Device and method for realizing spatial wavefront imaging speed improvement by single-pixel off-axis detection

Abstract

The present application belongs to the cross field of spatial wave front measurement and single-pixel imaging. At present, most of the single-pixel wave front imaging based on interference measurement is realized based on phase shift technology, which has defects such as complexity, poor stability, loss of imaging resolution and slow imaging speed. The present application provides a device and method for improving the speed of spatial wave front imaging by using phased array common-path off-axis interference single-pixel detection, which uses the programmable control characteristics of phased array to design the corresponding modulation mode to realize single-pixel common-path off-axis interference, greatly improving the speed of single-pixel wave front imaging, and according to the needs of the imaging scene, whether to choose the largest imaging field of view or higher imaging resolution, different reference strategies can be flexibly selected. The device of the present application is simple, stable, and the wave front imaging speed is significantly improved. The present application is also suitable for wider wave band wave front measurement. It has broad application prospects in the fields of biomedical imaging, lens measurement, single-photon imaging and real-time imaging.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of space wavefront measurement and single-pixel imaging, and specifically relates to a device and method for improving the speed of space wavefront imaging through single-pixel off-axis detection. Background Technology

[0002] Single-pixel imaging is an emerging computational imaging technology with advantages such as high detection sensitivity, wide spectral responsivity, and precise temporal resolution. When single-pixel imaging is combined with interferometry, spatial wavefront information can be retrieved using a single-pixel detector, enabling wavefront complex amplitude measurement. Thanks to the advantages of single-pixel imaging, single-pixel complex amplitude measurement can be extended to wavefront measurements across wider spectral bands, such as infrared imaging, terahertz imaging, and X-ray imaging, finding wide applicability in fields such as biomedical microscopy, single-photon imaging, real-time imaging, and lens measurement imaging. Currently, there are two methods for implementing single-pixel wavefront imaging based on interferometry. One method introduces an additional reference light to interfere with the signal light in the system, which increases the complexity of the system and has poor anti-interference capabilities; the other method introduces an inherent reference field through a reference strategy to achieve common-path interference. Both of these methods are mostly based on traditional phase-shifting techniques, requiring multiple measurements, and their slow measurement speed limits the practical application of single-pixel wavefront measurement. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to disclose a device and method for improving the speed of spatial wavefront imaging through single-pixel off-axis detection. This method utilizes the programmable phase control characteristics of an optical phased array to achieve a faster spatial wavefront imaging speed. Compared with existing methods using phase-shifting technology for spatial wavefront imaging, this invention saves several times the measurement time while maintaining similar imaging quality. It is suitable for applications such as biological imaging, lens measurement, and rapid imaging.

[0004] To achieve the above objectives, the method of the present invention is implemented through the following technical solution:

[0005] A device for improving the speed of spatial wavefront imaging using phased array co-path off-axis interferometry single-pixel detection includes a 4-f system, a phased array, a focusing lens, a pinhole, and a detector, wherein:

[0006] The 4-f system is coaxial with the phased array. The 4-f system includes a first lens and a second lens, and the phased array is located at the horizontal focal length of the second lens. The focusing lens, pinhole, and detector are arranged coaxially from near to far along the phased array's working surface at a 12° angle.

[0007] Furthermore, the phased array is a reflective phased array, which includes a tilted phase grating, a reference mode pattern, and a modulation base mode.

[0008] Furthermore, the aperture r of the pinhole satisfies the relationship r≤1.27λf / d with the wavelength and diameter of the incident beam from the focusing lens and the focal length of the focusing lens, where λ is the wavelength of the beam, f is the focal length of the focusing lens, and d is the diameter of the beam.

[0009] A method for improving the speed of spatial wavefront imaging using phased array co-path off-axis interferometric single-pixel detection is disclosed. Based on the aforementioned device for improving the speed of spatial wavefront imaging using phased array co-path off-axis interferometric single-pixel detection, this method utilizes the real-time programmable control characteristics of the phase distribution of an optical phased array and employs co-path off-axis interferometric single-pixel detection to improve the speed of spatial wavefront imaging. The specific steps are as follows:

[0010] Step 1: Construct a device to improve the speed of spatial wavefront imaging by phased array common off-axis interferometry single-pixel detection; introduce the target spatial wavefront into the phased array working surface through a 4-f system with vertical illumination, set the initial phase distribution of the phased array to a no-modulation mode, and determine the size of the pinhole diameter r based on the size of the emitted beam from the phased array working surface and the focal length of the focusing lens.

