Abstract: The keratometer comprises an illumination system made as the following components located before a cornea: a light source, an objective lens, ring-shaped measuring marks interposed between the light source and the objective lens on the focal surface of the illumination system symmetrically with respect to the optic axis of the objective lens, and a cone-shaped mirror.The cone-shaped mirror is interposed between the objective lens of the illumination system and the cornea and is shaped as a cone frustum having its inner surface provided with a reflecting coating. The keratometer comprises also a unit for recording the images of the measuring marks and a projection lens, the latter being composed of two elements one of which is in fact the objective lens of the illumination system and the other element is located on the optic axis of the illumination system objective lens between the latter and the unit for recording the images of the measuring marks.

Abstract: An interferometer for checking the shape of convex surfaces of optical components comprises a monochromatic light source and a sequence of devices arranged therebehind in the path of beams including a focusing lens, a light splitter, a compensator, a lens system having as its last surface a reference concave surface having a center of curvature optically matched with the back focus of the focusing lens by means of the compensator. Arranged in the path of beams behind the lens system are an additional compensator, an additional light splitter, an additional focusing lens, a system of mirrors for directing the beams from the monochromatic light source to the additional focusing lens having its back focus matched by means of the additional compensator with the center of curvature of the reference concave surface of the lens system closest to the monochromatic light source, the radius of curvature of this surface being other than that of the reference concave surface.