Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Reexamination Certificate
1999-12-27
2001-02-27
Manuel, George (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
Reexamination Certificate
active
06193373
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a lighting system for illuminating the eye and more particularly to a lighting system for video based tracking and correcting for eye movement during vision correction treatments.
2. Description of Related Art
Pupil position data obtained by eye tracking systems is used to detect eye motion during vision correction treatments. Conventional video based eye tracking systems automatically recognize and track the position of eye positions based on landmarks present within an image of a human eye. Such equipment requires illumination of the eye by infrared (IR) light. IR light typically 850 to 930 nanometers (nm) is used because it provides a good picture contrast between the pupil and iris. Additionally, the use of IR light decouples this lighting source from other visual sources which do not contain the infrared wavelengths.
The eye, illuminated by invisible IR light, is scanned by an infrared sensitive video camera. Under normal conditions, the pupil of the eye appears as a dark hole to the illumination. The dark pupil image is input to a real-time eye tracking system consisting of a digital image processor that outputs pupil size and position coordinates relative to the scan of the camera. The eye tracking system includes a circuit and processor designed to acquire and track the dark pupil position even in the presence of shadows or other clutter normally found in images of the eye.
FIG. 1
shows a conventional eye tracking system including illumination of the eye during laser vision correction surgery. The conventional illumination system includes one or two infrared light bundles
10
, mounted on a central hub
12
, to illuminate the eye for tracking by the eye tracking system. The path of a visible light beam used during vision correction treatments is shown at
14
. A camera
18
, sensitive to IR illuminations and fixed with respect to the subject's head, scans the eye to provide a video image for tracking the position of the eye.
Conventional illumination systems such as that shown in of
FIG. 1
require that light bundles
10
be relatively close to the eye in order to achieve an evenly distributed illumination. Generally, the light bundles
10
are about 80 millimeters (mm) from the eye being treated, as shown by the dimension A in FIG.
1
. This narrow spacing is a significant disadvantage because the light bundles
10
may interfere with the physician's hands either prior to or during the actual vision correction treatment. Additionally, the physician's hands can inadvertently block light emitted from one or both of the light bundles
10
causing a system efficacy and/or safety problem. Under certain circumstances, the patient's brow or nose can block light emitted from the light bundles
10
causing uneven illumination of the eye.
Additionally, conventional illumination systems such as that shown in
FIG. 1
require the light bundles
10
to be within 0 to +/−20 degrees to the visual axis in order to achieve generally presumption of an even illumination. If not, the light bundles
10
must be painstakingly adjusted for each patient at the time of treatment to achieve the best possible illumination based on the shape of that particular patient's face, eyes, etc. This is a time-consuming process and may result in errors.
However, even if the light bundles
10
are positioned within the conventionally preferred 0 to +/−20 degrees to the visual axis, there is an additional problem caused by specular reflections.
FIGS. 2 and 3
show specular reflections
21
at an eye
17
caused by any illumination system composed of point sources, e.g. light bundles
10
. Because of the relatively narrow angle (0 to +/−20 degrees) at which the light beams
19
(
FIG. 3
) are delivered, the specular reflections
21
can occur either within the pupil
18
or even worse at the pupil/iris border
20
. This makes the machine vision computer task of defining the pupil/iris border
20
much more complex and error prone.
The system shown in
FIG. 1
was originally designed for research studies of normal eyes in which the epithelium is intact with a tear layer providing distinct specular reflections. These conditions no longer hold true for current laser vision correction techniques. In particular, either the epithelium is removed under a technique called surface Photorefractive Keratectomy (PRK), or a flap is cut with a microkeratome, the flap is folded back, and the treatment is performed on the underlying stromal layer (called LASIK). Both LASIK and PRK markedly affect Illumination for eye tracking systems. The eye, rather than being shiny and smooth, becomes dryer and more diffusely reflective. This often leads to additional time-consuming physician adjustment of the light bundles
10
during a critical time period of the surgery.
Another problem exists with conventional eye tracking lighting systems when used with laser vision correction treatments. An ablating laser beam dries and roughens the eye surface further obscuring the camera's view of the pupil/iris border
20
and the peripheral limbal border. Empirically, this disadvantageous effect is accentuated by relatively coaxial lighting provided by singular light sources placed close to the eye at angles of less that +/−20 degrees.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a lighting system for illuminating the eye during vision correction treatments that does not physically interfere with preoperative and postoperative procedures, requires little or no physical adjustment, is insensitive to inadvertent light blockage, and minimizes or eliminates disadvantageous specular reflections at the pupil/iris border. These objects are attained in accordance with the principles of the present invention by providing a method and system which includes a generally arcuate main body. The main body is constructed, and arranged to be mounted in spaced relation to an eye to be tracked. An infrared light source is carried by the main body on at least a portion of its inner circumferential surface to direct infrared light toward the eye being treated at an angle from about 20 to 45 degrees with respect to an iris base plane of the eye being tracked.
REFERENCES:
patent: 2480737 (1949-08-01), Jayle
patent: 3074407 (1963-01-01), Moon
patent: 3476112 (1969-11-01), Elstein
patent: 3697889 (1972-10-01), Dewey, Jr.
patent: 3743965 (1973-07-01), Offner
patent: 3848104 (1974-11-01), Locke
patent: 3938058 (1976-02-01), Yamamoto
patent: 3966310 (1976-06-01), Larson
patent: 3982541 (1976-09-01), L'Esperance, Jr.
patent: 3983507 (1976-09-01), Tang et al.
patent: 4169663 (1979-10-01), Murr
patent: 4180751 (1979-12-01), Ammann
patent: 4349907 (1982-09-01), Campillo et al.
patent: 4386428 (1983-05-01), Baer
patent: 4423728 (1984-01-01), Lieberman
patent: 4461294 (1984-07-01), Baron
patent: 4477159 (1984-10-01), Mizuno et al.
patent: 4520816 (1985-06-01), Schachar et al.
patent: 4526171 (1985-07-01), Schachar
patent: 4538608 (1985-09-01), L'Esperance, Jr.
patent: 4546773 (1985-10-01), Kremer et al.
patent: 4573467 (1986-03-01), Rich et al.
patent: 4580559 (1986-04-01), L'Esperance, Jr.
patent: 4598714 (1986-07-01), Kremer et al.
patent: 4619259 (1986-10-01), Graybill et al.
patent: 4633866 (1987-01-01), Peyman et al.
patent: 4641349 (1987-02-01), Flom et al.
patent: 4653495 (1987-03-01), Nanaumi
patent: 4662370 (1987-05-01), Hoffman et al.
patent: 4665913 (1987-05-01), L'Esperance, Jr.
patent: 4669466 (1987-06-01), L'Esperance, Jr.
patent: 4688570 (1987-08-01), Kramer et al.
patent: 4718418 (1988-01-01), L'Esperance, Jr.
patent: 4720189 (1988-01-01), Heyman et al.
patent: 4721379 (1988-01-01), L'Esperance, Jr.
patent: 4729372 (1988-03-01), L'Esperance, Jr.
patent: 4729373 (1988-03-01), Peyman
patent: 4732148 (1988-03-01), L'Esperance, Jr.
patent: 4755043 (1988-07-01), Carter
patent: 4764930 (1988-08-01), Bille et al.
patent: 4770172 (1988-09-01), L
Apple Howard P.
Han Xiaofeng
Nevitt Martin P.
Bollman William H.
LaserSight Technologies Inc.
Manuel George
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