Fast adaptive laser ranging system and method based on silicon photomultiplier

Abstract

The application discloses a kind of fast adaptive laser ranging system and method based on silicon photomultiplier, data processing module start timing control circuit, drive pulse laser transmitter generates laser, and is shaped by transmitting lens assembly, irradiates to measured object, time digital conversion module synchronous start timing;Echo light signal is received by receiving lens assembly and is evenly distributed in silicon photomultiplier receiving surface by diaphragm, carries out photoelectric conversion, and then signal is amplified by amplifying circuit;Signal processing module measures background light intensity in real time as threshold voltage output to comparator, is shaped and discriminated by comparator, obtains effective signal and is transmitted to time digital conversion module while ending timing;By comparing the time delay between start timing signal and end timing signal, the target distance position is obtained.The application can sufficiently reduce the influence of background light, quickly collect distance information, and keep the overvoltage of silicon photomultiplier constant by automatic voltage adjustment.

Description

Technical Field

[0001] This invention belongs to the field of lidar detection technology, and in particular relates to a fast adaptive laser ranging system and method based on silicon photomultiplier tubes. Background Technology

[0002] Laser ranging technology is based on the excellent directionality and monochromaticity of lasers. It boasts advantages such as high precision, long transmission distance, and fast propagation speed, and has been widely used in both civilian and military fields. In laser ranging systems, because the echo signal intensity to be received is relatively weak, traditional optical detectors cannot detect weak light signals, necessitating the use of detectors with single-photon precision to receive the signal.

[0003] Silicon photomultiplier tubes (SiPMs) are a novel type of high-performance semiconductor photodetector. They consist of an array of multiple pixels operating in Geiger mode connected in parallel, with each pixel composed of an avalanche photodiode and a quenching resistor connected in series. SiPMs possess characteristics such as single-photon level sensitivity, excellent photon counting capability, and picosecond-level high-speed response. Because a SiPM consists of thousands of avalanche photodiodes, its detection surface is large, allowing it to respond to a large number of photons at a time. Therefore, it is necessary to expand the signal incident surface to fully utilize the detection performance of the SiPM. Furthermore, due to its high sensitivity, the influence of background light needs to be controlled. Additionally, SiPMs are susceptible to temperature-related errors, requiring real-time overvoltage control to ensure accuracy during practical operation. SiPM-based laser ranging systems can perform real-time measurements while improving system sensitivity and simplifying the system, which is of great significance for lidar applications.

[0004] Currently, silicon photomultiplier tubes (SMTs) have been used as detectors in laser ranging systems both domestically and internationally. However, due to the large detection area and numerous pixels of SMTs, existing technologies have not fully utilized their detection capabilities. Furthermore, because SMTs are highly sensitive and easily affected by background light, no laser ranging system with adaptive threshold adjustment based on SMTs has yet been designed. Summary of the Invention

[0005] The purpose of this invention is to solve the problems that existing ranging systems cannot fully utilize the large detection surface of silicon photomultiplier tubes and are easily affected by background light, making it impossible to adjust the threshold voltage in real time according to changes in background light.

[0006] To achieve the objectives of this invention, a fast adaptive laser ranging system based on a silicon photomultiplier tube is provided. The system includes a timing control circuit, a pulsed laser emitter, a transmitting lens assembly, a receiving lens assembly, an aperture, a silicon photomultiplier tube, an amplifier circuit, a signal processing module, a comparator, a data processing module, and a time-to-digital converter module. The data processing module activates the timing control circuit, which drives the pulsed laser emitter to generate laser light, which is then shaped by the transmitting lens assembly and projected onto the object being measured. Simultaneously, the timing control circuit provides a start-time signal to synchronize the timing with the time-to-digital converter module. After the laser reaches the target position, the echo signal is received by the receiving lens assembly and transmitted through… The echo light signal is evenly distributed on the receiving surface of the silicon photomultiplier tube (SMT) through the aperture. The SMT performs photoelectric conversion, and the signal is amplified by the amplifier circuit. The background light intensity is measured in real time by the signal processing module and output as a threshold voltage to the comparator. The signal is then shaped and discriminated by the comparator to obtain a valid signal, which is transmitted to the time-to-digital converter (TD-C) module and the timing ends. After the set detection cycle is completed, the distribution of photon events in all detection cycles is statistically analyzed based on the photon signal sequence collected within the cycle. By comparing the time delay between the start and end timing signals of the TD-C module, the data is transmitted to the data processing module to obtain the target distance and position.

[0007] Furthermore, the operating temperature of the silicon photomultiplier tube is monitored in real time by a temperature sensor and the information is transmitted to a power module with temperature compensation function; the power module automatically adjusts the output voltage according to the temperature sensor to keep the silicon photomultiplier tube in a stable working state.

