Holographic imaging device and system based on polarization state superposition interference

Abstract

The invention discloses holographic imaging equipment and system based on polarization state superposition interference, and relates to the technical field of holographic imaging, the holographic imaging equipment comprises a light source, an initial polarization state preparation module, a to-be-measured object modulation module, a polarization projection measurement module and a camera which are coaxially arranged in sequence; light emitted by the light source enters the initial polarization state preparation module to be prepared to be in a diagonal polarization state and then enters the to-be-measured object modulation module, light modulated by a to-be-measured object enters the polarization projection measurement module, the polarization projection measurement module projects two irrelevant orthogonal polarization states to the same polarization basis vector, and the to-be-measured object is measured. Finally, interference occurs on the polarization basis vector, an interference pattern is formed and collected by a camera, and the camera transmits the collected hologram to a processor; and the processor reconstructs the collected hologram into a phase image of the object to be measured through a holographic imaging method based on polarization state superposition interference. Through realizing strict common path of object light and reference light on a propagation path, the inhibition capability of the system on path phase noise is obviously improved.

Description

Technical Field

[0001] This invention relates to the field of holographic imaging technology, and in particular to holographic imaging devices and systems based on polarization state superposition interference. Background Technology

[0002] The statements in this section are merely background information relating to this disclosure and do not necessarily constitute prior art.

[0003] Holography is a technique that uses the principle of interference to record the amplitude and phase information of an object's light wave, and then reconstructs it through diffraction. It is widely used in fields such as anti-counterfeiting, imaging, and data storage. Unlike traditional imaging, which can only record the amplitude information of an object but loses phase information, holography can record and reconstruct the wavefront information of an object. However, in traditional coaxial holography, the coaxial propagation structure of the object light and reference light causes the original image and conjugate image to overlap and become inseparable during reconstruction, resulting in low image sharpness and contrast.

[0004] To address the above issues, several improvements have been proposed in existing technologies. One improvement in measurement methods involves introducing multi-step phase shifting. This involves acquiring multiple interferograms with different phase differences and then using algorithms to analyze and eliminate twin image interference. However, this method requires high precision and stability in system phase control and suffers from poor real-time performance. Another improvement in imaging systems is off-axis holography. By incident the reference and object beams at a specific angle, it effectively eliminates twin image interference by separating diffraction terms in the spatial frequency domain. However, this method requires high stability of the optical path. Co-path off-axis holography, by having the reference and object beams originate from the same beam and share most of the optical path, generates off-axis interference internally through diffractive optical elements. This method combines the high stability of coaxial optical paths with the advantages of off-axis methods in eliminating twin image effects.

[0005] However, the inventors discovered that in currently common co-path off-axis holographic systems, in order to achieve effective off-axis interference, it is difficult for the object beam and reference beam to achieve completely strict co-path propagation physically. This non-ideal co-path characteristic means that the two beams' ability to cancel out disturbances along the common path is not optimal, and the stability of the system in practical applications still has room for further improvement. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a holographic imaging device and system based on polarization state superposition interference. By loading the object under test into a polarization state subspace independent of the spatial position domain, the object light and the reference light are strictly co-pathed in the propagation path, thereby significantly improving the system's ability to suppress path phase noise and providing a new technical idea and implementation approach for high-stability holographic imaging.

[0007] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: In a first aspect, the present invention provides a holographic imaging device based on polarization state superposition interference, comprising a light source, an initial polarization state preparation module, a target object modulation module, a polarization projection measurement module, and a camera arranged coaxially in sequence; The photons emitted by the light source enter the initial polarization state preparation module and are prepared into a diagonally polarized state. The diagonally polarized light then enters the object under test modulation module. The photons modulated by the object under test then enter the polarization projection measurement module. The polarization projection measurement module projects two incoherent orthogonal polarization states onto the same polarization basis vector. Finally, interference occurs on this polarization basis vector, forming an interference pattern that is captured by the camera. The camera transmits the captured hologram to the processor. The processor is configured to reconstruct the phase image of the object under test from the acquired hologram using a holographic imaging method based on polarization state superposition interference.

