CN115844323A

CN115844323A - Optical lens group suitable for color fundus image system, visibility compensation method and driving method

Info

Publication number: CN115844323A
Application number: CN202211581176.1A
Authority: CN
Inventors: 彭先兆
Original assignee: Svision Imaging Ltd
Current assignee: Svision Imaging Ltd
Priority date: 2022-12-09
Filing date: 2022-12-09
Publication date: 2023-03-28
Anticipated expiration: 2042-12-09
Also published as: WO2024120321A1; CN115844323B

Abstract

The invention relates to an optical lens group, a visibility compensation method and a driving method which are suitable for a color fundus image system, wherein the optical lens group comprises: the imaging system comprises an entrance pupil, a scanning mirror group, a middle image plane, an eyepiece group and an exit pupil which are sequentially arranged along a first direction, wherein the entrance pupil is positioned on a focal plane on one side of the scanning mirror group, which is far away from the middle image plane; the exit pupil is positioned on the focal plane of the eyepiece group at the side far away from the middle image plane and is superposed with the pupil of the eye when the eye is detected; the curvature radius of field curvature of the intermediate image plane in the meridian plane is less than 2 times of the effective focal length of the ocular lens group, and the field curvature bends to one side of the ocular lens group; the effective focal length of the scanning lens group is larger than that of the eyepiece group, and the air space between the scanning lens group and the eyepiece group is larger than the transverse diameter of the middle image plane and smaller than the sum of the effective focal lengths of the scanning lens group and the eyepiece group. The invention provides an optical lens group which has a simple structure, can meet the requirements of ultra-wide angle and wide spectrum, has low distortion and high image quality and is suitable for a color fundus image system.

Description

Optical lens group suitable for color fundus image system, visibility compensation method and driving method

Technical Field

The present invention relates to optical lens designs for fundus imaging systems, and more particularly to an optical lens assembly, a diopter compensation method, and a driving method suitable for a color fundus imaging system.

Background

The fundus examination is one of the highest-frequency examination items in ophthalmology, the most widely used in the ophthalmology is fundus color photography, the imaging range of the traditional fundus camera is only 45 degrees, only 11.5 percent of the whole retina can be covered, and various peripheral fundus lesions can be missed to be diagnosed. After the ultra-wide-angle color confocal fundus camera appears, the fundus imaging range is greatly improved, and the missed diagnosis probability of peripheral lesions is reduced. The ultra-wide angle color fundus camera usually adopts a scanning mode to eliminate or reduce the problems of corneal and lens surface reflection, and two implementation modes of confocal scanning and wide line scanning are mainly adopted. Confocal scanning can achieve better stray light elimination and achieve a larger scanning visual field, but the colors are not real enough, and stray light elimination is complex in a wide line scanning mode.

The invention patent No. 202111440377.5 discloses a fundus imaging eyepiece capable of being switched to a wide angle/super wide angle, which is suitable for super wide angle fundus imaging eyepiece of optical tomography coherent imaging, but the structure is difficult to expand to the wide spectrum requirement of color images. Meanwhile, the patent also discloses a design of an eyepiece, which consists of a meniscus positive lens and a biconvex single aspheric lens, can realize an ultra-wide-angle field of view of more than 100 degrees, but is mainly applied to optical tomography coherent imaging or monochromatic confocal scanning laser ophthalmoscopes, the spectral range is not wide, or the optical tomography coherent imaging or the monochromatic confocal scanning laser ophthalmoscopes are limited in near infrared bands, the dispersion problem is not outstanding, and therefore, the special correction is not carried out on dispersion. US patent nos. US3390935 and US4286844 disclose designs of 80 ° and 90 ° eyepieces suitable for visible light bands, respectively, which can be used as eyepieces for conventional microscopes and telescopes, but these designs use 6 or more pieces of lenses, and if they are used for fundus imaging, the illumination light forms a reflection on the surface of each eyepiece lens which is difficult to eliminate, and thus is not practically used for fundus imaging.

Disclosure of Invention

The invention aims to provide an optical lens group, a visibility compensation method and a driving method which have simple structure, meet the optical requirements of ultra-wide angle, wide spectrum and high image quality, have small number of lenses and are suitable for a color fundus image system.

