on the preset walking error correspondence relationship of the pulse width ratio.

[0101] Specifically, the data processing module 1 first calculates the pulse width (PW_main) of the main pulse sensing signal generated by the main receiving module 5 and the pulse width (PW_reference) of the reference pulse sensing signal generated by the reference receiving module 6; alternatively, it can directly monitor the current pulse on the laser driving circuit to obtain the original pulse measurement laser pulse width (PW_emission).

[0102] Then, data processing module 1 performs a division operation, dividing the pulse width of the main pulse by the pulse width of the reference pulse to obtain a ratio: Ratio = PW_main / PW_reference (or Ratio = PW_main / PW_emit). This ratio is a dimensionless relative value, and its key advantage is that if factors such as ambient temperature cause slight changes in the overall response characteristics of electronic components (e.g., all pulses become proportionally wider or narrower), such changes are automatically eliminated when calculating the ratio. Therefore, this pulse width ratio can more purely and stably reflect the changes in echo signal energy caused by differences in target reflectivity, and is more robust than directly using the absolute pulse width of the main pulse.

[0103] The system undergoes a precise calibration process before leaving the factory. During calibration, a standard target board at a known distance is placed in front of the ranging system, and then target boards with different reflectivities (such as grayscale cards from 5% to 90%) are replaced sequentially. For each reflectivity, the system measures the corresponding pulse width ratio and the actual ranging error (i.e., walking error). By collecting a large number of such data points (pulse width ratio, walking error), a precise "pulse width ratio - walking error" correspondence can be constructed. This pulse width ratio-walking error correspondence can be stored as a lookup table (LUT) or a polynomial fitting function, and pre-set in the non-volatile memory of data processing module 1.

[0104] In the actual measurement process, after calculating the real-time pulse width ratio, data processing module 1 uses this ratio as input to query the preset correspondence table or substitute it into the fitting function for calculation. In this way, it can quickly and accurately query or calculate the specific walking error revealed by the specific pulse width ratio under the current measurement conditions, thereby obtaining an accurate walking error parameter (usually a time compensation value), which prepares for subsequent time-of-flight calibration.

[0105] This embodiment takes into account that when a high-speed electronic system (such as an amplifier in a receiver) is excited by a rapidly rising pulse, it not only saturates, but its internal parasitic inductance and capacitance (LC network) may also be "excited" at certain signal strengths, producing a resonance-like "ringing" or "overshoot" phenomenon. This phenomenon leads to additional, non-monotonic delays. As the signal strength increases further, deep saturation, in turn, "suppresses" or "damps" this resonance.

[0106] Therefore, this embodiment constructs a walking error calibration function based on a saturated damped resonance model to simulate the relationship between pulse width ratio and walking error. The mathematical expression of the walking error calibration function is as follows:

[0107]

[0108] Where, ΔT walk This represents the time correction amount for walking error.

[0109] R is the independent variable of the function, representing the pulse width ratio measured in real time.

[0110] A represents the saturation error amplitude, which determines the maximum travel error time caused by the base saturation effect.

[0111] R0 represents the static operating point ratio, which defines the central reference point of the entire calibration model, i.e., the operating point where the basic saturation error is considered zero at this pulse width ratio.

[0112] R µ The ratio of the resonant centers determines the pulse width ratio point where the resonance effect is most significant, i.e., the precise location of the resonant peak on the coordinate axis.

[0113] α represents the saturation sensitivity factor, which is used to control how quickly the walking error curve enters the saturation region, i.e., the system's response sensitivity to changes in signal strength.

[0114] B represents the resonant coupling coefficient, which is used to adjust the peak intensity of the resonant effect, i.e., the maximum contribution of the resonant phenomenon to the total walking error.

[0115] σ represents the resonant bandwidth, which describes the width range of the resonant peak, i.e. the concentration of pulse width ratios that can effectively excite the resonant effect.

[0116] T offset Represents the static time offset, which is a constant time offset inherent to the system and independent of signal strength. It is used for overall translation calibration of the entire function.

[0117] Among the parameters mentioned above, ΔT walk A, B, T offset The dimensions of R, R0, and R are all time-based. µ α and σ are all dimensionless pure numerical values.

