Dual-sensitivity multi-frame ultrafast velocity measurement imaging system and method

Abstract

The invention belongs to the technical field of imaging, and discloses a dual-sensitivity multi-frame ultrafast speed measurement imaging system and method. The system provided by the invention comprises a double-sensitivity multi-frame ultrafast speed measurement imaging unit and an information processing unit, the double-sensitivity multi-frame ultrafast velocity measurement imaging unit is combined with an imaging device with time domain shaping and space domain shaping and a double-sensitivity interference measurement device and is used for obtaining an interference pattern under double sensitivity; and the information processing unit is used for obtaining two-dimensional velocity field information according to the interference pattern under the double sensitivity. According to the invention, two-dimensional velocity field information at multiple moments under double sensitivities can be obtained through a single time, the experiment efficiency and the data credibility are improved, and the velocity measurement accuracy is also improved.

Description

Technical Field

[0001] The present invention belongs to the field of imaging technology, and more specifically, relates to a dual-sensitivity multi-frame ultrafast speed measurement imaging system and method. Background Art

[0002] Laser interferometry velocimetry is an imaging method that extracts velocity information based on the variations in interference fringes. It offers the advantages of non-contact measurement and does not interfere with the target's motion. It also significantly improves the temporal and spatial resolution of measurements, enabling the measurement of the velocity of shock wave interfaces. It holds significant theoretical significance and broad application prospects in a wide range of research fields, including fluid mechanics, materials science, and aerospace.

[0003] However, due to the current development status of recording devices, existing optical diagnostic methods can only obtain two-dimensional velocity field information at a certain moment. For the evolution of the velocity field, multiple times are required to obtain the two-dimensional velocity field distribution at multiple moments, which has certain defects in experimental efficiency and data credibility.

[0004] In addition, the limitation of the detection instrument's response speed may make it impossible for the detection instrument to distinguish the number of stripes that have moved at the moment the target starts to move, resulting in the loss of an integer number of stripes, which in turn affects the accuracy of speed measurement. Summary of the Invention

[0005] The present invention provides a dual-sensitivity multi-frame ultrafast speed measurement imaging system and method to solve the problems in the prior art of being unable to obtain two-dimensional speed field information at multiple moments through a single shot and the need to improve the accuracy of speed measurement.

[0006] The present invention provides a dual-sensitivity multi-frame ultrafast speed measurement imaging system, comprising: a dual-sensitivity multi-frame ultrafast speed measurement imaging unit and an information processing unit; the dual-sensitivity multi-frame ultrafast speed measurement imaging unit is combined with an imaging device with time domain shaping and space domain shaping and a dual-sensitivity interferometry measurement device, the dual-sensitivity multi-frame ultrafast speed measurement imaging unit is used to obtain an interference pattern under dual sensitivity; the information processing unit is used to obtain two-dimensional velocity field information under dual sensitivity based on the interference pattern under dual sensitivity.

[0007] Preferably, the dual-sensitivity multi-frame ultrafast speed measurement imaging unit includes a femtosecond laser, a time domain shaping module, a first beam splitter, a first optical combination, a second optical combination, a third beam combiner, a first beam splitter, an objective lens, a first lens, a fourth beam splitter, a first interference detection combination, and a second interference detection combination; The femtosecond laser is used to generate femtosecond pulses; the time domain shaping module is used to perform time domain stretching on the femtosecond pulses to obtain broadened chirped pulses; the first beam splitter is used to split the chirped pulses into S-polarized light and P-polarized light; the first optical assembly is used to split the S-polarized light into two sub-pulses and combine them after forming a time difference of t1 to obtain a first combined light beam; the second optical assembly is used to split the P-polarized light into two sub-pulses and combine them after forming a time difference of t2 to obtain a second combined light beam; the third beam combiner is used to combine the first combined light beam and the second combined light beam to obtain a third combined light beam; The third combined light beam passes through the first beam splitter and is incident on the objective lens. The light beam is converged on the sample after passing through the objective lens. The sample, after passing through the ultrafast event, reflects the light beam back to the objective lens, and then passes through the first beam splitter and is incident on the first lens. The signal light of the ultrafast event is collected and collimated by the first lens. The fourth optical splitter is used to split the collimated signal light into polarized light S' and polarized light P'; the first interference detection combination is used to split the S' polarized light into two sub-pulses and combine them after forming a time difference t1', and interfere to form a first interference pattern with a speed sensitivity V1; the second interference detection combination is used to split the P' polarized light into two sub-pulses and combine them after forming a time difference t2', and interfere to form a second interference pattern with a speed sensitivity V2.

