Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Reexamination Certificate
2001-10-05
2004-09-14
Manuel, George (Department: 3762)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
Reexamination Certificate
active
06789899
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an eye's optical characteristic measuring system for measuring an optical characteristic of an ocular optical system by determining a light amount intensity distribution of an index image, which is projected to a fundus of an eye under testing.
In the past, an eye's optical characteristic measuring system has been known. In this conventional type system, an index image such as a pinhole image is projected to a fundus of an eye under testing. The index image is formed on a photoelectric detector from the reflected light beam. Based on a light amount intensity distribution characteristic of the index image, an eye's optical characteristic of the ocular optical system of the eye under testing is measured.
In this conventional type eye's optical characteristic measuring system, a primary index image is formed on the fundus by a light beam passing through the ocular optical system from a cornea to the fundus. The reflected light beam from the primary index image passes through the ocular optical system again, and a secondary index image is formed on the photoelectric detector. Based on a signal from the photoelectric detector, the 2-dimensional light amount intensity distribution characteristic of the secondary index image is measured. From the result of the measurement, an optical characteristic (PSF) (e.g. a point image intensity distribution function) of the ocular optical system of the eye under testing is calculated. It is advantageous in that, based on this optical characteristic, the index image formed on the fundus of the eye under testing can be calculated and displayed as a simulation image.
All of the light beam projected to the fundus of the eye under testing are not necessarily reflected. A part of the light beam enters from the surface of the fundus into a superficial layer. Thus, scattering reflection (the so-called bleeding reflection) occurs.
The degree of deterioration of the image caused by the bleeding reflection (scattering reflection) at the fundus of the eye is expressed as the optical characteristic of the fundus. A system for quantitatively measuring the optical characteristic of the fundus has not been proposed so far.
Therefore, in the conventional type eye's optical characteristic measuring system, the secondary index image includs the influence of deterioration of the image caused by the scattering reflection at the fundus. When the scattering reflection is received at the photoelectric detector together with the reflected light beam, it is turned to a noise in the light amount intensity distribution of the secondary index image, and the accurate eye's optical characteristic of the ocular optical system cannot be obtained.
SUMMARY OF THE INVENTION
It is a first object of the present invention to provide an eye's optical characteristic measuring system, by which it is possible to measure an amount to indicate a condition of deterioration caused by the scattering reflection at the fundus of the eye under testing, i.e. for quantitatively measuring an optical characteristic of the fundus. It is a second object of the present invention to provide a system, which can calculate and display a simulation image at real time, which a subject person recognizes at any focusing position as desired, based on the optical characteristic of the fundus thus obtained and based on the light amount intensity distribution of the secondary index image on the photoelectric detector.
To attain the above objects, the eye's optical characteristic measuring system of the present invention comprises a projection system for projecting a primary index image on fundus of an eye under testing, a photodetection system for forming a secondary index image on a photoelectric detector from a reflection light beam of the primary index image, a detection system for measuring a light amount intensity distribution characteristic of the secondary index image based on a signal from the photoelectric detector, a correction optical system arranged in an optical path shared in common with the photodetection system and the detection system and for focusing the primary index image on the fundus of the eye under testing in correcting condition according to ocular refractive characteristic of the eye under testing, and a light beam switching means for switching over to a first condition to guide the reflection light beam including the scattering reflection light beam from the fundus of the eye under testing to the photoelectric detector and to a second condition to guide only the totally reflected light beam from the fundus of the eye under testing to the photoelectric detector, wherein the system is designed in such manner that light amount intensity distribution characteristics of the secondary index images formed respectively by two light beams selected by the light beam switching means can be measured based on signals from the photoelectric detector under the condition corrected by the correction optical system. Also, the present invention provides an eye's optical characteristic measuring system as described above, wherein there is provided an arithmetic unit for calculating optical characteristic of fundus of an eye from light amount intensity distribution characteristics of the two secondary index images. Further, the present invention provides an eye's optical characteristic measuring system as described above, wherein there is provided a simulation image calculating means for calculating a primary index image on the fundus as recognized by a subject person under testing from an optical characteristic of the fundus as calculated in advance and from a light amount intensity distribution characteristic of the secondary index image when a first photodetection condition is selected.
REFERENCES:
patent: 5751396 (1998-05-01), Masuda et al.
patent: 6629761 (2003-10-01), Hirohara et al.
Kobayashi Katsuhiko
Shibutani Masahiro
Takeuchi Gaku
Kabushiki Kaisha TOPCON
Nields & Lemack
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