JPS5869531A - Multiplication 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 ophthalmoscope imaging device, and more particularly to focusing of a fundus camera capable of variable magnification imaging or observation.

Eye examinations are carried out to aid in diagnosis to prevent disease, and photographs of the fundus, for example, can provide useful information.

In addition, as group photography for this purpose has become more widespread, there is a demand for a fundus camera with a wide field of view that can capture a wider range of images with fewer shots.
For patients for whom T can be assumed, a fundus camera that has a narrow field of view and can perform magnified imaging is required. In order to satisfy these two demands, there is a known device that enables wide-angle and narrow-angle photography by replacing the objective lens in the optical system of the fundus camera, but it takes time and effort to replace the objective lens. I'll do it,
Furthermore, there were many inconveniences, such as the need to align the optical axis of the eye to be examined and the objective lens, adjust the working distance, and readjust the focusing every time the objective lens was replaced. The present applicant previously proposed a fundus camera capable of zooming observation photography in Japanese Patent Application No. 53-49618 in an attempt to eliminate the above-mentioned difficulties.

Currently, there are two typical focusing methods for fundus cameras: moving the imaging surface and moving a part of the imaging optical system. However, in the case of a zoomable Hiko fundus camera, the focus σ depends on the diopter of each eye being examined.
The amount of movement in 11 varies depending on the selected zoom ratio, so
The method of moving the imaging lens 1j is not convenient. Therefore, in the embodiment described in the above-mentioned application, the focusing lens for focus correction is placed closer to the subject than the movable lens group for zooming. For example, even if you focus on an object point at a desired object distance and then zoom, in principle, it will be in focus in all zoom states.

Because the focusing lens moves along the optical axis, or when the focusing lens has negative refractive power, the off-axis photographing light flux that enters the movable lens group for zooming passes through a high position, so the movable lens group Also, the lens diameter of the relay lens group is increased, and as a result, each lens becomes thicker and the overall length becomes longer.

The purpose of the present invention is to make the optical system more compact, and in order to achieve this purpose, a fixed lens may be placed on the needle side of the photographic diaphragm. By doing so, the height of the chief ray passing through the variator which bears the main refractive power can be lowered, thereby making it possible to reduce the diameter of the constituent lenses, making each lens thinner, and making it easier to correct aberrations.

The present invention will be described in detail below with reference to the drawings.

In Figure 1, E indicates the eye to be examined, and If indicates the fundus. The objective lens 1 is a 1t/-i objective lens consisting of an abranatic lens and a biconvex lens made of three laminated lenses, and the objective lens 1 is placed a predetermined working distance away from the eye E to be examined. 2 is the shooting aperture,
Slightly in front of the photographic aperture 2, a light splitter (perforated mirror) m is obliquely installed for guiding the fundus illumination light beam to the photographing light beam. 1
6 shows a part of the optical axis of the illumination TP system, and the light source, relay lens, etc. are omitted.

Next, reference numeral 3 denotes the same lens, which has the function of reducing the image of the objective lens 1, and reduces the amount of movement of subsequent focusing members.

In this example, a positive refractive power is provided, but a negative refractive power can also be selected, and in that case, an imaginary one is formed. Reference numeral 2 denotes a variable magnification unit which has a zooming function and is composed of, in order, a negative variator (image plane compensation group) 4, a negative variator (focal length changing group) 5, and a positive fixed lens 6.

The variator 5 and the sensor 4 move during both rotations to achieve zooming, and the fixed lens 6 converts the paraxial ray emitted from the variator 4 into afocal light and emits it. And these compensator 4, variator 5, fixed lens 6
can be moved integrally in the optical axis direction, and by this insertion, a focusing lens is formed on the fundus If of the eye to be examined. In that case,
The compensator 4 and the variator 5 may occupy any position on the optical axis, and when they move together, a zoom tube and a fixed lens 6 that support the compensator 4 and the variator 5
It is better to slide the supporting lens barrel together from the outside. R is a relay lens section, which has the function of focusing the emitted light beam from the variable magnification section 2 onto the film F, and shortens the overall length by using a Galileo telephoto system (telephoto type) equipped with a positive lens 7 and a negative lens 8. do. As described above, the portion consisting of the objective lens 1 to the negative lens 9 is the photographing optical system, and at the wide-angle end of zooming, this system becomes a telescopic link. Further, although it is customary to provide a finder optical system between the relay lens section B and the film F, it is not shown in this figure.

Further, 9 is a fundus image (primary image) obtained by the objective lens 1, 9' is a re-formed image, 10 is an on-axis light beam, ], 1 is an off-axis light beam. Although lenses 3 to 8 are shown as single lenses, they are often composed of laminated lenses or a plurality of single lenses.

With the above configuration, the imaging optical system is tested 111i! l! After facing u, an illumination system (not shown) is activated to illuminate the fundus, and while observing the fundus image through the finder, the variable magnification unit z
By moving the frame setter 4, variator 5, and fixed lens 6 integrally in the optical axis direction, optimal focus can be obtained as described later. Next, a desired magnification can be selected by zooming. FIG. 2 shows the arrangement of the optical system after the aperture at the wide-angle end, and FIG. 3 shows the arrangement at the telephoto end.

In Figures 1 and 2, the primary image of the fundus formed at a certain position is formed on film F despite zooming, but as a result of zooming, the area on the image that appears on the same size film is (height) changes.