[0118] In this walking error calibration function, The basic saturation term describes the fundamental behavior of the walking error: as the signal strengthens (pulse width ratio R increases), the error smoothly and nonlinearly grows until it eventually saturates. The hyperbolic tangent function tanh is used to better describe the saturation phenomenon; its range is (-1, 1). The hyperbolic tangent function tanh is a mathematically smooth and centrally symmetric S-shaped curve, which can well simulate the physical process of an electronic amplifier moving from the linear region, through the nonlinear inflection point, to finally entering a hard saturation state, truly reflecting the physical constraint that the walking error will not grow indefinitely.

[0119] and As a damped resonant term, it effectively simulates the additional walking error caused by the excitation of the parasitic LC network inside the receiver within a specific signal strength range.

[0120] e^(-...): This is a Gaussian function, which is a bell curve representing a normal distribution. It simulates a "resonance peak" here.

[0121] B•(R-R0): This is a linear damping / gain term.

[0122] (R-R0): This term implies that the intensity of the resonance effect is proportional to the degree to which the signal deviates from the static operating point. However, when multiplied by a Gaussian function, it is cleverly "suppressed" back to zero by the exponentially decaying Gaussian function as R approaches infinity. This perfectly simulates the suppression effect of deep saturation on resonance: if the signal is too weak, resonance cannot be generated; if the signal is too strong, the circuit is "clamped" and cannot generate resonance either.

[0123] The walking error calibration function in this embodiment has the following characteristics:

[0124] Non-monotonicity: Unlike a simple S-curve, this function can be non-monotonic. That is, the walking error may not increase indefinitely with increasing signal strength; it may exhibit a "bump" or "dip" in the resonant region before saturating. This phenomenon is entirely possible in real-world precision measurements, making the model very realistic.

[0125] Multi-physics coupling: Instead of fitting data with a simple function, it mathematically couples the two independent physical processes of saturation and resonance. This embodies a higher-level system modeling concept.

[0126] High interpretability: Each parameter of the model (A, α, R0, B, R) µ Each of these (σ) corresponds to a clear and interpretable physical or electronic concept, making the calibration process not just curve fitting, but also "reverse engineering" and a deep understanding of the receiver hardware characteristics.

[0127] The computational complexity is moderate: the function includes hyperbolic tangent, exponential, and multiplication operations, which is slightly more complex than simple polynomials or lookup tables, but meets the requirements. It is perfectly feasible to implement on modern microprocessors (MCUs / FPGAs) using the CORDIC algorithm or floating-point arithmetic units.

[0128] In some embodiments, considering that the walking error calibration relies on a pre-calibrated, static lookup table (LUT) at the factory, this LUT may not be able to adapt to changes brought about by the aging of the device's own life cycle (such as APD gain degradation, comparator offset, etc.). Therefore, this embodiment establishes an "online self-calibration" mechanism. Specific implementation process:

[0129] 1) Variable Optical Attenuator (VOA): In the reference optical path (such as between beam splitter 3 and mirror 4), an electronically controlled variable optical attenuator (such as liquid crystal or MEMS VOA) is creatively introduced.

[0130] 2) Self-calibration mode: Data processing module 1 can manipulate this VOA during non-working intervals or specific self-test cycles to actively and gradually change the intensity of the reference optical path.

[0131] 3) Online Generation of "Miniature LUT": In self-calibration mode, the FPGA controls the VOA to generate reference light intensities at several known attenuation levels. For each intensity level, the FPGA measures its "virtual" walk error (i.e., the change in the arrival time of the reference pulse) and the corresponding reference pulse width. Using these (pulse width, error) data points, the system can fit or correct a set of the most accurate walk error calibration curve / LUT under the current equipment state online in real time.

[0132] This design in this embodiment transforms a static calibration process into a dynamic, real-time self-correcting one. It enables the ranging system to self-diagnose and compensate for performance degradation throughout its entire lifecycle, significantly improving the product's long-term stability and reliability. This is of immense value for equipment deployed in harsh environments and requiring long-term maintenance-free operation. Essentially, it utilizes a stable and controllable internal reference optical path to simulate uncontrollable external target reflectivity changes, thereby completing an "online check-up and calibration" of the entire measurement system.

[0133] In some embodiments, the incident angle of the pulse measurement laser on the beam splitter 3 is 45°, and the incident angle of the reference measurement laser on the mirror surface of the reflector 4 is 45°.

