Multi-band optical synchronous observation system for impact safety of energetic materials

Abstract

The application discloses a multi-waveband optical synchronous observation system for impact safety of energetic materials, and belongs to the technical field of impact test of energetic materials. The prior art cannot simultaneously acquire image information of three wavebands of visible light, infrared and X-ray in the same test, and the compatibility of a drop hammer device and a multi-light-path system is poor, and the synchronous triggering precision is insufficient. In the application, a drop hammer cavity comprises an upper cavity and a lower cavity, a reflecting element is arranged in the cavity, multi-waveband light sources vertically penetrate a sample after being reflected, and the emitted light enters a visible light imaging unit and an infrared imaging unit after being split by a dichroic mirror; X-ray is converted into an X-ray imaging unit after penetrating the sample; and a synchronous triggering module triggers each imaging unit and the light source according to a preset time sequence delay. The application is used for evaluating the impact safety of energetic materials, and can synchronously acquire deformation, temperature and internal structure information.

Description

Technical Field

[0001] This invention belongs to the field of energetic material impact testing technology. More specifically, this invention relates to a multi-band optical synchronous observation system for the impact safety of energetic materials. Background Technology

[0002] The ignition behavior of energetic materials under impact loads is a crucial indicator of their safety, and drop hammer impact testing is one of the standard methods for characterizing the impact sensitivity of energetic materials. During drop hammer impact, an ultrafast dynamic evolution with strong force-thermal-chemical coupling occurs within the energetic material, with a timescale ranging from microseconds to milliseconds and a spatial scale ranging from micrometers to millimeters. To reveal the impact ignition mechanism, it is necessary to simultaneously acquire information on the deformation field, temperature field, and internal structural evolution of the material surface.

[0003] Current testing technologies suffer from the following main problems and drawbacks. Existing technologies are primarily categorized into single-band and dual-band technologies. In single-band technologies, high-speed visible light imaging can record macroscopic material deformation, crack propagation, and flame propagation, but it cannot acquire temperature distribution and internal structural information. High-speed infrared imaging can capture surface temperature fields and hotspot evolution, but its spatial resolution and frame rate are limited, and it cannot observe the material's interior. X-ray imaging can penetrate opaque materials to obtain information on internal pores, cracks, and particle breakage, but traditional X-ray dynamic imaging is difficult to synchronize, and it cannot simultaneously obtain surface temperature and deformation information. Regarding dual-band technologies, a few studies have combined visible light and mid-wave infrared cameras to acquire deformation and temperature data in the same experiment, but internal structural information is still unavailable. Furthermore, due to the transmittance limitations of optical window materials, long-wave infrared bands are typically excluded. Therefore, current technologies cannot simultaneously acquire image information of energetic materials in the visible, infrared, and X-ray bands in the same drop-weight impact test, at the same spatial location, and with the same time reference, making it difficult to establish multi-physics coupling relationships between deformation, temperature rise, and structural evolution.

[0004] Traditional falling weight apparatuses employ a vertical loading structure, with the hammer and base occupying a significant amount of space, limiting the available optical interfaces on the sides. When simultaneously accommodating visible light, infrared, and X-ray optical paths, spatial interference easily arises between these paths. The upper cavity needs to provide a path for the incident light source, the lower cavity for the outgoing light, and X-rays need to penetrate the sample horizontally; these optical paths conflict within the limited space. Furthermore, conventional optical window materials have a certain transmittance for visible light and infrared, but weak X-ray penetration and limited impact resistance. After repeated impacts from the falling hammer, the window may be damaged, affecting the stability of the optical paths. Due to the lack of window materials that can simultaneously meet the requirements of high transmittance and impact resistance across multiple wavelengths, and the lack of cavity structures that can integrate multiple reflective elements and incident / outgoing interfaces, existing devices struggle to simultaneously accommodate three optical systems: visible light, infrared, and X-rays.

[0005] The hotspot formation process of energetic materials impact ignition can reach the microsecond scale. Existing systems mostly employ a cascaded external trigger signal approach: after a laser velocity sensor detects the hammer, it sequentially triggers the light source, cameras, and other devices. Due to varying response delays and inconsistent signal transmission path lengths among these devices, timing matching errors typically reach tens of microseconds. This level of timing error cannot guarantee strict temporal correspondence between images from different spectral bands, leading to misalignment of deformation, temperature rise, and internal structural evolution on the timeline, making it difficult to establish coupling. To achieve nanosecond-level synchronous triggering, it is necessary to solve problems such as low jitter output of multi-channel trigger signals, strict matching of transmission paths, and precise calibration of the trigger responses of each imaging device, which have not yet been effectively addressed in existing technologies.

[0006] The impact of a falling hammer generates intense mechanical vibrations, which can easily cause camera and optical component jitter, resulting in blurred images. Ambient stray light and the intense flame radiation generated during the ignition of energetic materials can reduce the signal-to-noise ratio of infrared images and even saturate infrared detectors, affecting the accuracy of temperature measurements. In X-ray dynamic imaging, motion blur can also occur due to long exposure times or insufficient synchronization precision, making it difficult to clearly distinguish micron-level internal structural details. The presence of these interfering factors makes it difficult for existing imaging systems to clearly capture the evolutionary details of micron-level hotspots. These problems limit a deeper understanding of the intrinsic mechanisms of impact ignition in energetic materials. Summary of the Invention

[0007] To achieve these objectives and other advantages of the present invention, the present invention provides a multi-band optical synchronous observation system for the impact safety of energetic materials, including a falling hammer loading module, a falling hammer cavity, an optical window, a multi-band light source module, an X-ray source, a visible light imaging unit, an infrared imaging unit, an X-ray imaging unit, and a synchronous triggering module. The falling hammer loading module includes a hammer body and a trigger signal generating device for detecting the falling of the hammer body. The trigger signal generating device is a position sensor set on the falling path of the hammer body, which is used to generate a trigger signal when the hammer body falls to a predetermined position before impact. The drop hammer cavity includes an upper cavity rigidly connected to the hammer body and a lower cavity fixed to the base. The upper and lower cavities are coaxially opposite each other. A reflective element is installed inside the upper cavity, and a light source inlet and an X-ray inlet window are opened on the side wall of the upper cavity. An upper optical window is installed on the lower end face of the upper cavity. A reflective element is installed inside the lower cavity, and a light outlet and an X-ray outlet window are opened on the side wall of the lower cavity. A lower optical window is installed on the upper end face of the lower cavity. The lower optical window is used to place the test sample, so that the test sample is located between the upper optical window and the lower optical window. Both the upper and lower optical windows have transmittance for visible light, infrared light, and X-rays. The output light of the multi-band light source module enters the upper cavity through the light source inlet, and after being reflected by the reflective element, it passes vertically through the upper optical window, the test sample and the lower optical window. After entering the lower cavity, it is reflected by the reflective element to the light outlet and emitted. The emitted light is split by the dichroic mirror and then enters the visible light imaging unit and the infrared imaging unit respectively. The X-rays output from the X-ray source penetrate the sample to be tested through the X-ray incident window and exit through the X-ray exit window. The exited X-rays are converted and then enter the X-ray imaging unit. The synchronous triggering module is a multi-channel synchronous trigger. Its trigger input is connected to a trigger signal generator, and its trigger output is connected to a multi-band light source module, a visible light imaging unit, an infrared imaging unit, and an X-ray imaging unit according to a preset timing delay. The preset timing delay is configured to match the start-up time of each imaging unit and light source module with the event of the hammer impacting the test sample. The timing matching error between the trigger signals output by the multi-channel synchronous trigger is less than the time scale of the energetic material ignition process.

[0008] Preferably, the reflective element disposed in the upper cavity is a silver-plated reflector, and the silver-plated reflector has a reflectivity of not less than 98% for the visible light band and the mid-wave infrared band; the reflective element disposed in the lower cavity is a gold-plated reflector, and the gold-plated reflector has a reflectivity of not less than 99% for the mid-wave infrared band and the long-wave infrared band, and a reflectivity of not less than 85% for the visible light band.

[0009] Preferably, the upper optical window and the lower optical window are single-crystal diamond optical windows.

[0010] Preferably, the infrared imaging unit includes a mid-wave infrared high-speed camera and / or a long-wave infrared high-speed camera and an infrared beam splitter. The infrared beam splitter is disposed in the optical path between the mid-wave infrared high-speed camera and the long-wave infrared high-speed camera. The infrared beam splitter has transmittance in the 3μm to 5μm band and reflectivity in the 8μm to 14μm band, or the infrared beam splitter has reflectivity in the 3μm to 5μm band and transmittance in the 8μm to 14μm band.

[0011] Preferably, the X-ray imaging unit includes a scintillator, a reflector, and a black-and-white high-speed camera; X-rays that have penetrated the test sample are incident on the scintillator, which converts the X-rays into visible light signals, and the visible light signals are deflected by the reflector and then incident on the black-and-white high-speed camera.

[0012] Preferably, the visible light imaging unit includes a color high-speed camera and a microscope lens, wherein the frame rate of the color high-speed camera is not less than 1 million frames per second, and the spatial resolution of the color high-speed camera is not less than 10 μm per pixel.

[0013] Preferably, the time resolution of the multi-channel synchronous trigger is not less than 1 ns; the trigger output terminal of the multi-channel synchronous trigger is connected to the visible light imaging unit, the infrared imaging unit, the X-ray imaging unit, and the multi-band light source module via coaxial cables of equal length.

[0014] Preferably, a narrowband filter is disposed between the dichroic mirror and the infrared imaging unit, the center wavelength of the narrowband filter being 3.9 μm or 10.6 μm, and the full width at half maximum (FWHM) of the narrowband filter being no greater than 200 nm.

[0015] Preferably, the X-ray source is a synchrotron radiation X-ray source or a pulsed X-ray source, and the multi-channel synchronous trigger controls the X-ray source to emit X-ray pulses within a time window from 1 μs before the hammer strikes the test sample to 10 μs after the hammer strikes the test sample.