On the other hand, as shown in FIGS. 4 to 6, when the eye to be examined has an abnormal diopter, the position where the primary image 9 is formed is displaced in the optical axis direction. Figure 5 shows the case of 0 diopter detection optometry, Figure 4 shows the case of + diopter, and Figure 5 shows the case of - diopter. When focusing on the eye to be examined of + diopter, move the variable magnification unit 2 toward the image direction. When focusing on the subject's eye of -diopters, the variable magnification section 2 is moved toward the object. In other words, as long as the variable magnification unit 2 is moved in the optical axis direction to align the object point position of the sensor 4 with the image point (re-imaged image 9, not shown) of the fixed lens 3, Since the light beam exiting the fixed lens 6 is afocal, the light beam forms an appropriate image on the film PK regardless of the distance between this lens 6 and the lens 7 behind it.

Note that unless the light beam exiting the variable magnification section is afocal, it cannot be said that an image will always be properly formed.
There is no problem if the order of operations is to perform zooming, set the desired magnification, and then perform focusing. Furthermore, even in the case of a variable magnification unit that does not have a compensator and therefore cannot set the magnification at two locations, focusing can be performed by moving the variator and fixed lens together.

From FIG. 7 onwards, other embodiments are depicted. However, in all of these optical arrangements, the objective lens l is omitted.

In the example shown in FIG. 1, the variable magnification section 2 has no fixed lens, 41L is a negative variator, and 5& is a positive variator. Wide-angle end of movement trajectory for zooming, ■
indicates the telephoto end, and the camera 5ai reciprocates for zooming. If you choose this form, you can make the luminous flux emitted from the funpensator 5& to be afocal,
No fixed lens is required. Focusing can be achieved by moving the variator 4a and the sensor 5& together.

Figure 8 shows a negative variator 4b and a negative funpensator 5b.
, a variable power unit consisting of a positive fixed lens 6 is moved together to perform focusing.

The compensator 5b is assumed to make a convex reciprocating motion toward the object side, and the light beam exiting the fixed lens 6 is afocal.

FIG. 9 shows that the magnification variable part Z consists of a negative convencator, a 40% positive variator 5c, and a negative fixed lens 6', and the compensator 4C switches between two solution equations for zooming. We are working to expand the zoom range. As in this example, the fixed lens of the variable power unit may have negative refractive power.

In the example shown in FIG. 10, the variable power section 2 is a compensator 4d.

It consists of a variator 5d and a positive fixed lens 6.

The paraxial ray exiting the fixed lens 6 is afocal, and focusing is achieved by integrally moving the variable power unit Z.

In the example shown in FIG. 11, the front fixed lens 3' following the diaphragm 2 has a negative refractive power, and this lens 3' forms a reduced virtual image of the primary image 9. The variable power unit 2 is composed of a positive compensator 4es, a negative variator 5e, and a positive fixed lens 6, and focusing is achieved by moving these externally. Note that the compensator 4e is of a type that transfers between two solutions.

In FIG. 12, the refractive power of the front fixed lens 3' is negative as described above, and on the other hand, the variable power section 2 consists of a positive variator 4f and a negative compensator 5f. The paraxial light ah emitted from the funpensator 5f is afocal, and the variator 4
Focusing is performed by moving it together with f.

FIG. 13 shows an example in which there is no fixed lens after the diaphragm and no fixed lens in the variable magnification section, and the variable magnification section 2 has a positive variator 4g.
and 5g of negative funpen sweater.

Focusing is performed by moving the variator 4g and compensator 5g together.

FIG. 14 is an example in which there is no temporary fixed lens for the aperture.

Magnification variable part 2 positive funpensator 4h, negative variator 5
h, consists of a positive fixed lens 6, and these are positioned as one! Focusing is done by JM.

Generally, in a lens system that changes magnification by moving a movable lens, a focusing lens is placed before the movable lens in order to provide an object point at a fixed position.
In the case of the optical system of a fundus camera, such an arrangement increases the size of the optical system and makes it difficult to correct aberrations; however, the present invention eliminates the front focal lens, which not only makes the device more compact. This has the effect of facilitating aberration correction.

[Brief explanation of the drawing]

FIG. 1 is an optical cross-sectional view showing an actual hli example of the present invention;
3 and 3 are sectional views of main parts for explaining the zooming action, and FIGS. 4 to 6 are sectional views of the main parts for explaining the focusing action. Figures 1 to 14
The figures up to the figures are sectional views of main parts showing different embodiments. In the figure, 1 is the objective lens, m is the perforated mirror, 2 is the photographic aperture,
3 is a front fixed lens, 2 is a variable magnification unit, 4 is a function shifter, 5 is a variator, 6 is a fixed lens, R is a relay lens, F is a film, and 4a to 4h and 5aN5h are movable lenses. Applicant Canon Co., Ltd.

Claims (1)

[Claims] (1) In a fundus camera equipped with an imaging system and an illumination system for the object to be photographed, the imaging system includes a photographing diaphragm on the image side of the objective system and a movable lens that moves for zooming. A variable-magnification fundus camera comprising a variable-magnification section and a fixed imaging lens, and the variable-magnification section is configured to be movable for focusing. (2) The variable-magnification fundus camera according to claim 1, wherein the variable-magnification unit emits the paraxial light beam incident on the fixed imaging lens as afocal light. (31) A variable magnification fundus camera according to claim 2, wherein the movable lens is a funpensator and a parier grouper. A variable magnification fundus camera according to range 1, 2, or 3. (5) The photographing system includes a fixed lens between the photographing diaphragm and the variable magnification unit for further reducing the image produced by the objective member. (6) The variable power fundus camera according to claim 11, wherein the fixed imaging lens is a Galileo telephoto system.