In order to achieve the purpose, the invention provides an optical lens group suitable for a color fundus image system, which comprises an entrance pupil, a scanning lens group, an intermediate image plane, an eyepiece group and an exit pupil, wherein the entrance pupil, the scanning lens group, the intermediate image plane, the eyepiece group and the exit pupil are sequentially arranged along a first direction; the exit pupil is positioned on the focal plane of the eyepiece group on the side far away from the middle image plane, and is superposed with the pupil of the eye when the eye is detected; the curvature radius of curvature of field in the meridian plane on the middle image plane is less than 2 times of the effective focal length of the ocular lens group, and the curvature of field bends to one side of the ocular lens group; the effective focal length of the scanning lens group is larger than that of the ocular lens group, and the air space between the scanning lens group and the ocular lens group is larger than the transverse diameter of the middle image surface and smaller than the sum of the effective focal lengths of the scanning lens group and the ocular lens group.

The invention also provides a diopter compensation method for the optical lens group suitable for the color fundus image system, the optical lens group comprises an entrance pupil, a scanning lens group, a middle image plane, an eyepiece group and an exit pupil which are sequentially arranged along the first direction, wherein the scanning lens group comprises a second double cemented positive lens and a front lens group which are arranged along the first direction,

and performing visibility compensation by changing an air interval L2 between the eyepiece group and the scanning lens group and an air interval L1 between a front lens group and a second double cemented lens in the scanning lens group.

The invention also provides a driving method of the optical lens group suitable for the color fundus image system, the optical lens group comprises an entrance pupil, a scanning lens group, a middle image plane, an eyepiece group, an exit pupil and a driving device which are sequentially arranged along the first direction, wherein the scanning lens group comprises a second double cemented positive lens and a front lens group which are arranged along the first direction,

and the driving device changes the air interval L2 between the eyepiece group and the scanning lens group and the air interval L1 between the front lens group and the second double cemented lens in the scanning lens group according to the received human eye visibility information, so that the L1 and the L2 meet the preset relationship.

The optical lens group of the color fundus image system has the following advantages:

1. the optical lens group consists of a group of wide-angle ocular lens groups and a group of scanning lens groups, has simple integral structure and small lens quantity, can meet the optical requirements of ultra wide angle and wide spectrum, is matched with the scanning lens groups to realize complete aberration correction, and obtains image quality with low distortion and diffraction limit level in full-field full spectrum;

2. the incidence and emergence angles of the light rays on the surfaces of the mirror surfaces are small, the types of glass materials are few, and only conventional stable glass materials are adopted, so that convenience is brought to the production and processing of the lenses, and great flexibility is brought to the arrangement of light paths;

3. the eyepiece group only has four reflecting surfaces, so that the risk of ghost images at the center of an image caused by the reflection of the lens is reduced, and the requirements of ultra-wide angle and wide-spectrum dispersion correction are met;

4. positive and negative visibility compensation is realized by simultaneously moving two air spaces between the scanning lens group and the eyepiece group as well as between the front lens group and the second double cemented lens in the scanning lens group, so that aberration introduced by high visibility compensation under an ultra-large visual field and a wide spectrum is effectively reduced;

5. the intermediate image plane is double telecentric imaging, namely telecentric imaging can be realized on the intermediate image plane by the eyepiece group and the scanning mirror, and the visual field range is kept unchanged while the visual degree compensation is carried out.

The optical lens design of the invention can be suitable for various colored fundus imaging devices such as fundus photography, confocal scanning laser ophthalmoscope, line scanning ophthalmoscope, wide line scanning ophthalmoscope and the like, and is also suitable for three-dimensional image modes with depth information such as optical coherence tomography.

Drawings

FIG. 1 is a schematic view of an optical lens assembly according to an embodiment of the present invention;

FIG. 2 is a schematic view of field curvature (dashed line) in a meridian plane at an intermediate image plane according to a first embodiment of the present invention;

fig. 3 is a schematic view of a field curvature and an astigmatism curve of an intermediate image plane according to a first embodiment of the invention;

FIG. 4 is a diagram illustrating an aberration Ray Fan in accordance with a first embodiment of the present invention;

FIG. 5 is a diagram illustrating a wavefront aberration OPD according to a first embodiment of the present invention;

FIG. 6 is a diagram illustrating the distribution of the RMS wavefront aberration within the field of view according to a first embodiment of the invention;

fig. 7 is a schematic view of a field curvature and an astigmatism curve according to a first embodiment of the invention;

FIG. 8 is a diagram illustrating an angle-enlarged distortion curve according to a first embodiment of the present invention;

FIG. 9 (left) is a schematic diagram of wavefront aberration compensated by only moving the scanning mirror assembly according to the present invention;

