Fundus camera imaging system

Abstract

The present invention relates to the field of optical equipment technology, and more particularly to a fundus camera imaging system comprising a first lens, a second lens, an aperture, a third lens, a filter, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a photosensitive component, arranged sequentially along the optical axis from the object side to the image side. By rationally allocating the focal lengths of the lenses in the imaging system and cooperating with each other, the present invention effectively corrects optical aberrations, eliminating the need for software post-processing and enabling the acquisition of high-quality fundus images.

Description

Technical Field

[0001] The present invention relates to the technical field of optical equipment, and in particular to a fundus camera imaging system. Background Art

[0002] A fundus camera is an ophthalmic imaging device used to examine and diagnose fundus diseases. It features mydriatic photography, non-mydriatic photography, red-light-free photography, and angiography. Its operating principle is this: the camera's illumination system emits infrared light for fundus observation. In a dark environment, infrared light is used to observe the fundus. Because the eye lacks visible light stimulation and is in darkness, the pupil naturally dilates. Once the camera is aimed and focused, the infrared light quickly switches to white or blue light, capturing a fundus image before the pupil constricts.

[0003] Existing fundus cameras often use simple optical lenses in their imaging systems, and then process the acquired fundus images through software. This imaging method has poor image quality and cannot truly restore the condition of the fundus tissue. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the related art. To this end, the present invention provides a fundus camera imaging system.

[0005] The present invention is achieved through the following technical solutions: A fundus camera imaging system includes a first lens, a second lens, an aperture, a third lens, a filter, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a photosensitive component, which are arranged in sequence from the object side to the image side along the optical axis; the object side surface of the first lens is convex, the image side surface of the first lens is concave, and the focal length of the first lens is negative; the object side surface of the second lens is convex, the image side surface of the second lens is convex, and the focal length of the second lens is positive; the object side surface of the third lens is concave, the image side surface of the second lens is convex, and the focal length of the third lens is positive; the object side surface of the fourth lens is convex, the image side surface of the fourth lens is concave, and the focal length of the fourth lens is positive; the object side surface of the fifth lens is concave , the image side surface of the fifth lens is concave, and the focal length of the fifth lens is negative; the object side surface of the sixth lens is concave, the image side surface of the sixth lens is convex, and the focal length of the sixth lens is positive; the object side surface of the seventh lens is concave, the image side surface of the seventh lens is concave, and the focal length of the seventh lens is negative; the object side surface of the eighth lens is concave, the image side surface of the eighth lens is concave, and the focal length of the eighth lens is negative; the object side surface of the ninth lens is convex, the image side surface of the ninth lens is convex, and the focal length of the ninth lens is positive; the object side surface of the tenth lens is convex, the image side surface of the tenth lens is convex, and the focal length of the tenth lens is positive; the object side surface of the eleventh lens is convex, the image side surface of the eleventh lens is convex, and the focal length of the eleventh lens is positive; the object side surface of the twelfth lens is convex, the image side surface of the twelfth lens is convex, and the focal length of the twelfth lens is positive.

[0006] Preferably, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens, and the twelfth lens are all glass spherical lenses.

[0007] Preferably, the imaging system satisfies the following relationship:

[0008] -50<TΤL / f<-30; -3<f1 / f2<-1;

[0009] -10<f3 / f<-6; -3<f4 / f5<-1;

[0010] -3<f6 / f7<-1; -1.5<f8 / f9<0;

[0011] -6<f 10 / f<-4;0<f 11 / f 12 <2;

[0012] Wherein, TTL represents the distance from the object side of the first lens to the imaging surface of the photosensitive component on the optical axis; f represents the total effective focal length of the imaging system; f1 represents the focal length of the first lens; f2 represents the focal length of the second lens; f3 represents the focal length of the third lens; f4 represents the focal length of the fourth lens; f5 represents the focal length of the fifth lens; f6 represents the focal length of the sixth lens; f7 represents the focal length of the seventh lens; f8 represents the focal length of the eighth lens; f9 represents the focal length of the ninth lens; f 10 Indicates the focal length of the tenth lens; f 11 Indicates the focal length of the eleventh lens; f 12 represents the focal length of the twelfth lens.

