阅读说明：本技术 一种空间分辨率可调的哈特曼波前传感器及波前复原方法 (Hartmann wavefront sensor with adjustable spatial resolution and wavefront restoration method ) 是由 于信 倪小龙 陈纯毅 刘智 董喆 于 2021-09-08 设计创作，主要内容包括：一种空间分辨率可调的哈特曼波前传感器及波前复原方法,属于光电检测领域,包括工控机；与工控机相连的焦距变换装置和光电探测装置,所述焦距变换装置的光轴方向平行于被测光束的法线方向；设置在焦距变换装置和光电探测装置之间的波前分割装置,光电探测装置的接收面位于波前分割装置的焦平面处；焦距变换装置收集被检测光束,通过波前分割装置聚焦于光电探测装置接收面上,同时在光电探测装置接收面上形成阵列光斑信息,通过工控机记录阵列光斑信息并计算出波前复原信息。本发明可根据被测光束的实际探测需求调节空间分辨率,进一步提升波前传感器的探测性能,能在大动态范围探测需求条件下提升测量精度,为高精度的波前探测提供了有力保障。(A Hartmann wavefront sensor with adjustable spatial resolution and a wavefront restoration method belong to the field of photoelectric detection and comprise an industrial personal computer; the optical axis direction of the focal length conversion device is parallel to the normal direction of the detected light beam; a wavefront dividing device disposed between the focal length converting device and the photodetecting device, a receiving surface of the photodetecting device being located at a focal plane of the wavefront dividing device; the focal length conversion device collects detected light beams, the detected light beams are focused on a receiving surface of the photoelectric detection device through the wavefront segmentation device, array light spot information is formed on the receiving surface of the photoelectric detection device, and the array light spot information is recorded through the industrial personal computer and wavefront restoration information is calculated. The invention can adjust the spatial resolution according to the actual detection requirement of the detected light beam, further improve the detection performance of the wavefront sensor, improve the measurement precision under the condition of the detection requirement of a large dynamic range, and provide powerful guarantee for high-precision wavefront detection.)

1. A hartmann wavefront sensor with adjustable spatial resolution, comprising:

an industrial personal computer (6);

the device comprises a focal length conversion device (1) and a photoelectric detection device (5) which are connected with an industrial personal computer (6), wherein the optical axis direction of the focal length conversion device (1) is parallel to the normal direction of a detected light beam;

a wavefront dividing device (4) arranged between the focal length transforming device (1) and the photodetection device (5), a receiving face of the photodetection device (5) being located at a focal plane of the wavefront dividing device (4);

the focal length conversion device (1) collects detected light beams, the detected light beams are focused on a receiving surface of the photoelectric detection device (5) through the wavefront dividing device (4), array light spot information is formed on the receiving surface of the photoelectric detection device (5), and the array light spot information is recorded through the industrial personal computer (6) and wavefront restoration information is calculated.

2. A hartmann wavefront sensor with adjustable spatial resolution according to claim 1, characterized in that the focal length transforming means (1) comprises: the device comprises a conjugate compensation device (7) connected with an industrial personal computer (6), and a first focal length free conversion device (2) and a second focal length free conversion device (3) which are arranged on the conjugate compensation device (7); the second focal length free transformation device (3) is arranged behind the first focal length free transformation device (2); and the conjugate compensation device (7) drives the first focal length free conversion device (2) and the second focal length free conversion device (3) to move along the direction of the optical axis.

3. Hartmann wavefront sensor with adjustable spatial resolution according to claim 2, characterised in that the focal length f of the first focal length free transformation means (2)₁A focal length f of the second focal length free-conversion device (3)₂Satisfies the following conditions:

(1) the optical distance L between the first focal length free-form changing device (2) and the second focal length free-form changing device (3) is f₁+f₂；

(2) Required multiplying power beta f of focal length conversion device (1)₂/f₁；

(3)f₁＝L/(1+β)，f₂＝βL/(1+β)。

4. The Hartmann wavefront sensor with adjustable spatial resolution of claim 2, characterized in that the first focal length free transformation device (2) and the second focal length free transformation device (3) constitute a magnification transformation optical system, and the magnification transformation optical system is in a Keplerian telescope structure or a Galileo telescope structure.

5. The Hartmann wavefront sensor with adjustable spatial resolution of claim 4, wherein when the requirement satisfies the conjugate detection, the magnification transformation optical system selects the Kepler telescope structure, the first focal length free transformation device (2) and the second focal length free transformation device (3) are both positive lenses, and the focal length f is₁、f₂Are all greater than zero(ii) a When no special requirement exists, the magnification conversion optical system selects a Galileo telescopic structure, the first focal length free conversion device (2) and the second focal length free conversion device (3) are both positive lenses, and the focal length f is₁Less than zero, focal length f₂Greater than zero.