[0008] Furthermore, the signal processing module first calculates the output voltage of the silicon photomultiplier tube under no laser signal and adds it to the set rated voltage; then, the delay timer is set by the FPGA to retain the current voltage as a comparison voltage. When the silicon photomultiplier tube receives a pulse signal, it will compare it with the voltage at the previous moment, measure the light intensity in real time and use it as the threshold voltage; if the pulse signal received by the silicon photomultiplier tube is greater than the voltage at the previous moment, the timing end signal is transmitted to the time-to-digital converter module.

[0009] Furthermore, each pixel of the silicon photomultiplier tube is composed of a silicon avalanche photodiode (APD) operating in Geiger mode connected in series with a quenching resistor; several such pixels are connected in parallel to form a two-dimensional array structure, and share a power supply terminal and an output terminal.

[0010] Furthermore, the time-to-digital conversion module transmits the data to the data processing module via the SPI communication protocol to obtain the actual transmission distance.

[0011] To achieve the objectives of this invention, a fast adaptive laser ranging method based on a silicon photomultiplier tube is also disclosed, comprising the following steps:

[0012] Step 1: The timing control circuit is started through the data processing module. The timing control circuit drives the pulsed laser emitter to generate laser light, which is shaped by the emitting lens assembly and irradiated onto the object under test. At the same time, the timing control circuit gives a start timing signal to make the time-to-digital conversion module start timing synchronously.

[0013] Step 2: After the laser reaches the target position, the echo light signal is received by the receiving lens assembly and evenly distributed on the receiving surface of the silicon photomultiplier tube through the aperture. The silicon photomultiplier tube performs photoelectric conversion, and then the signal is amplified by the amplification circuit. The background light intensity is measured in real time by the signal processing module and output as the threshold voltage to the comparator. After that, the signal is shaped and discriminated by the comparator to obtain a valid signal and transmit it to the time-to-digital conversion module to end the timing.

[0014] Step 3: After the set detection cycle is completed, based on the photon signal sequence collected within the cycle, the distribution of photon events in all detection cycles is statistically analyzed. By comparing the time delay between the start and end timing signals of the time-to-digital converter, the data is transmitted to the data processing module to obtain the target distance and position.

[0015] Compared with the prior art, the significant advancements of this invention are: 1) The aperture is designed with its aperture located on the focal plane and having the same area as the focal plane. This design can significantly reduce the influence of background light, while ensuring that the echo signal is fully received; 2) The distance between the photosensitive surface and the aperture is calculated to ensure that the echo signal covers the photosensitive surface of the silicon photomultiplier tube after passing through the aperture. Since the silicon photomultiplier tube is formed by thousands of photodiodes connected in parallel, its receiving surface is large. This design allows the aperture to block background light while ensuring that the echo signal diffuses and completely covers the receiving surface of the silicon photomultiplier tube, fully utilizing the characteristics of the silicon photomultiplier tube; 3) The signal processing module is designed... The output voltage of the silicon photomultiplier tube is measured in real time. The current output voltage is superimposed with the set rated voltage by an adder as a comparison voltage. When the silicon photomultiplier tube receives a pulse signal, the output voltage of the silicon photomultiplier tube is compared with the superimposed output voltage of the previous moment due to the existence of the delay. This design enables the system to adaptively adjust in real time according to the change of background light. Moreover, due to the use of the comparison discrimination method, distance information can be quickly acquired. 4) A power supply module with temperature compensation function is used, and a temperature sensor is used to measure the operating temperature of the silicon photomultiplier tube in real time. The overvoltage of the silicon photomultiplier tube is kept constant by automatically adjusting the voltage.

[0016] To more clearly illustrate the functional characteristics and structural parameters of the present invention, further explanation is provided below in conjunction with the accompanying drawings and specific embodiments. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0018] Figure 1 This is a schematic diagram of a fast adaptive laser ranging system based on a silicon photomultiplier tube.

[0019] Figure 2 A schematic diagram of a silicon photomultiplier tube receiving an echo signal;

[0020] Figure 3 This is a schematic diagram of the signal processing module.

[0021] Figure 4 This is a flowchart illustrating a fast adaptive laser ranging method based on silicon photomultiplier tubes.