[0008] In a further technical solution, the initial polarization state preparation module and the polarization projection measurement module have the same structure, both including at least one optical polarization modulation device.

[0009] In a further technical solution, the object-to-measure modulation module is a phase-type spatial light modulator, which loads the phase information of the object to be measured into the horizontal polarization state component of the diagonally polarized light, and simultaneously applies a linear phase factor to the vertical polarization state component to form a polarization modulation beam carrying the object information, which then enters the polarization projection measurement module.

[0010] A further technical solution, the holographic imaging method based on polarization state superposition interference, specifically includes the following steps: Obtain empty holograms and object holograms; Preprocessing of the spatial hologram and the object hologram yields a difference hologram; After performing frequency domain transformation, spectrum centering and frequency domain filtering on the difference hologram in sequence, the filtered object light signal spectrum is obtained. The filtered object light signal spectrum is then subjected to inverse frequency domain transformation to obtain the phase object information to be measured. Reconstruct the phase image of the object under test based on the phase information of the object under test.

[0011] A further technical solution is that when the modulation module of the object under test is in a no-modulation state without loading any object, it acquires an empty hologram; when the modulation module of the object under test loads the phase information of the object under test, it acquires an object hologram.

[0012] A further technical solution for acquiring object holograms is as follows: The initial polarization state preparation module prepares the polarization state of the incident light into a diagonally polarized state containing horizontal and vertical polarization components in equal proportions; The object-to-test modulation module loads the phase information of the object to be tested into the horizontal polarization component of the photon, and at the same time applies a linear phase factor to the vertical polarization component of the photon to form a polarization modulation beam carrying the object information. A polarization-modulated beam is incident on the polarization projection measurement module. Two orthogonal polarization states interfere on the same polarization basis, forming an interference pattern. The interference image is captured by a camera to obtain a hologram of the object.

[0013] A further technical solution involves performing a two-dimensional fast Fourier transform on the difference hologram to convert the interference fringes in real space into a frequency domain spectrum.

[0014] A further technical solution involves centering the spectrum by calling the fftshift function to shift the spectrum of the object optical signal to the center position in the frequency domain.

[0015] A further technical solution is that the frequency domain filtering specifically involves: designing a circular Gaussian filter based on the full width at half maximum (FWHM) of the object optical signal spectrum, and filtering the spectrum-centered signal based on the circular Gaussian filter to obtain the filtered object optical signal spectrum.

[0016] Secondly, the present invention provides a holographic imaging system based on polarization state superposition interference, comprising: The image acquisition module is configured to acquire spatial holograms and object holograms using a holographic imaging device based on polarization state superposition interference; The preprocessing module is configured to preprocess the empty hologram and the object hologram to obtain a difference hologram. The phase extraction module is configured to: sequentially perform frequency domain transformation, spectrum centering and frequency domain filtering on the difference hologram to obtain the filtered object light signal spectrum; and perform inverse frequency domain transformation on the filtered object light signal spectrum to obtain the phase information of the object to be measured. The image reconstruction module is configured to reconstruct the phase image of the object under test based on the phase object information.

[0017] The above one or more technical solutions have the following beneficial effects: This invention eliminates path differences through a strictly shared-path structure, significantly improving path noise suppression and overcoming the stability bottleneck of non-ideal shared-path systems. Existing shared-path off-axis holographic systems suffer from limited ability to counteract path disturbances such as vibration and air disturbances because the object beam and reference beam cannot achieve complete physical shared-path propagation. They require high-precision mechanical vibration isolation devices to maintain stable interference. The holographic imaging device of this invention loads the information of the object under test into a polarization state subspace independent of the spatial position domain, allowing the object beam and reference beam to share the entire physical propagation path. This results in higher stability than traditional off-axis holographic systems and enables highly stable interference in ordinary laboratory environments without the need for additional vibration isolation devices, significantly lowering the system's environmental requirements.

