Wide-band super-rayleigh speckle correlation imaging spectrometer based on dispersion compensation and imaging method thereof

Abstract

The application relates to a wide-band super-Rayleigh speckle correlation imaging spectrometer based on dispersion compensation, and the imaging scheme comprises and is not limited to the following imaging schemes: a front compensation scheme, a rear compensation scheme or a front-rear joint compensation scheme. The device comprises a front imaging module, a filter, a phase modulation module, a relay imaging module, a surface array detector and a computer and the like. The application utilizes the dispersion characteristics of the front imaging module or the relay imaging module to cooperate with the phase modulation module to realize super-Rayleigh speckle modulation in a wide band, and applies the super-Rayleigh speckle modulation to a correlation imaging spectrometer, so that the imaging quality of the correlation imaging spectrometer under low signal-to-noise ratio is improved.

Description

Technical Field

[0001] This invention relates to a method for achieving super Rayleigh speckle modulation over a wide spectral band by utilizing the dispersion characteristics compensation of a front imaging module or a relay module, and applies it to a correlated imaging spectral camera. Background Technology

[0002] Spectral imaging technology possesses both imaging and spectral detection capabilities, acquiring the spectral distribution of various spatial points while detecting spatial information of an object, thereby effectively revealing the physicochemical properties of the target. It has broad application prospects in fields such as space remote sensing, medical biology, national defense security, and food safety. Based on different information acquisition methods, spectral imaging technology is divided into optomechanical scanning, pushbroom, staring, and snapshot imaging. Among them, snapshot spectral imaging, capable of acquiring a three-dimensional data cube under single-exposure conditions, is currently a hot topic in spectral imaging research. The mainstream snapshot spectral imaging methods can be divided into two main categories: amplitude modulation-based and phase modulation-based. Phase modulation-based methods have attracted much attention due to their highest energy efficiency.

[0003] The research group of Han Shengsheng at the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, proposed a compressed sensing broadband hyperspectral imaging system based on random gratings (patent number: ZL201410348475.X). This system encodes the spatial and spectral information of an object onto a two-dimensional detector using random gratings, enabling the acquisition of broadband spectral image information in a single exposure. However, this system employs random phase modulation, resulting in speckle patterns that follow a Rayleigh distribution, making it difficult to obtain high-quality reconstructed images at low signal-to-noise ratios. To improve the noise resistance of spectral imaging, they proposed a correlation imaging spectral camera and its imaging method based on non-Rayleigh speckle fields (patent number: CN109520619B). The super-Rayleigh speckle field with a contrast greater than 1 exhibits high contrast and strong noise resistance, possessing significant application value in improving the image quality of high-order correlation imaging. However, their proposed non-Rayleigh modulation method suffers from problems such as a narrow application spectral band and resolution and contrast degradation when the wavelength deviates from the center wavelength. This limits the application of this modulation method in spectral imaging and fails to fully leverage the noise resistance and improved reconstruction accuracy advantages of super-Rayleigh speckle. Summary of the Invention

[0004] The purpose of this invention is to achieve wide-band snapshot-type spectral correlation imaging with high detection signal-to-noise ratio, and to overcome the shortcomings of correlation imaging spectral cameras and imaging methods based on non-Rayleigh speckle fields, which have a narrow super-Rayleigh speckle modulation band and cannot fully utilize the strong noise resistance of super-Rayleigh speckle, thus limiting their application in spectral imaging. This invention proposes a wide-band super-Rayleigh correlation imaging spectral camera based on dispersion compensation.

[0005] The typical system configuration of this invention includes components such as a front imaging module, a bandpass filter, a phase modulation module, a relay imaging module, a photodetector, and a computer. Based on the conditions met by different parts, it can be divided into a front compensation scheme (where the front imaging module meets specific dispersion requirements) and a rear compensation scheme (where the relay module meets specific dispersion requirements).

[0006] The pre-imaging module or relay imaging module with specific dispersion requirements achieves wideband super Rayleigh speckle modulation using imaging relationship compensation. For the pre-compensation scheme, objects of different wavelengths are imaged onto different first imaging planes. For the post-compensation scheme, speckle at different positions after the phase modulator is relayed onto the area array detector.

