CN116942077A - A highly universal fundus adaptive optical imaging system - Google Patents

Abstract

The application discloses a fundus self-adaptive optical imaging system with high universality, and belongs to the field of self-adaptive optics. The system matches eyes with different diopters by adopting a four-reflector system with adjustable spacing, so that high-resolution imaging can be carried out on fundus with diopters between-8D and 8D; the annular light inner diameter is adjusted by controlling the distance between the positive axicon lens and the negative axicon lens so as to adapt to corneas of different human eyes, so that the universality of an imaging system is improved, and stray light reflected by the corneas is avoided; the voice coil deformable mirror with large phase modulation amount is adopted to correct the ocular fundus aberration, so that the imaging precision is improved.

Description

A highly universal fundus adaptive optical imaging system

Technical field

The invention relates to a highly universal fundus adaptive optical imaging system, belonging to the field of adaptive optics.

Background technique

The fundus retina is the only tissue in the human body whose status can be observed using optical imaging technology under living, non-invasive conditions. High-resolution imaging is very important in the early diagnosis of cerebral arteriosclerosis, diabetes and other diseases (Yang Jie . Analysis of related factors of diabetic retinopathy [D]. Xinjiang Medical University, 2015.), the early symptoms of these diseases will cause lesions in the cones and capillaries of the fundus. The size of cones is 2-5 μm, and the diameter of retinal microvessels is about 5-8 μm, which exceeds the resolution capability of traditional fundus cameras (Gill J S, Moosajee M, Dubis AM. Cellular imaging of inherited retinal diseases using adaptive optics[J ].Eye,2019,33(5).). Using adaptive optics (AO) technology to compensate for human eye aberrations is an important means of obtaining high-resolution images of retinal cells and microvessels in the human eye.

At present, a lot of research has been conducted on fundus imaging technology based on adaptive optics at home and abroad, and different types of systems have been developed, mainly as follows: 1) Adaptive optics system based on liquid crystal wavefront corrector (Cheng Shaoyuan, Hu Lifa, Cao Zhaoliang, etc.). Application of liquid crystal adaptive optics in high-resolution imaging of human fundus [J]. China Laser, 2019, 46(7):0704009.) This system is based on a liquid crystal wavefront corrector, and liquid crystal has high pixel density, Advantages such as low voltage and programmable control; 2) Adaptive optical system based on dual piezoelectric deformable mirrors. This system uses two piezoelectric deformable mirrors to correct high-order and low-order aberrations of the fundus respectively, with high energy utilization. , but its driving voltage is high, the deformable mirror size is large, the overall structure is large (the overall system size is about 1400mm × 800mm), and the cost is high; 3) Adaptive optics system and optical coherence tomography technology, laser scanning ophthalmoscope and other imaging modes Combined with AO-OCT-SLO technology, it has large field of view and high-resolution imaging capabilities in the depth direction. These systems usually use the most advanced hardware and technology and have outstanding individual performances such as resolution or field of view, but the cost is high. As a result, the cost-effectiveness of the system is not outstanding, and it also limits the clinical application of adaptive optical fundus imaging systems. Clinical applications require that the imaging system can not only detect people with healthy vision, but also detect people with different degrees of myopia. Therefore, it is necessary to improve the universality of the adaptive optical imaging system and reduce the system cost.

A lot of research has also been done on the development of low-cost fundus imaging systems. Betul Sahin et al. proposed to estimate the aberration of the human eye in real time based on pupil tracking measurement to control the deformable mirror for distortion compensation without the need for a wavefront sensor (BETUL, SAHIN, BARBARA, et al.. Adaptive optics with pupil tracking for high resolution retinal imaging [ J].Biomedical optics express,2012,3(2):225-239.). Marwan Suheimat performs wavefront compensation based on MEMS (Micro Electro Mechanical System) (SUHEIMATM, DAINTY C.POSTER SESSION. High resolution flood illumination retinal imaging system with adaptive optics[C]//8th International Workshop on Adaptive Optics for Industry and Medicine.2020), However, the adjustment range for the diopter of different human eyes is small, and the wavefront correction range of MEMS is also small, so the universality will be relatively poor when applied. Fundus imaging adaptive optical system designed by Fuensanta et al. 2012) can only perform high-resolution imaging on the fundus of human eyes with normal vision or human eyes with small refractive power, and its universality is poor.

Contents of the invention

In order to solve the imaging problem of human eyes with different diopters and improve the universality of the high-resolution fundus adaptive optical imaging system, the present invention provides an optical path design that uses positive and negative axicon lenses with adjustable spacing to control the ring light. diameter, a four-mirror system with adjustable spacing is used to match human eyes with different diopters, and a voice coil deformable mirror with large phase modulation is used to correct fundus aberrations. It can not only satisfy high-resolution imaging for human eyes with normal vision, but also adjust and perform high-resolution imaging for human eyes with high refractive error. The purpose is to provide a highly universal adaptive optical system for high-resolution fundus imaging.