[0016] This invention also discloses an observation method based on the multi-band optical synchronous observation system for impact safety of the energetic material, comprising the following steps: The test sample is placed on the lower optical window, so that the test sample is located between the upper optical window and the lower optical window; The dropping hammer loading module is activated to release the hammer body. The trigger signal generating device generates a trigger signal when the hammer body falls to the predetermined position before impact and sends the trigger signal to the trigger input terminal of the synchronous trigger module. The synchronous triggering module receives the trigger signal and outputs trigger signals to the multi-band light source module, the visible light imaging unit, the infrared imaging unit, and the X-ray imaging unit respectively through the multiple trigger output terminals according to a preset timing delay. The preset timing delay is configured to match the emission time of the multi-band light source module, the exposure time of the visible light imaging unit, the exposure time of the infrared imaging unit, and the exposure time of the X-ray imaging unit with the time when the hammer hits the test sample, and the timing matching error between each trigger signal is less than 500ns. After receiving a trigger signal, the multi-band light source module outputs multi-band light. The multi-band light enters the upper cavity through the light source entrance, is reflected by the reflective element, and then passes vertically through the upper optical window, the test sample, and the lower optical window. After entering the lower cavity, it is reflected by the reflective element to the light exit port. The multi-band light emitted from the light exit port is split by the dichroic mirror and then enters the visible light imaging unit and the infrared imaging unit respectively. The visible light imaging unit acquires a visible light image sequence, and the infrared imaging unit acquires a mid-wave infrared image sequence and a long-wave infrared image sequence. After receiving a trigger signal, the X-ray source outputs an X-ray pulse. The synchronous triggering module controls the pulsed X-ray source to emit an X-ray pulse with a pulse width of no more than 100 ns within a time window from 1 μs before the hammer strikes the test sample. The X-ray pulse penetrates the test sample through the X-ray incident window and exits from the X-ray exit window. The exited X-rays are converted and then enter the X-ray imaging unit to be acquired as an X-ray image sequence.

[0017] The present invention offers at least the following advantages: The multi-band optical synchronous observation system for the impact safety of energetic materials described herein, by integrating reflective elements within the impact hammer cavity and employing a coaxially opposed upper and lower cavity structure, and simultaneously using a single-crystal diamond optical window with high transmittance for visible light, mid-wave infrared, long-wave infrared, and X-rays, achieves for the first time simultaneous imaging of energetic materials in four channels—visible light, mid-wave infrared, long-wave infrared, and X-rays—at the same spatial location during the same impact hammer test. This solves the problem that existing technologies cannot simultaneously acquire information on surface deformation, wide-range temperature distribution, and internal structural evolution. The upper cavity uses a silver-plated reflector with a reflectivity of not less than 98% for visible light and mid-wave infrared, while the lower cavity uses a gold-plated reflector with a reflectivity of not less than 99% for mid-wave and long-wave infrared and not less than 85% for visible light, effectively ensuring efficient transmission of multi-band optical paths and reducing light energy loss. The diamond window exhibits transmittance of no less than 50% in the 380nm-780nm, 3μm-5μm, 8μm-14μm, and X-ray bands, while maintaining an impact strength of no less than 500MPa, thus meeting the requirements for high transmittance across multiple bands and resistance to strong impacts from falling hammers. The infrared imaging unit, equipped with an infrared beam splitter and two high-speed infrared cameras (mid-wave and long-wave), can simultaneously acquire temperature field information in two infrared bands, expanding the temperature measurement range and enabling the simultaneous capture of high-temperature hotspots and ambient temperature rise processes. The X-ray imaging unit uses a scintillator to convert X-rays into visible light, which is then deflected by a mirror and acquired by a monochrome high-speed camera. This solves the problem of X-rays not being directly recorded by a high-speed camera and avoids optical path interference. Furthermore, the monochrome camera has high sensitivity and is suitable for weak light signals. The visible light imaging unit uses a color high-speed camera with a frame rate of no less than 1 million frames per second and a spatial resolution of no less than 10μm per pixel, capable of clearly capturing details such as micron-level crack propagation, particle breakage, and flame color during the impact of energetic materials. The synchronous triggering module employs a multi-channel synchronous trigger with a time resolution of no less than 1 ns. Connecting each device via coaxial cables of equal length ensures that the timing matching error of each trigger signal is controlled to less than 500 ns, far less than the μs-level hotspot formation time of energetic materials. This guarantees strict correspondence between visible light, infrared, and X-ray images on the time axis, enabling coupled analysis of deformation, temperature rise, and structural evolution. A narrowband filter with a center wavelength of 3.9 μm or 10.6 μm and a half-width at half-maximum of 200 nm is used in the infrared optical path. This effectively filters out the intense flame radiation generated by the energetic material reaction and ambient stray light, significantly improving the signal-to-noise ratio and temperature measurement accuracy of the infrared image. A pulsed X-ray source with a pulse width of no more than 100 ns is used, controlled by the synchronous trigger to emit X-ray pulses within a time window of 1 μs before to 10 μs after the hammer impact. This achieves "frozen" imaging of the dynamic changes in the internal structure at the μs level, while simultaneously reducing radiation damage to the sample.The entire observation method clarifies the specific steps of sample installation, trigger signal generation, timing delay configuration, and three-band image sequence acquisition, making the timing accuracy of each experiment controllable and the operation repeatable. It provides reliable multi-physics synchronous experimental data for the study of impact ignition mechanism of energetic materials, impact sensitivity assessment, and formulation optimization design.

[0018] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the multi-band optical synchronous observation system for the impact safety of energetic materials described in this invention.

[0020] Figure 2 This is a three-dimensional diagram of the multi-band optical synchronous observation system for the impact safety of energetic materials described in this invention.

[0021] Figure 3 This is a schematic diagram of the optical path of the drop hammer loading module described in this invention.

[0022] Figure 4 This is a schematic diagram of the optical path of the X-ray imaging unit described in this invention.

[0023] Figure 5 This is a schematic diagram of the optical path of the visible light imaging unit described in this invention.

[0024] Figure 6 This is a schematic diagram of the optical path of the infrared imaging unit described in this invention. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can implement it based on the description.

[0026] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0027] like Figure 1-6 As shown, the present invention provides a multi-band optical synchronous observation system for the impact safety of energetic materials, including a falling hammer loading module, a falling hammer cavity, an optical window 300, a multi-band light source module 701, an X-ray source, a visible light imaging unit, an infrared imaging unit 500, an X-ray imaging unit, and a synchronous triggering module 700. The falling hammer loading module includes a hammer body 101 and a trigger signal generating device for detecting the falling of the hammer body 101. The trigger signal generating device is a position sensor set on the falling path of the hammer body 101, which is used to generate a trigger signal when the hammer body 101 falls to a predetermined position before impact. The drop hammer cavity includes an upper cavity 100 rigidly connected to the hammer body 101 and a lower cavity 200 fixed to the base 201. The upper cavity 100 and the lower cavity 200 are coaxially opposite each other. A reflective element is provided inside the upper cavity 100. A light source inlet and an X-ray inlet window are opened on the side wall of the upper cavity 100. An upper optical window 301 is installed on the lower end face of the upper cavity 100. A reflective element is provided inside the lower cavity 200. A light outlet and an X-ray outlet window are opened on the side wall of the lower cavity 200. A lower optical window 302 is installed on the upper end face of the lower cavity 200. The lower optical window 302 is used to place the test sample 800, so that the test sample 800 is located between the upper optical window 301 and the lower optical window 302. Both the upper optical window 301 and the lower optical window 302 have transmittance for visible light, infrared light, and X-rays. The output light of the multi-band light source module 701 enters the upper cavity 100 through the light source inlet, and after being reflected by the reflective element, it passes vertically through the upper optical window 301, the test sample 800 and the lower optical window 302, and enters the lower cavity 200. After being reflected by the reflective element, it exits through the light outlet. The exited light is split by the dichroic mirror 501 and then enters the visible light imaging unit and the infrared imaging unit 500 respectively. The X-rays output from the X-ray source penetrate the test sample 800 through the X-ray incident window 603 and exit through the X-ray exit window 604. The exited X-rays are converted and then enter the X-ray imaging unit. The synchronous trigger module 700 is a multi-channel synchronous trigger. Its trigger input is connected to a trigger signal generator, and its trigger output is connected to a multi-band light source module 701, a visible light imaging unit, an infrared imaging unit 500, and an X-ray imaging unit according to a preset timing delay. The preset timing delay is configured to match the start-up time of each imaging unit and light source module with the event of the hammer 101 striking the test sample 800. The timing matching error between the trigger signals output by the multi-channel synchronous trigger is less than the time scale of the energetic material ignition process.

[0028] In the above technical solution, the falling hammer loading module can include a steel hammer body 101 and a trigger signal generating device. The weight of the hammer body 101 can be selected according to the test requirements, such as 2kg, 5kg, or 10kg, and the material can be chromium-molybdenum alloy steel. The trigger signal generating device can be a set of through-beam laser photoelectric sensors, which are set to the side of the falling path of the hammer body 101, specifically fixed at a predetermined height of about 10mm from the upper surface of the test sample 800 on the lower end surface of the hammer body 101. When the hammer body 101 falls and interrupts the laser beam, the sensor generates an electrical pulse signal, which serves as the initial time reference for the operation of the entire system.

[0029] The drop hammer chamber includes an upper chamber 100 and a lower chamber 200. The upper chamber 100 is rigidly connected to the hammer 101 and falls with it. A silver-plated plane mirror can be installed inside, with its reflective surface at a 45° angle to the vertical direction during installation. A light source entrance is provided on the side wall of the upper chamber 100, where a barium fluoride protective window can be installed, and an X-ray entrance window can be provided, which can be sealed with a beryllium sheet approximately 0.5 mm thick. The lower chamber 200 is fixed to the base 201 and coaxially opposite the upper chamber 100. A gold-plated plane mirror can be installed inside, with its installation angle corresponding to that of the upper mirror. A light exit port and an X-ray exit window are provided on the side wall of the lower chamber 200; the latter can also be sealed with a beryllium sheet. An upper optical window 301 is installed on the lower end face of the upper chamber 100 via a pressure ring, and a lower optical window 302 is installed on the upper end face of the lower chamber 200 in the same manner. The optical window 300 can be made of a single-crystal diamond sheet prepared by chemical vapor deposition, with a thickness of about 1 mm. Its transmittance in the 380 nm to 780 nm, 3 μm to 5 μm, 8 μm to 14 μm and X-ray bands is not less than 50%, and its impact resistance is not less than 500 MPa. The test sample 800 is placed at the center of the upper surface of the lower optical window 302.