[0134] This embodiment employs the above design, achieving a compact system structure and simplified optical path construction. When the pulsed measurement laser is incident on the beam splitter 3 at a 45° angle, its transmitted light (main measurement laser) continues to travel in the original direction, while the emitted reflected light (reference measurement laser) is deflected at a 90° angle to the main optical path. Similarly, when this 90° deflected reference laser is incident on another reflector 4 at a 45° angle, it will again undergo a 90° deflection.

[0135] These two 90° deflections ensure that the reference optical path ultimately directed towards the reference receiving module 6 remains parallel to the main optical path directed towards the main receiving module 5. This U-shaped folded optical path design allows for a compact, close-to-side arrangement of the transmitting module, main receiving module 5, and reference receiving module 6 on the circuit board, significantly reducing the physical size of the entire optical system and greatly facilitating product miniaturization and integration. Simultaneously, using a standard 45° angle simplifies the installation and debugging process of optical components, reducing the difficulty and cost of production assembly.

[0136] In some embodiments, the energy of the master measurement laser is greater than the energy of the reference measurement laser.

[0137] This embodiment employs a highly optimized, asymmetric allocation of the total laser energy to maximize the system's core performance—range measurement capability. This design fully considers the significant differences in physical characteristics between the primary and reference optical paths.

[0138] The main measurement laser needs to travel a long distance to reach the target and then be diffusely reflected back from a surface that is typically low in reflectivity. The energy attenuation during this process is extremely severe, resulting in a very weak signal reaching the main receiving module 5. Allocating most of the energy to the main measurement laser effectively increases the intensity of the returned light signal, thereby significantly improving the signal-to-noise ratio (SNR). A higher SNR means the system can more reliably distinguish the valid signal from background noise, which directly translates to a longer effective range and a stronger detection capability for low-reflectivity targets.

[0139] At the same time, the reference optical path is short and fixed, and the optical components are highly efficient. Only a small amount of energy is needed to generate a sufficiently strong and stable signal on the reference receiving module 6 for use as a precise time reference.

[0140] Therefore, this energy allocation strategy uses the limited total energy where it is most needed, greatly enhancing the system's practicality and robustness in real and complex environments without sacrificing the stability of the reference signal.

[0141] Furthermore, in some embodiments, the energy of the main measurement laser accounts for 90% to 99% of the energy of the pulse measurement laser, and the energy of the reference measurement laser accounts for 1% to 10% of the energy of the pulse measurement laser.

[0142] This design, through specific numerical ranges, further clarifies and quantifies the engineering "sweet spot" of the aforementioned energy optimization allocation, achieving the best balance in performance. This range is defined based on precise engineering trade-offs.

[0143] Setting the energy ratio of the main measuring laser to no less than 90% ensures that even under extreme conditions such as long distances, severe weather, or detecting dark targets, the signal energy returned to the main receiving module 5 can still be higher than the receiver's detection threshold, thus guaranteeing the basic availability and reliability of the ranging function.

[0144] Setting the energy ratio of the reference measurement laser to 1% is to ensure that the reference signal itself also has a sufficient signal-to-noise ratio, avoiding unnecessary jitter or noise due to a weak signal, thus guaranteeing its qualification as a highly stable "time anchor".

[0145] If the reference energy is higher than 10%, it means that too much energy is being used from the main measurement beam, which will unnecessarily sacrifice the system's maximum range and cause energy waste.

[0146] Therefore, this specific percentage range in this embodiment provides clear technical guidance for the design and manufacture of optical elements such as the beam splitter 3, ensuring that the system can achieve an optimal and engineering-feasible balance between maximizing ranging capability and maintaining a high-precision differential reference.

[0147] In some embodiments, the energy of the main measurement laser can preferably account for 95% of the energy of the pulse measurement laser, and the energy of the reference measurement laser can preferably account for 5% of the energy of the pulse measurement laser.

[0148] In some embodiments, the data processing module 1 is further configured to: determine the internal flight time of the system based on the timestamp information of the reference pulse sensing signal and the pulse measurement laser; and determine the health status of the device based on the internal flight time of the system.

[0149] Specifically, the data processing module 1 first sets a "zero time" reference for each measurement cycle in its internal system. This zero time is the instant when it sends a drive command to the laser emission module 2, and records a timestamp for this, denoted as T_emission.

[0150] Subsequently, when a portion of the laser light is captured by the reference receiving module 6 after passing through a fixed optical path such as beam splitting and reflection within the system, and a reference pulse sensing signal is generated and sent to the data processing module 1, the timestamp at this moment is recorded and denoted as T_reference.

