A streak camera based ultrafast compression holographic imaging system and method
By using an ultrafast compressed holographic imaging system based on a streak camera, and employing pinhole array plates and cylindrical lens encoding reference light technology, combined with compressed sensing technology, the existing technical problems in ultrafast imaging technology have been solved. This system enables the recording of multiple holographic images of ultrafast phenomena in a single measurement, solving the problem of recording only one image at a time in traditional holographic imaging, and achieving high frame rate holographic imaging.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-17
- Publication Date
- 2026-04-07
AI Technical Summary
Existing ultrafast imaging technologies struggle to simultaneously record the intensity and phase information of ultrafast phenomena in a single measurement, and traditional holographic recording optical paths can only record one holographic image at a time, making it difficult to meet the recording requirements of multiple holograms.
An ultrafast compressed holographic imaging system based on a streak camera is adopted. By designing a special reference light optical path unit, a pinhole array plate, a convex lens and a cylindrical lens are used for encoding. Combined with a streak camera and a compressed sensing algorithm, the phase interference of the object light and the reference light and the recording of the compressed hologram are realized.
It enables the simultaneous recording of intensity and phase information of ultrafast phenomena in a single measurement, with an imaging speed of tens of trillions of frames per second and the ability to record hundreds of holographic images in a single measurement, thus meeting the real-time observation requirements of ultrafast processes.
Smart Images
Figure CN115561983B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of holographic imaging, and particularly relates to an ultrafast compressed holographic imaging system and method based on a fringe camera. BACKGROUND
[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute the prior art.
[0003] In recent years, the study of transient events and ultrafast phenomena (events occurring in picoseconds, femtoseconds) has become a hot topic. For ultrafast laser-induced plasma, laser filamentation and ablation, it is of great academic and application value to study how to visualize the information evolution of transient events in two-dimensional space. With the development of ultrafast laser technology and high temporal-spatial resolution detectors, it is possible to capture transient events. So far, a variety of methods have been developed. Initially, pump-probe technology was applied in this field, which repeatedly detected the ultrafast scene to capture its specific occurrence process. However, many ultrafast phenomena are difficult or impossible to repeat, such as optical freak waves, atomic motion in chemical reaction processes, light scattering in living tissues, etc. At this time, the pump-probe technology will be difficult to apply. To overcome the limitations of the pump-probe method, single-shot ultrafast imaging technology has been developed, which can capture the entire dynamic process in real time by taking a picture. The imaging speed can reach 100 Mfps. Single-shot ultrafast imaging technology can be divided into direct imaging and reconstruction imaging. Direct imaging obtains images of transient events occurring through various imaging light paths. For example, Hou et al. proposed using polarization technology to observe the propagation of a single femtosecond laser pulse in a transparent medium at a high frame rate. Oishi et al. proposed a sequential time-aperture mapping photography (STAMP) technology, which uses a pulsed laser as an illumination source, generates a chirped pulse sequence to illuminate each frame of image in the framing imaging, and then realizes spatial separation imaging through a spatial mapping device. However, the imaging light path is relatively complex, and the authors have only achieved the recording of 6 images in experiments. Subsequently, Kannari et al. proposed an improved method of STAMP, i.e. SF-STAMP based on spectral filtering. This method increases the number of recorded images in a single imaging process to 25, but the problem is that the multiple images recorded are not in the same spectrum, which will affect the recovery of image information. In 2014, Wang et al. proposed an ultrafast imaging technology based on information compression theory (CUP), which combines the ultra-short time resolution of the compressive sensing algorithm and the streak camera. The imaging speed can reach 100 trillion frames per second, and the number of images recorded in a single recording can reach 350. Therefore, the CUP method is the most widely used. However, in the above ultrafast imaging methods, only the intensity information of the object wave can be recorded, and the application scenarios are limited. In the detection of ultrafast scenes, phase information and intensity information are equally important, and in the detection of phase-type or quasi-phase-type objects such as living cells, phase information is even more important than intensity information. Wang Xiaolei et al. used pulsed laser and angular multiplexed holography technology to realize single-shot holographic ultrafast imaging (PDH), which recorded three holographic images of the laser breakdown process in air using a holographic image. Due to the use of off-axis holography technology, the "walk-off" effect exists, making it difficult to record a large field of view. Reconstruction imaging needs to calculate and process the multiple images captured in the imaging light path to improve the imaging resolution.Recording multiple holographic images of an ultrafast process in a single measurement using a holographic optical path remains a significant challenge. Summary of the Invention
[0004] To address the shortcomings of existing technologies, the present invention aims to provide an ultrafast compressed holographic imaging system and method based on a streak camera, which can capture the light field distribution in ultrafast dynamic scenes. This method can simultaneously record the intensity and phase information of ultrafast phenomena in a single measurement, providing a new means for recording ultrafast phenomena.