[0018] The holographic imaging device in this invention has low setup complexity and low operation difficulty, and is simple and easy to operate. Existing holographic solutions generally require multiple sets of optical components, such as mirrors, beam splitters, and phase controllers, to achieve interference matching between the object beam and the reference beam. The optical path adjustment depends on manually calibrating the incident and angles of the object beam and the reference beam. A single setup requires several hours of repeated debugging, and recalibration is required after slight mechanical vibrations or temperature changes, which places extremely high demands on the professional skills of the operators. This invention relies on the design of loading object information into the polarization subspace. The object beam and the reference beam share the entire physical optical path from the light source to the camera in the form of orthogonal polarization components. There is no need to design an additional independent reference beam path, nor is it necessary to adjust the incident angles of the object beam and the reference beam. This shortens the optical path setup time and avoids the trouble of repeated calibration, significantly reducing the operating threshold.

[0019] This invention overcomes the real-time bottleneck of existing multi-step phase-shifting techniques by combining single-frame interferometric recording with real-time data processing, providing a practical technical path for high-frame-rate imaging of dynamic samples. Existing multi-step phase-shifting techniques require acquiring 3-4 interferometric images with different phase differences to eliminate twin image interference, completely failing to capture the instantaneous changes of dynamic samples; furthermore, subsequent data processing requires manual matching of phase information across multiple frames, resulting in a lack of real-time performance. This invention, through the design of a polarization projection measurement module, projects orthogonal polarization components onto the same basis vector, allowing a single-frame interferometric pattern to completely record the amplitude and phase information of the object, eliminating the need for multi-step phase shifting. The acquisition time for a single frame depends only on the camera exposure time. The corresponding image processing methods employ lightweight preprocessing workflows such as automatic empty image denoising and fast FFT algorithms, achieving a total processing time of <100ms / frame. Combined with the camera's in-camera trigger acquisition frequency, it is expected to achieve synchronous acquisition, processing, and display, providing a highly efficient new solution for rapid dynamic imaging. Attached Figure Description

[0020] 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.

[0021] Figure 1 This is a structural diagram of a holographic imaging device based on polarization state superposition interference according to an embodiment of the present invention; Figure 2 This is a flowchart of a holographic imaging device based on polarization state superposition interference according to an embodiment of the present invention; Figure 3 This is a flowchart of a holographic imaging method based on polarization state superposition interference according to an embodiment of the present invention. Detailed Implementation

[0022] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. 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 invention pertains.

[0023] 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 scope of exemplary embodiments according to the invention. 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.

[0024] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0025] Example 1 like Figure 1 As shown, this embodiment discloses a holographic imaging device based on polarization state superposition interference, including a light source, an initial polarization state preparation module, a target object modulation module, a polarization projection measurement module, and a camera arranged coaxially in sequence; The light source is used to emit incident photons; the initial polarization state preparation module is used to prepare the polarization state of the incident photons into a diagonally polarized state containing horizontal and vertical polarization state components in equal proportion; the object-to-measure modulation module is used to modulate the spatial phase of the incident light wave, that is, to load the spatial phase information of the object to be measured into the phase difference between the two orthogonal polarization states of the photon; the polarization projection measurement module is used to project the two orthogonal polarization components in the polarization modulation beam carrying the object information onto the same polarization basis, so that the two orthogonal polarization components satisfy the interference condition and form an interference pattern; the camera is used to acquire the interference pattern (hologram).

[0026] Photons emitted from the light source enter the initial polarization state preparation module and are prepared into a diagonally polarized state. The diagonally polarized light then enters the object-to-test modulation module. The photons whose polarization state has been modulated by the object-to-test then enter the polarization projection measurement module. This module projects two incoherent orthogonal polarization states onto the same polarization basis, and finally interference occurs on this polarization basis, forming an interference pattern that is captured by the camera. The hologram captured by the camera is transmitted to the processor. The processor is configured to reconstruct the phase image of the object-to-test from the captured hologram using a holographic imaging method based on polarization state superposition interference. Specifically, based on the parameter settings of the initial polarization state preparation module, the polarization state of the incident photon is prepared as a diagonal polarization state. The diagonally polarized light prepared by the above process is incident on the object-to-measure modulation module. The beam interacts with the object, and its polarization state is modulated by the spatial phase information of the object, forming a polarization-modulated beam carrying the object's information. The polarization-modulated beam enters the polarization projection measurement module, which projects the two orthogonal polarization components contained in the beam onto the same preset polarization basis, so that the originally incoherent orthogonal polarization components satisfy the interference condition on the basis, forming interference fringes. The camera is triggered to operate in internal trigger mode. The camera generates a trigger signal according to the internal timing sequence, exposes and acquires the above-mentioned polarization state superposition interference pattern, and transmits the acquired hologram data to the processor.