6. The Hartmann wavefront sensor with adjustable spatial resolution of claim 2, characterized in that the first free focal length transformation device (2) adopts a liquid crystal spatial light modulator, a digital micromirror, a deformable mirror or a zoom optical lens group; the second free focal length conversion device (3) adopts a liquid crystal spatial light modulator, a digital micromirror, a deformable mirror or a zooming optical mirror group.

7. The Hartmann wavefront sensor with adjustable spatial resolution of claim 6, characterized in that the first focal length free transformation device (2) and the second focal length free transformation device (3) both adopt a liquid crystal spatial light modulator to realize focal length transformation, and the detected light beam is a rectangular square light spot with a size of D2 mm x2 mm; the phase diagrams of the first focal length free transformation device (2) and the second focal length free transformation device (3) satisfy the formula (1):

wherein, λ represents the wavelength of the measured light beam, f represents the focal length of the focal length conversion device (1),representing the surface type to be generated by the spatial light modulator, wherein x and y are coordinate values respectively; will f is₁、f₂And respectively substituting the obtained data into the formula (1) to obtain the surface shapes required to be generated by the first focal length free conversion device (2) and the second focal length free conversion device (3).

8. A method of wavefront reconstruction using the hartmann wavefront sensor with adjustable spatial resolution of any one of claims 1 to 7, comprising the steps of:

(1) the measured light beam forms a converged light beam through the first focal length free conversion device (2) to be converged at a focal point of the first focal length free conversion device (2), forms a divergent light beam when being continuously transmitted forwards through the focal point, transmits the divergent light beam to the second focal length free conversion device (3), enters the wavefront dividing device (4) to be divided into a plurality of sub-regions after being collimated by the second focal length free conversion device (3), and forms array light spots at a receiving surface of the photoelectric detection device (5);

(2) the interval between the focal length conversion device (1) and the wavefront dividing device (4) is adjusted by driving a conjugate compensation device (7) through an industrial personal computer (6);

(3) the photoelectric detection device (5) transmits the array light spot data at the receiving surface to the industrial personal computer (6), and the industrial personal computer (6) records and stores the array light spot data; the industrial personal computer (6) is in accordance with the formula (1) and the focal length f₁And focal length f₂Calculating a corresponding surface type by using a gray scale weighting method, calculating the centroid of the light spot according to a formula (2), calculating wavefront slope information according to centroid offset information and a formula (3), recovering the wavefront information by adopting a mode method-based recovery method, controlling a first focal length free conversion device (2) and a second focal length free conversion device (3) to generate corresponding surface types, and realizing focal length conversion of the first focal length free conversion device (2) and the second focal length free conversion device (3);

wherein, I_ijRepresenting the light intensity, x, of the (i, j) th pixel on the receiving surface of the photo detection means (5)_ij、y_ijRespectively represent the coordinates, x, of the (i, j) th pixel_c、y_cRespectively representing the centroid positions of the reference beams forming the light spots in the sub-apertures;

wherein L is_k(x, y) represents the kth Legendre polynomial, and l represents the number of terms of the Legendre polynomial used in wavefront restoration; f represents the focal length of the focal length conversion device (1); a is_kCoefficients representing the Legendre polynomial of the kth term; g_x(i) Denotes the slope in the X direction, g_y(i) Denotes the slope in the Y direction, s denotes the number of sub-apertures, ax denotes the X-direction centroid shift, ay denotes the Y-direction centroid shift,the calculus is represented.

9. The method for wavefront restoration implemented by the Hartmann wavefront sensor with adjustable spatial resolution as claimed in claim 8, wherein in the step (2), the movement direction of the conjugate compensation device (7) is parallel to the optical axis transmission direction, and the adjustment amount is the focal length f of the second focal length free transformation device (3) before zooming₂And the focal length f of the second focal length free conversion device (3) after zooming₂The difference of' i.e. f₂ˊ-f₂(ii) a When the difference is positive, the optical axis transmission direction is adjusted reversely, so that the conjugate compensation device (7) is far away from the wavefront dividing device (4); when the difference is negative, the optical axis transmission direction is adjusted in the same direction so that the conjugate compensation means (7) approaches the wavefront dividing means (4).

