Multistage system synchronous triggering device and method based on laser pulse

Abstract

The invention relates to the technical field of precise time synchronization and trigger control, in particular to a multistage system synchronous trigger device and method based on laser pulses. The multistage system synchronous triggering device based on the laser pulse comprises a photoelectric detection module used for receiving the laser pulse and converting the laser pulse into an initial electric signal; the constant fraction timing module is connected with the photoelectric detection module and used for extracting a zero crossing point irrelevant to the laser pulse amplitude from the initial electric signal, taking the triggering moment of the zero crossing point as a time zero point and outputting a reference triggering signal corresponding to the time zero point; and the trigger signal distribution module is connected with the constant fraction timing module and is used for distributing the reference trigger signal to a plurality of back-stage devices, so that the trigger time of each back-stage device is traced to the time zero point.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of precise time synchronization and trigger control, and particularly relates to a multi-stage system synchronization trigger device and method based on laser pulses. BACKGROUND

[0002] In ultrafast scientific experiments and high-speed measurement systems, multiple downstream devices (such as high-speed cameras, oscilloscopes, data acquisition cards, time-to-digital converters, and gated detectors) need to be triggered synchronously at the precise moment of laser pulse generation to ensure the time correlation of measurement signals and the overall accuracy of the system. The existing technology mainly uses the following synchronization schemes: External clock synchronization: a unified external clock source or signal generator is used to provide clock or trigger reference for the laser and all downstream devices. The fundamental defect of this method is that the optical oscillation, Q-switching, mode-locking or frequency doubling process inside the laser will introduce unpredictable timing jitter, resulting in an uncertain and time-drifting delay between the actual output laser pulse and the external electrical clock, making it difficult to achieve strict alignment at the picosecond to nanosecond level.

[0003] Laser gate signal trigger: use the gate or ready electrical signal generated inside the laser to trigger downstream devices. As shown in FIG. 1, this method is directly related to the state of the laser, but the electrical signal usually corresponds to the "ready to discharge" or "cavity empty" event of the laser, not the "output" event of the final laser pulse, and there is a fixed or variable delay between the two, with limited accuracy. Figure 6 Fixed threshold trigger: convert the laser pulse into an electrical signal through a photodetector, and then use a comparator to set a fixed voltage threshold to extract the trigger time. As shown in FIG. 2, the amplitude and rising edge of the electrical signal will change due to fluctuations in laser pulse energy, mode instability, or changes in the optical path. Fixed threshold triggering is extremely sensitive to amplitude fluctuations, resulting in significant "time walk", i.e., the trigger time shifts back and forth with changes in pulse amplitude, severely damaging the stability and repeatability of the timing.

[0004] Figure 2

[0005] In summary, the existing technical solutions cannot fundamentally solve the synchronization requirement of using the laser pulse output event itself as the only and stable time reference. When multiple devices are triggered in parallel, signal reflection and impedance mismatch will introduce additional jitter; the electrical response delays of different devices are different, further causing the action time of each channel to be dispersed. SUMMARY

[0006] ​​The technical problem solved by the present application is to overcome the defects of time drift, trigger misalignment and insufficient synchronization accuracy caused by laser pulse amplitude fluctuation, external clock mismatch and inconsistent multi-channel distribution in the existing synchronization scheme.

[0007] To solve the above technical problems, the present application provides a multi-stage system synchronization trigger device and method based on laser pulse, which no longer attempts to synchronize the laser with an external clock, but directly takes the detected laser pulse event as the absolute time starting point (time zero point), and through precise timing and distribution technology, the trigger time of all subsequent devices is accurately traced back to this zero point.

[0008] To achieve the above purpose, the present application adopts the following technical solutions: On the one hand, the present application provides a multi-stage system synchronization trigger device based on laser pulse, comprising: a photoelectric detection module for receiving laser pulses and converting them into initial electrical signals; a constant fraction timing module connected with the photoelectric detection module, for extracting a zero-crossing point irrelevant to the laser pulse amplitude from the initial electrical signals, taking the trigger time of the zero-crossing point as the time zero point, and outputting a reference trigger signal corresponding to the time zero point; a trigger signal distribution module connected with the constant fraction timing module, for distributing the reference trigger signal to multiple subsequent devices, so that the trigger time of each subsequent device is traced back to the time zero point.

