Multi-channel staggered sampling SPAD module

Abstract

The utility model provides a multichannel staggered sampling SPAD module which is arranged in a laser radar and serves as a receiving module of a machine radar, an MCU is arranged in a laser tool, the MCU is provided with an MCU interface, and the multichannel staggered sampling SPAD module comprises an SPAD unit, a TDC circuit array, a signal processing circuit and a coding circuit; wherein the work cycles of the TDC circuits in the TDC circuit array are sequentially arranged in a staggered manner, so that time of the SPAD units is sampled in a staggered manner, a delay chain is formed, the TDC circuit array can output a second value once every a fixed time length, and the fixed time length is smaller than the work cycle of one TDC circuit. After the technical scheme is adopted, the upper limit of the signal transmission rate can be greatly improved, so that the sampling efficiency is improved, and stronger scanning performance is realized.

Description

Technical Field

[0001] This utility model relates to the field of lidar, and in particular to a SPAD module with multi-channel interleaved sampling. Background Technology

[0002] Due to its unique switching operation, the SPAD module commonly used in existing lidar requires the TDC channel to operate through multiple integration statistics or histogram statistics. Furthermore, the SPAD module of existing lidar has a single built-in TDC channel, which makes it difficult to exceed 5KHz in terms of maximum data output rate. Utility Model Content

[0003] A multi-channel interleaved sampling SPAD module is installed inside a lidar system as a receiving module for the lidar. The lidar system contains an MCU with an MCU interface. The multi-channel interleaved sampling SPAD module includes a SPAD unit, a TDC circuit array, a signal processing circuit, and an encoding circuit. The SPAD bias generator is electrically connected to the SPAD unit to raise the system voltage to the voltage required for the SPAD unit to operate, enabling the SPAD unit to generate an avalanche effect when it receives photons.

[0004] The quenching circuit is electrically connected to the SPAD unit to pull down the voltage of the SPAD unit that is experiencing an avalanche, making it lower than the breakdown voltage of the SPAD unit, thereby interrupting the continued avalanche of the SPAD unit and allowing the SPAD unit to quickly return to its initial state, thereby controlling the emission current and emission time of the SPAD unit.

[0005] The SPAD unit is electrically connected to the TDC circuit array to receive the echo from the lidar. When the SPAD unit receives the echo, it generates a pulse and sends a TRIG signal and an LD synchronization signal to the TDC circuit array at a fixed frequency.

[0006] The TDC circuit array includes at least one TDC circuit, with each TDC circuit arranged in parallel. Each TDC independently samples the flight time of the pulses generated by the SPAD unit and processes it into a second value upon receiving the TRIG signal and LD synchronization signal. The period during which each TDC outputs a second value is one operating cycle of the TDC circuit, and the circuit operates cyclically according to this operating cycle. The operating cycles of the TDC circuits in the TDC circuit array are sequentially interleaved, thereby interleaving the sampling time of the SPAD unit and forming a delay chain. This allows the TDC circuit array to output a second value at fixed intervals, where the fixed interval is less than the operating cycle of one TDC circuit.

[0007] The signal processing circuit and the encoding circuit are electrically connected to the TDC circuit array and connected to the MCU interface via a bus. The signal processing circuit and the encoding circuit acquire the second value of the TDC circuit array, convert the second value into a distance value, and transmit the distance value to the MCU for further processing.

[0008] Preferably, each TDC circuit in the TDC circuit array is sequentially provided with an initial delay, so that the working cycles of each TDC circuit in the TDC circuit array are sequentially interleaved to form a delay chain, so that the TDC circuit array can output a second value once every fixed time interval, and the fixed time interval is less than the working cycle of one TDC circuit.

[0009] Preferably, the initial delay is set as follows: the TDC circuit array includes n TDC circuits, sequentially numbered from the first TDC circuit to the nth TDC circuit, where n ≥ 2. The working cycle of each TDC circuit is m TRIG signals. The initial delay of the first TDC circuit is set to 0. Subsequently, each TDC circuit is extended by m / n TRIG signals compared to the previous TDC circuit. Thus, the time difference between the working cycles of any two adjacent TDC circuits is m / n TRIG signals, and the time difference between the working cycle of the first TDC circuit and the previous working cycle of the nth TDC circuit is also m / n TRIG signals, forming a delay chain. This allows the TDC circuit array to output a second value every fixed interval, where the fixed interval is less than the working cycle of one TDC circuit.

[0010] Optionally, a window period is set after the working cycle of each TDC circuit in the TDC circuit array, and the window period is determined based on the pulse flight time and the number of TDC circuits in the TDC circuit array.

[0011] Optionally, the SPAD unit is a SPAD array consisting of at least one SPAD diode arranged uniformly.

[0012] Optionally, the bus is an SPI bus or an IIC bus. Attached Figure Description

[0013] Figure 1 A circuit block diagram of a SPAD module with multi-channel interleaved sampling;

[0014] Figure 2 This is a Gantt chart of the duty cycle for one embodiment of a TDC circuit array. Detailed Implementation

[0015] The advantages of this disclosure are further illustrated below with reference to the accompanying drawings and specific embodiments.