FIG. 9 (right) is a schematic diagram of wavefront aberration compensated by simultaneously changing the air space between the eyepiece group and the scanning lens group and the air space between the front lens group and the second cemented positive lens according to the embodiment of the present invention;

FIG. 10 (left) is a schematic view of field curvature and astigmatism compensated by moving only the scanning mirror assemblies according to the embodiment of the present invention;

FIG. 10 (right) is a schematic diagram of wavefront aberration compensated by simultaneously changing the air space between the eyepiece lens group and the scanning lens group and the air space between the front lens group and the second cemented positive lens according to the embodiment of the present invention;

FIG. 11 is a schematic view of the adjustment of the air gap of a lens at different near sightedness in accordance with the first embodiment of the present invention;

FIG. 12 is a schematic diagram illustrating an adjustment curve of L1/L2 during compensation of myopia according to a first embodiment of the present invention;

FIG. 13 is a schematic structural view of a second optical lens assembly according to a second embodiment of the present invention;

FIG. 14 is a diagram illustrating the optical line Fan aberration Ray Fan according to a second embodiment of the present invention;

FIG. 15 is a diagram illustrating a wavefront aberration OPD according to a second embodiment of the present invention;

FIG. 16 is a diagram illustrating the distribution of RMS wavefront aberrations over a field of view in accordance with a second embodiment of the invention;

fig. 17 is a schematic view of field curvature and astigmatism curves of a second embodiment of the invention;

fig. 18 is a schematic view of an angle-enlarged distortion curve according to a second embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The present invention provides an optical lens assembly, a diopter compensation method and a driving method suitable for a color fundus image system, and the following describes embodiments of the present invention in detail with reference to the accompanying drawings.

Example one

Fig. 1 is a schematic structural diagram of an optical lens assembly according to a first embodiment of the present invention. As shown in fig. 1, the optical lens assembly 100 includes: the imaging system comprises an entrance pupil 50, a scanning mirror group 40, an intermediate image plane 30, an eyepiece group and an exit pupil 10 of the 20 which are sequentially arranged along a first direction, wherein the entrance pupil 50 is positioned on a focal plane on one side of the scanning mirror group 40, which is far away from the intermediate image plane 30; the exit pupil 10 is located on a focal plane of the eyepiece group 20 on the side far away from the intermediate image plane 30, and the exit pupil 10 is overlapped with the pupil of the eye when the eye is detected; the curvature radius of field curvature of the intermediate image plane 30 in the meridian plane is less than 2 times of the effective focal length of the ocular lens group, and the field curvature bends to one side of the ocular lens group 20; the effective focal length of the scanning mirror group 40 is greater than that of the ocular mirror group 20, and the air space between the scanning mirror group 40 and the ocular mirror group 20 is greater than the transverse diameter of the intermediate image plane 30 and less than the sum of the effective focal lengths of the scanning mirror group 40 and the ocular mirror group 20.

When the fundus image is taken, a beam of parallel illumination light starts from the entrance pupil 50 along a first direction, passes through the entrance pupil 50 and the scanning mirror group 40, is focused on the intermediate image plane 30, then passes through the ocular mirror group 20, enters the eye pupil (coinciding with the exit pupil 10 of the ocular mirror group 20) and converges on the fundus. After the illumination light is reflected or scattered by the fundus, a part of the light returns through the original path to reach the entrance pupil 50. If there is a beam splitting device at this location, a portion of the light will be directed in a different direction than the incident illumination light and thus detected by the detector. The light splitting can be realized by coating or by arranging different transmission and reflection areas on a plane, which depends on the specific modes of illumination, light splitting and detection.

Based on the design of the optical lens assembly 100 shown in fig. 1, fundus photography, confocal scanning laser ophthalmoscope, line scanning laser ophthalmoscope and wide line scanning slit ophthalmoscope can be realized. The invention does not limit the application scene of the optical lens group.

Further, the eyepiece group 20 in the optical lens group 100 includes: the second lens 23, the third lens 22 and the first lens 21 are sequentially arranged along the first direction, the first lens 21 is an aspheric positive lens, the second lens 22 is a negative lens, the third lens 23 is a positive lens, and the second lens 22 and the third lens 23 form a first doubly-cemented positive lens 223. The first lens 21 is a single aspheric positive lens or a double aspheric positive lens, one surface close to the second lens 22 is an even aspheric surface, and the other surface is a spherical or aspheric mirror. Preferably, the first lens 21 may be a positive meniscus lens, which is curved toward the exit pupil 10, and for the avoidance of ambiguity, the concave surface of the positive meniscus lens faces the exit pupil 10, and the convex surface faces the second lens 22.

