CN106990694B - A non-iterative phase recovery device and method under partially coherent light illumination - Google Patents

Abstract

The invention relates to a non-iterative phase recovery device and a non-iterative phase recovery method under the illumination of partial coherent light, and the non-iterative phase recovery device comprises a partial coherent light generating unit and an object phase measuring unit, wherein the partial coherent light generating unit comprises a laser, a beam expander, a focusing lens, a rotating ground glass sheet, a collimating lens and a Gaussian filter sheet, and a spiral phase plate can be arranged between the beam expander and the focusing lens; the object phase measuring unit comprises a beam splitter, a spatial light modulator, a reflector, a porous array plate, a Fourier lens, a charge coupling element and a computer. Compared with an iterative algorithm, the method has the advantages that the recovery process is faster, and real-time object information recovery can be realized; compared with a mode expansion method, the method has wider application range and can realize the object information recovery under the illumination of the part of coherent light with unknown associated structure; meanwhile, the method can be widely applied to lens-free diffraction imaging of X rays; the device has the advantages of simplicity, wide application range, high recovery speed and the like, and has important application prospect.

Description

A device and method for non-iterative phase recovery under partially coherent light illumination

technical field

The present invention relates to the field of optical technology, and in particular, to a non-iterative phase recovery device and method under partially coherent light illumination.

Background technique

For an unknown object containing amplitude and phase information, the amplitude information of the object can be directly observed through the charge-coupled element, but the phase information cannot be directly obtained. Therefore, how to obtain the phase information of the unknown object from the intensity information has become a research topic. an important subject. The technology of obtaining the phase information of the object from the intensity information is called wavefront detection technology or phase recovery. The method of obtaining the phase information of the object through diffraction or interference to realize two-dimensional and three-dimensional imaging is called coherent diffraction imaging, which is widely used in image information. processing, micro-nano optics, adaptive optics, materials science, and quantum tomography. With the rapid development of coherent diffraction imaging technology, the resolution has reached the nanometer level, and the recovery device has become more intelligent and real-time.

When studying wavefront detection technology and phase recovery, most of them assume that the illumination light source is completely coherent light, but in practical applications, such as high-resolution wavefront detection, X-rays or electron beams are often used as light sources for phase recovery, which are not completely coherent light. In addition, when a beam of fully coherent light is transmitted through the medium, its spatial coherence will also be reduced. In these cases, it is still treated as fully coherent light, there will be some problems.

There are many ways to achieve phase recovery. As early as 1952, David Sayre proposed to use Shannon's theorem to achieve phase recovery by measuring higher-density light intensity. So far, a series of phase recovery methods have been developed, such as Hartmann wavefront sensing technology, holographic interference technology, computational phase recovery technology and stacking technology.

Hartmann wavefront sensing technology mainly recovers phase information by measuring the wavefront slope (Platt B C, Shack R. History and principles of Shack-Hartmann wavefront sensing[J]. Journal of Refractive Surgery, 2001, 17(5): S573-S577.), based on this technology, the Shack Hartmann sensor is composed of a microlens array and a charge-coupled element. By measuring the coordinates of the light spot focused on the charge-coupled element through the microlens, the Zernike polynomial mode method is used to calculate the Zernike coefficients to reconstruct the wavefront. The technology has fast recovery speed and high sensitivity, and has been widely used in high-resolution imaging of astronomical telescopes and retinal cell-resolved imaging of human eyes.

Holographic interference technology is a technology that uses the principle of interference to restore the optical field of matter waves (Eisebitt S, Lüning J, Schlotter WF, et al. Lensless imaging of magnetic nanostructures by X-rayspectro-holography [J]. Nature, 2004, 432(7019): 885-888.), which is divided into two processes: shooting and recovery. When a beam of reference light interferes with the object light, the phase and amplitude information of the object will be recorded in the interferogram, and then the holographic interferogram can be illuminated with the reference light. The light field information of the object light is recovered, so as to extract the phase and amplitude information of the object. With the rapid development of holographic interference technology, charge-coupled elements are used to record the interference pattern, and the computer performs the phase recovery process. This technology has become a digital holography technology, which is widely used in three-dimensional image reconstruction, digital microscopic imaging, and non-destructive testing of materials. , medical diagnosis, etc.

Compared with the previous two methods, the computational phase recovery method has a wider application range, and is applicable to both visible light and extreme ultraviolet wavelengths. This recovery method was proposed in 1972 (Gerchberg R W.A practical algorithm for the determination of phase from image and diffraction plane pictures[J]. Optik, 1972, 35:237.), which uses an iterative algorithm from the intensity information of the diffracted light spots captured. This method can be used in imaging systems using X-rays or free electron beams as light sources to achieve lensless diffraction imaging and phase recovery, thereby reducing imaging system errors and simplifying system structure. prospect. Another stack imaging technique using an iterative algorithm (Rodenburg J M, Faulkner H M L. A phase retrieval algorithm for shifting illumination[J]. Applied physics letters, 2004, 85(20): 4795-4797.) is an emerging technology in the past decade. By searching for a unique complex solution that satisfies the constraints of multiple far-field diffraction intensity images in the mode of overlapping scanning of the sample, it is not limited by the optical focusing element, so it can break through the diffraction limit to achieve super-resolution imaging.

