Focusing-free fundus imaging system based on free-form surface

Abstract

The invention discloses a free-form surface-based focusing-free fundus imaging system, and belongs to the technical field of fundus imaging. The system comprises a light source module, a light splitting module, a light condensing module, a scanning module, a transmitting mirror group, an eyepiece group and a light detection module, the entrance pupil of the transmitting mirror group is located at the focus of the first parabolic mirror, and the eye pupil is located at the focus of the second parabolic mirror. The transmission lens group is used for correcting field aberration and human eye diopter aberration and comprises a first lens, a second lens, a first free-form surface lens, a second free-form surface lens, a third lens and a fourth lens; the third lens and the fourth lens converge the light of the eyepiece group to form a first image surface; the first free-form surface lens and the second free-form surface lens modulate the phase of the first image surface and correct diopter aberration; the first lens and the second lens perform aberration correction on the exit pupil and compress the light size to match the scanning module. The system has the advantages of ultra-wide angle, high resolution, no mydriasis and simple operation.

Description

Technical Field

[0001] The present invention belongs to the technical field of fundus imaging, and more specifically, relates to a free-form surface-based focus-free fundus imaging system. Background Art

[0002] Fundus imaging technology plays a vital role in screening and diagnosing various eye diseases, such as hypertension, glaucoma, maculopathy, age-related maculopathy and diabetic retinopathy. Myopia (or hyperopia) is a common eye disease, and the refractive error it causes will affect the clarity of fundus imaging and easily lead to misdiagnosis.

[0003] Common fundus imaging devices correct the effects of refractive errors by manually or electrically moving the lens group. This often increases the complexity and difficulty of operation of the system, and the movement of the lens group will also introduce additional errors, affecting the final image quality. Some portable fundus imaging devices use the automatic focus function of the mobile phone lens to compensate for diopter, but their field of view angle is often small, generally 45°, which can easily lead to missed diagnosis of peripheral retinal lesions. The use of diffractive optical elements can correct high-order aberrations caused by refractive errors, but their diffraction efficiency is sensitive to wavelength and incident angle, and is not suitable for ultra-wide-angle multi-wavelength fundus imaging devices. Summary of the invention

[0004] In view of the defects of the related art, the purpose of the present invention is to provide a focus-free fundus imaging system based on a free-form surface, aiming to solve the problem of cumbersome operation of moving the lens for refractive compensation in existing fundus imaging equipment, as well as the problem of small field of view angle, which easily leads to missed diagnosis of peripheral retinal lesions.

[0005] To achieve the above-mentioned object, the present invention provides a free-form surface-based focus-free fundus imaging system, comprising: a light source module, a light splitting module, a light focusing module, a scanning module, a light detection module, a transmission lens group and an eyepiece lens group;

[0006] The light source module is used to emit light as a light source; the light source passes through the light splitting module, the light focusing module, the scanning module, the transmission lens group and the eyepiece lens group in sequence along the first light path direction, and then reaches the retina of the human eye through the pupil; the reflected light from the fundus of the human eye passes through the eyepiece lens group, the transmission lens group, the scanning module, the light focusing module and the light splitting module in sequence along the second light path direction, and is split in the light splitting module and incident on the light detection module, and the light detection module converts the light signal into a digital image;

[0007] The eyepiece assembly comprises a first parabolic reflector and a second parabolic reflector, each of which has a hole in the center. The entrance pupil of the transmission mirror assembly is located at the focus of the first parabolic reflector, and the pupil of the human eye is located at the focus of the second parabolic reflector, and the two form a conjugate relationship. The eyepiece assembly is used to transmit the incident light to the human eye and transmit the reflected light of the human eye back to the transmission mirror assembly.

