Camera, Fundus, Fiber Optic
Saturday, September 02, 2006
A Fiber Optic Fundus Camera has been designed and developed where the cameras image plane detects light scattered by red blood cells. A Laser Diode light beam (810nm, 60mW at the cornea) is projected to the eye through the Fundus Camera
The Laser Diode is attached to the Fundus Camera housing, which also contains the collimating optics. The laser light beam is projected through the Fundus Camera and is deflected by a prism cube. Lens defocuses the laser light beam to obtain a diameter of 300um coming from the Camera, with a resulting power of 60mW at the cornea. A portion of scattered light emerges from the eye pupil. The scatted light passes through the hole in the mirror and is deflected by another mirror, and focused on the Fiber Optic input aperture. This Fiber Optic aperture is placed in a plane conjugate with the retina. Precise positioning of the Fiber Optic aperture is by a motorized x-y microdrive stage.
The image of the Fiber Optic aperture is viewed on a video camera monitor sensitive to near-infrared light. To obtain the position of the eye relative to the Fundus Camera requires an illumination system focused in the pupil plane of the eye. This can be performed with white light (Halogen lamp) before the actual measurements are taken. A filter with a transmission of 1% at 810nm is placed between the eye and the video camera to avoid saturation of the video camera by the scattered light of the laser light beam.
Source: Optical Engineer, Vol. 34 (3), March 1995, Article by Charles E. Riva and Benno L. Petrig, University of Pennsylvania
Reference:
1) Scheie Eye Institute, Department of Ophthalmology, Philadelphia, Pennsylvania
2) Institut de Recherches en Ophthalmologie, 64 Avenue Grand Champsec, CH-1950 Sion, Switzerland;
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posted by JD52 @ 8:23 PM,
