High spatial-temporal resolution imaging system and imaging method based on wavelength multiplexing

Abstract

The invention provides a wavelength multiplexing-based high-temporal-spatial-resolution imaging system and an imaging method, which are used for solving the problems that the imaging resolution is reduced, the electronic noise is large and the imaging efficiency is high in the existing imaging technology based on a high-speed framing camera. Or the technical problems of inconsistent view fields among a plurality of pictures, easy mutual interference among imaging pictures and low system anti-interference capability and stability existing in a serialized laser shadow active imaging technology are solved. According to the high-temporal-spatial-resolution imaging system based on wavelength multiplexing, pulse lasers emitted by a plurality of high-energy nanosecond pulse lasers with different wavelengths are coupled through a plurality of dichroscopes, so that the plurality of pulse lasers are propagated on the same light path to form a composite pulse sequence and then irradiate a to-be-measured target, and the consistency of an imaging view field is ensured; and meanwhile, each detector can only receive one imaging light pulse with a corresponding wavelength through the light splitting module and the corresponding narrow-band optical filter, so that wavelength multiplexing of the imaging light pulse is realized.

Description

Technical Field

[0001] The present invention relates to an imaging system and an imaging method, and in particular to a high-temporal-spatial resolution imaging system and an imaging method based on wavelength multiplexing. Background Art

[0002] High-speed imaging technology uses a high-speed camera system to instantly record images of objects in high-speed motion and rapid deformation. After processing and analysis, the position, morphology, motion and other parameters of the object at different times are obtained. It is an important technical means to study ultrafast phenomena and has been widely used in the fields of high-speed collision, flow field diagnosis, and energetic material testing. With the continuous advancement of technology, the high-speed cameras used in traditional high-speed imaging have been upgraded to more than one million frame rates, which is of great significance for capturing dynamic processes in extremely short periods of time. However, the frame rate of a high-speed camera is inversely proportional to the number of pixels. The spatial resolution of existing high-speed cameras with a frame rate of one million can only reach tens of thousands of pixels, which poses a severe challenge to application scenarios that require simultaneous acquisition of high temporal and spatial resolution.

[0003] At present, the most representative high-temporal-spatial-resolution imaging technologies include imaging technology based on high-speed framing cameras and serialized laser shadow active imaging technology. Imaging technology based on high-speed framing cameras uses common aperture framing or wavefront framing to image the same object separately onto multiple image-intensified detectors. Each image-intensified detector is independently exposed through timing control to achieve high-speed imaging. Although imaging technology based on high-speed framing cameras has improved the temporal resolution to a certain extent, it relies on image-intensified detectors for weak light amplification and imaging, resulting in a decrease in imaging resolution and the introduction of a large amount of electronic noise. Serialized laser shadow active imaging technology abandons the image intensifier and instead uses multiple high-energy pulsed lasers to actively illuminate the target to be measured. Multiple detectors are controlled by timing to receive their corresponding detection pulses, thereby achieving high-temporal-spatial-resolution imaging. Although the serialized laser shadow active imaging technology avoids the problems of resolution degradation and electronic noise caused by the image intensifier, it brings three problems: First, each high-energy pulse laser and its corresponding detector are not coaxial and cannot share the optical system, which leads to inconsistent fields of view between multiple frames; Second, in the serialized laser shadow active imaging technology, multiple pulse lasers have the same wavelength, and the detectors at the detection end often receive pulse lasers at different times at the same time, which makes it easy for the imaging frames to interfere with each other; Third, the serialized laser shadow active imaging system is complex and large in size, which reduces the system's anti-interference ability and stability. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problems of reduced imaging resolution and large electronic noise in the existing imaging technology based on high-speed framing cameras, or inconsistent fields of view between multiple frames in the serialized laser shadow active imaging technology, easy mutual interference between imaging frames, and low system anti-interference ability and stability, and to provide a high spatiotemporal resolution imaging system and imaging method based on wavelength multiplexing.

