Modeling and simulation of illumination effects for the evaluation
of microvessels of the conjunctiva.
Wick, Carl E., Murray H. Loew, and Joseph Kurantsin-Mills.
Department of Weapons and Systems Engineering, U.S. Naval Academy
Annapolis, MD 21402, Department of Electrical Engineering and
Computer Science, The George Washington University, Washington DC
20052, Department of Medicine and Department of Physiology, The
George Washington University Medical Center, Washington DC 20037
APStracts 3:0136H, 1996.
We present the development of a comprehensive model that was
undertaken to determine the relationships between the components of
an image and the light intensity values present in the image of the
microvessels of translucent tissues such as the bulbar conjunctiva.
Experiments were conducted during the modeling process using a
cylindrical microvessel embedded in a diffuse medium (phantom) on a
reflecting background to affirm model components and simulations. The
3-D model was reduced to a single illumination plane with four
regions of interest, and modelled as Lambertian radiators and
surfaces. The modeling showed that the top of the cylinder and its
immediate vicinity are diffuse reflectors of light from the source
plus light reflected from the background. The limbus of the cylinder
is a diffuse reflector of the source and background illumination, and
a specular reflector of background reflections which achieve a high
grazing angle with the cylinder. The immediate vicinity of the
cylinder receives direct illumination from the source, but the light
is partially obscured by the cylinder. The region beyond the shadow
of the cylinder is a diffuse reflector of the overhead light. The
diffuse medium additionally reflects the source, and also attenuates
the illumination reaching the other components of the scene.
Received 29 April 1994; accepted in final form 13 February 1996.
APS Manuscript Number H377-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 16 April 96