JP4520252B2 - Fundus camera - Google Patents

Description

  The present invention relates to a fundus camera that photographs the fundus of a subject's eye.

In the fundus camera, the fundus illuminates the fundus through a ring slit arranged at a position substantially conjugate with the eye pupil to be examined, and the fundus image of the eye to be examined is obtained through a diaphragm having a central opening arranged at a position substantially conjugate with the eye pupil to be examined. Shooting. This type of fundus camera has a problem that the photographed fundus image is darker at the periphery than at the center. As a countermeasure for this problem, by arranging a filter member whose transmittance gradually increases as it approaches the peripheral part from the central part at a position substantially conjugate with the fundus oculi of the fundus illumination optical system, the central part and the peripheral part are arranged. There has been proposed one that corrects the difference in brightness of the part (see Patent Document 1).
JP 62-38133 A

  However, when the filter member is placed at the fundus conjugate position as in Patent Document 1, it is easily affected by dust and dust adhering to the filter member, and the photographic image quality is likely to deteriorate. In addition, if an attempt is made to manufacture a filter member with a coating that gently changes the transmittance, an advanced coating technique is required, resulting in high costs.

  In view of the above problems, an object of the present invention is to provide a fundus camera that can easily and inexpensively improve unevenness in the amount of light of a fundus photographed image.

(1) In a fundus camera including a photographing optical system that photographs the fundus illuminated by the illumination optical system, the illumination optical system includes an illumination light source for fundus photography and a condenser for condensing a light beam from the illumination light source. A condenser lens arranged so that the eye-side focal position of the eye to be in the fundus conjugate position, and a luminous flux from the illumination light source arranged at the pupil conjugate position via the condenser lens as a ring-shaped illumination luminous flux A ring slit, a light path between the condenser lens and the illumination light source, and a filter disposed at a position where a light beam illuminating the fundus central part and a light beam illuminating the fundus peripheral part are separated, And a filter formed so that the transmittance of the central region is uniformly smaller than the transmittance of the peripheral region.
(2) In the fundus camera of (1), the filter is formed directly on the lens surface of the condenser lens.

  According to the present invention, it is possible to easily and inexpensively improve unevenness in the amount of light of a fundus photographed image.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of an optical system of a fundus camera according to the present invention.
The optical system includes a fundus photographing illumination optical system 10 and a fundus photographing optical system 30. The fundus camera includes an observation optical system for observing the eye to be inspected and an observation illumination optical system having a light source for enabling observation of the eye to be inspected, but the description thereof is omitted here.

  In the fundus illumination optical system 10, the imaging light source 14 such as a flash lamp conjugate to a substantially pupil position and the peripheral region 40 b have uniform transmittance, and the transmittance of the central region 40 a is equal to the transmittance of the peripheral region. Filter member 40 that becomes small like this, condenser lens 15 that collects the light flux from the light source 14, ring slit 17 having a ring-shaped opening provided at a conjugate position with the pupil of the eye to be examined, relay lens 18, mirror 19, center It has a black spot plate 20 having a black spot, a relay lens 21, a perforated mirror 22, and an objective lens 25. F is a position conjugate with the fundus formed between the ring slit 17 and the optical path of the condenser lens 15. The condenser lens 15 is arranged so that the focal position of the condenser lens 15 on the eye E side is located at the fundus conjugate position F. Thereby, since the light source 14 and the condenser lens 15 are in an infinite conjugate relationship with respect to the fundus, even if dust or dust adheres to the filter member 40 disposed therebetween, or there are scratches, Little affected by fundus illumination.

  The filter member 40 can be easily and inexpensively manufactured by applying a half mirror to the central region 40a using a transparent glass plate as a base material. Moreover, you may use for the center area | region 40a with a small transmittance | permeability the diffusion plate comprised from the ground glass etc. which reduce a transmitted light quantity by diffusing light. These can also be manufactured inexpensively and easily.

  The fundus photographing optical system 30 includes an objective lens 25, a photographing diaphragm 31 located in the vicinity of the aperture of the perforated mirror 22, a focusing lens 32 movable in the optical axis direction, an imaging lens 33, and a CCD camera 35 having sensitivity in the visible range. Is provided. The photographing aperture 31 is disposed at a position substantially conjugate with the pupil of the eye E with respect to the objective lens 25.