[0005] In order to achieve the above purpose, the technical solution of the present invention is as follows: A high-temporal-spatial-resolution imaging system based on wavelength multiplexing, which is special in that it includes a wavelength multiplexing unit, a laser beam expansion device, an imaging unit and a timing control unit; The wavelength multiplexing unit comprises M high-energy nanosecond pulse lasers of different wavelengths and M-1 dichroic mirrors, M≥2; the transmission surface of the first dichroic mirror is located on the pulse laser output light path of the first high-energy nanosecond pulse laser, the reflection surface is located on the pulse laser output light path of the second high-energy nanosecond pulse laser, and the light pulses transmitted and reflected by the first dichroic mirror are coaxial; when M≥3, the transmission surface of the i-th dichroic mirror is located on the light path of the light pulse after being transmitted by the i-1-th dichroic mirror, the reflection surface is located on the pulse laser output light path of the i+1-th high-energy nanosecond pulse laser, and the light pulses transmitted and reflected by the i-th dichroic mirror are coaxial, i=2,...,M-1; M pulsed lasers of different wavelengths pass through M-1 dichroic mirrors to generate a composite pulse sequence; The laser beam expansion device is located on the optical path of the composite pulse sequence, and the target to be measured is located on the transmission optical path of the composite pulse sequence after passing through the laser beam expansion device, so as to form a target optical pulse sequence carrying target information; The imaging unit includes a detection end imaging optical system, a light splitting module and M detectors; The imaging optical system at the detection end is located on the transmission optical path of the target optical pulse sequence, and is used to form an imaging optical pulse sequence; the light splitting module is located on the transmission optical path of the imaging optical pulse sequence, and is used to split the imaging optical pulse sequence into M paths; and the M detectors are respectively located on the transmission optical paths of the M paths of the imaging optical pulse sequence; A narrowband filter is disposed at the front end of each detector; the light transmission ranges of the M narrowband filters are different, and the wavelengths corresponding to the light transmission ranges are matched one by one with the pulse laser wavelengths of the M high-energy nanosecond pulse lasers, so that each detector only receives imaging light pulses of the corresponding wavelength; The timing control unit is electrically connected to the M high-energy nanosecond pulse lasers and the M detectors respectively, and is used to synchronously control the laser emission time of each high-energy nanosecond pulse laser and the shutter time of the corresponding detector according to preset timing parameters.

[0006] Further, the light splitting module includes M-1 beam splitters; The first beam splitter is located on the transmission optical path of the imaging light pulse sequence, and is used to split the imaging light pulse sequence into the first reflected light and the first transmitted light; when M≥3, the jth beam splitter is located on the optical path of the j-1th transmitted light, and is used to split the corresponding transmitted light into the jth reflected light and the jth transmitted light, j=2,...,M-1; the first M-1 detectors are respectively located on the transmission optical paths of the first to M-1th reflected light, and the Mth detector is located on the transmission optical path of the M-1th transmitted light.

[0007] Furthermore, the sum of the angle between the j-th beam splitter surface and the laser optical axis incident thereon and the angle between the j-1-th beam splitter surface and the laser optical axis incident thereon is 180°, j=2,...,M-1.

[0008] Further, the light splitting module is a pyramid; The pyramid is provided with M reflectors, which are located on the transmission light path of the imaging light pulse sequence and are used to divide the imaging light pulse sequence into M paths through the M reflectors thereon.

[0009] Furthermore, the sum of the angles between the transmission surface of the i-th dichroic mirror and the laser light axis incident on its transmission surface and the angles between the transmission surface of the i-1-th dichroic mirror and the laser light axis incident on its transmission surface is 180°, i=2,...,M-1. This arrangement facilitates integration, thereby achieving miniaturization of the imaging system.

[0010] Furthermore, a knife edge is provided in the imaging optical system of the detection end for realizing high temporal and spatial resolution laser schlieren imaging.

[0011] Furthermore, the optical depth of the narrowband filter is greater than 5, and the light transmission bandwidth is less than or equal to 3 nm.

[0012] Furthermore, the timing control unit is implemented by using a digital pulse signal generator DG645; and the detector is implemented by using a CCD or CMOS camera.

[0013] Furthermore, M=4.

