JPS6036031A - Eye refractive force measuring apparatus - 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 an eye refractive power measurement device for objectively measuring the refractive power of an eye.

A device for objectively measuring the refractive power of the eye has been used for a long time, called a refractive meter, but in recent years, automatic refractive make, which has automated this, has 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, JP-A-56-1
As seen in Japanese Patent No. 131031, a method has also been proposed in which the exit angle of a ray of light exiting from the fundus of the eye from the pupil is measured using a position detection element without moving the lens system or other internal optical systems. This method has the excellent advantage of not requiring the lens system or internal optical system to be moved, but the measurement range is limited because the distance between the two beams must be such that two beams of light are simultaneously incident on the position detection element. It is considered that the signal is limited and the S/N ratio of the signal is relatively poor.

An object of the present invention is to be able to measure refractive power over a wide range with a position detection element with relatively low resolution, and to
The objective is to provide a highly accurate eye refractive power measurement device that can significantly improve the /N ratio.
・Means for projecting the image onto the fundus of the eye to be examined; means for extracting a plurality of reflected images on the fundus from around the incident site of the projected light flux to the pupil of the eye to be examined; A correction means that corrects the conjugate position of the position detection element according to the refractive power of the eye to be examined by changing the arrangement of a position detection element that detects the position and a lens system that projects the fundus reflected light onto the position detection element. It is characterized by having the following.

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 a condenser lens 2 and a fundus projection chart 3 are sequentially arranged along the optical axis.
, the relay lens 4, the aperture 5, the perforated mirror 6, and the objective lens 7 to reach the fundus Ef of the eye E to be examined. Also,
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 passed through the aperture plate 8, prism 9, relay lens 10, reflection mirror 11, The light enters the one-dimensional position detection element 13 via the 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 aperture 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. Then, the chart image is projected from infinity by the objective lens 7 and is focused on the fundus Ef.

The char 1 image reflected from the fundus Ef is once again imaged on the primary imaging plane F by the objective lens 7 from the periphery of the pupil Ep, and then reflected from the periphery of the perforated mirror 6, and then transferred to the aperture diaphragm plate 8. The light passes through the prism 9, is separated and deflected by the relay lens 10, is reflected by the reflection mirror 11, passes through the silitorical lens 12, and is imaged on the -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, prism 9 is the third
As shown in the figure, six wedge-shaped prism elements 9
It is composed of a to 9c and 9a' to 9c', and is configured to refract two images in the same direction.

As shown in Fig. 4, the fundus projection chart 3 consists of three wooden slits facing the three meridian directions and forming an angle of 120 degrees to each other.
a to 3C, and the fundus reflection images Ra, Rh, Rc
is prism 9 Te Ra, Ra', Rh, Rh, Re
, Re', and is imaged on the -dimensional force' detection element 131 as shown in FIG. This -dimensional position detecting element 13 consists of three detecting elements 13a to 13c, which are arranged almost radially, each having cylindrical lenses 12a to 12c, and slits 3a to 3.
The light in the longitudinal direction of C is focused in the lateral direction of the detection elements 13a to 13c.

Since each of the six apertures of the aperture diaphragm plate 8 forms one image, the prism 9 deflects and separates the images, and as shown in FIG.
Form two images each.

As a result, the output signal of one detection element 13 has two peaks as shown in FIG. When the refractive power of the eye E to be examined changes, the angle of the light beam emitted from the periphery of the pupil Ep changes, so that the two peaks shown in FIG. 6 move away from each other or approach each other. Therefore, by measuring the distance MD 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 using three detection elements 13a to 13c, the refractive power changes by 5 in2θ depending on the angle, so the spherical power, astigmatic power, and astigmatic angle can be determined respectively. You can

If the eye E to be examined is highly hyperopic or highly myopic, the image will be blurred and the distance 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 first
By moving the position of the relay lens 10 in the figure back and forth as shown by 10a and 10b to shift the conjugate position of the position detection element 13 back and forth from the conjugate plane of the emmetropic eye, the distance 11111D and the amount of blur can be corrected. .

That is, when the distance 1i11D becomes larger than a predetermined value, the relay lens 10 is moved to the lo'a side, and conversely, when the distance 1i11D becomes smaller than the predetermined value, the relay lens 10 is moved to 10b.
If the eye E is moved to the side, even if the eye E is highly hyperopic or myopic, the two signal waveforms will be as clear as in the case of an emmetropic eye, so by measuring again, the distance #D between the signals will be accurate. can be obtained.

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 a part of the . FIG. 9 shows an embodiment in that case, in which relay lenses 20a and 2 are used.
Three types of lenses, 0b and 20c, 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 allows a part of the optical system for detecting the fundus image to be moved or switched, so that even if the eye to be examined is highly hyperopic or highly myopic, it can be used to measure emmetropia. The refractive power can be measured in the same way, and a wide range of refractive powers can be measured using a position detection element with relatively low resolution.The amount of blur can also be reduced, and the S/N ratio of the signal can also be improved, resulting in highly accurate refractive power measurement. becomes possible.

[Brief explanation of the drawing]

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

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 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; By changing the arrangement of a position detection element that detects the exit angle of the image from the pupil at the position of the light receiving surface and a lens system that projects the fundus reflected light onto the position detection element, the conjugate position of the position detection element can be changed. An eye refractive power measuring device characterized by comprising a correction means for correcting according to the refractive power of an eye test. 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.