Device and method for improving spatial resolution through common-path single-pixel detection based on DMD (Digital Micromirror Device)

Abstract

The invention relates to the crossing field of spatial wavefront measurement and single-pixel imaging. A common-path single-pixel detection spatial resolution improving device based on a DMD (digital micromirror device) comprises a first lens, a second lens, a first digital micromirror device, a third lens, a fourth lens, a second digital micromirror device, a fifth lens, a sixth lens, a first pinhole, a second pinhole, a first detector and a second detector, the third lens and the fourth lens form a second 4-f system, the first digital micro-mirror device is located on a Fourier rear focal plane of the first 4-f system, the second digital micro-mirror device is located on a Fourier rear focal plane of the second 4-f system, the first pinhole is located on a Fourier plane of the fifth lens, the second pinhole is located on a Fourier plane of the sixth lens, and the fourth lens is located on a Fourier plane of the fifth lens. The first detector is used for receiving a light beam signal penetrating through the first pinhole.

Description

Technical Field

[0001] The present invention relates to the cross field of spatial wavefront measurement and single-pixel imaging. Background Art

[0002] Single-pixel imaging is an emerging computational imaging technology, which has advantages such as high detection sensitivity, wide spectral response rate, and precise time resolution. When single-pixel imaging is combined with interferometry, it is possible to retrieve spatial wavefront information through a single-pixel detector to achieve wavefront complex amplitude measurement. Currently, there are mainly two methods for single-pixel wavefront measurement using a digital micromirror device (DMD), namely the dual-path method and the common-path method. The former requires an additional optical path to be introduced for the reference light. This optical setup is relatively complex and has weak anti-interference ability, but the advantage is that the imaging resolution will not be lost. The latter only requires one optical path, and the device complexity is relatively low. However, it often needs to adopt the methods of superpixels and sub-regions on the digital micromirror device (DMD) for interference. Part of it is used as the signal region for modulation, and the other part is used as the reference light for interference. This traditional sub-region common-path interference method often loses a part of the imaging resolution, and the light utilization efficiency will be reduced because only the signal on one side of the digital micromirror device (DMD) is detected. Summary of the Invention

[0003] The purpose of the present invention is to utilize the complementary structural characteristics of signal detection on both sides of the digital micromirror device (DMD) and the characteristics of analog pure-phase high-speed modulation to achieve fast wavefront complex amplitude measurement.

[0004] The technical solution adopted by the present invention is as follows: A device for improving spatial resolution based on DMD common-path single-pixel detection, including a first lens 1, a second lens 2, a first digital micromirror device 3, a third lens 4, a fourth lens 5, a second digital micromirror device 6, a fifth lens 7, a sixth lens 8, a first pinhole 9, a second pinhole 10, a first detector 11, and a second detector 12. Among them, the first lens 1 and the second lens 2 form a first 4-f system, the third lens 4 and the fourth lens 5 form a second 4-f system. The first digital micromirror device 3 is located on the Fourier rear focal plane of the first 4-f system, and the second digital micromirror device 6 is located on the Fourier rear focal plane of the second 4-f system. The first pinhole 9 is located on the Fourier plane of the fifth lens 7, and the second pinhole 10 is located on the Fourier plane of the sixth lens 8. The first detector 11 is used to receive the beam signal passing through the first pinhole 9, and the second detector 12 is used to receive the beam signal passing through the second pinhole 10. The central axis of the first 4-f system forms an angle θ with the mirror surface of the first digital micromirror device 3, and the central axis of the second 4-f system forms an angle (90° - θ) with the mirror surface of the first digital micromirror device 3. The central axes of the fifth lens 7 and the sixth lens 8 respectively form an angle θ with the mirror surface of the second digital micromirror device 6 and are symmetric about the central axis of the second 4-f system. The mirror surfaces of the first digital micromirror device 3 and the second digital micromirror device 6 are opposite and form an angle (90° - θ), where 45° < θ < 90°. The columnar wavefront beam to be measured passes through the first 4-f system and irradiates onto the first digital micromirror device 3. The beam reflected by the first digital micromirror device 3 is relayed to the second digital micromirror device 6 after passing through the second 4-f system. After being modulated by the second digital micromirror device 6, the first detector 11 collects the signal intensity value of the central point on the Fourier plane of the fifth lens 7 of the beam passing through the first pinhole 9, and the second detector 12 collects the signal intensity value of the central point on the Fourier plane of the sixth lens 8 of the beam passing through the second pinhole 10.