[0011] Step 2: Determine the modulation mode to be applied to the phased array: The tilted phase grating in the phased array is used to introduce an off-axis angle between the signal beam and the reference beam, generating a fixed phase difference; the incident wavefront is partitioned using the reference mode pattern in the phased array, dividing the incident wavefront into a reference part and a signal part; the modulation base mode is used to spatially sample the introduced wavefront in the signal part; then the unmodulated wavefront and the modulated wavefront reflected from the phased array undergo common off-axis interference after being focused by the focusing lens;

[0012] Step 3: Configure the initial parameters of the device for improving the speed of spatial wavefront imaging by phased array common off-axis interferometry single pixel detection: spatial wavefront imaging resolution M×N, single pixel imaging sampling rate φ, number of mirrors used in the phased array and determination of the imaging field of view size. It is also necessary to configure the number of cycles of the tilted phase grating, that is, the off-axis angle θ of the signal light relative to the reference light.

[0013] Step 4: Load modulation modes onto the phased array. The detector collects the signal intensity after focusing by the focusing lens. The φ×M×N modulation modes generated by single-pixel imaging are sequentially loaded onto the phased array. At the same time, the detector collects the signal intensity value of the center point of the Fourier plane corresponding to each modulation mode.

[0014] Step 5: Reconstruct the off-axis hologram of the imaged target: Based on the interference signal intensity value of the Fourier plane center point corresponding to each modulation mode collected by the single-pixel detector, the off-axis hologram of the target is finally reconstructed using the single-pixel reconstruction algorithm.

[0015] Step 6: Reconstruct the target spatial wavefront: Based on the reconstructed off-axis hologram, the spatial wavefront of the target object is recovered by Fourier fringe analysis to obtain the amplitude and phase of the target spatial wavefront.

[0016] Furthermore, the modulation basis modes in step 2 include: Hadamard transform basis modes, discrete cosine transform basis modes, and Fourier transform basis modes.

[0017] Furthermore, the phased array type in step 2 is: pure phase liquid crystal spatial light modulator, digital micromirror device, ferroelectric liquid crystal spatial light modulator, amplitude liquid crystal spatial light modulator indirectly realizes pure phase modulator or metasurface through Lee method or superpixel method.

[0018] Furthermore, the reference pattern in step 2 includes: a checkerboard reference pattern, an external reference pattern, and a random reference pattern.

[0019] In summary, the invention has the following beneficial effects:

[0020] This invention fully utilizes the real-time programmable control characteristics of the phase distribution of optical phased arrays. In a device for improving the speed of spatial wavefront imaging through common-path off-axis interferometric single-pixel detection, it employs a method to increase the speed of spatial wavefront imaging, offering the following advantages:

[0021] 1. Compared to traditional phase-shifting interferometry, it achieves similar imaging quality while saving several times the measurement time. It is suitable for applications in biomedical imaging, lens measurement, broadband wavefront complex amplitude measurement, and real-time imaging.

[0022] 2. The structure is simple and the method is flexible, allowing for the selection of different reference patterns according to imaging requirements;

[0023] 3. It can realize spatial wavefront imaging using single-pixel imaging of most existing different modulation base modes. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the device structure of the present invention;

[0025] Figure 2 A tilted phase grating with an off-axis angle is introduced between the signal beam and the reference beam for loading onto the phased array;

[0026] Figure 3 The different reference patterns, from left to right, are the "checkerboard" reference pattern, the external reference pattern, and the random reference pattern;

[0027] Figure 4A simulated amplitude and phase distribution diagram of a target space wavefront;

[0028] Figure 5 To achieve the imaging results of the simulated target space wavefront, from left to right, are the off-axis hologram of the simulated target space wavefront, the spectrum of the off-axis hologram, and the amplitude and phase distribution of the target space wavefront reconstructed using Fourier fringe analysis.

[0029] Figure 6 This is a phase distribution diagram of a simulated ideal lens;

[0030] Figure 7 To achieve the results of the lens measurement, from left to right are the off-axis hologram of the lens, the spectrum of the off-axis hologram, and the measured phase distribution of the lens.