However, these technologies all have certain shortcomings and drawbacks. The iterative algorithm for calculating the phase recovery method requires a large number of iterations and iteration time. For complex phase objects, the fast and real-time recovery of information cannot be achieved, and there may even be cases where a unique solution cannot be obtained. Happening. Moreover, when the existing iterative algorithm processes partially coherent light, it assumes that the cross-correlation function of the light source is a Gaussian Shell mode, and uses mode expansion for processing. However, when the coherence degree is very low, a large number of modes are required to correctly recover the phase information. , and for light sources whose correlation function is unknown, this mode expansion method will no longer apply.

Based on the above defects in object information recovery under partially coherent light illumination, this patent innovatively proposes a new non-iterative method for phase information recovery under partially coherent light illumination, which has the advantages of wide application range, fast recovery speed, The device is simple and has important scientific research and practical application value.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned technical problems, the purpose of the present invention is to provide a non-iterative phase recovery device and method under partial coherent light illumination, which avoids the tediousness and complexity of the iterative algorithm, makes up for the drawbacks of the mode expansion method, and can realize in traditional correlation or Correct and real-time recovery of phase object information under the illumination of light sources with complex or even unknown correlation structures.

The non-iterative phase recovery device under partially coherent light illumination of the present invention includes a partially coherent light generating unit and an object phase measuring unit, wherein the object phase measuring unit includes

- a beam splitter for transmitting the partially coherent light generated by the partially coherent light generating unit and reflecting the light beam modulated by the spatial light modulator;

- a spatial light modulator, placed perpendicular to the optical axis of the partially coherent light generating unit, for loading the phase object to be measured and the perturbation point for phase perturbation of the phase object to be measured, the spatial light modulator reflects the split beam the light transmitted by the mirror, and let the modulated light reflect again through the beam splitter;

- a perforated array plate through which the beams reflected by the beam splitter pass, the perforated array plate is provided with a periodically arranged two-dimensional array of small holes and a reference hole near the center of the array, the perforated array plate The reference hole on the beam splitter is aligned with the beam reflected by the beam splitter, and the distance between the multi-hole array plate and the spatial light modulator satisfies z ≥ d*L/λ, where d is the distance between the holes on the multi-hole array plate interval, L is the size of the widest point of the phase object to be measured, λ is the wavelength of the laser light source in the partially coherent light generating unit;

- a Fourier lens, placed immediately after the multiwell array plate, or enabling the multiwell array plate to be located on the front focal plane of the Fourier lens, for Fourier analysis of the light beam passing through the multiwell array plate leaf transform;

- Charge-coupled element, placed at the Fourier plane to capture light intensity information;

- a computer, connected with the spatial light modulator and the charge-coupled element, controls the phase loading on the spatial light modulator, and performs real-time inverse Fourier transform, screening and inverse transmission processing on the light intensity obtained by shooting to obtain Phase information of the object.

Further, when the purpose is to generate the partially coherent light associated with the traditional Gaussian, the partially coherent light generating unit includes a laser arranged in sequence, a beam expander that expands the laser beam emitted by the laser, and a collimator that collimates the beam. A straight lens and a Gaussian filter for shaping the beam, the light from the Gaussian filter is transmitted through the beam splitter and reaches the spatial light modulator.

Further, when the purpose is to generate the partially coherent light of the Laguerre-Gaussian correlation, the partially coherent light generating unit comprises the laser arranged in sequence, the beam expander for expanding the laser beam emitted by the laser, and the beam expander. The helical phase plate for changing the phase of the rear light, the collimating lens for collimating the beam, and the Gaussian filter for shaping the beam, the light from the Gaussian filter is transmitted through the beam splitter and reaches the Spatial Light Modulator.

Further, the partially coherent light generating unit further includes a coherence degree adjustment component, and the coherence degree adjustment component includes a focusing device for the beam expanded by the beam expander or the beam whose phase is changed by the helical phase plate. a lens, and a rotating frosted glass that scatters the focused light beam, and the light scattered by the rotating frosted glass is collimated by the collimating lens.

Further, the light beam reflected by the beam splitter can also be reflected to the porous array plate by a mirror.

Further, the disturbance point is located at any position of the object to be measured, its size is much smaller than the size of the object to be measured, and its phase assignment is different from the phase of the original object to be measured at this position.