[0005] The first pinhole 9 and the fifth lens 7 satisfy r1 = 1.27λ1 * f1 / d1, where r1 is the diameter of the first pinhole 9, λ1 is the wavelength of the beam passing through the first pinhole 9, f1 is the focal length of the fifth lens 7, and d1 is the diameter of the wavefront beam to be measured; the second pinhole 10 and the sixth lens 8 satisfy r2 = 1.27λ2 * f2 / d2, where r2 is the diameter of the second pinhole 10, λ2 is the wavelength of the beam passing through the second pinhole 10, f2 is the focal length of the sixth lens 8, and d2 is the diameter of the wavefront beam to be measured.

[0006] θ = 78°.

[0007] A method for improving spatial resolution based on DMD common-path single-pixel detection is carried out according to the following steps

[0008] Step 1: The columnar wavefront beam to be measured is irradiated onto the first digital micromirror device 3 through the first 4-f system. The beam reflected by the first digital micromirror device 3 is relayed to the second digital micromirror device 6 through the second 4-f system. Calculate the diameters of the first pinhole 9 and the second pinhole 10 according to the formulas r1 = 1.27λ1*f1 / d1 and r2 = 1.27λ2*f2 / d2;

[0009] Step 2: Determine the modulation basis mode to be loaded on the first digital micromirror device 3. The modulation basis mode is the Hadamard modulation basis or the Fourier modulation basis. The modulation basis loaded on the first digital micromirror device 3 is used to perform spatial sampling on the wavefront to be measured in the signal light part;

[0010] Step 3: Select the phase modulation mode to be loaded on the second digital micromirror device 6. The phase modulation mode is one of common-path multi-step phase-shifting interference and common-path off-axis interference; when the phase modulation mode is common-path multi-step phase-shifting interference, the second digital micromirror device 6 loads a binary phase-shifting grating and a "checkerboard" pattern. Among them, the binary phase-shifting grating is used to perform multi-step phase shifting, and the "checkerboard" is used to partition the incident light wave into a reference light part and a signal light part. The unmodulated light wave and the modulated light wave reflected by the second digital micromirror device 6 undergo common-path interference; this imaging method takes a relatively long time, but has high imaging quality and is suitable for imaging occasions that require high imaging resolution but have low time requirements. When the phase modulation mode is common-path off-axis interference, the second digital micromirror device 6 loads an inclined binary phase-shifting grating and a "checkerboard" pattern. The "checkerboard" is used to partition the incident light wave into a reference light part and a signal light part. When the inclined binary phase-shifting grating is used to perform multi-step phase shifting, a small angle greater than 0 and less than 1° is introduced between the signal light beam and the reference light beam to generate a fixed phase difference. The unmodulated light wave and the modulated light wave reflected by the second digital micromirror device 6 undergo common-path interference; this imaging method saves several times in imaging time compared with multi-step phase-shifting interference, but the imaging quality is slightly lower than that of multi-step phase-shifting interference and is suitable for imaging occasions that require faster imaging but have general requirements for imaging quality.

[0011] Step 4: Configure the initial parameters, the spatial wavefront imaging resolution M×N, the single-pixel imaging sampling rate φ. When the phase modulation mode is common-path multi-step phase-shifting interference, configure the number of phase-shifting steps. When the phase modulation mode is common-path off-axis interference, configure the period number of the inclined phase grating, that is, the deviation angle between the signal light and the reference light;

[0012] Step 5: Load the modulation mode on the first digital micromirror device 3. The modulation mode is the Hadamard modulation basis or the Fourier modulation basis. The first detector 11 and the second detector 12 collect the signal intensity of the light beam;

[0013] Step 6: When the phase modulation mode is common-path multi-step phase-shift interference, the φ×M×N modulation modes generated by single-pixel imaging are sequentially loaded onto the first digital micromirror device 3, and the binary phase-shifting grating used to implement phase-shift interference is sequentially loaded onto the second digital micromirror device 6. At the same time, the first detector 11 and the second detector 12 collect the signal intensity values corresponding to each mode. When the phase modulation mode is common-path off-axis interference, the M×N modulation modes generated by single-pixel imaging are sequentially loaded onto the first digital micromirror device 3, and the tilted binary phase-shifting grating is loaded onto the second digital micromirror device 6 to generate interference with a fixed phase difference. At the same time, the first detector 11 and the second detector 12 collect the signal intensity values corresponding to each mode.

