JPH0327604Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an eye examination optotype device having a transmission type optotype.

[Prior Art] Conventionally, this type of eye testing device has been widely used as a visual acuity testing device, and tests are performed by presenting a translucent or non-transparent optotype inserted into the device to a subject. There is. When a translucent optotype is used, the optotype can be illuminated by placing an illumination light source behind the optotype surface, or by arranging two or more light sources to illuminate the optotype surface behind the optotype. A method of illuminating from both directions on the observation side is adopted. In the case of non-transparent optotypes, a method is usually adopted in which a light source is placed on the observation side of the optotype surface.

There are a variety of optotype materials for displaying the Landolt ring for visual acuity tests, from conventional paper and film to liquid crystals, but in order to perform accurate tests, it is necessary to use optotypes that are easy for the examinee to perform. It is preferable to use liquid crystal because memorization is not possible and visual indicator presentation can be made variable without requiring mechanical drive parts such as a motor.

There are two types of LCD optotypes: non-transparent reflective LCD optotypes that have a reflector on the back side of the liquid crystal display, and transmissive LCD optotypes that are illuminated from behind by placing a diffuser plate in place of the reflector. However, in the reflective type, since the light is illuminated from the front side of the target, the shadow of the target such as the Landolt ring is reflected on the reflector, making the target double and having a negative impact on the examination. Transmissive liquid crystal optotypes that cannot be used are preferred.

By the way, important things in a visual acuity test include that the brightness of the optotype surface is about 300 to 700 lux, that the visual field is wide, and that the contrast of the optotype is high. When considering these points with conventional equipment, we find that the brightness of the optotype surface can be solved by selecting an appropriate light source and there is no problem, but the contrast between the observation field and the optotype remains unsolved. There is still room for improvement. In other words, when using a transmissive liquid crystal as a visual target, it is possible to widen the field of view by using a large liquid crystal and illuminating it from behind, but using such a large liquid crystal would make the device extremely expensive, so it is better I can't say it's a solution.

In addition, in the case of a device in which the light source is placed both behind the optotype and on the observation side, the contrast of the optotype decreases because the light from the observation side illuminates the optotype image on the liquid crystal surface. Another disadvantage is that two or more light sources are required. In other words, although conventional devices are able to perform accurate inspections to a certain extent by using transmissive liquid crystals, they are still not fully satisfactory in terms of target contrast, observation field of view, manufacturing cost, etc. It is difficult to say that it is.

[Purpose of the invention] The purpose of the invention is to eliminate the drawbacks of the conventional devices described above, and to provide an eye examination optotype that makes it possible to obtain a wide optotype and high contrast of the optotype even when using a small liquid crystal optotype. The objective is to provide standard equipment.

[Summary of the invention] The gist of the invention to achieve the above objectives is as follows:
An apparatus for performing an eye examination using an optotype, which includes a transmissive optotype provided with an opaque peripheral frame around the optotype, and a transmissive optotype for illuminating the optotype from behind directly or through a first light guiding means. An optotype device for eye examination, comprising a light source and a second light guiding means for irradiating a part of the luminous flux from the light source from the observation side while substantially limiting the peripheral frame portion. It is.

[Embodiments of the invention] The invention will be described in detail based on illustrated embodiments.

FIG. 1 shows a first embodiment in which the present invention is applied to an optotype device for visual acuity testing, in which a light source 2 is placed diagonally behind a transmissive liquid crystal optotype 1 that faces the subject's eye S and displays a Landolt ring, etc. has been done. The liquid crystal optotype 1 is supported around the periphery by an opaque frame 3, and behind the liquid crystal optotype 1 there is a first reflective mirror 4 as a light guiding means, and a second reflecting mirror 4 is provided diagonally above the observation side as a light guiding means. Mirrors 5 are arranged, a diffuser plate 6 is provided between the liquid crystal optotype 1 and the first reflective mirror 4, and a black light shielding member 7 is attached to the center of the second reflective mirror 5. . The first reflecting mirror 4 guides a part of the luminous flux from the light source 2 to the diffuser plate 6, and the second reflecting mirror 5 guides a part of the luminous flux from the light source 2 to the frame part 3.
It is arranged to lead to.

The light beam emitted from the light source 2 is reflected by the first reflecting mirror 4 and directed upward, and after being diffused by the diffuser plate 6, illuminates the liquid crystal optotype 1 from behind.
Landolt's ring and the like are observed by the eye S to be examined as transmitted light. On the other hand, among the light beams emitted from the light source 2, the light beams that reach the light shielding member 7 of the second reflective mirror 5 are blocked by the light shielding member 7, and the light flux reaching the light shielding member 7 of the second reflective mirror 5 is blocked by the light shielding member 7. The light flux that has reached the top is reflected by the reflecting mirror 5, illuminates the frame 3, and is observed by the subject's eye S as reflected light from the frame 3.