The first lens 21 and the third lens 23 are made of medium dispersion materials, and the second lens (negative lens) 22 is made of high-refractive-index and high-dispersion flint glass materials. Specifically, referring to table one, the first lens 21 is made of a material having a refractive index greater than 1.5 and an abbe number of 40 to 65; the second lens 22 is made of a material with a refractive index larger than 1.7 and an Abbe number smaller than 40; the third lens 23 is made of a material having a refractive index of more than 1.6 and an Abbe number of 40 to 65. Preferably, the first lens 21 and the third lens 23 may be made of the same material having a refractive index greater than 1.6 and an abbe number between 40 and 65.

Watch 1

Lens and lens assembly	Refractive index	Abbe number
			First lens	Refractive index > 1.5	65 & gt Abbe number & gt 40
Second lens	Refractive index > 1.7	40 > Abbe number
			Third lens	Refractive index > 1.6	65 & gt Abbe number & gt 40

In this embodiment, the focal length of the first lens element 21 is smaller than that of the first cemented doublet positive lens element 223, and the effective focal length of the eyepiece group 20 is between 20mm and 40 mm; the distance from the surface of one side of the exit pupil 10 of the first lens 21 to the exit pupil 10 is 10mm to 40 mm; the effective focal length of the first lens 21 of the eyepiece group 20 is smaller than that of the first cemented doublet positive lens 223.

In the optical lens assembly 100 of the present embodiment, the optical power of the eyepiece assembly 20 is shared by two positive lenses (the first lens 21 and the third lens 23), the first lens 21 takes on most of the optical power of the eyepiece assembly 20, the shape of the meniscus is favorable for reducing the exit angle of the peripheral light rays on the surface of the first lens 21 near the exit pupil 10, and the first cemented positive lens 223 formed by the second lens 22 and the third lens 23 has functions of dispersion correction and less optical power.

In this embodiment, the distance from the surface on the exit pupil 10 side of the first aspheric positive lens 21 to the exit pupil 10 is 21.4mm, the distance (working distance) to the anterior surface of the cornea is 19mm, an ultra-wide angle of 95 ° is realized on the eye side, the design spectral width is from 445nm blue light to 920nm near infrared, and the paraxial angle magnification is 3.1. For the illumination path, the entrance pupil 50 diameter is 8-10mm, corresponding to an exit pupil diameter of 2.6-3.2mm, and the image side (fundus) numerical aperture is 0.08 to 0.10; for imaging, the entrance pupil 50 (if the fundus is taken as the starting point of the light, the "entrance pupil 50" is referred to as the exit pupil at this time, and is still referred to as the entrance pupil for consistency), which has a diameter of 4mm, corresponds to an exit pupil diameter of 1.3mm, and has an image-side (fundus) numerical aperture of 0.04.

Further, the scanning mirror group 40 in the optical mirror group 100 includes: a fifth lens 43, a fourth lens 42 and a front lens group 41 arranged in sequence along the first direction, wherein the front lens group 41 includes at least one positive lens (in other embodiments, the front lens group 41 may be composed of a plurality of lenses), the fifth lens is a negative lens, the fourth lens is a positive lens, and the fourth lens 42 and the fifth lens 43 constitute a second double cemented positive lens 423. In the present embodiment, the fourth lens 42 is made of low dispersion crown glass with refractive index less than 1.7 and abbe number between 50 and 85; the fifth lens 43 is made of flint glass material with refractive index larger than 1.7 and Abbe number smaller than 40. Preferably, in the present embodiment, at least one positive lens element of the front lens group (when being a single-piece positive lens element) 41 and the fifth lens element 43 are made of the same material as the second lens element 21 of the eyepiece group 20.

The eyepiece lens assembly 20 and the scanning lens assembly 40 form a telecentric image at the intermediate image plane 30.