A highly universal fundus adaptive optical imaging system, the system includes five subsystems: target fixation subsystem, lighting subsystem, detection subsystem, imaging subsystem and pupil monitoring subsystem; wherein, the The optotype staring subsystem is used to prevent the human eye from moving irregularly due to untargeted staring, and at the same time, it guides the human eye to change its gaze direction by moving the optotype, thereby changing the fundus imaging area; the lighting subsystem is used to provide fundus imaging The imaging area provides illumination; the detection subsystem is used to measure the aberration of the human eye; the imaging subsystem is used to image the fundus retina; the pupil monitoring subsystem is used to assist alignment during the imaging process;

The system uses positive and negative axicon lenses with adjustable spacing to control the diameter of the ring light, a four-mirror system with adjustable spacing to match human eyes with different diopters, and a voice coil deformable mirror with large phase modulation amount to control the ring light. Fundus aberrations are corrected to achieve imaging of human eyes with different pupil sizes and diopters.

Optionally, the system includes a first light source 1, a second light source 2, a first lens 3 and a second lens 4, a first dichroic prism 5, a negative axicon lens 6 and a positive axicon lens 7, and a second dichroic prism 8. , the third dichroic prism 9, the third lens 10, the dichroic plate 11, the first reflecting mirror 12, the second reflecting mirror 13, the third reflecting mirror 14, the fourth reflecting mirror 15, the fourth lens 16, human eye or simulated human eye Eye 17, fifth lens 18, deformable mirror 19, fifth reflector 20, sixth lens 21, dichroic film 22, Shack-Hartmann wavefront detector 23, seventh lens 24, imaging camera 25, pupil camera 26. The eighth lens 27 and the LED sight mark light source 28;

Among them, the first reflector 12, the second reflector 13, the third reflector 14, and the fourth reflector 15 form a four-reflector system with adjustable spacing, and the second reflector 13 and the third reflector 14 are perpendicular to each other. The first reflecting mirror 12 and the fourth reflecting mirror 15 are perpendicular to each other, and the distance between the two sets of mutually perpendicular reflecting mirrors is adjusted to match the pupils of different human eyes.

Optionally, the first light source 1 is located on the focal plane of the first lens 3, and the second light source 2 is located on the focal plane of the second lens 4; the light emitted by the first light source 1 passes through The parallel light formed after the first lens 3, or the parallel light formed after the light emitted by the second light source 2 passes through the second lens 4 passes through the negative axicon lens 6 and the positive axicon lens 7 in sequence. It is parallel annular light; the cone angles of the negative axicon lens 6 and the positive axicon lens 7 are the same;

The inner diameter r ₂ of the ring light is:

Among them, r ₁ is the radius of the incident beam, d is the distance between the positive and negative axicon lenses, α is the cone angle of the positive and negative axicon lenses, and n is the refractive index of the axicon lens.

Optionally, when matching the pupils of different human eyes, the moving distance Δd between the two sets of mutually perpendicular reflectors is:

Among them, D is the diopter of the human eye, and f ₁₆ is the focal length of the fourth lens 16 .

Optionally, the light splitting ratio of the first dichroic prism 5, the second dichroic prism 8 and the third dichroic prism 9 is 50:50.

Optionally, the first light source 1 is an 808nm light source for wavefront detection; the second light source 2 is a 635nm light source for imaging; the first lens 3, the second lens 4 and the eighth lens 27 are The focal length of the third lens 10 is 50mm and the diameter is 25.4mm; the third lens 10 has a focal length of 300mm and the diameter is 50mm; the fourth lens 16 has a focal length of 125mm and a diameter of 25.4mm; the fifth lens 18 has a focal length of 200mm and a diameter of 50mm. ; The sixth lens 21 has a focal length of 75mm and a diameter of 25.4mm; the seventh lens 24 has a focal length of 125mm and a diameter of 25.4mm; all lenses are double cemented achromatic lenses, and their surfaces are coated with antireflection coatings.

Optionally, the central wavelength of the LED sight mark light source 28 is 550 nm; the transmission and reflection splitting ratio of the beam splitter 11 is 1:9; the deformable mirror 19 is a 69-unit deformable mirror with a clear aperture of 10 mm; The dichroic plate 22 is used to transmit the detection light of 808nm and reflect the light of 550nm and 635nm.

Optionally, the simulated human eye 17 includes a resolution plate and a lens with an aperture of 10 mm and a focal length of 20 mm. The aperture is 10 mm; the resolution plate is placed at the focal plane position of the lens to simulate the retina of the fundus of the human eye.

