CN111436902B - Fundus camera optical system based on non-coaxial array illumination - Google Patents
Fundus camera optical system based on non-coaxial array illumination Download PDFInfo
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- CN111436902B CN111436902B CN202010339572.8A CN202010339572A CN111436902B CN 111436902 B CN111436902 B CN 111436902B CN 202010339572 A CN202010339572 A CN 202010339572A CN 111436902 B CN111436902 B CN 111436902B
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- 238000005286 illumination Methods 0.000 title claims abstract description 90
- 230000003287 optical effect Effects 0.000 title claims abstract description 46
- 238000003384 imaging method Methods 0.000 claims abstract description 71
- 210000002747 omentum Anatomy 0.000 claims description 12
- 230000004075 alteration Effects 0.000 claims description 11
- 230000000694 effects Effects 0.000 abstract description 10
- 230000005764 inhibitory process Effects 0.000 abstract description 2
- 210000004087 cornea Anatomy 0.000 description 8
- 238000010586 diagram Methods 0.000 description 7
- 238000000034 method Methods 0.000 description 5
- 210000001525 retina Anatomy 0.000 description 5
- 238000013461 design Methods 0.000 description 4
- 201000010099 disease Diseases 0.000 description 4
- 208000037265 diseases, disorders, signs and symptoms Diseases 0.000 description 4
- 208000006550 Mydriasis Diseases 0.000 description 3
- 238000012937 correction Methods 0.000 description 3
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012014 optical coherence tomography Methods 0.000 description 2
- 210000001747 pupil Anatomy 0.000 description 2
- 238000002310 reflectometry Methods 0.000 description 2
- 201000001320 Atherosclerosis Diseases 0.000 description 1
- 208000024172 Cardiovascular disease Diseases 0.000 description 1
- 208000002177 Cataract Diseases 0.000 description 1
- 208000010412 Glaucoma Diseases 0.000 description 1
- 206010020772 Hypertension Diseases 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000003745 diagnosis Methods 0.000 description 1
- 208000010125 myocardial infarction Diseases 0.000 description 1
- 230000003071 parasitic effect Effects 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 210000001210 retinal vessel Anatomy 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 230000009885 systemic effect Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 230000002792 vascular Effects 0.000 description 1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
- A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
- A61B3/12—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for looking at the eye fundus, e.g. ophthalmoscopes
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
- A61B3/0008—Apparatus for testing the eyes; Instruments for examining the eyes provided with illuminating means
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
- A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
- A61B3/14—Arrangements specially adapted for eye photography
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- Health & Medical Sciences (AREA)
- Medical Informatics (AREA)
- Biophysics (AREA)
- Ophthalmology & Optometry (AREA)
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- Heart & Thoracic Surgery (AREA)
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Abstract
The invention provides a fundus camera optical system based on non-coaxial array illumination, which comprises: an illumination system, an imaging system; the illumination system includes a plurality of illumination sources; the plurality of illumination sources are uniformly distributed around the main optical axis of the imaging system, the main optical axis of each illumination source is deflected 15 degrees with the main optical axis of the imaging system, the distance between the center point of the light outlet of each illumination source and the main optical axis of the imaging system is 7.5mm, the working distance of the illumination sources is 10mm, and the diameter of the light inlet of the imaging system is 26mm. The device realizes a good uniform lighting effect, well avoids the generation of stray light, and realizes a good stray light inhibition effect. The invention is mainly used in the technical field of ophthalmic medical equipment.
Description
Technical Field
The invention relates to the technical field of ophthalmic medical equipment, in particular to a fundus camera optical system based on non-coaxial array illumination.
Background
The fundus camera mainly comprises an illumination system, an imaging system and an image sensor, wherein the illumination system illuminates the retina of the fundus, and the imaging system images capillaries on the retina to the image sensor. The fundus camera can be used for checking and judging the influence of ophthalmic diseases and systemic diseases, such as glaucoma, cataract, hypertension, atherosclerosis, myocardial infarction, cardiovascular diseases and the like on the width, tortuosity, branch angle and other characteristics of retinal blood vessels. Compared with common clinical examination equipment such as an ophthalmoscope (Ophthalmoscope), a slit-lamp microscope (Slit lamp microscope), a scanning laser ophthalmoscope (SCANNING LASER ophthalmoscope), optical coherence tomography (Optical coherence tomography) and the like, the real-time noninvasive fundus imaging examination of a fundus camera has become one of the most economical and common medical optical examination means, and has important significance for diagnosis and prevention of ophthalmic diseases and vascular-related diseases. Among these, how to design an optical system that is simple, small in size, low in cost, and capable of achieving a good effect of suppressing stray light is a difficulty in designing an optical system of a fundus camera.