[0008] The transmission lens group is used to correct the field aberration and the human eye refractive aberration, and the transmission lens group includes a first lens, a second lens, a first free-form surface lens, a second free-form surface lens, a third lens and a fourth lens arranged in sequence along the first optical path direction;

[0009] The third lens and the fourth lens are used to converge the light emitted from the eyepiece group, and form a first image plane between the first free-form surface lens and the second free-form surface lens; the first free-form surface lens and the second free-form surface lens are used to modulate the phase of the primary imaging surface and correct the refractive aberration; the free-form surface expressions of the first free-form surface lens and the second free-form surface lens are:

[0010]

[0011] Among them, z is the sag of the free-form surface, c is the vertex curvature, k is the cone coefficient, and c j is the coefficient of the high-order term of the free-form surface, r 2 =x 2 +y 2 ;c4x 2 and c6y 2 For diopter aberration correction, c7x 3 and c 10 y 3 Used for phase modulation function;

[0012] The first lens and the second lens are used to perform aberration correction on the exit pupil and compress the light size to match the scanning module;

[0013] The scanning module is used to emit light with different field angles in the same direction;

[0014] The focusing module is used to convert the incident light in the first light path into parallel light, and to converge the light passing through the scanning module to the light splitting module in the second light path.

[0015] Optionally, the distance between the first free-form surface lens and the second free-form surface lens and the primary imaging surface is less than 15 mm.

[0016] Optionally, the gap between the second lens and the first lens is 15 to 20 mm; the gap between the second lens and the first free-form surface lens is 80 to 85 mm; the gap between the first free-form surface lens and the second free-form surface lens is 23 to 26 mm; the gap between the second free-form surface lens and the third lens is 20 to 25 mm; and the gap between the third lens and the fourth lens is 3 to 5 mm.

[0017] Optionally, the first lens is a cemented lens, the first surface along the first optical path direction is a convex surface, the radius of curvature is set to -10 to -15 mm, the second surface is a concave surface relative to the first surface, the radius of curvature is set to 40 to 45 mm, the third surface is a convex surface, the radius of curvature is set to -20 to -25 mm, the center thickness between the first surface and the second surface is 9 to 10 mm, and the center thickness between the second surface and the third surface is 4 to 5 mm;

[0018] The first surface of the second lens along the first optical path is a concave surface, the radius of curvature is set to 10-11 mm, the second surface is a concave surface, the radius of curvature is set to 16-18 mm, and the center thickness is 7-8 mm;

[0019] The first surface of the first free-form surface lens along the first optical path direction is a free-form surface, the vertex curvature radius is set to 20-25 mm, the second surface is a free-form surface, the vertex curvature radius is set to 30-35 mm, and the center thickness is 9-10 mm;

[0020] The second free-form surface lens is a cemented lens, wherein the first surface along the first optical path direction is a free-form surface, the vertex curvature radius is set to -90 to -96 mm, the second surface is a concave surface relative to the first surface, the curvature radius is set to 55 to 60 mm, the third surface is a free-form surface, the vertex curvature radius is set to 101 to 106 mm, the center thickness between the first surface and the second surface is 11 to 13 mm, and the center thickness between the second surface and the third surface is 11 to 13 mm;

[0021] The first surface of the third lens along the first optical path is a convex surface, the radius of curvature is set to -10 to -13 mm, the second surface is a concave surface, the radius of curvature is set to 20 to 25 mm, and the center thickness is 6 to 7 mm;

[0022] The first surface of the fourth lens along the first optical path direction is a convex surface with a curvature radius of -60 to -65 mm, the second surface is a convex surface with a curvature radius of -25 to -30 mm, and the center thickness is 7 to 8 mm.

[0023] Optionally, the light source module is a single-wavelength light source or a multi-wavelength light source.

[0024] Optionally, the light source module emits laser light with a wavelength of 488nm, 520nm, 635nm, or 785nm.

[0025] Optionally, the beam splitter module is a beam splitter or a beam splitter group; the beam splitter is a cube beam splitter or a flat beam splitter.

[0026] Optionally, the focusing module includes a plano-convex lens, a biconcave lens and a biconvex lens in sequence along the first light path direction.

[0027] Optionally, the scanning module uses a two-dimensional galvanometer, and the vibration amplitude of the two-dimensional galvanometer is not greater than 20°.

[0028] Optionally, the light detection module includes a detector and a host computer;

[0029] The detector is used to convert the received human eye fundus reflected light into an electrical signal and transmit it to the host computer;

[0030] The host computer reconstructs images of different fields of view according to the received electrical signals and splices them together to obtain fundus images.