[0014] Step 7: Reconstruct the target spatial wavefront. When the phase modulation mode is common-path multi-step phase-shift interference, the complex coefficient spectrum of the target spatial wavefront is obtained based on the phase-shift technology, and the target spatial wavefront is restored using a single-pixel reconstruction algorithm. Commonly used reconstruction algorithms include second-order correlation reconstruction, compressive sensing reconstruction, etc. When the phase modulation mode is common-path off-axis interference, the interference hologram of the target spatial wavefront is restored based on the single-pixel reconstruction algorithm, and then the target spatial wavefront is restored from the hologram according to the Fourier fringe analysis method or the Hilbert transform.

[0015] The beneficial effects of the present invention are as follows: After the detection signals on both sides of the digital micromirror device of the present invention are superimposed, the resolution of the measured wavefront complex amplitude can be doubled. The present invention is particularly suitable for some application scenarios that require high resolution and high-speed measurement, and has the advantages of fast measurement speed, high imaging resolution, and flexible and convenient device. At the same speed, the resolution of the present invention is doubled.

[0016] The present invention can select common-path multi-step phase-shift interference with better imaging quality according to the application scenario, or can also select common-path off-axis interference with further improved speed on the premise of ensuring a certain imaging quality. The present invention can perform spatial wavefront detection on the existing single-pixel imaging with different modulation modes. Benefiting from the advantages of single-pixel imaging, the present invention can be extended to wavefront measurement in a wider wavelength band, such as infrared imaging, terahertz imaging, X-ray imaging, etc., and has wide applicability in the fields of biomedical microscopy, quantum imaging, high-speed moving object imaging, and imaging through scattering media. Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of the device of the present invention;

[0018] Figure 2 It is the amplitude and phase distribution diagram of the simulated target spatial wavefront. The left figure is the simulated spatial wavefront amplitude, and the right figure is the simulated spatial wavefront phase;

[0019] Figure 3It is the amplitude and phase distribution diagrams of the target spatial wavefront reconstructed by separately detecting the signals on both sides of the second digital micromirror device using the four-step phase-shifting method. From left to right, they are: the amplitude distribution diagram and phase distribution diagram of the target spatial wavefront reconstructed from the signals received by the first detector; the amplitude distribution diagram and phase distribution diagram of the target spatial wavefront reconstructed from the signals received by the second detector;

[0020] Figure 4 It is the amplitude and phase distribution diagrams of the high-resolution target spatial wavefront achieved by adding the signals on both sides of the second digital micromirror device obtained using the four-step phase-shifting method. The left figure is the amplitude diagram obtained by reconstruction, and the right figure is the phase diagram obtained by reconstruction;

[0021] Figure 5 It is the off-axis hologram of the target spatial wavefront reconstructed by separately detecting the signals on both sides of the second digital micromirror device with the phase modulation mode of common-path off-axis interference and the amplitude and phase distribution diagrams of the target spatial wavefront reconstructed using the Fourier fringe analysis method. In the upper row, from left to right, they are the off-axis hologram, amplitude distribution diagram, and phase distribution diagram reconstructed from the signals received by the first detector; in the lower row, from left to right, they are the off-axis hologram, amplitude distribution diagram, and phase distribution diagram reconstructed from the signals received by the second detector;

[0022] Figure 6 It is the high-resolution off-axis hologram obtained by adding the reconstructed holograms of the signals on both sides of the second digital micromirror device with the phase modulation mode of common-path off-axis interference and the amplitude and phase distribution diagrams of the high-resolution target spatial wavefront reconstructed using the Fourier fringe analysis method. From left to right, they are the off-axis hologram, amplitude distribution diagram, and phase distribution diagram;

[0023] Among them, 1. First lens, 2. Second lens, 3. First digital micromirror device, 4. Third lens, 5. Fourth lens, 6. Second digital micromirror device, 7. Fifth lens, 8. Sixth lens, 9. First pinhole, 10. Second pinhole, 11. First detector, 12. Second detector. Detailed implementation mode

