JPH0197435A - Eye refractometer - Google Patents

Abstract

PURPOSE:To calculate an eye refraction value from the position of a two-dimensional spot image, by a method wherein each luminous flux is separated from an optical axis by the wedge prism arranged in the vicinity of a pupil conjugate position and received by one two-dimensional sensor array positioned on the conjugate surface of the eyeground. CONSTITUTION:The spot luminous flux reflected from the eyeground Er is passes through an objective lens 5 to be reflected by a perforated mirror 4 and reaches the light receiving system iris 6 present at the position conjugated with the pupil Ep. Since the light receiving system iris 6 has three openings 6a, 6b, 6c, three luminous fluxes taken out from three places of the peripheral part of the pupil are deflected in a direction separated from an optical axis by the wedge prisms 8a, 8b, 8c corresponding to the respective luminous fluxes of a deflecting prism 8. In order to calculate the refraction value of an eye E to be examined, two-dimensional coordinates of spot images 6A, 6B, 6C are calculated diopter is calculated from said coordinates. The refraction value of an eye consists of three values of spherical power, astigmatic power and an astigmatic degree and, since a change in a diameter direction is supposed as a sine wave like one, when the diffraction values of three diameter lines are calculated, the refraction value of the eye can be calculated thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an eye refractometer for measuring the refractive value of an eye to be examined.

[Prior art] As a conventional general eye refractometer, for example, Japanese Patent Application Laid-Open No. 56-1
As disclosed in Japanese Patent No. 61031, a method is known in which a one-dimensional sensor array is arranged in each of the two radial directions to be measured and the eye refraction value is determined based on the position of the light beam in that direction. Since the method requires three one-dimensional sensor arrays, it is structurally complex and has the disadvantage that mutual adjustment of the sensor arrays is difficult.

[Object of the Invention] In order to improve such conventional drawbacks, the object of the present invention is to make it possible to obtain an eye refraction value by using only one two-dimensional sensor array as a detector, and to reduce the need for movable parts and adjustment parts. The object of the present invention is to provide an ocular refractometer with a simple structure that does not require.

[Summary of the Invention] The gist of the present invention to achieve the above-mentioned object is to arrange an aperture at a conjugate position of the pupil of the eye to be examined, which is created by an objective lens, and to direct a light flux from the center of the pupil to the fundus of the eye to be examined. A projection optical system that projects the light onto the fundus, and extracts the fundus reflected light of the projected light flux from at least three locations around the pupil, separates each light flux from the optical axis using a wedge prism placed near the pupil conjugate position, and positions it on the fundus conjugate plane. The eye refractometer is characterized in that it comprises a light receiving optical system that causes one two-dimensional sensor array to receive light, and determines an eye refraction value from a two-dimensional spot image position on the two-dimensional sensor array.

[Embodiments of the invention] The present invention will be explained in detail based on illustrated embodiments.

FIG. 1 shows an embodiment of an eye refractometer according to the present invention, in which a spot light source 1 such as an LED is provided on the optical axis L1 as a photographing optical system.
A lens 2, a projection system aperture 3 having a circular aperture 3a on the optical axis as shown in FIG. 2(a), and a hole having a hole in the center are arranged sequentially from the light source 1 toward the eye E. A clear mirror 4 and an objective lens 5 are arranged. Note that the spot light source 1 is preferably arranged on a conjugate plane of the fundus Er of the emmetropic eye to be examined, and the projection system diaphragm 3 is substantially conjugate to the pupil Ep of the eye E to be examined by the objective lens 5. perforated mirror 4
On the optical axis L2 on the reflection side of the
As shown in b), a light-receiving system having three apertures 6a, 6b, and 6c arranged equidistantly around the optical axis, a lens 7, and three imitation prisms 8a as shown in FIG. , 8
A deflection prism 8, which is a combination of sensors b and 8c, and a two-dimensional sensor array 9, such as a COD, are arranged in sequence. Here, the light receiving system aperture 6 is conjugate with the eye pupil Ep of the subject E, and the two-dimensional sensor array 9 is arranged in a plane conjugate with the fundus Er.

In this embodiment, the light beam emitted from the spot light source 1 is formed into an image by the lens 2 between the lens 2 and the objective lens 5, and further by the objective lens 5, the fundus Er of the eye E to be examined is
Projects a spot light beam onto.

The spot light beam reflected by the fundus Er passes through the objective lens 5, is reflected by the perforated mirror 4, and reaches the light receiving system aperture 6 located at a position conjugate with the pupil Ep. Since the light-receiving system diaphragm 6 has three apertures 6a, 6b, and 6c, the light beams are extracted from three locations around the pupil, and the three light beams thus extracted are directed to each of the deflection prisms 8. The beams are deflected away from the optical axis by corresponding wedge prisms 8a, 8b, and 8C. That is, the light beams passing through the apertures 6a, 6b, and 6c pass through the corresponding prisms 8a, 8b, and 8C, reach the two-dimensional sensor array 9, and as shown in FIG. Each spot image 6A
, 6B, and 6C. For example, the light beam from the aperture 6a passes through the prism 8a, where it is deflected in a direction perpendicular to the dividing line of the prisms 8b and 8c shown in FIG.