[0014] In addition, the present invention also provides a high spatiotemporal resolution imaging method based on wavelength multiplexing, which is special in that it includes the following steps: Step 1, building the above-mentioned high spatiotemporal resolution imaging system based on wavelength multiplexing; Step 2, turn on M high-energy nanosecond pulse lasers, adjust the positions and parameters of M-1 dichroic mirrors, laser beam expansion devices, detection end imaging optical systems, and M-1 beam splitters, so that the light pulses transmitted by the M-1 dichroic mirrors, the laser beam expansion devices, the detection end imaging optical systems, and the light pulses transmitted by the M-1 beam splitters are coaxial; Step 3, the timing control unit synchronously controls the laser emission time of each high-energy nanosecond pulse laser and the shutter time of the corresponding detector according to the preset timing parameters, so that the pulse lasers of different wavelengths pass through M-1 dichroic mirrors to generate a composite pulse sequence. After the composite pulse sequence is irradiated on the target to be measured, the target light pulse sequence carrying the target information passes through the imaging optical system of the detection end, and is coaxially incident on the spectroscopic module in sequence. After the spectroscopic module, it passes through M narrow-band filters respectively so that the corresponding detectors at the back end receive the imaging light pulses of the corresponding wavelengths, and the imaging of the target to be measured at M different times is obtained.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention provides a high spatiotemporal resolution imaging system based on wavelength multiplexing. The pulse lasers emitted by multiple high-energy nanosecond pulse lasers with different wavelengths are coupled through multiple dichroic mirrors, so that the multiple pulse lasers propagate on the same optical path, and are irradiated onto the target to be measured after forming a composite pulse sequence, thereby ensuring the consistency of the imaging field of view. At the same time, multiple detectors are arranged at the detection end, and a narrow-band filter matching each high-energy nanosecond pulse laser is arranged in front of each detector. Through the spectroscopic module and the corresponding narrow-band filter, each detector can only receive an imaging light pulse of a corresponding wavelength, thereby realizing wavelength multiplexing of the imaging light pulse. The present invention abandons the image-enhanced detector, and the imaging resolution can reach tens of millions of pixels, and the imaging field of view is consistent. By accurately controlling the emission time of pulse lasers with different wavelengths and the shutter time of the corresponding detector, high temporal resolution and high spatial resolution imaging are ensured.

[0016] 2. The present invention provides a high spatiotemporal resolution imaging system based on wavelength multiplexing, which has a simple structure, strong anti-interference ability and wide applicability.

[0017] 3. The angle between the transmission surface of each dichroic mirror and the laser optical axis incident on its transmission surface and the angle between the beam splitting surface of the beam splitter and the laser optical axis incident on its beam splitting surface in the present invention can make multiple high-energy nanosecond pulse lasers and multiple detectors reasonably arranged, easy to integrate, and realize the miniaturization of the imaging system.

[0018] 3. The high spatiotemporal resolution imaging method based on wavelength multiplexing provided by the present invention is simple to operate and highly practical. It can be widely used in the fields of high-speed collision, flow field diagnosis, energetic material testing, etc. for high spatiotemporal resolution imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of a first embodiment of a high spatiotemporal resolution imaging system based on wavelength multiplexing of the present invention.

[0020] The reference numerals are as follows: 1- High energy nanosecond pulse laser, 2- High energy nanosecond pulse laser, 3- High energy nanosecond pulse laser, 4- High-energy nanosecond pulse laser, 5-first dichroic mirror, 6-second dichroic mirror, 7-third dichroic mirror, 8-laser beam expansion device, 9-target to be measured, 10-detection end imaging optical system, 11-first beam splitter, 12-second beam splitter, 13-third beam splitter, 14- Narrow Band Filter, 15- Narrow Band Filter, 16- Narrow Band Filter, 17- Narrow band filter, 18-first detector, 19-second detector, 20-third detector, 21-fourth detector. DETAILED DESCRIPTION

[0021] In order to make the advantages and features of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Embodiment 1 like Figure 1 As shown, a high spatiotemporal resolution imaging system based on wavelength multiplexing includes a wavelength multiplexing unit, a laser beam expansion device 8, an imaging unit, and a timing control unit. The wavelength multiplexing unit includes four high-energy nanosecond pulse lasers of different wavelengths and three dichroic mirrors. The four high-energy nanosecond pulse lasers of different wavelengths are used as illumination light sources, and are coaxially output after passing through three dichroic mirrors to form a composite pulse sequence.

