JPH01293841A - Reflectometer - Google Patents

Abstract

PURPOSE:To calculate a highly accurate ophthalmic refraction value, by irradiating the center part of an eyeball and that of the eyeground with spot light and taking out the reflected luminous flux thereof from the periphery of the pupil to form ring- shaped luminous flux and forming an image on an area sensor. CONSTITUTION:The luminous flux emitted from a light source 1 passes through a lens 4, a circular iris 3 and the aperture part of a perforated mirror 2 and further passes through the center part of the pupil Ep of an eye E to be examined to project spot like luminous flux on the eyeground Er. The reflected luminous flux thereof again passes through an objective lens 1 and is reflected by the perforated mirror 2 to obtain a ring-shaped image on an area sensor 8 by an image forming optical member 8 through a lens 6 and a ring-shaped iris 7. The dimension and shape of the ring-shaped image obtained on the area sensor 9 are changed according to the degree of pseudomyopia, hypermetropia or astigmatism and, for example, in the case of hypermetropia, a ring-shaped image Ib having a diameter larger than that of the ring-shaped image Ia in the case of stigmatism is obtained and, in the case of astigmatism, a ring-shaped image Ic becomes oval and a degree of astigmatism can be calculated from the ratio of the long and short diameters of an oval and the angle thereof can be calculated from the diameter line direction of the oval.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a refractometer used for measuring the refractive value of an eyeball in an ophthalmology clinic, an eyeglass store, or the like.

[Prior Art] Conventionally, the fundus of the eye to be examined is irradiated with a ring-shaped light beam from the periphery of the pupil of the eye to be examined, and the reflected light beam from the fundus is imaged on an area sensor such as a COD. Measurement methods are known in which ocular refraction values are obtained by changes in size and shape. However, refractometers using this method do not measure using the center of the fundus, so when measuring an eye with different refractive values at the center and periphery of the fundus, it is difficult to accurately measure the refractometer. It is difficult to calculate the exact value.

[Object of the Invention] The object of the present invention is to eliminate the drawbacks of the above-mentioned conventional examples, to allow light to enter the fundus from the center of the fundus, and to make it possible to measure ocular refraction values with high precision using the reflected light flux from the fundus. The objective is to provide a refractometer with

[Summary of the Invention] The gist of the present invention for achieving the above-mentioned object is to provide a projection optical system that projects a spot light beam from the center of the pupil onto the fundus of an eye to be examined, and a projection optical system that projects a light beam of the spot light beam reflected by the fundus to the periphery of the pupil. This refractometer is characterized in that it has a photographing optical system that is taken out in a ring shape from the refractometer and guided onto a two-dimensional area sensor.

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

FIG. 1 shows a basic configuration diagram of a refractometer according to the present invention, which includes an objective lens 1 on the ocular axis facing the eye E to be examined, a perforated mirror 2 having an aperture in the center, and a circular aperture in the center. A diaphragm 3, a lens 4, and a light source 5 are arranged in this order. Further, on the optical axis in the reflection direction of the perforated mirror 2, a lens 6, a ring-shaped diaphragm 7, an imaging optical member 8, and an area sensor 9 such as a COD are sequentially installed. Note that the aperture 3.7 is positioned through the objective lens 1 so as to be conjugate with the pupil Ep of the eye E to be examined. The diaphragm 7 has a ring-shaped opening 7a as shown in FIG. 2, and the imaging optical member 8 has a ring-shaped lens 8a having approximately the same shape as the ring-shaped diaphragm 7, as shown in FIG. A ring-shaped lens 8a is provided.
The area sensor 9 is positioned at the focal point of the image.

First, the light beam emitted from the light source 1 passes through the lens 4 and the circular diaphragm 3, passes through the hole in the perforated mirror 2, passes through the center of the pupil EP of the eye E through the objective lens 1, and reaches the fundus Er. A spot-shaped light beam is projected onto the screen. The reflected light flux passes through the objective lens 1 again, is reflected by the perforated mirror 2, passes through the lens 6 and the ring-shaped diaphragm 7, and forms a ring-shaped image on the area sensor 9 by the imaging optical member 8.

4(a), (b), and (C) are ring-shaped images formed on the area sensor 9, and the ring-shaped lens 8
The condensing action of a creates a ring-shaped image of the strip, which facilitates shape analysis. Note that, in principle, a member that does not have a light condensing function, such as the ring-shaped lens 8a, can be used as the imaging optical member 8.

In this way, the size and shape of the ring-shaped image obtained on the area sensor 9 change depending on the degree of myopia, farsightedness, astigmatism, etc. For example, if FIG. 4(a) is the ring-shaped image Ia of emmetropia, , in the case of hyperopia, a ring-shaped image I having a larger diameter than the ring-shaped image Ia in the case of emmetropia is shown in FIG. 4(b).
b, and in the case of myopia, the ring-shaped image is smaller in diameter than in the case of emmetropia. In addition, the ring-shaped image Ia in the case of emmetropia
The difference between the magnitude of In addition, in the case of astigmatism, the ring-shaped image Ic becomes an ellipse as shown in Fig. 4 (C), and the degree of astigmatism is determined from the ratio of the major axis and minor axis of the ellipse, and the astigmatism angle is determined from the direction of the radial line of the ellipse. be able to.

FIG. 5 shows another embodiment of the imaging optical member 8, which is constructed using a conical prism 8b and a lens 8C instead of the ring-shaped lens 8a, and similarly forms a ring-shaped image on the area sensor 9. Obtainable. Further, the area sensor 9 is preferably a two-dimensional sensor array, but a television image pickup tube may be used and a video signal may be used. In this case, appropriate image processing is performed to calculate the ring shape.

[Effects of the Invention] As explained above, the refractometer according to the present invention has the following effects:
A spot light is irradiated to the center of the eyeball and fundus, and the reflected light beam is extracted from the periphery of the pupil and imaged on the area sensor as a ring-shaped light beam, allowing for calculation of refraction values with higher accuracy than conventional methods. Is possible.

[Brief explanation of the drawing]

The drawings show an embodiment of a refractometer according to the invention,
Figure 1 is a basic configuration diagram, Figure 2 is a plan view of the ring-shaped diaphragm,
Fig. 3 is a plan view of the imaging optical member, Fig. 4(a),
(b) and (C) are diagrams of the shape of a ring-shaped image formed on the area sensor, and FIG. 5 is a configuration diagram of another optical member for imaging. Reference numeral 1 is the objective lens, 2 is the perforated mirror, 3 is the aperture, and 5
7 is a light source, 7 is a ring-shaped diaphragm, 8 is an imaging optical member, and 9 is an area sensor. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] 1. A projection optical system that projects a spot light beam from the center of the pupil onto the fundus of the eye to be examined, and a photographing optical system that extracts a ring-shaped light beam reflected from the spot light beam by the fundus from the periphery of the pupil and guides it onto a two-dimensional area sensor. A refractometer characterized by having a system.