JPH02307426A - Photorefraction apparatus - Google Patents

Abstract

PURPOSE:To make a measurement with high accuracy possible by judging strength of a reflecting light in a pupil based on a shade pattern of a pupil image and an iris image and measuring an eye refractive value. CONSTITUTION:When an examined eye E is normal, all the light bundles from a pupil Ep are received on a lens and reach a recording medium 3 and the whole area in a pupil image P surrounded by an Aris image I on the recording medium 3 becomes bright. When the examined eye F is iongsightedness, a reflected light bundle from an eyeground Er disperses when it passes through the pupil and as only a light bundle from the central part of the pupil Ep reaches the lens 2, only the central part of the pupil image P on the recording medium 3 becomes bright. When the examined eye E is shortsightedness, as the reflected light bundle from the eyeground Er is condensed before a half mirror 1 after it passes through the pupil Ep and reaches the lens 2, only upper part of the pupil image P on the recording image 3 becomes bright. As described above, as a shade pattern of the pupil image P in the iris image 1 on the recording medium 3 becomes different depending on the refractive value of the pupil Ep of the examined eye E, measurement of eye refractive value can be done based on this shade pattern by using a pattern detecting device and an arithmetic device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a photoretraction device used, for example, in eye clinics and the like.

[Prior Art J] Conventionally, in a photorefraction device that measures the ocular refraction value by irradiating the fundus of the eye to be examined and capturing a shadow image of the pupil by the fundus reflected light, a strobe light source in the visible light range is generally used as the light source. If you want to measure astigmatism or improve the measurement accuracy of eye refraction values, you can change the direction of irradiation and take multiple images, or instill a mydriatic agent to enlarge the pupil. , the refraction value is measured after enlarging the shadow pattern of the U hole.

[Problem to be solved by the invention] However, in the conventional example having the above configuration,
Since the fundus of the subject's eye is irradiated with a luminous flux in the visible light range, visible light is absorbed by the melanin pigment contained in the fundus and iris, so the amount of melanin pigment contained varies depending on race and individual differences. The reflectance of the fundus of the eye and the iris is different, and an error is introduced into the ocular refraction value measured based on the light reflected from the fundus of the eye. In addition, because the chromatic aberration caused by the wavelength dispersion of the refractive index of the eyeball optical system disrupts the shadow pattern of the pupil of the subject's eye, a mydriatic is instilled into the eye to enlarge the pupil and measure the eye refraction value. However, there is a problem that the measurement accuracy does not improve.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the conventional example, reduce measurement errors in eye refraction values caused by racial and individual differences, and measure eye refraction with a high degree of refraction without using mydriatics. The object of the present invention is to provide a photorefraction device that can perform photorefraction.

[Means for Solving the Problems] In order to achieve the above object, the photorefraction device according to the present invention includes an illumination optical system that irradiates the fundus of the eye to be examined with near-infrared light, and an iris image and a pupil image. The eye refraction value of the eye to be examined is determined based on the shadow pattern of the iris image and the pupil image detected by the detection means.

[Operation] The photorefraction device having the above configuration uses near-infrared light as a light source to illuminate the fundus of the eye to be examined, and determines the brightness ratio between the iris image and the pupil image. To reduce racial and individual differences in reflectance, and further to reduce the influence of wavelength dispersion of the eyeball optical system.

[Example] The present invention will be explained in detail based on illustrated embodiments.

As shown in FIG. 1(a), a half mirror for the eye E to be examined! , a lens 2, a recording medium 3 consisting of a film, an image sensor, etc., and having sensitivity to near-infrared light, are sequentially installed on the optical axis 0 of the lens 2, and a little from the optical axis 0 on the side of the nof mirror 1. It consists of a strobe light source and an incandescent lamp with a visible cut filter attached at a distance, and weighs approximately 750-1000g.
A near-infrared light source 4 having an emission wavelength range of about m is provided. Note that the fundus Er and the light source 4 are conjugated through the lens 2, and the pupil Ep and the recording medium 3 are conjugated.

The near-infrared light beam projected from the light source 4 onto the fundus Er of the eye E to be examined is reflected by the fundus Er and exits the pupil Eρ, and then is reflected by the half mirror 1 and returns to the light source 4, or passes through the half mirror 1. However, the reflected light flux from the fundus E' illuminates the pupil EP from within the eyeball and also illuminates the iris Ei when exiting from the eye E. A pupil image and an iris image are formed.

When the eye E to be examined is normal, all the light flux from the pupil Ep is received by the lens 2 as shown in FIG. 1(a) and reaches the recording medium 3, and is recorded as shown in FIG. 1(b). The entire area within the pupil image P surrounded by the iris image ■ on the medium 3 becomes bright. However, if the eye E to be examined is hyperopic, the reflected light flux from the fundus Er diverges when passing through the pupil EP, as shown in FIG. Since only the light flux reaches the pupil image P of the recording medium 3J:, only the center of the pupil image P becomes bright, as shown in FIG. 2(b). Further, when the eye E to be examined is myopic, as shown in FIG. 3(a), the reflected light flux from the fundus Er passes through the pupil EP, is condensed in front of the half mirror 1, and reaches the lens 2. Therefore, as shown in FIG. 3(b), the pupil image P on the recording medium 3
Only the upper part of the screen becomes bright.

In this way, the shading pattern of the pupil image P in the iris image (■) on the recording medium 3 differs depending on the refractive value of the pupil EP of the eye E to be examined. can be used to measure ocular refraction values.

In addition, if another light source is provided at a position a little away from the optical axis 0 in a direction perpendicular to the drawing and images are taken sequentially, if the eye E to be examined has astigmatism, the recording medium 3
Since the shading pattern of the pupil image P with respect to the upper iris imager is different, it is possible to measure the astigmatism state and measure the ocular refraction value with high precision at the same time.

In addition, in the above-mentioned embodiment, the pupil Ep and the recording medium 3
are conjugated, but the fundus E in front of the pupil Ep
The eye refraction value may also be measured by photographing the reflected light flux from.

[Effects of the Invention] As explained above, the photorefraction device according to the present invention measures the ocular refraction value by determining the intensity of reflected light within the pupil based on the shadow pattern of the pupil image and the iris image. Highly accurate measurement becomes possible.

[Brief explanation of the drawing]

The drawings show an embodiment of the photorefraction device according to the present invention, in which FIG. 1(a) is a light flux diagram of a emmetropic type, FIG. 2(b) is an explanatory diagram of an image on a recording medium, and FIG. 2(a) is a hyperopic type. The luminous flux diagram of (
FIG. 3(b) is an explanatory diagram of the image on the recording medium, FIG. 3(a) is a luminous flux diagram of the myopia ratio, and FIG. 1 is a half mirror, 12 is a lens, 3 is a recording medium, 4
is a light source.

Claims (1)

[Claims] 1. An illumination optical system that irradiates the fundus of the eye to be examined with near-infrared light;
A photorefraction device comprising a detection means for detecting an iris image and a pupil image, and determining an ocular refraction value of an eye to be examined based on a shadow pattern of the iris image and pupil image detected by the detection means. .