The luminous flux emitted from the photographing illumination light source 14 illuminates the ring slit 17 through the filter member 40 and the condenser lens 15. The light transmitted through the ring slit 17 reaches the perforated mirror 22 via the relay lens 18, the mirror 19, the black spot plate 20, and the relay lens 21. The light reflected by the perforated mirror 22 is once converged in the vicinity of the pupil of the eye E by the objective lens 25, and then diffused to illuminate the fundus of the eye to be examined.
At the time of shooting, the reflected light from the fundus illuminated with the shooting illumination light passes through the objective lens 25, the perforated mirror 22, the shooting aperture 31, the focusing lens 32, and the imaging lens 33, and then to the shooting CCD camera 35. Form an image.

  Next, the effect of the filter member 40 arranged between the light source 14 and the condenser lens 15 and the difference in effect due to the difference in the arrangement position will be described with reference to FIGS. It should be noted that a light beam having an angle of view of 10 °, 20 °, or the like described below is a light beam that is tilted at 10 °, 20 °, or the like with respect to the optical axis of the objective lens 25 among light beams collected on the fundus. Point to.

  2A and 3A, the position P0 between the light source 14 and the condenser lens 15 is focused at an angle of view of 0 ° out of the light beams emitted from both ends of the light source 14 (filament). This is the position where the light beam and the light beam that is condensed at an angle of view of 20 ° are exactly separated. FIG. 2A shows a case where the filter member 40 is disposed at the position P1 near the condenser lens 15 on the condenser lens 15 side from the position P0.

  Here, the transmittance of the central region 40a is 50%, and the area thereof is larger than the size through which all the light flux with an angle of view of 0 ° at the center of the fundus passes and the light flux with an angle of view of 20 ° at the periphery of the fundus passes. It is assumed that it is set smaller than the size. Further, it is assumed that the transmittance of the peripheral region 40b is almost 100%. In this case, since all the luminous fluxes having an angle of view of 0 ° pass through the central region 40a, they become 50% of the original brightness. The luminous flux having an angle of view of 20 ° is 100% of the original brightness because 100% of the original luminous flux passes through the peripheral region 40b. The luminous flux having an angle of view of 10 ° is 75% (50% × 50% + 50% = 75%), assuming that 50% of the original luminous flux passes through the central region 40a. Although not shown in FIG. 2A, the luminous flux with an angle of view of 5 ° is 60% (80% × 50% + 20% = 60%) assuming that 80% of the original luminous flux passes through the central region 40a. ) Similarly, the luminous flux with an angle of view of 15 ° is 90% (20% × 50% + 80% = 90%), assuming that 20% of the original luminous flux passes through the central region 40a. As described above, the proportion of the fundus illumination light gradually changes according to the proportion of the original luminous flux passing through the central region 40a having a low transmittance for each angle of view (see FIG. 2B).

  Further, adjustments such as brightness adjustment and darkening from which angle of view can be adjusted by the transmittance and area of the central region 40a. As for how to adjust the illumination light amount for each angle of view, the light amount distribution received by the CCD camera 35 in the optical arrangement when the filter member 40 is not placed is obtained in advance, and the light amount unevenness at this time can be corrected. In addition, the transmittance and area of the central region 40a may be determined.

  On the other hand, FIG. 3A shows a case where the filter member 40 is arranged at the position P2 near the light source 14 on the light source 14 side from the position P0. Such a vicinity position P2 of the light source 14 includes a position substantially conjugate with the rear surface of the crystalline lens of the eye to be examined. As in the case of FIG. 2A, it is assumed that the transmittance of the central region 40a is 50%, and the area is set larger than the size through which all the light flux having an angle of view of 0 ° passes. Since all the luminous fluxes having an angle of view of 0 ° pass through the central region 40a, they become 50% of the original brightness. However, since a part of the luminous flux having an angle of view of 20 ° passes through the central region 40a, the amount of illumination light having an angle of view of 20 ° is reduced. For example, the luminous flux having an angle of view of 20 ° is 70% of the original brightness if 60% of the original luminous flux passes through the central region 40a. Also, a light flux with an angle of view of 10 ° is 60% of the original brightness if 80% of the original light flux passes through the central region 40a. FIG. 3B shows an example of the change in illumination light amount (reduced light amount) for each angle of view at this time. Comparing FIG. 2B and FIG. 3B, both are the same at an angle of view of 0 °, but the amount of light reduction is greater in FIG. 3B at the periphery of the angle of view of 20 °. For this reason, when the filter member 40 is provided in the vicinity P1 of the light source 14 where the luminous flux having the angle of view of 0 ° and the luminous flux of the angle of view of 20 ° is not separated, the light amount loss at the fundus periphery is large, and brightness adjustment or It is difficult to make adjustments such as darkening from any angle of view, which is disadvantageous. Therefore, the position where the filter member 40 is provided is preferably a position where at least a light beam having an angle of view of 0 ° and a light beam having an angle of view of 20 ° are separated.