Optionally, when using simulated human eyes for wavefront correction and imaging, use the Shack-Hartmann wavefront detector 23 to measure the wavefront slope, and use the measured slope and the control matrix to calculate the force that should be applied to the deformable mirror 19 voltage, use the integral control method to perform closed-loop correction, and control the deformable mirror 19 to compensate for the distorted wavefront;

When using the human eye for wavefront correction and imaging, first, turn on the LED sight mark light source 28, and the human eye stares at the sight mark through the sight mark subsystem until a clear position, at which time the human eye is aligned in the optical path; then , repeat the previous steps, that is, use the Shaker-Hartmann wavefront detector 23 and the deformable mirror 19 to perform closed-loop correction.

This application also provides applications of the above system in wavefront correction and fundus adaptive optical imaging.

The beneficial effects of the present invention are:

The diameter of the annular light is controlled by using positive and negative axicon lenses with adjustable spacing, a four-mirror system with adjustable spacing to match human eyes with different diopters, and a voice coil deformable mirror with large phase modulation amount to adjust the fundus image. Correct the difference. It can not only satisfy high-resolution imaging for human eyes with normal vision, but also adjust and perform high-resolution imaging for human eyes with high refractive errors. The system of this application can perform high-resolution imaging on the fundus of human eyes with diopter between -8D and 8D, which improves the universality of the imaging system. By controlling the distance between the positive and negative axicon lenses, the inner diameter of the annular light is adjusted to adapt to the cornea of different human eyes, which also improves the universality of the imaging system and avoids stray light reflected by the cornea.

Description of the drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is the schematic diagram of the adaptive optical system for fundus imaging.

Figure 2 is a schematic diagram of the optical path when there is defocus.

Figure 3 Schematic diagram of the optical path after focusing.

Figure 4a shows the wavefront image before correction. The PV and RMS are 16.845μm and 8.135μm respectively;

Figure 4b shows the corrected wavefront image. The PV and RMS are 1.43μm and 0.225μm respectively.

Figure 5a is the image before correction obtained by the imaging camera;

Figure 5b is the corrected image obtained by the imaging camera.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

Example 1:

This embodiment provides a highly universal fundus adaptive optical imaging system. See Figure 1. The system includes five subsystems: target fixation subsystem, lighting subsystem, detection subsystem, imaging subsystem and pupil monitoring. subsystem.

In Figure 1, the first light source 1 is an 808nm light source, used for wavefront detection; the second light source 2 is a 635nm light source, used for imaging; the first lens 3 and the second lens 4 have a focal length of 50mm and an aperture of 25.4mm; The first dichroic prism 5 has a light splitting ratio of 50:50; 6 and 7 are axicon lenses respectively, of which 6 is a negative axicon lens and 7 is a positive axicon lens; the second dichroic prism 8 has a light splitting ratio of 50:50; the eighth lens The focal length of 27 is 50mm and the aperture is 25.4mm; 28 is the LED sight mark light source with a central wavelength of 550nm; the third dichroic prism 9 has a light split ratio of 50:50; 26 is the pupil camera, which is used to photograph the pupil of the human eye and assist the human eye in focusing. Quasi-optical path and imaging area adjustment; the third lens 10 has a focal length of 300mm and an aperture of 50mm; 11 is a beam splitter with a transmission and reflection split ratio of 1:9; the first reflector 12, the second reflector 13, and the third reflector 14 and the fourth reflector 15 form a four-mirror system with adjustable spacing, in which the second reflector 13 and the third reflector 14 are a set of reflectors placed perpendicularly to each other, and the first reflector 12 and the fourth reflector 15 It is a set of reflectors placed perpendicularly to each other. The distance between the two sets of perpendicular reflectors can be adjusted later to match the pupils of different human eyes; the focal length of the fourth lens 16 is 125mm and the aperture is 25.4mm; 17 is the human eye or Simulate the human eye, where the simulated human eye includes a resolution board and a lens with a focal length of 20mm and an aperture of 10mm; the fifth lens 18 has a focal length of 200mm and an aperture of 50mm; 19 is a 69-unit deformable mirror from ALPAO Company with a clear aperture 10mm; the fifth reflector 20 has a diameter of 25.4mm; the sixth lens 21 has a focal length of 75mm and a diameter of 25.4mm; 22 is a dichroic plate, which transmits 808nm detection light and reflects 550nm and 635nm light; 23 is Shaker Hartmann wavefront detector, the seventh lens 24 has a focal length of 125mm and an aperture of 25.4mm. 25 is an imaging camera, which is located on the focal plane of the lens 24 and is used for imaging the fundus of the eye. Among them, all lenses are double-cemented achromatic lenses, and their surfaces are coated with antireflection coatings.

