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Photometric stereo imaging is an established computer vision technique that acquires a series of images illuminating the same sample from each of a number of different light sources sequentially. This series is used to synthesize a map of the spatial orientation of the object surface for each pixel in an image. Usually, photometric stereo imaging is limited by proximity of light sources and cannot be used in confined spaces. This invention relies on the same principle as photometric stereo imaging, but, importantly, can measure topographic information within a compact system for application in endoscopy.

Photometric stereo endoscopy utilizes one camera to acquire a series of tissue images utilizing multiple light sources, which are already incorporated into most commercial endoscopes. In contrast to traditional endoscopy analysis, a processor is used to analyze each surface image obtained under various illumination directions to determine tissue topography and construct a three-dimensional surface image. This image can be evaluated by endoscopists, and topographic information can be used as input for a computer-aided detection algorithm to improve detection of colorectal cancer lesions.