JPS58127631A - Eye bottom camera - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ophthalmological examination device, and more particularly to a fundus camera with clear image quality that eliminates flare or ghost caused by harmful reflected and scattered light by the cornea and crystalline lens.

Fundus cameras have now become indispensable devices not only in ophthalmology but also in various medical fields, and as they have become more widespread, demands on the devices have changed to include wider viewing angles and smaller required pupil diameters.

The most difficult thing in fundus photography is to let light in and out through the limited pupil size, and how to remove flare and ghosts from the cornea and crystalline lens to take clear images. That's the point.

This becomes more difficult as the angle of view becomes wider or the required pupil diameter becomes smaller.

The ring illumination method has traditionally been used to perform all fundus photography, but this is a method in which the fundus is illuminated with a ring-shaped light beam near the cornea, and the photographing light beam is extracted from the center of the ring.
This method is used in most large fundus cameras. Normally, in order to prevent harmful flare and ghost light from being mixed into the fundus imaging light flux, it is important to sufficiently separate the illumination light flux and imaging light flux within the cornea and crystalline lens. - With the photographic aperture method, there is a limit to the angle of view that can be enlarged, so
il near the fundus side surface)! Original baffle (Original item on axis)
A method of forming an image was proposed in Utility Model Publication No. 56-8645-Q and others, and Japanese Patent Application Publication No. 56-14, which developed it into history.
No. 3139 (Japanese Patent Application No. 55-45960) has been proposed.

However, if a light-shielding baffle is provided in the illumination optical path, the illumination light 'iIi will be reduced accordingly, and the more the m element is removed by the IL in order to enhance the removal effect of the illumination light, the more the haα brightness will be reduced. Therefore, if the diameter of the pupil through which the illumination light flux passes is made smaller, the amount of light Y = M that illuminates the fundus may not be sufficient, and even if the angle of view is widened to illuminate a wider area, the amount of light will be insufficient. .

The purpose of the present invention is to reduce the required pupil diameter or expand the angle of view, and for this purpose, it provides an appropriate arrangement of a ring slit (sometimes only an aperture), a light-shielding baffle, and a photographic aperture. be. A second object of the present invention is to prevent the image from becoming difficult to see due to a large difference in brightness between the center and peripheral areas of the screen.

Hereinafter, the problems will be explained in detail using the prior art, and then the present invention will be explained in detail.

FIG. 1 shows a 4+Vi eye illuminated with ring illumination light, and an image of a ring slit light-shielding plate (a composite of an open aperture and a central light-shielding point) is formed on the iris. In this figure, only the light flux illuminating two off-axis locations of the fundus F is shown, but in reality, it is assumed that the light flux is continuously incident between them. Here, the diamond-shaped area a1 is a shadow part formed by the image of the central shading point, and if the photographing light flux emitted from the fundus (the light flux that passes through the photographic aperture and reaches the screen) passes through the area Bi, the illumination Even if the light is reflected or scattered by the cornea C or crystalline lens CL, there is no risk of it being mixed into the photographing light flux.

Figure 2 shows the photographing light flux that passes through the fundus, and the region A3 where the photographic light flux passes through the crystalline lens and the region M where the photographic light flux passes through the cornea C.
a2 increases as the photographing angle of view increases, and if these regions a2 and a3 deviate from the region a1 in FIG. 1, harmful light will be mixed into the photographing light beam.

Therefore, if the aforementioned light-shielding buckle image B (Fig. 1) is formed behind the crystalline lens, the shadow area will increase to include area a3, and harmful light will be removed, and another light-shielding baffle image will be formed on the cornea. By forming , it is possible to include area a2.