[0031] In the diagram, 1 is the first lens, 2 is the second lens, 3 is the phased array, 4 is the focusing lens, 5 is the pinhole camera, and 6 is the detector. Detailed Implementation Plan

[0032] The present invention will now be described in further detail with reference to the accompanying drawings.

[0033] It should be noted that, for ease of description, the descriptions of direction in the following text are consistent with the directions in the accompanying drawings, but this does not limit the scope of the invention.

[0034] like Figures 1-7 As shown, this invention discloses a device for improving the speed of spatial wavefront imaging based on phased array co-path off-axis interferometry single-pixel detection. The device includes a 4-f system, a phased array 3, a focusing lens 4, a pinhole 5, and a detector 6. The 4-f system is coaxial with the phased array 3. The 4-f system includes a first lens 1 and a second lens 2. The phased array 3 is located at the horizontal focal length of the second lens 2. The phased array 3 is a reflective phased array, which includes a tilted phase grating, a reference mode pattern, and a modulation base pattern. The focusing lens 4, pinhole 5, and detector 6 are arranged coaxially from near to far along the working surface of the phased array 3 at a 12° tilt.

[0035] This invention fully utilizes the real-time programmable control characteristics of the phase distribution of optical phased arrays. In a device for improving the speed of spatial wavefront imaging through common-path off-axis interferometry single-pixel detection, it employs a method to enhance the spatial wavefront imaging speed. Compared to traditional phase-shifting interferometry, it achieves similar imaging quality while saving several times the measurement time. The structure is simple, the method is flexible, and different reference patterns can be flexibly selected according to imaging requirements. It can realize single-pixel imaging of most existing modulation base modes for spatial wavefront imaging. It is suitable for applications in biomedical imaging, lens measurement, broadband wavefront complex amplitude measurement, and real-time imaging.

[0036] Phased array 3 is used to carry the designed phase distribution. The modulation modes loaded on phased array 3 include a tilted phase grating, a reference mode pattern, and a corresponding modulation base mode. The tilted phase grating is used to introduce a small off-axis angle between the signal beam and the reference beam, generating a fixed phase difference. The reference mode pattern is used to partition the input wavefront and cause off-axis interference. The modulation base mode is used to spatially sample the introduced wavefront in the signal beam portion. The polarization direction is either horizontal or vertical polarization; here, the polarization direction refers to the inherent polarization direction of phased array 3 itself.

[0037] The size of the pinhole 5 is related to the wavelength and diameter of the beam from the focusing lens 4 and the focal length of the focusing lens 4, which satisfies the relationship r ≤ 1.27λf / d, where λ is the wavelength of the beam, f is the focal length of the focusing lens 4, and d is the diameter of the beam.

[0038] This invention also discloses a method for improving the speed of spatial wavefront imaging using phased array co-path off-axis interferometric single-pixel detection. Based on the aforementioned device for improving the speed of spatial wavefront imaging using phased array co-path off-axis interferometric single-pixel detection, the method is characterized by utilizing the real-time programmable control characteristics of the phase distribution of an optical phased array, and employing co-path off-axis interferometric single-pixel detection to improve the speed of spatial wavefront imaging. The specific steps are as follows:

[0039] Step 1: Construct a device to improve the speed of spatial wavefront imaging through phased array common-path off-axis interferometry single-pixel detection. The target spatial wavefront is vertically irradiated into the working surface of phased array 3 through a 4-f system. The initial phase distribution of phased array 3 is set to a no-modulation mode. The aperture r of pinhole 5 is determined based on the size of the emitted beam from the working surface of phased array 3 and the focal length of focusing lens 4.

[0040] Step 2: Determine the modulation mode to be applied to phased array 3: The modulation mode applied to phased array 3 includes a tilted phase grating, a reference mode pattern, and a corresponding modulation base mode. The tilted phase grating introduces an off-axis angle between the signal beam and the reference beam, generating a fixed phase difference. The off-axis angle can be adjusted according to the actual imaging scene and device parameters, and is generally selected from 0 to 2°. The reference mode pattern is used to partition the incident wavefront, dividing it into a reference light portion and a signal light portion. Reference mode patterns include: checkerboard reference mode pattern, external reference mode pattern, and random reference mode pattern. The modulation base mode is used to spatially sample the introduced wavefront in the signal light portion. Then, the unmodulated wavefront and the modulated wavefront reflected from phased array 3 undergo common-path off-axis interference after being focused by lens 4.

