Optical projection tomography

Apparatus for obtaining an image of a specimen by optical projection tomography, the apparatus comprising light scanning means, a rotary stage for rotating the specimen to be imaged, an optical system and a localized light detector, wherein light from the scanning means scans the specimen and the optical system is constituted by a convex lens which causes convergence of light incident thereon and is operative to direct onto only the localized light detector throughout the scanning movement of the light that light which exists or by-passes the specimen parallel to a beam incident on the specimen, thereby to allow a higher signal-to-noise ratio by limiting detection of scattered light at the localized light detector.