10. The method for wavefront reconstruction implemented by a hartmann wavefront sensor with adjustable spatial resolution as claimed in claim 8, wherein in step (3), the wavefront information is reconstructed by a reconstruction method based on a pattern method, and the calculation process of the wavefront slope information of the pattern method is as follows:

G＝L·A (4)

the column vector G is the wave front slope information of the M sub-apertures in the X and Y directions; l represents a reconstruction matrix when wavefront reconstruction is carried out by adopting a mode method; a represents a mode coefficient;

and obtaining a minimum norm solution by using a least square fitting mode:

A＝L⁺·G (5)

wherein L is⁺For the generalized inverse of matrix L, the wavefront slope φ (x, y) is obtained by substituting the coefficients into equation (6):

wherein, a_kCoefficients representing the Legendre polynomial of the k-th term.

Technical Field

The invention belongs to the technical field of photoelectric detection, and particularly relates to a Hartmann wavefront sensor with adjustable spatial resolution and a wavefront restoration method.

Background

The Hartmann wavefront sensor has the advantages of compact structure, strong anti-interference capability, high light energy utilization rate and the like, and is widely applied to the fields of adaptive optics, optical detection, photoelectric detection and the like.

Chinese patent publication No. CN1245904 discloses a classical structural form of a hartmann wavefront sensor, which adopts optical elements such as a microlens array to spatially divide the wavefront of an incident light wave, divide the wavefront into a plurality of sub-regions, focus the light beam of each sub-region on the receiving surface of a photodetector, form a series of array light spots on the receiving surface, analyze and process the variation information of the centroid of the array light spots, and combine with a corresponding recovery algorithm, thereby obtaining the wavefront information of the measured light beam. The wavefront sensor with the structure has the advantage of calibrating the systematic error, so that the wavefront sensor is favored in practical engineering application. On the premise of large dynamic range requirement, research work on how to improve the detection accuracy of the Hartmann wavefront sensor becomes a research hotspot.

The factors influencing the detection accuracy of the Hartmann wavefront sensor mainly comprise: information extraction, recovery algorithm and structure form. In the aspect of information extraction, accurate extraction of spot centroid change information is a guarantee for realizing high-precision wavefront restoration, so that the wavefront detection precision can be improved by improving the precision of centroid calculation, for example, a high-precision centroid detection method of a hartmann shack wavefront sensor (li crystal, consolidation, etc. [ J ]. china laser, 2014,41 (3)). In the aspect of wavefront reconstruction, the wavefront information of the measured light beam is accurately reconstructed according to the information provided by the centroid calculation, so that the accuracy can be effectively improved by improving and optimizing the algorithm of wavefront reconstruction, for example, the wavefront reconstruction method for improving the measurement accuracy of the shack-hartmann wavefront sensor disclosed in the chinese patent with the publication number CN 102749143A. From the aspect of the structural form, the number of the wave-front segmentation subregions can be increased in a mode of improving the spatial resolution, and the precision of wave-front detection is improved. Although the accuracy of wavefront reconstruction can be further improved by optimizing the means of information extraction and the wavefront reconstruction algorithm, the spatial resolution is always a precondition for wavefront detection. When the wave front is restored by adopting the mode method, no matter in the aspect of information extraction or in the aspect of wave front restoration, the measured wave front can not be restored by adopting the Zernike polynomials of different orders. And the adoption of enough orders is the guarantee for perfectly restoring the measured wavefront. For example, when the measured light beam includes 35-order high-order aberration and the spatial resolution is only 2 × 2, under the condition of such spatial resolution, only the recovery of the low-order aberration component (the first 7-order) can be realized, and the high-order term of 35-order cannot be reflected, under such condition, the accuracy cannot be improved in either the information extraction aspect or the wavefront recovery algorithm aspect, and only the spatial resolution can be improved. When the spatial resolution is improved to 10 × 10, the restoration of 65-order aberration can be realized, and on the premise of the spatial resolution, the method of optimizing information extraction and the wavefront reconstruction algorithm is more meaningful.

However, a method for effectively adjusting the spatial resolution of the wavefront sensor is lacking, and therefore, there is an urgent need to develop a hartmann wavefront sensor that can still further improve the accuracy of wavefront detection under the condition of a large dynamic range.

Disclosure of Invention

In order to solve the problem of how to improve the detection precision of the Hartmann wavefront sensor under the condition of a large dynamic range, the invention provides the Hartmann wavefront sensor with adjustable spatial resolution and a wavefront restoration method.

The technical scheme adopted by the invention for solving the technical problem is as follows:

the invention relates to a Hartmann wavefront sensor with adjustable spatial resolution, which comprises:

an industrial personal computer;

the optical axis direction of the focal length conversion device is parallel to the normal direction of the detected light beam;

a wavefront dividing means disposed between the focal length converting means and the photodetecting means, a receiving face of the photodetecting means being located at a focal plane of the wavefront dividing means;

the focal length conversion device collects detected light beams, the detected light beams are focused on a receiving surface of the photoelectric detection device through the wavefront segmentation device, array light spot information is formed on the receiving surface of the photoelectric detection device, and the array light spot information is recorded through the industrial personal computer and wavefront restoration information is calculated.