[0027] The initial polarization state preparation module and the polarization projection measurement module adopt the same structure, both of which include one or a combination of optical polarization modulation devices.

[0028] In some implementations, the light source is a He-Ne laser, the initial polarization state preparation module includes a collimating beam expander (composed of a pinhole spatial filter and a beam expander lens group) and a half-wave plate, the object-to-measure modulation module is a phase-type spatial light modulator (used to modulate the spatial phase of the incident light wave), the polarization projection measurement module includes a polarizer, a first lens and a second lens, and an ICCD camera. The center points of the light source, collimating beam expander, half-wave plate, phase-type spatial light modulator, lens 1, lens 2, and ICCD camera are all on the same straight line.

[0029] The light emitted from the He-Ne laser, after passing through a collimating and beam-expanding device, becomes a linearly polarized beam with high homogeneity and parallelism. To meet the subsequent interference conditions, a half-wave plate is used to adjust the polarization state of the linearly polarized light, utilizing the polarization rotation characteristics of the half-wave plate to adjust the beam to a diagonally polarized state. Subsequently, this linearly polarized beam is incident on a phase-type spatial light modulator (SLM). The phase information of the phase object to be measured has been loaded onto the SLM in a gray-scale-phase mapping mode. Linearly polarized light can be decomposed into two orthogonal polarization components within the SLM plane. Since a phase-type SLM only modulates the phase of the beam without changing its amplitude, the two orthogonal polarization components carry phase information of the object being measured. To ensure that the two orthogonal polarization components satisfy the interference condition of "aligned vibration directions," the modulated beam is incident onto a... A linearly polarized filter is used to project two orthogonal components onto the same vibration direction, thereby generating stable interference fringes and forming a hologram containing the phase information to be measured. To achieve high-fidelity recording of the hologram, a 4f optical system consisting of two achromatic Fourier lenses with the same focal length, 1 (first lens) and 2 (second lens), is used to achieve high-fidelity imaging of the SLM plane onto the target surface of an enhancement-coupled device (ICCD). The ICCD operates in low-light detection mode, which can efficiently acquire low-intensity holograms generated by interference, ultimately completing the recording of the holographic information of the phase object to be measured.

[0030] It should be noted that the beam does not emphasize the quantum nature of photons, whereas the classical light source emitted by the laser focuses on the quantum mechanical description of photons.

[0031] In this embodiment, the holographic imaging method based on polarization state superposition interference includes the following specific steps: S1: Obtain the empty hologram and the object hologram; S101: On the optical platform, fix each component sequentially according to the optical path order: light source, initial polarization state preparation module, object under test modulation module, polarization projection measurement module, and ICCD. This completes the physical construction of the optical path, ensuring that the centers of all optical components are at the same height, guaranteeing that the laser beam propagates without offset along the optical axis. Adjust the parameters of the initial polarization state preparation module and the polarization projection module to meet the requirements of interferometric imaging, ensuring that the subsequent beam polarization state is controllable and the interference conditions meet the standards.

[0032] S102: Start the ICCD control software, set the trigger mode, exposure time, and storage path; start the SLM control software, ensuring the SLM is in a modulated-free state without any loaded objects. After confirming the parameters are correct, execute the acquisition process and record the empty hologram acquired under the set ICCD parameters, which effectively reflects the inherent background noise of the system.

[0033] S103: Load the phase information of the object under test into the effective imaging area of ​​the SLM in the object modulation module, keep the camera parameters completely consistent with those in S102, only modify the storage path and file name, and acquire a hologram containing the object information to ensure that the object phase is effectively recorded.

[0034] The effective recording of object holograms using polarization state superposition interferometry includes: The initial polarization state preparation module prepares the incident photon into a diagonally polarized state. ,in and These represent the horizontal and vertical polarization state components, respectively. Since the SLM in the object-under-test modulation module can only modulate the horizontal polarization state of photons, and has no modulation effect on the vertical polarization state, the SLM will transmit the phase information of the object under test. Horizontal polarization state loaded onto photons In this process, the horizontal polarization component carries the phase information of the object.