[0031] Compared with the prior art, the above technical solution conceived by the present invention can achieve the following beneficial effects:

[0032] 1. The present invention provides a free-form surface-based focus-free fundus imaging system, which adopts a transmission lens group including two free-form surface lenses. By utilizing the excellent aberration correction ability of the free-form surface, the aberration caused by the refractive human eye can be compensated without adjusting the position of the transmission lens, thereby realizing focus-free imaging of a human eye with a larger range of refractive power. The scanning module reflects the outgoing light of the transmission lens group along the second optical path, so that light rays with different field angles will be emitted in the same direction, thereby realizing point scanning. The aberration correction of the free-form surface combined with the double parabolic reflector group and the field of view splicing technology realizes ultra-wide-angle fundus imaging with an extraocular field angle of 138° (intraocular field angle of 206°), and the full-field optical resolution reaches 23um; the entire system has the advantages of ultra-wide angle, high resolution, no mydriasis, and easy operation.

[0033] 2. The present invention provides a free-form surface-based focus-free fundus imaging system. The free-form surface-containing transmission lens group realizes focus-free imaging within the refractive range of -15D to +15D through the design of the lens shape, combined with the setting of parameters such as the curvature radius and the center thickness, and the full-field optical resolution reaches 23um. The entire system is easy to operate and has both ultra-wide-angle and high-resolution characteristics.

[0034] 3. The present invention provides a free-form surface-based non-focus fundus imaging system, wherein the transmission lens group containing the free-form surface has excellent aberration correction capability and is insensitive to the incident wavelength. The light source module of the fundus imaging system can select a multi-wavelength light source to obtain retinal color photos, thereby obtaining richer retinal information. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a structural schematic diagram of a free-form surface-based focus-free fundus imaging system provided by an embodiment of the present invention;

[0036] Figure 2 is a schematic structural diagram of a transmission lens assembly provided by an embodiment of the present invention;

[0037] Figure 3 This is the full field spot diagram of a human eye with a diopter of -15D;

[0038] Figure 4 This is the full field spot diagram of a human eye with a diopter of -10D;

[0039] Figure 5 This is the full field spot diagram of a normal human eye;

[0040] Figure 6 This is the full field spot diagram of a 10D diopter human eye;

[0041] Figure 7 This is the full field spot diagram of a 15D diopter human eye;

[0042] Description of reference numerals:

[0043] 1. Light source module; 2. Spectral module; 3. Focusing module; 4. Scanning module; 5. Transmission lens group; 6. Eyepiece lens group; 7. Human eye; 8. Detector; 9. Host computer. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] The contents involved in the above embodiment are described below in conjunction with a preferred embodiment.

[0046] like Figure 1 As shown, a free-form surface-based focus-free fundus imaging system comprises: a light source module 1, a light splitting module 2, a light focusing module 3, a scanning module 4, a light detection module, a transmission lens group 5 and an eyepiece lens group 6;

[0047] The light source module 1 is used to emit light as a light source; the light source passes through the light splitting module 2, the light focusing module 3, the scanning module 4, the transmission lens group 5 and the eyepiece lens group 6 in sequence along the first light path direction, and then reaches the retina of the human eye 7 through the pupil; the fundus reflected light of the human eye 7 passes through the eyepiece lens group 6, the transmission lens group 5, the scanning module 4, the light focusing module 3 and the light splitting module 2 in sequence along the second light path direction, and is split by the light splitting module 2 and incident on the light detection module, and the light detection module converts the light signal into a digital image;

[0048] The eyepiece assembly 6 includes a first parabolic reflector and a second parabolic reflector with holes in the center, respectively; the entrance pupil of the transmission lens assembly 5 is located at the focus of the first parabolic reflector, and the pupil of the human eye is located at the focus of the second parabolic reflector, and the two form a conjugate relationship; the eyepiece assembly 6 is used to transmit the incident light to the human eye 7, and transmit the reflected light of the human eye 7 back to the transmission lens assembly 5;

[0049] The transmission lens group 5 is used to correct the field aberration and the human eye refractive aberration, and the transmission lens group 5 includes a first lens, a second lens, a first free-form surface lens, a second free-form surface lens, a third lens and a fourth lens arranged in sequence along the first optical path direction;

[0050] The third lens and the fourth lens are used to converge the light emitted from the eyepiece group 6, and form a first image plane between the first free-form surface lens and the second free-form surface lens; the first free-form surface lens and the second free-form surface lens are used to modulate the phase of the primary imaging surface and correct the refractive aberration; the free-form surface expressions of the first free-form surface lens and the second free-form surface lens are:

[0051]

[0052] Among them, z is the sag of the free-form surface, c is the vertex curvature, k is the cone coefficient, and c j is the coefficient of the high-order term of the free-form surface, r 2 =x 2 +y 2 ;c4x 2 and c6y 2 For diopter aberration correction, c7x 3 and c 10 y 3 Used for phase modulation function;

[0053] The first lens and the second lens are used to perform aberration correction on the exit pupil and compress the light size to match the scanning module 4;

[0054] The scanning module 4 is used to emit light with different viewing angles in the same direction;

[0055] The focusing module 3 is used to convert the incident light in the first light path into parallel light, and to converge the light passing through the scanning module 4 to the light splitting module 2 in the second light path.

[0056] In the existing technology, the autofocus function of the mobile phone lens or the diffractive optical element can be used to correct the high-order aberrations caused by the refractive error, but its field of view is often small and is not suitable for ultra-wide-angle multi-wavelength fundus imaging equipment. A free-form surface is a surface that does not contain any rotational symmetry or translational symmetry. It has a very high degree of design freedom, provides more variables for optimizing aberrations, and exhibits excellent aberration correction capabilities in imaging systems.

[0057] When performing fundus imaging examination, the subject places his eyes at the inspection hole of the fundus imaging system and looks in different directions according to the instructions to image the fields of view in different directions. The laser is transmitted along the first optical path through the beam splitter, focusing module, scanning module, transmission lens group and eyepiece group, and then reaches the retina of the subject's eye through the pupil; it is reflected at the fundus of the human eye, and the reflected light passes through the eyepiece group, transmission lens group, scanning module, focusing module and beam splitter module in sequence along the second optical path. The beam splitter module uses a beam splitter and is reflected to the light detection module through the beam splitter. The light detection module converts the light signal into a digital image. The scanning module reflects the outgoing light along the second optical path, and the light rays of different field angles will be emitted in the same direction, thereby realizing point scanning. Furthermore, the scanning module uses a two-dimensional galvanometer, and the vibration amplitude of the two-dimensional galvanometer is not greater than 20°.

[0058] The eyepiece group 6 is used to expand the imaging field angle and realize ultra-wide-angle fundus imaging. The first free-form surface lens and the second free-form surface lens are located on both sides of the primary imaging surface, so that the free-form surface lens can realize the phase modulation function. Furthermore, the distance between the first free-form surface lens and the second free-form surface lens and the primary imaging surface is less than 15 mm.

[0059] The entrance pupil of the transmission mirror assembly 5 is located at the focus of the first parabolic reflector, and the pupil of the human eye is located at the focus of the second parabolic reflector, and the two form a conjugate relationship, which facilitates the transmission mirror assembly 5 containing a free-form surface to correct aberrations.

[0060] In the expression of free-form surface, the introduction of cubic terms of odd terms plays the role of wavefront coding, which can make the system insensitive to the defocus amount. The main reason for the different refractive powers of the human eye is the different focusing ability of the lens. The use of the designed free-form surface lens can enhance the defocus invariance of the fundus imaging system, reduce the impact of the focusing difference of the human eye lens, and realize focus-free fundus imaging.

[0061] The first free-form surface lens and the second free-form surface lens are used, and the excellent aberration correction ability of the free-form surface is utilized to compensate for the aberration caused by the refractive human eye without adjusting the position of the transmission lens, and to achieve focus-free imaging of the human eye with a refractive power of -15D to +15D. The first parabolic reflector and the second parabolic reflector with through holes in the center, where the through hole diameter is 30mm≤≤80mm, can achieve ultra-wide-angle fundus imaging with an extraocular field of view angle of 138° (intraocular field of view angle of 206°).

[0062] The focusing module 3 is used to focus the reflected light of the scanning module 4 to the light splitting module 2; it only focuses the light and does not perform additional correction on the aberration. In one specific embodiment, the focusing module includes a plano-convex lens, a biconcave lens, and a biconvex lens in sequence along the first optical path.