[0016] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0017] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0018] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0019] In the description of this disclosure, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0020] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0021] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0022] See Figure 1 The multi-channel interleaved sampling SPAD module provided by this invention is installed inside a lidar system as a receiving module. The lidar tool also contains an MCU with an MCU interface.

[0023] The multi-channel interleaved sampling SPAD module includes a SPAD unit, a SPAD bias generator, a quenching circuit, a TDC circuit array, a signal processing module, and an encoding circuit.

[0024] The SPAD bias generator is electrically connected to the SPAD unit to raise the system voltage to the voltage required for the SPAD unit to operate, so that the SPAD unit can generate an avalanche effect when it receives photons.

[0025] The quenching circuit is electrically connected to the SPAD unit to pull down the voltage of the SPAD unit that is experiencing an avalanche, making it lower than the breakdown voltage of the SPAD unit, interrupting the continued avalanche of the SPAD unit and allowing the SPAD unit to quickly return to its initial state, thereby controlling the emission current and emission time of the SPAD unit.

[0026] The SPAD unit is a SPAD array consisting of at least one SPAD diode evenly arranged to receive the echo from the lidar. The SPAD unit is electrically connected to the TDC circuit array. When the SPAD unit receives the echo, it generates a pulse and sends a TRIG signal and an LD synchronization signal to the TDC circuit array at a fixed frequency.

[0027] The TDC circuit array comprises several TDC circuits arranged in parallel. Each TDC circuit independently samples the flight time of the pulses generated by the SPAD unit and converts it into a digital signal upon receiving the TRIG signal and LD synchronization signal. It then collects data from the digital signal using histogram statistics to form histogram data. The peak values ​​in the histogram data are analyzed and located, and the peak position or center positioning time is calculated to obtain the second value. The period during which each TDC circuit obtains a second value using the above steps constitutes one operating cycle of the TDC circuit.

[0028] In another embodiment, the TDC circuits of the TDC circuit array acquire data through integral statistics.

[0029] The signal processing encoding circuit is electrically connected to the TDC circuit array and connected to the MCU interface of the MCU via the SPI bus. It is used to process the second value obtained by the TDC circuit array, convert it into the corresponding distance value, and upload the obtained distance value to the MCU via the SPI bus.

[0030] The MCU receives the distance value uploaded by the signal processing encoding circuit for further processing.

[0031] In another embodiment, the signal processing encoding circuit is connected to the MCU interface of the MCU via the IIC bus.

[0032] By setting different initial delays for each TDC circuit in sequence, the working cycles of each TDC circuit are interleaved, so that the TDC circuit array can form a delay chain and realize the time-interleaved sampling of the SPAD unit by the TDC circuit array.

[0033] The specific method for setting the initial delay is as follows:

[0034] exist Figure 1 Based on, combined Figure 2 The TDC circuit array includes n TDC circuits, designated as the first to the nth TDC circuits, where the number of TDC circuits n ≥ 2. Each TDC circuit samples and acquires data from the SPAD unit once upon receiving a TRIG signal. After receiving m TRIG signals and performing m sampling and data acquisitions on the SPAD unit, the acquired data is analyzed to derive and output the second value. The TDC circuits then operate in a cyclical manner. The measurement rate of each TDC circuit after initially analyzing and outputting the second value is a (Hz).

[0035] The initial delay of the first TDC circuit is set to 0. Subsequently, the initial delay of each TDC circuit is extended by m / n times compared to the previous TDC circuit.

[0036] For example, the first TDC circuit operates in a cycle according to the above working cycle starting from receiving the first TRIG signal; the second TDC circuit operates in a cycle according to the above working cycle starting from receiving the m / n+1th TRIG pulse signal; the third TDC circuit operates in a cycle according to the above working cycle starting from receiving the 2m / n+1th TRIG signal; and the nth TDC circuit operates in a cycle according to the above working cycle starting from receiving the (n-1)m / n+1th TRIG signal.

[0037] The working cycles of the first to the nth TDC circuits are interleaved sequentially. The time difference between the working cycles of each two adjacent TDC circuits is m / n times the TRIG signal, and the time difference between the working cycle of the first TDC circuit and the previous working cycle of the nth TDC circuit is also m / n times the TRIG signal. Thus, the TDC circuit array forms a delay chain, realizing the time-interleaved operation of the TDC circuit array, and can output a second value every m / n times the TRIG signal.

[0038] The time-interleaved sampling and data acquisition of the SPAD unit by the TDC circuit array composed of n TDC circuits implemented by the above method has a measurement rate of n·a (Hz) after the second value is obtained and output at the beginning of the analysis. Compared with the single TDC circuit for the SPAD unit, the measurement rate of the interleaved sampling by the TDC circuit array composed of multiple TDC circuits can be greatly improved.

[0039] Optionally, a window period is set after the working cycle of each TDC circuit, and the window period is determined based on the pulse flight time and the number of TDC circuits in the TDC circuit array.