[0030] The output light from the multi-band light source module 701 enters the upper cavity 100 through the light source entrance port. After being deflected by an internal reflector, it penetrates vertically downwards through the upper window, sample, and lower window, enters the lower cavity 200, and is again deflected horizontally by a reflector before exiting from the light exit port. The emitted light is split by a dichroic mirror 501, reflecting visible light to a visible light imaging unit composed of a color high-speed camera and a microscope lens, and transmitting infrared light to an infrared imaging unit 500. A narrowband filter with a center wavelength of 3.9 μm or 10.6 μm and a half-width at half-maximum (FWHM) of no more than 200 nm can be first placed in the optical path of the infrared imaging unit 500. The beam is then split by an infrared beam splitter and received by a mid-wave infrared high-speed camera and a long-wave infrared high-speed camera, respectively. The X-ray source can be a pulsed X-ray tube with a pulse width of no more than 100 ns. The emitted X-rays penetrate horizontally through the X-ray entrance window, sample, and exit window before entering the X-ray imaging unit. This unit contains a cesium iodide scintillator that converts X-rays into a visible light image, which is then deflected by a mirror before being captured by a high-speed monochrome camera. The core control component of the system is a multi-channel digital delay pulse generator with a time resolution of no less than 1 ns. Its trigger input is connected to the signal output of the position sensor, and multiple trigger outputs are connected via 2-m long coaxial cables to the power supply of the multi-band light source module 701, the external trigger interfaces of each high-speed camera, and the trigger interface of the pulsed X-ray source, respectively. By pre-measuring the response delay of each device and setting compensation values, the start-up time of all imaging and illumination devices is precisely matched with the time of impact of the hammer 101 on the sample, and the timing matching error between the trigger signals can be controlled to less than 500 ns.

[0031] The preset timing delay refers to the independent delay time value set for each trigger output channel of the multi-channel synchronous trigger relative to its trigger input signal (the trigger signal from the position sensor). This delay time value is determined by prior measurement and calibration, so that the absolute value of the time deviation between the actual working time of each imaging unit and light source module (i.e., the light source emission time, the camera exposure midpoint time, and the X-ray pulse emission time) and the nominal time when the hammer impacts the test sample does not exceed ±500 ns, and the relative timing matching error between each channel (i.e., the maximum difference between the actual working times of any two channels) is less than the time scale of the energetic material ignition process.

[0032] The specific method for setting the preset timing delay includes the following steps: The first step is to calibrate the drop hammer motion parameters. A high-speed photoelectric sensor or accelerometer is installed on the lower end face of the hammer. Through multiple no-load drop hammer tests, the average flight time T of the hammer from the trigger position of the trigger signal generator (position sensor) to the point of impact on the upper surface of the test sample is measured. impactThe measurement should be repeated at least 10 times, and the average value should be taken. The measurement accuracy should be better than 1 μs.

[0033] The second step is to measure the intrinsic response delay of each device. The following delay time is measured separately: the delay To from receiving the trigger pulse to outputting stable illumination light from the multi-band light source module. light The delay T between receiving the trigger pulse and the start of exposure for the visible light imaging unit. vis In the infrared imaging unit, the respective delays T of the mid-wave infrared high-speed camera and the long-wave infrared high-speed camera are... mwir and T lwir In an X-ray imaging unit, the delay T between receiving a trigger pulse and emitting an X-ray pulse from the X-ray source is... xray And the delay T of a black-and-white high-speed camera from receiving the trigger pulse to starting exposure. cam,x All delay measurements were performed using a digital oscilloscope with a bandwidth of at least 500MHz, with a single measurement error not exceeding 5ns. Each device was measured 10 times and the average value was taken.

[0034] The third step is to calculate the preset delay value for each channel. This is based on the moment T when the hammer strikes the sample. impact Let T be the arrival time of the trigger input signal of the multi-channel synchronous trigger, which is considered as the zero point in time. trigger ,but: Preset delay D of multi-band light source module light = T impact - T trigger - T light ; Preset delay D of visible light imaging unit vis = T impact - T trigger - T vis ; Preset delay D of the infrared imaging unit mwir = T impact - T trigger - T mwir D lwir similar; Preset delay D of the X-ray source xray = T impact - T trigger - T xray + ΔT xray,offset , where ΔT xray,offset It is an offset set according to the observation needs (for example, in the range of 1μs before to 10μs after the impact, it is usually set to +2μs, that is, X-ray pulse is emitted 2μs after the impact). Preset delay D of a black and white high-speed camera cam,x = D xray - Tcam,x + T xray This is to ensure that the camera exposure window is aligned with the arrival time of the X-ray pulse.

[0035] All preset delay values ​​are input to the multi-channel synchronous trigger, each channel is set independently, and the adjustment step is no greater than 1ns.

[0036] The timescale of the ignition process of energetic materials refers to the time interval required for the energetic material to form a critical hot spot and initiate a self-sustaining exothermic reaction under drop hammer impact loading, from the onset of mechanical impact. This timescale is an intrinsic parameter of the dynamic response characteristics of energetic materials, which depends on the chemical composition, microstructure, and loading conditions of the material. For the ignition process of typical elemental energetic materials (such as HMX, RDX, CL-20, etc.) under drop hammer impact conditions, the characteristic timescale of hot spot formation and initial reaction is usually on the order of sub-microseconds to tens of microseconds. Specifically: For highly sensitive energetic materials (such as CL-20-based formulations), the hotspot formation time is approximately 0.5 μs to 2 μs; For energetic materials with moderate sensitivity (such as HMX-based and RDX-based formulations), the hot spot formation time is approximately 2 μs to 20 μs. For materials with low sensitivity (such as TATB-based formulations or certain propellants), the ignition timescale can range from 50 μs to 200 μs.

[0037] In this system, the "timing matching error" is defined as the maximum time deviation between the actual working time and the theoretically set time of the devices (light source, cameras, X-ray source) driven by each trigger output channel, as well as the maximum time deviation between any two channels. By employing multi-channel synchronous triggers with a time resolution of no less than 1 ns and connecting them with coaxial cables of equal length, and calibrating the preset delay of each channel according to the above method, the measured value of the timing matching error of the entire system in any two tests is less than 500 ns. This value is much smaller than the minimum ignition time scale of the aforementioned energetic materials (the minimum is about 0.5 μs), thus meeting the requirement that "the timing matching error is less than the time scale of the energetic material ignition process." In other words, even for the fastest igniting energetic materials, the synchronization accuracy of this system is less than 1 / 2 of its characteristic time scale, ensuring that visible light, infrared, and X-ray images have alignable physical meaning within the same microsecond-level time window, avoiding decoupling of different physical fields due to timing misalignment.

[0038] In practice, users can adjust the channel delay value of the multi-channel synchronous trigger according to the actual ignition timescale of the energetic material under test, thereby further reducing the timing matching error to within 100 ns, or increasing it to no more than 1 / 3 of the characteristic ignition timescale of the material. However, regardless of the adjustment, the timing matching error in the factory calibration state of the system will not exceed 500 ns, and is clearly less than the timescale of the impact ignition process of most energetic materials (at least less than 0.5 μs).

[0039] Before the experiment, a 5mm diameter, 2mm thick energetic material tablet was placed on the upper surface of the lower optical window 302, positioned between the upper and lower windows. The dropping hammer loading module was activated to release the hammer 101, causing the upper cavity 100 to fall with it. When the lower end of the hammer 101 passed the position sensor of the trigger signal generator, the sensor generated a trigger signal and sent it to the multi-channel synchronous trigger. Upon receiving the signal, the synchronous trigger, according to a preset timing delay, sent trigger signals to the multi-band light source module 701 and each imaging unit. The light source module emitted pulsed intense light, which, after passing through the upper cavity 100 reflector and optical window 300, penetrated the sample and was then guided out by the lower cavity 200 reflector. The light was then split by the dichroic mirror 501 and entered the visible and infrared imaging units 500. Each camera simultaneously began high-frame-rate exposure, recording the deformation and temperature field changes on the sample surface. Almost simultaneously, the X-ray source emits nanosecond-level X-ray pulses within a few μs time window before and after the hammer 101 impacts the sample. The rays, after penetrating the sample, are converted by a scintillator and deflected by a mirror, and captured by a black-and-white high-speed camera, resulting in an image reflecting the instantaneous state of the sample's internal structure. After one hammer impact process, the system simultaneously acquires image sequences or single-frame images from four channels: visible light, mid-wave infrared, long-wave infrared, and X-ray.

[0040] This system can simultaneously acquire information about energetic materials in four wavelength bands from the same spatial location and time reference during a single drop hammer impact test. Visible light images can be used to analyze surface morphology, crack propagation, and flame propagation; mid-wave and long-wave infrared images can capture high-temperature hotspots and near-room-temperature temperature rise regions, respectively, broadening the temperature measurement range; X-ray images can reveal structural evolution such as pore collapse and particle fragmentation within the material. The coaxially opposed upper and lower cavities (200mm structure), combined with built-in reflectors and a single-crystal diamond window, enable multi-wavelength optical paths to pass through the sample without interference within a limited space. The combination of multi-channel synchronous triggers and equal-length coaxial cables controls the timing matching error of the trigger signals of each device to the nanosecond level, far smaller than the μs-level timescale of energetic material ignition, ensuring strict alignment of multiphysics images on the time axis. This allows for quantitative analysis of the coupling relationship between surface deformation, temperature distribution, and internal structural changes. The application of narrowband filters effectively suppresses the interference of strong radiation in the reaction zone on infrared thermometry, while the pulsed X-ray source freezes the dynamic moment of the internal structure with nanosecond-level pulses, reducing motion blur.

[0041] In other technical solutions, the reflective element disposed in the upper cavity 100 is a silver-plated reflector 102, the silver-plated reflector 102 having a reflectivity of not less than 98% for the visible light band and the mid-wave infrared band; the reflective element disposed in the lower cavity 200 is a gold-plated reflector 202, the gold-plated reflector 202 having a reflectivity of not less than 99% for the mid-wave infrared band and the long-wave infrared band, and a reflectivity of not less than 85% for the visible light band.