[0035] To achieve single-frame holographic recording, the vertical polarization state... Apply an artificially introduced linear phase factor ,in, This represents the spatial frequency introduced by off-axis interference. The linear phase factor, representing the two-dimensional spatial coordinate vector of the imaging plane, is used to simulate the phase distribution of the reference light in off-axis holography, thus achieving off-axis interference between the object light and the reference light. At this point, the photon quantum state after SLM modulation is: The modulated beam described above is incident on the polarization projection measurement module, and the two orthogonal polarization states are... Interference occurs on the polarization basis vectors, and the intensity distribution of the resulting interference pattern satisfies: The interference pattern is acquired and recorded by an ICCD, completing the recording process of the object hologram.

[0036] S2: Preprocess the empty hologram and the object hologram to obtain the difference hologram; Preprocessing involves removing the inherent background noise from both the empty hologram and the object hologram, and then using the arithmetic mean of the empty hologram as the background reference image. The hologram of an object, after being arithmetically averaged, is defined as an object-information map. The difference hologram is obtained by subtracting the grayscale values ​​from the two values. ,in, The coordinates of the imaging plane are two-dimensional. This operation can effectively eliminate inherent background noise of the system, including non-uniform spatial distribution of light source intensity, dark current of ICCD detectors, and stray light generated by scattering from the surface of optical elements, etc. Only the interference signal related to the object under test is retained.

[0037] S3: After performing frequency domain transformation, spectrum centering and frequency domain filtering on the difference hologram in sequence, the filtered object light signal spectrum is obtained. The filtered object light signal spectrum is then subjected to inverse frequency domain transformation to obtain the phase information of the object to be measured. In holographic imaging, the core difference between off-axis digital holography and coaxial holography lies in the optical path interference structure. Off-axis holography forms spatially separated spectra (zero order and ±1 order) through the oblique incidence of the object beam and the reference beam, which is naturally suitable for frequency filtering. However, in traditional coaxial holography, because the object beam and the reference beam are coaxial, the zero-order DC component, the object beam signal (+1 order), and the conjugate image (-1 order) highly overlap in the frequency domain, making it difficult to directly apply frequency filtering methods. In this invention, the encoding of the polarization subspace gives the object beam signal a unique frequency domain identifier through polarization state modulation, breaking through the frequency domain aliasing bottleneck of traditional coaxial holography and innovatively using frequency filtering to obtain the spectrum of the object beam signal.

[0038] S301: Frequency domain transformation. For difference holograms Performing a two-dimensional fast Fourier transform converts the interference fringes in real space into a frequency domain spectrum, the mathematical expression of which is:

[0039] in, Represents the difference hologram The frequency domain spectrum distribution obtained after two-dimensional fast Fourier transform, This represents the two-dimensional frequency coordinate vector transformed into the frequency domain by the Fast Fourier Transform. This represents the two-dimensional Fast Fourier Transform operator. The two-dimensional spatial coordinate vector representing the imaging plane. The amplitude of the DC component is determined by the incident light intensity and the system transmittance. This represents the Dirac function, which represents the zero-order DC component; This represents the spatial frequency introduced by off-axis interference. The frequency domain representation of the object's light field.

[0040] S302: Spectrum Centering. Due to the spectral separation characteristics of off-axis interference, the object light signal spectrum, conjugate image spectrum, and zeroth-order DC component are symmetrically distributed in the frequency domain. Spectrum centering is achieved by calling the `fftshift` function, shifting the object light signal spectrum to the center position in the frequency domain, resulting in:

[0041] in, This represents the spectral distribution of the object-optical signal after spectral centering. This represents a frequency domain signal that has not undergone centralization.

[0042] This step provides a spatial positioning reference for subsequent frequency domain filtering, ensuring the accuracy of object-optical signal extraction.

