A few-pixel wavefront imaging device and method based on location sensitive detection

Abstract

The present application relates to the field of wavefront sensing and computational imaging, and the wavefront imaging technology based on spatial sampling relies on a large number of spatial sampling modes, and the number of sampling modes increases exponentially with the increase of spatial resolution, the present application provides a kind of few-pixel wavefront imaging device and method based on position sensitive detection, it is in turn for 4f lens group and spatial light modulator along the transmission direction of target spatial wavefront to be measured, lens array is arranged between spatial light modulator and position sensitive few-pixel detector, each detection unit of position sensitive few-pixel detector independently captures the light intensity and centroid position information of corresponding focus point, calculates the intensity and phase gradient of each sub-space wavefront, calculates the phase distribution of sub-space wavefront, and synthesizes the complete target spatial wavefront phase distribution, the present application realizes the efficient reconstruction of wavefront through the mapping relationship of spatial position, improves the speed of wavefront sensing and imaging, and can maintain a faster wavefront imaging speed under a wider working waveband or single-photon detection level.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of wavefront sensing and computational imaging, and more specifically, relates to a low-pixel wavefront imaging device and method based on position-sensitive detection. Background Technology

[0002] The surface formed by equiphase surfaces at a certain location where a wave propagates is called a wavefront. Wavefront measurement technology is an optical detection method used to accurately analyze the phase distribution and distortion of light waves. Its core principle is to capture the wavefront tilt or phase difference through a sensor, and then reconstruct the wavefront morphology. Currently, the mainstream wavefront measurement techniques are divided into interferometric and non-interferometric methods. Interferometric methods calculate the target wavefront by measuring the interference hologram generated by the introduction of a reference light. Due to the introduction of the reference light, this type of method has weak resistance to environmental disturbances. Therefore, non-interferometric methods such as coherent diffraction technology and phase-solving methods based on the transmission equation have emerged. Among them, Shak-Hartmann wavefront sensing technology has been gradually developed due to its advantages of non-iterative, non-interferometric, and high robustness. It combines a microlens array and an array detector. By placing the detector at the focal plane of the microlens array, the offset of the centroid of the focal point corresponding to each microlens can be captured. The wavefront can be calculated by using the relationship between the centroid offset and the wavefront phase gradient. However, the imaging resolution and dynamic response range of this technology are severely limited by the number, focal length, and size of the microlens array. Subsequently, to overcome the aforementioned problems, researchers developed wavefront imaging technology based on spatial sampling. The core of this technology is to sample the wavefront using a series of spatial sampling patterns. The intensity and centroid information of the focal points corresponding to different sampling patterns are recorded by a position-sensitive sensor. Finally, a reconstruction algorithm similar to single-pixel imaging can be used to reconstruct the amplitude and phase of the wavefront. However, this type of method relies on a large number of spatial sampling patterns, significantly slowing down wavefront acquisition. Furthermore, the number of sampling patterns increases exponentially with increasing spatial resolution. This is highly unsuitable for applications requiring real-time capture of dynamic wavefront information. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention aims to provide a position-sensitive detection-based low-pixel wavefront imaging device and method. By utilizing a position-sensitive low-pixel detector for spatial wavefront sampling to achieve wavefront sensing and imaging, it can efficiently and quickly acquire spatial wavefront information. This overcomes the inherent imaging resolution limitations of Shak-Hartmann wavefront sensing while significantly improving the speed of spatial sampling wavefront imaging, making it suitable for real-time imaging scenarios.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: A position-sensitive detection-based few-pixel wavefront imaging device includes a 4f lens group, a spatial light modulator, a lens array, and a position-sensitive few-pixel detector. The 4f lens group and the spatial light modulator are arranged sequentially along the spatial wavefront transmission direction of the target. A lens array is set between the spatial light modulator and the position-sensitive few-pixel detector used to receive the modulated beam. The spatial light modulator is divided into n×n subspaces. The number of detection units of the position-sensitive few-pixel detector is n×n. Each detection unit of the position-sensitive few-pixel detector independently captures the light intensity and centroid position information of the corresponding focal point.

[0005] Furthermore, the spatial light modulator is set to a spatial sampling mode. The spatial light modulator performs sub-spatial wavefront division and spatial wavefront sampling on the target spatial wavefront. The spatial light modulator can be any one of a liquid crystal spatial light modulator or a digital micromirror device.

[0006] Furthermore, the spatial sampling mode performs spatial sampling on each wavefront, and the spatial sampling mode can be any one of the following: Hadamard mode, Fourier mode, discrete cosine mode, or cyclic Hadamard mode.