Further, the focal length conversion device includes: the device comprises a conjugate compensation device connected with an industrial personal computer, a first focal length free conversion device and a second focal length free conversion device, wherein the first focal length free conversion device and the second focal length free conversion device are arranged on the conjugate compensation device; the second focal length free transformation device is arranged behind the first focal length free transformation device; the conjugate compensation device drives the first focal length free conversion device and the second focal length free conversion device to move along the direction of the optical axis.

Further, the focal length f of the first focal length free transformation device₁Focal length f of the free conversion device with the second focal length₂Satisfies the following conditions:

(1) the optical distance between the first focal length free conversion device and the second focal length free conversion device is equal to f₁+f₂；

(2) Multiplying power beta f needed by focal length changing device 1₂/f₁；

(3)f₁＝L/(1+β)，f₂＝βL/(1+β)。

Furthermore, the first focal length free conversion device and the second focal length free conversion device form a magnification conversion optical system, and the structural form of the magnification conversion optical system is a Keplerian telescope structure or a Galileo telescope structure.

Further, when the requirement meets the conjugated detection, the multiplying power conversion optical system selects a Kepler type telescopic structure, the first focal length free conversion device and the second focal length free conversion device are both positive lenses, and the focal length f is₁、f₂Are all larger than zero; when no special requirement exists, the magnification conversion optical system selects a Galileo telescopic structure, the first focal length free conversion device and the second focal length free conversion device are both positive lenses, and the focal length f₁Is less thanZero, focal length f₂Greater than zero.

Furthermore, the first focal length free transformation device adopts a liquid crystal spatial light modulator, a digital micromirror, a deformable mirror or a zooming optical mirror group; the second focal length free transformation device adopts a liquid crystal spatial light modulator, a digital micromirror, a deformable mirror or a zooming optical mirror group.

Further, the first focal length free transformation device and the second focal length free transformation device both adopt a liquid crystal spatial light modulator to realize focal length transformation, detected light beams are rectangular square light spots, and the size D is 2mm multiplied by 2 mm; the phase diagrams of the first focal length free transformation device and the second focal length free transformation device satisfy formula (1):

wherein, λ represents the wavelength of the measured light beam, f represents the focal length of the focal length conversion device,representing the surface type to be generated by the spatial light modulator, wherein x and y are coordinate values respectively; will f is₁、f₂And (3) respectively substituting the two into the formula (1) to obtain the surface shapes required to be generated by the first focal length free conversion device and the second focal length free conversion device.

The invention discloses a wavefront restoration method realized by a Hartmann wavefront sensor with adjustable spatial resolution, which comprises the following steps:

(1) the measured light beam forms a converged light beam through the first focal length free conversion device, converges at the focal point of the first focal length free conversion device, forms a divergent light beam when continuously transmitted forwards through the focal point, transmits the divergent light beam to the second focal length free conversion device, enters the wavefront dividing device after being collimated by the second focal length free conversion device, is divided into a plurality of sub-regions, and forms array light spots at the receiving surface of the photoelectric detection device;

(2) the interval between the focal length conversion device and the wavefront segmentation device is adjusted by driving the conjugate compensation device through the industrial personal computer;

(3) the photoelectric detection device transmits the array light spot data at the receiving surface to an industrial personal computer, and the industrial personal computer records and stores the array light spot data; the industrial personal computer is according to formula (1) and focal length f₁And focal length f₂Calculating a corresponding surface type by using a gray scale weighting method, calculating the centroid of the light spot according to a formula (2), calculating wavefront slope information according to centroid offset information and a formula (3), recovering the wavefront information by adopting a mode method-based recovery method, controlling a first focal length free conversion device and a second focal length free conversion device to generate corresponding surface types, and realizing focal length conversion of the first focal length free conversion device and the second focal length free conversion device;

wherein, I_ijRepresenting the light intensity, x, of the (i, j) th pixel on the receiving surface of the photo detection means_ij、y_ijRespectively represent the coordinates, x, of the (i, j) th pixel_c、y_cRespectively representing the centroid positions of the reference beams forming the light spots in the sub-apertures;

wherein L is_k(x, y) represents the kth Legendre polynomial, and l represents the number of terms of the Legendre polynomial used in wavefront restoration; f represents the focal length of the focal length conversion device; a is_kCoefficients representing the Legendre polynomial of the kth term; g_x(i) Denotes the slope in the X direction, g_y(i) Denotes the slope in the Y direction, s denotes the number of sub-apertures, ax denotes the X-direction centroid shift, ay denotes the Y-direction centroid shift,the calculus is represented.