FIG. 3 shows the main components of the fundus camera according to the present invention, where fA) shows the observation and photographing system, and (B) shows the illumination system. Note that although the observation and photographing system and the illumination system are shown separately in the figure, the objective lens OL is actually shared. In the figure, other members 1 and 2 are a photographic aperture, 3 is an imaging lens, 4 is a finder, and 5 is a film. Also, 6 is a perforated mirror with an opening [ ] 6a, 7 is a relay lens, 8 and 1O are light shielding baffles, 9 is a ring slit a light plate, 11 is an optical path change 'd, 12 and 14 are condenser lenses, and 13 is a photographing Strobe light source for 15
is a white light source for observation, and here light source 13 or 1
The light beam from 5 is condensed by a condenser lens and illuminates the ring slit light shielding plate 9, and the light beam emitted from the ring slit 9a is imaged near the mirror surface of the perforated mirror 6 by the relay lens 7, and then focused by the objective lens OL. The image is formed near the iris and uniformly illuminates the fundus F. At that time, the first light shielding baffle 8 forms a shadow on the rear surface of the crystalline lens CL, and the second light shielding baffle 10
forms a shadow on the cornea C. .

On the other hand, the light beam scattered and reflected by the fundus is once imaged by the objective lens OL, and then regulated by the photographic aperture DI and 2, that is, the light beam passes through the shadow area formed by the ring slit light-shielding plate 9, the light-shielding baffle 8, and IO. The light passes through the photographic apertures 1 and 2, enters the imaging lens, undergoes imaging action there, and forms an image on the film 5, or is observed through the finder 4.

Next, we will explain in detail the interrelationships of the previously described configurations, but since it is difficult to explain the relationships if the related optical elements are separated from each other, we will use optical conjugate relationships to superimpose them in one place and explain the relationships. Make it.

In other words, the ring slit image formed within the subject's eye and the first
Observe the second shading baffle image, project it onto the photographing system, and place the projected images 9a', 8' next to the first and second photographic apertures Jl.
, 10'.

To explain the symbols used, in Fig. 4, F'
is the conjugate plane of the fundus, I( is the maximum off-axis height, h is the distance, O is on the axis b=I<s L' is conjugate to the posterior direction of the crystalline lens, ■'
is conjugate to the iris, C't is a position conjugate to the anterior surface of the cornea, and the plane F' and 71tHr,') distance = +F is L, +1
1] The distance HII between 'L' and '■' is m2, and '1' and 'C.
Let the distance of ' be l-111. Further, the total position of the first photographing aperture 1 is P, the distance between L' and P is el, and the distance between the first photographing aperture 1 and the second photographing aperture 2 is el.

Here, the aperture radius of the first and second shadow diaphragms 1 and 2 placed near the iris j1 and at positions conjugate with the cornea is rl, respectively.
, r2, the light beam from one point i (off-axis) in the photographing light beam passes through the respective photographic apertures in common.1JAt this time, on the posterior surface of the crystalline lens and the corneal surface, first, the shadow of the illumination light beam is Since a light shielding baffle with radius B1 was required on the plane L' conjugate to the posterior surface of the crystalline lens in order to pass the photographing light beam through the area where There is a restriction on the outer shape of 9a' that it must be greater than or equal to the radius BS.However, Br is the radius when the radius B on the surface L' is proportionally expanded to the surface ■' with the origin at 0 on the axis on the surface y. .

Note that if the radius is less than BI', there will be a central part of the fundus where the illumination light beam does not reach.

This shows that this control becomes stricter as the angle of view becomes wider.

The above requirements can be expressed as follows according to the geometrical similarity relationship.

Regarding the origin O, it□≧B/ =L + 7-B ・
...(1) With the intersection (hr-rl) of the optical axis and the tangent connecting point 1■ and the contact point of the first photographing diaphragm as the origin, B = L+, x /2 +
rl-(21 On the other hand, wJ2 photographing aperture is determined to be almost included in the second light-shielding baffle image located on the corneal conjugate plane, so if the radius of this baffle body is B2.The aperture radius ftr2 of the second photographing aperture is as follows. It is.

r2≦B2 ・−・・(4
) Apart from the problem of ghosts or flares mentioned above, the total energy, i.e. the scene distribution reaching the film plane (
(corresponding to vignetting), unless a certain limit is set, it will cause density unevenness on the film surface, so this will be corrected by means such as a filter. However, it would be more convenient if an easy-to-see image could be obtained without using these correction means.

