Shadow Depth Cues and Endoscopic Task Performance

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Abstract
IN THE 1950s, there were 2 milestone inventions in the evolution of endoscopy: the rod lens system by Hopkins1 and the fiberoptic light-transmitting system,2 permitting efficient internal illumination of body cavities from an external light source by total internal reflection within the glass fiber bundles. These 2 components have since been incorporated into all rigid endoscopes in which the light surrounds the objective lens so that light direction and optical axis subtend the same angle to the target plane. This assembly ensures good illumination of the field of view even when the endoscope is moved. However, this configuration produces a shadowless image.