[0013] Preferably, the imaging system satisfies the following relationship:

[0014] Nd1≥1.8; Nd2≤1.7; Nd3≤1.7; Nd4≤1.8;

[0015] Nd5≥1.6; Nd6≤1.7; Nd7≥1.7; Nd8≥1.8;

[0016] Nd9≥1.5; Nd 10 ≤1.7; Nd 11 ≥1.8; Nd 12 ≤1.7;

[0017] Wherein, Nd1 represents the refractive index of the first lens; Nd2 represents the refractive index of the second lens; Nd3 represents the refractive index of the third lens; Nd4 represents the refractive index of the fourth lens; Nd5 represents the refractive index of the fifth lens; Nd6 represents the refractive index of the sixth lens; Nd7 represents the refractive index of the seventh lens; Nd8 represents the refractive index of the eighth lens; Nd9 represents the refractive index of the ninth lens; Nd 10 Represents the refractive index of the tenth lens; Nd 11 Represents the refractive index of the eleventh lens; Nd 12 represents the refractive index of the twelfth lens.

[0018] Preferably, the imaging system satisfies the following relationship:

[0019] Vd1>23; Vd2<50; Vd3>50; Vd4<50;

[0020] Vd5>30; Vd6>50; Vd7<30; Vd8<30;

[0021] Vd9>60;Vd 10 >50; Vd 11 <30;Vd 12 >50;

[0022] Wherein, Vd1 represents the Abbe number of the first lens; Vd2 represents the Abbe number of the second lens; Vd3 represents the Abbe number of the third lens; Vd4 represents the Abbe number of the fourth lens; Vd5 represents the Abbe number of the fifth lens; Vd6 represents the Abbe number of the sixth lens; Vd7 represents the Abbe number of the seventh lens; Vd8 represents the Abbe number of the eighth lens; Vd9 represents the Abbe number of the ninth lens; Vd 10 Vd represents the dispersion coefficient of the tenth lens; 11 Vd represents the Abbe number of the eleventh lens; 12 represents the Abbe coefficient of the twelfth lens.

[0023] Preferably, the imaging system satisfies the following relationship:

[0024] (d 23 +d 34 +d 45 +d 56 +d 67 +d 78 +d 89 +d 910 +d 1112 +d 1213 +d 1314 ) / TTL<1.5;

[0025] (T1+T2+T3+T4+T5+T6+T7+T8+T9+T 10 +T 11 +T 12 +T 13 ) / TTL<0.5;

[0026] BFL / TTL<0.5;

[0027] Among them, d 23 Indicates the air spacing distance between the second lens and the aperture; d 34 Indicates the air distance between the aperture and the third lens; d 45 Indicates the air spacing distance between the third lens and the filter; d 56 Indicates the air spacing distance between the filter and the fourth lens; d 67 represents the air spacing distance between the fourth lens and the fifth lens; d 78 represents the air spacing distance between the fifth lens and the sixth lens; d 89 represents the air spacing distance between the sixth lens and the seventh lens; d 910 represents the air spacing distance between the seventh lens and the eighth lens; d 1112 represents the air spacing distance between the ninth lens and the tenth lens; d 1213represents the air spacing distance between the tenth lens and the eleventh lens; d 1314 represents the air gap between the eleventh lens and the twelfth lens; BFL represents the air gap between the twelfth lens and the photosensitive component; T1 represents the center thickness of the first lens, T2 represents the center thickness of the second lens, T3 represents the center thickness of the third lens, T4 represents the center thickness of the filter, T5 represents the center thickness of the fourth lens, T6 represents the center thickness of the fifth lens, T7 represents the center thickness of the sixth lens, T8 represents the center thickness of the seventh lens, T9 represents the center thickness of the eighth lens, T 10 Indicates the center thickness of the ninth lens, T 11 represents the center thickness of the tenth lens, T 12 Indicates the center thickness of the eleventh lens, T 13 represents the center thickness of the twelfth lens, and TTL represents the distance from the object side of the first lens to the imaging surface of the photosensitive component on the optical axis.