[0063] Optionally, the gap between the second lens and the first lens is 15 to 20 mm; the gap between the second lens and the first free-form surface lens is 80 to 85 mm; the gap between the first free-form surface lens and the second free-form surface lens is 23 to 26 mm; the gap between the second free-form surface lens and the third lens is 20 to 25 mm; and the gap between the third lens and the fourth lens is 3 to 5 mm.

[0064] The gaps between the lenses of the transmission lens group are limited to improve the imaging effect.

[0065] Optionally, the first lens is a cemented lens, the first surface along the first optical path direction is a convex surface, the radius of curvature is set to -10 to -15 mm, the second surface is a concave surface relative to the first surface, the radius of curvature is set to 40 to 45 mm, the third surface is a convex surface, the radius of curvature is set to -20 to -25 mm, the center thickness between the first surface and the second surface is 9 to 10 mm, and the center thickness between the second surface and the third surface is 4 to 5 mm;

[0066] The first surface of the second lens along the first optical path is a concave surface, the radius of curvature is set to 10-11 mm, the second surface is a concave surface, the radius of curvature is set to 16-18 mm, and the center thickness is 7-8 mm;

[0067] The first surface of the first free-form surface lens along the first optical path direction is a free-form surface, the vertex curvature radius is set to 20-25 mm, the second surface is a free-form surface, the vertex curvature radius is set to 30-35 mm, and the center thickness is 9-10 mm;

[0068] The second free-form surface lens is a cemented lens, wherein the first surface along the first optical path direction is a free-form surface, the vertex curvature radius is set to -90 to -96 mm, the second surface is a concave surface relative to the first surface, the curvature radius is set to 55 to 60 mm, the third surface is a free-form surface, the vertex curvature radius is set to 101 to 106 mm, the center thickness between the first surface and the second surface is 11 to 13 mm, and the center thickness between the second surface and the third surface is 11 to 13 mm;

[0069] The first surface of the third lens along the first optical path is a convex surface, the radius of curvature is set to -10 to -13 mm, the second surface is a concave surface, the radius of curvature is set to 20 to 25 mm, and the center thickness is 6 to 7 mm;

[0070] The first surface of the fourth lens along the first optical path direction is a convex surface with a curvature radius of -60 to -65 mm, the second surface is a convex surface with a curvature radius of -25 to -30 mm, and the center thickness is 7 to 8 mm.

[0071] The transmission lens group with free-form surface realizes focus-free imaging within the refractive range of -15D to +15D through the design of lens shape and the setting of parameters such as curvature radius and center thickness.

[0072] Optionally, the light source module is a single-wavelength light source or a multi-wavelength light source.

[0073] Optionally, the light source module emits laser light with a wavelength of 488nm, 520nm, 635nm, or 785nm.

[0074] Select the light source module according to the requirements to meet the multi-wavelength light source detection requirements. The light source module 1 is used to emit light as a light source to illuminate the fundus. In this embodiment, the light source module 1 is used to emit laser. The light source module 1 can select laser but is not limited to laser. Figure 1 The light source module 1 in the figure only shows one light source, but the actual light source module 1 can be one of a single-wavelength light source and a multi-wavelength light source; when a multi-wavelength light source is used, lasers of different wavelengths are usually combined by a beam combiner to form a beam of light, and then enter the spectroscopic module 2; illustratively, the light source module 1 has emission wavelengths of 488nm, 520nm, 635nm, and 785nm, and the light is combined by a beam combiner to form a beam of light and then enters the spectroscopic module 2.

[0075] Optionally, the beam splitter module is a beam splitter or a beam splitter group; the beam splitter is a cube beam splitter or a flat beam splitter.

[0076] Optionally, the light detection module includes a detector 8 and a host computer 9;

[0077] The detector 8 is used to convert the received fundus reflected light of the human eye 7 into an electrical signal and transmit it to the host computer 9;

[0078] The host computer 9 reconstructs images of different fields of view according to the received electrical signals and splices them to obtain fundus images.

[0079] The designed free-form surface-based focus-free fundus imaging system was used to perform full-field imaging of human eyes with diopters of -15D, 10D, 0D, 10D, and 15D, respectively, with light sources emitting wavelengths of 488nm, 520nm, 635nm, and 785nm. The full-field point arrays of human eyes with different diopters are shown in the following figure. Figures 3 to 7 As shown, Figure 3 This is the full field of view spot diagram of a human eye with a diopter of -15D. Figure 4 This is the full field of view point diagram of a 10D human eye. Figure 5 is the full field of view point diagram of a normal human eye. Figure 6 This is the full field of view point diagram of a 10D human eye. Figure 7 This is the full field point diagram of a 15D diopter human eye.

