JPS6254493B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an eye refractive power measurement device for objectively measuring the refractive power of an eye.

A device that objectively measures the refractive power of the eye is called a refractometer and has been used for a long time.
In recent years, autorefractometers that automate this process have become popular. Most of these instruments generally move and rotate a lens system within the instrument to automatically determine the conjugate position with the fundus of the eye to be examined. However, recently, as seen in Japanese Patent Application Laid-Open No. 161031/1983, the angle of exit of the pupil of the light rays exiting from the fundus of the eye is measured using a position detection element without moving the lens system or other internal optical systems. A method has also been proposed. This method has the excellent advantage of not having to move the lens system or internal optical system, but it requires a certain distance between the two light beams that simultaneously enter the position sensing element, which makes measurement difficult. It is possible that the range is limited and the S/N ratio of the signal is relatively poor.

The purpose of the present invention is to expand the measurement range and significantly increase the S/N ratio of the signal by adding an extremely simple mechanism of chopping the aperture at a position conjugate to the pupil of the eye to be examined. The purpose is to provide a highly accurate eye refractive power measurement device that can be improved. An eye refractive power measuring device having a means for taking out a plurality of reflected images on the fundus, and a detection means for detecting the exit angle from the pupil of the fundus reflected image based on the position of the light receiving surface, the pupil conjugate corresponding to the measurement meridian. It is characterized by having means for arbitrarily shielding a part of the surface.

The present invention will be explained in detail below based on illustrated embodiments.

In FIG. 1, a light beam emitted from a light emitting element 1 such as a light emitting diode, which is a light source, passes through a condenser lens 2, a fundus projection chart 3, a relay lens 4, and an aperture diaphragm, which are sequentially arranged along the optical axis to the left. 5. The light passes through the perforated mirror 6 and the objective lens 7 and reaches the fundus Ef of the eye E to be examined. Furthermore, the light beam reflected by the fundus Ef travels to the right along the optical axis, passes through the objective lens 7, is reflected by the perforated mirror 6, and is sequentially transferred to the aperture plate 8, relay lens 9, prism 10,
The light enters a one-dimensional position detection element 13 via a reflection mirror 11 and a cylindrical lens 12.

The light beam from the light emitting element 1 passes through a condenser lens 2 and illuminates a fundus projection chart 3, and the fundus projection chart 3 is imaged on a primary imaging plane F by a relay lens 4. Further, the light source image is once formed on the diaphragm 5, and then formed on the pupil Ep of the eye E to be examined through the aperture of the perforated mirror 6 by the objective lens 7, thereby illuminating the fundus Ef. The chart image is then projected from infinity by the objective lens 7 and focused on the fundus Ef. The chart image reflected by the fundus Ef is once again formed from the periphery of the pupil Ep on the primary imaging plane F by the objective lens 7, then reflected by the periphery of the perforated mirror 6, and then passed through the aperture diaphragm plate 8. The light is then separated and deflected by the relay lens 9 and the prism 10, reflected by the mirror 11, passes through the cylindrical lens 12, and is imaged onto the one-dimensional position detection element 13.

The aperture diaphragm plate 8 has, for example, annular openings 8a to 8c at equal intervals as shown in FIG.
4, and is inserted into the optical path between the perforated mirror 6 and the relay lens 9 so that the rotation center O of the aperture plate 8 coincides with the optical axis. Further, the prism 10 includes six wedge-shaped prism elements 10a, 10a', 10a, as illustrated in FIG.
b, 10b', 10c, and 10c', and two images corresponding to each are refracted in the same direction.

The fundus projection chart 3 is as shown in FIG.
The fundus reflection images Ra,
Rb and Rc are further separated into two pieces each by the prism 10 to become Ra, Ra', Rb, Rb', Rc, and Rc', which are imaged on the one-dimensional position detection element 13 as shown in FIG. . The one-dimensional position detection element 13 has three elements 1
3a to 13c are arranged almost radially as shown in FIG.
a~12c are correspondingly arranged, and slits 3a~
The light in the longitudinal direction of element 3c is focused on the transverse direction of elements 13a to 13c.

Fundus reflection images Ra, Rb, and Rc formed when the apertures 8a to 8c of the aperture diaphragm plate 8 overlap the prism elements 10a to 10c are shown as solid lines in FIG. Further, when the openings 8a to 8c overlap the prism elements 10a' to 10c', the openings become Ra', Rb', and Rc' shown by broken lines. The intervals between the fundus reflection images Ra and Ra', Rb and Rb', and Rc and Rc' correspond to the eye refractive power of the meridian in the direction of each detection element.