[0043] S303: Spectrum filtering. Based on the full width at half maximum (FWHM) and full width at half maximum (FWHM) of the object optical signal spectrum. Design radius is A circular Gaussian filter, through filtering operations:

[0044] in, This represents the frequency domain distribution of the pure object optical signal obtained after spectral centering and Gaussian filtering. The transfer function of a Gaussian filter is represented by... This represents the frequency domain distribution of the pure object optical signal obtained after spectral centering and Gaussian filtering.

[0045] Furthermore, in the centralized spectrum In the process, the location of the spectral peak corresponding to the object optical signal is identified as the energy concentration region of the object optical spectrum. The spectral intensity distribution curve along the main distribution direction where the spectral peak is located is then extracted. First, determine the peak intensity of the intensity curve. Then find the strength as The two frequency coordinates corresponding to (half-height) and (located on both sides of the peak), then the full width at half height is... .

[0046] It can completely filter out the zero-order DC component and the conjugate image spectrum, retaining only the core spectrum of the object light signal. At the same time, it suppresses high-frequency noise through the smoothing characteristics of Gaussian filtering, preserving the detailed information of the object phase to the maximum extent.

[0047] Spectrum of the filtered object optical signal Perform a two-dimensional inverse fast Fourier transform to obtain the phase information of the object under test:

[0048] in, This represents the two-dimensional fast inverse Fourier transform operator.

[0049] S4: Reconstruct the phase image of the object under test based on the phase information of the object under test.

[0050] The phase image of the object under test is reconstructed and output based on the inverse transform result, which is the target phase object holographic image.

[0051] In summary, the parameters for each step are determined based on experimental verification and theoretical derivation, possessing clear mathematical basis and engineering feasibility; the entire process is executed automatically by the processor, avoiding human error and improving detection repeatability and stability; the final output phase image directly reflects the information of the object under test, providing highly reliable raw data support for subsequent application stages.

[0052] Example 2 This embodiment provides a holographic imaging system based on polarization state superposition interference, including: The image acquisition module is configured to acquire spatial holograms and object holograms using a holographic imaging device based on polarization state superposition interference; In this embodiment, a control module is also included. The control module is electrically connected to the camera and is configured to use the camera's internal trigger mode. The trigger signal is generated by the camera itself and directly controls exposure and image acquisition without relying on external devices (such as sensors, motion controllers, etc.) to provide signals. In other words, the control module takes the camera's automatic timing synchronization as its core and is based on the ICCD's built-in internal trigger function. The trigger signal is generated by the ICCD's internal timing generator, realizing imaging control without external dependence.

[0053] The preprocessing module is configured to preprocess the empty hologram and the object hologram to obtain a difference hologram. The phase extraction module is configured to: sequentially perform frequency domain transformation, spectrum centering and frequency domain filtering on the difference hologram to obtain the filtered object light signal spectrum; and perform inverse frequency domain transformation on the filtered object light signal spectrum to obtain the phase information of the object to be measured. The image reconstruction module is configured to reconstruct the phase image of the object under test based on the phase object information.

[0054] In this embodiment, the data acquired by the holographic imaging device based on polarization state superposition interference is transmitted to the processor for data processing. The processor is connected to the camera and includes a preprocessing module, a phase extraction module, and an image reconstruction module, ultimately outputting the phase image of the object under test. The preprocessing module eliminates noise such as uneven light source, background interference, and hardware defects by subtracting the hologram containing object information acquired by the camera from the empty hologram recorded when there is no object, providing high-quality input for subsequent processing. The phase extraction module separates the object light signal through mathematical transformation and then selects a filter of appropriate size to extract the object signal, completing the process of parsing the core phase information of the object from the signal. The image reconstruction module generates the phase image of the object based on the extracted object information and quantifies its physical parameters, completing the entire process from interference fringes to phase reconstruction.

