JPS5823099B2 - fundus camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fundus camera, and particularly to a fundus camera with variable imaging magnification.

When observing and photographing the eye to be examined using a fundus camera, there are cases where it is desired to enlarge a part of the fundus for detailed diagnosis.

In particular, as screens become wider these days, if the film size used in the fundus camera is kept constant, the imaging magnification will decrease, making it difficult to see details. There will be demands.

The illumination system of the fundus camera does not change the angle of view when projecting the illumination light flux, so the range of the fundus illuminated by the illumination light flux remains constant. Since the range to be photographed changes, the amount of light reaching the photographic film also changes.

An object of the present invention is to enable a desired exposure amount to be obtained regardless of changes in photographing magnification.

First, a fundus camera with variable imaging magnification will be described below.

In FIG. 1, E is the eye to be examined and Ef is the fundus.

On the other hand, 1 is an observation lamp, 2 is a condenser lens, and 3
is a photography strobe tube, 4 is a second condenser lens, 5 is
is an optical path refracting mirror.

Reference numeral 7 denotes a slit plate having an annular slit, on which the light beam emitted from the lamp 1 and the light beam emitted from the S-Robo tube 3 converge.

8 and 9 are relay lenses, respectively, and 10 is a perforated mirror with an aperture.

However, the aperture may be installed separately on the image side of the perforated mirror.

Reference numeral 11 denotes an objective lens, and the aperture mirror 10 and the aforementioned slit plate 7 are conjugate with respect to the relay lenses 8 and 9, and the aperture mirror 10 and the pupil of the eye to be examined occupying a predetermined position are conjugate with respect to the objective lens 11.

12 is an imaging lens, 13 is a film, and F is an image plane of the imaging lens. An image of the fundus Ef is formed by the objective lens 11, and then re-imaged on the film 13 by the imaging lamp 12. .

14 is a flip mirror, 15 is a field lens, 16 is an optical path refractor, 17 is an eyepiece, and 18 is an observer.

Further, F is an image (observation image plane) of the imaging lens through the flip-up mirror 14.

The imaging lens 12 is a variable magnification lens, 12a and 12b are movable in the optical axis direction, 12a is a so-called variator, and 12b is a compensator.

Reference numeral 20 denotes a cam tube, and pins connected to lenses 12a and 12b are engaged with respective cam grooves cut in the cam tube.

Note that the linear cam tube in the optical axis direction, which the pin separately engages with, is omitted.

21 is a gear portion formed around the cam tube, 22 is a small gear that meshes with the gear portion, and the small gear 22 is driven by a drive portion 24.

Next, the effect will be explained.

When the lamp 1 is turned on, the light beam emitted from the lamp 1 converges at a condenser lens 2, then diverges, converges again at a condenser lens 4, diverges again, converges at the condenser lens 4 again, and changes direction at a mirror 5.

The light then passes through the annular opening of the slit plate 7 and is once imaged on the perforated mirror 10 by the action of the relay lenses 8 and 9, and then passes through the objective lens 11 to illuminate the fundus Ef.

The object light reflected by the fundus Ef passes through the objective lens 11 and the imaging lens 12 and is reflected by the mirror 14, and forms an image of the fundus in the observation image F'. observed by an observer.

Now, if the observer wishes to see an enlarged view of the observation area using FIG. 2 as the observation field, by operating the drive unit 24, the cam tube 20 is rotated and the lenses 12a and 12b are guided to the cam grooves.

The focal length of the imaging lens 12 increases.

Therefore, as shown in FIG. 3, the field of view is expanded, but the brightness of the field of view is accordingly decreased.

Furthermore, when the flip-up mirror 14 is raised and the strobe tube 3 emits light to take a photograph, if the light amount is set to match the low magnification side pressure, the amount of exposure will be insufficient.

Note that the configuration for changing the imaging magnification is not limited to the zoom method shown in Figure 1, and in Figures 4 to 8 below, the configuration for changing the imaging magnification is shown in Figures 4 to 8. Another configuration for changing the magnification will be explained.

Note that the figure is a partial view, and the same members as those in FIG. 1 are given the same numbers.

In FIG. 4, the entire imaging lens 12 is configured to be interchangeable with a convergent lens 30 having a different focal length.

However, when the interchangeable lens 30 is attached, the object plane of this lens coincides with the image plane P of the objective lens 11, and the image plane coincides with the film plane 13.

FIG. 5 shows a case where a part of the imaging lens 12 is replaced. For example, the imaging lens 12 is composed of a fixed front group 12a and a removable rear group 12b, and the rear group 12b is replaced by a lens group 31 having a different focal length. Change the composite magnification by exchanging with .

FIG. 6 shows a configuration in which a lens is installed in the photographing optical path to change the combined focal length of the optical system.

Figure 6A shows the configuration before the lens is attached, and Figure 6B
shows the configuration when the diverging lens 32 is inserted.

However, although the focal length of the optical system increases by inserting the lens 32, the position of the image also moves backward.