Now, focusing on the detection element 13a, for example, the signal when the aperture 8a overlaps the prism 10a is as shown in FIG. 6a. Similarly, when it overlaps the prism 10a', it becomes as shown in FIG. 6b, and the refractive power can be determined by measuring the interval between the peaks of this output waveform.

If the subject eye is ametropic, this peak will shift;
Both peaks approach each other as shown in Figures 7a and 7b, and the image becomes blurred and the peaks become gentler. However, since signals are obtained one by one by rotation of the aperture diaphragm plate 8, that is, by chopping, there is no possibility that these peaks cannot be discriminated.

Regarding this point, if the prism 10 is not shielded by the aperture diaphragm plate 8, for example, the prism 1
When the images of 0a and 10a' are superimposed on the detection element 13a, the signal becomes as shown by the solid line in Figure 8, and the two peaks overlap, worsening the resolution, and the position of the peak also changes, causing measurement errors. However, the measurement range of the refractive power of the eye to be examined is also reduced.

If the eye refractive power of the three meridians in the direction of the detection element can be measured, the spherical power, which is the usual method of displaying the eye refractive power,
The astigmatic power and the astigmatic angle can be calculated and determined based on predetermined formulas.

In the embodiment, a mechanical means for rotating the aperture diaphragm plate 8' is used as means for shielding a part of the prism 10, but this can also be done by electrical means. FIG. 9 shows an example using liquid crystal, and in this case, the aperture diaphragm plate 8 has six liquid crystal elements 8a' to 8f' as shown in FIG. When ~8c' is in the state of transmitting light, 8d~8f is driven to block the light, and conversely, when 8d'~8f' is transmitting light, the liquid crystal is driven to block 8a'~8c'. Driver 15
It may be driven by.

In the previous embodiment, two cases were described in which the prism 10 is shielded mechanically and electrically. Therefore, the aperture diaphragm plate 8 can be modified into various configurations other than the above embodiment.

As explained above, in the eye refractive power measuring device according to the present invention, by alternately shielding a part of the pupillary conjugate plane for measurement, the measurement range can be expanded, the S/N ratio of the signal can be improved, and the resolution can be improved. The excellent effect of improving measurement accuracy is obtained.

[Brief explanation of the drawing]

The drawings show an embodiment of the eye refractive power measuring device according to the present invention, FIG. 1 is a configuration diagram thereof, FIG. 2 is a plan view of an aperture plate, FIG. 3 a is a plan view of a prism, and FIG. 3 b is a cross section thereof. Figure 4 is a plan view of the fundus projection chart, Figure 5 is an explanatory diagram of the relationship between the detection element and the fundus reflection image, Figures 6a, b and 7a, b are the signal waveforms of the detection element. Figure 8 is a signal waveform diagram when the prism is not shielded, Figure 9 is a configuration diagram of another embodiment,
FIG. 10 is a plan view of the aperture diaphragm plate. Code 1 is a light emitting element, 2 is a condenser lens, 3
is a fundus projection chart, 4 is a relay lens, 5 is an aperture, 6 is a mirror with holes, 7 is an objective lens, 8 is an aperture stop plate, 10 is a prism, 12 is a cylindrical lens, 13 is a one-dimensional position detection element, 14 1 is a motor, and 15 is a liquid crystal driver.

Claims (1)

[Scope of Claims] 1. A means for projecting a fundus projection chart onto the fundus of the eye to be examined, a means for extracting a plurality of reflected images on the fundus from around the area where the projected light flux enters the pupil of the eye to be examined, and a fundus reflection chart. An eye refractive power measuring device having a detection means for detecting the exit angle of an image from the pupil at the position of the light receiving surface, and comprising means for arbitrarily shielding a part of the pupil conjugate plane corresponding to the measurement meridian. An eye refractive power measurement device characterized by: 2. The eye refractive power measuring device according to claim 1, wherein the means for shielding a part of the pupil conjugate plane is a diaphragm plate having an aperture in part and rotating around the optical axis. 3. Claim 1, wherein the means for shielding a part of the pupil conjugate plane is electrical means using liquid crystal.
The eye refractive power measuring device described in Section 1.