  In addition, as a structure which arrange | positions the filter member 40 in the position where the light beam with an angle of view of 0 ° and the light beam with an angle of view of 20 ° are separated, a coating such as a half mirror corresponding to the central region 40a of the filter member 40, It may be formed directly on the lens surface of the condenser lens 15. In this way, the condenser lens 15 can be used also as the filter member 40, and a more inexpensive device configuration can be achieved.

  Hereinafter, a method of adjusting the illumination light amount and the central illumination light amount for each angle of view by changing the size and transmittance of the central region 40a will be additionally described. FIG. 4 is a diagram illustrating a case where the size of the central region 40a is changed in the configuration in which the filter member 40 is disposed in the vicinity of the condenser lens 15. FIG. FIG. 5 is a diagram for explaining, for each angle of view, how much the light amount of the light beam that illuminates the fundus is reduced by the filter member 40 in the optical system as shown in FIG. At this time, if the size of the central region 40a is set to a size that is just in contact with the luminous flux having an angle of view of 20 ° as shown in FIG. 4A, the light attenuation characteristic as shown in the graph a in FIG. Can do. Further, if the size of the central region 40a is set to a size that allows 50% of the luminous flux having an angle of view of 10 ° to pass as shown in FIG. 4B, the light attenuation characteristic as shown in the graph b in FIG. 5 is obtained. be able to. Further, when the size of the central region 40a is set to such a size that all the luminous flux having an angle of view of 0 ° passes as shown in FIG. 4C, the light attenuation characteristic as shown in the graph c in FIG. 5 is obtained. be able to.

  Furthermore, various dimming characteristics can be obtained by changing the transmittance of the central region 40a. For example, in FIG. 4A, when the central region 40a has a transmittance of 25%, the light attenuation characteristic as shown by the graph g in FIG. 6 can be obtained. When the central region 40a has a transmittance of 75%, it is possible to obtain a light attenuation characteristic as shown by a graph f in FIG. When the central region 40a has a transmittance of 50%, it is possible to obtain a light attenuation characteristic as shown by a graph e in FIG.

  As described above, by changing the area and transmittance of the central region 40a, it is possible to adjust the illumination light amount for each angle of view and the illumination light amount at the central portion without dimming the illumination light amount around the fundus. . If different dimming characteristics are obtained in this way, when correcting unevenness in light amount according to the light amount distribution of the fundus reflected light when the filter member 40 is not placed, without dimming the luminous flux that illuminates the fundus periphery, It becomes possible to provide a filter member suitable for the light quantity distribution at that time. Therefore, it is possible to appropriately correct the unevenness of the amount of light in fundus imaging.

It is a figure which shows the structure of the optical system of the fundus camera concerning this invention. It is a figure explaining the effect | action of the filter member arrange | positioned between the illumination light source for fundus photography, and a condenser lens. It is a figure explaining the difference in the effect by the difference in the arrangement position of a filter member. It is a figure which shows the case where the magnitude | size of a center part area | region is changed in the structure which has arrange | positioned the filter member in the vicinity position of a condenser lens. It is a figure explaining how much the light quantity of the light beam which illuminates the fundus is reduced for each angle of view by changing the size of the central region of the filter member. It is a figure explaining a light attenuation characteristic changing by changing the transmittance | permeability of the center part area | region of a filter member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fundus illumination optical system 14 Imaging light source 15 Condenser lens 17 Ring slit 30 Fundus imaging optical system 40 Filter member 40a Central area 40b Peripheral area

Claims (2)

In a fundus camera including a photographing optical system that photographs the fundus illuminated by the illumination optical system, the illumination optical system is an illumination light source for photographing the fundus and a condenser lens for condensing a light beam from the illumination light source. A condenser lens arranged so that the focal position of the eye to be examined is located at the fundus conjugate position, and a ring slit in which a light flux from the illumination light source arranged at the pupil conjugate position via the condenser lens is a ring-shaped illumination light flux And a filter disposed at a position where an optical path between the condenser lens and the illumination light source is separated from a light beam that illuminates the center of the fundus and a light beam that illuminates the periphery of the fundus. A fundus camera comprising: a filter formed so that the transmittance of the central region is uniformly small with respect to the transmittance. 2. The fundus camera according to claim 1, wherein the filter is formed directly on a lens surface of the condenser lens.