[0028] Preferably, the photosensitive component includes a photosensitive chip switching device, a color photosensitive chip and a black-and-white photosensitive chip, and the color photosensitive chip and the black-and-white photosensitive chip are both installed in the photosensitive chip switching device.

[0029] Preferably, a side of the color photosensitive chip close to the twelfth lens and a side of the black and white photosensitive chip close to the twelfth lens are both provided with protective glass.

[0030] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0031] The present invention rationally distributes the focal lengths of the lenses of the imaging system. With the cooperation of the lenses, optical aberrations can be well corrected, and high-quality fundus images can be obtained without the need for image post-processing through software. All lenses are glass spherical lenses. Compared with optical resin materials, optical glass has high light transmittance and low dispersion coefficient at high refractive index, making it easy to correct aberrations and having stable physical and chemical properties. Compared with aspheric lenses, spherical lenses are easy to process and have low cost. Rational distribution of the refractive index of each lens is conducive to reducing the size of the lens, and under reasonable focal length distribution, aberrations such as spherical aberration and coma can be well corrected. By limiting the dispersion coefficient of each lens, dispersion caused by different refractive indices at different wavelengths can be compensated. , can reduce the secondary spectrum, has good chromatic aberration correction ability within the visible light range, and can improve the clarity of the imaging system; under the premise of ensuring the optical performance of the imaging system, by designing a reasonable air spacing distance between lenses and controlling the thickness of each lens, it is beneficial to correct aberrations and reduce the total length of the imaging system; in addition, by synchronously moving the third lens to the twelfth lens, the need for focusing the imaging system in the range of -25D to +25D of the eye's refractive media can be met; when the black and white photosensitive chip is in the optical axis position, the imaging system can directly output black and white fundus phases. Compared with converting color fundus phases into black and white fundus phases through software, the contrast of the fundus phase can be relatively enhanced, the image details are good and the three-dimensional sense is strong, and the interference of red reflected light from the fundus is reduced.

[0032] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of the present invention.

[0034] Figure 2 It is the MTF curve of the imaging system.

[0035] In the figure: 1. first lens; 2. second lens; 3. aperture; 4. third lens; 5. filter; 6. fourth lens; 7. fifth lens; 8. sixth lens; 9. seventh lens; 10. eighth lens; 11. ninth lens; 12. tenth lens; 13. eleventh lens; 14. twelfth lens; 15. photosensitive component. DETAILED DESCRIPTION

[0036] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0037] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0038] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0039] like Figure 1 As shown, the present invention provides a fundus camera imaging system, comprising a first lens 1, a second lens 2, an aperture 3, a third lens 4, a filter 5, a fourth lens 6, a fifth lens 7, a sixth lens 8, a seventh lens 9, an eighth lens 10, a ninth lens 11, a tenth lens 12, an eleventh lens 13, a twelfth lens 14 and a photosensitive component 15, which are arranged in sequence from the object side to the image side along the optical axis.

[0040] The object side surface of the first lens is convex, the image side surface of the first lens is concave, and the focal length of the first lens is negative; the object side surface of the second lens is convex, the image side surface of the second lens is convex, and the focal length of the second lens is positive; the first lens and the second lens together constitute a first cemented lens, wherein the first lens is a meniscus lens with a negative focal length, which can increase the focal length of the first cemented lens, reduce the numerical aperture of the incident light, and increase the field of view angle; the second lens can make the light passing through the first lens deflected at a large angle, thereby relatively reducing the size of the rear lens, which is conducive to reducing the volume of the imaging system.

[0041] An aperture for limiting the light beam is provided between the second lens and the third lens, which can improve the imaging quality, facilitate the collection of effective light, and reduce the aperture of the lens.

[0042] The object side of the third lens is concave, the image side of the second lens is convex, and the focal length of the third lens is positive, which can properly converge the front light and make the light smoothly transition to the rear optical system.

[0043] A filter is provided between the third lens and the fourth lens to eliminate stray light.

