JPS60171031A - Eyesight meter - 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 a visual acuity meter that allows visual targets to be viewed binocularly.

BACKGROUND ART Conventionally, vision needles used in eye clinics, opticians, etc. are known that present separate optotypes to the left and right eyes of a subject and separate the left and right eye optical paths.

That is, for example, the visual acuity meter is such that the left eye is presented with an optotype for the left eye, and the right eye is not presented with the optotype for the left eye.

Moreover, in the visual acuity meter, only the optotype section is usually presented, and the subject cannot see the inner wall surface of the device other than the optotype section.

This conventional example has the following drawbacks.

That is, since the visual target consisting of 1) is viewed with one eye, and the visual target alone is viewed in a flat manner, it is unnatural and physiologically prone to so-called mechanical myopia.

2) The viewing angle is narrow because separate optotypes are presented to the left and right eyes.

As a result, in elderly people and others who have weak accommodation, accommodation may intervene and produce measurement results that are worse than the visual acuity in the natural state.

It is an object of the present invention to provide a visual acuity meter that eliminates the drawbacks of the conventional example. Hereinafter, the present invention will be described in detail using the accompanying drawings.

FIG. 1 shows a first embodiment of the invention.

The subject S looks at a visual target 1, such as a Landolt ring, which is apparently one distance away, through the left and right lenses 3L and 3R.

A plurality of Landolt rings and the like are presented on the optotype 1 for visual acuity measurement.

In the optical path, near the left and right lenses 3L, 3R, deflection prisms 2R, 2L are provided to refract the optical path so that the left and right eyes see the same optotype 1.

Deflection prism 2L, 2R and left and right lenses 6L.

The line of sight through 6R is approximately parallel to the left and right, and the so-called convergence angle is close to zero, resulting in a far viewing state.

Note that this case corresponds to the case of viewing an object at a distance of 5 m, for example. Here is the declination prism 2L.

The second prism is an achromatic prism in which a high dispersion prism H and a low dispersion prism L are pasted together to prevent deterioration of visual acuity measurement results due to chromatic aberration.

Note that the optical element is provided within the housing 4, making it a compact visual acuity meter.

The inner wall surface of the housing 4 does not need to be a light-absorbing surface as in the conventional example, and the inner wall surface near the visual target can be viewed at a convergence angle that is approximately equal to the convergence angle when viewing the line of sight 1. (Because it is three-dimensional rather than two-dimensional, it can eliminate the occurrence of physiological so-called mechanical myopia.)

FIG. 2 shows a second embodiment of the invention. The same reference numerals as in FIG. 1 indicate the same members. The liquid crystal optotype 6 is illuminated through a polarizing plate 5 whose polarization direction is in the direction in the drawing (horizontal direction).

Here, the liquid crystal optotype 6 has an electrode on an optotype section such as a Landolt ring, and when energized, the polarization direction of the optotype section is made of water.

FIG. 4 shows a liquid crystal optotype 6 with a normal percentage of #.

In the figure, broken lines indicate polarization directions at each location.

In FIG. 2, 7B and 7L are TN type liquid crystals, electrodes are provided on the entire surface, and the direction of polarization changes from the horizontal direction to the 45° direction when energized.

8R, 8Lti-polarizing plates, and the polarizing direction is horizontal like the polarizing plate 5.

When the TN type liquid crystal 7 and 7L are not energized, the liquid crystal optotype 6
When electricity is applied to the Landolt ring, etc., as shown in Fig. 4, the Landolt ring 6' appears dark (and the remaining part 6' appears bright).In the case of binocular visual acuity measurement, the TN type liquid crystal 7R.

7L is not energized, but in the case of visual acuity measurement using one eye, only the TNffl liquid crystal 7 of the eye other than the one to be examined is energized.

Then, as shown in FIG. 5, the polarization direction of the light passing through the TN liquid crystal 7 becomes uniform over the entire surface, and appears uniform between the Landolt ring 6' and the remaining part 6'.

In other words, in the case of visual acuity measurement using one eye, only the Landolt ring becomes invisible in the non-tested eye, while other parts, such as the edge of the optotype or the inner wall surface of the housing, are visible, and binocular vision is maintained.

FIG. 3 shows a sixth embodiment of the present invention.

9L, 9B are polarizing plates, 101. ．． TNl [crystal, 1iL, 11L, which has optical rotation of 10R and 90 is a polarizing plate 112
is a beam splitter 1l3L, and 13B is a polarizing plate. Therefore, polarizing plates 9L and 11L are used.

13L has a horizontal polarization direction, and polarizing plates 9B, 11B, and 13B have a vertical polarization direction, and the TN type liquid crystal 10L.

The indicator part of 10B moves from the horizontal direction to the vertical direction, respectively, when energized.
Change the polarization direction from vertical to horizontal.

Members 9L, 10L, 11L and members 9L, 10R.

11R is located at an optically conjugate position with respect to the beam splitter 12.

With this configuration, the TN liquid crystal 10L is visible only to the left eye, while the TN liquid crystal 10R is visible only to the right eye.

For binocular visual acuity measurement, TN type liquid crystal 10L'.

When 10B is energized, only each index portion appears dark.

In the case of measuring visual acuity with one eye) For example, in the case of measuring the left eye, it is sufficient to energize the TN type liquid crystal 10L and not energize the TN type liquid crystal 10R.

In this embodiment, unlike the second embodiment, when visual acuity is measured using one eye, the background of the non-tested eye does not become dark.

Note that the beam splitter 12 may be a half beam splitter, but it is even better if it is a polarizing beam splitter. It is also possible to test binocular vision functions such as stereopsis using . Note that in the above embodiments, a prism is used as the light refracting member, but a lens, for example, an eccentric lens, etc. may also be used.

As described above, according to the present invention, it is possible to visually see a visual target that is optically conjugate with both eyes, and the wall surface inside the housing near the visual target can also be seen, resulting in a three-dimensional field of view, which is a visual field in a natural state. This allows complete adjustment and accurate visual acuity measurement. ◇In general, the optotypes were placed 5m apart, but it is possible to set the optotypes closer than 5m while maintaining the same convergence angle. It is possible to provide a compact visual acuity meter.

The example diagrams, Figures 4 and 5, are diagrams showing the polarization direction of each part of the liquid crystal sight target. In the figure, 1 is the sight target, 2L, 2B are polarization prisms, 3L
51FL is the lens, 4 is the housing, 5, 8L, 8L.

9L, 9J11L, 11R, 13L, 13R are polarizing plates,
6, 7L, 7R, IOL, and 10B are nematic twist (TN) type liquid crystals, and 12 is a beam splitter.

Claims (1)

[Scope of Claims] (1) A visual acuity meter in which a visual target is apparently provided at a distance using a lens provided near the subject's eye, and a light refracting member is provided in one optical path, so that the left and right eyes are provided with the same optical target. - or a visual acuity meter characterized by presenting an optically conjugate visual target. (2) The visual acuity meter according to claim (1), wherein the light refracting member is an achromatic prism. (6) The visual acuity meter according to claim (1), wherein the optotype is a liquid crystal optotype with optical rotation. (4) The visual acuity meter according to claim (6), which allows the left and right eyes to see in different polarization states. (5) Visual acuity meter 0 according to claim (6), which allows the eye to be examined and the eye not to be examined to view with different polarization states.