Further, a reference small hole is etched on the opaque substrate by laser, and the reference small hole is used as the center of the circle to offset a certain distance in the x and y directions, and then the two-dimensional small hole array is symmetrically laser etched to form the porous structure. For the array plate, the interval between the two-dimensional holes should satisfy d≤z*λ/L, where z is the distance from the object plane to the porous array plate, L is the size of the widest point of the phase object to be measured, and λ is the part The wavelength of the laser light source in the coherent light generating unit; the size of the offset satisfies a/2≤Δx=Δy≤d/2-a/2, where a is the size of the two-dimensional small hole; the reference small hole and each two-dimensional small hole are The size of the holes is the same, which needs to be much smaller than the size of the object to be measured, and less than one-third of the interval between the two-dimensional small holes; the structure of the porous array plate can also be simulated by the spatial light modulator.

Further, the spatial light modulator is a reflective pure-phase spatial light modulator.

Further, the beam splitter is a half mirror with a light intensity of 50:50.

The method for non-iterative phase recovery using the above-mentioned non-iterative phase recovery device under partially coherent light illumination of the present invention includes the steps of:

(1) Obtaining partially coherent light associated with Gaussian or partially coherent light associated with Laguerre Gaussian through the partially coherent light generating unit, and changing the focus on the Rotate the spot size on the frosted glass to adjust the spatial coherence of the light source;

(2) The partial coherent light is transmitted to the object phase measurement unit, so that the partial coherent light passes through the object to be measured and records the light intensity information:

(21) When the partially coherent light is partially coherent light with Gaussian correlation, record the light intensity twice, the first shot - load the phase object to be measured: set the prepared image to grayscale image mode, when the image is loaded When it reaches the pure-phase spatial light modulator, the gray value will be converted into the corresponding phase; the second shot - place a disturbance point at any position of the object to be measured, and its size needs to be much smaller than the size of the object to be measured. , the phase assignment is different from the phase of the original phase object to be measured at this position; the light intensity information obtained by the two shots is sent to the computer for processing: First, the two groups of light intensity information are respectively Fourier transform, Then, it is screened by the screening array, and then the screened results are subtracted, and the subtracted results are reversely transmitted to extract the phase information of the object; the screening holes of the screening array are periodically arranged two-dimensional holes , generated by the computer, and the side length and interval of each screening hole are consistent with the multi-hole array plate;

(22) When the partially coherent light is the partially coherent light of the Laguerre-Gaussian correlation, record the light intensity four times, and take the first shot - load the object to be measured: set the prepared image to grayscale mode, when When the picture is loaded on the pure-phase spatial light modulator, the gray value will be converted into the corresponding phase; the second shot - place a disturbance point at any position of the phase object to be measured, and its size is much smaller than that of the phase to be measured. The size of the object, its phase assignment is different from the phase of the original phase object to be measured at this position; the third shot - remove the object to be measured but do not remove the disturbance point, that is, the area where the original phase object to be measured is located. The phase is set to 0; the fourth shot—removes the disturbed phase; the two light intensity information obtained from the third and fourth shots are sent to the computer for processing: first, Fourier is performed on the two sets of light intensity information respectively. Leaf transformation, and then screened by the screening array, secondly, the filtered results are subtracted, and the subtracted results are inversely transmitted to extract the cross-spectral density information and phase information of the light source; The two light intensity information obtained by the second shooting is sent to the computer for processing: first, the two sets of light intensity information are subjected to Fourier transform respectively, and then screened by the screening array, and then the screened results are subtracted, and the subtracted After inverse transmission of the result, the phase information of the object affected by the phase of the light source can be extracted; finally, the phase of the light source can be removed by the phase of the object affected by the phase of the light source, and the correct phase information of the object can be obtained; the screening of the screening array is small. The holes are periodically arranged two-dimensional small holes, which are generated by the computer, and the side length and interval of each screening small hole are consistent with the multi-hole array plate.

By means of the above scheme, the present invention has at least the following advantages:

Compared with the iterative algorithm, the present invention is more rapid and real-time for the recovery of the phase information of the object under partial coherent light illumination. Compared with the mode expansion, the iterative algorithm for processing partial coherent light has a wider range of applications, and has a wider range of applications for processing complex correlation structures. Even in the case of unknown partially coherent light illumination, the phase recovery of the object has unique advantages; the lensless diffraction imaging phase recovery device of the present invention can be extended to the X-ray imaging system, so it has extremely important significance in practical applications .

The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly, and implement it according to the content of the description, the preferred embodiments of the present invention are described in detail below with the accompanying drawings.

Description of drawings

1 is a schematic structural diagram of a non-iterative phase recovery device under partially coherent light illumination of the present invention;

Fig. 2 is an example of loading the object to be measured and disturbance on the spatial light modulator, wherein Fig. 2(a) only loads the object information, and Fig. 2(b) loads a disturbance on the object information;

Fig. 3(a) is a detail view of the center portion of the multiwell array plate used in the present invention; Fig. 3(b) is a detail view of the center portion of the screening array used in computer recovery.