[0044] The object side surface of the fourth lens is convex, the image side surface of the fourth lens is concave, and the focal length of the fourth lens is positive, so that the front light is properly converged, reducing the angle between the light and the optical axis, which is conducive to reducing the volume of the imaging system.

[0045] The object side surface of the fifth lens is concave, the image side surface of the fifth lens is concave, and the focal length of the fifth lens is negative, which can appropriately deflect the front light and smoothly enter the rear optical system.

[0046] The object side surface of the sixth lens is concave, the image side surface of the sixth lens is convex, and the focal length of the sixth lens is positive, which can properly converge the front light and eliminate part of the aberration field curvature.

[0047] The object side surface of the seventh lens is concave, the image side surface of the seventh lens is concave, and the focal length of the seventh lens is negative, which can properly diverge the front light, increase the numerical aperture, and shorten the working distance.

[0048] The object side surface of the eighth lens is concave, the image side surface of the eighth lens is concave, and the focal length of the eighth lens is negative; the object side surface of the ninth lens is convex, the image side surface of the ninth lens is convex, and the focal length of the ninth lens is positive. The eighth lens and the ninth lens together constitute a second cemented lens, which can reduce system chromatic aberration.

[0049] The object side surface of the tenth lens is convex, the image side surface of the tenth lens is convex, and the focal length of the tenth lens is positive, which can converge the light in front, which is beneficial to reducing the aperture of the imaging system.

[0050] The object side surface of the eleventh lens is convex, the image side surface of the eleventh lens is convex, and the focal length of the eleventh lens is positive, which can converge the front light and is conducive to reducing the aperture of the imaging system.

[0051] The object side surface of the twelfth lens is convex, and the image side surface of the twelfth lens is convex. The focal length of the twelfth lens is positive, which can converge the light in front, which is beneficial to reducing the aperture of the imaging system, converging the light quickly, and reducing the working distance.

[0052] It should be noted that the “object side” mentioned in the above text refers to the side of the corresponding lens away from the photosensitive component; the “front” mentioned in the above text refers to the side of the corresponding lens away from the photosensitive component; the “image side” mentioned in the above text refers to the side of the corresponding lens close to the photosensitive component; and the “rear” mentioned in the above text refers to the side of the corresponding lens close to the photosensitive component.

[0053] This imaging system can effectively correct optical aberrations by rationally allocating the focal lengths of the lenses and cooperating with each other, eliminating the need for software-based image post-processing and enabling high-quality fundus images to be obtained.

[0054] According to the above technical solution, further, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens, and the twelfth lens are all glass spherical lenses. Compared with optical resin materials, optical glass has high light transmittance, a low Abbe number at high refractive index, is easy to correct aberrations, and has stable physical and chemical properties. Compared with aspheric lenses, spherical lenses are easy to process and have low cost.

[0055] According to the above technical solution, further, the imaging system satisfies the following relationship:

[0056] -50<TΤL / f<-30; -3<f1 / f2<-1;

[0057] -10<f3 / f<-6; -3<f4 / f5<-1;

[0058] -3<f6 / f7<-1; -1.5<f8 / f9<0;

[0059] -6<f 10 / f<-4;0<f 11 / f 12 <2;

[0060] Wherein, TTL represents the distance from the object side of the first lens to the imaging surface of the photosensitive component on the optical axis; f represents the total effective focal length of the imaging system; f1 represents the focal length of the first lens; f2 represents the focal length of the second lens; f3 represents the focal length of the third lens; f4 represents the focal length of the fourth lens; f5 represents the focal length of the fifth lens; f6 represents the focal length of the sixth lens; f7 represents the focal length of the seventh lens; f8 represents the focal length of the eighth lens; f9 represents the focal length of the ninth lens; f 10 Indicates the focal length of the tenth lens; f 11 Indicates the focal length of the eleventh lens; f 12 represents the focal length of the twelfth lens.

[0061] By limiting -50<TTL / f<-30, the total length of the imaging system can be shortened and the volume of the imaging system can be reduced while the total effective focal length of the imaging system is relatively short; and the short focal length can shorten the working distance, allowing light to converge quickly and meet the imaging range of the photosensitive component.