[0009] Preferably, the trigger signal distribution module comprises: a fan-out buffer unit for distributing the reference trigger signal into multiple trigger signals; a delay compensation unit provided on the output channel of at least one trigger signal, for adjusting the transmission delay of at least one trigger signal to compensate for the response time difference between the corresponding subsequent device and the time zero point.

[0010] Preferably, the trigger signal distribution module further comprises an impedance matching network connected to the multiple output channels of the fan-out buffer unit, for matching the impedance of each output channel with the input impedance of the corresponding subsequent device.

[0011] Preferably, the delay compensation unit comprises at least one of a digital delay chip or a delay control logic based on a field programmable gate array (FPGA).

[0012] Preferably, the delay compensation unit and the fan-out buffer unit can be integrated in the same field programmable gate array (FPGA) to simplify the design and improve the integration level.

[0013] Preferably, the fan-out buffer unit is implemented by a dedicated fan-out buffer chip to provide optimal signal integrity and channel isolation.

[0014] Preferably, the constant fraction timing module extracts the zero-crossing point of the differential signal as the time zero point by delaying, attenuating and differentiating the initial electrical signal. The zero-crossing point corresponds to a fixed proportion point (e.g. 50% peak height) of the original signal waveform, thereby eliminating the influence of amplitude fluctuation.

[0015] Preferably, the time jitter of the time zero point is less than 100 picoseconds, which is significantly better than the fixed threshold triggering method.

[0016] Preferably, the post-stage device includes an ultrafast laser spectroscopy, a time-correlated single photon counting, a laser radar or a multi-channel high-speed data acquisition system.

[0017] In another aspect, the application provides a multi-stage system synchronization triggering method based on laser pulses, comprising the following steps: Step 1: obtaining an initial electrical signal corresponding to a laser pulse; Step 2: performing constant fraction timing processing on the initial electrical signal to determine a time zero point independent of the amplitude of the laser pulse, and generating a reference trigger signal; Step 3: distributing the reference trigger signal into multiple synchronization trigger signals as a unified reference based on the time zero point; Step 4: introducing controllable delay to at least one of the multiple synchronization trigger signals to compensate for the response time difference between the target post-stage device and the time zero point, so that multiple post-stage devices work synchronously based on the same time zero point.

[0018] Preferably, the step 3 further comprises: introducing an impedance matching network to the output channels in the multiple synchronization trigger signals, so that the impedance of each output channel is matched with the input impedance of the corresponding post-stage device.

[0019] Compared with the prior art, the application has the following advantages: The application discards the external clock and directly takes the physical laser pulse event as the time zero point, solving the fundamental contradiction between the internal timing uncertainty of the laser and the strict alignment of the external clock.

[0020] The constant fraction timing technology is used to determine the triggering time, so that the position of the synchronization trigger point is independent of the absolute amplitude of the laser pulse, greatly improving the stability and repeatability of the timing.

[0021] The consistency of the waveforms and timing of the multi-path trigger signals is ensured by fan-out buffering and impedance matching; the inherent response differences of different subsequent devices are finely calibrated by programmable delay compensation, and the multi-device is precisely aligned on the picosecond to nanosecond scale.

[0022] The device can be accessed as an independent module in an existing laser system, and does not depend on specific brands of lasers or backend devices, and has good universality and scalability.

[0023] After the application, the response time of the multi-device changes from a scattered state to a highly concentrated state, effectively avoiding the misalignment of the laser pulse and the acquisition window, and improving the reliability, accuracy and signal-to-noise ratio of the entire measurement system. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The overall structure block diagram of the multi-stage system synchronous trigger device based on laser pulse provided by an embodiment of the application.

[0025] Figure 2 The schematic diagram of the electrical signal waveform after photoelectric conversion of the laser pulse in the background art shows the influence of amplitude fluctuation on fixed threshold triggering.

[0026] Figure 3 The working principle schematic diagram of the constant fractional timing module in the application.

[0027] Figure 4 The schematic diagram of the multi-channel trigger signal distribution structure in the application.