Disclosure of Invention
It is an object of the present invention to provide an optical system for a fundus camera based on non-coaxial array illumination, which solves one or more of the technical problems of the prior art, and at least provides an advantageous choice or creation.
The invention solves the technical problems as follows: an optical system of fundus camera based on non-coaxial array illumination comprises an illumination system and an imaging system; the illumination system includes a plurality of illumination sources; the plurality of illumination sources are uniformly distributed around the main optical axis of the imaging system, the main optical axis of each illumination source is deflected 15 degrees with the main optical axis of the imaging system, the distance between the center point of the light outlet of each illumination source and the main optical axis of the imaging system is 7.5mm, the working distance of the illumination sources is 10mm, and the diameter of the light inlet of the imaging system is 26mm.
Further, the wavelength range of the emitted light of the illumination source is located in the near infrared wavelength range. By emitting such light, the human eyes are insensitive, detection is convenient, and mydriasis-free illumination is realized.
Further, the wavelength of the emitted light of the illumination source is 940nm.
Further, the imaging system includes: the system comprises a omentum objective lens group and an imaging lens group, wherein the omentum objective lens group and the imaging lens group are arranged on a common optical axis, the omentum objective lens group is used for first imaging and correcting partial human eye aberration, and the imaging lens group is used for second imaging and correcting residual human eye aberration and system aberration. By means of twice correction, the aberration of human eyes is eliminated to the greatest extent.
Further, the field angle of view of the web objective group is 30 ° to 45 °, and the field angle of view of the imaging lens group is 65 °.
Further, the omentum objective lens group is Ran Sideng eyepiece lens group.
Further, the number of illumination sources is six.
The beneficial effects of the invention are as follows: the device realizes a good uniform lighting effect, well avoids the generation of stray light, and realizes a good stray light inhibition effect. The system has the advantages of simple design structure, small volume, good aberration correction effect and high imaging quality. By realizing the mydriasis-free shooting of retina, the purpose of noninvasive examination is achieved.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
fig. 1 is a light path diagram of the present fundus camera optical system;
FIG. 2 is a light path diagram of an illumination source;
FIG. 3 is a schematic diagram of the principle of the illumination source acting on reflected light from the cornea;
FIG. 4 is a schematic diagram of an imaging system;
FIG. 5 illustrates an MTF plot for an imaging system;
FIG. 6 is a point diagram of an imaging system;
fig. 7 shows a field curvature, distortion map of an imaging system.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.
In order that those skilled in the art will better understand the present invention, a detailed description of embodiments of the present invention will be provided below, with reference to the accompanying drawings, wherein it is apparent that the described embodiments are only some, but not all, embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, shall fall within the scope of the invention.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data used in this manner is intended to cover, where appropriate, a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements that are expressly listed or inherent to such process, method, article, or apparatus.
The invention will be described in detail below with reference to the drawings in connection with embodiments.
According to an embodiment of the present invention, fig. 1 provides a fundus camera optical system employing a non-coaxial annular array illumination mode, which is applied to a model of a human eye for convenience of description, for which a COMS photosensitive chip 600 is disposed on an image plane of an imaging system 800, and the COMS photosensitive chip 600 is used as an image sensor.
The construction system as shown in fig. 1 comprises: an illumination system 700, an imaging system 800; the illumination system comprises a plurality of illumination sources 200 (only two are shown in fig. 1); the plurality of illumination sources 200 are evenly distributed about a primary optical axis 810 of the imaging system 800. The illumination source 200 includes a beam splitter group and an LED point light source having a light emission angle of 30 ° and a working distance of 6.5mm, i.e., a distance between the LED point light source and the beam splitter group. The working distance of the illumination source 200, i.e. the distance between the center point of the light exit of the light homogenizing lens set and the cornea 110 of the human eye model, is instead 10 mm.
Referring to fig. 2, the primary optical axis 230 of each illumination source 200 is deflected from the primary optical axis 810 of the imaging system 800 by β, which is equal to 15 °, the distance between the center point of the light exit of each illumination source 200 and the primary optical axis 810 of the imaging system 800 is h, which is equal to 7.5mm, and the light entrance diameter of the imaging system 800 is 26mm. Wherein the imaging system 800 comprises: the system comprises a omentum objective lens group 400 and an imaging lens group 500 which are arranged on the common optical axis, wherein the omentum objective lens group 400 is used for first imaging and correcting partial human eye aberration, and the imaging lens group 500 is used for second imaging and correcting residual human eye aberration and system aberration.