[0008] Preferably, the first optical assembly includes a second beam splitter, a first time delay device, and a first beam combiner; the second beam splitter is used to split the S-polarized light into two sub-pulses S1 and S2; the first time delay device is used to make the two branches achieve a time difference of time t1; and the first beam combiner is used to combine the two branches to obtain a first combined beam; The second optical assembly includes a third beam splitter, a second time delay device, and a second beam combiner; the third beam splitter is used to split the P-polarized light into two sub-pulses P1 and P2, the second time delay device is used to make the two branches achieve a time difference of time t2, and the second beam combiner is used to combine the two branches to obtain a second combined beam; The first interference detection assembly includes a fifth beam splitter, a third time delay device, a fourth beam combiner, a first spatial shaping module, and a first image sensor; the fifth beam splitter is used to split the S' polarized light into two sub-pulses, S1' and S2'; the third time delay device is used to make the two branches achieve a time difference of time t1'; the fourth beam combiner is used to combine the two branches; the first spatial shaping module is used to spatially separate multiple wavelengths passing through the ultrafast event and project them to different time positions on the first image sensor; the first image sensor is used to obtain a first interference pattern with a velocity sensitivity of V1 formed by the interference of the chirped pulse with itself at a previous moment; The second interference detection combination includes a sixth beam splitter, a fourth time delay device, a fifth beam combiner, a second spatial shaping module and a second image sensor; the sixth beam splitter is used to split P' polarized light into two sub-pulses P1' and P2', the fourth time delay device is used to enable the two branches to achieve a time difference of time t2', the fifth beam combiner is used to combine the two branches, and the second spatial shaping module is used to spatially separate multiple wavelengths passing through the ultrafast event and project them to different time positions on the second image sensor; the second image sensor is used to obtain a second interference pattern with a velocity sensitivity of V2 formed by the interference of the chirped pulse with itself at the previous moment.

[0009] Preferably, the multiple time differences satisfy the following relationship: t1=t1', t2=t2', t1≠t2.

[0010] Preferably, the time domain shaping module adopts a glass rod, a volume Bragg grating or an optical fiber.

[0011] Preferably, the first time delay device and the third time delay device use a unified etalon as a time delay device; the second time delay device and the fourth time delay device use a unified etalon as a time delay device.

[0012] Preferably, the first spatial shaping module and the second spatial shaping module have the same structure, and both include a second beam splitter, a grating, a second lens, a spatial shaping element and a third lens; The second beam splitter is used to separate the input light and the reflected light; the input light transmitted through the second beam splitter is incident on the grating; the grating is used to perform spatial dispersion expansion on the pulse, and the expanded light beam is collimated by the second lens to the spatial shaping element; the spatial shaping element is composed of multiple reflective mirrors with different inclination angles, and the pulses are incident on different reflective mirrors in sequence according to their wavelength and return to the second lens at different angles; the reflected light is focused by the second lens and returns to the grating, and the grating spatially expands the multiple sub-pulses into a column, which is then incident on the third lens after passing through the second beam splitter and is finally output through the third lens.

[0013] Preferably, the second lens is an achromatic cemented lens.

[0014] On the other hand, the present invention provides a dual-sensitivity multi-frame ultrafast speed measurement imaging method, which is implemented using the above-mentioned dual-sensitivity multi-frame ultrafast speed measurement imaging system and can obtain two-dimensional velocity field information at multiple moments under dual sensitivity through a single shot; The dual-sensitivity multi-frame ultrafast speed measurement imaging method comprises: using a dual-sensitivity multi-frame ultrafast speed measurement imaging unit to obtain an interference pattern under dual sensitivity; using an information processing unit to obtain two-dimensional velocity field information under dual sensitivity based on the interference pattern under dual sensitivity.