[0028] Figure 5 The schematic diagram of the digital delay chip in the delay adjustment scheme provided by an embodiment of the application.

[0029] Figure 6 The schematic diagram of the time misalignment of the laser pulse and the acquisition window (Gate) of the subsequent device in the background art.

[0030] Figure 7 The comparison schematic diagram of the multi-device response timing before and after the application of the synchronous trigger scheme of the application; Figure 8 The step schematic diagram of the multi-stage system synchronous triggering method based on laser pulse of the application.

[0031] BRIEF DESCRIPTION OF DRAWINGS 100, multi-stage system synchronous trigger device based on laser pulse; 110, photoelectric detection module; 120, constant fractional timing module; 130, trigger signal distribution module; 131, fan-out buffer unit; 132, impedance matching network; 133, delay compensation unit. DETAILED DESCRIPTION

[0032] In order to make the objects, technical solutions and advantages of the present application clearer, the following will further describe the present application in detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application.

[0033] Referring to Figure 1 , the embodiment provides a multi-stage system synchronous trigger device 100 based on laser pulse. The device 100 comprises an optoelectronic detection module 110, a constant fraction timing module 120 and a trigger signal distribution module 130 connected in sequence.

[0034] The optoelectronic detection module 110 is usually composed of a high-speed photodiode (such as PIN photodiode or avalanche photodiode) and a corresponding transimpedance amplifier. It receives the laser pulse from the laser and linearly converts it into an initial electrical signal (voltage or current signal). The initial electrical signal carries the time information of the laser pulse, but also contains amplitude noise and jitter.

[0035] The constant fraction timing module 120 receives the initial electrical signal. As Figure 3 shown, the internal circuit divides the signal into two paths: one path passes through an adjustable or fixed delay line (Delay), and the other path passes through an attenuator (Attenuator) for a certain proportion of amplitude attenuation. Then, the delayed signal and the attenuated signal are input into a differential amplifier for subtraction to obtain a differential signal. The differential signal has a zero-crossing point. Both theoretical analysis and experiments show that the zero-crossing point accurately corresponds to a fixed fraction point (for example, 50% of the peak value) on the original input signal waveform, and is independent of the absolute amplitude of the signal. Therefore, detecting the zero-crossing point of the differential signal can obtain a stable "time zero point" independent of the amplitude fluctuation of the laser pulse. The constant fraction timing module 120 outputs a digital level signal with steep edges corresponding to this moment as a reference trigger signal. In the preferred embodiment of the present application, the module can control the jitter of the time zero point to be below 100 picoseconds.

[0036] The trigger signal distribution module 130 receives the reference trigger signal and is responsible for reliably distributing it to multiple subsequent devices (such as TDC, DAQ Card, etc.). The module 130 further comprises a fan-out buffer unit 131, an impedance matching network 132 and a delay compensation unit 133.

[0037] The fan-out buffer unit 131 is used to reproduce one reference trigger signal into multiple (such as 4, 8 or more) trigger signals with good isolation and driving ability. The unit can be realized by a dedicated fan-out buffer chip (such as Texas Instruments CDC series), or by multiple output buffers of FPGA.

[0038] Impedance matching network 132 is connected to each output terminal of fan-out buffer unit 131 to match the impedance of each output channel with the input impedance of the corresponding downstream device. For example... Figure 4 As shown, it ensures the continuity of transmission line impedance from the device output port to the input port of the subsequent device, typically terminated with a 50-ohm resistor to minimize signal reflection, ringing, and edge degradation, thereby maintaining a high degree of consistency in the waveform and timing of the multiplexed trigger signals.

[0039] The delay compensation unit 133 is key to achieving precise alignment of multiple devices in this invention. It introduces controllable delay adjustment in at least a portion of the output channels. Specific implementations may include: Coaxial cable delay: A fixed delay is introduced by physically replacing coaxial cables of different lengths. The method is simple, low-cost, and suitable for situations where the delay requirement is fixed.

