CN111084604A

CN111084604A - Fundus imaging system based on square rod illumination

Info

Publication number: CN111084604A
Application number: CN201911159117.3A
Authority: CN
Inventors: 王鑫; 封皓
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2019-11-22
Filing date: 2019-11-22
Publication date: 2020-05-01

Abstract

The invention discloses an eyeground imaging system based on square rod illumination, wherein a square spot imaging unit, a condenser group, an aperture diaphragm, a polaroid, a field diaphragm, a reflector, a field lens, a reflector and an eye objective are sequentially arranged from a light source side to an eyeground side in the eyeground illumination system; the light source forms a square light source after passing through the square rod, the square light source forms an image at the field diaphragm after passing through the condenser group for the first time, and then the square light spot is formed at the pupil position after sequentially passing through the polaroid, the reflector, the field lens, the reflector and the eye-catching objective lens.

Description

Fundus imaging system based on square rod illumination

Technical Field

The invention relates to medical treatment auxiliary equipment, in particular to an eyeground imaging system based on square bar illumination.

Background

The human eye is similar to a zoom lens in structure, the retina is equivalent to the negative plate of a camera and plays a vital role, and pathological changes of the retina seriously affect the normal life of a patient, and most of the pathological changes can be observed through a fundus camera. The only capillary vessels which can be directly observed in the human body are distributed on the fundus tissues of the human body, and doctors can diagnose many diseases such as diabetes, hypertension and the like through fundus images.

The eyeground of people can not give out light, and the condition of eyeground can only be observed to the external light source, and the pupil is as the light-passing hole of glasses, under the condition of not mydriasis, can only guarantee 3 ~ 4 mm's diameter, has restricted illuminance and the degree of consistency of illumination. In addition, when illuminating light irradiates the cornea of the eye, the illuminating light is reflected to an imaging light path, and the light intensity of the reflected light is multiple times of the fundus image information, so that the imaging quality is seriously influenced. There are two main approaches to solving the corneal reflection, the first is to use annular light illumination to remove the central ray that produces the corneal reflection by forming an annular spot in the pupil, but this approach reduces the light energy and uniformity of the illumination light. The second approach is to use a polarization switch to eliminate corneal reflections, which also reduces the light energy of the illumination. Since most of the current photoelectric receivers are square, a large amount of light energy is wasted in a round illumination area of the fundus oculi. In view of the above, it is necessary to provide a novel fundus illumination system.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a novel fundus camera lighting system capable of forming uniform square light spots on the fundus, and the system has higher light energy utilization rate and more uniform lighting effect.

The technical scheme of the invention is realized as follows:

an eyeground imaging system based on square rod illumination is characterized in that a square spot imaging unit, a condenser lens group, an aperture diaphragm, a polaroid, a field diaphragm, a reflector, a field lens, a reflector and an eye objective lens are sequentially arranged from a light source side to an eyeground side; wherein:

the square spot imaging unit consists of a square rod, a light source and a reflector;

the light source forms a square light source after passing through the square rod, the square light source forms a first image at the field diaphragm after passing through the condenser group, and then the square light spot is formed at the pupil position after sequentially passing through the polaroid, the reflector, the field lens, the reflector and the eye-catching objective lens.

The square spot forming process in the square spot imaging unit body comprises the following steps:

the light source converges the light emitted by the light source into the square rod through the arc reflector 13;

the light is totally reflected after entering the square rod, and a uniform square light source is formed at the other end of the square rod; wherein: the light source has a light emitting angle of 120 degrees, and the reflector 13 needs to ensure that the light source incident angle is larger than the critical angle of total reflection of the square rod.

The length-width ratio of the square bar is preferably 4: 3.

the square rod material is PMMA.

The field diaphragm and the aperture diaphragm are variable diaphragms, the change of the field diaphragm size can correspond to the conditions of different pupil sizes, and the change of the aperture diaphragm size can adjust the light intensity incident to the eye fundus.

The polarizer in combination with the polarizer of the imaging beam path may eliminate corneal reflections.

Advantageous effects

Compared with the prior art, the invention uses the square light source to replace the traditional circular light source, overcomes the defect of waste of the traditional light source illumination area, and greatly improves the utilization rate of light energy. The integral square rod is used as a light source shaping device, and uniform rectangular light spots are formed through multiple total reflections, so that the uniform illumination of the eyeground is facilitated, and the damage of light to the eyeground is reduced.