[0015] Preferably, the method of obtaining an interference pattern under dual sensitivity by using a dual-sensitivity multi-frame ultrafast speed measurement imaging unit includes the following sub-steps: generating a femtosecond pulse by using a femtosecond laser; performing time domain stretching on the femtosecond pulse by using a time domain shaping module to obtain a broadened chirped pulse; dividing the chirped pulse into S-polarized light and P-polarized light by using a first optical splitter; dividing the S-polarized light into two sub-pulses by using a first optical combination and combining them after forming a time difference of t1 to obtain a first combined light; dividing the P-polarized light into two sub-pulses by using a second optical combination and combining them after forming a time difference of t2 to obtain a second combined light; combining the first combined light and the second combined light by using a third combiner to obtain a third combined light; and After passing through the first beam splitter, the beam is incident on the objective lens, and the beam is converged on the sample after passing through the objective lens; after passing through the ultrafast event, the sample reflects the beam back to the objective lens, and then passes through the first beam splitter and is incident on the first lens, and the signal light of the ultrafast event is collected and collimated by the first lens; the collimated signal light is divided into polarized light S' and polarized light P' by using the fourth beam splitter; the S' polarized light is divided into two sub-pulses by using the first interference detection combination, and the beams are combined after forming a time difference t1', and the interference forms a first interference pattern with a speed sensitivity of V1; the P' polarized light is divided into two sub-pulses by using the second interference detection combination, and the beams are combined after forming a time difference t2', and the interference forms a second interference pattern with a speed sensitivity of V2.

[0016] One or more technical solutions provided in the present invention have at least the following technical effects or advantages: The dual-sensitivity multi-frame ultrafast velocimetry imaging system provided by the present invention includes a dual-sensitivity multi-frame ultrafast velocimetry imaging unit and a signal processing unit. The dual-sensitivity multi-frame ultrafast velocimetry imaging unit combines an imaging device with time-domain shaping and spatial-domain shaping and a dual-sensitivity interferometry device. The dual-sensitivity multi-frame ultrafast velocimetry imaging unit is used to obtain an interference pattern under dual sensitivity. The signal processing unit is used to obtain two-dimensional velocity field information under dual sensitivity based on the interference pattern under dual sensitivity. In other words, the present invention combines an imaging system with time-domain shaping and spatial-domain shaping with dual-sensitivity interferometry technology, enabling the acquisition of multi-frame two-dimensional velocity field information under dual sensitivity in a single shot. This improves experimental efficiency and data reliability, as well as the accuracy of velocity measurement. It is also expected to become an effective solution for high-speed plasma shock wave diagnostic measurement. The present invention utilizes two interferometers with different delay times to cover a wider velocity range and dynamic measurement requirements. This invention has important scientific significance and application value for expanding the application scope of ultrafast imaging technology and improving the accuracy of velocity diagnosis. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic structural diagram of a dual-sensitivity multi-frame ultrafast speed measurement imaging unit in a dual-sensitivity multi-frame ultrafast speed measurement imaging system provided in Example 1 of the present invention; Figure 2 This is a structural schematic diagram of a spatial shaping module in a dual-sensitivity multi-frame ultrafast speed measurement imaging system provided in Example 1 of the present invention.

[0018] Among them, 101-femtosecond laser, 102-time domain shaping module, 103-first beam splitter, 104-second beam splitter, 105-first time delay device, 106-first beam combiner, 107-third beam splitter, 108-second time delay device, 109-second beam combiner, 110-third beam combiner, 111-first beam splitter, 112-objective lens, 113-first lens, 114-fourth beam splitter, 115-fifth beam splitter, 116-third time delay device, 117-fourth beam combiner, 118-first spatial domain shaping module, 119-first image sensor, 120-sixth beam splitter, 121-fourth time delay device, 122-fifth beam combiner, 123-second spatial domain shaping module, 124-second image sensor; 201 - second beam splitter, 202 - grating, 203 - second lens, 204 - spatial shaping element, 205 - third lens. DETAILED DESCRIPTION

[0019] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0020] Example 1: Example 1 provides a dual-sensitivity multi-frame ultrafast speed measurement imaging system, including: a dual-sensitivity multi-frame ultrafast speed measurement imaging unit and an information processing unit; the dual-sensitivity multi-frame ultrafast speed measurement imaging unit is combined with an imaging device with time domain shaping and spatial domain shaping and a dual-sensitivity interference measurement device, and the dual-sensitivity multi-frame ultrafast speed measurement imaging unit is used to obtain an interference pattern under dual sensitivity; the information processing unit is used to obtain two-dimensional velocity field information under dual sensitivity based on the interference pattern under dual sensitivity.