[0007] A position-sensitive detection-based few-pixel wavefront imaging method, implemented using the aforementioned position-sensitive detection-based few-pixel wavefront imaging device, specifically includes the following steps: Step 1. Build a wavefront sensing device based on position-sensitive few-pixel detection, select the spatial sampling mode of the spatial light modulator, the imaging resolution of the spatial wavefront of the target to be measured is M×N, and the number of detection units of the position-sensitive few-pixel detector is n×n. Step 2. Spatial segmentation and sampling of the target spatial wavefront: The target spatial wavefront to be measured is divided into n×n independent sub-spatial wavefronts using a spatial light modulator. The spatial sampling mode is composed of multiple sub-sampling modes, and each sub-sampling mode samples the corresponding sub-wavefront. Step 3. After sampling, each subspace wavefront passes through the sublenses of the lens array to form a focal array at the focal point. The intensity and centroid position information of the focal point corresponding to each subspace wavefront are mapped and recorded on the detection unit of the corresponding position sensitive few-pixel detector. Each detection unit only records the light intensity and focal position information of the corresponding subspace wavefront, and the light intensity and focal position information recorded by the detection unit corresponding to each subspace wavefront are collected and output in parallel. Step 4. Reconstructing the image: Based on the Shackleton-Hartmann wavefront reconstruction and single-pixel imaging reconstruction algorithms, the intensity of each subspace wavefront is calculated based on the light intensity signal detected by the detection unit of each position-sensitive few-pixel detector in Step 3, and the complete wavefront intensity distribution is synthesized; the phase gradient of each subwavefront is calculated based on the focal centroid position detected by the detection unit of each position-sensitive few-pixel detector in Step 3, and the phase distribution of the subspace wavefront is calculated by numerical integration, and the complete target space wavefront phase distribution is synthesized.

[0008] Furthermore, the spatial resolution of the spatial coding pattern corresponding to each subspace wavefront is (M / n) × (N / n).

[0009] Furthermore, the single-pixel imaging reconstruction algorithm can be any one of the following: second-order correlation algorithm, inverse transform algorithm, or compressed sensing algorithm.

[0010] Furthermore, the numerical integration algorithm integrates the phase gradient to recover the wavefront phase. The numerical integration algorithm can be any one of the following: linear integration method, Fourier transform integration method, discrete cosine transform integration method, and iterative integration method.

[0011] In summary, the invention has the following beneficial effects: This invention fully combines the advantages of array-based detection and single-pixel detection, achieving a balance between detector and imaging speed. It uses a low-pixel detector instead of a high-density, highly integrated area array detector (CCD / CMOS), avoiding the problems of high cost and difficulty in acquiring area array detectors in special wavelength bands (infrared, ultraviolet, terahertz, etc.). Compared with the micro-unit area array detector, the low-pixel detector of this invention has a larger unit photosensitive area, which can collect more photons, resulting in stronger detection capability and higher detection efficiency under low light (single photon) conditions. By spatially segmenting the wavefront and sampling the subspace, parallel data acquisition is achieved, breaking the speed bottleneck caused by the global scanning mode of traditional spatial sampling Shakhartmann wavefront imaging technology, thus increasing the wavefront imaging speed by several times and making it suitable for high-speed dynamic scenes. This invention has low requirements for detector pixel density, making it possible to use area array detectors that have excellent performance in specific wavebands but are difficult to manufacture with high pixel density, thus expanding the spectral range of wavefront sensing. It combines the speed advantage of parallel detection of area array detectors with the detection advantage of single-pixel detectors in special wavebands or low light conditions, while avoiding the disadvantages of both, and provides a wavefront sensing solution that has both high performance and high feasibility in practical applications. Attached Figure Description

[0012] Figure 1 This is a wavefront sensing device based on a position-sensitive, low-pixel detector.

[0013] Among them, 1, 4f lens group, 2, spatial light modulator, 3, microlens array, and 4, position-sensitive low-pixel detector. Detailed Implementation

[0014] The present invention will now be described in further detail with reference to the accompanying drawings.

[0015] 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 they do not limit the structure of the present invention.

[0016] like Figure 1 As shown, this invention discloses a few-pixel wavefront imaging device based on position-sensitive detection, including a 4f lens group 1, a spatial light modulator 2, a lens array 3, and a position-sensitive few-pixel detector 4. Along the transmission direction of the target spatial wavefront, the 4f lens group 1 and the spatial light modulator 2 are arranged sequentially. The 4f lens group 1 relays and transmits the target wavefront to the surface of the spatial light modulator 2. The spatial light modulator 2 is set to a spatial sampling mode, which performs spatial sampling on each sub-wavefront. The spatial sampling mode can be any one of Hadamard mode, Fourier mode, discrete cosine mode, or cyclic Hadamard mode. The spatial light modulator 2 performs sub-spatial wavefront division and spatial wavefront sampling on the target spatial wavefront. The modulator 2 is either a liquid crystal spatial light modulator or a digital micromirror device. A lens array 3 is set between the spatial light modulator 2 and the position-sensitive few-pixel detector 4 for receiving the modulated light beam. The number of sub-lenses in the lens array 3 is the same as the number of sub-space wavefronts sampled in parallel. Each sub-lens focuses the corresponding sampled sub-space wavefront and forms a focal point array on the focal plane. The spatial light modulator 2 is divided into n×n subspaces. The number of detection units in the position-sensitive few-pixel detector 4 is n×n. Each detection unit of the position-sensitive few-pixel detector 4 independently captures the centroid position information of the light field intensity and intensity distribution of the corresponding focal point. The number of detection units is much less than the number of pixels required for complete imaging.

