ANISOPLANATIC ABERRATION CORRECTION METHOD AND APPARATUS FOR ADAPTIVE OPTICAL BIAXIAL SCANNING IMAGING

Abstract

An anisoplanatic aberration correction method and apparatus for adaptive optical biaxial scanning imaging are provided. Insofar as no adaptive optical wavefront sensor and wavefront corrector are added, an anisoplanatic aberration of biaxial scanning is divided into a plurality of isoplanatic sub-fields of view by means of a time-sharing method and according to a beam scanning trajectory; aberration measurement and closed-loop correction are respectively completed in each isoplanatic region sub-field of view, and a residual aberration of a formed image of each isoplanatic region sub-field of view is also supplementally corrected on the basis of an image processing technology, thereby realizing complete correction of an anisoplanatic aberration of a wide field of view. The aberration correction of a wide field of view can be completed only by a single wavefront sensor and a single wavefront corrector, so that the limitation of an isoplanatic region to an adaptive optical imaging field of view can be broken through, the aberration correction and high-resolution imaging of a wide field of view of a retina are realized, almost none of the system complexities is increased, and the method and the apparatus have extremely high practicability. The correction of an image subjected to deconvolution is low in cost, and the correction effect is good.

Claims

1. An anisoplanatic aberration correction method for adaptive optical biaxial scanning imaging, wherein, in the adaptive optical biaxial scanning imaging, biaxial scanning comprises an X direction and a Y direction; the method comprises the following steps: step S1: dividing an entire anisoplanatic imaging field of view of the biaxial scanning into a plurality of sub-regions according to a scanning trajectory, the sub-regions including sub-region 11, sub-region 12, . . . , sub-region 1N, sub-region 21, sub-region 22, . . . , sub-region MN, wherein a field of view of each sub-region does not exceed 2° both in the X direction of scanning and in the Y direction of scanning, and all the sub-regions satisfy the principle of an isoplanatic region; M and N are positive integers; step S2: measuring an aberration of each isoplanatic sub-region by a wavefront sensor in sequence, and performing feedback in sequence to control a wavefront corrector to complete closed-loop correction of the aberration of each isoplanatic sub-region in sequence; step S3: converting a wavefront aberration of each sub-region measured by the wavefront sensor to obtain a point spread function (PSF) of each sub-region, taking the PSF of each sub-region as a PSF initial value and constraint condition of a formed image of each sub-region, and respectively completing deconvolution processing of the formed image of each sub-region by means of Wiener filtering, so as to supplementally correct a residual aberration of the formed image of each sub-region; and step S4: after the deconvolution correction of the formed images of all the sub-regions is completed, stitching the images to obtain a formed image of a wide field of view with M×N sub-regions, the anisoplanatic aberration of which is completely corrected.

2. The anisoplanatic aberration correction method for the adaptive optical biaxial scanning imaging according to claim 1, wherein, in step S1, each sub-region may be uniformly and equally divided, or may be non-uniformly divided.

3. The anisoplanatic aberration correction method for the adaptive optical biaxial scanning imaging according to claim 1, wherein step S3 specifically comprises: S3-1: performing calculation on a wavefront W.sub.i,j(ξ,η), 1≤i≤M, 1≤j≤N of each sub-region measured by the wavefront sensor to obtain a PSF h.sub.i,j(x,y), 1≤i≤M, 1≤j≤N of each sub-region, wherein $h_{i,j}\left(x,y\right)={.Math.\int \int P_{i,j}\left(\xi ,\eta \right)\exp \left({\mathrm{jkW}}_{i,j}\left(\xi ,\eta \right)\right)\exp \left(-j\frac{k}{f}\left[\left(x\xi +y\eta \right)\right]\right)d\xi d\eta .Math.}_2^2$ P.sub.i,j(ξ,η) is a pupil function of a sub-lens of the wavefront sensor; f is a focal length of the sub-lens; k is a wave number constant; and S3-2: taking the PSF of each sub-region as a PSF initial value and constraint condition of a formed image of each sub-region, and respectively completing deconvolution processing of the formed image of each sub-region by means of the following iterative formula for incremental Wiener filtering, so as to supplementally correct a residual aberration of the formed image of each sub-region, ${i,j}_{\mathrm{new}}^{}\left(u,v\right)={i,j}_{\mathrm{old}}^{}\left(u,v\right)+\frac{{i,j}_{*}^{}\left(u,v\right)S\left(u,v\right)}{{.Math.{i,j}_{}\left(u,v\right).Math.}^2+{\gamma }_x};{i,j}_{\mathrm{new}}^{}\left(u,v\right)={i,j}_{\mathrm{old}}^{}\left(u,v\right)+\frac{{i,j}_{*}^{}\left(u,v\right)S\left(u,v\right)}{{.Math.{i,j}_{}\left(u,v\right).Math.}^2+{\gamma }_h};S\left(u,v\right)=Y\left(u,,v\right)-{i,j}_{}\left(u,v\right){i,j}_{}\left(u,v\right);$ wherein * represents a complex conjugate operator; i and j represent the serial number of each sub-region; Y.sub.i,j(u,v) represents Fourier transformation of the formed image of the sub-region; .sub.i,j.sup.new(u,v) and .sub.i,j.sup.old(u,v) respectively represents Fourier transformations, iterated in the current deconvolution and the previous deconvolution, of the formed image of the sub-region; .sub.i,j.sup.new(u,v) and .sub.i,j.sup.old(u,v) respectively represent Fourier transformations, iterated in the current deconvolution and the previous deconvolution, of a PSF estimate of the sub-region; S(u,v) is a precision term; as values of .sub.i,j.sup.new(u,v) and .sub.i,j.sup.new(u,v) are updated, the value of S(u,v) is updated timely; γ.sub.x and γ.sub.h are parameters for controlling an iteration step size; if the values of γ.sub.x and γ.sub.h are larger, the iteration step size is smaller, converging of the algorithm would be slower, and a solution thereof would be more accurate; and if the values of γ.sub.x and γ.sub.h decrease, the iteration step size increases, and the algorithm would converge faster into an unsmoothed solution.

