JPS5820625B2 - The construction of a medical examination room - Google Patents

Description

[Detailed Description of the Invention] In a fundus observation and photography device, particularly one in which a part of the optical system such as an objective lens is used both for fundus illumination and observation and photography,
Of the illumination light, reflected light from the surface of the objective lens and from the corneal surface of the subject's eye significantly degrades the quality of the observed and photographed image, so measures must be taken to remove this reflected light.

For this purpose, as is known in U.S. Pat. No. 2,777,364 and elsewhere, it is known to place a light-shielding object on the objective lens to prevent reflected light, or to use a concave mirror instead of a lens in the objective system. However, in the former case, the objective lens is a Lunn group of meniscus convex lenses, so the observation and photography field angle cannot be more than 30°, and in the latter case, the concave mirror must be installed at an angle, which causes the disadvantage of a unique distortion aberration.

The present invention relates to an optical system in which the objective lens is composed of two groups with positive refractive power, and by providing special conditions to these, it is possible to separate and remove reflected light that is harmful to observation and photography, to widen the observation and photography field angle to 45° or more, and to improve aberrations.

To explain Figure 1, 1 is the eye to be examined, 2 is an objective lens composed of two lens groups 20, 2□ with positive refractive power, each of which is a single lens or a cemented lens, 3 is a relay lens, 4 is a film surface, 5 is a finder light path deriving mirror that is freely inserted into the optical path between the lens 3 and the film surface 4, 6 is a finder system, 7 is an illumination light introduction mirror (hereinafter referred to as a perforated mirror) having a light-transmitting hole in the center and disposed obliquely between the objective lens 2 and the relay lens 3, 8 is an illumination light source, 9 is a condenser lens, 10 is a ring slit, and 11 is a relay lens.

Incidentally, the light transmitting hole of the illumination light introducing mirror acts as a photographic aperture, but as is well known, the aperture may be positioned slightly off-center.

As shown in Figures 2 and 3, for each of the lens groups 21, 2° that constitute the objective lens 2, the first surface counting from the side of the eye to be examined, i.e., surfaces 11 and 13, are convex toward the side of the eye to be examined, the center of curvature of the final surface r4 is located on the point where the perforated mirror 7 intersects the optical axis, one of surfaces 11 and 13 is made aspheric so that the center of the cornea 12 of the eye to be examined is imaged at the center of the perforated mirror 7 without spherical aberration, the curvature of the final surface r2 of the front lens group 2 is determined so that light emitted from the point where the perforated mirror 7 intersects the optical axis passes through the rear lens group 2□ and is reflected by surface 12, and light shields 13, 14 of an appropriate size capable of blocking light rays reflected by surfaces 11 and 13 that are harmful to observation and photography are placed on surfaces 12 and 14 or in their vicinity.

In the above optical system, light emitted from a light source 8 passes through a condenser lens 9, a ring slit 10, and a relay lens 11 to form an image of the light source on a perforated mirror 70. After being reflected by this, the light passes through an objective lens 2 and is incident on the cornea 1 of the eye 1 to be examined.
Images are formed on two planes to illuminate the fundus.

Light from the illuminated fundus is imaged near the rear focal plane of the objective lens 2, and then imaged on a film surface 4 by a relay lens 3. If a finder light output mirror 5 is inserted in the optical path, the image is observed in the viewfinder field.

In this case, if the cornea 12 and the aperture mirror T are arranged in a conjugate relationship with respect to the objective lens 2, the aperture mirror 7
The illumination light reflected in a ring shape illuminates the fundus in a ring shape from above the cornea, and is emitted from inside the ring of the ring slit image formed on the cornea.

The observation and photography light passes through the hole in the apertured mirror 7, but the light reflected by the cornea of the illumination light does not pass through the hole and is separated and removed.

In addition, 11 surfaces are harmful to observation and photography due to reflected light from the lens surface.
The light reflected from the surface 13 is blocked by light shields 13 and 14 as shown in FIG.

In addition, the center of curvature of surface 14 is at the center of perforated mirror 7, and as for surface 12, when light emitted from the point where perforated mirror 7 intersects the optical axis passes through lens group 22 and is reflected by surface 12,
The radii of curvature of the 12 surfaces are determined so that the incident light returns along the same path as the incident light, so that the surface reflected light from these surfaces is also separated and removed from the observation and photography light.

In other words, since the illumination light is reflected from the mirror surface of the perforated mirror I toward the objective lens 2, if the light reflected from the lens surface travels back along the path of the incident light, the reflected light will reach the mirror surface of the perforated mirror 7, but will not enter the light-transmitting hole.

Furthermore, the objective lens in this type of conventional device is only one lens group corresponding to the lens group 22 in the present invention, and the first surface of the lens group must have a fairly strong refractive power. However, in the present invention, a lens group with positive refractive power is provided in front of the lens group 22 to share the refractive power, thereby improving the aberration correction of the entire system and increasing the observation and photography field angle to 45°.
This has the effect of expanding the range to as much as 100°.

Next, examples of numerical values of the objective lens for implementing the present invention will be shown.

In this example, as shown in FIG. 3, the front lens group 2 is a cemented lens for achromatization, and the light shielding member 13 is provided in the convex lens.

For this purpose, the convex lens is constructed of a laminated lens of the same material, and a light shield is provided on the laminated surface.

r: radius of curvature of the refractive surface in sequence, where r3 is the radius of the maximum circle of apex contact of the aspheric surface; d: surface spacing in sequence, where d2' and dg are the spacing between the light shielding body 13 and the front and rear surfaces; N: refractive index of each lens in sequence; V: Abbe number of each lens in sequence; diameter of light shielding body 13 -0.5; diameter of light shielding body 14 -0.5. The longitudinal aberration of this objective lens is as shown in Figure 4.

According to the present invention described above, the image of the perforated mirror is formed on the cornea without spherical aberration, and the corneal reflected light is eliminated.
Selecting the shape of the lenses in the group has the effect of eliminating harmful reflected light from the objective lens itself.

[Brief description of the drawings]

FIG. 1 is a diagram showing the main components of an embodiment of the optical system of the present invention, FIG. 2 is a diagram showing the functional relationship of the objective lenses of the optical system of the present invention, and FIG.
The figure shows the structure of one embodiment of the objective lens, and Fig. 4 shows the aberration curve of the embodiment. 1: Eye to be examined, 2: Objective lens, 2□, 22: Lens group constituting the objective lens, 3: Relay lens, 4: Film surface, 5: Finder mirror, 6: Finder system,
7: Perforated mirror for introducing illumination light, 8: Illumination light source, 12:
Cornea, 13, 14: light shield.

Claims (1)

[Claims] An optical system of a fundus observation and photography device, comprising two lens groups with positive refractive power, each of which is made up of a cemented objective lens or a single lens, and which has a shape such that the first surface of each group, counting from the side of the eye to be examined, faces the convex surface toward the eye to be examined, and the final surface of the entire group has a radius of curvature whose center of curvature approximately coincides with the point where the perforated mirror for introducing illumination light intersects the optical axis, and at least one of the first surfaces of each group is an aspheric surface that forms an image of the center of the cornea of the eye to be examined at the center of the perforated mirror without spherical aberration, and further, the radii of curvature of the first surfaces of each group are determined so that, of the illumination light reflected at these surfaces, light that passes through the hole in the perforated mirror can be blocked by a light blocking means, and so that the reflected light at the rear surface of the group on the side of the eye to be examined can be blocked by returning along the same path as the incident light.