[0055] The holographic imaging device based on polarization state superposition interference provides the hardware foundation for the system from light field modulation to interferometric imaging. The control module realizes the timing control of the image acquisition process, and the processor completes the phase analysis and image reconstruction of the hologram. The three work together to realize high-precision phase imaging of phase objects.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0057] 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. A holographic imaging device based on polarization state superimposed interference, characterized in that, The light source, the initial polarization state preparation module, the object to be measured modulation module, the polarization projection measurement module and the camera are arranged coaxially in sequence. The photons emitted by the light source are prepared into diagonal polarization states by the initial polarization state preparation module, and then the diagonal polarization light enters the object to be measured modulation module. The photons modulated by the object to be measured enter the polarization projection measurement module. The polarization projection measurement module projects two incoherent orthogonal polarization states onto the same polarization basis vector, and finally interference occurs on the polarization basis vector to form an interference pattern which is collected by the camera. The camera transmits the collected hologram to the processor. The processor is configured to reconstruct the collected hologram into a phase image of the object to be measured by a polarization state superposition interference-based holographic imaging method.

2. The polarization state superposition interference based holographic imaging device of claim 1, wherein, The initial polarization state preparation module and the polarization projection measurement module have the same structure and comprise at least one optical polarization modulation device.

3. The polarization state superposition interference based holographic imaging device of claim 1, wherein, The object to be measured modulation module is a phase-type spatial light modulator which loads the phase information of the object to be measured into the horizontal polarization component of the diagonal polarization light, and simultaneously applies a linear phase factor to the vertical polarization component to form a polarization modulation light beam carrying object information, which then enters the polarization projection measurement module.

4. The polarization state superposition interference based holographic imaging device of claim 1, wherein, The polarization state superposition interference-based holographic imaging method comprises the following steps: acquiring an empty hologram and an object hologram; preprocessing the empty hologram and the object hologram to obtain a difference hologram; after the difference hologram is sequentially subjected to frequency domain transformation, spectrum centering and frequency domain filtering, a filtered object light signal spectrum is obtained, and the filtered object light signal spectrum is subjected to inverse frequency domain transformation to obtain the phase information of the object to be measured; reconstructing a phase image of the object to be measured based on the phase information of the object to be measured.

5. The holographic imaging device based on polarization state superposition interference as described in claim 4, characterized in that, When the object to be measured modulation module is in an unmodulated state without loading any object, the empty hologram is collected, and when the object to be measured modulation module loads the phase information of the object to be measured, the object hologram is collected.

6. The polarization state superposition interference based holographic imaging device of claim 4, wherein, The collection of the object hologram comprises the following steps: the initial polarization state preparation module prepares the polarization state of the incident light into a diagonal polarization state containing horizontal polarization components and vertical polarization components in equal proportions; the object to be measured modulation module loads the phase information of the object to be measured into the horizontal polarization component of the photon, and simultaneously applies a linear phase factor to the vertical polarization component of the photon to form a polarization modulation light beam carrying object information; the polarization modulation light beam is incident on the polarization projection measurement module, and interference occurs between the two orthogonal polarization states on the same polarization basis vector to form an interference pattern which is collected by the camera to obtain the object hologram.

7. The polarization state superposition interference based holographic imaging device of claim 4, wherein, The frequency domain transformation is a two-dimensional fast Fourier transform of the difference hologram, which converts the interference fringes in the real space into a frequency spectrum in the frequency domain.

8. The polarization state superposition interference based holographic imaging device of claim 4, wherein, The spectrum centering is to shift the object light signal spectrum to the center position in the frequency domain by calling the fftshift function.

9. The polarization state superposition interference based holographic imaging device of claim 4, wherein, The frequency domain filtering specifically comprises the following steps: designing a circular Gaussian filter based on the full width at half maximum of the object light signal spectrum, filtering the signal after the spectrum centering based on the circular Gaussian filter to obtain the filtered object light signal spectrum.

10. A holographic imaging system based on polarization state superimposed interference, characterized in that, The image acquisition module is configured to acquire an empty hologram and an object hologram by using a polarization state superposition interference-based holographic imaging device. ​ The pre-processing module is configured to pre-process the empty hologram and the object hologram to obtain a difference hologram; The phase extraction module is configured to perform frequency domain transformation, spectrum centering and frequency domain filtering on the difference hologram in sequence to obtain a filtered object light signal spectrum, and perform inverse frequency domain transformation on the filtered object light signal spectrum to obtain the phase information of the object to be measured; The image reconstruction module is configured to reconstruct a phase image of the object to be measured based on the phase information of the object to be measured.

Images