[0022] The attached diagram is labeled as follows: 1. Timing control circuit; 2. Pulsed laser emitter; 3. Emitting lens assembly; 4. Receiving lens assembly; 5. Aperture; 6. Silicon photomultiplier tube; 7. Amplifier circuit; 8. Signal processing module; 9. Comparator; 10. Power supply module; 11. Temperature sensor; 12. Data processing module; 13. Time-to-digital converter module. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] like Figure 1As shown, a fast adaptive laser ranging system based on silicon photomultiplier tubes includes a timing control circuit 1, a pulsed laser emitter 2, an emitting lens assembly 3, a receiving lens assembly 4, an aperture 5, a silicon photomultiplier tube 6, an amplifier circuit 7, a signal processing module 8, a comparator 9, a power supply module 10, a temperature sensor 11, a data processing module 12, and a time-to-digital converter module 13. The data processing module 12 is connected to the timing control circuit 1, used to store data and transmit pulse signals to control the operation of the entire system; the timing control circuit 1 controls the pulsed laser emitter 2 to emit pulsed laser signals and sends a start timing signal to the time-to-digital converter module; the transmitting lens assembly 3 significantly compresses the divergence angle and collimates the laser signal so that it is emitted onto the target object; the receiving lens assembly 4 is used to refocus the echo signal that has undergone diffuse reflection after reaching the target position onto the receiving surface of the silicon photomultiplier tube 6; the aperture 5 is used to block part of the background light and diffuse the light signal to the surface of the silicon photomultiplier tube 6; the silicon photomultiplier tube 6 is used to receive the laser echo signal and convert it into a current signal for subsequent processing; the amplifier circuit 7 is used to amplify the signal of the silicon photomultiplier tube 6. The transmitted weak current signal is converted into a larger voltage signal; comparator 9 is used to convert the amplified analog signal into a digital signal by setting different equivalent threshold voltages and send a stop timing signal to the time-to-digital converter module 13; signal processing module 8 is used to change the threshold voltage in real time according to the background light intensity; temperature sensor 11 obtains the real-time temperature of silicon photomultiplier tube 6 and transmits it to power module 10, so that power module 10 adjusts the voltage according to the temperature to keep silicon photomultiplier tube 6 in a stable working state; time-to-digital converter module 13 obtains the delay time by calculating the start timing signal and the stop timing signal; data processing module 12 communicates with time-to-digital converter module 13 through SPI, processes the data to obtain the actual transmission distance, and displays the distance through the relevant interface.

[0025] Specifically, in this embodiment, the power module 10 is a power module with temperature compensation function. Its specific operation is as follows: the temperature sensor 11 detects the ambient temperature of the silicon photomultiplier tube 6 and compares it with the reference source of the silicon photomultiplier tube 6. Specifically, the reference source is a reference voltage of 25V when the ambient temperature is 25℃. When the ambient temperature rises, the required breakdown voltage also increases, while when the operating voltage is constant, the overvoltage decreases, leading to a reduction in detection efficiency. Using the power module 10 with temperature compensation function, the silicon photomultiplier tube 6 maintains a constant overvoltage.

[0026] Specifically, in this embodiment, the pulsed laser emitter 3 is model RLD650005, the silicon photomultiplier tube 6 is model JSP-TP3050-SMT, the amplifier circuit 7 is model OPA657, the power supply module 10 is model LM2733, the comparator 9 is model MAX999, the data processing module 12 is model STM32F103CBT6, and the time-to-digital converter module 13 is model TDC-GP22.

[0027] Specifically, in this embodiment, each pixel of the silicon photomultiplier tube 6 is composed of multiple pixels operating in Geiger mode connected in parallel, and each pixel is composed of an avalanche diode and a quenching resistor connected in series.

[0028] like Figure 2 As shown, the echo signal is received by the receiving lens assembly 4, and the light signal gradually converges to a focal plane. The aperture 5 of this system is designed to match the diameter of the focal plane, filtering out background light noise as much as possible. Since the receiving surface of the silicon photomultiplier tube 6 is relatively large, the aperture 5 designed in this system extends the distance between the focal plane and the silicon photomultiplier tube 6, allowing the echo light signal to diffuse and be fully incident on the photosensitive surface of the silicon photomultiplier tube 6 (SiPM), thus fully utilizing the detection performance of the SiPM. The diameter of the focal plane is:

[0029]

[0030] In the formula, u is the detection distance, and R is the distance between the two points. T Let f be the aperture diameter and f be the focal length of the system. The diameter R of the focal plane can be calculated using this formula, and the thickness of the aperture can be calculated using the size of the detection surface of the silicon photomultiplier tube.

[0031] like Figure 3 As shown, the signal processing module first calculates the output voltage of the silicon photomultiplier tube under no laser signal and superimposes it with the set rated voltage. The current voltage is retained as a comparison voltage by setting a delay unit through the FPGA. When the silicon photomultiplier tube receives a pulse signal, it will compare it with the voltage at the previous moment. Through this module, the light intensity can be measured in real time and used as a threshold voltage to realize the adaptive light intensity function of this system.