[0021] See also Figure 1 The dual-sensitivity multi-frame ultrafast speed measurement imaging unit includes a femtosecond laser 101, a time domain shaping module 102, a first beam splitter (specifically a polarization beam splitter) 103, a second beam splitter (specifically a common beam splitter) 104, a first time delay device 105, a first beam combiner (specifically a common beam splitter) 106, a third beam splitter (specifically a common beam splitter) 107, a second time delay device 108, a second beam combiner (specifically a common beam splitter) 109, a third beam combiner (specifically a polarization beam splitter) 110, a first beam splitter (specifically a common beam splitter) 111, and a second beam combiner (specifically a common beam splitter). Ordinary beam splitter) 111, objective lens 112, first lens 113, fourth beam splitter (specifically using a polarization beam splitter) 114, fifth beam splitter (specifically using an ordinary beam splitter) 115, third time delay device 116, fourth beam combiner (specifically using an ordinary beam splitter) 117, first spatial shaping module 118, first image sensor 119, sixth beam splitter (specifically using an ordinary beam splitter) 120, fourth time delay device 121, fifth beam combiner (specifically using an ordinary beam splitter) 122, second spatial shaping module 123 and second image sensor 124.

[0022] The ultrafast event is located in front of the objective lens 112 (i.e., on the outgoing light path). Specifically, the system adopts a reflective imaging system, and the ultrafast event is located near the working distance of the objective lens 112. That is, the light pulse passes through the objective lens 112 to converge the light beam onto the sample. After passing through the ultrafast event, the sample reflects the light beam back to the objective lens 112, and a light pulse carrying the ultrafast event light signal is obtained.

[0023] The femtosecond laser 101 is used to generate femtosecond pulses; the time domain shaping module 102 is used to perform time domain stretching on the femtosecond pulses to obtain broadened chirped pulses; the first optical splitter 103 is used to split the chirped pulses into two sub-pulses, S-polarized light and P-polarized light; wherein, the S-polarized light is split into two sub-pulses, S1 and S2, after passing through the second optical splitter 104. The two sub-pulses are passed through the first time delay device 105 so that the two branches achieve a time difference of time t1, and are then combined by the first beam combiner 106 to obtain a first combined light beam; the P-polarized light is split into two sub-pulses, P1 and P2, by the third optical splitter 107. The two sub-pulses are passed through the second time delay device 108 so that the two branches achieve a time difference of time t2, and are then combined by the second beam combiner 109 to obtain a second combined light beam; finally, the separately combined S-polarized light and P-polarized light are combined by the third beam combiner 110, that is, the third beam combiner is used to combine the first combined light beam and the second combined light beam to obtain a third combined light beam. The first beam splitter 111 is used to separate the incident and exiting light beams of the objective lens 112. Specifically, the third combined light beam passes through the first beam splitter 111 and is incident on the objective lens 112. After passing through the objective lens 112, the light beam converges on the sample. After the ultrafast event, the sample reflects the light beam back to the objective lens 112, and then passes through the first beam splitter 111 and is incident on the first lens 113. The signal light collected from the ultrafast event is collimated by the first lens 113. The collimated signal light passes through the fourth beam splitter 114, and the returned signal light is split into sub-pulse polarized light S' and polarized light P'. Among them, after passing through the fifth beam splitter 115, the S' polarized light is divided into two sub-pulses, S1' and S2'. The two sub-pulses pass through the third time delay device 116 so that the two branches achieve a time difference of time t1', and are combined by the fourth beam combiner 117. Subsequently, the multiple wavelengths passing through the ultrafast event are spatially separated by the first spatial domain shaping module 118 and projected onto different time positions on the first image sensor 119; the first image sensor obtains a first interference pattern with a velocity sensitivity of V1 formed by the interference of the chirped pulse with itself at the previous moment. At the same time, the P' polarized light is divided into two sub-pulses, P1' and P2', after passing through the sixth beam splitter 120. The two sub-pulses are passed through the fourth time delay device 121 so that the two branches achieve a time difference of time t2', and are combined by the fifth beam combiner 122. Subsequently, the multiple wavelengths passing through the ultrafast event are spatially separated by the second spatial domain shaping module 123 and projected onto different time positions on the second image sensor 124. The second image sensor 123 obtains a second interference pattern with a velocity sensitivity V' formed by the interference of the chirped pulse with itself at the previous moment.