Detailed ways

The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. The following examples are intended to illustrate the present invention, but not to limit the scope of the present invention.

The phase recovery method proposed by the present invention includes three processes: generating a partially coherent light source with Gaussian correlation or special correlation, passing through an object carrying phase information and recording the light intensity, and computer processing to recover the phase. The corresponding structural device is shown in FIG. 1 .

First, a partially coherent light source is generated, which irradiates the object to be measured and passes through the multi-hole array plate, and uses the charge-coupled element to record the intensity of the spot light in the Fourier plane. Generally, only two shots are required to recover the complete phase information of the object to be measured. The first shot is to let the light source illuminate the object to be tested, and then transmit a distance to the specially designed multi-hole array plate, and then record the light intensity information by the charge-coupled element placed on the Fourier plane. The disturbance point is added in the middle of the measuring object, and then the light intensity information is recorded by the charge-coupled element after the same transmission process. After two shots, the computer program is used to recover the object light information. However, if the light source is not Gaussian correlation, the recovered object light information will be affected by the light source correlation structure. In this case, the object needs to be removed, and the rest remain unchanged. According to the above steps, two more shots are taken, and the computer After processing the recovery, the cross spectral density equation of the light source is obtained. Finally, the correct object amplitude and phase information can be obtained by dividing the two recovery results.

The structure of the partially coherent light generating unit of Gaussian correlation in the present invention includes: the laser beam emitted by the laser 1 is expanded by the beam expander 2, and then focused by the focusing lens 4 on the rotating ground glass sheet 5, and the emitted light is emitted by the collimating lens. 6 is collimated and shaped by a Gaussian filter 7. The focusing lens 4 and the rotating ground glass sheet 5 constitute a coherence adjustment system. By changing the positions of the focusing lens 4 and the rotating ground glass sheet 5, the coherence degree of the outgoing light can be changed. This is because the size of the light spot focused on the rotating ground glass sheet 5 directly It affects the coherence of the outgoing light. The larger the focused spot, the lower the coherence, and the smaller the focused spot, the higher the coherence. The light beam after passing through the Gaussian filter 7 is the partially coherent light of the Gaussian correlation, that is, the required light source. If a helical phase plate 3 is placed between the beam expander 2 and the focusing lens 4, and the others remain unchanged, then the Gaussian filter 7 produces the partially coherent light of the Laguerre-Gaussian correlation, that is, the required special correlation part coherent light source.

The structure of the object phase measurement unit in the present invention specifically includes: after generating a partially coherent light source, it is vertically incident on the spatial light modulator 9 through a beam splitter 8. A mirror, an object carrying phase information is loaded on the spatial light modulator 9. After passing through the spatial light modulator 9, the light reflected by it passes through the beam splitter 8, and then is reflected on the porous array plate 13. The spatial light modulator 9. There is a certain distance from the multi-hole array plate 13, and the distance satisfies the formula z≥d*L/λ, where d is the interval between the small holes on the multi-hole array plate 13, L is the dimension of the widest part of the object to be measured, and λ is the laser The wavelength of the light source. The multiwell array plate 13 consists of a periodically arranged two-dimensional array of small holes, and there is a reference small hole in the middle of the array. The light beam reaching the multi-hole array plate 13 needs to be aligned with the reference hole, and the Fourier lens 12 is placed immediately after the multi-hole array plate 13, or the multi-hole array plate can be positioned on the front focal plane of the Fourier lens, and finally the charge-coupled element 11 Take light intensity information at the Fourier plane. The light intensity captured by the charge-coupled element here needs to be sent to the computer 10 for real-time inverse Fourier transform, screening array screening and inverse transmission processing to obtain the phase information of the object.

The basis and principle of the present invention are as follows:

The cross spectral density of the light source is expressed as W ₀ (ρ ₁ ,ρ ₂ ), and the object to be measured is expressed as O(ρ). After the light source illuminates the object to be measured, the cross spectral density equation transmitted to the multi-hole array plate can be expressed as :

W(r ₁ ,r ₂ )=∫∫W ₀ (ρ _1,ρ2 )O(ρ ₁ )O(ρ ₂ ) ^* P(ρ ₁ ,r ₁ )P(ρ ₂ ,r ₂ ) ^* dρ ₁ dρ ₂ (1)

where P(ρ,r) is the transfer term from the object plane to the multiwell array plate. Well array plates can be represented by the delta function:

M(r)=δ(r)+∑ _mn δ(rr _mn ) (2)

where r _mn =(md+Δx,nd+Δy) are the coordinates of the periodic holes on the multiwell array plate, m and n are integers, d is the spacing between the array holes, and Δx and Δy represent the array near the reference hole The offset of the hole in the x and y directions from the center point, δ(r) is the reference hole at the center. The light intensity I(κ) reaches the Fourier plane after passing through the porous array plate, and then performs inverse Fourier transform, which corresponds to the cross-spectral density equation of the light field after the light passes through the porous array plate:

where r _mn -r _pq =[(mp)d,(nq)d], where p and q are integers. Next, a computer program was used to simulate the inverse Fourier-transformed cross-spectral density through a screening array that had a similar distribution to the multiwell array plate, but lacked a reference well. After this screening array, W(-r _mn ,0) or W(0,r _mn ) ^* can be filtered out, because the porous array is not strictly centered on the reference hole, therefore, only one cross spectral density equation can be screened out . It is obtained by formula (3):

where T _O (ρ ₁ ,ρ ₂ )=∫W ₀ (ρ ₁ ,ρ ₂ )O(ρ ₂ ) ^* P(ρ ₂ ,0) ^* dρ ₂ , then if W(r _mn ,0) is performed Inverse transmission, what is obtained is T _O (ρ ₁ ,ρ ₂ )O(ρ ₁ ), which is not the correct information required, therefore, a second shot is required. A disturbance is loaded on the object to be measured, which is mathematically expressed as Cδ(ρ-ρ ₀ ), where C is a complex constant and ρ ₀ is the coordinate of the disturbance. The W′(r _mn ,0) obtained from the second shot is expressed as:

Subtract the before and after results to get:

At this time, the reverse transmission is performed, and only W ₀ (ρ ₁ ,ρ ₀ )O(ρ ₁ ) is left. For the partially coherent light associated with Gaussian, its phase is 1, and the recovered phase is the object O(ρ ₁ ) The phase carried, when the illumination light source is not Gaussian correlation but partially coherent light with special correlation, the object needs to be removed in the optical path, and W ₀ (ρ ₁ , ρ ₀ ) is obtained by the same experiment and processing method, and then the The correct phase information can be obtained by dividing the before and after results.

The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

Embodiment 1: Recovery of phase information of an object under Gaussian correlation partially coherent light illumination.

1. Generation of partially coherent light source with Gaussian correlation: its structure includes a power-adjustable semiconductor-pumped solid-state laser 1, which emits a laser wavelength of 532 nm, and the laser beam emitted by the laser is expanded by a beam expander 2. The beam after the beam is focused on the rotating ground glass sheet 5 by the focusing lens 4 , the scattered light is collimated by the collimating lens 6 , and then shaped by the Gaussian filter 7 . The light coming out of the Gaussian filter is the partially coherent light of the Gaussian correlation. Here, the focal length of the focusing lens 4 is 80 mm, and the focal length of the collimating lens 6 is 150 mm.

1.1. Adjust the spatial coherence of the light source: the spatial coherence of the light source is directly related to the spot size focused on the rotating ground glass sheet. Therefore, by adjusting the front and rear positions of the focusing lens 4 on the optical axis, the focus on the rotating ground glass sheet can be changed. The size of the spot on 5, when the focused spot is smaller, the coherence of the outgoing light is higher, on the contrary, the larger the focused spot is, the lower the coherence of the outgoing light.

2. The unit where the light source passes through the object and records the light intensity: the partially coherent light source generated in the previous step is transmitted through the beam splitter 8 and reaches the reflective pure-phase spatial light modulator 9 . The beam splitter is a half mirror with a light intensity of 50:50, and the reflective spatial light modulator is placed perpendicular to the optical axis of the partially coherent light generating unit. The spatial light modulator 9 is connected to the computer 10, and the computer 10 controls the phase loading on the spatial light modulator. The phase-modulated outgoing light passes through the beam splitter again and is reflected. In order to save the space occupied by the device, the reflected light is reflected again by a reflecting mirror 14 and reaches the porous array plate 13 after being transmitted for 1170 mm. The transmission distance of the light beam from the spatial light modulator to the multi-hole array plate must satisfy the condition z≥d*L/λ, where d is the interval of the small holes of the multi-hole array plate, L is the size of the widest part of the object to be measured, and λ is the laser light source wavelength. Immediately after the multi-hole array plate, a Fourier lens 12 with a focal length of 150 mm is placed, and the charge-coupled element 11 connected to the computer 10 is placed at the Fourier plane, and the light intensity is recorded.

The whole process needs to record the light intensity twice. The only difference between the two shooting processes is that the phase loading on the spatial light modulator 9 is different: the first shooting, the object to be measured is loaded, as shown in Figure 2(a); the second For the second shooting, place a disturbance point in the middle of the object to be measured, as shown in Figure 2(b). The disturbance point is a square with a side length of 240 μm, and its phase assignment is equal to the phase of the original object to be measured at this position minus 0.8π , in order to achieve the perturbation effect.

2.1. Load phase information on the reflective spatial light modulator: First, set the prepared image to grayscale image mode. When the image is loaded on a phase-only spatial light modulator (model Holoeye-Pluto, pixel size 1920×1080, pixel size 8μm), the gray value will be converted to the corresponding phase.