The design of the eyepiece group 20 takes into account the short focal length required for ultra-wide field of view and the dispersion correction required for color imaging, while employing as few lenses and reflective surfaces as possible, the number of lenses being much lower than in US3390935 and US4286844 of similar field of view. If the number of lenses is less than that of the first embodiment, in order to satisfy the short focal length required for the ultra-wide field of view, the eyepiece set 20 can only use a single positive lens or two positive lenses, which is not only difficult to perform effective dispersion correction, but also introduces additional dispersion into the eyepiece set 20 itself, which imposes a great design pressure on the scanning mirror set 40, making it extremely complex. Through many design attempts of the inventor, in order to achieve similar image quality requirements, the number of the lenses of the scanning mirror assembly exceeds 7, and reaches 14 at most, and it is difficult to avoid large incident angles above 45 degrees, and if the number of the lenses of the eyepiece assembly 20 is higher than that of the first embodiment, it is difficult to eliminate central reflection on the surfaces of the lenses in the eyepiece assembly 20. If the first lens 21 is replaced with a cemented doublet, the focal power is difficult to ensure, and it is difficult to realize an ultra-wide field of view. If the first cemented doublet 223 composed of the second lens 22 and the third lens 23 is replaced by a cemented triplet, although the number of glass-air interfaces is not increased, the diameter of the intermediate image plane 30 will be increased, and the rear surface of the cemented triplet is closer to the intermediate image plane 30, and the intermediate image plane 30 formed by high myopia will be very close to the rear surface of the cemented triplet, thereby greatly increasing the risk of central reflection on the lens surface.

One of the key points of the present invention is that the eyepiece group 20 only corrects the central field of view of the intermediate image plane 30, overcorrects the off-axis lateral chromatic aberration, and simultaneously releases off-axis aberrations such as field curvature, astigmatism, coma, and distortion of the intermediate image plane 30, and the field curvature and astigmatism of the intermediate image plane 30 are particularly prominent. The scanning lens group 40 adopts a single lens (or lens group) and double-cemented structure similar to the eyepiece group 20, and the field curvature, astigmatism and dispersion on the intermediate image plane 30 are opposite to the intermediate image formed by the fundus through the eyepiece group 20, so that most off-axis aberrations are cancelled. This has the advantage of greatly simplifying the design of the overall optical system. The scanning mirror array 40 can use only three mirrors at minimum, and just compensates the uncorrected (or overcorrected) off-axis aberration of the intermediate image plane. The whole light path can adopt only six lenses at least, namely, the wide spectrum from blue light 445nm to near infrared 920nm and diffraction limit order imaging in the full-field range of 95-degree ultra-wide-angle vision are achieved. FIG. 2 is a schematic view of the in-plane field curvature (dashed line) of the meridian at the intermediate image plane according to the first embodiment of the present invention; fig. 3 is a schematic view of the field curvature and astigmatism curves of the intermediate image plane according to the first embodiment of the invention.

Although the off-axis aberration of the intermediate image plane 30 is large, the combination of the eyepiece lens assembly 20 and the scanning lens assembly 40 can use only 6 lenses, and at least 3 glass materials, to achieve the image quality of the diffraction limit order in the wide spectral range from blue light to near infrared and the ultra-large field of view. FIG. 4 is a schematic diagram of a Ray Fan aberration Ray Fan according to a first embodiment of the invention; FIG. 5 is a diagram illustrating a wavefront aberration OPD according to a first embodiment of the present invention; FIG. 6 is a diagram illustrating the distribution of RMS wavefront aberrations within a field of view in accordance with a first embodiment of the invention; fig. 7 is a schematic view of field curvature and astigmatism curves according to a first embodiment of the invention. As shown in fig. 4, the light Ray Fan aberration Ray Fan of the first embodiment is lower than 10 μm in the full field of view. As shown in fig. 5, the peak-to-peak value of the wavefront aberration OPD of the first embodiment is about 0.5wave. As shown in fig. 6, the root mean square wavefront aberration is below the diffraction limit of 0.07wave throughout the field of view. As shown in fig. 7, the image side NA is 0.04, so that the focal plane depth of field can be calculated to be 0.5mm. In FIG. 7, the field curvature, astigmatism, axial chromatic aberration, and lateral chromatic aberration are all much lower than the depth of field of the focal plane. Fig. 8 is a schematic diagram of an angle-enlarged distortion curve according to a first embodiment of the present invention. Distortion is defined as the change of the angle of the scanning angle before the cornea relative to the angle magnification of the principal ray of the entrance pupil along with the angle, and the specific formula is as follows:

wherein gamma is the angular magnification distortion, theta is the angle of the chief ray at the entrance pupil 50 with respect to the optical axis, M is the paraxial angular magnification,

is the angle of the chief ray at the exit pupil 10 relative to the optical axis corresponding to the entrance pupil chief ray angle theta. As shown in fig. 8, the angular distortion of the entire optical path is within 1.5%.