4. The anisoplanatic aberration correction method for the adaptive optical biaxial scanning imaging according to claim 3, wherein in step S3-2, the values of γ.sub.x and γ.sub.h are selected as: γ.sub.h=0.2|Ĥ(0,0)|.sup.2, γ.sub.x=0.2|{circumflex over (X)}(0,0)|.sup.2.

5. The anisoplanatic aberration correction method for the adaptive optical biaxial scanning imaging according to claim 3, wherein step S3 is carried out online or offline.

6. An anisoplanatic aberration correction apparatus for adaptive optical biaxial scanning imaging, wherein the apparatus is configured to adopt the method according to claim 1 to achieve anisoplanatic aberration correction for adaptive optical biaxial scanning imaging.

7. The anisoplanatic aberration correction apparatus for the adaptive optical biaxial scanning imaging according to claim 6, wherein the apparatus comprises a light source and beam transformation system, a biaxial scanning system, an adaptive optical system, a beam collection system and a data processing system; the light source and beam transformation system comprises an imaging light source used for illumination imaging, a beacon light source used for aberration measurement, and an optical element used for transforming beams emitted by the imaging light source and the beacon light source; the biaxial scanning system comprises a scanning device capable of realizing beam scanning both in an X direction and in a Y direction; a scanning trajectory of the biaxial scanning system is configured to first scan the sub-regions along the X direction and then scan the sub-regions along the Y direction, or is configured to first scan the sub-regions along the Y direction and then scan the sub-regions along the X direction.

8. The anisoplanatic aberration correction apparatus for the adaptive optical biaxial scanning imaging according to claim 7, wherein the adaptive optical system comprises a wavefront sensor, a wavefront corrector and a wavefront processor; the wavefront sensor is configured to measure a wavefront aberration and output the wavefront aberration to the wavefront processor; the wavefront processor is configured to solve the wavefront aberration into a wavefront control quantity, and perform feedback according to a scanning synchronization signal of the biaxial scanning system to control the wavefront corrector to generate phase compensation, so as to realize closed-loop correction of the wavefront aberration.

9. The anisoplanatic aberration correction apparatus for the adaptive optical biaxial scanning imaging according to claim 8, wherein the beam collection system comprises an optical element used for completing focusing of imaging beams, and a detector for achieving photoelectric conversion.

10. The anisoplanatic aberration correction apparatus for the adaptive optical biaxial scanning imaging according to claim 9, wherein the data processing system is a digital processor or a computer; and the data processing system is configured to complete, according to the scanning synchronization signal of the biaxial scanning system, image deconvolution on all the sub-regions on the scanning trajectory and image stitching on all the sub-regions having been subjected to the image deconvolution.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is a schematic diagram of an anisoplanatic aberration correction method for adaptive optical biaxial scanning imaging in Embodiment 1 of the present application;

[0031] FIG. 2 is a schematic diagram of an anisoplanatic aberration correction apparatus for adaptive optical biaxial scanning imaging in Embodiment 2 of the present application;

[0032] FIG. 3 is a conventional single adaptive optical closed-loop correction aberration result in Embodiment 3 of the present application;

[0033] FIG. 4 is a result of regional adaptive optical correction on an anisoplanatic aberration provided by the present application in Embodiment 3 of the present application; and

[0034] FIG. 5 is a regional image deconvolution processing result in Embodiment 3 of the present application.