[0024] The multiple time differences satisfy the following relationship: t1=t1', t2=t2', t1≠t2.

[0025] The time-domain shaping module 102 of the present invention is used to stretch a single pulse in the time domain, thereby generating a broadened chirped pulse. Pulse stretching utilizes the principle of optical dispersion to disperse light of different wavelengths at different moments in the time domain, thereby sequentially recording transient events at different wavelengths. The time-domain shaping module 102 can utilize dispersive elements such as glass rods, volume Bragg gratings, and optical fibers.

[0026] The first time delay device 105 and the third time delay device 116 use a unified etalon as a time delay device; the second time delay device 108 and the fourth time delay device 121 use a unified etalon as a time delay device.

[0027] The first image sensor 119 and the second image sensor 124 are used to detect image signals, and specifically can be cameras.

[0028] The first spatial shaping module 118 and the second spatial shaping module 123 have the same structure, and both include a second beam splitter 201 , a grating 202 , a second lens 203 , a spatial shaping element 204 and a third lens 205 .

[0029] For details, see Figure 2 The spatial shaping module includes a second beam splitter 201 , a grating 202 , a second lens 203 , a spatial shaping element 204 and a third lens 205 . The second beam splitter 201 is used to separate input light and reflected light. The input light transmitted through the second beam splitter 201 is incident on the grating 202. The grating 202 performs spatial dispersion expansion on the pulse. The expanded light beam passes through the second lens 203 (the second lens 203 is preferably an achromatic cemented lens) and is collimated to the spatial shaping element 204. The spatial shaping element 204 is composed of multiple reflective mirrors with different inclination angles (the spatial shaping element 204 is preferably a reflective mirror array). The pulses are sequentially incident on different reflective mirrors according to their wavelength and return to the second lens 203 at different angles. The reflected light is focused by the second lens 203 and returns to the grating 202. The grating 202 spatially expands the multiple sub-pulses into a column. The sub-pulses then pass through the second beam splitter 201 and are incident on the third lens 205. Finally, the light is output through the third lens 205.

[0030] The present invention is based on the interference pattern under dual sensitivity. Through the information processing unit (such as a computer), two-dimensional velocity field information under dual sensitivity can be obtained. In addition, the information processing unit can also be used to store and display the two-dimensional velocity field information under dual sensitivity.

[0031] The following further explains how to obtain the two-dimensional velocity field information under dual sensitivity based on the interference pattern under dual sensitivity.

[0032] The Doppler velocity information carried by the interference fringes can be extracted by the Fourier method. Since it is a two-dimensional imaging, the velocity information is also two-dimensional. Specifically, compared with the extraction of velocity information at a single moment, the present invention needs to perform Fourier transform on multiple frames one by one to extract the phase information of each position at each moment. Since each frame is the interference between the current moment and the previous moment, the phase change at each moment needs to be solved one by one and restored progressively. On this basis, the above operation is repeated for the interference imaging under two sensitivities. That is, the present invention obtains the velocity information under a certain sensitivity based on a certain interference pattern, and obtains the two-dimensional velocity field information under dual sensitivity after combination.

[0033] This invention utilizes a pump-probe method with high temporal resolution and the ability to capture ultrafast dynamic events. Based on the principle of time-stretch imaging, a time-domain shaping system stretches femtosecond laser pulses into time-sequenced chirped pulses, where different wavelengths correspond to chirp times. After detecting the ultrafast event, a specific spatial framing system is used in front of the detector to separate the chirped pulses from the time domain into the spatial domain by wavelength. Finally, images are captured in different areas of the camera, achieving a two-dimensional imaging effect arranged in time sequence. This invention can perform interferometric imaging of multiple beams at dual sensitivity. This application to ultrafast imaging enables dual-sensitivity ultrafast imaging velocity measurement at multiple moments.