In addition to diopter changes, off-axis aberrations increase dramatically when the eye deviates from emmetropia. The degree to which off-axis aberrations increase is also different for different wavelengths. This is not a serious problem for conventional visual field or narrow spectrum fundus image applications. For example, in the invention patent application No. 202111440377.5, although the visual field range reaches more than 87 degrees, the spectral width is limited to the near infrared band range, the dispersion is low, and the added additional aberration is still within the acceptable range under the condition of myopia up to 21D. Therefore, the visibility compensation can be realized by only moving the scanning lens group to change the air space between the ocular lens and the scanning lens group, which is the visibility compensation mode of most standard visual field or achromatic fundus image equipment.

The compensation of the visibility of wide-spectrum color wide-angle images is much more complicated. According to the Navarro myopia human eye model, for an ultra-wide angle vision field of 95 degrees, the change of off-axis aberration along with the diopter is much larger than that of near infrared under a visible light wave band, the aberration change degrees caused by the change of different wavelengths along with the diopter are different, and the change of blue light is severe. The drastic change in off-axis aberrations makes the aberrations very different from the normal for high-vision situations, which is further exacerbated by the ultra-wide angles. Therefore, the compensation of the visibility of an ultra-wide-angle, broad-spectrum fundus image cannot rely solely on changing the air separation between the ocular and scanning lens assemblies, which would otherwise result in a drastic reduction in the system image quality with increasing deviation of visibility.

With reference to fig. 1, the present embodiment further provides a method for compensating the visibility of an optical lens assembly suitable for a color fundus image system, the optical lens assembly includes an entrance pupil 50, a scanning lens assembly 40, an intermediate image plane 30, an eyepiece lens assembly 20 and an exit pupil 10, which are sequentially arranged along a first direction, wherein the scanning lens assembly 40 includes a second cemented doublet positive lens 423 and a front lens assembly 41, which are arranged along the first direction, and the visibility compensation is performed by changing an air interval L2 between the eyepiece lens assembly 20 and the scanning lens assembly 40 and an air interval L1 between the front lens assembly 41 and the second cemented doublet positive lens 423 in the scanning lens assembly 40.

Further, in the optical lens group visibility compensation method, myopia compensation is performed by reducing an air interval L2 between the eyepiece group 20 and the scanning lens group 40 and an air interval L1 between a front lens group 41 and a second cemented doublet 423 in the scanning lens group 40; the hyperopia compensation is performed by increasing the air space L2 between the eyepiece group 20 and the scanning mirror group 40 and the air space L1 between the front mirror group 41 and the second cemented doublet 423 in the scanning mirror group 40.

The present invention better solves the above problems by adjusting the air space L2 between the scanning mirror group 40 and the eyepiece group 20 and simultaneously adjusting the air space L1 between the front mirror group 41 and the second doublet 423 in the scanning mirror group 40 to perform aberration compensation, thereby realizing large-scale visibility compensation and maintaining good image quality.

By way of comparison, figure 9 shows the difference in image quality between the two above approaches when compensating for-5D myopia. FIG. 9 (left) is a diagram illustrating wavefront aberration when only the scanning mirror group is moved (only L2 is changed) for compensation; fig. 9 (right) is a diagram illustrating wavefront aberration when compensating by simultaneously changing L2 and the air space L1 between the front lens group and the second cemented positive lens. taking-5D myopia compensation as an example, if the air gap L2 between the scanning lens group 40 and the ocular lens group 20 is reduced by 9.75mm for refocusing, the imaging quality of the peripheral region is significantly reduced, as shown in fig. 9 (left). If the air space L2 between the scanning lens group 40 and the ocular lens group 20 is reduced by 6.15m, and the air space L1 between the front lens group 41 and the fourth lens group 42 is reduced by 3.29mm, the image quality is reduced much less. As shown in fig. 9, the image quality of fig. 9 (right) is significantly better than that of fig. 9 (left).

FIG. 10 (left) is a schematic diagram of curvature of field and astigmatism compensated by only moving the scanning mirror assembly (only changing L2); fig. 10 (right) is a schematic diagram of curvature of field and astigmatism when L2 and the air space L1 between the front lens group and the second cemented positive lens are simultaneously changed for compensation. The field curvature astigmatism in fig. 10 (right) is significantly lower than in fig. 10 (left).

FIG. 11 is a schematic diagram of adjusting the air gap of a lens at different degrees of myopia according to a first embodiment of the present invention. As shown in fig. 11, as the nearsightedness increases, the interval L2 between the scanning lens group 40 and the eyepiece group 20 and the air interval L1 between the front lens group 41 and the fourth lens element 42 become smaller. FIG. 12 is a diagram illustrating the adjustment curve of L1/L2 during compensation of myopia according to the first embodiment.