Among them, the visual target staring subsystem consists of an LED visual target light source 28, an eighth lens 27, a second beam splitting prism 8, a third beam splitting prism 9, a third lens 10, a beam splitter 11, a first reflector 12, a second reflector It is composed of mirror 13, third reflecting mirror 14, fourth reflecting mirror 15, fourth lens 16 and human eye 17.

The illumination subsystem consists of the second light source 2, the second lens 4, the first dichroic prism 5, the negative axicon lens 6, the positive axicon lens 7, the second dichroic prism 8, the third dichroic prism 9, the third lens 10, the dichroic It is composed of a piece 11, a first reflecting mirror 12, a second reflecting mirror 13, a third reflecting mirror 14, a fourth reflecting mirror 15, a fourth lens 16 and a human eye 17.

The detection subsystem consists of a first light source 1, a first lens 3, a first dichroic prism 5, a negative axicon lens 6, a positive axicon lens 7, a second dichroic prism 8, a third dichroic prism 9, a third lens 10, and a dichroic prism. Piece 11, first reflector 12, second reflector 13, third reflector 14, fourth reflector 15, fourth lens 16, human eye 17, fifth lens 18, deformable mirror 19, fifth reflector 20 , the sixth lens 21, the dichroic film 22 and the Shaker Hartman 23.

The imaging subsystem consists of a human eye 17, a fourth lens 16, a fourth reflector 15, a third reflector 14, a second reflector 13, a first reflector 12, a beam splitter 11, a fifth lens 18, a deformable mirror 19, It is composed of a fifth reflecting mirror 20 , a sixth lens 21 , a dichroic film 22 , a seventh lens 24 and an imaging camera 25 .

The pupil monitoring subsystem consists of a human eye 17, a fourth lens 16, a fourth reflector 15, a third reflector 14, a second reflector 13, a first reflector 12, a beam splitter 11, a third lens 10, and a third beam splitter. It consists of prism 9 and pupil camera 26.

In the lighting subsystem, the size of the second light source 2 is an optical fiber with a diameter of 1 mm. The end face of the optical fiber that emits light is located on the focal plane of the second lens 4. After being collimated by the second lens 4, it passes through the first beam splitting prism 5. The reflected light Entering the negative axicon lens 6, the first dichroic prism 5 and the negative axicon lens 6 are both in parallel light. There are no strict requirements for their positions. They can be conveniently placed depending on the light path adjustment; the vertex of the negative axicon lens 6 is divided into hollow The light beam enters the positive axicon lens 7, and the cone angles of the two axicon lenses are the same to ensure that the light emitted from the positive axicon lens 7 is parallel annular light. The function of the positive and negative axicon lenses is to generate annular light beams to avoid the influence of stray light on the front surface of the human cornea on imaging. It replaces the traditional annular aperture. Compared with the traditional annular diaphragm, this application uses positive and negative axicon lenses whose spacing can be adjusted so that the diameter of the annular beam can be controlled. The formulas for the magnification M of positive and negative axicon lenses to the incident beam are as follows:

Among them, r ₁ is the radius of the incident beam, r ₂ is the inner ring radius of the annular beam, d is the distance between the two positive and negative axicon lenses, the cone angle α of the positive and negative axicon lenses is the same, and n is the axis The refractive index of a conic lens. Therefore, the inner diameter of the ring light is:

After the glass material and cone angle used in the positive and negative axicon lenses are fixed, the inner diameter r ₂ of the ring light has a linear relationship with d. Therefore, the inner diameter r ₂ of the ring light can be controlled by adjusting the value of the spacing d to match different people. The pupil of the eye.

The annular beam is transmitted through the second dichroic prism 8 and the third dichroic prism 9. The second dichroic prism 8 and the third dichroic prism 9 are in the parallel light path. Their positions are not strictly required. They can be adjusted to determine their placement. ; The transmitted light is focused by the third lens 10, and the focal points of the second lens 4 and the third lens 10 are at the same position; 10% of the light passes through the beam splitter 11 and is reflected by the four-mirror system before entering the fourth The positions of the lens 16, the beam splitter 11, the first reflector 12 and the fourth reflector 15 do not have strict requirements and can be adjusted according to the actual optical path; the annular beam formed after collimation by the fourth lens 16 enters the pupil of the human eye and finally forms in the fundus of the eye. Illumination spot, in which the third lens 10 and the fourth lens 16 have the same focal position, and the distance from the second reflector 13 and the third reflector 14 to the first reflector 12 and the fourth reflector 15 can be adjusted; at the pupil of the human eye At the focal plane position of the fourth lens 16.