[0007] The bandpass filter is used to filter out stray light outside the working spectrum and improve the signal-to-noise ratio of the imaging system.

[0008] The phase modulation module is used to load a specific phase distribution map and perform phase modulation on the light field (including but not limited to a transmissive spatial light modulator, a reflective spatial light modulator, and a customized photolithographic phase plate, etc.). When the phase modulator is a spatial light modulator, the phase modulation module should also include a polarizer.

[0009] A wideband super-Rayleigh speckle correlation imaging spectroscopic camera based on dispersion compensation includes components such as a front imaging module, a bandpass filter, a phase modulation module, a relay imaging module, an area array detector, and a computer. The signal light from the object sequentially passes through the front imaging module, imaging the object at different wavelengths onto the corresponding first imaging plane. Then, the light passes through the bandpass filter and illuminates the phase modulation module. If the phase modulation module is a reflective spatial light modulator, the light returns along its original path, is reflected by a beam splitter, and then imaged onto the area array detector by the rear imaging system, where it is collected.

[0010] For the front-mounted compensation scheme: design the structure and materials of the front-mounted imaging module to achieve the optimal focal length for front-mounted imaging. The following conditions must be met:

[0011]

[0012] in, The distance from the imaging target to the front imaging module. This is the distance between the front imaging module and the phase modulation module, i.e., the distance from which the front imaging module projects an image of an object with wavelength λ onto the front of the phase modulation module. Location. The distance between them. satisfy

[0013]

[0014] and This refers to the backpropagation wavelength and distance when obtaining the phase distribution map required by the phase modulation module for super Rayleigh speckle using the backpropagation method. (Distance-phase modulation module) The speckle pattern at the location is relayed by the imaging module (focal length is...). When the image is projected onto the area array detector, it satisfies the following imaging formula.

[0015]

[0016] This represents the distance from the phase modulation module to the relay imaging module. This is the distance from the relay imaging module to the area array detector, where the focal length of the relay module is... It is a constant.

[0017] Or the focal length of the relay imaging module. The following conditions must be met:

[0018]

[0019] in, This represents the distance from the phase modulation module to the relay imaging module. The distance is the distance from the relay imaging module to the area array detector, where the distance is... satisfy

[0020]

[0021] in and This refers to the backpropagation wavelength and distance when obtaining the phase distribution map required by the phase modulation module for super Rayleigh speckle using the backpropagation method. The distance... Satisfy the following imaging formula

[0022]

[0023] The distance from the imaging target to the front imaging module. The distance between the front imaging module and the phase modulation module is the focal length of the front module at this point. It is a constant.

[0024] The specific imaging method is shown in the following steps:

[0025] Step 1: Obtain the phase distribution map required for super Rayleigh speckle using phase retrieval or by reverse propagation of the light field at wavelength. and distance The phase distribution map of the corresponding field is obtained by inverse propagation of the super Rayleigh speckle pattern, and then loaded onto the phase modulator;

[0026] Step Two: Calibration Process. The measurement matrix A of the dispersion-compensated super-Rayleigh modulation correlation imaging spectral camera is pre-calibrated using the patented method "Method for Obtaining Measurement Matrix of Compressed Spectral Imaging System" (Patent No.: ZL201410161282.3) and stored on the computer. At this point, the area array detector will obtain a series of dispersion-compensated super-Rayleigh speckle fields, all with a large speckle contrast within the working spectral band.

[0027] Step 3: Detection process. Place the object to be tested within the system's field of view, expose the area array detector once, obtain the corresponding detection light signal Y, and store it on the computer.

[0028] Step 4: Reconstruction process. Based on the calibrated measurement matrix A and the probe light signal Y, the multispectral reconstructed image of the target is obtained through image restoration algorithms or deep learning networks.