[0040] Digital delay chips: These utilize dedicated programmable delay integrated circuits (such as Analog Devices' AD9501 series). Internal registers are configured via a digital interface (such as SPI), enabling precise delays with step accuracy ranging from picoseconds to nanoseconds and delay ranges up to tens of nanoseconds. This method offers excellent accuracy and stability, and the delay value can be flexibly set via software. Figure 5 As shown, the microcontroller input delay value N and the total delay time T = N*τ are simple, have high delay accuracy (10ps~ns), and high stability.

[0041] FPGA-based delay control logic: Within the FPGA, high-resolution, dynamically configurable delays are achieved using dedicated IODELAY units or clock-managed digital logic (such as DLLs or PLLs that generate multi-phase clocks for interpolation). In a highly integrated embodiment, the functions of the fan-out buffer unit 131 and the delay compensation unit 133 can all be implemented by programming the same FPGA.

[0042] In actual deployment, the user first measures the inherent response time of each downstream device from receiving the trigger signal to actually performing an action (such as opening the shutter or starting sampling), without connection delay or with zero delay set. Then, in the trigger signal distribution module 130, an additional delay is set for the device channel with the shorter response time, so that the total delay (inherent device delay + compensated delay) of all device channels is consistent. In this way, although the electrical signals arrive at each device at different times, the physical moment of each device performing the action is precisely aligned with the "time zero point" of the laser pulse.

[0043] Figure 7The effect of applying this invention is visually demonstrated: the left side shows the dispersed triggering timing without this invention, while the right side shows the highly synchronized triggering timing of all devices after applying this invention. Without this invention, the triggering times of each downstream device are significantly dispersed; however, after applying this invention, all devices respond synchronously based on the zero point of the same laser pulse time, significantly improving the system's time consistency and repeatability.

[0044] By abandoning the external clock and directly using the physical laser pulse event as the time zero point, the fundamental contradiction between the internal timing uncertainty of the laser and the inability of the external clock to be strictly aligned is resolved.

[0045] By employing constant fractional timing technology to determine the triggering time, the position of the synchronous triggering point becomes independent of the absolute amplitude of the laser pulse, greatly improving the stability and repeatability of the timing sequence.

[0046] Fan-out buffering and impedance matching ensure the consistency of waveforms and timing of multiple trigger signals; programmable delay compensation finely calibrates the inherent response differences of different downstream devices, enabling precise alignment of multiple devices on the picosecond to nanosecond scale.

[0047] The multi-level system synchronization triggering device 100 based on laser pulses can be connected to existing laser systems as an independent module, without relying on specific brands of lasers or back-end equipment, and has good versatility and scalability.

[0048] After applying this invention, the response times of multiple devices change from a dispersed state to a highly concentrated state, effectively avoiding the problem of misalignment between laser pulses and acquisition windows, and improving the reliability, accuracy and signal-to-noise ratio of the entire measurement system.

[0049] Preferably, the downstream equipment includes ultrafast laser spectroscopy, time-correlated single-photon counting, lidar, or a multi-channel high-speed data acquisition system.

[0050] like Figure 8 As shown, the present invention provides a method for synchronous triggering of a multi-level system based on laser pulses, comprising the following steps: Step S1: Obtain the initial electrical signal corresponding to the laser pulse; Step S2: Perform constant fractional timing processing on the initial electrical signal to determine the zero point of time, which is independent of the laser pulse amplitude, and generate a reference trigger signal; Step S3: Using the zero point of time as a unified reference, distribute the reference trigger signal into multiple synchronous trigger signals; Step S4: Introduce a controllable delay to at least one of the multiple synchronous trigger signals to compensate for the response time difference between the target downstream device and the zero point of time, so that multiple downstream devices can work synchronously based on the same zero point of time.

[0051] Step S1 is achieved through photoelectric conversion. Specifically, a photodetector is used to receive the laser pulses output by the pulsed laser and linearly convert them into an analog electrical signal (voltage or current signal), called the initial electrical signal. The rise time and amplitude of this signal carry the original timing information of the laser pulse, but also contain the inherent amplitude noise and jitter of the laser.

[0052] Step S2 is the core of accurately extracting the absolute time reference, and its implementation includes: Signal processing: The initial electrical signal is split into two paths. One path passes through a fixed or adjustable delay line, introducing a delay τ (for example, τ is set to be slightly less than the pulse rise time, such as 300 ps). The other path passes through an attenuator, which attenuates its amplitude to k times the original amplitude (k is a constant fraction, usually taken as 0.5~0.9, for example 0.7).