[0023] The four high-energy nanosecond pulse lasers are denoted as High energy nanosecond pulse laser1, High energy nanosecond pulse laser2, High-energy nanosecond pulsed lasers3 and A high-energy nanosecond pulse laser 4 is provided, and the three dichroic mirrors are respectively recorded as a first dichroic mirror 5, a second dichroic mirror 6 and a third dichroic mirror 7. The transmission surface of the first dichroic mirror 5 is located at On the pulse laser emission optical path of the high energy nanosecond pulse laser 1, the reflection surface is located at The pulse laser output optical path of the high energy nanosecond pulse laser 2, and The light pulses of the pulse laser of the high energy nanosecond pulse laser 1 after being transmitted through the first dichroic mirror 5 are The pulsed laser of the high-energy nanosecond pulsed laser 2 is coaxially emitted after being reflected by the first dichroic mirror 5. The transmission surface of the second dichroic mirror 6 is located on the optical path of the light pulse after being transmitted or reflected by the first dichroic mirror 5, and the reflection surface is located The light pulses on the pulse laser emission light path of the high energy nanosecond pulse laser 3 and after being transmitted by the second dichroic mirror 6 are The pulsed laser of the high-energy nanosecond pulsed laser 3 is coaxially emitted after being reflected by the second dichroic mirror 6. The transmission surface of the third dichroic mirror 7 is located on the optical path of the light pulse after being transmitted or reflected by the second dichroic mirror 6, and the reflection surface is located The light pulses on the pulse laser emission light path of the high energy nanosecond pulse laser 4 and after being transmitted by the third dichroic mirror 7 are The pulse laser of the high-energy nanosecond pulse laser 4 is reflected by the third dichroic mirror 7 and then emitted coaxially. The wavelength is The pulsed laser is sequentially transmitted through the first dichroic mirror 5, the second dichroic mirror 6, and the third dichroic mirror 7 and then irradiated onto the target 9 to be measured. The wavelength is The pulsed laser is reflected by the first dichroic mirror 5, and then transmitted through the second dichroic mirror 6 and the third dichroic mirror 7, and then irradiated onto the target 9 to be measured. The wavelength is The pulsed laser is reflected by the second dichroic mirror 6, transmitted by the third dichroic mirror 7, and then irradiated onto the target 9 to be measured. The wavelength is The pulsed laser is reflected by the third dichroic mirror 7 and then irradiated onto the target 9 to be measured. The wavelength is The pulsed laser with a wavelength of The pulsed laser with a wavelength of The pulsed laser with a wavelength of The pulsed laser is controlled by the timing control unit and then coaxially output through three dichroic mirrors to form a composite pulse sequence.

[0024] The laser beam expander 8 is located on the transmission optical path of the composite pulse sequence, and the target 9 to be measured is located on the transmission optical path of the composite pulse sequence after being transmitted by the laser beam expander 8, and is used to form a target optical pulse sequence carrying target information after passing through the target 9 to be measured.

[0025] The imaging unit includes a detection end imaging optical system 10, a spectroscopic module, and four detectors, wherein the number of detectors is the same as the number of high-energy nanosecond pulse lasers, and the detectors can be selected from high-performance CCD or CMOS cameras. The detection end imaging optical system 10 is located on the transmission optical path of the target light pulse sequence and is used to form an imaging light pulse sequence. By adding a knife edge to the detection end imaging optical system 10, high temporal and spatial resolution laser schlieren imaging can be achieved.

[0026] In this embodiment, the light splitting module adopts a wavefront framing mode, that is, the light splitting module is set to three beam splitters. The three beam splitters are sequentially recorded as the first beam splitter 11, the second beam splitter 12, and the third beam splitter 13, and the four detectors are respectively recorded as the first detector 18, the second detector 19, the third detector 20, and the fourth detector 21. The first beam splitter 11 is located on the transmission optical path of the imaging light pulse sequence, and is used to divide the imaging light pulse sequence into a first beam of transmitted light and a first beam of reflected light. The second beam splitter 12 is located on the transmission optical path of the first beam of transmitted light, and is used to divide the corresponding transmitted light into a second beam of transmitted light and a second beam of reflected light. The third beam splitter 13 is located on the transmission optical path of the second beam of transmitted light, and is used to divide the corresponding transmitted light into a third beam of transmitted light and a third beam of reflected light. The first detector 18 is located on the transmission optical path of the first beam of reflected light, the second detector 19 is located on the transmission optical path of the second beam of reflected light, the third detector 20 is located on the transmission optical path of the third beam of reflected light, and the fourth detector 21 is located on the transmission optical path of the third beam of transmitted light.