[0151] Next, a subtraction operation is performed: T_reference - T_emission, resulting in the "system internal flight time". This time value includes the optical delay of light propagating along the fixed internal optical path, as well as a series of electronic delays, such as the laser being triggered, actual emission, photoelectric conversion by the reference receiving module 6, and signal processing. Since the optical path is fixed and the optical delay is constant, this "system internal flight time" becomes a highly sensitive "electronic fingerprint" characterizing the comprehensive response characteristics of the core components within the system.

[0152] In this embodiment, during the calibration process before leaving the factory, or during the self-test program at each startup, the system measures and stores a baseline "internal flight time" under a standard operating condition, which is called the "health baseline value", and sets a reasonable floating tolerance range for it.

[0153] During the continued operation of the equipment, data processing module 1 will repeatedly calculate the real-time internal flight time of the system in each measurement cycle. Then, it will compare this real-time value with the stored health baseline value. If the real-time value consistently fluctuates within the preset tolerance range, the equipment is considered to be in good health.

[0154] However, if the module detects a persistent, slow drift in this real-time value that exceeds the tolerance range, it may indicate that critical components such as the laser or receiver are aging or experiencing performance degradation. If a sudden change in the real-time value is detected or it becomes completely unmeasurable, it indicates a possible sudden damage to the components, contamination of the internal optical path, or serious misalignment.

[0155] Once an unhealthy state is determined, the system can trigger an alarm, record a fault log, or execute a preset safety policy, thereby achieving a powerful online self-diagnosis and predictive maintenance function, which greatly improves the reliability and maintainability of the equipment.

[0156] Furthermore, in some embodiments, the data processing module 1 is also used to: calculate the difference between the rise time of the reference pulse of the reference pulse sensing signal and the rise time of the measurement pulse of the pulse measurement laser to obtain the internal flight time of the system.

[0157] The data processing module 1 uses its internal high-precision timing unit (such as a time-to-digital converter TDC) to perform a precise calibration of the total electronic and optical delay within the system.

[0158] First, the data processing module 1 marks the rising edge of the driving pulse (i.e., the electronic source signal of the "pulse measurement laser") sent to the laser emission module 2 as a precise start timestamp, namely the "measurement pulse rising edge time", which can be regarded as the "zero moment" of the entire system event chain.

[0159] Next, after the laser beam undergoes internal splitting and reflection, it is received and processed by the reference receiving module 6. The reference receiving module 6 outputs a digital "reference pulse sensing signal". The rising edge of this signal is also captured by the timing unit of the data processing module 1 and recorded as the "reference pulse rising edge time".

[0160] Finally, data processing module 1 performs a precise subtraction operation, subtracting the previous "measurement pulse rise time" from the subsequent "reference pulse rise time". The difference obtained is the "system internal flight time". This time value physically encompasses the total link delay from the electrical signal triggering to the emission of the optical signal, the propagation of light in the internal fixed optical path, and then to the reception of the optical signal and its conversion back into an electrical signal.

[0161] By locking the starting point of the pulse—the rising edge—as the timing basis, this method provides an extremely stable and repeatable measurement benchmark for monitoring the internal delay of the system. It effectively eliminates the interference that may be caused by changes in pulse width, ensures the accuracy of the measured "internal flight time of the system," and lays a solid data foundation for subsequent equipment health status diagnosis.

[0162] In some embodiments, the data processing module 1 is further configured to: calculate the difference between the falling edge time of the reference pulse of the reference pulse sensing signal and the falling edge time of the measurement pulse of the pulse measurement laser, and obtain the internal flight time of the system.

[0163] The timing unit (TDC) inside data processing module 1 is configured to accurately capture the falling edge of the pulse signal. When the laser drive pulse (i.e., the drive signal of the "pulse measurement laser") emitted by data processing module 1 ends and its voltage jumps from high level back to low level, the TDC immediately records this moment as the "falling edge time of the measurement pulse". This marks the end of one emission event within the system.

[0164] Subsequently, after the reference pulse signal returned through the internal optical path is processed by the reference receiver, its falling edge (high-to-low transition) is also captured by the TDC and recorded as the "reference pulse falling edge time". Finally, the data processing module 1 calculates the difference between these two falling edge timestamps (i.e., "reference pulse falling edge time" - "measured pulse falling edge time") to obtain a "system internal flight time" based on the pulse end point.