[0080] Figure 2 : is a schematic diagram of the structure of the transmission lens group 5 containing free-form surfaces in the fundus imaging device. In this embodiment, the entire lens group contains 4 free-form surfaces. The coefficients of the high-order terms of the free-form surfaces are shown in Table 1 below.

[0081] Table 1 Free-form surface parameters

[0082] The first free-form surface The second free-form surface The third free-form surface The fourth free-form surface <![CDATA[c4]]> 77.274 100.262 139.458 -60.111 <![CDATA[c6]]> 64.641 71.17 -22.674 70.609 <![CDATA[c7]]> 1010.194 580.701 333.512 863.797 <![CDATA[c 10 ]]> -28.275 -53.796 -557.107 -117.563

[0083] By Figures 3 to 7 As shown, 9 fields of view are obtained at each diopter (fields 1 to 9 correspond to object planes extending from 8.5 mm to -11.98 mm in sequence), and the RMS radius for each diopter is shown in Table 2 below:

[0084] Table 2 RMS radius

[0085]

[0086]

[0087] Combined with Table 2 Figures 3 to 7 It can be seen that the combination of the eyepiece group, the transmission lens group with free-form surfaces, and the scanning module, plus the field of view stitching technology, can achieve ultra-wide-angle fundus imaging with an extraocular field of view angle of 138° (intraocular field of view angle of 206°). At the same time, without moving the lens group to focus, refractive compensation imaging of the human eye with a diopter of -15D to +15D can be achieved, and the full-field optical resolution reaches 23um. The entire system is easy to operate and has both ultra-wide-angle and high-resolution characteristics.

[0088] In the embodiment of the present invention, two free-form surface lenses are arranged in the transmission mirror group, and the excellent aberration correction ability of the free-form surface is utilized. Without adjusting the position of the transmission lens, the aberration caused by the refractive human eye can be compensated, and the focus-free imaging within the refractive range of -15D to +15D can be achieved. The aberration correction of the free-form surface is combined with the double parabolic reflector group and the field of view splicing technology to achieve an ultra-wide-angle fundus imaging with an extraocular field of view angle of 138° (an intraocular field of view angle of 206°), and the full-field optical resolution reaches 23um. The cumbersome operation of moving the lens for diopter compensation in the existing fundus imaging equipment and the technical problem that the field of view angle is small and easily causes the missed diagnosis of peripheral retinal lesions are solved. The system has the advantages of ultra-wide angle, high resolution, no mydriasis, and easy operation.

[0089] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A free-form surface-based focus-free fundus imaging system, characterized in that: include: Light source module, light splitting module, light focusing module, scanning module, light detection module, transmission lens group and eyepiece lens group; The light source module is used to emit light; the light passes through the light splitting module, the light focusing module, the scanning module, the transmission lens group and the eyepiece lens group in sequence along the first light path direction, and then reaches the retina of the human eye through the pupil; the reflected light from the fundus of the human eye passes through the eyepiece lens group, the transmission lens group, the scanning module, the light focusing module and the light splitting module in sequence along the second light path direction, and is split in the light splitting module and incident on the light detection module, and the light detection module converts the light signal into a digital image; The eyepiece assembly comprises a first parabolic reflector and a second parabolic reflector, each of which has a hole in the center. The entrance pupil of the transmission mirror assembly is located at the focus of the first parabolic reflector, and the pupil of the human eye is located at the focus of the second parabolic reflector, and the two form a conjugate relationship. The eyepiece assembly is used to transmit the incident light to the human eye and transmit the reflected light of the human eye back to the transmission mirror assembly. The transmission lens group is used to correct the field aberration and the human eye refractive aberration, and the transmission lens group includes a first lens, a second lens, a first free-form surface lens, a second free-form surface lens, a third lens and a fourth lens arranged in sequence along the first optical path direction; The third lens and the fourth lens are used to converge the light emitted from the eyepiece group to form a first image plane between the first free-form surface lens and the second free-form surface lens; the first free-form surface lens and the second free-form surface lens are used to modulate the phase of the primary imaging surface to correct the diopter aberration; The free-form surface expressions of the first free-form surface lens and the second free-form surface lens are: Among them, z is the sag of the free-form surface, c is the vertex curvature, k is the cone coefficient, and c j is the coefficient of the high-order term of the free-form surface, r 2 =x 2 +y 2 ;c4x 2 and c6y 2 For diopter aberration correction, c7x 3 and c 10 y 3 Used for phase modulation function; The first lens and the second lens are used to perform aberration correction on the exit pupil and compress the light size to match the scanning module; The scanning module is used to emit light with different field angles in the same direction; The focusing module is used to convert the incident light in the first light path into parallel light, and to converge the light passing through the scanning module to the light splitting module in the second light path.