[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:
[0006] The first aspect of the present invention provides an ultrafast compressed holographic imaging system based on a streak camera, comprising: a laser emitting unit, an object light optical path unit, a reference light optical path unit, and a hologram compression unit; the laser emitting unit splits the emitted laser into two paths, one path as the object light entering the object light optical path unit, and the other path as the reference light entering the reference light optical path unit; the reference light optical path unit "encodes" the reference light and interferes with the object light at different times output by the object light optical path unit to form a sequence of holograms; after being compressed by the hologram compression unit, a compressed hologram is obtained.
[0007] Furthermore, the laser emitting unit includes a laser, a pinhole, and a beam splitter. The laser emitted by the laser is filtered and collimated by the pinhole to become parallel light, and then split into two paths after passing through the first beam splitter.
[0008] Furthermore, the object-optical path unit includes a second reflecting mirror, a dynamic object, a microscope objective, and a microscope tube lens arranged sequentially.
[0009] Furthermore, the object light carries the object's information after passing through it, and enters the hologram compression unit after being magnified by the microscope objective and the microscope tube lens.
[0010] Furthermore, the reference light path unit includes a pinhole array plate, a convex lens, a first reflecting mirror, and a cylindrical lens arranged sequentially.
[0011] Furthermore, after the reference light passes through a specially designed pinhole array plate, it becomes a series of spherical waves with different propagation directions. These spherical waves pass through a convex lens and become a series of plane waves propagating in different directions. Then, after passing through a cylindrical lens along the x-direction, they become a collection of elongated plane waves with different incident directions, which are connected but do not overlap, near the focal plane of the cylindrical lens.
[0012] Furthermore, the hologram compression unit includes a second beam splitter and a streak camera; the second beam splitter combines the object light and the reference light and sends them into the streak camera, which has ultra-high temporal resolution to record ultrafast events at the femtosecond level.
[0013] Furthermore, the compressed hologram is reproduced using a compressed sensing recovery algorithm to recover the complex amplitude distribution of the object wave at different times.
[0014] A second aspect of the present invention provides an ultrafast compressed holographic imaging method based on a streak camera, comprising:
[0015] The laser beam emitted by the laser is split into two beams: one beam is used as the object beam, and the other beam is used as the reference beam.
[0016] The object light passes through the transient scene t i The complex amplitude at time T(x′,y′,t) i The dynamic object is transformed into O(x′,y′,t). i The light wave, after being magnified by a microscope objective and a lens in the microscope tube, enters the hologram compression unit, and its complex amplitude distribution becomes O(x,y,t). i );
[0017] After the reference light passes through a specially designed pinhole array plate, it becomes a series of spherical waves with different propagation directions. These spherical waves pass through a convex lens and become a series of plane waves propagating in different directions. Then, after passing through a cylindrical lens along the x-direction, they become a collection of long strip-shaped plane waves with different incident directions, which are connected but do not overlap, near the focal plane of the cylindrical lens. The total complex amplitude distribution is R(x,y).
[0018] t i The object light and reference light at different times are combined by the second beam splitter and enter the slit of the streak camera. They interfere with each other at the slit of the streak camera to form a hologram. These holograms formed at different times are cut by the streak camera and then cross-superimposed on the CCD plane to form a compressed hologram.
[0019] Furthermore, by using a recovery algorithm based on compressed sensing (CS) to reconstruct the compressed hologram, the complex amplitude distribution of the object wave at different times can be recovered.
[0020] The beneficial effects of the above embodiments of the present invention are as follows:
[0021] This invention proposes an ultrafast compressed holographic imaging system based on a streak camera. This system utilizes a specially "coded" reference light to achieve holographic recording of ultrafast events. Compared to traditional holographic recording optical paths, this invention employs a simple optical system consisting of a specially designed pinhole array and cylindrical lenses to "code" the reference light. The encoded reference light interferes with the object light, and the streak camera compresses and shears the light to obtain a compressed hologram. Finally, a recovery algorithm based on compressed sensing is used to recover the complex amplitude distribution of the object wave at different times. Based on the ultrashort temporal resolution of the streak camera, this system can achieve an imaging speed of tens of trillions of frames per second, recording hundreds of holographic images in a single run. This provides a new technical means for the real-time observation and research of various transient processes in physics, chemistry, and biology.