DETAILED DESCRIPTION

[0035] The present application is further described in detail below in combination with the embodiments, so that those skilled in the art can implement the present application by referring to the text of this specification.

[0036] It should be understood that the terms such as “have”, “comprise” and “include” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

Embodiment 1

[0037] In adaptive optical biaxial scanning imaging, biaxial scanning includes an X direction and a Y direction. Referring to FIG. 1, an anisoplanatic aberration correction method for adaptive optical biaxial scanning imaging provided by this embodiment includes the following steps.

[0038] Step S1: an entire anisoplanatic imaging field of view of the biaxial scanning is divided into a plurality of sub-regions according to a scanning trajectory, wherein the sub-regions including sub-region 11, sub-region 12, . . . , sub-region 1N, sub-region 21, sub-region 22, . . . , sub-region MN. A field of view of each sub-region does not exceed 2° both in the X direction of scanning and the Y direction of scanning, and all the sub-regions satisfy the principle of an isoplanatic region. As shown in FIG. 1, H and V respectively represent angle values of the field of view in the X direction of scanning and the Y direction of scanning, and are not greater than 2, and M and N are positive integers. Each sub-region can be uniformly and equally divided or non-uniformly divided.

[0039] Step S2: an aberration of each isoplanatic sub-region is measured by a wavefront sensor in sequence, and feedback is performed in sequence to control a wavefront corrector to complete closed-loop correction of the aberration of each isoplanatic sub-region in sequence.

[0040] Step S3: a wavefront aberration of each sub-region measured by the wavefront sensor is converted to obtain a PSF of each sub-region, the PSF of each sub-region is taken as a PSF initial value and constraint condition of a formed image of each sub-region, and the deconvolution processing of the formed image of each sub-region is respectively completed by means of Wiener filtering, so as to supplementally correct a residual aberration of the formed image of each sub-region.

[0041] Step 3 is specifically as follows:

[0042] S3-1: a wavefront W.sub.i,j(ξ,η), 1≤i≤M, 1≤j≤N of each sub-region measured by the wavefront sensor is calculated to obtain a PSF h.sub.i,j(x,y), 1≤i≤M, 1≤j≤N of each sub-region, wherein

[00003]$h_{i,j}\left(x,y\right)={.Math.\int \int P_{i,j}\left(\xi ,\eta \right)\exp \left({\mathrm{jkW}}_{i,j}\left(\xi ,\eta \right)\right)\exp \left(-j\frac{k}{f}\left[\left(x\xi +y\eta \right)\right]\right)d\xi d\eta .Math.}_2^2$

[0043] in the formula, P.sub.i,j(ξ,η) is a pupil function of a sub-lens of the wavefront sensor; f is a focal length of the sub-lens; k is a wave number constant.

[0044] S3-2: the PSF of each sub-region is taken as a PSF initial value and constraint condition of a formed image of each sub-region, and the deconvolution processing of the formed image of each sub-region is respectively completed by means of the following iterative formula for incremental Wiener filtering, so as to supplementally correct a residual aberration of the formed image of each sub-region,

[00004]${i,j}_{\mathrm{new}}^{}\left(u,v\right)={i,j}_{\mathrm{old}}^{}\left(u,v\right)+\frac{{i,j}_{*}^{}\left(u,v\right)S\left(u,v\right)}{{.Math.{i,j}_{}\left(u,v\right).Math.}^2+{\gamma }_x};{i,j}_{\mathrm{new}}^{}\left(u,v\right)={i,j}_{\mathrm{old}}^{}\left(u,v\right)+\frac{{i,j}_{*}^{}\left(u,v\right)S\left(u,v\right)}{{.Math.{i,j}_{}\left(u,v\right).Math.}^2+{\gamma }_h};S\left(u,v\right)=Y\left(u,,v\right)-{i,j}_{}\left(u,v\right){i,j}_{}\left(u,v\right);$