On the other hand, as shown in Figure 1, methods for adjusting the focus of a fundus camera generally include moving part or all of the imaging lens in the optical axis direction and changing the distance between the imaging lens and the flip-up mirror. However, in the case of a configuration in which a variable magnification lens 32 is attached as shown in FIG. This can be easily dealt with by moving the position of the film surface 13.

7A and 7B depict an example in which a variable power lens 33 consisting of at least two groups is inserted to change the magnification without changing the image plane position, A shows before insertion, and B shows after insertion. Indicates the form.

In FIG. 7B, the variable power lens is inserted behind the imaging lens, whereas FIG. 8 shows an example in which the variable power lens 34 is inserted just in front of the imaging lens.

Although the above example shows an example in which the magnification can be changed in two steps, it is possible to change the magnification in more steps by preparing interchangeable lenses or variable magnification lenses with various focal lengths.

Next, an embodiment for obtaining the optimum exposure amount for a photographic film will be described with reference to FIGS. 9 and 10.

However, elements in the drawings with the same numbers as in FIG. 1 are the same members.

Reference numeral 38 is a diaphragm plate, which has diaphragm holes 38a each having a different opening diameter (area), as shown in the plan view in FIG.
, 38b, 38c, and 38d.

Reference numeral 39 denotes a rotating shaft, which is connected to the aperture plate 38 and supported by a bearing.

The rotation of the rotation shaft 39 is used to replace all or part of the imaging lens 12 (FIGS. 4 and 5), or to insert or remove a variable power lens into or near the imaging lens (FIGS. 6 to 5).
8), and the imaging lens 1
2 to a desired magnification, an aperture hole suitable for the optimum exposure amount of the film 14 is installed in the photographing optical path.

Furthermore, as shown in FIG. 1, when the imaging lens 12 is a zoom lens, it is also possible to rotate the cam tube 20 step by step using the drive section 24, and rotate the aperture plate 38 in conjunction with the rotation of the cam tube 20. Furthermore, if the diaphragm plate 38 is replaced with an iris diaphragm, it is of course possible to continuously change the aperture diameter along with the continuous zooming of the imaging lens 12.

In addition, when setting the light intensity of the observation lamp 1 and photography strobe tube 3, if the optimum exposure amount is determined on the wide-angle (low magnification) side, then the aperture with the smallest aperture diameter on this low magnification side should be set. The hole 38a is inserted into the optical path, and the aperture hole 38d with the maximum aperture diameter is inserted on the enlarged side.

According to the above configuration, while the first observation lamp 1 is turned on and the fundus Ef is observed, the imaging lens 12 is zoomed or the lens is replaced and inserted.

Even if the magnification is changed by separation, the aperture diameter of the photographic diaphragm changes, so the amount of light incident on the observation surface F' remains constant and the brightness does not change.

Furthermore, even when the photography strobe tube 3 is turned on, the amount of light reaching the film 13 is at an optimum value, so there is an effect that good photography is possible regardless of the photography magnification.

In addition, especially if the change in magnification and the change in the aperture of the diaphragm are linked, the brightness of the field of view will be maintained constant even when the imaging/observation system is magnified and the observed area is enlarged. This has the effect of freeing the user from the trouble of repeatedly adjusting the amount of light, and also eliminating the inconvenience of forgetting to adjust the photographing light source and taking photographs with insufficient exposure.

[Brief explanation of drawings]

Figure 1 is a sectional view of the optical system. FIG. 2 and FIG. 3 are diagrams showing observation fields of view, respectively. Includes Figures 4, 5, and 6. B, FIG. 7 included, B, FIG. 8, and FIG. 9 are sectional views of the main parts of the optical system, respectively. FIG. 10 is a plan view. In Figure 1, Ef is the fundus, 1 is a light source for observation, 3 is a strobe tube for photography, 10 is a perforated mirror, 11 is an objective lens, 12 is an imaging lens, 13 is a film, 12a and 12b are movable lenses, 30 and 31 are interchangeable lenses, 32, 33, and 34 are removable lenses, 38 is an aperture diaphragm, and 38a to 38
d is an aperture hole.

Claims (1)

[Scope of Claims] 1. A fundus having an objective system facing the eye to be examined, an aperture, a rear optical system, and a photographing system including a film in this order, and an illumination system that projects an illumination beam for illuminating the fundus of the eye to be examined. A fundus camera characterized in that the rear optical system is capable of changing magnification, and the aperture of the diaphragm is variable in order to compensate for changes in film exposure due to the change in magnification. 2. The fundus camera according to claim 1, wherein the change in magnification of the rear optical system and the change in the aperture of the diaphragm are performed in conjunction with each other. 3. The fundus camera according to claim 2, wherein the aperture of the diaphragm is changed by moving a diaphragm plate provided with holes having different aperture diameters. 4. The fundus camera according to claim 2, wherein the magnification of the rear optical system is changed by moving the lens in the optical axis direction. 5. The fundus camera according to claim 2, wherein the magnification of the rear optical system is changed by attaching, detaching, or replacing a lens.