Drawings

Fig. 1 is a diagram showing the path of fundus illumination according to the present invention.

FIG. 2 is a schematic diagram of the illumination of a square rod of the present invention.

Fig. 3 is a simulation diagram of the illumination effect at the pupil position of the invention.

FIG. 4 is a simulation of the illumination effect at the fundus of the eye according to the present invention.

Detailed Description

The following description of the present invention will be explained in conjunction with the accompanying drawings so that those skilled in the art can understand the present invention.

As shown in fig. 1, the present invention is provided with a reflecting mirror 13, a light source 12, a square rod 11, a condenser group 10, an aperture stop 9, a polarizing plate 8, a field stop 7, a reflecting mirror 6, a field lens 5, a reflecting mirror 4, and an objective lens 3 in this order from the light source side to the fundus side.

The light source passes through the square bar 11 to form a uniform 4:3 square light spots.

The condenser lens 11 is used to form a primary light source image of the kohler illumination system, which is located at the aperture stop 7. The size of the image formed at the pupil can be controlled by controlling the size of the aperture stop 7.

The light can become the line polarization light when the polaroid 8 passes through, and the line polarization light becomes non-polarized light after being reflected by the retina, and the line polarization light that the cornea reflection comes can be filtered to the polaroid that is located the formation of image light path, and the light that comes through the retina reflection to eliminate the cornea reflection.

The field lens 5 is used to shorten the length of the optical system, and forms the second condenser lens of the Kohler illumination system together with the objective lens.

After passing through the objective lens, the light forms a clear 4:3 rectangular light spot on the pupil, and the length and the width of the pupil are 3.2mm and 2.4mm respectively under the condition that the size of the pupil is 4 mm.

As shown in fig. 2, the square rod is located at the second focal point of the ellipsoidal reflector 13, the light emitting angle of the light source 12 is 120 °, the square rod is located at the first focal point of the ellipsoidal reflector 13, and the diameter of the exit of the reflector 13 is 10 mm. The square rod 11 is made of organic glass, the refractive index of the organic glass is 1.49, the critical angle of total reflection is 42 degrees, when a light source is incident at 120 degrees, the reflection angle of light on the square rod is 48 degrees, and the requirement of total reflection is met.

The longer the square rod is, the higher the uniformity of the light when the light is emitted, but the transmission efficiency is reduced, and the length of the light for carrying out three times of total reflection is the optimal length.

As shown in FIG. 3, the illumination source forms a rectangular spot with a diagonal of about 4mm at the pupil, which can satisfy the requirement of non-mydriatic photography.

As shown in fig. 4, the light forms a uniform rectangular light spot on the fundus, the diagonal length is about 15mm, and the requirement of fundus detection can be met.

Claims

1. An eyeground imaging system based on square rod illumination is characterized in that a square spot imaging unit, a condenser group, an aperture diaphragm, a polaroid, a field diaphragm, a reflector, a field lens, a reflector and an eye objective are sequentially arranged from a light source side to an eyeground side in the eyeground illumination system; wherein:

the light source forms a square light source after passing through the square rod, the square light source forms an image at the field diaphragm after passing through the condenser group for the first time, and then the square light spot is formed at the pupil position after sequentially passing through the polaroid, the reflector, the field lens, the reflector and the eye-catching objective lens.

2. An eyeground imaging system based on square rod illumination as claimed in claim 1, characterized in that the square spot forming process in the square spot imaging unit body is as follows:

the light source converges the light emitted by the light source into the square rod through the arc reflector;

the light is totally reflected after entering the square rod, and a uniform square light source is formed at the other end of the square rod; wherein: the light emitting angle of the light source is 120 degrees, and the reflector needs to ensure that the incident angle of the light source is larger than the critical angle of total reflection of the square rod.

3. An eyeground imaging system based on square rod illumination as claimed in claim 1, characterized in that the square rod length to width ratio is preferably 4: 3.

4. an ocular fundus imaging system based on square rod illumination according to claim 1 characterized in that said square rod material is PMMA.

5. An eyeground imaging system based on square rod illumination as claimed in claims 1-4, characterized in that the field stop and aperture stop are variable diaphragms, the change of field stop size can cope with the situation of different pupil size, the change of aperture stop size can adjust the light intensity of the light incident to the eyeground.

6. An fundus imaging system according to claim 5 and based on square rod illumination, characterized in that said polarizer in combination with the polarizer of the imaging path eliminates corneal reflections.