The compensation for hyperopia is achieved by increasing the air space L2 from the front lens group 41 to the third lens element 23 and the air space L1 from the second double cemented lens group 423 to the front lens group 41, the relative movement direction of the lenses being opposite to that of the compensation for myopia.

In the first embodiment, for ± 21D diopter compensation, the air distance L2 between the scanning lens group 40 and the eyepiece lens group 20 varies by ± 25.5mm, and the air distance L1 between the scanning front lens group 41 and the second cemented doublet 423 varies by ± 10.7mm.

The driving device for changing the two air gaps L1 and L2 can be implemented by a conventional mechanical wire casing of the zoom lens or other transmission modes, or can be composed of two stepping motors for respectively driving the positions of the front lens group 41 and the second doublet-cemented lens group 423, or respectively driving the positions of the scanning lens group 40 and the front lens group 41 by the two motors for implementing the diopter compensation.

With reference to fig. 1, the present embodiment further provides a method for driving the optical lens group, where the optical lens group includes an entrance pupil 50, a scanning lens group 40, an intermediate image plane 30, an eyepiece group 20, an exit pupil 10, and a driving device (not shown) sequentially arranged along a first direction, where the scanning lens group 40 includes a second double cemented positive lens 423 and a front lens group 41 arranged along the first direction, and the driving device changes an air interval L1 between the second double cemented positive lens 423 and the front lens group 41 and an air interval L2 between the front lens group 41 and the eyepiece group 20 according to the received human eye visibility information, so that the L1 and L2 satisfy a preset relationship.

In this embodiment, the specific composition and driving manner of the driving device are not limited, and the purpose is to drive the relevant components so that L1 and L2 satisfy the preset relationship. The preset relationship between L1 and L2 is the relationship shown by the curve in fig. 12, and may also be the relationship between L1 and L2 pre-stored in the form of a formula or an array. The relationship between L1 and L2 may be calculated in real time by a specific calculation method, or may be a formula or a plurality of relationship arrays obtained by earlier-stage theoretical calculation or experiments, which is not limited herein.

It will be appreciated by those skilled in the art that the scanning lens assembly 40 and the optical lens assembly design thereof of the present invention are also applicable to non-scanning fundus imaging systems, such as conventional fundus cameras, which only need to add an illumination optical path and an image capturing optical path in front of the entrance pupil 50, but the details of the illumination optical path and the image capturing optical path of the conventional fundus camera are not essential to the present patent application, and those skilled in the art can add the required technical details based on the optical design of the above-described embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention as disclosed in the claims of the present invention.

Example two

Fig. 13 is a schematic structural view of a second optical lens assembly according to a second embodiment of the present invention. As shown in fig. 13, the second optical lens group 200 according to the second embodiment includes: the imaging system comprises an entrance pupil 50a, a scanning mirror group 40a, an intermediate image plane 30a, an eyepiece group 20a and an exit pupil 10a which are sequentially arranged along a first direction, wherein the scanning mirror group comprises a front mirror group 41a and a second double cemented positive lens 423a, and the front mirror group 41a is a positive lens composed of a first lens 411a and a second lens 412 a. The eyepiece group 20a includes a first cemented doublet positive lens 223a and a first aspheric positive lens 21a. The distance from the exit pupil 10a side surface of the first aspherical positive lens 21a to the exit pupil 10 is about 22.7mm, the distance (working distance) to the anterior surface of the cornea is 20mm, an ultra-wide angle of 100 ° is realized on the eye side, the spectral width is 445nm to 920nm as in the first embodiment, the paraxial magnification is 4.5, the diameter of the entrance pupil 50a is 6mm, corresponding to an exit pupil diameter of 1.3mm, and the image side (fundus) numerical aperture is 0.04..

FIG. 14 is a schematic view of a light Ray Fan aberration Ray Fan according to a second embodiment of the present invention; FIG. 15 is a diagram illustrating a wavefront aberration OPD according to a first embodiment of the present invention; FIG. 16 is a diagram illustrating the distribution of the RMS wavefront aberration in a field of view according to a second embodiment of the invention; fig. 17 is a schematic view of field curvature and astigmatism curves of a second embodiment of the invention; fig. 18 is a schematic view of an angle-enlarged distortion curve according to a second embodiment of the present invention. As shown in fig. 14 to 18, the overall optical performance is similar to that of the first embodiment, and the angular magnification distortion is increased.