Further, in step (2), the moving direction of the conjugate compensation device and the optical axis transmission directionParallel to the focal length f of the second focal length free conversion device before zooming₂And the focal length f of the second focal length free conversion device after zooming₂The difference of' i.e. f₂ˊ-f₂(ii) a When the difference is positive, the optical axis transmission direction is adjusted reversely, so that the conjugate compensation device is far away from the wavefront dividing device; when the difference is negative, the optical axis transmission direction is adjusted in the same direction, so that the conjugate compensation device approaches the wavefront dividing device.

Further, in the step (3), the wavefront information is restored by using a restoration method based on a mode method, and the calculation process of the wavefront slope information of the mode method is as follows:

G＝L·A (4)

the column vector G is the wave front slope information of the M sub-apertures in the X and Y directions; l represents a reconstruction matrix when wavefront reconstruction is carried out by adopting a mode method; a represents a mode coefficient;

and obtaining a minimum norm solution by using a least square fitting mode:

A＝L⁺·G (5)

wherein L is⁺For the generalized inverse of matrix L, the wavefront slope φ (x, y) is obtained by substituting the coefficients into equation (6):

wherein, a_kCoefficients representing the Legendre polynomial of the k-th term.

The invention has the beneficial effects that:

although the accuracy of wavefront reconstruction can be further improved by optimizing the means of information extraction and the algorithm of wavefront reconstruction, the spatial resolution is always a precondition for wavefront detection. For example: when the number of subapertures of the wavefront dividing device 4 is 2 × 2, when the wavefront reconstruction is performed by the mode method, only the low-order aberration (first 5-order aberration) component can be reconstructed, and the high-order aberration component cannot be detected. At this time, when the number of sub-apertures of the wavefront dividing device 4 is 9 × 9, more detailed information about the incident wavefront can be obtained, the aberration order that can be recovered is increased to 65 orders, and the reconstructed wavefront surface type is more practical. Therefore, the expected effect of improving the reconstruction precision can be achieved only by optimizing the information extraction means and the wavefront reconstruction algorithm on the premise that the spatial resolution meets the requirement. In addition, when wave front detection is required to be carried out on light beams with different apertures, the spatial resolution of the traditional Hartmann wave front sensor is reduced along with the reduction of the apertures, so that the accuracy of wave front detection is reduced.

In summary, the present invention provides a hartmann wavefront sensor with adjustable spatial resolution and a wavefront restoration method, and the hartmann wavefront sensor with adjustable spatial resolution can adjust the spatial resolution according to the actual detection requirement of the detected light beam, thereby further improving the detection performance of the wavefront sensor.

In the invention, the focal length conversion device is a device with adjustable focal length and capable of compensating defocusing aberration, wherein the first focal length free conversion device and the second focal length free conversion device can realize focal length conversion and also play a role in eliminating aberration and ensuring the beam quality of a system in the process of magnification conversion. The magnification of the magnification conversion optical system is adjusted through the focal length conversion device, the number of effective sub-apertures of the wavefront dividing device is controlled, the spatial resolution is adjusted, and the measurement precision can still be improved under the condition of large dynamic range detection requirements.

In the invention, the wavefront dividing device is positioned between the focal length conversion device and the photoelectric detection device, and can focus the mapping light beam on the receiving surface of the photoelectric detection device, form array light spot information on the receiving surface of the photoelectric detection device, and further reconstruct the wavefront information of the detected light beam according to the change information of the array light spot.

The invention adopts the Hartmann wavefront sensor with adjustable spatial resolution to detect, can realize higher spatial resolution through magnification transformation even under the condition that the size of the detected light beam is smaller, and provides powerful guarantee for high-precision wavefront detection.

The wave front restoration method realized by the Hartmann wave front sensor with adjustable spatial resolution improves the spatial resolution and improves the wave front detection precision under the condition of large dynamic range detection requirement.

Drawings

Fig. 1 is a schematic structural diagram of a hartmann wavefront sensor with adjustable spatial resolution according to the present invention.

Fig. 2 is a schematic view of an optical structure of the focal length conversion device.

Fig. 3 is a schematic diagram of a wavefront dividing apparatus according to the first embodiment, when β is 2 ×.

Fig. 4 is a residual map (RMS 0.022 μm) of wavefront reconstruction when β is 2 ×, according to the first embodiment.