[0040] In one embodiment, the SPAD unit transmits signals at a frequency of 1MHz. The TDC circuit array has four TDC circuits: a first TDC circuit, a second TDC circuit, a third TDC circuit, and a fourth TDC circuit. Each TDC circuit samples and acquires data from the SPAD unit once upon receiving a TRIG signal. After repeating this sampling and data acquisition process 150 times, the circuit analyzes the data and outputs a second value. The measurement rate of each TDC circuit after it begins analyzing and outputting the second value is 5kHz.

[0041] The first TDC circuit starts sampling and acquiring data from the SPAD unit from the first TRIG signal received. When the 200th TRIG signal is received, it analyzes and outputs the second value for the first time. Then, it starts sampling and acquiring data from the 201st TRIG signal received. When the 400th TRIG signal is received, it analyzes and outputs the second value for the second time. The first TDC circuit then works in this manner in a cycle.

[0042] The second TDC circuit starts sampling and acquiring data from the SPAD unit from the 51st TRIG pulse. When the 250th TRIG signal is received, it analyzes and outputs the second value for the first time. Then, it starts sampling and acquiring data from the 251st TRIG signal for the second time. When the 450th TRIG signal is received, it analyzes and outputs the second value for the second time. The second TDC circuit then works in this manner in a cycle.

[0043] The third TDC circuit starts sampling and acquiring data from the SPAD unit from the 101st TRIG signal. When the 300th TRIG signal is received, it analyzes and outputs the second value for the first time. Then, it starts sampling and acquiring data from the 301st TRIG signal. When the 500th TRIG signal is received, it analyzes and outputs the second value for the second time. The third TDC circuit then works in this manner in a cycle.

[0044] The fourth TDC circuit starts sampling and acquiring data from the SPAD unit from the 151st TRIG signal. When the 350th TRIG signal is received, it analyzes and outputs the second value for the first time. Then, it starts sampling and acquiring data from the 351st TRIG signal. When the 550th TRIG signal is received, it analyzes and outputs the second value for the second time. The fourth TDC circuit then works in this manner in a cycle.

[0045] The operating cycles of the first to fourth TDC circuits are interleaved sequentially, and the time difference between the operating cycles of any two adjacent TDC circuits, as well as between the first and fourth TDC circuits, is 50 TRIG signals. This creates a delay chain in the TDC circuit array, enabling time-interleaved sampling of the SPAD units by the TDC circuit array. The measurement rate of the TDC circuit array, composed of four TDC circuits, after obtaining and outputting the second value at the start of analysis, is 20 kHz.

[0046] Using the lidar receiving system provided by this invention, the upper limit of signal transmission rate can be significantly increased, thereby improving sampling efficiency and achieving stronger scanning performance.

[0047] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A multi-channel interleaved sampling SPAD module, disposed within a lidar as a receiving module of the lidar, wherein the lidar contains an MCU and the MCU has an MCU interface; Its features are, It includes a SPAD bias generator, a quenching circuit, a SPAD unit, a TDC circuit array, a signal processing circuit, and an encoding circuit; The SPAD bias generator is electrically connected to the SPAD unit to pull the system voltage up to the voltage required for the SPAD unit to operate, so that the SPAD unit generates an avalanche effect when it receives photons. The quenching circuit is electrically connected to the SPAD unit to pull down the voltage of the SPAD unit that is experiencing an avalanche, making it lower than the breakdown voltage of the SPAD unit, thereby interrupting the continued avalanche of the SPAD unit and allowing the SPAD unit to quickly return to its initial state, thereby controlling the emission current and emission time of the SPAD unit. The SPAD unit is electrically connected to the TDC circuit array to receive the echo from the lidar; when the SPAD unit receives the echo, it generates a pulse and sends a TRIG signal and an LD synchronization signal to the TDC circuit array at a fixed frequency. The TDC circuit array includes at least one TDC circuit, with each TDC circuit arranged in parallel. Each TDC independently samples the flight time of the pulse generated by the SPAD unit and processes it into a second value when it receives the TRIG signal and LD synchronization signal. The period during which each TDC obtains a second value is one working cycle of the TDC circuit, and it operates cyclically according to the working cycle. The working cycles of each TDC circuit in the TDC circuit array are sequentially interleaved, thereby interleaving the sampling time of the SPAD unit to form a delay chain, so that the TDC circuit array can output a second value once every fixed time interval, and the fixed time interval is less than the working cycle of one TDC circuit. The signal processing circuit and the encoding circuit are electrically connected to the TDC circuit array and connected to the MCU interface via a bus. The signal processing circuit and the encoding circuit acquire the second value of the TDC circuit array, convert the second value into a distance value, and transmit the distance value to the MCU for further processing.

2. The SPAD module with multi-channel interleaved sampling as described in claim 1, characterized in that, The SPAD unit is a SPAD array consisting of at least one SPAD diode arranged uniformly.

3. The SPAD module with multi-channel interleaved sampling as described in claim 1, characterized in that, The bus is either an SPI bus or an IIC bus.

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