Drape for a surgical microscope with anti-halation window

Details Drape for a surgical microscope with anti-halation window Drape for a surgical microscope with anti-halation window

1999-11-26

2001-07-10

Nguyen, Thong (Department: 2872)

Optical: systems and elements

Barrel end eye guard

C359S601000, C359S608000, C359S510000

Reexamination Certificate

active

06257730

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to drapes for surgical microscopes.
BACKGROUND OF THE INVENTION
Surgical microscopes are typically covered with a disposable drape to prevent contamination of the microscope from the patient or contamination of the patient from the microscope. The drape comprises a flexible cover having a flat transparent window therein aligned with the objective lens of the microscope.
In many surgical microscopes the objective lens transmits light from a light source to the surgical site to illuminate the surgical site, and the objective lens also transmits the image of the surgical site to the optical path of the microscope.
The flat window in the drape allows light form the objective lens to pass to the surgical site, and it allows the image to pass from the surgical site to the objective lens. One problem encountered with conventional drapes is that the flat window will reflect some of the light that is transmitted from the objective lens back to the objective lens and into the optical or viewing path of the microscope. The reflected light impairs the image of the surgical site due to a phenomenon called halation. Anti reflective coatings can be applied to the window, but even with antireflective coatings, a substantial amount of light is reflected into the optical or viewing path. U.S. Pat. No. 5,608,574, incorporated herein by reference, discloses a flat slanted window. Tilting the window can also reduce the amount of light reflected into the optical or viewing path, but this introduces a distortion or astigmatism into the viewed image. (An astigmatism is a defocusing of the image along one axis). Also the slant of the drape lens reduces the clearance between the microscope and the surgical field, which may cause the surgeon to compromise and use a longer lens to allow adequate working space between the microscope and the surgical field. Some surgeons remove the window to avoid these problems, compromising the effectiveness of the drape.
Another problem experienced with flat windows is that to save cost these windows are made of molded plastic, and flat molded plastic parts tend to have irregular peaks and valleys on their surfaces. This surface irregularity introduces additional distortion into the image, and because it is essentially random, it is difficult for the eye to accommodate, resulting in a very poor image.
SUMMARY OF THE INVENTION
The drape of the present invention is adapted to be installed over a surgical microscope to isolate the surgical microscope from the surgical field. Generally, the drape of the present invention comprises a cover for covering a surgical microscope having a window therein adapted to be aligned with the objective lens of the microscope. However, the window is convexly curved. The convex configuration of the window reduces the amount of light reflected from the window back to the objective lens.
When properly installed on a surgical microscope, the drape of the present invention isolates the microscope from the surgical field. The window allows light form the objective lens to pass to the surgical site and allows the image to pass from the surgical site to the objective lens. The convex configuration of the window reduces the amount of reflected light received by the objective lens, reducing halation.
Another benefit of the concave/convex curved configuration of the window is that even if it is made out of molded plastic, any distortions tend to be in the radial direction. This does not affect the imagery of the optical surface, although it does affect the curvature and ultimately the magnifying power. Aberrations introduced by this type of shape are in a controlled direction and more easily accommodated by the eye.
Still another possible benefit of the concave/convex configuration of the window is that the shape of the window can be designated to cooperate with the optics of the microscope to increase the optical erformance of the microscope.


REFERENCES:
patent: 3402981 (1968-09-01), Cardone
patent: 3796477 (1974-03-01), Geraci
patent: 5311358 (1994-05-01), Pederson et al.
patent: 5386817 (1995-02-01), Jones
patent: 5467223 (1995-11-01), Cleveland, Jr. et al.
patent: 5526181 (1996-06-01), Kunick et al.
patent: 5608574 (1997-03-01), Heinrich

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