[0034] For imaging interference, existing solutions usually use the interference of detection light and reference light, which can only obtain the depth information of the surface of the object to be measured but cannot obtain the speed information; for speed measurement, existing solutions can usually only record the two-dimensional velocity field information at a single moment, and multiple shots are required for multiple moments. The present invention combines single-shot multi-frame imaging with dual-sensitivity interference speed measurement. Compared with the interference of detection light and reference light, and multiple shots to obtain continuous speed information, the present invention uses the interference of detection light and itself at the previous moment to record the continuous changes in interference fringes on the surface of the object to be measured, and can obtain two-dimensional velocity field information at multiple frames of continuous moments in the case of a single shot. That is, for multi-frame interference imaging, the present invention uses the interference of detection light and itself at the previous moment, which can be used for speed measurement. For speed measurement imaging, the present invention realizes single-shot sequential multi-moment interference imaging. At the same time, the present invention also adds two sets of delay devices with different sensitivities, which can solve the problem of missing interference fringes caused by sudden changes in speed under a single sensitivity. The present invention uses dual-sensitivity velocimetry to address the issue of fringe loss. The signal light is split into two beams, which enter two velocity interferometers with different velocity sensitivities and are received by two detection instruments. As long as the two velocity sensitivities are not integer multiples, the number of lost fringes can be estimated. This method combines dual-sensitivity interferometric velocimetry with multi-frame imaging. This method, based on single-moment interferometric imaging velocimetry, achieves continuous multi-frame imaging, recording sequential interference fringe changes and ensuring multi-frame interference to extract continuous Doppler velocity information.

[0035] The present invention can achieve the acquisition of two-dimensional velocity field information at multiple moments in a single shot, thereby improving experimental efficiency and data credibility. Under the premise of single-shot multi-frame interferometric imaging velocimetry, the present invention achieves zero-time alignment and separation of signal lights of different sensitivities through polarization splitting, thereby realizing dual-sensitivity velocimetry. In summary, the present invention can achieve dual-sensitivity multi-frame interferometric imaging velocimetry in a single shot, further improving the accuracy of velocity measurement. The present invention can realize ultrafast two-dimensional frame interferometric imaging velocimetry under single-shot pump-probe conditions, can detect ultrafast changes in the two-dimensional velocity field, and can improve the framing frequency, spatial bandwidth, and time resolution of interferometric velocimetry.

[0036] Example 2: Example 2 provides a dual-sensitivity multi-frame ultrafast speed measurement and imaging method, which is implemented using the dual-sensitivity multi-frame ultrafast speed measurement and imaging system as described in Example 1, and can obtain two-dimensional velocity field information at multiple moments under dual sensitivity through a single shot; the dual-sensitivity multi-frame ultrafast speed measurement and imaging method includes: using a dual-sensitivity multi-frame ultrafast speed measurement and imaging unit to obtain an interference pattern under dual sensitivity; using an information processing unit to obtain two-dimensional velocity field information under dual sensitivity based on the interference pattern under dual sensitivity.

[0037] The method comprises the following sub-steps: generating a femtosecond pulse by using a femtosecond laser; performing time domain stretching on the femtosecond pulse by using a time domain shaping module to obtain a broadened chirped pulse; dividing the chirped pulse into S-polarized light and P-polarized light by using a first optical splitter; dividing the S-polarized light into two sub-pulses by using a first optical combination and combining them after forming a time difference of t1 to obtain a first combined light beam; dividing the P-polarized light into two sub-pulses by using a second optical combination and combining them after forming a time difference of t2 to obtain a second combined light beam; combining the first combined light beam and the second combined light beam by using a third combiner to obtain a third combined light beam; and combining the third combined light beam by using a second optical combination. The light beam is incident on the objective lens after passing through the first beam splitter, and converges on the sample after passing through the objective lens; the sample after passing through the ultrafast event reflects the light beam back to the objective lens, and then passes through the first beam splitter and is incident on the first lens, and the signal light of the ultrafast event is collected and collimated by the first lens; the collimated signal light is divided into polarized light S' and polarized light P' by using the fourth beam splitter; the S' polarized light is divided into two sub-pulses by using the first interference detection combination, and the beams are combined after forming a time difference of t1', and the interference forms a first interference pattern with a speed sensitivity of V1; the P' polarized light is divided into two sub-pulses by using the second interference detection combination, and the beams are combined after forming a time difference of t2', and the interference forms a second interference pattern with a speed sensitivity of V2.