[0032] like Figure 4 As shown, a fast adaptive laser ranging method based on silicon photomultiplier tubes includes the following steps:

[0033] Step 1: The timing control circuit is started through the data processing module. The timing control circuit drives the pulsed laser emitter to generate laser light that is emitted to the target surface. At the same time, the digital conversion module starts timing synchronously.

[0034] Step 2: After the laser reaches the target position, the receiving lens assembly receives the echo light signal and transmits it to the silicon photomultiplier tube through the aperture. The silicon photomultiplier tube receives and processes the signal into a voltage signal, which is compared with the output voltage of the background light noise obtained by the signal processing module. When a valid signal is obtained, it is transmitted to the time value conversion module.

[0035] Step 3: After completing the set detection cycle, the distribution of photon events in all detection cycles is statistically analyzed. The data is obtained through the time-to-digital conversion module and transmitted to the data processing module to obtain the target distance and position.

[0036] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0037] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A fast adaptive laser ranging system based on a silicon photomultiplier tube, characterized in that, The system includes a timing control circuit, a pulsed laser emitter, a transmitting lens assembly, a receiving lens assembly, an aperture, a silicon photomultiplier tube, an amplifier circuit, a signal processing module, a comparator, a data processing module, and a time-to-digital converter module. The data processing module activates the timing control circuit, which drives the pulsed laser emitter to generate laser light, which is then shaped by the transmitting lens assembly and projected onto the object being measured. Simultaneously, the timing control circuit provides a start timing signal to synchronize with the time-to-digital converter module. After the laser reaches the target position, the echo signal is received by the receiving lens assembly and evenly distributed across the silicon photomultiplier tube via the aperture. On the receiving surface of the photomultiplier tube, a silicon photomultiplier tube performs photoelectric conversion, and then the signal is amplified by an amplifier circuit. The signal processing module measures the background light intensity in real time and outputs it as a threshold voltage to a comparator. The signal is then shaped and discriminated by the comparator to obtain a valid signal, which is transmitted to the time-to-digital converter module and the timing ends. After the set detection cycle is completed, the distribution of photon events in all detection cycles is statistically analyzed based on the photon signal sequence collected within the cycle. By comparing the time delay between the start and end timing signals of the time-to-digital converter module, the data is transmitted to the data processing module to obtain the target distance and position. The operating temperature of the silicon photomultiplier tube is monitored in real time by a temperature sensor and the information is transmitted to a power module with temperature compensation function. The power module automatically adjusts the output voltage based on the temperature sensor, ensuring that the silicon photomultiplier tube is in a stable working state. The signal processing module first calculates the output voltage of the silicon photomultiplier tube under no laser signal and adds it to the set rated voltage. Then, the delay timer set by the FPGA retains the current voltage as a comparison voltage. When the silicon photomultiplier tube receives a pulse signal, it compares it with the voltage at the previous moment, measures the light intensity in real time and uses it as the threshold voltage. If the pulse signal received by the silicon photomultiplier tube is greater than the voltage at the previous moment, it transmits the end timing signal to the time-to-digital converter module. Each pixel of the silicon photomultiplier tube is composed of a silicon avalanche photodiode (APD) operating in Geiger mode connected in series with a quenching resistor; several such pixels are connected in parallel to form a two-dimensional array structure, and share a power supply terminal and an output terminal.

2. The fast adaptive laser ranging system based on a silicon photomultiplier tube according to claim 1, characterized in that, The time-to-digital conversion module transmits data to the data processing module via the SPI communication protocol to obtain the actual transmission distance.

3. A fast adaptive laser ranging method based on a silicon photomultiplier tube, the method being based on a fast adaptive laser ranging system based on a silicon photomultiplier tube as described in any one of claims 1-2, characterized in that, Includes the following steps: Step 1: The timing control circuit is started through the data processing module. The timing control circuit drives the pulsed laser emitter to generate laser light, which is shaped by the emitting lens assembly and irradiated onto the object under test. At the same time, the timing control circuit gives a start timing signal to make the time-to-digital conversion module start timing synchronously. Step 2: After the laser reaches the target position, the echo light signal is received by the receiving lens assembly and evenly distributed on the receiving surface of the silicon photomultiplier tube through the aperture. The silicon photomultiplier tube performs photoelectric conversion, and then the signal is amplified by the amplification circuit. The background light intensity is measured in real time by the signal processing module and output as the threshold voltage to the comparator. After that, the signal is shaped and discriminated by the comparator to obtain a valid signal and transmit it to the time-to-digital conversion module to end the timing. Step 3: After the set detection cycle is completed, based on the photon signal sequence collected within the cycle, the distribution of photon events in all detection cycles is statistically analyzed. By comparing the time delay between the start and end timing signals of the time-to-digital converter, the data is transmitted to the data processing module to obtain the target distance and position.

Images