[0024] Example 1: As Figure 1As shown in the figure, a device for improving the spatial resolution of a common-path single-pixel detection based on a DMD includes a first lens 1, a second lens 2, a first digital micromirror device 3, a third lens 4, a fourth lens 5, a second digital micromirror device 6, a fifth lens 7, a sixth lens 8, a first pinhole 9, a second pinhole 10, a first detector 11, and a second detector 12. Among them, the first lens 1 and the second lens 2 form a first 4-f system, the third lens 4 and the fourth lens 5 form a second 4-f system. The first digital micromirror device 3 is located on the Fourier back focal plane of the first 4-f system, and the second digital micromirror device 6 is located on the Fourier back focal plane of the second 4-f system. The first pinhole 9 is located on the Fourier plane of the fifth lens 7, and the second pinhole 10 is located on the Fourier plane of the sixth lens 8. The first detector 11 is used to receive the beam signal passing through the first pinhole 9, and the second detector 12 is used to receive the beam signal passing through the second pinhole 10. The central axis of the first 4-f system forms a 78° angle with the mirror surface of the first digital micromirror device 3, and the central axis of the second 4-f system forms a 12° angle with the mirror surface of the first digital micromirror device 3. The central axes of the fifth lens 7 and the sixth lens 8 respectively form a 78° angle with the mirror surface of the second digital micromirror device 6 and are symmetric about the central axis of the second 4-f system. The mirror surfaces of the first digital micromirror device 3 and the second digital micromirror device 6 are opposite to each other and form a 12° angle. The columnar wavefront beam to be measured passes through the first 4-f system and irradiates onto the first digital micromirror device 3. The beam reflected by the first digital micromirror device 3 is relayed to the second digital micromirror device 6 after passing through the second 4-f system. After being modulated by the second digital micromirror device 6, the first detector 11 collects the signal intensity value of the central point on the Fourier plane of the fifth lens 7 of the beam passing through the first pinhole 9, and the second detector 12 collects the signal intensity value of the central point on the Fourier plane of the sixth lens 8 of the beam passing through the second pinhole 10.

[0025] The first pinhole 9 and the fifth lens 7 satisfy r1 = 1.27λ1*f1 / d1, where r1 is the diameter of the first pinhole 9, λ1 is the wavelength of the beam passing through the first pinhole 9, f1 is the focal length of the fifth lens 7, and d1 is the diameter of the wavefront beam to be measured; the second pinhole 10 and the sixth lens 8 satisfy r2 = 1.27λ2*f2 / d2, where r2 is the diameter of the second pinhole 10, λ2 is the wavelength of the beam passing through the second pinhole 10, f2 is the focal length of the sixth lens 8, and d2 is the diameter of the wavefront beam to be measured. For the present invention, λ1 = λ2.

[0026] For this embodiment, all beam diameters are the same (the beam diameters entering each lens). For this embodiment, all lenses have the same focal length and the same diameter. The first digital micromirror device 3 is used to carry the designed phase distribution and plays an expected modulation role on the transmitted wavefront. If the phase modulation mode is common-path multi-step phase-shift interference, then the second digital micromirror device 6 is used to load a binary phase-shift grating and a "checkerboard" to partition the input wavefront and cause phase-shift interference.

[0027] If the phase modulation mode is common-path off-axis interference, then the second digital micromirror device 6 is used to load a tilted phase grating and a "checkerboard" to partition the input wavefront and cause off-axis interference.

[0028] Embodiment 2: As Figures 2 - 6 shown, this embodiment is a method for improving the spatial wavefront sensing resolution based on the common-path interference single-pixel complementary detection of a digital micromirror device (DMD), and the specific steps are as follows:

[0029] Step 1: Build a device for improving the spatial wavefront sensing resolution based on the common-path interference single-pixel complementary detection of a DMD. The target spatial wavefront is obliquely irradiated onto the first digital micromirror device 3 through a 4-f system composed of the first lens 1 and the second lens 2. The first digital micromirror device 3 is initially set to the non-modulation mode. Then, the reflected light of the first digital micromirror device 3 passes through a 4-f system composed of the third lens 4 and the fourth lens 5 to relay the modulated target object wavefront to the second digital micromirror device 6. The sizes of the first pinhole 9 and the second pinhole 10 are determined according to the size of the outgoing beam on the acting surface of the second digital micromirror device 6 and the focal length of the fifth lens 7;