[0165] The unique feature of this method is that it not only reflects the signal propagation delay but is also extremely sensitive to changes in pulse width. By comparing this internal flight time, calculated based on the falling edge, with the flight time previously calculated based on the rising edge, the system can obtain deeper diagnostic information. For example, it can distinguish whether the pulse waveform broadening or narrowing is due to a simple change in signal transmission delay or component aging, thus achieving more refined and comprehensive monitoring of equipment health status.

[0166] like Figure 3 The image shows the software interface of the system in this embodiment, which displays the distance measurement results of the distance measurement system in this embodiment. Figure 3 This strongly demonstrates that the present embodiment achieves excellent measurement accuracy and stability, effectively controlling ranging fluctuations within 1 mm, and achieving millimeter-level ranging accuracy.

[0167] Figure 3 In the diagram, the reference signal represents the reference pulse sensing signal, and the target signal represents the main pulse sensing signal. In the real-time distance data graph, the x-axis represents the number of measurements, and the y-axis represents the measured distance value in millimeters. In the reference signal attenuation rate and target signal attenuation rate data graphs, the x-axis represents the number of measurements, and the y-axis represents the signal energy value; this value is a software-internal conversion result and has no unit. Figure 3As can be clearly observed, all data points are tightly clustered around a horizontal center line, with their fluctuation range (peak-to-peak value) distributed within an extremely narrow interval of ±0.5 mm, meaning the total fluctuation is less than 1 mm. This extremely low data dispersion intuitively demonstrates that this technical solution effectively suppresses environmental drift through a differential hedging architecture and eliminates errors caused by different reflectivities through precise walking error calibration.

[0168] Specifically, in Figure 3 During the test, the ranging value fluctuated between 1583.0 mm and 1583.4 mm. The software interface clearly indicated that the current value was 1583.2 mm, with a maximum deviation of only 0.4 mm (i.e., the difference between the maximum value of 1583.4 mm and the minimum value of 1583.0 mm). This 0.4 mm deviation clearly demonstrates that the maximum fluctuation of the ranging result was strictly controlled within 0.4 mm during the continuous monitoring period, far below the technical target of 1 mm. This definitively verifies the technical effect of achieving millimeter-level (more precisely, sub-millimeter-level) accuracy in this embodiment.

[0169] at the same time, Figure 3 This also powerfully demonstrates the core advantage of the differential hedging architecture in this embodiment, namely, that it effectively immunizes against signal fluctuations caused by environmental factors through an internal reference signal, thereby ensuring the measurement stability of the system. Figure 3 In the diagram, the data graphs of the reference signal attenuation rate and the target signal attenuation rate clearly show two curves: the upper curve represents the internal reference signal with constant energy, whose value remains almost a perfect straight line throughout the measurement process, verifying the extreme stability of the reference optical path; while the lower curve, representing the external target signal, exhibits obvious fluctuations. This contrast vividly reveals a key fact: although the main measurement signal inevitably fluctuates due to environmental disturbances, minor target vibrations, or normal fluctuations in the laser's output energy, the reference benchmark established internally in this embodiment remains stable. By using the difference or ratio between the main signal and this stable reference signal in subsequent calculations, the system can effectively offset the "common-mode" fluctuation component in the target signal, ultimately extracting pure time-of-flight information that is only related to distance. This is one of the fundamental reasons why this embodiment can achieve high stability and high-precision ranging.

[0170] This invention provides a groundbreaking solution that combines high precision, low cost, and high practicality, addressing the inherent shortcomings of existing high-precision phase-based ranging and traditional TOF ranging.

[0171] Compared to the traditional phase method, this embodiment is based on the time-of-flight (TOF) principle. It does not require complex phase unwinding algorithms, nor does it rely on expensive, high-power, high-speed, high-resolution ADCs. Instead, it achieves time measurement through sophisticated analog circuit design and a cost-effective FPGA or MCU in conjunction with a dedicated TDC chip. This significantly reduces hardware costs and system power consumption, and allows the product to achieve a smaller physical size.

[0172] More importantly, the dual-path differential architecture of this embodiment fundamentally solves the core bottleneck of achieving high precision in traditional TOF technology, namely electronic device drift. Its resistance to environmental interference is far superior to that of the phase method, which is sensitive to atmospheric parameters, thus achieving the goal of "simple production and convenient debugging".