[0038] Since the dual-sensitivity multi-frame ultrafast speed measurement imaging method provided in Example 2 is implemented using the dual-sensitivity multi-frame ultrafast speed measurement imaging system provided in Example 1, Example 2 can be understood by referring to the description of Example 1 and will not be repeated here.

[0039] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A dual-sensitivity multi-frame ultrafast speed measurement imaging system, characterized in that: include: Dual-sensitivity multi-frame ultrafast speed measurement imaging unit and information processing unit; The dual-sensitivity multi-frame ultrafast speed measurement imaging unit is combined with an imaging device with time domain shaping and spatial domain shaping and a dual-sensitivity interference measurement device. The dual-sensitivity multi-frame ultrafast speed measurement imaging unit is used to obtain an interference pattern under dual sensitivity; the information processing unit is used to obtain two-dimensional velocity field information under dual sensitivity based on the interference pattern under dual sensitivity.

2. The dual-sensitivity multi-frame ultrafast speed measurement imaging system according to claim 1, characterized in that: The dual-sensitivity multi-frame ultrafast speed measurement imaging unit includes a femtosecond laser, a time domain shaping module, a first beam splitter, a first optical combination, a second optical combination, a third beam combiner, a first beam splitter, an objective lens, a first lens, a fourth beam splitter, a first interference detection combination, and a second interference detection combination; The femtosecond laser is used to generate femtosecond pulses; The time domain shaping module is used to perform time domain stretching on the femtosecond pulse to obtain a broadened chirped pulse; The first optical splitter is used to split the chirped pulse into S-polarized light and P-polarized light; the first optical assembly is used to split the S-polarized light into two sub-pulses and combine them after forming a time difference t1 to obtain a first combined light beam; the second optical assembly is used to split the P-polarized light into two sub-pulses and combine them after forming a time difference t2 to obtain a second combined light beam; the third beam combiner is used to combine the first combined light beam and the second combined light beam to obtain a third combined light beam; The third combined light beam passes through the first beam splitter and is incident on the objective lens. The light beam is converged on the sample after passing through the objective lens. The sample, after passing through the ultrafast event, reflects the light beam back to the objective lens, and then passes through the first beam splitter and is incident on the first lens. The signal light of the ultrafast event is collected and collimated by the first lens. The fourth optical splitter is used to split the collimated signal light into polarized light S' and polarized light P'; the first interference detection combination is used to split the S' polarized light into two sub-pulses and combine them after forming a time difference t1', and interfere to form a first interference pattern with a speed sensitivity V1; the second interference detection combination is used to split the P' polarized light into two sub-pulses and combine them after forming a time difference t2', and interfere to form a second interference pattern with a speed sensitivity V2.

3. The dual-sensitivity multi-frame ultrafast speed measurement imaging system according to claim 2, characterized in that: The first optical assembly includes a second beam splitter, a first time delay device, and a first beam combiner; the second beam splitter is used to split the S-polarized light into two sub-pulses S1 and S2; the first time delay device is used to make the two branches achieve a time difference of time t1; the first beam combiner is used to combine the two branches to obtain a first combined beam; The second optical assembly includes a third beam splitter, a second time delay device and a second beam combiner; The third optical splitter is used to split the P-polarized light into two sub-pulses P1 and P2, the second time delay device is used to make the two branches achieve a time difference of time t2, and the second beam combiner is used to combine the two branches to obtain a second combined beam; The first interference detection assembly includes a fifth beam splitter, a third time delay device, a fourth beam combiner, a first spatial shaping module, and a first image sensor; the fifth beam splitter is used to split the S' polarized light into two sub-pulses, S1' and S2'; the third time delay device is used to make the two branches achieve a time difference of time t1'; the fourth beam combiner is used to combine the two branches; the first spatial shaping module is used to spatially separate multiple wavelengths passing through the ultrafast event and project them to different time positions on the first image sensor; the first image sensor is used to obtain a first interference pattern with a velocity sensitivity of V1 formed by the interference of the chirped pulse with itself at a previous moment; The second interference detection combination includes a sixth beam splitter, a fourth time delay device, a fifth beam combiner, a second spatial shaping module and a second image sensor; the sixth beam splitter is used to split P' polarized light into two sub-pulses P1' and P2', the fourth time delay device is used to enable the two branches to achieve a time difference of time t2', the fifth beam combiner is used to combine the two branches, and the second spatial shaping module is used to spatially separate multiple wavelengths passing through the ultrafast event and project them to different time positions on the second image sensor; the second image sensor is used to obtain a second interference pattern with a velocity sensitivity of V2 formed by the interference of the chirped pulse with itself at the previous moment.