[0030] Step 2: Determine the modulation basis mode to be loaded on the first digital micromirror device 3;

[0031] Step 3: Determine the phase modulation mode to be loaded on the second digital micromirror device 6, and select whether to use the common-path multi-step phase-shift interference method or the common-path off-axis interference method according to the imaging scenario;

[0032] If the phase modulation mode is common-path multi-step phase-shift interference, then several binary phase-shift gratings and a "checkerboard" need to be loaded on the second digital micromirror device 6. The binary grating is used to perform multi-step phase-shifting on the reference beam, and the "checkerboard" is used to partition the incident wavefront into a reference light part and a signal light part. The unmodulated wavefront and the modulated wavefront reflected from the second digital micromirror device 6 undergo common-path interference. This imaging method takes relatively longer time but has high imaging quality and is suitable for imaging occasions that require high imaging resolution but have low time requirements;

[0033] If the phase modulation mode is common-path off-axis interference, a tilted phase grating and a "checkerboard" need to be loaded on the second digital micromirror device 6. The tilted phase grating is used to introduce a small angle between the signal beam and the reference beam to generate a fixed phase difference; the "checkerboard" is used to partition the incident wavefront into a reference light part and a signal light part, and the unmodulated wavefront and the modulated wavefront reflected from the second digital micromirror device 6 undergo common-path interference. This imaging method saves several times in imaging time compared with multi-step phase-shift interference, but the imaging quality is slightly lower than that of multi-step phase-shift interference, and it is suitable for imaging occasions that require higher-speed imaging but have general requirements for imaging quality.

[0034] Step 4: Configure the initial parameters of the detection system. The spatial wavefront imaging resolution is M×N, and the single-pixel imaging sampling rate is φ. If the selected imaging method is multi-step phase-shift interference, the number of phase-shift steps needs to be configured; if the selected imaging method is off-axis interference, the period number of the tilted phase grating needs to be configured, that is, the deviation angle between the signal light and the reference light.

[0035] Step 5: Load the modulation mode onto the first digital micromirror device 3, and the first detector 11 and the second detector 12 respectively collect the signal intensities.

[0036] If the phase modulation mode is common-path multi-step phase-shift interference, the φ×M×N modulation modes generated by single-pixel imaging are sequentially loaded onto the first digital micromirror device 3; the binary grating for phase shift is sequentially loaded onto the second digital micromirror device 6. At the same time, the first detector 11 and the second detector 12 collect the signal intensity values at the center point of the Fourier plane corresponding to each mode.

[0037] If the phase modulation mode is common-path off-axis interference, the M×N modulation modes generated by single-pixel imaging are sequentially loaded onto the first digital micromirror device 3, and the tilted phase grating is loaded onto the second digital micromirror device 6 to generate a fixed phase difference for interference. At the same time, the first detector 11 and the second detector 12 collect the signal intensity values at the center point of the Fourier plane corresponding to each mode.

[0038] Step 6: Reconstruct the target spatial wavefront.

[0039] If the phase modulation mode is common-path multi-step phase-shift interference, the complex coefficient spectrum of the target spatial wavefront is obtained based on the phase-shift technology, and the target spatial wavefront is restored using the single-pixel reconstruction algorithm.

[0040] If the phase modulation mode is common-path off-axis interference, the interference hologram of the target spatial wavefront can be restored based on the single-pixel reconstruction algorithm, and then the target spatial wavefront can be restored from the hologram according to the Fourier fringe analysis method or the Hilbert transform.

[0041] Example 3: Taking Hadamard basis, one of the commonly used single-pixel imaging modulation bases, as an example, this example uses a digital micromirror device with a binary modulation mode. This implementation is an example in which the modulation mode in Example 1 and Example 2 is the Hadamard basis mode.

[0042] Embodiment 4: Taking one of the commonly used multi-step phase shifting methods, namely four-step phase shifting, as an example, this implementation is an example of the phase shifting step number of four-step phase shifting in Embodiment 1 and Embodiment 2.