Fig. 5 is a schematic diagram illustrating matching of the wavefront dividing apparatus when β is 4x in the second embodiment.

Fig. 6 is a residual map (RMS 0.01 μm) of wavefront reconstruction when β is 4 × in embodiment two.

In the figure, the device comprises a focal length conversion device 1, a focal length conversion device 2, a first focal length free conversion device 3, a second focal length free conversion device 4, a wavefront division device 5, a photoelectric detection device 6, an industrial personal computer 7 and a conjugate compensation device.

Detailed Description

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

As shown in fig. 1, a hartmann wavefront sensor with adjustable spatial resolution of the present invention mainly includes: the device comprises a focal length conversion device 1, a wavefront dividing device 4, a photoelectric detection device 5 and an industrial personal computer 6.

The focal length conversion device 1 is connected with an industrial personal computer 6 through a data line. The focal length conversion device 1 is arranged at the forefront of the system, the optical axis direction of the focal length conversion device 1 is parallel to the normal direction of the measured light beam, and the optical axis of the focal length conversion device 1 is perpendicular to the wavefront dividing device 4 and the photoelectric detection device 5. The focal length conversion device 1 can match the aperture of the light source to be detected with the size of the wavefront dividing device 4. The focal length conversion device 1 is used for collecting the detected light beam, performing size conversion on the detected light beam, adjusting the coverage area of the detected light beam mapped on the wavefront dividing device 4, and changing the number of effective sub-apertures of the wavefront dividing device 4, thereby changing the spatial resolution.

The focal length conversion device 1 mainly comprises a first focal length free conversion device 2, a second focal length free conversion device 3 and a conjugate compensation device 7. The first focal length free transformation device 2 and the second focal length free transformation device 3 are both arranged on the conjugate compensation device 7. The second focal length free conversion device 3 is arranged behind the first focal length free conversion device 2, namely the first focal length free conversion device 2 is arranged at the front end of the second focal length free conversion device 3, and the optical interval between the first focal length free conversion device 2 and the second focal length free conversion device 3 is L.

In the focal length conversion device 1, the focal length f of the first focal length free conversion device 2₁And a focal length f of the second focal length free conversion means 3₂The following geometrical relationships are satisfied:

(1) the optical interval of the focal length conversion device 1 is L ═ f₁+f₂；

(2) The required multiplying power of the focal length conversion device 1 is beta ═ f₂/f₁；

(3) Focal length f of the first focal length free transformation device 2₁L/(1+ β), the focal length f of the second focal length free transformation means 3₂＝βL/(1+β)。

The first focal length free conversion device 2 and the second focal length free conversion device 3 form a magnification conversion optical system, the structural form of the magnification conversion optical system can be a Keplerian telescope structure or a Galileo telescope structure, the magnification conversion optical system can be arbitrarily converted according to the use requirement, and the beam quality of the system can be guaranteed. When the conjugate detection is required, a keplerian telescope structure is selected, as shown in fig. 2 (a), and at this time, the first focal length free transformation device 2 and the second focal length free transformation device 3 are both positive lenses, and the focal length f is₁、f₂Are all greater than zero. When there is no special requirement, a Galileo telescopic structure is selected, as shown in (b) of FIG. 2, and at this time, the first focal length free transformation device 2 and the second focal length free transformation device 3 are both positive lenses, and the focal length f is₁Is less thanZero, focal length f₂Greater than zero.

The first focal length free conversion device 2 and the second focal length free conversion device 3 can be selected from liquid crystal spatial light modulators, digital micro-mirrors, deformable mirrors, zooming optical lens groups and other devices with functions of zooming and eliminating aberration.

In the present embodiment, in order to meet the requirement of adaptive optical conjugate correction, the magnification conversion optical system including the first and second free focal length conversion devices 2 and 3 has a keplerian telescope structure capable of performing an image transfer function.

In the present embodiment, the optical distance L between the first and second focal length conversion devices 2 and 3 is 30mm, and the focal length of the first focal length conversion device 2 is f₁10mm, the focal length f of the second focal length free transformation device 3₂＝β×f₁. The focal length of the first focal length free conversion device 2 is larger than that of the second focal length free conversion device 3, and the image of the object is amplified in the image transmission process so as to meet the requirement of spatial resolution.

