Focusing device for e.g. autocollimator selects distance between first and second optical elements such that in response to first and second refractive power, real or virtual image is formed at any point along optical axis

摘要

The device has a first optical element (110) with a first variable refractive power. A second optical element (120) is provided with a second variable refractive power. The first and second optical elements have a common optical axis (Z). The distance between the first and second optical elements is selected such that in response to the first and second refractive power, real or virtual image (B) is formed at any point along the optical axis. Independent claims are included for the following: (1) autocollimator; and (2) method for measuring optical surface of specimen.