[0053] Differential and Zero-Crossing Detection: The delayed signal and the attenuated signal are input into a high-speed differential amplifier and subtracted to obtain the differential signal. The zero-crossing point of this differential signal corresponds to a fixed fractional height point on the waveform of the original laser pulse electrical signal (such as (1+k) / 2 of the peak height).

[0054] Zero-point generation: A high-speed voltage comparator detects the zero-crossing point of the differential signal and generates a digital level signal (such as LVTTL or LVDS level) with a steep edge (rise time <1 ns) at this moment. This signal is the reference trigger signal, and the time defined by its rising edge is the system's zero-point. By optimizing the circuit, the RMS time jitter of this zero-point can be reduced to less than 100 picoseconds.

[0055] Step S3 aims to copy and transfer the time reference without loss, and its implementation includes: Fan-out buffer: The single-channel reference trigger signal generated in step S2 is input to the fan-out buffer unit. The fan-out buffer unit can be implemented by a dedicated fan-out buffer chip (such as TI's CDCLVC1104) or by multiple global clock buffers of an FPGA to generate multiple (such as 4-channel or 8-channel) copies of the synchronization signal with low inter-channel skew.

[0056] Impedance matching: Each signal after fan-out is output through an impedance matching network. For example, a precision resistor (e.g., 50Ω) is connected in series at each output terminal, and it is ensured that a coaxial cable with characteristic impedance matching (e.g., 50Ω RG-316) is used to connect to the subsequent equipment. Simultaneously, the input terminals of the subsequent equipment must be set to matched termination mode (e.g., 50Ω). This operation aims to minimize signal reflections and ensure the consistency of signal waveforms and timing fidelity across all channels.

[0057] Step S4 is a crucial calibration step for achieving precise alignment of the final physical actions of multiple devices. Its implementation includes a systematic measurement-calculation-compensation process: Step S4.1 Measurement of inherent system delay: Step S4.1.1 Temporarily set the active delay compensation for all channels to 0.

[0058] Step S4.1.2 Use a high-bandwidth oscilloscope to simultaneously measure the initial electrical signal (as a reference for the physical time zero point) and the trigger signal of each output of the device.

[0059] Step S4.1.3 Record the delay time D of each output signal edge relative to a fixed characteristic point (such as the peak value) of the initial electrical signal. i (i is the channel number). D i It includes the inherent delays in the device's internal photoelectric conversion, CFD processing, and signal distribution paths.

[0060] Step S4.2 Device response delay measurement: Measure the internal delay R of each downstream device from receiving a valid edge at its trigger input to executing a critical action (such as the shutter opening of a high-speed camera, the start of sampling on a data acquisition card, or the start of timing on a TDC). i This value can be obtained from the equipment manual or measured experimentally.

[0061] Step S4.3 Compensation Delay Calculation and Application: Step S4.3.1 Calculate the total delay for each complete path (device channel + downstream equipment): T total-i = D i + R i .

[0062] Step S4.3.2 Find all T total-i The maximum value T in max .

[0063] Step S4.3.3 calculates the programmable compensation delay value to be added for the i-th channel: C i = T max -T total-i This means that the channel with the longest total delay has a compensation delay of 0, and the other channels have their delay increased to align with it.

[0064] Step S4.3.4 calculates C i The value is configured into the delay compensation unit of the corresponding channel. This unit can be implemented as follows: FPGA-based logic delay: This is achieved by configuring the number of taps in precision delay units such as IODELAYE2 and ODELAYE2 within the FPGA, with a resolution on the order of 10 ps.

[0065] Digital delay chip: The delay value is set by configuring the registers of a dedicated delay chip through interfaces such as SPI.

[0066] Fixed coaxial cable: by replacing it with a longer one (C) i A cable with a *speed of light coefficient* is used to approximate a fixed delay (suitable for situations where frequent adjustments are not required).