[0022] Traditional holographic recording optical paths can only record one holographic image at a time. To address the significant challenge of recording multiple holograms, this invention improves the reference light path of traditional holography. In the reference light path, an encoding unit composed of a pinhole array plate, a convex lens, a mirror, and a cylindrical lens is designed. This unit "encodes" the reference light, resulting in a set of long, non-overlapping plane waves with different incident directions. Simultaneously, a common image sensor (such as a CCD) is replaced with a streak camera. The clipping function of the streak camera enables the recording of compressed holograms, which can then be "decoded" using compressed sensing algorithms. This achieves the goal of recording multiple holographic images in an ultrafast process in a single measurement using the holographic optical path. Attached Figure Description
[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.
[0024] Figure 1 This is a structural diagram of the ultrafast compressed holographic imaging system according to Embodiment 1 of the present invention;
[0025] Figure 2 This is a schematic diagram of the pinhole array in the ultrafast compressed holographic imaging system of Embodiment 1 of the present invention;
[0026] Figure 3 The intensity distribution diagram of reference light is shown in Embodiment 1 of the present invention;
[0027] Figure 4 This is a phase distribution diagram of the reference light in Embodiment 1 of the present invention;
[0028] Figure 5 The compressed hologram obtained in Embodiment 1 of the present invention;
[0029] Figure 6These are scene diagrams reconstructed at different times according to Embodiment 1 of the present invention. Detailed implementation method:
[0030] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.
[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0032] Example 1:
[0033] Embodiment 1 of the present invention provides an ultrafast compressed holographic imaging system based on a streak camera, comprising: a laser emitting unit, an object light optical path unit, a reference light optical path unit, and a hologram compression unit. For example... Figure 1 As shown, the laser emitting unit includes an ultrafast laser (Laser) and a beam splitter (BS1). The object light optical path unit includes a second reflecting mirror (M2), a dynamic object (Obj), a microscope objective (MO), and a tube lens (TL), arranged in sequence. The reference light optical path unit includes a pinhole array plate (SF), a convex lens (L1), a first reflecting mirror (M1), and a cylindrical lens (CL) placed in the x-direction, arranged in sequence. The hologram compression unit includes a second beam splitter (BS2) and a streak camera (SC).
[0034] As a further technical solution, the laser emitted by the laser is collimated by a pinhole filter and then becomes parallel light. After passing through the beam splitter BS1, it is split into two paths. One path enters the object light optical path unit as the object light, and the other path enters the reference light optical path unit as the reference light. The reference light optical path unit "encodes" the reference light, and the reference light and the object light output from the object light optical path unit interfere with each other in the hologram compression unit to form a compressed hologram.
[0035] Preferably, in the object-optical path unit, the object light passes through the transient scene t i The complex amplitude at time T(x′,y′,t) i The dynamic object is transformed into O(x′,y′,t). i The object light wave, after being magnified by a system consisting of a microscope objective and a lens barrel, enters the hologram compression unit. Specifically, the object light wave is expanded by the microscope objective MO and the lens barrel TL, and then combined by the beam splitter BS2 before reaching the slit of the streak camera. Its complex amplitude distribution becomes O(x,y,t). i ).
[0036] Preferably, in the reference light optical path unit, the collimated parallel light passes through as follows: Figure 2 After passing through the pinhole array plate SF, the waves become a series of spherical waves with different propagation directions. After passing through the convex lens L1, these spherical waves become a series of plane waves propagating in different directions. Then, after passing through the cylindrical lens CL along the x-direction, they become a collection of long strip-shaped plane waves with different incident directions, which are connected but do not overlap, near the focal plane of the cylindrical lens. The total complex amplitude distribution is R(x,y).