In FIG. 4, when the second incident light beam image 10' is viewed from an off-axis height H, the apparent size at the posterior conjugate plane L' of the crystalline lens is a circle with a radius B, /; therefore, this radius 82'
As a result of being blocked by the circle and the first light-blocking baffle image 8', the light beam illuminating the height H is the outer diameter of the ring slit image 9a'
Then, the light flux passing through the surfaces 1'j[)t and b2 is obtained by subtracting the shaded area from the apparent size at L'. On the other hand, the light beam that illuminates the axial position 0 is a light beam that passes through the ring-shaped area b3.

Regarding the photographing light flux, the height H of the first photographing aperture l and the apparent area at the second photographing aperture position 2 viewed from the upper axis If O are the light fluxes passing through CI and C2, respectively. The distribution of total energy above is multiplied by the illumination and photographing light fluxes both on-axis and off-axis. When observing the screen, if the difference in brightness between the center and the periphery is less than 25 inches, it becomes difficult to see, so the following restrictions are added.

-(bl+b2) X C2-1 4'-,;-;〆1t-i1...
(5) Therefore, the combination of area areas should be selected so as to satisfy equation (5).

Next, regarding the inner diameter of the ring slit image, from the conditions of the imaging side, if it is larger than rl, there is no problem.The limit for achieving good illumination can be found by calculating 1 degree. First, area b in Figure 4
1 and b2 (the first light-shielding buffle image B1 and the apparent second
Given R6', which is tangent to the iris conjugate plane I' as seen from the off-axis height I, it is meaningless to make this circle smaller. I4 is the lower limit.

Note that by effectively using the shadows of the front and rear light shielding baffles or by using the holes of the perforated mirror, the central light shielding point of the ring slit a light plate can be omitted. The easiest way to use a light-shielding baffle is to use a light-transmitting plate, but it can also be substituted by bending the optical path with a mirror and making a hole in the mirror to allow the light to escape from that part. The ring slit a does not have to be provided before and after the light plate, but may be arranged at other conjugate positions.

According to the present invention described above, efficient illumination can be performed without mixing harmful light into the photographing light, so the required pupil diameter can be reduced compared to the conventional photographic angle of view, or even This has the effect of expanding the photographing angle of view while maintaining the pupil diameter, or reducing the pupil diameter and expanding the photographing angle of view at the same time.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between illumination light and the eye to be examined. FIG. 2 is a diagram showing the relationship between photographing light and the eye to be examined. FIG. 3 (13) is an optical cross-sectional view according to the embodiment. FIG. 4 is an optical sectional view showing the effect of the embodiment. In the figure, C is the cornea, ■ is the iris, CL is the crystalline lens, and C is the fundus.
OL is an objective lens, 1 is a first photographing aperture, 2 is a second photographing aperture, 8 is a first light-shielding baffle, 9 is a ring slit light-shielding plate, 10 is a second light-shielding buffle, F' ii fundus conjugate plane, L
′ is a surface conjugate to the posterior surface of the crystalline lens, 1′ is an iris conjugate surface, C′ is a corneal conjugate surface, L is the distance between Ir′ and surface L′, m m 2 is the distance between L′ and surface ■′, nl 1 is the distance between ■' and surface C', 4 is the distance between the first photographic aperture and L', 11 is the distance between the first photographic aperture and the second photographic aperture, and l-1 is the aperture radius of the first photographic aperture. , r2 is the aperture radius of the second photographing diaphragm, Bl is the radius of the projected image of the first light-shielding baffle, and B2 is the radius of the projected image of the second light-shielding baffle. Applicant Canon Co., Ltd. i-1 5

Claims (3)