2.2. The multi-hole array plate used in the design experiment: use laser etching to make a 18mm×14mm multi-hole array plate, the substrate as a whole is opaque to light, and then drill holes, where a square hole with a side length of 54 μm is placed at the origin. , and then offset Δx=117 μm and Δy=117 μm from the origin to the x and y directions respectively, and arrange the small hole array symmetrically with this as the center of the circle, as shown in Figure 3(a), in which there are 66 small holes in the x direction and 48 small holes in the y direction. The side length of each small hole is 54 μm, and the interval between the small holes is d=270 μm. It is worth noting that Δx=Δy≠d/2. (The multiwell array plate can also be replaced with a transmissive spatial light modulator). In the experiment, the beam reaching the multiwell array plate is aimed at the reference well.

3. Calculate the recovery phase: the light intensity information obtained by the two shots is sent to the computer 10 for processing. Firstly, Fourier transform is performed on the two sets of light intensity information respectively, and then it is screened by the screening array. Second, the filtered results are subtracted, and the subtracted results are inversely transmitted to extract the phase information of the object.

3.1. Design the screening array used in computer recovery: the screening array is not an actual object, but an array for screening information that needs to be used in program processing. Its distribution is shown in Figure 3(b), the only difference from the experimental multi-well array plate is the lack of the reference hole in the middle, and other parameters are consistent.

Embodiment 2: Recovering the phase information of an object under the illumination of special associated partially coherent light.

1. The generation of a special associated partially coherent light source: its structure includes a power-adjustable semiconductor-pumped solid-state laser 1 with a wavelength of 532 nm. The laser beam emitted by the laser is expanded by a beam expander 2, and the expanded beam After passing through the helical phase plate 3 with a topological charge number of 2, it is focused by the focusing lens 4 onto the rotating frosted glass plate 5. The scattered light is collimated by the collimating lens 6, and then shaped by the Gaussian filter 7. Here, the focal length of the focusing lens 4 is 80 mm, and the focal length of the collimating lens 6 is 150 mm. The light coming out of the Gaussian filter is the partially coherent light of the Laguerre-Gaussian correlation. The partially coherent light of the Laguerre-Gaussian correlation is used as the illumination light source to illustrate the phase recovery process in the case of complex correlation structure.

1.1. Adjust the spatial coherence of the light source: The spatial coherence of the light source is directly related to the spot size focused on the frosted glass sheet. Therefore, by adjusting the front and rear positions of the focusing lens 4 on the optical axis, the focus on the rotating ground glass sheet 5 can be changed. When the focused spot is smaller, the coherence of the outgoing light is higher, and conversely, the larger the focused spot is, the lower the coherence of the outgoing light.

2. The unit where the light source passes through the object and records the light intensity: the partially coherent light source of the Laguerre-Gaussian correlation generated in the previous step is transmitted through the beam splitter 8 and reaches the reflective pure-phase spatial light modulator 9 . The beam splitter is a half mirror with a light intensity of 50:50, and the reflective spatial light modulator is placed perpendicular to the optical axis of the partially coherent light generating unit. The spatial light modulator 9 is connected to the computer 10, and the computer 10 controls the phase loading on the spatial light modulation. The phase-modulated outgoing light passes through the beam splitter again and is reflected. In order to save the space occupied by the device, the reflected light is reflected again by a reflecting mirror 14 and reaches the porous array plate 13 after being transmitted for 1170 mm. The transmission distance of the light beam from the spatial light modulator to the multi-hole array plate must satisfy the condition z≥d*L/λ, where d is the interval of the small holes of the multi-hole array plate, L is the size of the widest part of the object to be measured, and λ is the laser light source wavelength. Immediately after the multi-hole array plate, a Fourier lens 12 with a focal length of 150 mm is placed, and the charge-coupled element 11 connected to the computer 10 is placed at the Fourier plane, and the light intensity is recorded.

The whole process requires a total of 4 light intensity recordings. The only difference in the 4 shooting processes is that the phase loading on the spatial light modulator 9 is different: the first shooting, loading the phase object to be measured, as shown in Figure 2(a); the second For the second shooting, place a disturbance point in the middle of the object to be measured, as shown in Figure 2(b). The disturbance point is a square with a side length of 240 μm, and its phase assignment is equal to the phase of the original object to be measured at this position minus 0.8π , to achieve the perturbation effect; for the third shot, remove the phase object without removing the perturbation loading (removing the phase object does not mean removing the spatial light modulator, but setting the phase of the area where the original object is located to 0) ; 4th shot, remove perturbation loading.

2.1. Load phase information on the reflective spatial light modulator: First, set the prepared image to grayscale image mode. When the image is loaded on a phase-only spatial light modulator (model Holoeye-Pluto, pixel size 1920×1080, pixel size 8μm), the gray value will be converted to the corresponding phase.