[0043] Embodiment 5: The phase modulation mode is common-path off-axis interference, including off-axis holography and slightly off-axis holography. Taking the commonly used off-axis holography as an example, this implementation is an example of off-axis interference in Embodiment 1 and Embodiment 2.

[0044] Embodiment 6: Taking the four-step phase shifting method as an example, taking the imaging of a wavefront in a space to be measured with an amplitude limited within a ring and having the letter "D" and a phase distribution in the shape of a "little rabbit" as an example, Figure 2 As shown, this embodiment performs wavefront imaging according to the steps of Example 2, and reconstructs the amplitude and phase distribution of the signals on both sides of the second digital micromirror device 6 respectively as shown in FIG. Figure 3 As shown, the final high-resolution amplitude and phase distribution obtained by adding the signals detected on both sides of the second digital micromirror device 6 is as shown in Figure 4 shown.

[0045] Example 6: Taking the phase modulation mode as common-path off-axis interference as an example, taking the imaging of a wavefront in a space to be measured with an amplitude limited within a ring and having the letter "D" and a phase distribution in the shape of a "little rabbit" as an example, Figure 2 As shown, this embodiment performs wavefront imaging according to the steps of Example 2, and reconstructs the off-axis hologram by detecting the signals on both sides of the second digital micromirror device 6 and the amplitude and phase distribution finally recovered as shown in FIG. Figure 5 As shown, the high-resolution amplitude and phase distribution of the final high-resolution off-axis hologram reconstructed by adding the detection signals on both sides of the DMD is shown in Figure 6 shown.

[0046] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A device for improving spatial resolution in common-path single-pixel detection based on DMD, characterized in that: It includes a first lens (1), a second lens (2), a first digital micromirror device (3), a third lens (4), a fourth lens (5), a second digital micromirror device (6), a fifth lens (7), a sixth lens (8), a first pinhole (9), a second pinhole (10), a first detector (11), and a second detector (12). Among them, the first lens (1) and the second lens (2) form a first 4-f system, the third lens (4) and the fourth lens (5) form a second 4-f system. The first digital micromirror device (3) is located on the Fourier rear focal plane of the first 4-f system, and the second digital micromirror device (6) is located on the Fourier rear focal plane of the second 4-f system. The first pinhole (9) is located on the Fourier plane of the fifth lens (7), and the second pinhole (10) is located on the Fourier plane of the sixth lens (8). The first detector (11) is used to receive the beam signal passing through the first pinhole (9), and the second detector (12) is used to receive the beam signal passing through the second pinhole (10). The central axis of the first 4-f system forms an angle θ with the mirror surface of the first digital micromirror device (3), and the central axis of the second 4-f system forms an angle (90° - θ) with the mirror surface of the first digital micromirror device (3). The central axes of the fifth lens (7) and the sixth lens (8) respectively form an angle θ with the mirror surface of the second digital micromirror device (6) and are symmetric about the central axis of the second 4-f system. The mirror surfaces of the first digital micromirror device (3) and the second digital micromirror device (6) are opposite and form an angle (90° - θ), where 45° < θ < 90°. The columnar wavefront beam to be measured passes through the first 4-f system and irradiates onto the first digital micromirror device (3). The beam reflected by the first digital micromirror device (3) is relayed to the second digital micromirror device (6) after passing through the second 4-f system. After being modulated by the second digital micromirror device (6), the first detector (11) collects the signal intensity value of the center point of the Fourier plane of the fifth lens (7) of the beam passing through the first pinhole (9), and the second detector (12) collects the signal intensity value of the center point of the Fourier plane of the sixth lens (8) of the beam passing through the second pinhole (10).

2. The device for improving the spatial resolution of a common-path single-pixel detection based on DMD according to claim 1, characterized in that: The first pinhole (9) and the fifth lens (7) satisfy r1 = 1.27λ1*f1 / d1, where r1 is the diameter of the first pinhole (9), λ1 is the wavelength of the beam passing through the first pinhole (9), f1 is the focal length of the fifth lens (7), and d1 is the diameter of the wavefront beam to be measured; the second pinhole (10) and the sixth lens (8) satisfy r2 = 1.27λ2*f2 / d2, where r2 is the diameter of the second pinhole (10), λ2 is the wavelength of the beam passing through the second pinhole (10), f2 is the focal length of the sixth lens (8), and d2 is the diameter of the wavefront beam to be measured.