[0027] The front end of the first detector 18, the second detector 19, the third detector 20 and the fourth detector 21 are respectively provided with a high-performance narrow-band filter, which only allows light pulses of one wavelength to pass through, and the light pulses of the other three wavelengths are filtered out; the high-performance narrow-band filter refers to a narrow-band filter with an optical depth of >5 and a passband of ≤3nm. The passband ranges of the four narrow-band filters are different, and the wavelengths corresponding to their passband ranges are matched one by one with the pulse laser wavelengths of the four high-energy nanosecond pulse lasers, so that each detector only receives imaging light pulses of the corresponding wavelength. In this embodiment, the wavelength corresponding to the passband range of the narrow-band filter at the front end of the first detector 18 is , denoted as The wavelength corresponding to the light transmission range of the narrow-band filter 14 and the second detector 19 is , denoted as The wavelength corresponding to the light transmission range of the narrow-band filter 15 and the narrow-band filter at the front end of the third detector 20 is , denoted as The wavelength corresponding to the light transmission range of the narrow-band filter 16 and the narrow-band filter at the front end of the fourth detector 21 is , denoted as Narrowband filter 17. The position of each narrowband filter in the present invention does not need to correspond one-to-one with the position of each high-energy nanosecond pulse laser.

[0028] The timing control unit is electrically connected to the four high-energy nanosecond pulse lasers and the four detectors, respectively, and is used to synchronously control the laser emission time of each high-energy nanosecond pulse laser and the shutter time of the corresponding detector according to the preset timing parameters. In conjunction with the corresponding narrow-band filter, it can effectively ensure that each detector accurately detects the imaging light pulse of the corresponding wavelength, and realizes the target imaging at different times. The timing control unit adopts a precision timing control unit, and its control accuracy can reach the nanosecond or even picosecond level. In this embodiment, it is preferably implemented by a digital pulse signal generator DG645. The present invention abandons the CCD or CMOS camera based on the image intensifier, and can achieve tens of millions of pixels, realizing high time resolution and high spatial resolution imaging.

[0029] remove In addition to the high-energy nanosecond pulse laser 1, the other three high-energy nanosecond pulse lasers can be arranged on the same side or on two sides. At the same time, the three dichroic mirrors are arranged along the same horizontal plane, and the angle between the transmission surface of the three dichroic mirrors and the laser optical axis incident on the transmission surface can be any angle of 0 to 180°. In order to achieve system integration and miniaturization, it is preferred in this embodiment The high energy nanosecond pulse laser 1 is arranged in the horizontal direction. High-energy nanosecond pulse lasers 2 and The high-energy nanosecond pulse laser 4 is arranged on the same side and perpendicular to The setting direction of the high energy nanosecond pulse laser 1, The high energy nanosecond pulse laser 3 is also perpendicular to The setting direction of the high energy nanosecond pulse laser 1, but it is related to High energy nanosecond pulse laser 2 and The high-energy nanosecond pulse laser 4 is located on different sides. Accordingly, the sum of the angles between the transmission surfaces of two adjacent dichroic mirrors and the laser optical axis incident on the corresponding transmission surfaces is 180°, that is, the sum of the angles between the transmission surface of the second dichroic mirror 6 and the laser optical axis incident on its transmission surface and the angle between the transmission surface of the first dichroic mirror 5 and the laser optical axis incident on its transmission surface is 180°, and the sum of the angles between the transmission surface of the third dichroic mirror 7 and the laser optical axis incident on its transmission surface and the angle between the transmission surface of the second dichroic mirror 6 and the laser optical axis incident on its transmission surface is 180°.

[0030] Correspondingly, the setting principle of the detector is similar to that of the high-energy nanosecond pulse laser, and the setting principle of the beam splitter is similar to that of the dichroic mirror, which will not be described in detail here.

[0031] At the same time, the present invention also provides a high temporal and spatial resolution imaging method based on wavelength multiplexing, which specifically includes the following steps: Step 1: Build the above-mentioned high spatiotemporal resolution imaging system based on wavelength multiplexing.

[0032] Step 2, turn on four high-energy nanosecond pulse lasers, adjust the positions and parameters of three dichroic mirrors, laser beam expansion device 8, detection end imaging optical system 10 and three beam splitters, so that the light pulses transmitted by the three dichroic mirrors, laser beam expansion device 8, detection end imaging optical system 10 and the light pulses transmitted by the three beam splitters are coaxial, and the system debugging is completed. During debugging, four high-energy nanosecond pulse lasers can be turned on at the same time, or two adjacent high-energy nanosecond pulse lasers can be turned on at the same time and debugged in sequence.