[0042] In the above technical solution, a silver-plated plane mirror is installed inside the upper cavity 100. K9 optical glass with a thickness of 3mm to 5mm can be used as the substrate, with a silver reflective film coated on the surface and a magnesium fluoride protective layer added. Its reflectivity for the visible light and mid-infrared bands is not less than 98%. The silver-plated mirror 102 is fixed to the inner wall of the upper cavity 100 by a mirror frame. The normal of the mirror surface forms a 45° angle with the vertical direction, so that the light beam entering horizontally from the light source entrance is reflected and passes vertically downwards through the optical window 300 and the sample. The mirror is installed above and to the opposite side of the light source entrance, with the reflecting surface facing the incident light direction and the lower window. Its effective aperture is greater than 1.2 times the diameter of the incident beam to avoid beam interception.

[0043] A gold-plated plane mirror is installed inside the lower cavity 200. It can use a substrate of the same size and specifications as the upper mirror, with a gold reflective film and a protective layer deposited on its surface. This mirror has a reflectivity of no less than 99% for the mid-wave infrared and long-wave infrared bands, and no less than 85% for the visible light band. The gold-plated mirror 202 is also fixed to the inner wall of the lower cavity 200 by an adjustable frame. The mirror surface normal forms a 45° angle with the vertical direction. It receives the beam of light incident vertically from above and reflects it horizontally, exiting from the light outlet. The installation height of the lower cavity 200 mirror is lower than the lower surface of the lower optical window 302, with the reflecting surface facing the upper window and light outlet. Its position ensures that the converging or collimated beam of light after passing through the upper mirror, window, and sample falls completely within the effective area of ​​the reflecting surface.

[0044] Before installation, the actual reflectivity of the silver-plated reflector 102 and the gold-plated reflector 202 can be measured with a spectrophotometer to confirm that they meet the requirements in the target wavelength band. When cleaning the mirrors, anhydrous ethanol and optical lens paper can be used for gentle wiping to avoid scratching the coating. This configuration effectively controls the optical path transmission loss between the upper and lower cavities 200 for visible light, mid-wave infrared, and long-wave infrared. The silver reflector in the upper cavity 100 prioritizes efficiency in the short-wave band, while the gold reflector in the lower cavity 200 takes into account the high reflectivity requirements of long-wave infrared while maintaining usable reflectivity for visible light.

[0045] In other technical solutions, the upper optical window 301 and the lower optical window 302 are single-crystal diamond optical windows.

[0046] In the above technical solution, both the upper optical window 301 and the lower optical window 302 can be made of single-crystal diamond material, prepared by chemical vapor deposition, and are circular flat sheets with a diameter of 10 mm and a thickness of 1 mm. Both sides are polished and coated with a wide-band antireflective film. The impact resistance of this single-crystal diamond window is not less than 500 MPa. The edge of the diamond window can be pressed into the countersunk hole on the end face of the cavity by a metal pressure ring through an elastic sealing gasket. A thin polytetrafluoroethylene gasket is placed on the side of the pressure ring that contacts the window to avoid local stress concentration that could cause the window to crack.

[0047] The upper optical window 301 is installed in the countersunk hole at the center of the lower end face of the upper cavity 100, and the lower optical window 302 is installed in the corresponding countersunk hole at the upper end face of the lower cavity 200. The two are coaxially opposed. The test sample 800 is placed directly on the center of the upper surface of the lower optical window 302. When the hammer 101 falls, the upper window descends together with the upper cavity 100, pressing the sample between the two windows. The parallelism between the upper and lower windows can be ensured by grinding the end face of the cavity or by adding shims under the window seats. When using a parallelism measuring instrument, the parallelism deviation between the windows can be controlled within 5μm.

[0048] After repeated impact tests, the diamond window may develop surface microcracks or scratches. The surface condition of the window can be inspected with an optical microscope after each test, and a new window should be replaced when the defect density exceeds a preset threshold. This diamond window simultaneously meets the dual requirements of high transmittance across multiple wavelengths and resistance to strong drop hammer impacts, allowing four light paths—visible light, mid-infrared, long-infrared, and X-rays—to pass through the same pair of windows without damage and act on the sample.

[0049] In some other technical solutions, the infrared imaging unit 500 includes a mid-wave infrared high-speed camera and / or a long-wave infrared high-speed camera and an infrared beam splitter. The infrared beam splitter is disposed in the optical path between the mid-wave infrared high-speed camera and the long-wave infrared high-speed camera. The infrared beam splitter has transmittance in the 3μm to 5μm band and reflectivity in the 8μm to 14μm band, or the infrared beam splitter has reflectivity in the 3μm to 5μm band and transmittance in the 8μm to 14μm band.

[0050] In the above technical solution, the infrared imaging unit 500 first receives the infrared beam transmitted by the dichroic mirror 501 at the optical path entrance end, and the beam enters an infrared beam splitter. This infrared beam splitter can be made with a zinc selenide or germanium substrate coated with a beam-splitting film, which has high transmittance in the 3μm to 5μm wavelength band and high reflectivity in the 8μm to 14μm wavelength band. Alternatively, it can be configured to reflect mid-wave infrared and transmit long-wave infrared; both configurations are acceptable. A mid-wave infrared high-speed camera is placed on the transmitted light path after beam splitting, and a long-wave infrared high-speed camera is placed on the reflected light path. The mid-wave infrared high-speed camera can use a cooled mercury cadmium phosphorus focal plane detector with a pixel pitch of 15μm, an array size of 640×512 pixels, and a frame rate of no less than 500 frames per second in full frame mode; a higher frame rate can be achieved after windowing. The long-wave infrared high-speed camera can use an uncooled vanadium oxide microbolometer detector or a cooled quantum well detector, with a pixel pitch of 17μm, an array size of 640×480 pixels, and a frame rate of no less than 200 frames per second.

[0051] Both infrared cameras use electrically focused infrared lenses with apertures set to f / 2.0 or f / 2.5. They are mounted at the two optical path exits after beam splitting via adapter rings. A narrowband filter with a center wavelength of 3.9 μm can be mounted in front of the lens of the mid-wave infrared camera, while a narrowband filter with a center wavelength of 10.6 μm can be mounted in front of the lens of the long-wave infrared camera. The filters can be screwed in or inserted using filter wheels. The camera bodies are fixed to the optical platform using L-shaped brackets. Silicone rubber vibration damping pads can be installed between the brackets and the platform to reduce the impact of drop hammer vibrations on image quality.

[0052] The infrared beam splitter's mounting base employs an adjustable cage structure, allowing for both angle and position adjustments. This, combined with a laser collimator, adjusts the beam splitter's angle and position, aligning the transmitted and reflected beams with the entrance pupils of the two cameras, respectively. This configuration enables the simultaneous acquisition of temperature field information in both mid-wave and long-wave infrared bands during a single impact, expanding the temperature measurement range and covering both high-temperature hotspots and near-normal temperature rise areas.

[0053] In some other technical solutions, the X-ray imaging unit includes a scintillator 601, a reflector 602, and a black-and-white high-speed camera 600; X-rays that have penetrated the test sample 800 are incident on the scintillator 601, and the scintillator 601 converts the X-rays into visible light signals, which are then deflected by the reflector 602 and incident on the black-and-white high-speed camera 600.

[0054] In the above technical solution, the X-ray imaging unit is composed of a scintillator 601, a reflector 602, and a monochrome high-speed camera 600 in sequence. The scintillator 601 can be a cesium iodide columnar crystal screen, with an effective luminescent area of ​​50mm × 50mm and a thickness of approximately 200μm, deposited on a carbon fiber substrate or an aluminum substrate. It has high X-ray conversion efficiency and a spatial resolution down to the micrometer level. The scintillator 601 is installed in a dark box outside the X-ray exit window, with its luminescent surface facing the X-ray incident direction. It is positioned close to the beryllium plate behind the exit window, receiving X-rays that have penetrated the sample and generating a visible light fluorescence image. An aluminum-plated reflector 602 is placed behind the scintillator 601. The visible light reflecting surface size can be selected as 75mm × 75mm, and the installation angle is 45°. This deflects the optical axis of the fluorescence image by 90° before it enters the lens of the monochrome high-speed camera 600.

[0055] The monochrome high-speed camera 600 can employ a back-illuminated scientific-grade CMOS camera with a pixel size of approximately 6.5μm, an array size of 2048×2048 pixels, and a frame rate of no less than 100 frames per second at full frame rate. It features external triggering and high sensitivity, making it suitable for capturing weak fluorescence signals. The reflector 602 is rigidly fixed within the cassette. The cassette is constructed entirely of opaque aluminum alloy, with the inner walls coated with matte black paint to eliminate stray light. All seams are sealed with light-blocking strips. The cassette is bolted to a mounting flange on the outside of the X-ray exit window.

[0056] The camera body is mounted on an L-shaped bracket outside the dark box. By adjusting the camera position and lens focus, the luminescent surface of the scintillator 601 is imaged onto the target surface of the camera detector, resulting in a clear image. The geometric magnification ratio is set by changing the ratio of the distance from the X-ray source focal point to the sample to the distance from the sample to the scintillator 601, and can be selected as 2x or 3x. This configuration solves the problem of X-rays not being able to be directly recorded by means of the scintillator 601. The reflector 602 deflects the light path to prevent X-rays from directly irradiating the camera sensor, while the high sensitivity of the monochrome high-speed camera 600 is suitable for capturing weak light signals.

[0057] In other technical solutions, the visible light imaging unit includes a color high-speed camera 400 and a microscope lens 401, wherein the frame rate of the color high-speed camera 400 is not less than 1 million frames per second, and the spatial resolution of the color high-speed camera 400 is not less than 10 μm per pixel.