Here, the liquid crystal optotype 1 is composed of a transmission-type optotype for displaying an optotype such as a Landolt ring, but similar results can be obtained by using a transmission-type electrochromic material. . The light shielding member 7 may be provided in the optical path that illuminates the observation side of the liquid crystal target 1, but if the light source 2 has a certain size, the light shielding member 6 may be placed close to the liquid crystal target 1. With this, the contrast of the liquid crystal optotype 1 can be further enhanced. Note that the light shielding member 7 does not have to be a non-reflective member as in the embodiment, but may be an opening provided in the second reflective mirror 5. The light shielding member 7 is the same size as the reflecting mirror 5, and the light shielding member 7 has a reflectance distribution so that the peripheral frame 3 is the same as the liquid crystal optotype 1.
The light may be illuminated more strongly than the .

In this embodiment, since a liquid crystal is used as the optotype, it is possible to prevent memorization of the optotype and display the optotype without the need for driving parts as in the past. Not only can it be possible to avoid blurring of the image due to the shadow of the reflection plate being reflected on the reflection plate, but also it is possible to reduce the number of light sources by providing the reflection mirrors 4 and 5. Moreover, it is possible to reduce the number of light sources by providing the reflection mirrors 4 and 5. 7, the subject's eye can be illuminated by illuminating only the frame 3 around the liquid crystal optotype 1 or by providing stronger illumination to the frame 3 around the liquid crystal optotype 1 than to the liquid crystal optotype 1. The frame portion 3 is visible along with the liquid crystal optotype 1 at S, making it possible to widen the field of view without reducing the contrast of the liquid crystal optotype 1.

FIG. 2 shows a second embodiment, in which the same reference numerals as in FIG. 1 represent the same or equivalent members. Here, the mutual positional relationship of the eye S to be examined, the liquid crystal optotype 1, the frame 3, and the diffuser plate 6 is the same as that in FIG. 1, but the light source 2
is placed behind the liquid crystal optotype 1 placed on the observation optical axis, one end of each of the optical fiber bundles 8 consisting of a plurality of fibers is placed around the light source 2, and the other end of the optical fiber bundle 8 is placed behind the liquid crystal optotype 1 placed on the observation optical axis. It is arranged around the frame part 3.
Note that the end angle of the optical fiber bundle 8 is adjusted so as not to illuminate the liquid crystal optotype 1.

In this way, the light flux from the light source 2 is transmitted to the diffuser plate 6.
The liquid crystal optotype 1 is illuminated through the optical fiber bundle 8, and the frame portion 3 guided upward by the optical fiber bundle 8 is illuminated. This second embodiment also provides the same effects as the previous embodiment, and the eye S to be examined can observe the liquid crystal optotype 1 with high contrast and a wide field of view.

[Effects of the invention] As explained above, the optotype device for eye examination according to the present invention guides a light beam from one light source in multiple directions through a light guiding means such as a reflective mirror or an optical fiber. By illuminating from both the back and the observation side, and using a reflective mirror or optical fiber with a partial light-shielding function as a light guiding means on the observation side, the peripheral frame of the optotype can be illuminated more strongly than the optotype. It has the advantage of being able to illuminate and secure a wide field of view without reducing the contrast of the optotype, making it possible to perform higher-precision inspections while keeping the liquid crystal optotype small.

[Brief explanation of the drawing]

The drawings show an embodiment of the optotype device for eye examination according to the present invention, and FIG. 1 is a perspective view of the main part of the first embodiment, and FIG. 2 is a perspective view of the main part of the second embodiment. It is. Reference numeral 1 is a transmission type liquid crystal optotype, 2 is a light source, 3 is a frame portion, 4 and 5 are reflective mirrors, 6 is a diffuser plate, 7 is a light shielding member, 8 is an optical fiber bundle, and S is an eye to be examined.

Claims (1)

[Claims for Utility Model Registration] 1. A device for performing an eye examination using an optotype, including a transmissive optotype having an opaque peripheral frame around the optotype, and a transmissive optotype provided with an opaque peripheral frame, and the optotype being directly or A light source for illuminating through a light means, and a second light guiding means for irradiating a part of the luminous flux from the light source from the viewing side while substantially limiting the peripheral frame. Characteristic optotype device for eye examination. 2. The optotype device for eye examination according to claim 1, wherein the optotype is a transmissive liquid crystal. 3. The optotype device for eye examination according to claim 1, wherein the optotype is made of a transmission type electrochromic material. 4. The optotype device for eye examination according to claim 1, wherein the first light guide means is a reflecting mirror provided behind the optotype. 5. The optotype device for eye examination according to claim 1, wherein the second light guide means is a reflecting mirror provided on the viewing side of the optotype. 6. The optotype device for eye examination according to claim 5, wherein the reflecting mirror has a partial light shielding function so as not to illuminate the optotype. 7. The optotype device for eye examination according to claim 1, wherein the second light guide means is a plurality of optical fibers.