The light beams passing through the other apertures 6b and 6c are similarly deflected away from the optical axis.

In FIG. 4, the dotted lines and arrows indicate the directions in which the spot images 6A, 6B, and 6C move when the diopter of the eye E to be examined changes.1 When the diopter changes in the opposite direction, the spot images 6A
, 6B, and 6C will shift in the opposite direction to the arrow, and if there is astigmatism, they will shift away from the dotted line. To obtain the refractive value of the eye E, first, the two-dimensional coordinates of the spot images 6A, 6B, and 6C are obtained. If the two-dimensional sensor array 9 is an image pickup device of a television camera, the video signal may be used, and an appropriate threshold level is determined, binarized, and the spot center position is determined by calculation. Furthermore, signals for each element can also be used to obtain accurate values. After the coordinates are calculated by binarizing or multi-valued, the deopter is calculated from the coordinates.

The refractive value of the eye consists of three values: spherical power, astigmatic power, and astigmatic power, and the change in the radial direction is assumed to be sinusoidal, so once the refractive value of the two radial lines is determined, the rest is done by calculation. It can be calculated. Various methods are known for selecting these two radial lines. For example, in FIG. 2(b), if the direction connecting the optical axis L2 and each aperture 6a, 6b, 6c is taken, the dotted line in FIG. What is necessary is to calculate the movement of the spot images 6A, 6B, and 6C in the directions. In this case, the amount of movement from the emmetropic spot position is proportional to the refraction value in each radial direction.

Alternatively, the radial direction connecting the apertures 6a, 6b, 6c in FIG. The relative positions of 6A and 6C in the vertical direction represent the refraction value in this radial direction, and the refraction values in the other two radial directions can be determined in the same manner. If the deflection direction of the deflection prism 8 is perpendicular to the movement of the spot image with respect to the spherical power, that is, the dotted line direction in FIG. 4, the area of the two-dimensional sensor array 9 can be used effectively.

The above embodiment is a case where the light receiving system diaphragm 6 has three apertures, but the accuracy can be further improved by using one having six apertures 6a to 6f as shown in FIG. . Of course, in this case, the wedge prism of the deflecting prism 8 is also
The direction of deflection is preferably perpendicular to the movement of the spherical power, as in the embodiment of FIG.

FIG. 6 shows spot images 6A to 6F from each aperture 6a to 6f when the light receiving system aperture 6 as shown in FIG. 5 is used.
This shows 6F. In this way, spot image 6A~
The calculation becomes complicated when there are many 6Fs, but the spot image 6A
Since the amount of movement of ~6F is large, it is advantageous in terms of accuracy. That is, when using the horizontal relative positions of the spot images 6A and 6D from the horizontal refraction values r36a and 6d, the amount of movement is proportional to the interval between the extraction positions at the pupil Ep, so both ends of the pupil Ep are In this embodiment, the amount of movement is large and the accuracy can be easily improved. For other radial lines, the relative positions of spot images 6B and 6E, and 6C and 6F in the dotted line direction in FIG. 6 are used. Note that it is convenient to place the two-dimensional sensor array 9 on a plane conjugate with the fundus Er for emmetropia because the image is not blurred for emmetropia.

[Effects of the Invention] As explained above, the ocular refractometer according to the present invention only needs to use one two-dimensional sensor array as a detector, so there is no need for mutual adjustment of the sensors as in the conventional case. The structure is simplified by eliminating the need for moving parts and adjustment parts.

[Brief explanation of the drawing]

The drawings show an embodiment of the eye refractometer according to the present invention, in which Fig. 1 is an optical layout diagram, Figs. 2(a) and (b) are front views of the aperture of the projection system and light receiving system, respectively, and Fig. 3 is a front view of a deflection prism, FIG. 4 is an explanatory diagram of a spot image on a two-dimensional sensor array, FIG. 5 is a front view of another example of a light receiving system aperture, and FIG.
The figure is an explanatory diagram of a spot image on a two-dimensional sensor array. Symbol l is a spot light source, 2 is a lens, 3 is a projection system aperture,
4 is a perforated mirror, 5 is an objective lens, 6 is a light receiving system aperture,
7 is a lens, 8 is a deflection prism, and 9 is a two-dimensional sensor array. Patent applicant: Canon Co., Ltd. Figure 3 Figure 5 e bt Figure 4

Claims (1)

[Claims] 1. A projection optical system that has an aperture located at a conjugate position of the pupil of the subject's eye created by the objective lens and projects a spot light beam from the center of the pupil onto the fundus of the subject's eye;
A light-receiving optical system extracts the fundus reflected light of the projection light flux from a point, separates each light flux from the optical axis by a wedge prism placed near the pupil conjugate position, and receives the light on one two-dimensional sensor array located on the fundus conjugate plane. An eye refractometer, characterized in that an eye refraction value is determined from a two-dimensional spot image position on the two-dimensional sensor array.