[0029] Compared with the prior art, the technical effects of the present invention are as follows: Unlike the prior art which is only designed for single-wavelength speckle, the present invention utilizes the dispersion characteristics compensation of the front imaging module or the relay imaging module to achieve super Rayleigh speckle modulation in a wide band, and applies it to the correlated imaging spectral camera, which can give full play to the noise resistance of super Rayleigh speckle and significantly improve the quality of reconstructed images at low signal-to-noise ratios in the working full spectrum. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the wideband super Rayleigh correlation imaging spectral camera based on dispersion compensation according to the present invention (the phase modulation module is a photolithographic phase plate).

[0031] In the diagram: 1-Front-end imaging module; 2-Bandpass filter; 3-Photolithography phase plate; 4-Relay imaging module; 5-Area array detector; 6-Computer.

[0032] Figure 2 This is a schematic diagram of the second embodiment where the phase modulation module is a transmissive spatial light modulator.

[0033] Figure 3 This is a schematic diagram of the third embodiment where the phase modulation module is a reflective spatial light modulator. Detailed Implementation

[0034] The following description, in conjunction with the accompanying drawings and embodiments, further illustrates the wideband super Rayleigh correlation imaging spectral camera based on dispersion compensation of the present invention, but this should not be construed as limiting the scope of protection of the present invention.

[0035] Example 1: The phase modulation module is a photolithographic phase plate.

[0036] like Figure 1As shown, the system includes a front imaging module 1, a bandpass filter 2, a photolithographic phase plate 3, a relay imaging module 4, an area array detector 5, and a computer 6. Along the incident beam, the front imaging module 1 is positioned sequentially. The light then passes through the bandpass filter 2 and illuminates the photolithographic phase plate 3. The light is then imaged onto the area array detector 5 via the relay imaging system 4 and collected by the detector.

[0037] Example 2: The phase modulation module is a transmissive spatial light modulator.

[0038] like Figure 2 As shown, the system includes a front imaging module 1, a bandpass filter 2, a polarizer 3, a transmissive spatial light modulator 4, a relay imaging module 5, an area array detector 6, and a computer 7. Along the incident beam, the front imaging module 1 is positioned sequentially. The light then passes through the bandpass filter 2 and the polarizer 3 before illuminating the transmissive spatial light modulator 4. The light is then imaged onto the area array detector 6 via the relay imaging system 5 and collected by the detector.

[0039] Example 3: The phase modulation module is a reflective spatial light modulator.

[0040] like Figure 3 As shown, the system includes a front imaging module 1, a bandpass filter 2, a polarizer 3, a beam splitter 4, a reflective spatial light modulator 5, a relay imaging module 6, an area array detector 7, and a computer 8. Along the incident beam, the front imaging module 1 is positioned sequentially. The light then passes through the bandpass filter 2, polarizer 3, and beam splitter 4 before illuminating the reflective spatial light modulator 5. After being modulated by the reflective spatial light modulator 5, the light returns along the same path, is reflected again by the beam splitter 4, and is then imaged onto the area array detector 7 by the relay imaging system 6, where it is collected by the detector.

[0041] The imaging method of this invention based on a dispersion-compensated broadband super Rayleigh correlation imaging spectral camera comprises the following steps:

[0042] Step 1: Phase loading. The phase distribution required for the super Rayleigh light field is obtained by using phase recovery or by using the reverse propagation method to obtain the phase distribution map of the corresponding field by reverse propagation of the super Rayleigh speckle. Then, it is loaded onto the corresponding phase modulator, or the corresponding phase plate is processed by photolithography.

[0043] Step Two: Calibration Process. The measurement matrix A of the dispersion-compensated super-Rayleigh modulation correlation imaging spectral camera is pre-calibrated using the patented method "Method for Obtaining Measurement Matrix of Compressed Spectral Imaging System" (Patent No.: ZL201410161282.3) and stored on the computer. At this point, the area array detector will obtain a series of dispersion-compensated super-Rayleigh speckle fields, all with a large speckle contrast within the working spectral band.

[0044] Step 3: Detection process. Place the object to be tested within the system's field of view, expose the area array detector once, obtain the corresponding detection light signal Y, and store it on the computer.

[0045] Step 4: Reconstruction process. Based on the calibrated measurement matrix A and the probe light signal Y, the multispectral reconstructed image of the target is obtained through image restoration algorithms or deep learning networks.