[0062] By limiting -3<f1 / f2<-1, the first lens can have a longer focal length, and the focal length of the second lens cannot be too short, so as to avoid excessive light deflection angle and cause significant changes in aberrations.

[0063] By limiting -10<f3 / f<-6, the third lens can have a longer focal length, so that the angle of light deflection will not be too large, thereby avoiding the introduction of excessive aberrations.

[0064] By limiting the range of -3<f4 / f5<-1 and -3<f6 / f7<-1, the focal lengths of the fourth and fifth lenses, and the focal lengths of the sixth and seventh lenses can be appropriately proportioned, so that light can smoothly transition to the rear optical system and avoid excessive light deflection angles.

[0065] By limiting f8 / f9 to -1.5 < 0 and rationally configuring the focal length ratio of the eighth lens and the ninth lens, the chromatic aberration and distortion of the imaging system can be reduced, while the light can be diverged, the total effective focal length of the imaging system can be reduced, and the working distance can be shortened.

[0066] By limiting -6<f 10 / f<-4, the tenth lens can have a longer focal length, balancing the spherical aberration, coma and astigmatism produced by the negative focal length lens in front.

[0067] By limiting 0<f 11 / f 12 <2, rationally configure the ratio of the eleventh lens and the twelfth lens to deflect and converge the light to the photosensitive component, thereby reducing the working distance.

[0068] According to the above technical solution, further, the imaging system satisfies the following relationship:

[0069] Nd1≥1.8; Nd2≤1.7; Nd3≤1.7; Nd4≤1.8;

[0070] Nd5≥1.6; Nd6≤1.7; Nd7≥1.7; Nd8≥1.8;

[0071] Nd9≥1.5; Nd 10 ≤1.7; Nd 11 ≥1.8; Nd 12 ≤1.7;

[0072] Wherein, Nd1 represents the refractive index of the first lens; Nd2 represents the refractive index of the second lens; Nd3 represents the refractive index of the third lens; Nd4 represents the refractive index of the fourth lens; Nd5 represents the refractive index of the fifth lens; Nd6 represents the refractive index of the sixth lens; Nd7 represents the refractive index of the seventh lens; Nd8 represents the refractive index of the eighth lens; Nd9 represents the refractive index of the ninth lens; Nd 10 Represents the refractive index of the tenth lens; Nd 11 Represents the refractive index of the eleventh lens; Nd 12 represents the refractive index of the twelfth lens. The first, second, fourth, seventh, eighth, ninth, and eleventh lenses all utilize relatively high refractive indices, which can increase the light deflection angle, facilitate lens size reduction, and, with a reasonable focal length distribution, effectively correct aberrations such as spherical aberration and coma. It should be noted that for those skilled in the art, a refractive index below 1.5 is considered low. A refractive index close to 1.7 or 1.8 is considered high.

[0073] According to the above technical solution, further, the imaging system satisfies the following relationship:

[0074] Vd1>23; Vd2<50; Vd3>50; Vd4<50;

[0075] Vd5>30; Vd6>50; Vd7<30; Vd8<30;

[0076] Vd9>60;Vd 10 >50; Vd 11 <30;Vd 12 >50;

[0077] Wherein, Vd1 represents the Abbe number of the first lens; Vd2 represents the Abbe number of the second lens; Vd3 represents the Abbe number of the third lens; Vd4 represents the Abbe number of the fourth lens; Vd5 represents the Abbe number of the fifth lens; Vd6 represents the Abbe number of the sixth lens; Vd7 represents the Abbe number of the seventh lens; Vd8 represents the Abbe number of the eighth lens; Vd9 represents the Abbe number of the ninth lens; Vd 10 Vd represents the dispersion coefficient of the tenth lens; 11 Vd represents the Abbe number of the eleventh lens; 12 Represents the Abbe number of the twelfth lens. Combining a high-Abbe number glass spherical lens with a low-Abbe number glass spherical lens can compensate for the dispersion caused by different refractive indices at different wavelengths, reduce the secondary spectrum, and provide better chromatic aberration correction within the visible light range, thereby improving the clarity of the imaging system.