[0041] Step 3: Configure the initial parameters of the device: spatial wavefront imaging resolution M×N, single-pixel imaging sampling rate φ, number of mirrors used in the phased array and determine the imaging field of view size. It is also necessary to configure the number of cycles of the tilted phase grating, that is, the off-axis angle θ of the signal light relative to the reference light.

[0042] Step 4: Load modulation modes onto phased array 3. Detector 6 acquires the signal intensity after focusing by focusing lens 4. Since the reference beam and signal beam have already undergone off-axis interference, the signal at this time is equivalent to another beam of light distinct from both the signal beam and the reference beam. The φ×M×N modulation modes generated by single-pixel imaging are sequentially loaded onto phased array 3, and detector 6 simultaneously acquires the signal intensity value at the center point of the Fourier plane corresponding to each modulation mode.

[0043] Step 5: Reconstruct the off-axis hologram of the imaged target: Based on the interference signal intensity value of the Fourier plane center point corresponding to each modulation mode collected by the single-pixel detector, the off-axis hologram of the target is finally reconstructed using the single-pixel reconstruction algorithm.

[0044] Step 6: Reconstruct the target spatial wavefront. Based on the reconstructed off-axis hologram, the spatial wavefront of the target object can be recovered using Fourier fringe analysis, and the amplitude and phase of the target spatial wavefront can be obtained.

[0045] Commonly used optical phased array types include pure phase liquid crystal spatial light modulators, digital micromirror devices, ferroelectric liquid crystal spatial light modulators, and amplitude liquid crystal spatial light modulators. Pure phase modulators or metasurfaces are indirectly realized through Lee's method or superpixel method.

[0046] Example 1: In this example, we take one of the commonly used reflective optical phased arrays, the digital micromirror device, as an example. The method of improving the speed of spatial wavefront imaging by common-path off-axis interference single-pixel detection of digital micromirror devices is used in wavefront imaging in weak light and special bands. In this example, phased array 3 is a digital micromirror device.

[0047] Example 2: In this example, the Hadamard modulator, one of the commonly used single-pixel imaging modulation base modes, is used as an example. The method of improving the spatial wavefront imaging speed by common-path off-axis interferometric single-pixel detection is applied to digital micromirror devices with binary modulation base modes. In this example, the modulation base mode is the Hadamard transform base mode.

[0048] Example 3: Commonly used reference patterns include checkerboard reference patterns, external reference patterns, and random reference patterns. This example uses the commonly used checkerboard reference pattern as an example. In this example, the reference pattern is a checkerboard reference pattern, such as... Figure 3 As shown.

[0049] Example 4: This example uses imaging of a spatial wavefront with an amplitude confined within a circular ring and bearing the letter "D," and a phase distribution resembling a "rabbit." Figure 4 As shown, this embodiment performs wavefront imaging on the combined wavefront according to the steps of the method of the present invention. The off-axis hologram and its spectrum of the wavefront are reconstructed using second-order correlation. Finally, the amplitude and phase distribution of the wavefront are reconstructed using Fourier fringe analysis. Figure 5 As shown.

[0050] Example 5: This example uses the phase measurement of a physical optical lens with a focal length of 1000mm as an example. The phase measurement of this optical lens is restricted to a circular area, such as... Figure 6 The diagram illustrates an ideal phase representation of a physical lens. This embodiment is an example of its application in the field of lens measurement. First, the target spatial wavefront needs to be introduced into the working surface of the phased array using a 4-f system. Then, lens measurements are performed according to the steps of this invention. The off-axis hologram and its spectrum of the lens are reconstructed using a second-order correlation algorithm. Finally, the phase distribution of the lens is reconstructed using Fourier fringe analysis, as shown below. Figure 7 As shown.

[0051] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A device for improving the speed of spatial wavefront imaging using phased array co-path off-axis interferometry single-pixel detection, characterized in that, The speed of spatial wavefront imaging is improved by utilizing the programmable phase control characteristics of optical phased arrays. The system includes a 4-f system, a phased array (3), a focusing lens (4), a pinhole (5), and a detector (6), wherein: The 4-f system is coaxial with the phased array (3). The 4-f system includes a first lens (1) and a second lens (2). The phased array (3) is located at the horizontal focal length of the second lens (2). The focusing lens (4), pinhole (5) and detector (6) are arranged coaxially from near to far along the working surface of the phased array (3) at an angle of 12°. The phased array (3) is a reflective phased array, which includes a tilted phase grating, a reference mode pattern and a modulation base mode.