[0045] wherein * represents a complex conjugate operator; i and j represent the serial number of each sub-region; Y.sub.i,j(u,v) represents Fourier transformation of the formed image of the sub-region; .sub.i,j.sup.new(u,v) and .sub.i,j.sup.old(u,v) respectively represents Fourier transformations, iterated in the current deconvolution and the previous deconvolution, of the formed image of the sub-region; .sub.i,j.sup.new(u,v) and .sub.i,j.sup.old(u,v) respectively represent Fourier transformations, iterated in the current deconvolution and the previous deconvolution, of a PSF estimate of the sub-region; S(u,v) is a precision term; as values of .sub.i,j.sup.new(u,v) and .sub.i,j.sup.new(u,v) are updated, the value of S(u,v) is updated timely; γ.sub.x and γ.sub.h are parameters for controlling an iteration step size; if the values of γ.sub.x and γ.sub.h are larger, the iteration step size is smaller, converging of the algorithm would be slower, and a solution thereof would be more accurate; and if the values of γ.sub.x and γ.sub.h decrease, the iteration step size increases, and the algorithm would converge faster into an unsmoothed solution. Values of γ.sub.x and γ.sub.h may be selected as: γ.sub.h=0.2|Ĥ(0,0)|.sup.2, γ.sub.x=0.2|{circumflex over (X)}(0,0)|.sup.2.

[0046] Step S3 can be carried out online or offline.

[0047] Step S4: after the deconvolution correction of the formed images of all the sub-regions is completed, the images are stitched to obtain a formed image of a wide field of view with M×N sub-regions, the anisoplanatic aberration of which is completely corrected.

Embodiment 2

[0048] An anisoplanatic aberration correction apparatus for adaptive optical biaxial scanning imaging is provided. The apparatus is configured to adopt the method of Embodiment 1 to achieve anisoplanatic aberration correction for adaptive optical biaxial scanning imaging. Specifically, referring to FIG. 2, the apparatus includes a light source and beam transformation system, a biaxial scanning system, an adaptive optical system, a beam collection system and a data processing system.

[0049] The light source and beam transformation system includes an imaging light source used for illumination imaging, a beacon light source used for aberration measurement, and an optical element used for transforming beams emitted by the imaging light source and the beacon light source. The light source and beam transformation system can also include light sources with other imaging functions.

[0050] The biaxial scanning system includes a scanning device capable of realizing beam scanning both in an X direction and in a Y direction; a scanning trajectory of the biaxial scanning system is configured to first scan the sub-regions along the X direction and then scans the sub-regions along the Y direction, or is configured to first scan the sub-regions along the Y direction and then scans the sub-regions along the X direction.

[0051] The adaptive optical system includes a wavefront sensor, a wavefront corrector and a wavefront processor. The wavefront sensor is configured to measure a wavefront aberration and output the wavefront aberration to the wavefront processor. The wavefront processor is configured to solve the wavefront aberration into a wavefront control quantity, and perform feedback according to a scanning synchronization signal of the biaxial scanning system to control the wavefront corrector to generate phase compensation, so as to realize closed-loop correction of the wavefront aberration.

[0052] The beam collection system includes an optical element used for completing focusing of imaging beams, and a detector for achieving photoelectric conversion. The beam collection system can have a variety of combinations, including a confocal imaging mode, a time-domain optical coherence tomography mode, a spectral-domain optical coherence tomography mode, or a Fourier-domain optical coherence tomography mode, or the like.

[0053] The data processing system is a digital processor or a computer, and is configured to complete, according to the scanning synchronization signal of the biaxial scanning system, image deconvolution on all the sub-regions on the scanning trajectory and image stitching on all the sub-regions having been subjected to the image deconvolution.

Embodiment 3 Comparison Between the Conventional Correction Method and the Method of the Present Application

[0054] Referring to FIG. 3 which illustrates a conventional single adaptive optical closed-loop correction aberration result, an imaging field of view is 4*4 degrees, and a central isoplanatic region of 2*2 degrees has a good aberration correction effect. Other edge fields of view are anisoplanatic regions, the aberration correction is incomplete, and the image is fuzzy.

[0055] Referring to FIG. 4 which illustrates a result of regional adaptive optical correction on an anisoplanatic aberration provided by the present application, the entire imaging field of view of 4*4 degrees is divided into four imaging sub-regions of 2*2 degrees to complete aberration correction in sequence. Referring to FIG. 5 which illustrates an effect of regional deconvolution processing of images provided by the present application, after the regional adaptive optical aberration correction in FIG. 4 is completed, deconvolution processing is continued, so as to complete the deconvolution processing of the images in four sub-regions by Wiener filtering respectively, which can correct the residual aberration of the images.

[0056] Although the implementation solutions of the present application have been disclosed as above, it is not limited to the applications listed in the specification and the implementations. The present application can be fully applied to various fields suitable for the present application. Those skilled in the art can easily implement additional modifications. Therefore, the present application is not limited to specific details without departing from the general concept defined by the claims and the equivalent scope.