[0058] In the above technical solution, the visible light imaging unit receives the visible light beam reflected by the dichroic mirror 501. This beam first enters the microscope objective lens, which can be an infinity-corrected long working distance plan achromatic objective lens with a magnification of 5x or 10x, a numerical aperture of 0.14 or 0.25, and a working distance of approximately 34mm or 20mm to allow sufficient space for the cavity and window. The objective lens is then connected to the microscope tube lens, which converges the infinity-corrected beam onto the detector target surface of the color high-speed camera 400. The sensor of the color high-speed camera 400 can be a back-illuminated CMOS sensor with a pixel pitch of approximately 10μm, a frame rate of no less than 20,000 frames per second in full frame mode, and no less than 1 million frames per second when windowed to 256×256 pixels, supporting external triggering and segmented memory storage modes. The camera lens interface can be an F-type or C-type interface, connected to the microscope tube lens via an adapter ring.

[0059] The microscope objective, microscope tube lens, and high-speed color camera 400 are integrated via a cage-type coaxial mounting system. The entire assembly is fixed on a three-axis translation stage with an adjustment accuracy of no less than 5μm, used to precisely adjust the objective plane of the microscope to the impact surface of the test sample 800. The camera's data cable can be connected to the acquisition computer via high-speed fiber optic or Camera Link interface, achieving a data transfer rate of several gigabytes per second, storing image sequences captured at 1 million frames per second in real time into a high-speed solid-state drive array.

[0060] Before the experiment, the spatial resolution of the visible light imaging unit can be calibrated using a resolution chart to confirm that a linewidth of 10 μm can be resolved at the sample location. The field of view can be adjusted by selecting different magnification objectives; a 5x objective has a field of view of approximately 2 mm × 2 mm, and a 10x objective has a field of view of approximately 1 mm × 1 mm, depending on the sample size and the area of ​​interest. The camera exposure time can be set from 200 ns to 500 ns to match the pulse width of the light source, freezing high-speed motion with pulsed illumination. This configuration has a frame rate of no less than 1 million frames per second and a spatial resolution of no less than 10 μm per pixel, enabling the clear capture of micron-level details such as crack propagation, particle fragmentation, and flame morphology during energetic material impact.

[0061] In other technical solutions, the time resolution of the multi-channel synchronous trigger is not less than 1 ns; the trigger output terminal of the multi-channel synchronous trigger is connected to the visible light imaging unit, the infrared imaging unit 500, the X-ray imaging unit, and the multi-band light source module 701 via coaxial cables of equal length.

[0062] In the above technical solution, the core of the synchronous trigger module 700 is a multi-channel digital delay pulse generator with a time resolution of no less than 1 ns. It has one trigger input channel and at least six independent delay pulse output channels. The delay time of each channel can be independently set with a resolution of 1 ns. The amplitude of the output pulse is at 5V TTL level, and the pulse width can be set from 1 μs to 10 μs. The trigger input terminal of this synchronous trigger is connected to the trigger signal generation device, i.e., the position sensor, on the falling path of the hammer 101 via a coaxial cable. The six trigger output terminals are respectively connected to the pulse drive power supply of the multi-band light source module 701, the external trigger input of the visible light high-speed camera, the external trigger input of the mid-wave infrared high-speed camera, the external trigger input of the long-wave infrared high-speed camera, the external trigger input of the monochrome high-speed camera 600, and the trigger input of the pulsed X-ray source.

[0063] All cables connecting the synchronous trigger output to the trigger input of each device must be 50Ω characteristic impedance RG58 or RG174 coaxial cables of the same type, with a uniform length of 2m and an error controlled within 5mm. The transmission delay of each cable can be measured first using a network analyzer or time domain reflectometer to confirm that the difference in delay time between the six cables is less than 100ps. If it exceeds this, the cable should be replaced or the cable length should be fine-tuned.

[0064] The timing delay values ​​for each channel are set through the following steps: First, the average time interval from the laser beam from the interrupted position sensor to the impact surface of the sample is measured using an oscilloscope. This is repeated ten times, and the average value is taken as the reference time T0. Then, the delay T1 from receiving the trigger signal to actual emission of the multi-band light source module 701, the trigger response delays T2 to T5 of each camera, and the triggering and emission delay T6 of the X-ray source are measured respectively. These delay values ​​are input into the channel settings of the synchronization trigger. The trigger advance of the light source and camera is set to the difference between T0 and their respective delays. The triggering time of the X-ray source is set to a time in the μs range before and after T0, ultimately aligning the actual working times of all devices at the sample. The timing matching error of the output signals of each channel can be verified by actual measurement with a photodetector at the sample position using a multi-channel oscilloscope. The error value can be controlled to be less than 500 ns. This configuration improves the synchronization trigger accuracy from the conventional tens of μs to the ns level, providing hardware assurance for strict time alignment of multi-band images.

[0065] In other technical solutions, a narrowband filter is provided between the dichroic mirror 501 and the infrared imaging unit 500. The center wavelength of the narrowband filter is 3.9μm or 10.6μm, and the half-width at half maximum (WHM) of the narrowband filter is no greater than 200nm.

[0066] In the above technical solution, a narrowband filter is inserted into the optical path between the dichroic mirror 501 and the infrared imaging unit 500. This filter can be mounted on a rotatable filter wheel or a push-pull filter holder, which is fixed to a cage-like mounting tube connected to the transmission end of the dichroic mirror 501 via a threaded connection. The center wavelength of the narrowband filter can be selected as 3.9 μm or 10.6 μm, depending on the infrared band of interest. When a filter with a center wavelength of 3.9 μm is used, its half-width at half-maximum (HWHM) is no greater than 200 nm. This band is located within the atmospheric window of the mid-wave infrared and avoids the strong emission bands of water vapor and carbon dioxide in the reaction products of energetic materials, effectively suppressing the interference of flame radiation on temperature measurement. When a filter with a center wavelength of 10.6 μm is used, the HWHM is also kept to be no greater than 200 nm, corresponding to the long-wave infrared band, suitable for capturing the weak thermal radiation from the sample surface near room temperature, while filtering out broadband reactive luminescence.

[0067] The substrate of the filter can be made of sapphire, calcium fluoride, or zinc selenide, and a multilayer dielectric film is deposited on the surface to achieve bandpass filtering with a peak transmittance of not less than 70%. The filter is positioned in the optical path before the infrared beam splitter, so that the filtered beam is split into mid-wave and long-wave paths by the beam splitter.

[0068] Before installation, the actual transmittance curve of the filter can be measured using a Fourier transform infrared spectrometer to confirm that the center wavelength and full width at half maximum (FWHM) meet the specifications. After using a narrowband filter, the temperature measurement accuracy of the infrared camera can be verified by comparing the measurement results of a standard blackbody with and without the filter, ensuring that the temperature inversion error after filtering is within an acceptable range. This configuration effectively filters out the intense flame radiation and ambient stray light generated during the impact ignition of energetic materials, significantly improving the signal-to-noise ratio of the infrared image and the accuracy of temperature measurement.

[0069] In other technical solutions, the X-ray source is a synchrotron radiation X-ray source or a pulsed X-ray source, and the multi-channel synchronous trigger controls the X-ray source to emit X-ray pulses within a time window from 1 μs before the hammer 101 strikes the test sample 800 to 10 μs after the strike.

[0070] In the above technical solutions, when a pulsed X-ray tube is selected as the X-ray source, its pulse width is no greater than 100 ns, the tube voltage can be set within the range of 100 kV to 300 kV, the peak tube current can reach tens of amperes, and the focal spot size is approximately 0.5 mm × 0.5 mm to 1.0 mm × 1.0 mm. When a synchrotron radiation X-ray source is selected, the ns to picosecond level X-ray pulses naturally generated by the electron beam cluster in the storage ring can be utilized, which also meets the system's requirement for short-pulse imaging, and no additional pulse width control is required. The trigger interface of the X-ray source is connected to one output channel of the synchronous trigger module 700 via a coaxial cable of equal length to receive TTL trigger pulses. A collimator or aperture can be installed in front of the exit window of the X-ray source to limit the divergence angle of the X-ray beam, so that the irradiation area is concentrated within the sample size range, reducing the influence of stray scattered rays on the imaging quality. The distance between the X-ray source and the sample can be set between 200 mm and 500 mm, and the geometric magnification ratio and irradiation dose can be changed by adjusting the distance.

[0071] The synchronous triggering module 700 controls the X-ray source to emit X-ray pulses within a time window of 1 μs before and 10 μs after the hammer 101 impacts the test sample 800. For specific timing settings, the precise moment of impact can be determined first using high-speed photography and contact sensors, and then the triggering delay of the X-ray source can be set to 2 μs to 5 μs after the impact. This time window is chosen to account for the internal pore collapse and particle fragmentation that begin within μs after impact in energetic materials, allowing the emission of X-ray pulses to capture instantaneous images of the initial structural state or early damage. For pulsed X-ray tubes, a pulse width of 100 ns is sufficiently short compared to the speed of movement of the sample's internal structure to "freeze" the dynamic process and eliminate motion blur; for synchrotron radiation X-ray sources, the pulse width is even shorter (down to picoseconds), achieving or even surpassing this "freezing" effect.

[0072] Regardless of the type of X-ray source used, parameters such as tube voltage and tube current can be optimized based on the material density and thickness of the sample. For HMX-based or RDX-based energetic material tablets with a diameter of 5 mm and a thickness of 2 mm, if a pulsed X-ray tube is used, the tube voltage can be set to 150 kV to penetrate a material with a thickness of approximately 2 mm and ensure sufficient fluorescence brightness on the scintillator 601. If a synchrotron radiation X-ray source is used, its high brightness and good monochromaticity can be utilized to obtain higher contrast images at a lower dose. This configuration, using nanosecond (or picosecond) X-ray pulses in conjunction with precise time-delay triggering, achieves "frozen" imaging of the micron-level structural changes within the energetic material at the moment of impact, while simultaneously controlling the radiation dose received by the sample to a low level.