2. The device for improving the speed of spatial wavefront imaging using phased array co-path off-axis interferometry single-pixel detection according to claim 1, characterized in that, The aperture r of the pinhole (5) satisfies the relationship between the wavelength and diameter of the incident beam from the focusing lens (4) and the focal length of the focusing lens (4). ,in Where is the wavelength of the light beam. The focal length of the focusing lens (4) is... Let be the diameter of the beam.

3. A method for improving the speed of spatial wavefront imaging using phased array co-path off-axis interferometry single-pixel detection, based on the apparatus for improving the speed of spatial wavefront imaging using phased array co-path off-axis interferometry single-pixel detection as described in any one of claims 1 to 2, characterized in that, By leveraging the real-time programmable control characteristics of the phase distribution of optical phased arrays, a faster spatial wavefront imaging speed is achieved using common-path off-axis interferometric single-pixel detection. The specific steps are as follows: Step 1: Construct a device to realize the speed improvement of spatial wavefront imaging by phased array common off-axis interference single pixel detection; introduce the target spatial wavefront into the phased array (3) working surface through the 4-f system vertical illumination, set the initial phase distribution of the phased array (3) to the no-modulation mode, and determine the size of the pinhole (5) aperture r according to the size of the emitted beam of the phased array (3) working surface and the focal length of the focusing lens (4); Step 2: Determine the modulation mode to be loaded in the phased array (3): The tilted phase grating in the phased array (3) is used to introduce an off-axis angle between the signal beam and the reference beam to generate a fixed phase difference; the incident wavefront is partitioned using the reference mode pattern in the phased array (3) to divide the incident wavefront into a reference part and a signal part, and the modulation base mode is used to spatially sample the introduced wavefront in the signal part; Then, the unmodulated wavefront and the modulated wavefront reflected from the phased array (3) are focused by the focusing lens (4) and then undergo common off-axis interference. Step 3: Configure the initial parameters of the device for improving the speed of space wavefront imaging using phased array co-path off-axis interferometry single-pixel detection: space wavefront imaging resolution M×N, single-pixel imaging sampling rate The number of mirrors used in the phased array and the size of the imaging field of view also require the configuration of the number of periods of the tilted phase grating, which is the off-axis angle of the signal light relative to the reference light. ; Step 4: Load modulation modes into the phased array (3), and the detector (6) collects the signal intensity after focusing by the focusing lens (4). The φ×M×N modulation modes generated by single-pixel imaging are sequentially loaded into the phased array (3). At the same time, the detector (6) collects the signal intensity value of the center point of the Fourier plane corresponding to each modulation mode. Step 5: Reconstruct the off-axis hologram of the imaged target: Based on the interference signal intensity value of the Fourier plane center point corresponding to each modulation mode collected by the single-pixel detector, the off-axis hologram of the target is finally reconstructed using the single-pixel reconstruction algorithm. Step 6: Reconstruct the target spatial wavefront: Based on the reconstructed off-axis hologram, the spatial wavefront of the target object is recovered by Fourier fringe analysis to obtain the amplitude and phase of the target spatial wavefront.

4. The method for improving the speed of spatial wavefront imaging using phased array co-path off-axis interferometry single-pixel detection according to claim 3, characterized in that: The modulation base modes in step 2 include: Hadamard transform base mode, discrete cosine transform base mode, and Fourier transform base mode.

5. The method for improving the speed of spatial wavefront imaging using phased array co-path off-axis interferometry single-pixel detection according to claim 3, characterized in that: The phase array type in step 2 is: pure phase liquid crystal spatial light modulator, digital micromirror device, ferroelectric liquid crystal spatial light modulator, amplitude liquid crystal spatial light modulator indirectly realized as pure phase modulator or metasurface through Lee method or superpixel method.

6. The method for improving the speed of spatial wavefront imaging using phased array co-path off-axis interferometry single-pixel detection according to claim 3, characterized in that: The reference pattern in step 2 includes: checkerboard reference pattern, external reference pattern, and random reference pattern.

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