[0067] Step S4.4 Synchronization: After completing the above delay compensation configuration, when the laser pulse is generated again, all downstream devices will receive the trigger signal that has been precisely calibrated by their respective channels. The physical timing of their internal key actions will all be traced back to the same laser pulse time zero point, thereby achieving system-level synchronous triggering at the picosecond to nanosecond level.

[0068] Through the specific and operable steps described above, this method transforms the core idea of ​​"using laser pulses as a time reference" into a standardized and calibrable process flow. It not only clarifies "what to do," but also clearly indicates "how to do it" and "how to calibrate," ensuring that those skilled in the art can reliably implement it, ultimately achieving the technical effect of high-precision synchronization of multiple devices.

[0069] In summary, this invention constructs a novel, high-precision multi-level system synchronization triggering architecture by defining the zero point of the laser pulse itself and supplementing it with constant fractional timing, consistent distribution, and calibrable delay techniques. Those skilled in the art can make various modifications, equivalent substitutions, or improvements within the concept and principles of this invention, and all such modifications should be included within the scope of protection of this invention.

Claims

1. A multi-level system synchronous triggering device based on laser pulses, characterized in that, include: A photoelectric detection module is used to receive laser pulses and convert them into initial electrical signals; A constant fraction timing module, connected to the photoelectric detection module, is used to extract a zero-crossing point independent of the laser pulse amplitude from the initial electrical signal, take the triggering time of the zero-crossing point as the time zero point, and output the reference trigger signal corresponding to the time zero point. The trigger signal distribution module, connected to the constant fraction timing module, is used to distribute the reference trigger signal to multiple downstream devices, so that the trigger time of each downstream device is traced back to the zero point of time.

2. The multi-level system synchronous triggering device based on laser pulses according to claim 1, characterized in that, The trigger signal distribution module includes: A fan-out buffer unit is used to distribute the reference trigger signal into multiple trigger signals; A delay compensation unit is provided on the output channel of at least one trigger signal to adjust the transmission delay of at least one of the trigger signals in order to compensate for the response time difference between the corresponding downstream device and the zero point of time.

3. The multi-level system synchronous triggering device based on laser pulses according to claim 2, characterized in that, The trigger signal distribution module further includes an impedance matching network connected to multiple output channels of the fan-out buffer unit, used to match the impedance of each output channel with the input impedance of the corresponding downstream device.

4. The multi-level system synchronous triggering device based on laser pulses according to claim 2, characterized in that, The delay compensation unit includes at least one of a digital delay chip or a delay control logic based on a field-programmable gate array.

5. The multi-level system synchronous triggering device based on laser pulses according to claim 4, characterized in that, The delay compensation unit and the fan-out buffer unit are integrated in the same field-programmable gate array.

6. The multi-level system synchronous triggering device based on laser pulses according to claim 1, characterized in that, The constant fractional timing module extracts the zero-crossing point of the differential signal as the time zero point by delaying, attenuating, and differentially processing the initial electrical signal.

7. The multi-level system synchronous triggering device based on laser pulses according to claim 1, characterized in that, The time jitter at the zero point is less than 100 picoseconds.

8. The multi-level system synchronous triggering device based on laser pulses according to any one of claims 1 to 7, characterized in that, The downstream equipment includes ultrafast laser spectroscopy, time-correlated single-photon counting, lidar, or a multi-channel high-speed data acquisition system.

9. A method for synchronous triggering of a multi-stage system based on laser pulses, characterized in that, Includes the following steps: Step 1: Obtain the initial electrical signal corresponding to the laser pulse; Step 2: Perform constant fractional timing processing on the initial electrical signal to determine the zero point of time, which is independent of the laser pulse amplitude, and generate a reference trigger signal; Step 3: Using the zero point of time as a unified reference, distribute the reference trigger signal into multiple synchronous trigger signals; Step 4: Introduce a controllable delay to at least one of the multiple synchronous trigger signals to compensate for the response time difference between the target downstream device and the zero point of time, so that multiple downstream devices can work synchronously based on the same zero point of time.

10. The method for synchronous triggering of a multi-stage system based on laser pulses according to claim 9, characterized in that, Step 3 also includes: An impedance matching network is introduced into the output channels of the multi-channel synchronous trigger signal to match the impedance of each output channel with the input impedance of the corresponding downstream device.

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