In this embodiment, the first focal length free transformation device 2 and the second focal length free transformation device 3 both use the liquid crystal spatial light modulator to realize focal length transformation, and can eliminate defocusing aberration, and the detected beam size is: d is a 2mm × 2mm rectangular square spot. When the first focal length free transformation device 2 and the second focal length free transformation device 3 both use the liquid crystal spatial light modulator, the phase diagram thereof satisfies the relationship shown in the formula (1):

wherein λ represents the wavelength of the measured light beam, f represents the focal length of the focal length conversion device 1,representing the shape of the surface to be generated by the spatial light modulator, x, y being coordinate values, respectively. Will f is₁、f₂Respectively, into the formula (1), the first focal length free transformation device 2 and the second focal length free transformation deviceThe second focal length is free of the face shape that the device 3 needs to produce.

The conjugate compensation device 7 is connected with the industrial personal computer 6 through a data line. The conjugate compensation device 7 can drive the first focal length free conversion device 2 and the second focal length free conversion device 3 to move along the optical axis direction, and the movement amount is approximately equal to the difference value of the front focal length and the back focal length of the second focal length free conversion device 3.

The conjugate compensation device 7 is used for adjusting the distance between the second focal length free transformation device 3 and the wavefront dividing device 4, can ensure the conjugate relation between the detected plane and the wavefront dividing plane, and meets the special requirements of the adaptive optical correction system.

The conjugate compensation device 7 can be a mechanism with a linear displacement adjustment function driven by a motor, piezoelectric ceramics and the like.

In the present embodiment, the conjugate compensation device 7 is a linear displacement platform driven by piezoelectric ceramics, and the stroke thereof is 30 mm.

The wavefront dividing device 4 is arranged behind the second focal length free transformation device 3, the wavefront dividing device 4 is arranged in front of the photoelectric detection device 5, the wavefront dividing device 4 is used for receiving the light beam output by the focal length transformation device 1, the wavefront dividing device 4 divides the transformed light beam into a plurality of sub-areas in space, and the light beam in the divided sub-areas is imaged on the receiving surface of the photoelectric detection device 5.

The normal direction of the sub-wavefront of the wavefront dividing device 4 is kept consistent with the optical axis direction of the focal length conversion device 1, the whole size of the wavefront dividing device 4 is larger than the aperture of the detected light source, and the whole size of the wavefront dividing device 4 is matched with the size of the receiving surface of the photoelectric detection device 5.

The wavefront dividing means 4 may employ a continuous surface microlens array, a binary fresnel microlens array, or a gradient index microlens array.

In this embodiment, the wavefront dividing device 4 specifically uses a continuous surface microlens array, the size of a single sub-aperture is 0.5mm × 0.5mm, the overall size is 15mm × 15mm, and the focal length is 30 mm.

In this embodiment, the wavefront dividing device 4 is coated with antireflection films on both sides, so that the energy utilization rate is improved.

The photoelectric detection device 5 is connected with the industrial personal computer 6 through a data line. The receiving face of the photodetection device 5 is located at the focal plane of the wavefront dividing device 4. The size of the receiving face of the photodetection device 5 matches the size of the whole wavefront dividing device 4. The photoelectric detection device 5 receives the image spot information in the sub-region divided by the wavefront dividing device 4, records the change information of the image spot of the sub-region, and further reconstructs the wavefront aberration of the measured light beam by adopting a corresponding reconstruction algorithm.

The photoelectric detection device 5 can be a four-quadrant sensor, a CCD detector, a CMOS detector or other photoelectric conversion devices.

In this embodiment, the photoelectric detection device 5 specifically uses a CCD detector, the resolution of the receiving surface is 1024 × 1024, the pixel size is 14 μm, and the receiving surface size is 14.336mm × 14.336 mm.

The invention discloses a method for realizing wavefront recovery of a measured light beam by utilizing a Hartmann wavefront sensor with adjustable spatial resolution, which comprises the following specific processes:

1. the measured light beam forms a converged light beam through the first focal length free conversion device 2, the converged light beam converges at the focus of the first focal length free conversion device 2, a divergent light beam is formed when the divergent light beam continuously forwards transmits through the focus, the divergent light beam transmits to the second focal length free conversion device 3 to be collimated, enters the wavefront dividing device 4 after being collimated by the second focal length free conversion device 3, is divided into a plurality of sub-regions after passing through the wavefront dividing device 4, and an array light spot is formed at the receiving surface of the photoelectric detection device 5.

The focal length conversion device 1 adjusts the focal length f of the first focal length free conversion device 2₁And a focal length f of the second focal length free conversion means 3₂Changing the magnification beta to change the area of the spot mapped on the wavefront dividing device 4 by beta²Doubling, increasing the number of subapertures to the original (. beta.)²-1) times.