2. The system according to claim 1, characterized in that The distance between the first free-form surface lens and the second free-form surface lens and the primary imaging surface is less than 15 mm.

3. The system according to claim 1, characterized in that The gap between the second lens and the first lens is 15-20 mm; the gap between the second lens and the first free-form surface lens is 80-85 mm; the gap between the first free-form surface lens and the second free-form surface lens is 23-26 mm; the gap between the second free-form surface lens and the third lens is 20-25 mm; the gap between the third lens and the fourth lens is 3-5 mm.

4. The system according to claim 3, characterized in that The first lens is a cemented lens, the first surface along the first optical path direction is a convex surface, the radius of curvature is set to -10 to -15 mm, the second surface is a concave surface relative to the first surface, the radius of curvature is set to 40 to 45 mm, the third surface is a convex surface, the radius of curvature is set to -20 to -25 mm, the center thickness between the first surface and the second surface is 9 to 10 mm, and the center thickness between the second surface and the third surface is 4 to 5 mm; The first surface of the second lens along the first optical path is a concave surface, the radius of curvature is set to 10-11 mm, the second surface is a concave surface, the radius of curvature is set to 16-18 mm, and the center thickness is 7-8 mm; The first surface of the first free-form surface lens along the first optical path direction is a free-form surface, the vertex curvature radius is set to 20-25 mm, the second surface is a free-form surface, the vertex curvature radius is set to 30-35 mm, and the center thickness is 9-10 mm; The second free-form surface lens is a cemented lens, wherein the first surface along the first optical path direction is a free-form surface, the vertex curvature radius is set to -90 to -96 mm, the second surface is a concave surface relative to the first surface, the curvature radius is set to 55 to 60 mm, the third surface is a free-form surface, the vertex curvature radius is set to 101 to 106 mm, the center thickness between the first surface and the second surface is 11 to 13 mm, and the center thickness between the second surface and the third surface is 11 to 13 mm; The first surface of the third lens along the first optical path is a convex surface, the radius of curvature is set to -10 to -13 mm, the second surface is a concave surface, the radius of curvature is set to 20 to 25 mm, and the center thickness is 6 to 7 mm; The first surface of the fourth lens along the first optical path direction is a convex surface with a curvature radius of -60 to -65 mm, the second surface is a convex surface with a curvature radius of -25 to -30 mm, and the center thickness is 7 to 8 mm.

5. The system according to claim 1, wherein: The light source module is one of a single-wavelength light source and a multi-wavelength light source.

6. The system according to claim 5, characterized in that The light source module emits lasers with wavelengths of 488nm, 520nm, 635nm and 785nm.

7. The system according to claim 1, characterized in that The beam splitter module is a beam splitter or a beam splitter group; the beam splitter is a cube beam splitter or a flat beam splitter.

8. The system of claim 1, wherein: The focusing module includes a plano-convex lens, a biconcave lens and a biconvex lens in sequence along the first light path direction.

9. The system according to claim 1, characterized in that The scanning module adopts a two-dimensional galvanometer, and the vibration amplitude of the two-dimensional galvanometer is not greater than 20°.

10. The system according to claim 1, wherein: The light detection module includes a detector and a host computer; The detector is used to convert the received human eye fundus reflected light into an electrical signal and transmit it to the host computer; The host computer reconstructs images of different fields of view according to the received electrical signals and splices them together to obtain fundus images.

Images