JPH0683705B2 - Eye refraction measuring device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an eye refraction index measuring apparatus for objectively measuring the eye refraction index of an eye to be inspected.

[Conventional technology]

As a conventional device for measuring the refractive index of the eye, a so-called split target image is formed by projecting a measurement target onto the fundus of the eye to be inspected through two points on the pupil of the eye to be inspected which are separated along a predetermined radial direction with respect to the eye. Is formed, and the degree of refraction in the radial direction is detected from the separation amount of the split target image at the fundus, and the detection is performed in at least three radial directions, and based on this result, the spherical power, astigmatism and astigmatism of the eye to be examined are obtained. There is known a device configured to calculate an axial angle.

[Problems to be solved by the invention]

The above-mentioned conventional eye refraction measuring device has a problem that the eye refraction cannot be measured in a short time in order to calculate the spherical power of the eye to be inspected, the astigmatic power and the astigmatic axis angle after the detection of the refractive power of the radial direction of 37. there were. In addition, the apparatus is inevitably movable in order to form the split target image, which complicates the configuration.

The present invention has been made in view of the above problems of the conventional eye refraction measuring device, which has a simple configuration including no movable part and which enables highly accurate eye refraction measurement in a short time. An object is to provide a degree measuring device.

[Means for solving problems]

The present invention has the following structural features to solve the above problems. That is, the present invention provides a light source unit and a projection optical system for projecting a light beam from the light source unit onto the fundus of the eye to be inspected to form an optotype image which becomes at least a part of a ring shape on the fundus of the eye to be inspected. A detection system for forming the optotype image on the fundus on the photoelectric detector by reflected light from the fundus, and the shape of the optotype image formed on the photoelectric detector by the signal from the photodetector. And an arithmetic system for calculating the refractive index of the subject's eye from the shape of this image.

〔Example〕

The optics of the eye refraction measuring apparatus according to an embodiment of the present invention, as shown in FIG. 1, the projection optical system 10 that forms a ring-shaped image on the fundus E _R of the eye E, formed on the fundus E _R The detection optical system 32 forms the formed ring-shaped image on the photoelectric conversion element 30.

The projection optical system 10 includes a point light source 16 disposed at a position conjugate with the fundus E _R on the projection optical axis 14 that coincides with the eye optical axis 12 to be examined, and a point light source.
A first imaging lens 18 that forms a primary image of 16 at the primary imaging point 19, and a pupil E _P between the first imaging lens 18 and the primary imaging point 19 A cap prism 20 with a reflecting prism disposed at a position conjugate with and a primary image forming point 19 and a secondary image of the point light source 16 formed on the fundus E _R between the eye E to be examined. 2 imaging lens 22.

As shown in the side view A in FIG. 2 and the front view B, the reflection prism with a reflection prism 20 has a central reflection prism 50 inclined by 45 ° with respect to the optical axis 14, and a flat surface on one side and another surface on the other side. The conical surface is composed of a bulky prism 52 at the peripheral portion which becomes thicker toward the periphery. On the umbrella prism 52, a mask 53 having a ring-shaped transmission opening 53a is formed as a diaphragm member.

In the projection optical system 10, the light flux emitted from the point light source 16 in the above configuration is deflected in the direction away from the optical axis 14 by the umbrella prism 52 of the umbrella prism 20 after passing through the first imaging lens 18, and A ring-shaped primary image is formed at the next imaging point 19. The light flux forming the ring-shaped primary image passes through the second imaging lens 22, and then passes through the peripheral ring-shaped region of the eye E _{P to} be inspected, which is in a conjugate relationship with the bulk prism 20, to the fundus E _R. A secondary image is formed.

The detection optical system 32 includes the second imaging lens 22 and the umbrella prism 20.
Of the reflecting prism 50 and the third imaging lens 36 arranged on the detection optical axis 34 reflected by the reflecting prism 50.
An area sensor 60 is arranged at a position conjugate with the next imaging point 19.

In the detection optical system 32 having the above-described configuration, since the reflection prism 50 and the pupil E _{P of the} subject's eye are conjugate, the light flux reflected by the fundus E _R that forms the secondary image of the link is reflected by the subject's eye E _P. After passing through the central portion of the pupil E _P , that is, the region where the light flux due to the projection optical system 32 does not pass, it passes through the second imaging lens 22 and the third imaging position 62 at the same position as the primary imaging position 19 A ring-shaped tertiary image is formed on. The light flux forming the ring-shaped third-order image is reflected by the reflection prism 50, is bent, passes through the imaging lens 36, and forms a ring-shaped fourth-order image on the area sensor 60. The area sensor 60 is, for example, a two-dimensional CCD.

In the above-mentioned embodiment, the bulk prism 52 is formed so that it becomes thicker toward the peripheral edge, but conversely, it may be formed so that it becomes thinner toward the peripheral edge. In that case, the light beam transmitted by the umbrella prism 52 is deflected in a direction approaching the optical axis 14. The bulk prism 52, the plane 52 _{1-52 8} which is inclined as shown in FIG. 3 may be formed in a conical shape.
As the throttle member when using the mask 53 arranged in a ring-shaped transparent openings 53 ₁ to 53 ₈ to correspond to the plane of each.