The illumination system 700 includes six illumination sources 200, each illumination source 200 having a light homogenizing lens group and a point light source. Each lens group comprises two plano-convex lenses with positive focal power. Six illumination sources 200 are annularly distributed at the front end of the web objective 400. In the embodiment of the present invention, the optical design software ZEMAX is used to design multiple structures of the illumination source 200, and the surface of the cornea 110 of the human eye model is taken as a global coordinate reference plane, six illumination sources are evenly distributed 360 ° under the condition of being deflected by 15 ° and eccentric by 7.5mm relative to the main optical axis, and the multiple structure parameters of the illumination source 200 are shown in table 1. Wherein, config1 is the first illumination source, config1 is the second illumination source, config1 is the third illumination source, config1 is the fourth illumination source, config1 is the fifth illumination source, and Config1 is the sixth illumination source.
Table 1 spatial distribution data of illumination sources
| Operand | Config1 | Config2 | Config3 | Config4 | Config5 | Config6 |
| CATX | -15 | -15 | -15 | -15 | -15 | -15 |
| CADY | -7.5 | -7.5 | -7.5 | -7.5 | -7.5 | -7.5 |
| CATZ | 0 | 60 | 120 | 180 | 240 | 300 |
In some preferred embodiments, the illumination source 200 emits light in the near infrared band, i.e., the LED point light source emits light in the near infrared band, which makes the human eye insensitive and convenient to detect, and in some embodiments, the illumination source 200 emits light at 940nm.
As shown in fig. 3, since a plurality of illumination sources 200 are disposed around a main optical axis 810 of the imaging system 800, an annular light-emitting illumination system 700 is composed. In the illumination system 700, light emitted from the illumination sources 200 is incident on the surface of the cornea 110 at an angle such that reflected light 120 (stray light) from the surface of the cornea 110 is reflected at an angle, and the distance between the center point of the light exit of each illumination source 200 and the main optical axis 810 of the imaging system 800 is set by setting the deflection angle between each illumination source 200 and the main optical axis 810 of the imaging system 800. So that the reflected light 120 from the surface of the cornea 110 does not enter the imaging system 800, thereby achieving a parasitic light suppression effect.
In this embodiment, lighttools stray light analysis software is used to perform modeling analysis on fundus reflection stray light, when the power of a light source is set to be 100W and the divergence angle of a point light source is 30 °,1×10 6 light rays are traced, the surface reflectivity of the cornea 110 is 4%, the surface reflectivity of the omentum objective lens group 400 is 2%, and the detected energy on the CMOS photosensitive chip 600 is 0, which indicates that the stray light of the cornea 110 is totally overflowed from the imaging system 800.
Here, when the number of illumination sources 200 is six, the illumination effect is good. In the embodiment of the invention, the fundus illumination uniformity is modeled and analyzed by lighttools stray light analysis software, the power of a light source is set to be 100W, when the divergence angle of the light source is 30 degrees, 1X 10 6 light rays are tracked, according to the simulation result, the power density of the fundus central area is about 0.084W/mm 2, the maximum power density is 0.086W/mm 2, and the power density at the position with the radius of 85 percent in the illumination area of 30 degrees is about 0.070W/mm 2. According to the definition of uniformity UΦ center is the power density of the illumination center area, Φ 85％ is the power density of the illumination area at the radius of 85%, Φ max is the maximum power density in the illumination area, and u=83.7% is calculated, which indicates that the scheme of six illumination sources 200 in this embodiment can achieve a better fundus uniform illumination effect. With the above configuration, the total length of the illumination system in the embodiment of the present invention can be realized to be not more than 18mm. The size of the entire fundus camera optical system is reduced.