[0073] In other technical solutions, the present invention also discloses an observation method based on the multi-band optical synchronous observation system for the impact safety of the energetic material, comprising the following steps: The test sample 800 is placed on the lower optical window 302, so that the test sample 800 is located between the upper optical window 301 and the lower optical window 302; The dropping hammer loading module is activated to release the hammer 101. The trigger signal generating device generates a trigger signal when the hammer 101 falls to the predetermined position before impact and sends the trigger signal to the trigger input terminal of the synchronous trigger module 700. The synchronous trigger module 700 receives the trigger signal and outputs trigger signals to the multi-band light source module 701, the visible light imaging unit, the infrared imaging unit 500, and the X-ray imaging unit respectively through the multiple trigger output terminals according to a preset timing delay. The preset timing delay is configured such that the emission time of the multi-band light source module 701, the exposure time of the visible light imaging unit, the exposure time of the infrared imaging unit 500, and the exposure time of the X-ray imaging unit all match the time when the hammer 101 hits the test sample 800, and the timing matching error between each trigger signal is less than 500ns. After receiving a trigger signal, the multi-band light source module 701 outputs multi-band light. The multi-band light enters the upper cavity 100 through the light source entrance port, is reflected by the reflective element, and then passes vertically through the upper optical window 301, the test sample 800, and the lower optical window 302. After entering the lower cavity 200, it is reflected by the reflective element to the light exit port. The multi-band light emitted from the light exit port is split by the dichroic mirror 501 and then enters the visible light imaging unit and the infrared imaging unit 500 respectively. The visible light imaging unit acquires a visible light image sequence, and the infrared imaging unit 500 acquires a mid-wave infrared image sequence and a long-wave infrared image sequence. After receiving a trigger signal, the X-ray source outputs an X-ray pulse. The synchronous triggering module 700 controls the pulsed X-ray source to emit an X-ray pulse with a pulse width of no more than 100 ns within a time window from 1 μs before the hammer 101 strikes the test sample 800. The X-ray pulse penetrates the test sample 800 through the X-ray incident window and exits from the X-ray exit window. The exited X-ray is converted and then enters the X-ray imaging unit to be acquired as an X-ray image sequence.

[0074] In the above technical solution, the test sample 800 is placed at the center of the upper surface of the lower optical window 302, and its position is adjusted so that it is within the projection area directly below the upper optical window 301. The dropping hammer loading module is activated to release the hammer 101, and the upper cavity 100 falls along the guide rail with the hammer 101. During the fall of the hammer 101, its lower end face blocks the laser beam when it passes the position sensor, and the sensor generates a trigger signal and sends it to the synchronous trigger module 700. After receiving the trigger signal, the synchronous trigger module 700 sends TTL trigger pulses to the multi-band light source module 701, the visible light imaging unit, the infrared imaging unit 500, and the X-ray imaging unit respectively through multiple trigger output terminals according to a preset time delay. The timing matching error between each trigger signal is controlled to be less than 500ns.

[0075] Upon receiving a trigger signal, the multi-band light source module 701 outputs pulsed illumination light. The beam enters the upper cavity 100 through the light source entrance and is reflected by the reflective element. It then passes vertically through the upper optical window 301, the test sample 800, and the lower optical window 302, enters the lower cavity 200, and is reflected again by the reflective element to exit through the light outlet. After being split by the dichroic mirror 501, the light enters the visible light imaging unit and the infrared imaging unit 500, respectively. Visible light image sequences, mid-wave infrared image sequences, and long-wave infrared image sequences are simultaneously acquired by each camera. Simultaneously, upon receiving the trigger signal, the X-ray source emits X-ray pulses with a pulse width of no more than 100 ns within a time window from 1 μs before to 10 μs after the hammer 101 strikes the sample. After penetrating the sample, the X-rays are converted and enter the X-ray imaging unit, where X-ray images are acquired by the black-and-white high-speed camera 600.

[0076] This method simultaneously acquires image data from four channels in a single drop hammer test. The visible light image sequence can be used for digital image correlation analysis to obtain displacement and strain fields, while the infrared image sequence can be used to invert the temperature field after radiometric calibration. X-ray images, after processing, can extract information on internal pores and cracks. The synchronous trigger module 700 controls the start-up time of each device with nanosecond-level precision, ensuring that the timing error is less than the μs-level hotspot generation time of energetic materials. This guarantees strict alignment of the multiphysics images on the time axis, enabling coupled analysis of deformation, temperature rise, and structural evolution. Pulsed X-rays are emitted within a narrow window at the moment of impact, freezing the instantaneous state of the internal structure and reducing motion blur.

[0077] In other technical solutions, spatiotemporal fusion of the visible light image sequence, the mid-wave infrared image sequence, the long-wave infrared image sequence, and the X-ray image sequence includes: mapping the mid-wave infrared image sequence, the long-wave infrared image sequence, and the X-ray image sequence frame by frame to the image coordinate system of the visible light imaging unit using a pre-established spatial mapping relationship, and aligning each frame of the visible light image sequence, the mid-wave infrared image sequence, the long-wave infrared image sequence, and the X-ray image sequence to the same time reference on the time axis according to the pre-measured relative response delay of each imaging unit, thereby obtaining a spatiotemporally aligned multi-band data sequence; The collaborative analysis of the spatiotemporally aligned multi-band data sequence includes at least the following: identifying hot spot regions on the surface of the test sample 800 based on temperature field data obtained after temperature calibration of mid-wave infrared and long-wave infrared images; mapping the positions of the hot spot regions to visible light images through spatial mapping to obtain the spatial correspondence between the hot spot regions and crack features in the visible light images; and determining the time of internal crack initiation in the X-ray image sequence, determining the time of surface hot spot appearance in the temperature field data, and calculating the time difference between the time of internal crack initiation and the time of surface hot spot appearance.

[0078] In the above technical solution, before carrying out spatiotemporal fusion, the spatial mapping relationship of each imaging unit is first established. A calibration plate with a checkerboard or dot array can be placed at the sample position of the lower optical window 302. The calibration plate pattern can be imaged in the visible light, infrared, and X-ray bands. For the infrared band, the calibration plate can be preheated to a state higher than the background temperature, so that the pattern is clearly visible in the mid-wave and long-wave infrared cameras. For the X-ray band, a pattern of metal sheet inlay can be processed on the calibration plate, and the difference in the material's absorption rate of X-rays is used to form a contrast on the scintillator 601. Images of the calibration plate are captured by a visible light high-speed camera, a mid-wave infrared high-speed camera, a long-wave infrared high-speed camera, and an X-ray imaging unit, respectively. The coordinates of feature points in each image are extracted. Using the visible light image coordinate system as the reference coordinate system, the geometric transformation parameters from the infrared image and X-ray image to the visible light image coordinate system are calculated by solving the homography matrix or using a polynomial distortion model, thus completing the calibration of the spatial mapping relationship.

[0079] The relative response delay of each imaging unit can be measured in the system's overall state. A fast-response photodetector is placed at the sample position, and the synchronous trigger module 700 simultaneously triggers the light source and all cameras. A multi-channel oscilloscope is used to record the arrival time of the light source's emission pulse and the moment of the first exposure midpoint after each camera's shutter opens. The difference between the exposure midpoint time of each camera and the arrival time of the light source pulse is the relative response delay of that camera. For the X-ray imaging unit, a scintillator 601 detector can be used instead of a photodetector, recording the difference between the arrival time of the X-ray pulse and the exposure midpoint time of the black-and-white camera. The delay values ​​of each imaging unit are stored in the data processing software as compensation parameters for time alignment.

[0080] After the formal experiment was completed, visible light image sequences, mid-wave infrared image sequences, long-wave infrared image sequences, and X-ray image sequences were obtained. First, each frame of the mid-wave infrared, long-wave infrared, and X-ray images was transformed pixel-by-pixel to the visible light image coordinate system using spatial mapping relationships. During the transformation, bilinear or bicubic interpolation was used to maintain image quality, resulting in spatially aligned multi-band images. Then, based on the relative response delay of each imaging unit and using the exposure time of the visible light image as a reference, each frame of the infrared and X-ray images was shifted and compensated on the time axis, ensuring that the four images acquired at the same time are strictly corresponding in time, forming a spatiotemporally aligned multi-band data sequence.

[0081] During collaborative analysis, the mid-wave infrared and long-wave infrared images are first calibrated for temperature. Using the grayscale-temperature correspondence pre-measured with a standard blackbody, the grayscale values ​​of the infrared images are converted into temperature values, yielding temperature field data for the sample surface. Hotspot regions are identified within the temperature field data by setting a temperature threshold. This threshold can be a fixed difference above the sample's average temperature or an adaptive threshold algorithm. The identified hotspot region contours are superimposed onto the visible light image using a spatial mapping relationship. The presence of crack features in this region is observed in the visible light image. Crack features can be extracted using edge detection or image segmentation algorithms, thus determining the spatial correspondence between hotspots and cracks. In the X-ray image sequence, the frame number of internal crack initiation is detected using inter-frame difference or image subtraction methods, and the timestamp corresponding to that frame is taken as the internal crack initiation time. In the temperature field data, the temperature change curve of each pixel over time is monitored, and the moment when the temperature rise rate exceeds a preset threshold is taken as the appearance time of the surface hotspot. The time difference between the internal crack initiation time and the appearance time of the surface hotspot is calculated to obtain their temporal relationship.

[0082] Multi-band imaging units have different fields of view, resolutions, and imaging orientations in space. Differences in signal transmission paths and device response characteristics between each camera, X-ray source, and synchronization trigger mean that the synchronization trigger signal cannot completely eliminate minor time deviations between channels. The basic principle of spatiotemporal fusion is to first establish spatial coordinate transformation relationships between images from different bands through geometric calibration, unifying images from different optical paths into the same coordinate system and eliminating spatial misalignment; then, by measuring the relative response delay of each imaging link, the images of each frame are translated and compensated on the time axis to eliminate timing deviations. This process enables multi-source image data that are not entirely consistent in space and time to correspond pixel-by-pixel and frame-by-frame within a unified framework.

[0083] The collaborative analysis is based on the strong coupling physical mechanism between deformation, temperature rise, and internal structural damage during the impact ignition of energetic materials. The initiation of internal cracks is often accompanied by local stress release and the conversion of plastic work into heat, potentially forming hotspots near the crack surface; conversely, thermal softening caused by local temperature rise may also promote crack propagation. By spatially mapping and comparing the locations of hotspots in the temperature field with cracks in visible light images, we can provide a basis for determining whether hotspots are the cause or consequence of cracking. By determining the times of internal crack initiation and surface hotspot appearance on the time axis and calculating the time difference, we can quantitatively describe the temporal relationship between damage and temperature rise, providing data support for revealing the dominant ignition mechanism.

