Using a lens as an example, this paper analyzes the problem of accurately positioning an object at the focus of the optical system of a heterodyne differential-phase interferometer with scanning of the beams over the field. A theoretical expression is obtained for a differential-phase portrait of the lens. A method is proposed for eliminating the error associated with inaccurate positioning of the test object in the focal plane of the objective by making several measurements of the phase while the heterodyne photodetector undergoes controlled displacement in the transverse direction. Experimental checking is done, which showed that the theoretical calculations agreed with the results of a measurement of the focal power of the lenses.
© 2008 Optical Society of AmericaPDF Article