2.2. The multi-hole array plate used in the design experiment: use laser etching to make a 18mm×14mm multi-hole array plate, the substrate as a whole is opaque to light, and then drill holes, where a square hole with a side length of 54 μm is placed at the origin. , and then offset Δx=117 μm and Δy=117 μm from the origin to the x and y directions respectively, and arrange the small hole array symmetrically with this as the center of the circle, as shown in Figure 3(a), in which there are 66 small holes in the x direction and 48 small holes in the y direction. The side length of each small hole is 54 μm, and the interval between the small holes is d=270 μm. It is worth noting that Δx=Δy≠d/2. (The multiwell array plate can also be replaced with a transmissive spatial light modulator). In the experiment, the beam reaching the multiwell array plate is aimed at the reference well.

3. Calculating the restored phase: for the shooting results of the above-mentioned 3rd and 4th time-removed phase objects: the light intensity information obtained by the two shots is sent to the computer 10 for processing. First, the two sets of light intensity information are subjected to Fourier transform, and then screened by the screening array. Second, the filtered results are subtracted, and the subtracted results are inversely transmitted to extract the cross spectral density information of the light source. and its phase information. Regarding the above-mentioned first and second photographing results of objects with phase: the light intensity information obtained by the two photographing is sent to the computer 10 for processing. Firstly, Fourier transform is performed on the two sets of light intensity information respectively, and then they are screened by the screening array. Second, the filtered results are subtracted, and the subtracted results are inversely transmitted, so that the objects affected by the phase of the light source can be extracted. phase information. Finally, the phase of the light source is removed by the phase of the object affected by the phase of the light source, and the correct phase information of the object can be obtained.

3.1. Design the screening array used in computer recovery: the screening array is not an actual object, but an array for screening information that needs to be used in program processing. Its distribution is shown in Figure 3(b), the only difference from the experimental multi-well array plate is the lack of the reference hole in the middle, and other parameters are consistent.

The whole process includes four times of light intensity recording and data processing. The processing process is simple, so the whole process takes very little time, and almost real-time recovery can be achieved.

The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. It should be pointed out that for those skilled in the art, some improvements can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims (8)

1. A non-iterative phase recovery device under partially coherent illumination, characterized by: comprises a partially coherent light generation unit and an object phase measurement unit including

A beam splitter for transmitting the partially coherent light generated by the partially coherent light generation unit and reflecting the light beam modulated by the spatial light modulator;

a spatial light modulator, disposed perpendicular to the optical axis of the partially coherent light generating unit, for loading the phase object to be measured and disturbance points for performing phase disturbance on the phase object to be measured, the spatial light modulator reflecting the light transmitted by the beam splitter and allowing the modulated light to be reflected again by the beam splitter;

A porous array plate, through which the light beam reflected by the beam splitter passes, wherein a two-dimensional aperture array arranged periodically is arranged on the porous array plate, a reference aperture is arranged near the center of the array, the reference aperture on the porous array plate is aligned with the light beam reflected by the beam splitter, and the distance between the porous array plate and the spatial light modulator satisfies z ≥ d x L/lambda, wherein d is the interval between the apertures on the porous array plate, L is the size of the widest part of the phase object to be measured, and lambda is the wavelength of the laser light source in the partially coherent light generating unit;

-a fourier lens placed immediately behind the multi-well array plate or capable of having the multi-well array plate located in a front focal plane of the fourier lens for fourier transforming the light beam passing through the multi-well array plate;

-a charge coupled element placed at the fourier plane to capture the light intensity information;

the computer is connected with the spatial light modulator and the charge coupled device, controls phase loading on the spatial light modulator, and performs real-time inverse Fourier transform, screening and inverse transmission processing on the shot light intensity to obtain phase information of the object;

when the purpose is to generate partial coherent light of the traditional Gaussian correlation, the partial coherent light generating unit comprises a laser, a beam expander for expanding a laser beam emitted by the laser, a collimating lens for collimating the light beam and a Gaussian filter for shaping the light beam which are sequentially arranged, and the light emitted by the Gaussian filter transmits through the beam splitter to reach the spatial light modulator;

The partially coherent light generating unit further comprises a coherence adjusting assembly, the coherence adjusting assembly comprises a lens for focusing the light beam with the phase changed by the light beam expanded by the beam expander and rotating ground glass for scattering the focused light beam, and the light scattered by the rotating ground glass is collimated by the collimating lens.

2. The non-iterative phase recovery apparatus under illumination by partially coherent light of claim 1, wherein: when the purpose is to generate Laguerre Gaussian related partial coherent light, the partial coherent light generating unit comprises a laser, a beam expander for expanding a laser beam emitted by the laser, a spiral phase plate for changing the phase of the expanded light, a collimating lens for collimating the light beam and a Gaussian filter for shaping the light beam, which are sequentially arranged, and the light emitted by the Gaussian filter is transmitted through the beam splitter and reaches the spatial light modulator.