4. The dual-sensitivity multi-frame ultrafast speed measurement imaging system according to claim 2, characterized in that: The multiple time differences satisfy the following relationship: t1=t1', t2=t2', t1≠t2.

5. The dual-sensitivity multi-frame ultrafast speed measurement imaging system according to claim 2, characterized in that: The time domain shaping module adopts glass rod, volume Bragg grating or optical fiber.

6. The dual-sensitivity multi-frame ultrafast speed measurement imaging system according to claim 3, characterized in that: The first time delay device and the third time delay device use a unified etalon as a time delay device; the second time delay device and the fourth time delay device use a unified etalon as a time delay device.

7. The dual-sensitivity multi-frame ultrafast speed measurement imaging system according to claim 3, characterized in that: The first spatial shaping module and the second spatial shaping module have the same structure, and both include a second beam splitter, a grating, a second lens, a spatial shaping element and a third lens; The second beam splitter is used to separate the input light and the reflected light; the input light transmitted through the second beam splitter is incident on the grating; the grating is used to perform spatial dispersion expansion on the pulse, and the expanded light beam is collimated by the second lens to the spatial shaping element; the spatial shaping element is composed of multiple reflective mirrors with different inclination angles, and the pulses are incident on different reflective mirrors in sequence according to their wavelength and return to the second lens at different angles; the reflected light is focused by the second lens and returns to the grating, and the grating spatially expands the multiple sub-pulses into a column, which is then incident on the third lens after passing through the second beam splitter and is finally output through the third lens.

8. The dual-sensitivity multi-frame ultrafast speed measurement imaging system according to claim 7, characterized in that: The second lens is an achromatic cemented lens.

9. A dual-sensitivity multi-frame ultrafast speed measurement imaging method, characterized in that: The dual-sensitivity multi-frame ultrafast velocity measurement imaging system according to any one of claims 1 to 8 is used to obtain two-dimensional velocity field information at multiple moments under dual sensitivity through a single shot; The dual-sensitivity multi-frame ultrafast speed measurement imaging method comprises: obtaining an interference pattern under dual sensitivity by using a dual-sensitivity multi-frame ultrafast speed measurement imaging unit; The information processing unit is used to obtain the two-dimensional velocity field information under the dual sensitivity according to the interference pattern under the dual sensitivity.

10. The dual-sensitivity multi-frame ultrafast speed imaging method according to claim 9, characterized in that: The method of obtaining an interference pattern under dual sensitivity by using a dual-sensitivity multi-frame ultrafast speed measurement imaging unit comprises the following sub-steps: generating femtosecond pulses by using a femtosecond laser; Using a time domain shaping module to perform time domain stretching on the femtosecond pulse to obtain a broadened chirped pulse; A first optical splitter is used to split a chirped pulse into S-polarized light and P-polarized light; a first optical combination is used to split the S-polarized light into two sub-pulses and combine them after forming a time difference of t1 to obtain a first combined light beam; a second optical combination is used to split the P-polarized light into two sub-pulses and combine them after forming a time difference of t2 to obtain a second combined light beam; a third beam combiner is used to combine the first combined light beam and the second combined light beam to obtain a third combined light beam; the third combined light beam is incident on an objective lens after passing through a first beam splitter, and the light beam is converged on a sample after passing through the objective lens; the sample after passing through an ultrafast event reflects the light beam back to the objective lens, and then passes through the first beam splitter and is incident on a first lens, and the signal light collected from the ultrafast event is collimated by the first lens; The collimated signal light is divided into polarized light S' and polarized light P' by using the fourth beam splitter; the S' polarized light is divided into two sub-pulses by using the first interference detection combination and the sub-pulses are combined after forming a time difference t1', thereby forming a first interference pattern with a speed sensitivity of V1 by interference; the P' polarized light is divided into two sub-pulses by using the second interference detection combination and the sub-pulses are combined after forming a time difference t2', thereby forming a second interference pattern with a speed sensitivity of V2.

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