[0037] As a further technical solution, t i The object light at a given moment and the encoded reference light interfere with each other at the slit of the fringe camera after passing through a beam splitter to form a hologram, the intensity distribution of which is as follows:
[0038]
[0039] x, y are spatial coordinates, t is the time coordinate, and i is an integer representing the time sequence number of the image; R * (x,y), O * (x,y,t i R(x,y) and O(x,y,t) are respectively. i The conjugate term of ) . After the hologram is cut by a streak camera, it is cross-stacked on the recording plane to obtain a compressed hologram, t i The intensity distribution of the hologram on the time-recording plane is as follows
[0040] I s (x,y,t i )=I(x,y-il,t i (2)
[0041] Where l is the single cut length of the fringe camera. The total light intensity distribution on the CCD recording plane after the holograms at all times are cut by the fringe camera is:
[0042]
[0043] As a further technical solution, we use compressed sensing algorithms (such as TwIST) to reconstruct compressed holograms and recover the complex amplitude distribution of the object wave at different times.
[0044] To achieve the reconstruction of the compressed hologram, i.e., to separate and reconstruct the compressed image, the center coordinates of the +1 order spatial spectrum of the hologram formed by the interference of the object light and the reference light at each moment must deviate to a certain extent and not completely coincide. If the spectra coincide, the prior condition for successfully separating and reconstructing the compressed hologram fails, and the reconstruction of the compressed image cannot be achieved. Therefore, this invention designs an array plate with a special pinhole distribution to "encode" the reference light to meet this requirement. All pinholes in the pinhole array have a diameter of d, where the position coordinates of the nth pinhole are (x... n ,y n Its position coordinates are determined by the main parameters of the stripe camera, such as the size of the CCD pixels, the total number of pixels, the slit width, and the shear length.
[0045] Let the pixel size of the streak camera CCD be Δx=Δy=Δ, the number of pixels be M*N, the slit width be L (number of pixels), the shear length be l (number of pixels), the incident laser wavelength be λ, and the focal lengths of the convex lens and the cylindrical lens be f. Based on the CCD parameters, the minimum and maximum values of the angle between the incident direction of the reference light and the x-direction can be calculated. Typical values are as follows:
[0046]
[0047]
[0048] exist Between them After dividing into equal parts, a series of offset angles can be obtained.
[0049]
[0050] Thus, the horizontal and vertical coordinates of the pinhole array can be calculated.
[0051]
[0052] [y1,y2,...,y n ]=[Δ,2Δ,...,nΔ] (8)
[0053] To verify the feasibility of the above method, we conducted an experimental simulation using 10 frames of blooming lotus flowers as a dynamic scene. In the simulation, the pixel size of the streak camera CCD was set to 5µm, the pixel count was 2048*2048, the incident laser wavelength was 532nm, and the focal lengths of both the convex and cylindrical lenses were 10cm. The series of angles between the incident direction of the reference light and the x-direction are then...
[0054]
[0055] The location of the pinhole array can be determined from this. The intensity and phase distribution of the reference light are as follows: Figure 3 , 4 As shown, the stripe camera records compressed holograms as follows: Figure 5 As shown, the amplitude and phase distribution maps of the scene at different times were successfully separated and reconstructed using a recovery algorithm based on compressed sensing, as shown in the figure. Figure 6 As shown in the figure. Simulation results demonstrate that this imaging system can successfully record holograms of dynamic scenes at different times, simultaneously recording both the intensity and phase information of the dynamic scene. Using a streak camera, an ultrafast imaging speed of trillions of frames per second can be achieved, successfully enabling single-shot recording of transient events and ultrafast phenomena.
[0056] Example 2:
[0057] Embodiment 2 of the present invention provides an ultrafast compressed holographic imaging method based on a streak camera, comprising:
[0058] The laser beam emitted by the laser is split into two beams: one beam is used as the object beam, and the other beam is used as the reference beam.
[0059] The object light passes through the transient scene t i The complex amplitude at time T(x′,y′,t) i The dynamic object is transformed into O(x′,y′,t). i The light wave, after being magnified by a microscope objective and a lens in the microscope tube, enters the hologram compression unit, and its complex amplitude distribution becomes O(x,y,t). i );
[0060] After the reference light passes through the pinhole array plate, it becomes a series of spherical waves with different propagation directions. After passing through the convex lens, these spherical waves become a series of plane waves propagating in different directions. Then, after passing through the cylindrical lens along the x-direction, they become a collection of long strip-shaped plane waves with different incident directions, which are connected but do not overlap near the focal plane of the cylindrical lens. The total complex amplitude distribution is R(x,y).
[0061] The reference light and the object light interfere with each other on the CCD plane of the streak camera to form a hologram, which is then cut by the streak camera to obtain a compressed hologram.