As shown in fig. 4, parameters of the respective optical elements in the optical path composed of a human eye model (Gullstrand-Le Grand), an imaging system 800, and a CMOS light-sensitive chip 600 are provided:
Data for mirror surfaces of imaging system 800
Such that the field angle of the web objective lens 400 is 30 ° to 45 °, and the field angle of the imaging lens 500 is 65 °. In this embodiment, using BASLER camera with pixel size of 5.5 μm×5.5 μm as CMOS light-sensitive chip 600, the resolution of retina 6 μm structure is required, and the limit resolution of imaging system 800 can be found to be 91lp/mm by the formula n=1000/2α (N is the limit resolution, α is the pixel size). By the formula ψ=1.22λ/D (ψ is the ratio of the pixel size D to the focal length f of the optical system, D is the entrance pupil diameter, λ is the center wavelength), a diffraction limited aperture value of 4.8 can be obtained. In this embodiment, the diameter of the light inlet of the web objective group is 26mm. With the above configuration of the imaging system 800, the overall length of the imaging system 800 is no greater than 75mm. The parameters of the final imaging system 800 are shown in table 3:
Table 3 parameters of the imaging system
| Wavelength (nm) | 935～945 |
| Fundus imaging range | ±5.24 |
| Retina resolution (mum) | 6 |
| Pupil diameter (mm) | 2 |
| Total length of system (mm) | ≤130 |
| Rate of distortion (%) | <5 |
| MTF value | >0.2@91lp/mm |
Fig. 5 is a graph of MTF of modulation transfer function of imaging system 800 according to an embodiment of the present invention, as shown in fig. 5, when the nyquist frequency is 911p/mm, the MTF value is greater than 0.2, satisfying the requirement of using BASLER cameras in the imaging system. Fig. 6 is a point diagram of an imaging system according to an embodiment of the present invention, and fig. 7 is a field curvature and distortion diagram of the imaging system according to an embodiment of the present invention. As shown in fig. 6 and 7, the airy disk radius is 8.602 μm, the maximum RMS radius is 4.135 μm, and the image quality is close to the diffraction limit. The field curvature of the full field is less than 0.2mm, and the distortion rate is less than 5%. The imaging system has good correction effect and high imaging quality.
Through the non-coaxial design of the illumination system 700 and the imaging system 800 and the six illumination sources 200 which are annularly arranged, the interference of stray light on the imaging system is effectively inhibited while a better uniform illumination effect is realized; the near infrared LED light source insensitive to human eyes is adopted, so that mydriasis treatment in the fundus photographing process is avoided. The total length of the whole illumination system 700 can be no more than 18mm, the total length of the imaging system 800 can be no more than 75mm, and the whole illumination system has the advantages of simple structure, small volume, low cost, handholding, portability and the like.
While the present invention has been described in considerable detail and with particularity with respect to the described embodiments, it is not intended to be limited to any such detail or embodiments or any particular embodiment, but is to be construed as providing broad interpretation of such claims by reference to the appended claims in view of the prior art so as to effectively encompass the intended scope of the invention. Furthermore, the foregoing description of the invention has been presented in its embodiments contemplated by the inventors for the purpose of providing a useful description, and for the purposes of providing a non-essential modification of the invention that may not be presently contemplated, may represent an equivalent modification of the invention.
Claims (7)
1. The fundus camera optical system based on non-coaxial array illumination is characterized by comprising an illumination system and an imaging system; the illumination system includes a plurality of illumination sources; the plurality of illumination sources are uniformly distributed around the main optical axis of the imaging system, the main optical axis of each illumination source is deflected 15 degrees with the main optical axis of the imaging system, the distance between the center point of the light outlet of each illumination source and the main optical axis of the imaging system is 7.5mm, the working distance of the illumination sources is 10mm, and the diameter of the light inlet of the imaging system is 26mm.
2. The fundus camera optical system based on non-coaxial array illumination of claim 1, wherein: the wavelength range of the emitted light of the illumination source is located in the near infrared wavelength range.
3. A fundus camera optical system based on non-coaxial array illumination according to claim 2, wherein: the wavelength of the emitted light of the illumination source is 940nm.
4. The fundus camera optical system based on non-coaxial array illumination of claim 1, wherein: the imaging system includes: the system comprises a omentum objective lens group and an imaging lens group, wherein the omentum objective lens group and the imaging lens group are arranged on a common optical axis, the omentum objective lens group is used for first imaging and correcting partial human eye aberration, and the imaging lens group is used for second imaging and correcting residual human eye aberration and system aberration.
5. The fundus camera optical system based on non-coaxial array illumination according to claim 4, wherein: the field angle of view of the omentum objective lens group is 30-45 degrees, and the field angle of view of the imaging lens group is 65 degrees.
6. The fundus camera optical system based on non-coaxial array illumination according to claim 4, wherein: the omentum objective lens group is Ran Sideng eyepiece lens group.
7. The fundus camera optical system based on non-coaxial array illumination of claim 1, wherein: the number of illumination sources is six.
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| CN104083145A (en) * | 2014-07-15 | 2014-10-08 | 温州雷蒙光电科技有限公司 | Fundus camera |
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