In the second embodiment, the material of the first lens 411a and the second lens 412a may be flint glass. However, the number, material, position and power distribution of the lenses constituting the front lens group 41a can be configured very flexibly, the material is not limited to flint glass, the number of the lenses can be more than 2, and the lenses can be positive lenses or negative lenses, and can be single lenses or cemented lenses as long as the total effective focal length of the front lens group 41 is positive.

In the invention, the first embodiment and the second embodiment realize good chromatic aberration correction in a spectral range from blue light to near infrared with a width of 475nm, the lens is made of common stable glass materials, and the coefficients of acid resistance, alkali resistance, phosphorus resistance, dirt resistance, environment resistance and the like are all within 10. By relaxing the off-axis aberration of the intermediate image plane 30, the use of corrosive materials, such as ultra-low dispersion glass, anomalous dispersion glass, lanthanide LAF and LAK glass, etc., can be avoided.

The embodiments of the invention are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. An optical lens assembly for use in a color fundus imaging system, comprising:

an entrance pupil, a scanning mirror group, an intermediate image plane, an eyepiece group and an exit pupil arranged in sequence along a first direction,

the entrance pupil is positioned on the focal plane of the scanning mirror group at the side far away from the middle image plane;

the exit pupil is positioned on the focal plane of the eyepiece group on the side far away from the middle image plane, and is superposed with the pupil of the eye when the eye is detected;

the curvature radius of field curvature of the middle image plane in the meridian plane is less than 2 times of the effective focal length of the ocular lens group, and the field curvature bends to one side of the ocular lens group;

the effective focal length of the scanning lens group is larger than that of the eyepiece group, and the air space between the scanning lens group and the eyepiece group is larger than the transverse diameter of the middle image plane and smaller than the sum of the effective focal lengths of the scanning lens group and the eyepiece group.

2. The optical lens assembly of claim 1 wherein said eyepiece assembly comprises:

the first lens is an aspheric positive lens, the second lens is a negative lens, the third lens is a positive lens, and the second lens and the third lens form a first double-cemented positive lens.

3. The optical lens assembly of claim 2,

the first lens is a single-aspheric surface or double-aspheric surface positive lens;

one surface of the first lens, which is close to the second lens, is an even-order aspheric surface.

4. The optical lens assembly of claim 2,

the first lens is a positive meniscus lens which is bent towards the exit pupil.

5. The optical lens assembly of claim 2,

the first lens of the eyepiece group is made of a material with the refractive index larger than 1.5 and the Abbe number of 40-65;

the second lens of the eyepiece group is made of a material with the refractive index larger than 1.7 and the Abbe number smaller than 40;

the third lens of the eyepiece group is made of a material with the refractive index larger than 1.6 and the Abbe number between 40 and 65.

6. Optical lens group according to claim 2,

the effective focal length of the eyepiece group is between 20mm and 40 mm;

the distance from one side surface of the exit pupil of the first lens to the exit pupil is 10mm to 40 mm;

the effective focal length of the first lens of the eyepiece group is smaller than that of the first double cemented positive lens.

7. The optical lens assembly of claim 2, wherein said scanning lens assembly comprises:

a fifth lens element, a fourth lens element and a front lens element arranged in sequence along a first direction,

the front lens group comprises at least one positive lens;

the fifth lens is a negative lens, the fourth lens is a positive lens, and the fifth lens and the fourth lens form a second double-cemented positive lens.

8. The optical lens assembly of claim 7,

the fourth lens of the scanning lens group is made of crown glass material with the refractive index less than 1.7 and the Abbe number between 50 and 85;

the fifth lens of the scanning lens group is made of flint glass material with the refractive index of more than 1.7 and the Abbe number of less than 40.

9. A method for compensating the visual acuity of an optical lens group suitable for a color fundus image system is characterized in that,

the optical lens group comprises an entrance pupil, a scanning lens group, a middle image plane, an eyepiece group and an exit pupil which are sequentially arranged along a first direction, wherein the scanning lens group comprises a second double-cemented positive lens and a front lens group which are arranged along the first direction,

10. A driving method of optical lens set suitable for color fundus image system is characterized in that,

the optical lens group comprises an entrance pupil, a scanning lens group, a middle image plane, an eyepiece group, an exit pupil and a driving device which are sequentially arranged along a first direction, wherein the scanning lens group comprises a second double cemented positive lens and a front lens group which are arranged along the first direction,