Optical system for automatic lens meter

An optical system for an automatic lens meter, comprising:

• a light source for generating a measuring light beam;
• a convex collimator lens, disposed at a predetermined focal distance from the light source, for collimating the measuring light beam generated from the light source to move in parallel after passing through the convex collimator lens;
• an expanding concave lens, disposed downstream of a lens to be examined, for expanding the measuring light beam passed through the lens to be examined with respect to an optic axis;
• a plural-apertures stop, disposed downstream of the expanding concave lens and formed with a plurality of apertures along the circumference thereof at predetermined angular intervals, for separating the measuring light beam, having passed through the expanding concave lens into a plurality of measuring light beams;
• a prism lens in which a convex lens and a fixed prism assembly are integrally formed, disposed directly downstream of the plural-apertures stop, having the convex lens to focus the plural measuring light beams passed through the plural-apertures stop, and the same number of prisms as the number of the plural apertures to deflect the focused light beams so as to maintain the light beams in the separated beams;
• and
• an image forming lens disposed downstream of the prism lens, for forming aperture images of the measuring light beams, passed through the prism lens, on a two-dimensional sensor array.