3. The device for improving the spatial resolution of common-path single-pixel detection based on DMD according to claim 1 or claim 2, characterized in that: θ = 78°.

4. A method for improving the spatial resolution based on the common-path single-pixel detection of the device described in claim 2, characterized in that: Proceed as follows Step 1: The columnar wavefront beam to be measured is irradiated onto the first digital micromirror device (3) through the first 4-f system. The beam reflected by the first digital micromirror device (3) is relayed to the second digital micromirror device (6) through the second 4-f system. Calculate the diameters of the first pinhole (9) and the second pinhole (10) according to the formulas r1 = 1.27λ1*f1 / d1 and r2 = 1.27λ2*f2 / d2; Step 2: Determine the modulation basis mode to be loaded on the first digital micromirror device (3). The modulation basis mode is the Hadamard modulation basis or the Fourier modulation basis. The modulation basis loaded on the first digital micromirror device (3) is used to perform spatial sampling on the wavefront to be measured in the signal light part; Step 3: Select the phase modulation mode to be loaded on the second digital micromirror device (6). The phase modulation mode is one of common-path multi-step phase-shifting interference and common-path off-axis interference; when the phase modulation mode is common-path multi-step phase-shifting interference, the second digital micromirror device (6) is loaded with a binary phase-shifting grating and a "checkerboard" pattern. Among them, the binary phase-shifting grating is used for multi-step phase shifting, and the "checkerboard" is used to partition the incident light wave into a reference light part and a signal light part. The unmodulated light wave and the modulated light wave reflected by the second digital micromirror device (6) undergo common-path interference; when the phase modulation mode is common-path off-axis interference, the second digital micromirror device (6) is loaded with an inclined binary phase-shifting grating and a "checkerboard" pattern. The "checkerboard" is used to partition the incident light wave into a reference light part and a signal light part. When the inclined binary phase-shifting grating is used for multi-step phase shifting, a small angle greater than 0 and less than 1° is introduced between the signal light beam and the reference light beam to generate a fixed phase difference. The unmodulated light wave and the modulated light wave reflected by the second digital micromirror device (6) undergo common-path interference; Step 4: Configure the initial parameters, the spatial wavefront imaging resolution M×N, the single-pixel imaging sampling rate φ. When the phase modulation mode is common-path multi-step phase-shifting interference, configure the number of phase-shifting steps. When the phase modulation mode is common-path off-axis interference, configure the number of periods of the inclined phase grating, that is, the deviation angle between the signal light and the reference light; Step 5: Load the modulation mode on the first digital micromirror device (3). The modulation mode is the Hadamard modulation basis or the Fourier modulation basis. The first detector (11) and the second detector (12) collect the signal intensity of the beam; Step 6: When the phase modulation mode is common-path multi-step phase-shifting interference, load the φ×M×N modulation patterns generated by single-pixel imaging onto the first digital micromirror device (3) in sequence, and load the binary phase-shifting grating used to achieve phase-shifting interference onto the second digital micromirror device (6) in sequence. At the same time, the first detector (11) and the second detector (12) collect the signal intensity values corresponding to each pattern. When the phase modulation mode is common-path off-axis interference, load the M×N modulation patterns generated by single-pixel imaging onto the first digital micromirror device (3) in sequence, and load the tilted binary phase-shifting grating onto the second digital micromirror device (6) to generate interference with a fixed phase difference. At the same time, the first detector (11) and the second detector (12) collect the signal intensity values corresponding to each pattern. Step 7: Reconstruct the target spatial wavefront. When the phase modulation mode is common-path multi-step phase-shifting interference, obtain the complex coefficient spectrum of the target spatial wavefront according to the phase-shifting technique, and use the single-pixel reconstruction algorithm to restore the target spatial wavefront (common reconstruction algorithms include second-order correlation reconstruction, compressive sensing reconstruction, etc.). When the phase modulation mode is common-path off-axis interference, restore the interference hologram of the target spatial wavefront according to the single-pixel reconstruction algorithm, and then restore the target spatial wavefront from the hologram according to the Fourier fringe analysis method or the Hilbert transform.

Images