[0033] Step 3, the timing control unit synchronously controls the laser emission time of each high-energy nanosecond pulse laser and the shutter time of the corresponding detector according to the preset timing parameters, so that the pulse lasers of different wavelengths pass through three dichroic mirrors to generate a composite pulse sequence. After the composite pulse sequence is irradiated on the target 9 to be measured, the target light pulse sequence carrying the target information passes through the imaging optical system 10 at the detection end, and is coaxially incident on the three beam splitters in sequence. After being reflected by the first beam splitter 11, the second beam splitter 12, and the third beam splitter 13 and transmitted by the third beam splitter 13, the corresponding first detector 18, the second detector 19, the third detector 20, and the fourth detector 21 at the rear end respectively receive the imaging light pulses of the corresponding wavelengths through four narrow-band filters, so as to obtain the imaging of the target to be measured at four different times.

[0034] Embodiment 2 The difference between this embodiment and the first embodiment is that the light splitting module adopts the common aperture light splitting mode, that is, the light splitting module is implemented by a tetrahedron. The specific principle is: four reflective mirrors are arranged on the tetrahedron, and the tetrahedron is located on the transmission optical path of the imaging light pulse sequence, and is used to divide the imaging light pulse sequence into four paths through the four reflective mirrors thereon. The four-path imaging light pulse sequence passes through the corresponding narrow-band filters so that the first detector 18, the second detector 19, the third detector 20, and the fourth detector 21 receive the imaging light pulses of the corresponding wavelengths.

[0035] The present invention provides a high spatiotemporal resolution imaging system based on wavelength multiplexing, which uses multiple pulsed lasers of different wavelengths and couples them through corresponding dichroic mirrors to ensure that multiple pulsed lasers propagate on the same optical path and irradiate the target to be measured through the same laser beam expansion device 8. After passing through the target to be measured, the pulsed laser carrying the target information is imaged on different optical paths through a tetrahedron; at the same time, a corresponding narrow-band filter is set at the front end of the detector of each optical path to ensure that each detector can only receive a light pulse of one wavelength. The present invention not only realizes high temporal resolution and high spatial resolution imaging, but also ensures the consistency of the imaging field of view. The overall system structure is simple, the anti-interference ability is improved, and the applicability is enhanced. It has broad application prospects and important practical value in the fields of high-speed collision, flow field diagnosis, energetic material testing, etc. In the present invention, by increasing the number of high-energy nanosecond pulsed lasers and corresponding detectors, eight or even sixteen high spatiotemporal resolution imaging can be achieved.

[0036] The above description is only used to illustrate the technical solution of the present invention rather than to limit it. For ordinary professional and technical personnel in the field, the specific technical solution recorded in the above embodiment can be modified, or some of the technical features therein can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution protected by the present invention.

Claims

1. A high spatiotemporal resolution imaging system based on wavelength multiplexing, characterized in that: It comprises a wavelength multiplexing unit, a laser beam expansion device (8), an imaging unit and a timing control unit; The wavelength multiplexing unit comprises M high-energy nanosecond pulse lasers of different wavelengths and M-1 dichroic mirrors, M≥2; the transmission surface of the first dichroic mirror is located on the pulse laser output light path of the first high-energy nanosecond pulse laser, the reflection surface is located on the pulse laser output light path of the second high-energy nanosecond pulse laser, and the light pulses transmitted and reflected by the first dichroic mirror are coaxial; when M≥3, the transmission surface of the i-th dichroic mirror is located on the light path of the light pulse after being transmitted by the i-1-th dichroic mirror, the reflection surface is located on the pulse laser output light path of the i+1-th high-energy nanosecond pulse laser, and the light pulses transmitted and reflected by the i-th dichroic mirror are coaxial, i=2,...,M-1; M pulsed lasers of different wavelengths pass through M-1 dichroic mirrors to generate a composite pulse sequence; The laser beam expansion device (8) is located on the optical path of the composite pulse sequence, and the target to be measured (9) is located on the transmission optical path of the composite pulse sequence after passing through the laser beam expansion device (8), so as to form a target optical pulse sequence carrying target information; The imaging unit comprises a detection end imaging optical system (10), a light splitting module and M detectors; The detection end imaging optical system (10) is located on the transmission optical path of the target optical pulse sequence and is used to form an imaging optical pulse sequence; the light splitting module is located on the transmission optical path of the imaging optical pulse sequence and is used to split the imaging optical pulse sequence into M paths; the M detectors are respectively located on the transmission optical paths of the M paths of the imaging optical pulse sequence; A narrowband filter is disposed at the front end of each detector; the light transmission ranges of the M narrowband filters are different, and the wavelengths corresponding to the light transmission ranges are matched one by one with the pulse laser wavelengths of the M high-energy nanosecond pulse lasers, so that each detector only receives imaging light pulses of the corresponding wavelength; The timing control unit is electrically connected to the M high-energy nanosecond pulse lasers and the M detectors respectively, and is used to synchronously control the laser emission time of each high-energy nanosecond pulse laser and the shutter time of the corresponding detector according to preset timing parameters.