[0017] This invention also discloses a few-pixel wavefront imaging method based on position-sensitive detection, implemented using the aforementioned few-pixel wavefront imaging device based on position-sensitive detection, characterized by the following steps: Step 1. Construct a wavefront sensing device based on position-sensitive few-pixel detectors. Select the spatial sampling mode of the spatial light modulator 2. The imaging resolution of the target spatial wavefront is M×N, and the number of detection units of the position-sensitive few-pixel detector 4 is n×n. The position-sensitive few-pixel detector 4 records the intensity at the focal point and the centroid position of the focal point.

[0018] Step 2. Spatial segmentation and sampling of the target spatial wavefront: The spatial wavefront to be measured is divided into n×n independent sub-spatial wavefronts using the spatial light modulator 2. The spatial sampling mode is composed of multiple sub-sampling modes, and each sub-sampling mode samples the corresponding sub-wavefront. The spatial sampling mode switched by the spatial light modulator (2) is composed of multiple sub-sampling modes, and the spatial resolution of the spatial coding mode corresponding to each sub-spatial wavefront is (M / n)×(N / n). Finally, the spatial sampling mode loaded on the spatial light modulator 2 is a combination of n×n spatial basis modes, the purpose of which is to perform parallel sampling of the sub-spatial wavefronts.

[0019] Step 3. After sampling, each subspace wavefront passes through the sublenses of lens array 3 to form a focal array at the focal point. The intensity and centroid position information of the focal point corresponding to each subspace wavefront are mapped and recorded on the detection unit of the corresponding position sensitive few-pixel detector 4. Each detection unit only records the light intensity and focal position information of the corresponding subspace wavefront, and the light intensity and focal position information recorded by the detection unit corresponding to each subspace wavefront are collected and output in parallel. Step 4. Reconstructing the image: Based on the Shackleton-Hartmann wavefront reconstruction and single-pixel imaging reconstruction algorithms, the intensity of each subspace wavefront is calculated based on the light intensity signal detected by the detection unit of each position-sensitive few-pixel detector 4 in Step 3, and a complete wavefront intensity distribution is synthesized. The single-pixel imaging reconstruction algorithm can be any one of the second-order correlation algorithm, inverse transform algorithm, or compressed sensing algorithm. The phase gradient of each subwavefront is calculated based on the focal centroid position detected by the detection unit of each position-sensitive few-pixel detector 4 in Step 3, and the phase distribution of the subspace wavefront is calculated by numerical integration method, and a complete target space wavefront phase distribution is synthesized. The numerical integration algorithm integrates the phase gradient to recover the wavefront phase. The numerical integration algorithm can be any one of the linear integration method, Fourier transform integration method, discrete cosine transform integration method, or iterative integration method.

[0020] The 4f lens group 1 is an optical system composed of two lenses with the same focal length or a certain focal length ratio, mainly used for optical information processing and spatial filtering. The wavefront to be measured is conjugate-relayed to the surface of the spatial light modulator 2 after passing through the 4f lens group 1. The spatial light modulator 2 (SLM) is a core device that achieves light wave modulation by actively controlling light field parameters (such as amplitude, phase, polarization state). It consists of a one-dimensional or two-dimensional array of independent pixel units (subspaces). Each unit can independently receive optical or electrical signals and dynamically change its own optical properties (such as refractive index and polarization state). The spatial light modulator can be a liquid crystal spatial light modulator, a digital micromirror device (DMD), etc. The spatial sampling mode is switched on the spatial light modulator 2. The sampled beam is reflected and focused by the lens array 3 onto the position-sensitive few-pixel detector 4. The position-sensitive few-pixel detector is a detector composed of a small number of pixel sensors. Each pixel sensor can simultaneously acquire the intensity and centroid position of the focal point. Each detection unit is specifically used to receive and record the light field intensity and focal point position information from its corresponding subspace.