When the ring-shaped secondary image formed on the fundus E _R , that is, the ring of the ring-shaped quaternary image formed on the area sensor 60, its size changes depending on the refractive index of the eye to be inspected, and when there is astigmatism Is an ellipse. That is, as shown in FIG. 4, when the coordinates x and y are assumed on the area sensor 60, the ring of the quaternary image is a major axis a, a minor shape b, and the major axis is an ellipse forming an angle θ with the x axis. If it is formed, the angle θ corresponds to the axis of astigmatism, a corresponds to the degree of refraction of the strong main diameter line of astigmatism, b corresponds to the degree of refraction of the weak main diameter line of astigmatism, and the size of the ellipse corresponds to the spherical power. Therefore, the degree of refraction of the subject's eye can be obtained by detecting the elliptical shape.

By the way, the general formula of the ellipse in the coordinate system shown in FIG. 3 is Ax ² + By ² + Cxy = 1 (1) Can be expressed as, so the coordinate values on the ellipse (x ₁ ,
y ₁ ), ..., (xi, yi), and based on this result, A, B, and C are calculated from the equation (1) by the least square method, and a, b, θ, and The refractive index of the optometry can be calculated.

The calculation system calculates the refractivity of the eye to be inspected from the output of the area sensor 60 based on the above calculation method. As shown in the block diagram of FIG. 5, the area sensor 60 controls the clock pulse of the microprocessor 100. In response to this, the area sensor 60 is connected to a drive circuit 102 that sequentially scans and drives it. The output of the area sensor 60 is input to the analog switch 104 in synchronization with the clock pulse. The analog switch 104 inputs the output from the area sensor 60 to the A / D converter 106 under the control of the microprocessor 100. The A / D converter 106 converts the input analog output from each sensor element of the area sensor 60 into a digital amount, and the digital amount is sequentially written to a predetermined address of the memory circuit 108 under the control of the microprocessor 100. Get caught.

The microprocessor 100 calculates the coordinate values (x ₁ , y ₁ ), ..., (xi, yi) by the coordinate calculation program of the program memory 110 based on the data stored in the storage circuit 108, and further Coordinate value (x ₁ , y ₁ ), ……, (xi, yi)
Based on the above, a, b, and θ are obtained by the arithmetic programs of the equations (1) and (2) of the program memory 110, and these are converted into the refractive index of the eye to be examined and input to the display interface 112. The display interface 112 converts the input refraction index data of the eye to a display signal and displays it.
It outputs to 114, and the display 114 displays this.

One of the modifications of the above embodiment is that the reflecting prism 50 is removed from the reflecting prism-equipped umbrella prism 20, and instead, a half mirror is obliquely provided between the umbrella prism 52 and the second imaging lens 22, A detection optical system is formed on the reflection optical axis of the half mirror.

〔The invention's effect〕

The present invention forms a ring-shaped image on the fundus by the light flux that has passed through the peripheral ring-shaped region of the pupil surface of the eye to be examined as described above, and obtains the degree of eye refraction from the shape of this ring-shaped image. It has an advantage that the measurement time is short and that the structure is simple because it is not necessary to rotate the measurement target projection system in each of a plurality of radial directions as in the conventional apparatus.

[Brief description of drawings]

FIG. 1 is an optical diagram of an eye refraction measuring apparatus which is an embodiment of the present invention, A in FIGS. 2 and 3 is an enlarged side view of a bulk prism with a reflecting prism, B is its front view, and FIG. FIG. 5 is a block diagram of the arithmetic system of the embodiment, which is an explanatory view of the measurement principle of the present invention. E: Eye to be inspected E _R: Fundus E _P: Pupil 10: Projection optical system 14: Projection optical axis 16: Point light source 18: First imaging lens 20: Shade prism with reflection prism 22 ... … Second imaging lens 30 …… Photoelectric conversion element 32 …… Detection optical system 50 …… Reflecting prism 52 …… Bass prism

Claims (3)

[Claims] 1. A light source section, and a projection optical system for projecting a light flux from the light source section onto a fundus of the eye to be examined to form an optotype image so as to form at least a ring-shaped part on the fundus of the eye to be examined. , A detection system for forming the optotype image on the fundus on the photoelectric detector by the reflected light from the fundus, and the shape of the optotype image formed on the photoelectric detector by the signal from the photoelectric detector. And an arithmetic system for calculating the refractive index of the subject's eye from the shape of this image. 2. The eye refractivity measuring apparatus according to claim 1, wherein the projection optical system has a ring-shaped diaphragm member arranged at a position substantially conjugate with the pupil of the eye to be inspected. 3. The eye refraction measuring apparatus according to claim 1, wherein the projection optical system has a diaphragm member arranged at a position substantially conjugate with an eye to be inspected and having a plurality of apertures arranged in a ring shape. .