2. The interval between the focal length conversion device 1 and the wavefront dividing device 4 is adjusted by driving the conjugate compensation device 7 through the industrial personal computer 6 so as to meet the requirement of conjugate detection. The direction of movement of the conjugate compensation means 7 is parallel to the direction of optical axis transport, the amount of adjustment thereofIs the focal length f of the second focal length free conversion device 3 before zooming₂And the focal length f of the second focal length free conversion device 3 after zooming₂The difference between the two, i.e. f₂ˊ-f₂(ii) a When the difference is positive, the adjustment is performed in the direction opposite to the optical axis transmission direction, so that the conjugate compensation device 7 is away from the wavefront dividing device 4; when the difference is negative, adjustment is made in the same direction as the optical axis transmission direction so that the conjugate compensation means 7 approaches the wavefront dividing means 4.

3. And finally, the photoelectric detection device 5 transmits the array light spot data at the receiving surface, namely the light intensity information of the array light spots, to the industrial personal computer 6 through a data line, and the array light spot data is recorded and stored through the industrial personal computer 6. The industrial personal computer 6 is in accordance with the relation and the focal length f in the formula (1)₁And focal length f₂According to the requirements and the stored array light spot data, a corresponding surface type is calculated by using a gray scale weighting method, meanwhile, the center of mass of the light spot is calculated according to a formula (2), wavefront slope information is calculated according to a formula (3), a restoring method based on a mode method is adopted to restore the wavefront information, the first focal length free conversion device 2 and the second focal length free conversion device 3 are controlled to generate the corresponding surface type, and focal length conversion of the first focal length free conversion device 2 and the second focal length free conversion device 3 is realized.

Wherein, I_ijRepresenting the light intensity, x, of the (i, j) th pixel on the receiving surface of the photo detection means 5_ij、y_ijRespectively represent the coordinates, x, of the (i, j) th pixel_c、y_cRespectively, the centroid positions of the reference beam forming spots at the sub-apertures.

And calculating wavefront slope information according to formula (3) according to the information of the centroid shift.

Wherein L is_k(x, y) denotes the Legendre polynomial of the k-th term, l denotes the wavefrontThe number of terms of the Legendre polynomial used in the recovery. f denotes the focal length of the focal length conversion device 1. a is_kCoefficients representing the Legendre polynomial of the k-th term. g_x(i) The slope in the X direction is shown. g_y(i) Indicating the slope in the Y direction. s represents the number of subapertures. Δ X denotes the X-direction centroid displacement. Δ Y represents the Y-direction centroid offset.The calculus is represented.

The method comprises the following steps of restoring wavefront information by adopting a restoration method based on a mode method, wherein the calculation process of wavefront slope information of the mode method is as follows:

G＝L·A (4)

the column vector G is the wave front slope information of the M sub-apertures in the X and Y directions; l represents a reconstruction matrix when wavefront reconstruction is carried out by adopting a mode method; a represents a mode coefficient. By using least squares fit, the minimum norm solution can be obtained:

A＝L⁺·G (5)

wherein L is⁺The coefficient is substituted into the formula (6) as a generalized inverse matrix of the matrix L, and the wavefront slope phi (x, y) can be obtained:

wherein, a_kCoefficients representing the Legendre polynomial of the k-th term.

Detailed description of the invention

Assuming that the magnification required by the focal length conversion device 1 is β 2x, the focal length f of the first focal length free conversion device 2₁10mm, the focal length f of the second focal length free transformation means 3₂20 mm. At this time, the matching relationship between the mapped spot size and the wavefront dividing device 4 is shown in fig. 3, and the number of effective sub-apertures is: 8x 8. By adopting the restoration method of the invention, the wavefront aberration information detected by the photoelectric detection device 5 is subtracted from the aberration actually contained in the detected light beam, and the residual error map of wavefront reconstruction is obtained as shown in fig. 4RMS (root mean square value) after recovery was 0.022 μm. The wavefront restoration residual error is smaller, which shows that the wavefront restoration residual error is closer to a theoretical value, and the measurement precision is higher.

Detailed description of the invention

Assuming that the magnification required by the focal length conversion device 1 is β 3 ×, the focal length f of the first focal length free conversion device 2₁10mm, the focal length f of the second focal length free transformation means 3₂30 mm. At this time, the matching relationship between the mapped spot size and the wavefront dividing device 4 is shown in fig. 5, and the number of effective sub-apertures is: 12x 12. With the restoration method of the present invention, the wavefront aberration information detected by the photodetection device 5 is subtracted from the aberration actually contained in the measured beam, and the reconstructed wavefront residual map is obtained as shown in fig. 6, where the RMS (root mean square value) after restoration is 0.01 μm. The wavefront restoration residual error is smaller, which shows that the wavefront restoration residual error is closer to a theoretical value, and the measurement precision is higher.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.