[0046] In summary, this invention is a wideband super Rayleigh speckle correlation imaging spectrophotometer based on dispersion compensation. It utilizes the dispersion characteristics of the front imaging module or the relay imaging module to generate a super Rayleigh speckle field over a wide band. Applying this method to the correlation imaging spectrophotometer enables the acquisition of high-quality reconstructed images under low signal-to-noise ratio conditions.

Claims

1. A wideband ultra-Rayleigh speckle correlation imaging spectral camera based on dispersion compensation, comprising a front imaging module (1), a bandpass filter (2), a phase modulation module (3), a relay imaging module (4), an area array detector (5), and a computer (6), characterized in that, The phase modulation module (3) is used to load and generate the phase distribution map of super Rayleigh speckle and perform phase modulation on the light field. The front imaging module (1) or the relay imaging module (4) uses imaging relationship compensation to realize super Rayleigh speckle modulation in a wide band. The focal length of the front imaging module (1) The following conditions must be met: in, The distance from the imaging target (a) to the front imaging module, The distance between the front imaging module (1) and the phase modulation module (3) is the distance between the front imaging module (1) and the phase modulation module (3), i.e., the distance between the front imaging module (1) and the phase modulation module (3) where the front imaging module (1) projects the image of the object with wavelength λ onto the front of the phase modulation module (3). Location, where the distance satisfy and The inverse propagation wavelength and distance are used to obtain the phase distribution map required by the phase modulation module (3) for super Rayleigh speckle using the inverse propagation method. The speckle pattern at the location is transmitted via relay imaging module (4), with a focal length of [missing information]. The image is projected onto the area array detector (5), satisfying the following imaging formula: The distance from the phase modulation module (3) to the relay imaging module (4) is... The distance from the relay imaging module (4) to the area array detector (5) is the focal length of the relay imaging module (4). It is a constant; Or the focal length of the relay imaging module (4) The following conditions must be met: in, The distance from the phase modulation module (3) to the relay imaging module (4) is... The distance from the relay imaging module (4) to the array detector (5) is where the distance is... satisfy in and The reverse propagation wavelength and distance are used to obtain the phase distribution map required by the phase modulation module (3) for super Rayleigh speckle using the reverse propagation method, where the distance is... The following imaging formula is satisfied: The distance from the imaging target (a) to the front imaging module (1) is... The distance between the front imaging module (1) and the phase modulation module (3) is the focal length of the front imaging module (1) at this time. It is a constant.

2. The wideband super Rayleigh speckle correlation imaging spectroscopic camera based on dispersion compensation according to claim 1, characterized in that, The bandpass filter (2) is used to filter out stray light outside the working spectrum and improve the signal-to-noise ratio of the imaging system.

3. The wideband super Rayleigh speckle correlation imaging spectroscopic camera based on dispersion compensation according to claim 1, characterized in that, The phase modulation module (3) includes a photolithographic phase plate or a modulation module containing a polarizer and a transmissive spatial light modulator or a reflective spatial light modulator.

4. A method for spectral imaging using a wideband super Rayleigh modulation correlation imaging spectrophotometer based on dispersion compensation as described in any one of claims 1-3, characterized in that... Includes the following steps: Step 1: Obtain the phase distribution map required for super Rayleigh speckle using phase retrieval or by reverse propagation of the light field at wavelength. and distance The phase distribution map of the corresponding field is obtained by inverse propagation of the super Rayleigh speckle pattern, and then loaded onto the phase modulator; Step 2: Calibration process: Pre-calibrate the measurement matrix A and store it on the computer (6). At this time, the area array detector (5) will obtain a series of ultra-Rayleigh speckle fields after applying dispersion compensation, which have a large speckle contrast in the working spectrum. Step 3: Detection process: Place the object to be tested within the system's field of view, expose the area array detector once, obtain the corresponding detection light signal Y, and store it on the computer; Step 4: Reconstruction process: Based on the calibrated measurement matrix A and the probe light signal Y, the multispectral reconstructed image of the target is obtained.

Images