[0062] As a further technical solution, the compressed hologram is reproduced using the recovery algorithm of compressed sensing to recover the complex amplitude distribution of the object wave at different times.
[0063] The steps and methods described in Embodiment 2 correspond to those in Embodiment 1. For detailed implementation methods, please refer to the relevant descriptions in Embodiment 1. Those skilled in the art should understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any specific combination of hardware and software.
[0064] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.
Claims
1. An ultrafast compressed holographic imaging system based on a streak camera, characterized in that, include: Laser emitting unit, object light optical path unit, reference light optical path unit, and hologram compression unit; The laser emitting unit splits the emitted laser into two paths: one path enters the object light optical path unit as the object light, and the other path enters the reference light optical path unit as the reference light. The reference light optical path unit encodes the reference light and interferes with the object light output from the object light optical path unit at different times to form a sequence of holograms. After being compressed by the hologram compression unit, a compressed hologram is obtained. The reference light optical path unit includes a pinhole array plate, a convex lens, a first reflecting mirror, and a cylindrical lens arranged in sequence.
2. The ultrafast compressed holographic imaging system based on a streak camera as described in claim 1, characterized in that, The laser emitting unit includes a laser and a beam splitter. The laser emitted by the laser is collimated by a pinhole filter and then becomes parallel light. After passing through the first beam splitter, it is split into two paths.
3. The ultrafast compressed holographic imaging system based on a streak camera as described in claim 1, characterized in that, The object-optical path unit includes a second reflecting mirror, a dynamic object, a microscope objective, and a microscope tube lens arranged in sequence.
4. The ultrafast compressed holographic imaging system based on a streak camera as described in claim 3, characterized in that, Object light passing through a transient scene The complex amplitude at time is The dynamic object then becomes a light wave. The light wave, after being magnified by a microscope objective and a lens in the microscope tube, enters the hologram compression unit, and its complex amplitude distribution becomes... .
5. The ultrafast compressed holographic imaging system based on a streak camera as described in claim 1, characterized in that, After the reference light passes through the pinhole array plate, it becomes a series of spherical waves with different propagation directions. These spherical waves then pass through a convex lens and become a series of plane waves propagating in different directions. Then, they pass through... Behind a cylindrical lens, near the focal plane of the lens, the wave becomes a collection of elongated plane waves with different incident directions, which are adjacent but do not overlap. The total complex amplitude distribution is as follows: .
6. The ultrafast compressed holographic imaging system based on a streak camera as described in claim 1, characterized in that, The hologram compression unit includes a second beam splitter and a streak camera; The object light and reference light at a given time coherently coherently form a hologram at the slit of the streak camera after passing through the second beam splitter. The hologram is then clipped by the streak camera and cross-stacked on the recording plane to obtain a compressed hologram.
7. The ultrafast compressed holographic imaging system based on a streak camera as described in claim 6, characterized in that, The compressed hologram was reconstructed using a compressed sensing recovery algorithm to recover the complex amplitude distribution of the object wave at different times.
8. An ultrafast compressed holographic imaging method based on a streak camera, characterized in that, Includes the following steps: The laser beam emitted by the laser is split into two beams: one beam is used as the object beam, and the other beam is used as the reference beam. Object light passing through a transient scene The complex amplitude at time is The dynamic object then becomes a light wave. The light wave, after being magnified by a microscope objective and a lens in the microscope tube, enters the hologram compression unit, and its complex amplitude distribution becomes... ; After the reference light passes through the pinhole array plate, it becomes a series of spherical waves with different propagation directions. These spherical waves then pass through a convex lens and become a series of plane waves propagating in different directions. Then, they pass through... Behind a cylindrical lens, near the focal plane of the lens, the wave becomes a collection of elongated plane waves with different incident directions, which are adjacent but do not overlap. The total complex amplitude distribution is as follows: ; The object light and reference light at different times are combined by the second beam splitter and enter the slit of the streak camera. They interfere with each other at the slit of the streak camera to form a hologram. These holograms formed at different times are cut by the streak camera and then cross-superimposed on the CCD plane to form a compressed hologram.
9. The ultrafast compressed holographic imaging method based on a streak camera as described in claim 8, characterized in that, The compressed hologram was reconstructed using a compressed sensing recovery algorithm to recover the complex amplitude distribution of the object wave at different times.
Citation Information
Patent Citations
Hilbert transform based high-precision digital holography phase reconstruction method
CN104407507A