3. The non-iterative phase recovery apparatus under illumination by partially coherent light of claim 1, wherein: the beam reflected by the beam splitter may also be reflected by a mirror onto the porous array plate.

4. The apparatus for non-iterative phase recovery under illumination by partially coherent light of claim 1, wherein: the disturbance point is positioned at any position of the phase object to be measured, the size of the disturbance point is far smaller than that of the phase object to be measured, and the phase assignment of the disturbance point is different from that of the original phase object to be measured at the position.

5. The non-iterative phase recovery apparatus under illumination by partially coherent light of claim 1, wherein: etching a reference small hole on a lightproof substrate by laser, and symmetrically laser etching a two-dimensional small hole array by taking the reference small hole as a circle center and respectively offsetting a certain distance to the x direction and the y direction to form the porous array plate, wherein the interval between the two-dimensional small holes needs to satisfy that d is not more than z lambda/L, wherein z is the distance from an object plane to the porous array plate, L is the size of the widest position of a phase object to be detected, and lambda is the wavelength of a laser light source in a partial coherent light generation unit; the offset is a/2 ≤ Δ x ≤ Δ y ≤ d/2-a/2, wherein a is the size of the two-dimensional pore; the sizes of the reference small holes and the two-dimensional small holes are consistent, and the reference small holes are far smaller than the size of the object to be measured and smaller than one third of the interval of the two-dimensional small holes; the porous array plate may be replaced with a transmissive spatial light modulator.

6. The non-iterative phase recovery apparatus under illumination by partially coherent light of claim 1, wherein: the spatial light modulator is a reflective phase-only spatial light modulator.

7. The non-iterative phase recovery apparatus under illumination with partially coherent light according to claim 3, wherein: the beam splitter is a light intensity 50: 50 half mirror.

8. A method of non-iterative phase recovery using a non-iterative phase recovery device under illumination with partially coherent light according to any of claims 1 to 7, comprising the steps of:

(1) acquiring Gaussian-related partial coherent light or Laguerre Gaussian-related partial coherent light through a partial coherent light generation unit, and changing the size of a light spot focused on the rotating ground glass to adjust the spatial coherence of a light source by adjusting the front and back positions of the lens for focusing on an optical axis;

(2) transmitting the partially coherent light to the object phase measuring unit, so that the partially coherent light passes through the object to be measured and records light intensity information:

(21) when the partial coherent light is Gaussian-associated partial coherent light, recording the light intensity twice, shooting for the first time, namely loading the object with the phase to be measured: setting the prepared picture as a gray scale image mode, and converting the gray scale value into a corresponding phase when the picture is loaded on the spatial light modulator with pure phase; second shooting, namely placing a disturbance point at any position of the object with the phase to be measured, wherein the size of the disturbance point is far smaller than that of the object with the phase to be measured, and the phase assignment of the disturbance point is different from that of the original object with the phase to be measured at the position; and (3) transmitting the light intensity information obtained by two times of shooting to a computer for processing: firstly, performing Fourier transform on two groups of light intensity information respectively, screening by a screening array, subtracting the screened results, and performing reverse transmission on the subtracted results to extract object phase information; the screening pores of the screening array are periodically arranged two-dimensional pores, and are generated by the computer, and the side length and the interval of each screening pore are consistent with those of the porous array plate;

(22) When the partial coherent light is Laguerre Gaussian related partial coherent light, recording four light intensities, shooting for the first time, and loading the object with the phase to be measured: setting the prepared picture as a gray scale image mode, and converting the gray scale value into a corresponding phase when the picture is loaded on the spatial light modulator with pure phase; second shooting, namely placing a disturbance point at any position of the object with the phase to be measured, wherein the size of the disturbance point is far smaller than that of the object with the phase to be measured, and the phase assignment of the disturbance point is different from that of the original object with the phase to be measured at the position; shooting for the third time, namely removing the object with the phase to be detected without removing the disturbance point, namely setting the phase of the area where the original object with the phase to be detected is located to be 0; fourth shooting-removing the disturbance phase; and (3) transmitting the light intensity information of two times obtained by the third shooting and the fourth shooting to a computer for processing: firstly, performing Fourier transform on two groups of light intensity information respectively, screening by a screening array, subtracting the screened results, and performing reverse transmission on the subtracted results to extract cross spectral density information and phase information of the light source; and (3) conveying the light intensity information of the two times obtained by the first shooting and the second shooting to a computer for processing: firstly, performing Fourier transform on two groups of light intensity information respectively, screening by a screening array, subtracting the screened results, and performing reverse transmission on the subtracted results to extract object phase information influenced by the light source phase; finally, the object phase influenced by the light source phase is used for removing the phase of the light source, so that correct object phase information can be obtained; the screening pores of the screening array are periodically arranged two-dimensional pores, and are generated by the computer, and the side length and the interval of each screening pore are consistent with those of the porous array plate.

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