[0078] According to the above technical solution, further, the imaging system satisfies the following relationship:

[0079] (d 23 +d 34 +d 45 +d 56 +d 67 +d 78 +d 89 +d 910 +d 1112 +d 1213 +d 1314 ) / TTL<1.5;

[0080] (T1+T2+T3+T4+T5+T6+T7+T8+T9+T 10 +T 11 +T 12 +T 13 ) / TTL<0.5;

[0081] BFL / TTL<0.5;

[0082] Among them, d 23 Indicates the air spacing distance between the second lens and the aperture; d 34 Indicates the air distance between the aperture and the third lens; d 45 Indicates the air spacing distance between the third lens and the filter; d 56 Indicates the air spacing distance between the filter and the fourth lens; d 67 represents the air spacing distance between the fourth lens and the fifth lens; d 78 represents the air spacing distance between the fifth lens and the sixth lens; d 89 represents the air spacing distance between the sixth lens and the seventh lens; d910 represents the air spacing distance between the seventh lens and the eighth lens; d 1112 represents the air spacing distance between the ninth lens and the tenth lens; d 1213 represents the air spacing distance between the tenth lens and the eleventh lens; d 1314 represents the air gap between the eleventh lens and the twelfth lens; BFL represents the air gap between the twelfth lens and the photosensitive component; T1 represents the center thickness of the first lens, T2 represents the center thickness of the second lens, T3 represents the center thickness of the third lens, T4 represents the center thickness of the filter, T5 represents the center thickness of the fourth lens, T6 represents the center thickness of the fifth lens, T7 represents the center thickness of the sixth lens, T8 represents the center thickness of the seventh lens, T9 represents the center thickness of the eighth lens, T 10 Indicates the center thickness of the ninth lens, T 11 represents the center thickness of the tenth lens, T 12 Indicates the center thickness of the eleventh lens, T 13 represents the center thickness of the twelfth lens, and TTL represents the distance along the optical axis from the object side of the first lens to the imaging surface of the photosensitive component. While ensuring the optical performance of the imaging system, properly designing the air spacing between lenses and controlling the thickness of each lens facilitates aberration correction and reduces the overall length of the imaging system. Furthermore, by synchronously shifting the third through twelfth lenses, the imaging system can meet the focusing requirements of the eye's refractive media within the range of -25D to +25D.

[0083] According to the above technical solution, the photosensitive component further includes a photosensitive chip switching device, a color photosensitive chip, and a black-and-white photosensitive chip. The color photosensitive chip and the black-and-white photosensitive chip are both mounted on the photosensitive chip switching device. The photosensitive chip switching device can be used to switch the color photosensitive chip or the black-and-white photosensitive chip to the optical axis position as needed. It should be noted that the photosensitive chip switching device is a conventional device in the art and will not be described in detail here.

[0084] When the color photosensitive chip is in the optical axis position, the imaging system can output color fundus images, which can clearly restore the true color of the fundus; when the black and white photosensitive chip is in the optical axis position, the imaging system can directly output black and white fundus images. Compared with converting the color fundus images into black and white fundus images through software, the contrast of the fundus images can be relatively enhanced, the image details are good and the three-dimensional sense is strong, and the interference of red reflected light from the fundus is reduced.

[0085] According to the above technical solution, further, a side of the color photosensitive chip close to the twelfth lens and a side of the black and white photosensitive chip close to the twelfth lens are both provided with protective glass for protecting the corresponding photosensitive chips.