In the imaging subsystem, when imaging, an 808nm light source is used. The light reflected by the fundus of the human eye 17 has a wavelength of 808nm. It is focused after passing through the fourth lens 16, and then passes through the fourth reflector 15, the third reflector 14, the second After reflection by the reflector 13 and the first reflector 12, it passes through the beam splitter 11, 90% of the light is reflected, and then collimated by the fifth lens 18. For a human eye with normal vision with diopter 0D, the fourth lens 16 and the fifth lens The focal points of 18 are coincident; the light collimated by the fifth lens 18 is incident on the deformable mirror 19, in which the mirror surface of the deformable mirror is located at the focal plane position of the fifth lens 18; the light modulated by the deformable mirror is reflected and returned to the fifth lens 18 , and after being reflected by the fifth reflector 20, it reaches the sixth lens 21. The fifth reflector 20 is tilted at 45 degrees and plays the role of a folding axis of the optical path; the light passing through the folding axis of the fifth reflector 20 is collimated by the sixth lens 21 Straight, the focal points of the fifth lens 18 and the sixth lens 21 coincide, so that the fifth lens 18 and the sixth lens 21 play a conjugate role, making the deformable mirror 19 and the Shack-Hartmann wavefront detector 23 conjugate; After being collimated by the sixth lens 21 and reflected by the dichroic plate, the 808nm light enters the seventh lens 24, and the focus positions of the sixth lens 21 and the seventh lens 24 coincide; finally, the light that passes through the seventh lens 24 is reflected in the camera 25 For imaging, the camera 25 is located on the focal plane of the seventh lens 24 .

As shown in Figure 2, after the light is condensed through the fourth lens 16, if the distance between the convergence point and the third lens 10 is greater (less than) the front focal length of the third lens 10, then the light beam passes through the third lens 10 and becomes the converged light ( Divergent light) will cause the wavefront detected by the wavefront detector to be larger out of focus. At this time, keep the first reflector 12 and the fifth reflector 15 stationary, and move the second reflector 13 and the third reflector 14 up and down, so that the light beam becomes parallel light after passing through the third lens 10, as shown in Figure 3 It shows that the wavefront detected by the wavefront detector is not out of focus at this time, and high-order aberrations can be better corrected. According to the Gaussian imaging formula, the moving distance Δd of the second reflector 13 and the third reflector 14 can be deduced as:

Among them, the unit of Δd is mm, Δd>0 means the second reflector 13 and the third reflector 14 move upward, Δd<0 means the second reflector 13 and the third reflector 14 move downward; f ₁₆ is the fourth lens 16 The focal length is in mm; D is the diopter of the human eye.

In this system, it has been confirmed that the focal length f 16 of the fourth lens ₁₆ =125mm, so the maximum adjustable diopter is 8D, and the second reflective mirror 13 and the third reflective mirror 14 have a certain moving range: -62.5mm≤Δd≤62.5 mm, corresponding to the focusing range of the fundus adaptive imaging system is -8D ~ 8D.

In the detection subsystem, most of the optical paths coincide with the imaging optical paths. During wavefront detection, a 635nm light source is used. The light reflected from the fundus of the human eye 17 has a wavelength of 635 nm. It is focused after passing through the fourth lens 16, and then reflected by the fourth reflecting mirror 15, the third reflecting mirror 14, the second reflecting mirror 13 and the first reflecting mirror 12. After passing through the beam splitter 11, 90% of the light is reflected and then collimated by the fifth lens 18. For a human eye with normal vision with diopter 0D, the focus of the fourth lens 16 and the fifth lens 18 coincide; Light is incident on the deformable mirror 19, where the mirror surface of the deformable mirror is located at the focal plane position of the fifth lens 18; the light modulated by the deformable mirror 19 is reflected back to the fifth lens 18, and is reflected by the fifth mirror 20 to the fifth lens 18. The six lenses 21 and the fifth reflecting mirror 20 are placed at an angle of 45 degrees to play the role of a folding axis of the optical path; the light passing through the folding axis of the fifth reflecting mirror 20 is collimated by the sixth lens 21, and the difference between the fifth lens 18 and the sixth lens 21 is The focus coincides, so that the fifth lens 18 and the sixth lens 21 play a conjugate role, making the deformable mirror 19 and the Shaker Hartmann wavefront detector 23 conjugate; after collimation by the sixth lens 21, the color separation The 635nm light enters the Shaker-Hartmann wavefront detector 23 , and the Shaker-Hartmann wavefront detector 23 is located on the focal plane of the sixth lens 21 .

