1. A method to detect information representing a three-dimensional structure of an inner surface of a body cavity of a patient, comprising: introducing an endoscopy capsule into a body cavity of a patient, said body cavity having an inner surface; with a light source in said introduced endoscopy capsule, illuminating a first portion of said inner surface of said body cavity; with a camera in the endoscopy capsule, acquiring an image of a second portion of said inner surface of said body cavity that differs from said first portion and is illuminated by said first portion, said second portion having a three-dimensional structure that is known; and supplying said image from said endoscopy capsule to a processor and, in said processor, automatically deriving information representing a three-dimensional structure of said first portion of said inner surface from intensity values in said image.