[0086] Specifically, when d23 =170mm, d 34 =6mm,d 45 =5mm,d 56 =16mm,d 78 =11mm,d 67 =2mm,d 89 =1.5mm,d 910 =2mm,d 1112 =0.8mm,d 1213 =0.5mm,d 1314 =0.3mm, BFL=20mm, and the other parameters of the imaging system meet the following table:

[0087]

[0088] The MTF curve of the imaging system is as follows: Figure 2 As shown in the figure, curve AT is the curve of the modulus of the optical transfer function in the meridional direction at a field of view angle of 0°, and curve AS is the curve of the modulus of the optical transfer function in the sagittal direction at a field of view angle of 0°. In this embodiment, curve AT and curve AS coincide with each other. Curve BT is the curve of the modulus of the optical transfer function in the meridional direction at a field of view angle of 32°, and curve BS is the curve of the modulus of the optical transfer function in the sagittal direction at a field of view angle of 32°. Curve CT is the curve of the modulus of the optical transfer function in the meridional direction at a field of view angle of 48°, and curve CS is the curve of the modulus of the optical transfer function in the sagittal direction at a field of view angle of 48°. It can be seen that when the spatial frequency reaches 100 line pairs / mm, the minimum value of the modulus of the optical transfer function is above 0.15, which can well meet the imaging requirements.

[0089] The present invention rationally distributes the focal lengths of the lenses of the imaging system. With the cooperation of the lenses, optical aberrations can be well corrected, and high-quality fundus images can be obtained without the need for image post-processing through software. All lenses are glass spherical lenses. Compared with optical resin materials, optical glass has high light transmittance and low dispersion coefficient at high refractive index, making it easy to correct aberrations and having stable physical and chemical properties. Compared with aspheric lenses, spherical lenses are easy to process and have low cost. Rational distribution of the refractive index of each lens is conducive to reducing the size of the lens, and under reasonable focal length distribution, aberrations such as spherical aberration and coma can be well corrected. By limiting the dispersion coefficient of each lens, dispersion caused by different refractive indices at different wavelengths can be compensated. , can reduce the secondary spectrum, has good chromatic aberration correction ability within the visible light range, and can improve the clarity of the imaging system; under the premise of ensuring the optical performance of the imaging system, by designing a reasonable air spacing distance between lenses and controlling the thickness of each lens, it is beneficial to correct aberrations and reduce the total length of the imaging system; in addition, by synchronously moving the third lens to the twelfth lens, the need for focusing the imaging system in the range of -25D to +25D of the eye's refractive media can be met; when the black and white photosensitive chip is in the optical axis position, the imaging system can directly output black and white fundus phases. Compared with converting color fundus phases into black and white fundus phases through software, the contrast of the fundus phase can be relatively enhanced, the image details are good and the three-dimensional sense is strong, and the interference of red reflected light from the fundus is reduced.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A fundus camera imaging system, characterized in that: The invention comprises a first lens, a second lens, an aperture, a third lens, a filter, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens and a photosensitive component which are arranged in sequence from the object side to the image side along the optical axis; the object side surface of the first lens is convex, the image side surface of the first lens is concave, and the focal length of the first lens is negative; the object side surface of the second lens is convex, the image side surface of the second lens is convex, and the focal length of the second lens is positive; the object side surface of the third lens is concave, the image side surface of the third lens is convex, and the focal length of the third lens is positive; the object side surface of the fourth lens is convex, the image side surface of the fourth lens is concave, and the focal length of the fourth lens is positive; the object side surface of the fifth lens is concave, the image side surface of the fifth lens is concave, and the focal length of the fifth lens is positive. The focal length of the fifth lens is negative; the object side surface of the sixth lens is concave, the image side surface of the sixth lens is convex, and the focal length of the sixth lens is positive; the object side surface of the seventh lens is concave, the image side surface of the seventh lens is concave, and the focal length of the seventh lens is negative; the object side surface of the eighth lens is concave, the image side surface of the eighth lens is concave, and the focal length of the eighth lens is negative; the object side surface of the ninth lens is convex, the image side surface of the ninth lens is convex, and the focal length of the ninth lens is positive; the object side surface of the tenth lens is convex, the image side surface of the tenth lens is convex, and the focal length of the tenth lens is positive; the object side surface of the eleventh lens is convex, the image side surface of the eleventh lens is convex, and the focal length of the eleventh lens is positive; the object side surface of the twelfth lens is convex, the image side surface of the twelfth lens is convex, and the focal length of the twelfth lens is positive.