[0084] This method eliminates image misalignment caused by spatial field-of-view differences and relative response delays among imaging units by spatiotemporally fusing image sequences from four channels: visible light, mid-infrared, long-infrared, and X-ray. It obtains multi-band data frame-by-frame and pixel-by-pixel under a unified coordinate system and time reference. Based on this, collaborative analysis maps hotspot regions in the temperature field to visible light images, intuitively demonstrating the spatial correlation between hotspots and cracks. By calculating the time difference between internal crack initiation and surface hotspot appearance, the temporal relationship between internal material damage and surface temperature rise is quantitatively revealed. These analytical results provide direct spatiotemporal evidence for determining the main mechanisms of hotspot formation during impact ignition of energetic materials. They help distinguish between different ignition modes, such as hotspots caused by stress concentration, friction, or shear bands, thus providing more physically grounded guidance for assessing the impact sensitivity of energetic materials and optimizing formulation design.

[0085] In other technical solutions, the pre-established spatial mapping relationship is obtained through the following steps: a multi-band calibration target with grid-like feature marks is placed on the lower optical window 302, and the synchronous triggering module 700 synchronously triggers each imaging unit to acquire calibration images; the sub-pixel coordinates of the feature marks are extracted, and the homography matrix of the mid-wave infrared high-speed camera, the long-wave infrared high-speed camera, and the X-ray imaging unit to the reference is calculated using the visible light image coordinate system as a reference, thus forming the spatial mapping relationship. The pre-measured relative response delay of each imaging unit is obtained through the following steps: using a standard pulse light source with a pulse width of less than 10 ns to simultaneously incident on the optical path of each imaging unit, the time difference between the arrival time of the trigger signal and the arrival time of the exposure indication signal of each imaging unit is measured using a high-speed oscilloscope to obtain the response delay of each imaging unit, and the relative response delay of each imaging unit is calculated based on the response delay of the visible light imaging unit. The temperature calibration is obtained through the following steps: a standard blackbody radiation source is set at the lower optical window 302, and the standard blackbody radiation source is stabilized at multiple temperature points. Images at each temperature point are acquired using the mid-wave infrared high-speed camera and the long-wave infrared high-speed camera, and the average gray value of the central region is extracted to establish mid-wave infrared gray-temperature calibration curves and long-wave infrared gray-temperature calibration curves. In the formal experiment, the gray values ​​of the mid-wave infrared image and the long-wave infrared image are converted into temperature values ​​through the calibration curves to obtain the temperature field data. The determination of the moment of internal crack initiation in the X-ray image sequence includes: identifying pixels in the X-ray image whose grayscale value differs from the average grayscale value of the sample area before impact by more than 20% to 80% of the average grayscale value as crack initiation pixels, and recording the moment corresponding to the first X-ray image showing the crack initiation pixel as the moment of internal crack initiation; the determination of the moment of surface hotspot appearance in the temperature field data includes: identifying pixel areas whose temperature value exceeds the average temperature of the sample area before impact by 1.1 to 2.5 times as hotspot areas, and recording the moment corresponding to the first image showing the hotspot area as the moment of surface hotspot appearance. The collaborative analysis also includes: calculating the true temperature value of the hotspot area using a dual-band ratio thermometry method based on the mid-wave infrared temperature and long-wave infrared temperature at the same pixel location, eliminating the influence of unknown emissivity on single-band thermometry.

[0086] In the above technical solution, establishing the spatial mapping relationship first requires the fabrication of a multi-band calibration target. This calibration target can be placed on a single-crystal diamond substrate with a thickness of approximately 1 mm. The multi-band calibration target is positioned on the upper surface of the lower optical window 302, between the upper and lower windows. The synchronous triggering module 700 synchronously triggers the visible light high-speed camera, mid-wave infrared high-speed camera, long-wave infrared high-speed camera, and X-ray imaging unit to acquire one frame of calibration image each. For infrared imaging, the calibration target can be preheated slightly to a temperature slightly higher than the ambient temperature, creating a radiation difference between the grid area and the non-grid area. The sub-pixel coordinates of the grid intersections in each image are extracted using Harris corner detection or a sub-pixel localization algorithm based on local gray-scale moments to obtain the coordinates of at least 20 feature points in each channel. Using the visible light image coordinate system as the reference coordinate system, the coordinates of feature points in the mid-wave infrared, long-wave infrared, and X-ray images are matched with their corresponding points in the visible light image. The homography matrix from each channel to the reference coordinate system is solved using the direct linear transformation method. This matrix contains parameters for rotation, translation, scaling, and perspective transformation. The obtained homography matrix is ​​stored as a spatial mapping parameter file, which can be directly used in subsequent image processing.

[0087] The relative response delay of each imaging unit can be measured in a darkroom environment. A standard pulsed light source with a pulse width of less than 10 ns is prepared; this can be a gain-switched picosecond laser diode or a fast-edge LED driver module, with output light wavelengths covering the visible to infrared bands. The emitted light from the pulsed light source is simultaneously coupled into the optical path entrances of the visible light imaging unit, the mid-wave infrared imaging unit, and the long-wave infrared imaging unit via an optical fiber beam splitter or diffuser. For the X-ray imaging unit, a fast X-ray flash tube needs to be triggered by the pulsed light source, or a pulsed light source needs to be placed in front of the scintillator 601 to simulate the arrival time of the X-ray. Using a multi-channel high-speed oscilloscope with a bandwidth of at least 1 GHz, after the synchronous trigger module 700 emits a single trigger pulse, the oscilloscope records the rising edge times of the signals in each channel. Using the arrival time of the exposure indication signal of the visible light imaging unit as a reference, the time difference between the mid-wave infrared camera, the long-wave infrared camera, and the X-ray imaging unit is calculated, which is the relative response delay of each imaging unit. The measurement is repeated ten times, and the average value is taken. The delay value is then written into the channel compensation parameters of the synchronous trigger module 700.

[0088] Temperature calibration was completed before the formal experiment. A standard blackbody radiation source was placed at position 302 in the lower optical window. The radiation aperture of the blackbody radiation source could be selected as 5mm, with a temperature control range covering 300K to 2000K and a temperature control accuracy better than 0.5K. Several temperature points were sequentially set for the blackbody temperature. After each temperature point stabilized, 100 frames of images were acquired using a mid-wave infrared high-speed camera and a long-wave infrared high-speed camera, respectively. The grayscale values ​​of 50×50 pixels in the central region of each frame were averaged over time and spatially to obtain the average grayscale value at that temperature point. The average grayscale value at each temperature point was fitted to the corresponding blackbody temperature. Mid-wave infrared grayscale temperature calibration curves and long-wave infrared grayscale temperature calibration curves could be established using a quadratic polynomial or a simplified form of Planck's formula. The integration time, aperture, and filter configuration used for the infrared cameras during calibration remained consistent with those used in the formal experiment.

[0089] After obtaining a spatiotemporally aligned multi-band data sequence for the formal experiment, the moment of internal crack initiation was determined from the X-ray image sequence. First, an X-ray image frame before impact was selected as the baseline image, and the average gray value G0 within the sample area was calculated. For each subsequent X-ray image frame, the difference between the gray value G and G0 was calculated pixel-by-pixel. Pixels with a difference exceeding 20% ​​to 80% of G0 were identified as crack initiation pixels. The lower limit of this threshold range was used to filter out noise and minute density changes, while the upper limit was used to exclude completely fractured areas. When a group of crack initiation pixels with a continuous area larger than a preset area first appeared in a frame, the corresponding time of that frame was recorded as the moment of internal crack initiation.

[0090] The timing of surface hotspot appearance is determined from the temperature field data. The average temperature T0 of the sample region before impact is taken as the reference temperature. For the temperature field obtained by inversion from mid-wave infrared or long-wave infrared, each pixel is checked to determine whether the temperature value exceeds 1.1 to 2.5 times T0. The lower limit of 1.1 times is used to exclude normal temperature rise fluctuations, and the upper limit of 2.5 times is used to exclude inversion anomalies caused by flame radiation interference. Pixel regions that meet this temperature threshold condition are marked as hotspot regions. When a hotspot region with an area larger than a preset area first appears in a frame, the corresponding time in that frame is recorded as the time of surface hotspot appearance.

[0091] In collaborative analysis, the dual-band ratio thermometry method is used to calculate the true temperature value of hotspot regions. For the same spatially corresponding pixel location, the brightness temperature T is obtained from the mid-wave infrared temperature field data. mw Brightness temperature T is obtained from long-wave infrared temperature field data. lwLet the operating wavelength of the mid-wave infrared camera be λ1 and the operating wavelength of the long-wave infrared camera be λ2. The emissivity ratio of the energetic material sample in the two bands can be approximated as 1. The true temperature T is calculated using the dual-band ratio thermometry formula, obtaining the true temperature value that eliminates the influence of emissivity. The calculated true temperature is then superimposed onto the visible light image in the form of a pseudo-color map to visually display the temperature distribution and magnitude of the hotspot region.

[0092] The spatial mapping relationship is established based on the homography mapping principle in multi-view geometry. Each imaging unit images the same planar target from different directions. Since both the sample and the calibration target are placed on the optical window plane, this plane can be approximated as a two-dimensional plane. The images formed by different cameras on this plane satisfy the planar homography transformation relationship. The homography matrix can be solved by at least four sets of non-collinear feature point pairs, and the images of each channel are uniformly mapped to the visible light image coordinate system.

[0093] The measurement principle of relative response delay is based on the time difference between signal transmission and device response. The arrival time of the electrical pulse emitted by the synchronous trigger at each camera trigger port varies slightly due to differences in cable length and interface circuitry. The electronic delay from receiving the trigger signal to the shutter fully opening or beginning exposure also differs for each camera. By simulating the arrival time of the light signal using a pulsed light source and directly measuring the time difference between the electrical signal and the light response signal with an oscilloscope, the total delay of the entire signal link can be accurately obtained, thus compensating for it in the trigger timing.