In the target fixation subsystem, most of the light paths coincide with the lighting subsystem. The LED sight mark light source 28 is an LED light source with a central wavelength of 550 nm; the LED sight mark light source 28 is located on the focal plane of the eighth lens 27 and can move two-dimensionally in the direction of the vertical optical axis to guide the human eye to stare at the target and change imaging area. Then, the light passes through the second dichroic prism 8, part of the reflected light passes through the third dichroic prism 9, and part is transmitted. The positions of the second dichroic prism 8 and the third dichroic prism 9 are as described above; the transmitted light is passed through the third lens. 10 focusing, the focal points of the eighth lens 27 and the third lens 10 are at the same position; after passing through the beam splitter 11, 10% of the light is transmitted and is reflected by the first reflecting mirror 12, the second reflecting mirror 13, the third reflecting mirror 14 and After reflection by the fourth reflector 15, it enters the fourth lens 16. The positions of the beam splitter 11, the first reflector 12 and the fifth reflector 15 are not strictly required and can be adjusted according to the actual optical path; the annular shape formed by the collimation of the fourth lens 16 The light beam enters the pupil of the human eye and finally forms an illumination spot at the fundus of the eye. The third lens 10 and the fourth lens 16 have the same focal position, and the second reflector 13 and the third reflector 14 reach the first reflector 12 and the fourth reflector. The distance of 15 can be adjusted; the pupil of the human eye is at the focal plane position of the fourth lens 16. The optotype gaze subsystem plays a role in stabilizing the eyes and preventing the human eye from moving irregularly due to untargeted staring. At the same time, when moving the optotype, it can guide the eyes to change the direction of gaze, thereby changing the fundus imaging area.

In the pupil monitoring subsystem, part of the optical path coincides with the detection subsystem. The light reflected by the pupil of the human eye 17 passes through the fourth lens 16, then is reflected by the fourth reflecting mirror 15, the third reflecting mirror 14, the second reflecting mirror 13 and the first reflecting mirror 12, and then passes through the beam splitter 11. 10% of the light is transmitted, and is imaged on the pupil camera 26 after passing through the third lens 10 and the third dichroic prism 9 . The pupil camera 26 is at the focal plane of the third lens 10, and the positions of the remaining optical elements are the same as described in the detection subsystem. The pupil monitoring subsystem plays a role in assisting alignment.

Before performing wavefront correction, first replace the human eye with a simulated human eye17. The simulated human eye includes a lens with a diameter of 10mm and a focal length of 20mm and frosted glass. The frosted glass is placed at the focal plane of the lens to simulate the retina of the fundus of the human eye; the 635nm imaging light is turned off. , turn on the 808nm detection light, use the Shack-Hartmann wavefront detector 23 to measure the response function of the deformable mirror 19, and then calculate the control matrix.

When using simulated human eyes for wavefront correction and imaging, the wavefront slope can be measured with the Shaker Hartmann wavefront detector 23, and the voltage that should be applied to the deformable mirror 19 can be calculated using the measured slope and the control matrix. The integral control method performs closed-loop correction and controls the deformable mirror to compensate for the distorted wavefront. The compensated wavefront will be flatter and the resulting aberration will be smaller. During the calibration process, 635nm imaging light is collected on the imaging CCD, and high-resolution, large-field-of-view imaging results can be obtained on the CCD. When using the human eye for wavefront correction and imaging, first, turn on the optotype light source, and the human eye stares at the optotype through the optotype subsystem until a clear position is reached. At this time, the human eye is aligned in the optical path; then, repeat The previous step is to use the Shaker Hartmann wavefront detector 23 and the deformable mirror 19 to perform closed-loop correction; during the correction process, the 635nm imaging light is collected on the imaging CCD, and high resolution and large viewing angle can be obtained on the CCD. Field imaging results.

Embodiment 2

This embodiment provides a method for the above system to perform wavefront correction and fundus adaptive imaging. In this embodiment, the process of wavefront detection is simulated. First, a light lattice is generated; secondly, the slope is calculated based on the light lattice; and then , sparse the slope to simulate the sparse collection process of light points. At the same time, in the compression detection algorithm, if the slope with sparsity is satisfied, the slope recovery can be completed through a nonlinear reconstruction algorithm; fourth, for sparseization The slope is restored; finally, the wavefront can be reconstructed from the slope according to the conventional wavefront reconstruction algorithm.

1) The imaging camera 25 used is a pco.edge 4.2 model CCD camera, the single pixel size is 6.5μm, the resolution is 2048×2048, and the sensor size is 13.3mm×13.3mm;

2) The deformable mirror 19 used is a 69-unit voice coil deformable mirror from the French ALPAO company, with an effective aperture of 10.5 mm and a phase modulation depth of 60 μm.