2. The fundus camera imaging system according to claim 1, characterized in that: The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens and the twelfth lens are all glass spherical lenses.

3. The fundus camera imaging system according to claim 2, characterized in that: The imaging system satisfies the following relationship: ； ； ； ； ； ； ； ； in, represents the distance from the object side of the first lens to the imaging surface of the photosensitive component on the optical axis; Represents the total effective focal length of the imaging system; represents the focal length of the first lens; represents the focal length of the second lens; represents the focal length of the third lens; represents the focal length of the fourth lens; represents the focal length of the fifth lens; represents the focal length of the sixth lens; represents the focal length of the seventh lens; represents the focal length of the eighth lens; represents the focal length of the ninth lens; represents the focal length of the tenth lens; represents the focal length of the eleventh lens; represents the focal length of the twelfth lens.

4. The fundus camera imaging system according to claim 2, characterized in that: The imaging system satisfies the following relationship: ； ； ； ； ； ； ； ； ； ； ； ； in, represents the refractive index of the first lens; represents the refractive index of the second lens; represents the refractive index of the third lens; represents the refractive index of the fourth lens; represents the refractive index of the fifth lens; represents the refractive index of the sixth lens; represents the refractive index of the seventh lens; represents the refractive index of the eighth lens; represents the refractive index of the ninth lens; represents the refractive index of the tenth lens; represents the refractive index of the eleventh lens; represents the refractive index of the twelfth lens.

5. The fundus camera imaging system according to claim 2, characterized in that: The imaging system satisfies the following relationship: ； ； ； ； ； ； ； ； ； ； ； ； in, represents the Abbe coefficient of the first lens; represents the Abbe coefficient of the second lens; represents the Abbe coefficient of the third lens; represents the Abbe coefficient of the fourth lens; represents the Abbe coefficient of the fifth lens; represents the Abbe coefficient of the sixth lens; represents the Abbe coefficient of the seventh lens; represents the Abbe coefficient of the eighth lens; represents the Abbe coefficient of the ninth lens; represents the Abbe coefficient of the tenth lens; represents the Abbe coefficient of the eleventh lens; represents the Abbe coefficient of the twelfth lens.

6. The fundus camera imaging system according to claim 2, characterized in that: The imaging system satisfies the following relationship: ； ； ； in, Indicates the air spacing distance between the second lens and the aperture; Indicates the air spacing distance between the aperture and the third lens; Indicates the air spacing distance between the third lens and the filter; Indicates the air spacing distance between the filter and the fourth lens; represents the air spacing distance between the fourth lens and the fifth lens; represents the air spacing distance between the fifth lens and the sixth lens; represents the air spacing distance between the sixth lens and the seventh lens; represents the air spacing distance between the seventh lens and the eighth lens; represents the air spacing distance between the ninth lens and the tenth lens; represents the air spacing distance between the tenth lens and the eleventh lens; represents the air spacing distance between the eleventh lens and the twelfth lens; represents the air spacing distance between the twelfth lens and the photosensitive component; represents the center thickness of the first lens, represents the center thickness of the second lens, represents the center thickness of the third lens, Indicates the center thickness of the filter, represents the center thickness of the fourth lens, represents the center thickness of the fifth lens, represents the center thickness of the sixth lens, represents the center thickness of the seventh lens, represents the center thickness of the eighth lens, represents the center thickness of the ninth lens, represents the center thickness of the tenth lens, represents the center thickness of the eleventh lens, represents the center thickness of the twelfth lens, Represents the distance from the object side of the first lens to the imaging surface of the photosensitive component on the optical axis.

7. The fundus camera imaging system according to claim 1, characterized in that: The photosensitive component includes a photosensitive chip switching device, a color photosensitive chip and a black and white photosensitive chip, and the color photosensitive chip and the black and white photosensitive chip are both installed in the photosensitive chip switching device.

8. The fundus camera imaging system according to claim 7, characterized in that: The side of the color photosensitive chip close to the twelfth lens and the side of the black and white photosensitive chip close to the twelfth lens are both provided with protective glass.

Images