2. The high spatiotemporal resolution imaging system based on wavelength multiplexing according to claim 1, characterized in that: The light splitting module includes M-1 beam splitters; The first beam splitter is located on the transmission optical path of the imaging light pulse sequence, and is used to split the imaging light pulse sequence into the first reflected light and the first transmitted light; when M≥3, the jth beam splitter is located on the optical path of the j-1th transmitted light, and is used to split the corresponding transmitted light into the jth reflected light and the jth transmitted light, j=2,...,M-1; the first M-1 detectors are respectively located on the transmission optical paths of the first to M-1th reflected light, and the Mth detector is located on the transmission optical path of the M-1th transmitted light.

3. The high spatiotemporal resolution imaging system based on wavelength multiplexing according to claim 2, characterized in that: The sum of the angle between the j-th beam splitter surface and the laser optical axis incident thereon and the angle between the j-1-th beam splitter surface and the laser optical axis incident thereon is 180°, j=2,...,M-1.

4. The high spatiotemporal resolution imaging system based on wavelength multiplexing according to claim 1, characterized in that: The light splitting module is a pyramid; The pyramid is provided with M reflectors, which are located on the transmission light path of the imaging light pulse sequence and are used to divide the imaging light pulse sequence into M paths through the M reflectors thereon.

5. A high spatiotemporal resolution imaging system based on wavelength multiplexing according to any one of claims 1 to 4, characterized in that: The sum of the angles between the i-th dichroic mirror transmission surface and the laser optical axis incident thereon and the angles between the i-1-th dichroic mirror transmission surface and the laser optical axis incident thereon is 180°, i=2,...,M-1.

6. The high spatiotemporal resolution imaging system based on wavelength multiplexing according to claim 5, characterized in that: The detection end imaging optical system (10) is provided with a knife edge for realizing high temporal and spatial resolution laser schlieren imaging.

7. The high spatiotemporal resolution imaging system based on wavelength multiplexing according to claim 1, characterized in that: The optical depth of the narrowband filter is greater than 5, and the light transmission bandwidth is less than or equal to 3nm.

8. The high spatiotemporal resolution imaging system based on wavelength multiplexing according to claim 2, characterized in that: The timing control unit is implemented by a digital pulse signal generator DG645; The detector adopts a CCD or CMOS camera.

9. The high spatiotemporal resolution imaging system based on wavelength multiplexing according to claim 1, characterized in that: The M=4.

10. A high spatiotemporal resolution imaging method based on wavelength multiplexing, characterized in that: The following steps are involved: Step 1, constructing a high spatiotemporal resolution imaging system based on wavelength multiplexing as described in any one of claims 1 to 9; Step 2, turning on M high-energy nanosecond pulse lasers, adjusting the positions and parameters of M-1 dichroic mirrors, the laser beam expansion device (8), the detection end imaging optical system (10), and the M-1 beam splitters, so that the light pulses transmitted through the M-1 dichroic mirrors, the laser beam expansion device (8), the detection end imaging optical system (10), and the light pulses transmitted through the M-1 beam splitters are coaxial; Step 3, the timing control unit synchronously controls the laser emission time of each high-energy nanosecond pulse laser and the shutter time of the corresponding detector according to the preset timing parameters, so that the pulse lasers of different wavelengths pass through M-1 dichroic mirrors to generate a composite pulse sequence. After the composite pulse sequence is irradiated onto the target to be measured (9), the target light pulse sequence carrying the target information passes through the imaging optical system (10) at the detection end, and then coaxially incident on the spectroscopic module in sequence. After being split by the spectroscopic module, the corresponding detectors at the back end respectively pass through M narrow-band filters to receive the imaging light pulses of the corresponding wavelengths, thereby obtaining the imaging of the target to be measured at M different times.

Images