3) The 808nm light source 1 used is a laser light source, MDL-E-808 laser from Changchun New Industry Company, used for wavefront detection; the second light source 2 is a 635nm light source from Daheng Company, used for imaging;

4) The first dichroic prism 5, the second dichroic prism 8, and the third dichroic prism 9 are all wide-band dichroic prisms of Daheng Company, 25.4mm×25.4mm×25.4mm, with a splitting ratio of 50:50.

5) The material of the positive and negative axicon lenses is ultraviolet grade fused silica (UVFS), the refractive index n is 1.517, and the cone angle is 20°, so r ₂ ≈0.214d is obtained from formula (2). Therefore, there is a linear relationship between the inner diameter r ₂ of the annular beam and the distance d between the positive and negative axicon lenses. By adjusting the value of the distance d, the inner diameter of the annular beam can be controlled to match the pupils of different human eyes.

6) The LED sight mark light source 28 is a Thorlabs LED light source with a central wavelength of 550nm;

7) The pupil camera 26 is a Thorlab CS165CU/M camera with 1.6 million pixels. It is used to photograph the pupil of the human eye and assist the human eye in aligning the light path and adjusting the imaging area.

8) The beam splitter 11 is a wide-band beam splitter from Daheng Company, with a transmission and reflection split ratio of 1:9.

9) The first reflector 12, the second reflector 13, the third reflector 14, the fourth reflector 15 and the fifth reflector 20 are all Daheng Company reflectors, with a diameter of 25.4mm and a thickness of 8mm. Among them, the second reflecting mirror 13 and the third reflecting mirror 14 are perpendicular to each other in the optical path, and the first reflecting mirror 12 and the fourth reflecting mirror 15 are perpendicular to each other.

10) The color separation film 22 is a long-wave pass color separation film, which transmits the detection light of 808nm and reflects the light of 550nm and 635nm;

11) 23 is a Shaker-Hartmann wavefront detector, and the camera is an ARTCAM-990SWIR camera from ARTRAY Company, with 1280×1024 pixels, a dynamic range of 12 bits, and a relative quantum efficiency of about 82%.

12) Using the above components, set up the light path according to Figure 1. Before performing wavefront correction, first replace the human eye with a simulated human eye17. The simulated human eye includes a lens with a diameter of 10mm and a focal length of 20mm and frosted glass. The frosted glass is placed at the focal plane of the lens to simulate the retina of the fundus of the human eye; the 635nm imaging light is turned off. , turn on the 808nm detection light, use the Shack-Hartmann wavefront detector 23 to measure the response function of the deformable mirror 19, and then calculate the control matrix.

13) When using simulated human eyes for wavefront correction and imaging, the Shack-Hartmann wavefront detector 23 can be used to measure the wavefront slope, and the measured slope and control matrix can be used to calculate the voltage that should be applied to the deformable mirror 19 , use the integral control method to perform closed-loop correction and control the deformable mirror to compensate for the distorted wavefront. The compensated wavefront will be flatter and the resulting aberration will be smaller. During the calibration process, 635nm imaging light is collected on the imaging CCD, and high-resolution, large-field-of-view imaging results can be obtained on the CCD.

14) Large defocus is artificially introduced, as shown in Figure 4a and Figure 4b. The wavefront before correction is shown in Figure 4a, PV and RMS are 16.845μm and 8.135μm respectively; the wavefront after correction is shown in Figure 4b, PV and RMS are 1.43μm and 0.225μm respectively. The images before and after correction obtained by the imaging camera 25 are shown in Figures 5a and 5b. Figure 5a is before correction, and the image is almost indistinguishable. Figure 5b is the resolution plate after correction, and stripes and numbers can be seen; after correction, it is clear The accuracy is significantly improved. At this time, the spot diameter on the CCD panel accounts for approximately 450 pixels, and the illumination area corresponding to the fundus of the eye corresponding to 450 pixels is approximately 293 μm.

Some steps in the embodiments of the present invention can be implemented using software, and corresponding software programs can be stored in readable storage media, such as optical disks or hard disks.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (10)

1. A highly versatile fundus-adaptive optical imaging system, the system comprising five subsystems: a sighting target staring subsystem, an illumination subsystem, a detection subsystem, an imaging subsystem and a pupil monitoring subsystem; the sighting target staring subsystem is used for avoiding irregular disturbance of eyes due to no target staring, and guiding the changes of the staring direction of the eyes by moving the sighting target so as to change the fundus imaging area; the illumination subsystem is used for providing illumination for a fundus imaging area of a human eye; the detection subsystem is used for measuring human eye aberration; the imaging subsystem is used for imaging the fundus retina; the pupil monitoring subsystem is used for auxiliary alignment in the imaging process;

the system adopts positive and negative axicon lenses with adjustable spacing to control the diameter of annular light, adopts a four-reflector system with adjustable spacing to match eyes with different diopters, adopts a voice coil deformable mirror with large phase modulation amount to correct the aberration of the bottom of the eye, and realizes imaging of eyes with different pupil sizes and different diopters.