[Claims] (1) Equipped with a main optical system for observing or photographing the fundus, or both, and an illumination optical system for illuminating the fundus, a light shielding body with a ring slit or an aperture and a plurality of light shielding baffles are arranged in the illumination optical system. In an apparatus in which a plurality of imaging units are arranged in the main optical system, the first light-shielding baffle is approximately conjugate to the posterior surface of the crystalline lens, and the outer diameter of the ring slit image formed and projected inside the eye of the light-shielding body is approximately conjugate to the posterior surface of the crystalline lens. The radius or the radius of the aperture image is ■ζ1. The radius of the first photographic aperture is rl, the distance between the surface conjugate to the posterior surface of the crystalline lens and the first photographic aperture is e21, the distance between the surface conjugate to the posterior surface of the crystalline lens and the conjugate surface of the fundus, The distance to the iris conjugate plane is m2. The maximum off-axis height on the fundus conjugate plane is h, L + m2 h - r 1 loss ≧ 1. X (L+12 X e 2 ” r
1), and further assuming that the maximum off-axis height of the conjugate plane of the fundus is the origin and the first photographing aperture is projected onto the conjugate plane of the cornea, the projected image is the second shading baffle image formed within the subject's eye. is projected onto the corneal conjugate plane, the projected second
If it deviates from the shading baffle image, set the radius of the first shading baffle image to B2. The radius of the second imaging aperture that is approximately conjugate to the cornea is r
2, a fundus camera that satisfies r2≦Bird. (2) When the first light-transmitting buckle image and the second light-blocking buckle image are viewed from the maximum off-axis height of the fundus, a circle whose diameter is the y point of the final image at the posterior crest of the crystalline lens is projected onto the iris conjugate plane. The fundus camera according to claim 1, wherein the dimension of this projected image is the lower limit of the inner diameter of the ring slit. (3) The main optical system for observing or photographing the fundus, and the illumination optical system for illuminating the J-class eye are both polarized, and a ring slit or a light-shielding plate with a full aperture and multiple light-shielding baffles are installed in the illumination optical system. In an apparatus in which a plurality of photographic apertures are arranged in the main optical system, the first! The original baffle is approximately conjugate to the posterior surface of the crystalline lens, and the outer diameter radius of the ring slit image or the radius of the aperture image formed and projected into the eye of the light shielding member is R1, and the radius of the first photographing aperture is rl, The distance between the surface conjugate to the posterior surface of the crystalline lens and the first photographic aperture is /ffi+
Calculate the distance between the plane conjugate to the posterior surface of the crystalline lens and the conjugate direction of the fundus, and the distance between the plane conjugate to the posterior surface of the crystalline lens and the iris conjugate plane m2. Letting h be the maximum off-axis height on the fundus conjugate plane, L + 1112 R1≧-11 ('nie', xez+rt)1,
L + /2 and assuming that the first imaging aperture is projected onto the corneal conjugate plane with the maximum off-axis height of the fundus conjugate plane as the origin, this projected image is formed within the eye to be examined. Assuming that the second light-exceeding buttful image is projected onto the corneal conjugate plane, the projected second
If it deviates from the light-shielding buckle image, change the radius of the second M-source baffle image to B2. The radius of the second imaging aperture that is approximately conjugate to the cornea is r
Assuming that r2≦bird is satisfied and that the area where the light flux that illuminates this position viewed from the maximum off-axis height of the fundus passes through the posterior surface of the crystalline lens is projected onto a plane conjugate to the posterior surface of the crystalline lens, then the projection formula l)1 +
b2, When we assume that the area where the light beam illuminating position 1a as viewed from the axis of the fundus passes through the iris is projected onto turtle 1, which is conjugate to the iris, the projected area is: , II bottom conjugate plane Assuming that the first imaging diaphragm is projected onto the corneal conjugate plane with the axial position as the origin, the projected aperture area of the first imaging diaphragm is el, and Assuming that one imaging aperture is projected onto the corneal conjugate plane,
A fundus camera that satisfies -(bl + b2)