[0021] Shak-Hartmann wavefront sensing technology utilizes a microlens array and a position-sensitive array detector to acquire the target wavefront. Its imaging resolution and dynamic range are significantly limited by the number, focal length, and size of the microlenses. Subsequent spatial sampling wavefront sensing technology uses a single lens and a series of spatial sampling modes to sample the wavefront, overcoming the inherent limitations of resolution and dynamic range in traditional Shak-Hartmann wavefront sensing. However, relying on a large number of spatial sampling modes significantly increases imaging time, which is often unsuitable for dynamic wavefront scenarios requiring real-time monitoring. This invention utilizes a position-sensitive sensor with a small number of pixels and a spatial light modulator to achieve efficient wavefront reconstruction through spatial position mapping. While retaining the advantages of high dynamic range and high imaging resolution of spatial sampling wavefront sensing technology, it greatly improves the speed of wavefront sensing and imaging. It maintains a fast wavefront imaging speed over a wide operating wavelength range or at single-photon detection levels, making it practically valuable.

[0022] 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 low-pixel wavefront imaging device based on position-sensitive detection, characterized in that, The system includes a 4f lens group (1), a spatial light modulator (2), a lens array (3), and a position-sensitive few-pixel detector (4). The 4f lens group (1) and the spatial light modulator (2) are arranged sequentially along the spatial wavefront transmission direction of the target to be measured. The lens array (3) is set between the spatial light modulator (2) and the position-sensitive few-pixel detector (4) used to receive the modulated beam. The spatial light modulator (2) is divided into n×n subspaces. The number of detection units of the position-sensitive few-pixel detector (4) is n×n. Each detection unit of the position-sensitive few-pixel detector (4) independently captures the light intensity and centroid position information of the corresponding focal point.

2. The few-pixel wavefront imaging device based on position-sensitive detection according to claim 1, characterized in that, The spatial light modulator (2) is set to a spatial sampling mode. The spatial light modulator (2) performs sub-spatial wavefront division and spatial wavefront sampling on the target spatial wavefront. The spatial light modulator (2) can be any one of a liquid crystal spatial light modulator or a digital micromirror device.

3. The few-pixel wavefront imaging device based on position-sensitive detection according to claim 2, characterized in that, The spatial sampling mode performs spatial sampling on each wavefront, and the spatial sampling mode can be any one of the following: Hadamard mode, Fourier mode, discrete cosine mode, and cyclic Hadamard mode.

4. A few-pixel wavefront imaging method based on position-sensitive detection, implemented by the few-pixel wavefront imaging device based on position-sensitive detection as described in any one of claims 1 to 3, characterized in that, Specifically, the following steps are included: Step 1. Build a wavefront sensing device based on position-sensitive low-pixel detection, select the spatial sampling mode of the spatial light modulator (2), the imaging resolution of the spatial wavefront of the target to be measured is M×N, and the number of detection units of the position-sensitive low-pixel detector (4) is n×n. Step 2. Spatial segmentation and sampling of the target spatial wavefront: The target spatial wavefront to be measured is divided into n×n independent sub-spatial wavefronts using a spatial light modulator (2). The spatial sampling mode is composed of multiple sub-sampling modes, and each sub-sampling mode samples the corresponding sub-wavefront. Step 3. After sampling, each subspace wavefront passes through the sublenses of the lens array (3) to form a focal array at the focal point. The intensity and centroid position information of the focal point corresponding to each subspace wavefront are mapped and recorded on the detection unit of the corresponding position sensitive few-pixel detector (4). Each detection unit only records the light intensity and focal position information of the corresponding subspace wavefront, and collects and outputs the light intensity and focal position information recorded by the detection unit corresponding to each subspace wavefront in parallel. Step 4. Reconstructing the image: Based on the Shaker-Hartmann wavefront reconstruction and single-pixel imaging reconstruction algorithm, the intensity of each subspace wavefront is calculated according to the light intensity signal detected by the detection unit of each position-sensitive few-pixel detector (4) in Step 3, and the complete wavefront intensity distribution is synthesized; the phase gradient of each subwavefront is calculated according to the focal centroid position detected by the detection unit of each position-sensitive few-pixel detector (4) in Step 3, and the phase distribution of the subspace wavefront is calculated by numerical integration method, and the complete target space wavefront phase distribution is synthesized.

5. The few-pixel wavefront imaging method based on position-sensitive detection according to claim 4, characterized in that, The spatial resolution of the spatial coding pattern corresponding to each subspace wavefront is (M / n) × (N / n).

6. The few-pixel wavefront imaging method based on position-sensitive detection according to claim 4, characterized in that, The single-pixel imaging reconstruction algorithm can be any one of the following: second-order correlation algorithm, inverse transform algorithm, or compressed sensing algorithm.

7. The few-pixel wavefront imaging method based on position-sensitive detection according to claim 4, characterized in that, The numerical integration algorithm integrates the phase gradient to recover the wavefront phase. The numerical integration algorithm can be any one of the following: linear integration method, Fourier transform integration method, discrete cosine transform integration method, and iterative integration method.

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