JPH0336529B2 - - 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 electrically detect a position conjugate to 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 the measurement range is limited because the two light beams that simultaneously enter the position detection element must be separated by a certain distance. It is conceivable that the signal is limited and the S/N ratio of the signal is relatively poor.

An object of the present invention is to provide a highly accurate eye refractive power measurement device that can measure refractive power in a wide range with a position detection element with relatively low resolution and can significantly improve the signal-to-noise ratio. In particular, the gist is: a means for projecting a fundus projection chart onto the fundus of the eye to be examined; a means for extracting a reflected image on the fundus from an exit site different from the incident site of the projected light beam into the pupil of the eye to be examined; In an eye refractive power measuring device having a position detection element that detects the exit angle of an image from the pupil at the position of the light receiving surface, the position can be adjusted by changing the arrangement of the lens system that projects the fundus reflected light onto the position detection element. The present invention is characterized by comprising a correction means for correcting the conjugate position of the detection element according to the refractive power of the eye to be examined.

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, goes to the left, and is sequentially arranged along the optical axis through a condenser lens 2, a fundus projection chart 3, a relay lens 4, and an aperture. 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, prism 9, relay lens 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 imaged onto the fundus Ef projected from infinity by the objective lens 7.
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 reflection mirror 1 is separated and deflected by a prism 9 and a relay lens 10.
1 , passes through the cylindrical lens 12 , and forms an image on the one-dimensional position detection element 13 .

The aperture diaphragm plate 8 has, for example, annular apertures 8a to 8c and 8a' to 8c' as shown in FIG. 2, and is arranged at a position substantially conjugate to the pupil Ep. on the other hand,
As shown in FIG. 3, the prism 9 is composed of six wedge-shaped prism elements 9a to 9c and 9a' to 9c', and is adapted to refract two images in the same direction.

The fundus projection chart 3 is as shown in FIG.
It has three slits 3a to 3c facing the three meridian directions and making an angle of 120 degrees to each other, and this fundus reflection image
Ra, Rb, Rc are Ra, Ra′, Rb, Rb,
It is separated into Rc and Rc', and is imaged on the one-dimensional position detection element 13 as shown in FIG. This one-dimensional position detection element 13 has three detection elements 13a to 13c.
These elements are arranged approximately radially, and cylindrical lenses 12a to 12c are provided respectively, so that the light in the longitudinal direction of the slits 3a to 3c is condensed in the lateral direction of the detection elements 13a to 13c. .

The six apertures of the aperture diaphragm plate 8 each create one image, so the prism 9 deflects and separates the image into the fifth image.
As shown in the figure, two images are formed on each of the detection elements 13a to 13c of the one-dimensional position detection element 13.
As a result, the output signal of one detection element 13 is
As shown in the figure, it has two peaks. When the refractive power of the eye E changes, the pupil
Since the angle of the light flux emitted from the periphery of Ep changes,
The two peaks shown in FIG. 6 move away from each other or approach each other. Therefore, by measuring the distance D between these two peaks, the refractive power of the eye E in the direction of the detection element can be measured. As shown in FIG. 5, if the refractive power in the three meridian directions is measured with the three detection elements 13a to 13c, the refractive power changes by sin ² θ depending on the angle, so the spherical power, astigmatic power, and astigmatism can be determined. You can find each angle.

If the eye E to be examined is highly hyperopic or highly myopic, the image will be blurred and the distance D between the two peak signals will also change, so the signal waveforms will be as shown in Figures 7 and 8, respectively. becomes impossible to measure. Therefore, a part of the lens system that projects the fundus reflected light onto the position detection element 13, that is, the position of the relay lens 10 in FIG. By shifting forward or backward from the conjugate plane of the emmetropic eye, the distance D and the amount of blur can be corrected.

In other words, when the distance D becomes larger than a predetermined value, the relay lens 10 is moved to the 10a side, and when the distance D becomes smaller than the predetermined value, the relay lens 10 is moved to the 10b side. Even if the eye is highly hyperopic or myopic, the two signal waveforms will be clear as in the case of an emmetropic eye, so the distance D between the signals can be accurately obtained by measuring again.

In the above embodiment, a case was described in which a part of the lens system was moved in the optical axis direction as means for correcting the conjugate position of the position detection element 13 according to the refractive power of the eye E to be examined. Of course, the same effect can be achieved by replacing the parts. FIG. 9 shows an embodiment in that case, in which relay lenses 20a, 20b, 2
Three types of lenses (0c) are arranged interchangeably, and one of them is selected and switched according to the refractive power of the eye E to be measured.

In this way, the eye refractive power measuring device according to the present invention has the following features:
By making part of the optical system that detects the fundus image movable or switchable, even if the subject's eye is highly hyperopic or highly myopic, it can be measured in the same way as if it is emmetropic, and it can be measured at a position with relatively low resolution. It is possible to measure a wide range of refractive power with the detection element, the amount of blur can be reduced, and the S/N ratio of the signal is improved, making it possible to measure refractive power with high precision.

[Brief explanation of drawings]

The drawings show an embodiment of the eye refractive power measuring device according to the present invention, and FIG. 1 is a configuration diagram thereof, FIG. 2 is a plan view of an aperture plate, FIG. 3 is a front view of a prism, and FIG. 4 is a fundus. A plan view of the projection chart, FIG. 5 is an explanatory diagram of the relationship between the detection element and the fundus reflection image, and FIGS. 6 to 8
The figure is a signal waveform diagram of the detection element, and FIG. 9 is a configuration diagram of another embodiment. 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 perforated mirror, 7 is an objective lens, 8 is an aperture diaphragm plate, 9 is a prism, 10, 20a, 20
b, 20c are relay lenses, 12 is a cylindrical lens, and 13 is a one-dimensional position detection element.

Claims (1)

[Scope of Claims] 1. Means for projecting a fundus projection chart onto the fundus of the eye to be examined, means for extracting a reflected image on the fundus from an exit site different from the incident site of the projected light flux into the pupil of the eye to be examined, and a fundus reflected image. In an eye refractive power measuring device having a position detection element that detects the exit angle from the pupil at the position of the light receiving surface, the position detection can be performed by changing the arrangement of a lens system that projects the fundus reflected light onto the position detection element. 1. An eye refractive power measuring device comprising: a correction means for correcting a conjugate position of an element according to a refractive power of an eye to be examined. 2. The eye refractive power measuring device according to claim 1, wherein the correction means moves a part of the lens system in the optical axis direction. 3. The eye refractive power measuring device according to claim 1, wherein the correction means replaces a part of the lens system.