2. The system according to claim 1, characterized in that the system comprises a first light source (1), a second light source (2), a first lens (3) and a second lens (4), a first dichroic prism (5), a negative axicon lens (6) and a positive axicon lens (7), a second dichroic prism (8), a third dichroic prism (9), a third lens (10), a dichroic sheet (11), a first mirror (12), a second mirror (13), a third mirror (14), a fourth mirror (15), a fourth lens (16), a human eye or simulated human eye (17), a fifth lens (18), a deformable mirror (19), a fifth mirror (20), a sixth lens (21), a dichroic sheet (22), a shack hartmann wavefront detector (23), a seventh lens (24), an imaging camera (25), a pupil camera (26), an eighth lens (27) and an LED vision standard light source (28);

the first reflecting mirror (12), the second reflecting mirror (13), the third reflecting mirror (14) and the fourth reflecting mirror (15) form a four-reflecting mirror system with adjustable distance, the second reflecting mirror (13) and the third reflecting mirror (14) are mutually perpendicular, the first reflecting mirror (12) and the fourth reflecting mirror (15) are mutually perpendicular, and the pupils of different eyes are matched by adjusting the distance between two groups of mutually perpendicular reflecting mirrors.

3. The system according to claim 2, characterized in that the first light source (1) is located on the focal plane of the first lens (3) and the second light source (2) is located on the focal plane of the second lens (4); parallel light generated by light emitted by the first light source (1) after passing through the first lens (3) or parallel light generated by light emitted by the second light source (2) after passing through the second lens (4) sequentially passes through a negative axicon lens (6) and a positive axicon lens (7) and then is parallel annular light; the cone angles of the negative axicon (6) and the positive axicon (7) are the same;

the inner diameter r of the annular light ₂ The method comprises the following steps:

wherein r is ₁ Is the radius of the incident beam, d is the distance between the positive and negative axicon, α is the cone angle of the positive and negative axicon, and n is the refractive index of the axicon.

4. A system according to claim 3, wherein the distance Δd of movement between the two sets of mutually perpendicular mirrors when matching the pupils of different eyes is:

wherein D is the diopter of the human eye, f ₁₆ Is the focal length of the fourth lens (16).

5. The system according to claim 4, characterized in that the splitting ratio of the first (5), second (8) and third (9) splitting prisms is 50:50.

6. The system according to claim 5, characterized in that the first light source (1) is a 808nm light source for wavefront detection; the second light source (2) is a 635nm light source and is used for imaging; the focal length of the first lens (3), the second lens (4) and the eighth lens (27) is 50mm, and the caliber is 25.4mm; the focal length of the third lens (10) is 300mm, and the caliber is 50mm; the focal length of the fourth lens (16) is 125mm, and the caliber is 25.4mm; the focal length of the fifth lens (18) is 200mm, and the caliber is 50mm; the focal length of the sixth lens (21) is 75mm, and the caliber is 25.4mm; the focal length of the seventh lens (24) is 125mm, and the caliber is 25.4mm; all lenses were double cemented achromats and the surface was coated with an anti-reflection film.

7. The system of claim 6, wherein the LED optotype light source (28) has a center wavelength of 550nm; the transmission and reflection light splitting ratio of the light splitting sheet (11) is 1:9; the deformable mirror (19) is a 69-unit deformable mirror with a light transmission caliber of 10mm; the color separation film (22) is used for transmitting 808nm detection light and reflecting 550nm and 635nm light.

8. The system according to claim 7, characterized in that the simulated human eye (17) comprises a resolution plate and a lens with a 10mm aperture and a focal length of 20mm, the aperture being 10mm; the resolution board is placed at the focal plane position of the lens and is used for simulating the retina of the ocular fundus.

9. The system according to claim 8, characterized in that, when performing wavefront correction and imaging with an analog human eye, the wavefront slope is measured with a shack hartmann wavefront sensor (23), the voltage that should be applied to the deformable mirror (19) is calculated with the measured slope and the control matrix, closed loop correction is performed with an integral control method, and the deformable mirror (19) is controlled to compensate for the distorted wavefront;

when the human eyes are used for wavefront correction and imaging, firstly, an LED sighting target light source (28) is turned on, the human eyes stare at a sighting target through a sighting target subsystem until the sighting target is in a clear position, and the human eyes are aligned in a light path at the moment; the preceding steps are then repeated, namely closed loop correction using the shack Hartmann wavefront sensor (23) and the deformable mirror (19).

10. Use of the system of any one of claims 1-9 for wavefront correction and fundus adaptive optical imaging.