[0173] Compared to traditional TOF technology, which can only achieve centimeter-level accuracy, this embodiment successfully improves the ranging accuracy to the millimeter level through the dual protection of "differential offsetting" and "walking error calibration," achieving an accuracy level comparable to or even surpassing that of the phase method. At the same time, it retains the natural advantages of TOF technology in long-distance measurement, such as ambiguity-free range and fast response speed.

[0174] In summary, the embodiments of the present invention cleverly integrate the cost and distance advantages of TOF technology, and overcome its accuracy shortcomings with an innovative architecture, ultimately achieving an ideal technical form that realizes long-distance millimeter-level high-precision measurement with significant advantages in multiple dimensions such as accuracy, cost, size, reliability and ease of production.

[0175] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A time-of-flight (TOF) based laser ranging system, characterized in that, It includes a data processing module, a laser emission module, a beam splitter, a reflector, a reference receiving module, and a main receiving module; The laser emitting module is used to emit pulse measurement lasers; The beam splitter is positioned in the light emission direction of the laser emitting module to split the pulse measurement laser into a reference measurement laser and a main measurement laser. The reference measurement laser is directed toward the reflector, and the main measurement laser is directed toward the target being measured. The reflector is used to reflect the reference measurement laser to the reference receiving module; The reference receiving module is used to receive the reference measurement laser and generate a reference pulse sensing signal; The main receiving module is used to receive the main measuring laser reflected back from the target under test and generate a main pulse sensing signal. The circuits of the main receiving module and the reference receiving module are the same or symmetrical. The data processing module is connected to both the reference receiving module and the main receiving module, and is used for: The initial differential flight time is determined based on the timestamp information of the main pulse sensing signal and the reference pulse sensing signal; Determining the walking error parameter based on the pulse width of the main pulse sensing signal includes: calculating the pulse width ratio of the main pulse sensing signal to the pulse width of the reference pulse sensing signal or the pulse measurement laser; and determining the walking error parameter corresponding to the pulse width ratio based on a preset pulse width ratio-walking error correspondence. Based on the initial differential flight time and the walking error parameters, a calibration flight time is generated; Based on the calibrated flight time and the speed of light, the calibrated ranging result of the target is calculated. By constructing a walking error calibration function to simulate the correspondence between pulse width ratio and walking error, the mathematical expression of the walking error calibration function is as follows: Where, ΔT walk R represents the time correction amount for the walking error; R is the independent variable of the function, representing the pulse width ratio of the real-time measurement; A represents the saturation error amplitude; R0 represents the static operating point ratio; R μ Represents the resonant center ratio; α represents the saturation sensitivity factor; B represents the resonant coupling coefficient; σ represents the resonant bandwidth; T offset This indicates the static time offset.

2. The system according to claim 1, characterized in that, The timestamp information of the main pulse sensing signal includes the rise time of the main pulse, and the timestamp information of the reference pulse sensing signal includes the rise time of the reference pulse. The data processing module is specifically used to calculate the time difference between the rising edge time of the main pulse and the rising edge time of the reference pulse to obtain the initial differential flight time.

3. The system according to any one of claims 1-2, characterized in that, The incident angle of the pulse measurement laser on the beam splitter is 45°, and the incident angle of the reference measurement laser on the mirror surface of the reflector is 45°.

4. The system according to claim 1, characterized in that, The energy of the master measuring laser is greater than the energy of the reference measuring laser.

5. The system according to claim 4, characterized in that, The energy of the main measurement laser accounts for 90% to 99% of the energy of the pulse measurement laser, and the energy of the reference measurement laser accounts for 1% to 10% of the energy of the pulse measurement laser.

6. The system according to claim 1, characterized in that, The data processing module is also used for: The internal flight time of the system is determined based on the timestamp information of the reference pulse sensing signal and the pulse measurement laser. The health status of the equipment is determined based on the internal flight time of the system.

7. The system according to claim 6, characterized in that, The data processing module is also used to: calculate the difference between the rise time of the reference pulse of the reference pulse sensing signal and the rise time of the measurement pulse of the pulse measurement laser, and obtain the internal flight time of the system.

8. The system according to claim 6, characterized in that, The data processing module is also used to: calculate the difference between the falling edge time of the reference pulse of the reference pulse sensing signal and the falling edge time of the measurement pulse of the pulse measurement laser, and obtain the internal flight time of the system.

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