Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Patent
1991-05-03
1993-01-05
Bovernick, Rodney B.
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
351221, A61B 310
Patent
active
051775115
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to an apparatus for producing images of an object and in particular for observing the rear portions of the eye.
Apparatuses for producing images of an object for observing the rear portions of the eye are well known in the art and are implemented with various equipment for producing images. By way of illustration, a number of laser-scanning cameras, laser-scanning microscopes and laser-scanning ophthalmoscopes have been proposed in medical technology.
Apparatuses of the known type have proven to be particularly advantageous when a comparatively large object has to be viewed through a small aperture arranged before the object. For example, when observing the rear portions of the eye, there arises the problem that the fundus must be illuminated and observed through the pupil of the eye and frequently through the not clear anterior media of the eye, where reflexes occur to produce image defects. Similar circumstances have been encountered in other cases of medical or technical application.
For this reason, fundus cameras have usually been employed in the past to observe the rear portions of the eye, in which the entrance pupil and the exit pupil were separated according to "GULLSTRAND" to suppress the so-called corneal reflex i.e. the part of the pupil of the eye used for the illumination surrounds ring-like the part used for observation.
Nonetheless, reflexes cannot be entirely suppressed when working with such fundus cameras. Moreover, the attainable resolution of approx. 15 .mu.m is often insufficient.
Therefore, it has repeatedly been proposed to employ apparatuses for observing the fundus of the eye, which do not illuminate expansive areas of the fundus of the eye, but rather scan as small as possible a spot with a focused illuminating light and detect the reflected light in relation to the scanning sequence. In this regard, reference is made, by way of illustration, to "The Foundations of Ophthalmology", Vol. VII, pp. 307/308, Yr. 1962, U.S. Pat. No. 4,213,678, EP-A-0 145 563 as well as Japanese patent publications 61-5730 and 50-138822.
The apparatuses described in the aforementioned references differ from one another in the pupil separation. The Japanese patent publication 61-5730 proposes a "GULLSTRAND separation", U.S. Pat. No. 4,213,678 an inverted "GULLSTRAND pupil," and the Japanese patent publication 50-138822 adjacent pupils as illumination and observation light.
In the apparatus for observing the rear portions of the eye described in EP-A-145 563, both the illumination light beam and the observation light beam are directed via a scanning device. A "double scanning system" of this type has the advantage that the reflected beam of light can be determined by means of a stationary detector with a relatively small surface.
The apparatuses mentioned in the preceding for observing the rear portions of the eye with "scanning illumination" have in common that the resolution of the received image is determined by the size of the "focus spot" (approx. 8-12 .mu.m) on the fundus of the eye and that the reflected light is received by a single detector with a more or less large field of view aperture for building up the image of the rear portions of the eye.
Further analysis of the returned light has not previously been considered.
The present invention is based on the recognition of the fact that apparatuses for producing images, in particular, due to special types of illumination and/or the analysis of the light scattered back according to most varied criteria permits gaining essential further ground-laying information about the object of which an image is to be made, for example the fundus of the eye, than is possible with any of the other known apparatuses.
Therefore, a primary object of the present invention is to improve an apparatus for producing images of an object hereto in such a fashion, that it is possible, by means of special types of illumination and/or the analysis of the light scattered back, to analyze the object to be im
REFERENCES:
patent: 4838679 (1989-06-01), Bille
Feuerstein Manfred
Klingbeil Ulrich
Kuhl Claus H.
Plesch Andreas
Bovernick Rodney B.
G. Rodenstock Instruments GmbH
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