[0094] Temperature calibration is based on the blackbody radiation law, which states that there is a definite relationship between the spectral radiative exitance of a standard blackbody and its temperature. The grayscale value output by the infrared camera detector is linearly related to the received radiant flux within a certain range. By establishing a grayscale-temperature correspondence curve through multi-temperature point measurements, the temperature value can be retrieved from the grayscale value during actual measurements.

[0095] Crack initiation is determined based on changes in grayscale values ​​in X-ray images. Before impact, energetic materials have a relatively homogeneous internal structure, and after X-ray penetration, the grayscale values ​​concentrate within a certain range. Crack formation indicates a local decrease in material density, reduced X-ray attenuation, and increased intensity reaching the scintillator 601, corresponding to an increase in image grayscale values. By setting a threshold for the change in grayscale value relative to a baseline, the crack region can be segmented from the background.

[0096] Hot spot identification is based on the temperature threshold method. Before impact, the sample is at room temperature with a relatively uniform temperature field. After impact, the temperature rises in local areas due to the conversion of plastic work into heat or the release of heat from chemical reactions. If the temperature rise exceeds the normal fluctuation range, it is identified as a hot spot.

[0097] The dual-band ratio thermometry method is based on the gray body approximation assumption. When the ratio of the emissivity of the sample surface in two different bands is known or approximately 1, the brightness temperatures measured in the two bands can be solved simultaneously to obtain the true temperature, which is unaffected by the absolute value of the emissivity. This method overcomes the difficulty of accurately obtaining the true temperature in single-band thermometry due to the unknown material emissivity.

[0098] By employing a grid-like multi-band calibration target and solving the homography matrix, a spatial mapping relationship was established between visible light, mid-infrared, long-infrared, and X-ray images, achieving precise spatial alignment of images at the pixel level across different bands. A standard pulsed light source with a pulse width of less than 10 ns, combined with a high-speed oscilloscope, precisely measured the relative response delay of each imaging unit, providing accurate compensation parameters for time axis alignment and eliminating timing deviations caused by differences in device response. Gray-scale temperature calibration of a standard blackbody radiation source at multiple temperature points provided reliable data curves for temperature inversion from infrared images, ensuring the accuracy of the temperature field data.

[0099] In the collaborative analysis, crack initiation pixels in X-ray images were identified by setting a threshold of 20% to 80% grayscale difference, and hotspot regions were identified by setting a threshold of 1.1 to 2.5 times the baseline temperature. The moment of first appearance was recorded, quantitatively obtaining the starting time points of internal damage and surface temperature rise. Calculating the time difference between these two moments reveals the temporal relationship between internal cracks and surface hotspots, providing direct evidence for determining the dominant ignition mechanism. The dual-band ratiometric thermometry method utilizes temperature data from both medium-wave and long-wave channels to eliminate the influence of emissivity, obtaining the true temperature value of the hotspot region and avoiding temperature measurement errors caused by unknown or changing surface emissivity of energetic materials. The entire spatiotemporal fusion and collaborative analysis process fully integrates and utilizes multi-band image data, advancing the coupling relationship between macroscopic deformation, temperature distribution, and internal structural evolution from qualitative observation to quantitative analysis, providing a systematic data processing method for studying the impact ignition mechanism of energetic materials.

[0100] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A multi-band optical synchronous observation system for the impact safety of energetic materials, characterized in that, It includes a falling weight loading module, a falling weight cavity, an optical window, a multi-band light source module, an X-ray source, a visible light imaging unit, an infrared imaging unit, an X-ray imaging unit, and a synchronous triggering module; The falling hammer loading module includes a hammer body and a trigger signal generating device for detecting the falling of the hammer body. The trigger signal generating device is a position sensor set on the falling path of the hammer body, which is used to generate a trigger signal when the hammer body falls to a predetermined position before impact. The drop hammer cavity includes an upper cavity rigidly connected to the hammer body and a lower cavity fixed to the base. The upper cavity and the lower cavity are coaxially opposite each other. A reflective element is installed inside the upper cavity. A light source inlet and an X-ray inlet window are opened on the side wall of the upper cavity. An upper optical window is installed on the lower end face of the upper cavity. A reflective element is installed inside the lower cavity. A light outlet and an X-ray outlet window are opened on the side wall of the lower cavity. A lower optical window is installed on the upper end face of the lower cavity. The sample to be tested is placed between the upper and lower optical windows and supported by the lower optical window. The output light of the multi-band light source module enters the upper cavity through the light source inlet, and after being reflected by the reflective element, it passes vertically through the upper optical window, the test sample and the lower optical window. After entering the lower cavity, it is reflected by the reflective element to the light outlet and emitted. The emitted light is split by the dichroic mirror and then enters the visible light imaging unit and the infrared imaging unit respectively. The X-rays output from the X-ray source penetrate the sample to be tested through the X-ray incident window and exit through the X-ray exit window. The exited X-rays are converted and then enter the X-ray imaging unit. The synchronous triggering module is a multi-channel synchronous trigger. Its trigger input is connected to a trigger signal generator, and its trigger output is connected to a multi-band light source module, a visible light imaging unit, an infrared imaging unit, and an X-ray imaging unit according to a preset timing delay. The preset timing delay is configured to match the start-up time of each imaging unit and light source module with the event of the hammer impacting the test sample. The timing matching error between the trigger signals output by the multi-channel synchronous trigger is less than the time scale of the energetic material ignition process.

2. The multi-band optical synchronous observation system for the impact safety of energetic materials as described in claim 1, characterized in that, The reflective element disposed in the upper cavity is a silver-plated reflector, and the silver-plated reflector has a reflectivity of not less than 98% for the visible light band and the mid-wave infrared band; the reflective element disposed in the lower cavity is a gold-plated reflector, and the gold-plated reflector has a reflectivity of not less than 99% for the mid-wave infrared band and the long-wave infrared band, and a reflectivity of not less than 85% for the visible light band.

3. The multi-band optical synchronous observation system for the impact safety of energetic materials as described in claim 1, characterized in that, The upper optical window and the lower optical window are single-crystal diamond optical windows.

4. The multi-band optical synchronous observation system for the impact safety of energetic materials as described in claim 1, characterized in that, The infrared imaging unit includes a mid-wave infrared high-speed camera and / or a long-wave infrared high-speed camera and an infrared beam splitter. The infrared beam splitter is disposed in the optical path between the mid-wave infrared high-speed camera and the long-wave infrared high-speed camera. The infrared beam splitter has transmittance in the 3μm to 5μm band and reflectivity in the 8μm to 14μm band, or the infrared beam splitter has reflectivity in the 3μm to 5μm band and transmittance in the 8μm to 14μm band.

5. The multi-band optical synchronous observation system for the impact safety of energetic materials as described in claim 1, characterized in that, The X-ray imaging unit includes a scintillator, a reflector, and a black-and-white high-speed camera; X-rays that have penetrated the test sample are incident on the scintillator, which converts the X-rays into visible light signals, and the visible light signals are deflected by the reflector and then incident on the black-and-white high-speed camera.

6. The multi-band optical synchronous observation system for the impact safety of energetic materials as described in claim 1, characterized in that, The visible light imaging unit includes a color high-speed camera and a microscope lens. The frame rate of the color high-speed camera is not less than 1 million frames per second, and the spatial resolution of the color high-speed camera is not less than 10 μm per pixel.

7. The multi-band optical synchronous observation system for the impact safety of energetic materials as described in claim 1, characterized in that, The time resolution of the multi-channel synchronous trigger is not less than 1 ns; the trigger output terminal of the multi-channel synchronous trigger is connected to the visible light imaging unit, the infrared imaging unit, the X-ray imaging unit and the multi-band light source module through coaxial cables of equal length.

8. The multi-band optical synchronous observation system for the impact safety of energetic materials as described in claim 1, characterized in that, A narrowband filter is disposed between the dichroic mirror and the infrared imaging unit. The center wavelength of the narrowband filter is 3.9 μm or 10.6 μm, and the full width at half maximum (FWHM) of the narrowband filter is no greater than 200 nm.

9. The multi-band optical synchronous observation system for the impact safety of energetic materials as described in claim 1, characterized in that, The X-ray source is a synchrotron radiation X-ray source or a pulsed X-ray source. The multi-channel synchronous trigger controls the X-ray source to emit X-ray pulses within a time window from 1 μs before the hammer strikes the test sample to 10 μs afterward.

10. An observation method based on the multi-band optical synchronous observation system for energetic material impact safety as described in any one of claims 1-9, characterized in that, Includes the following steps: The test sample is placed on the lower optical window, so that the test sample is located between the upper optical window and the lower optical window; The dropping hammer loading module is activated to release the hammer body. The trigger signal generating device generates a trigger signal when the hammer body falls to the predetermined position before impact and sends the trigger signal to the trigger input terminal of the synchronous trigger module. The synchronous triggering module receives the trigger signal and outputs trigger signals to the multi-band light source module, the visible light imaging unit, the infrared imaging unit, and the X-ray imaging unit respectively through the multiple trigger output terminals according to a preset timing delay. The preset timing delay is configured to match the emission time of the multi-band light source module, the exposure time of the visible light imaging unit, the exposure time of the infrared imaging unit, and the exposure time of the X-ray imaging unit with the time when the hammer hits the test sample, and the timing matching error between each trigger signal is less than 500ns. After receiving a trigger signal, the multi-band light source module outputs multi-band light. The multi-band light enters the upper cavity through the light source entrance, is reflected by the reflective element, and then passes vertically through the upper optical window, the test sample, and the lower optical window. After entering the lower cavity, it is reflected by the reflective element to the light exit port. The multi-band light emitted from the light exit port is split by the dichroic mirror and then enters the visible light imaging unit and the infrared imaging unit respectively. The visible light imaging unit acquires a visible light image sequence, and the infrared imaging unit acquires a mid-wave infrared image sequence and a long-wave infrared image sequence. After receiving a trigger signal, the X-ray source outputs an X-ray pulse. The synchronous triggering module controls the X-ray source to emit an X-ray pulse with a pulse width of no more than 100 ns within a time window from 1 μs before the hammer strikes the test sample. The X-ray pulse penetrates the test sample through the X-ray incident window and exits from the X-ray exit window. The exited X-ray is converted and then enters the X-ray imaging unit to be acquired as an X-ray image sequence.

Images