Lateral-shearing interferometer using square prisms for optical testing of aspheric lenses

Abstract

We present a lateral-shearing interferometer specially devised for production-line inspection of aspheric lenses. The interferometer constitutes four right-angle prisms, whose relative sliding motions provide the lateral shearing and phase shifts necessary for measuring the beam wavefront collimated by the lens under test. The prisms are held together face to face using index-matching oil, so environmental disturbances from external vibration and atmospheric turbulence can be minimized. Furthermore, a special phase-measuring algorithm of least-squares type is adopted to compensate for the phase shift error caused by the variation in thickness of the index-matching oil holding the prisms. Experimental results prove that the interferometer provides a measuring reproducibility of the order of one hundredth of the light's wavelength.

Anti-Vibration Characteristics of a Lateral Shear Interferometer for On-Machine Surface Measurement

“…Different from the conventional interferometric methods, a lateral shear interferometer has good anti-vibration ability due to self-reference characteristics [2]. Various designs [3][4][5][6][7][8] of lateral shear interferometer have been reported for experimental researches. However they are inconvenient for shear adjustments and phase shifting, have complicate mechanisms, in-complete common-path, and therefore less stability for practical applications.…”

Measurement of Freeform Optical Surfaces: Trade‐Off between Accuracy and Dynamic Range

“…For example, linear fringes indicate defocus while the wavefront with spherical aberration (SA) yields nonconcentric fringes appearing like coma in ordinary wavefront interferometry. Typical lateral shearing generators include wedge prisms, [ 76 ] parallel plates, slightly wedge‐shaped plates, [ 77,78 ] square prisms, [ 79 ] double gratings, [ 80 ] spatial light modulators (SLMs), [ 81,82 ] etc.…”

Detection of phase singularity using a lateral shear interferometer

“…Fringes in a shear interferometer depict the gradients of the test wave front in the direction of shear, when shear is small. Lateral shear can be introduced by a shear plate [2], gratings [3], prisms [4] and Michelson interferometer [5]. Shear interferometers are used for testing of optical components [6], wave front aberration testing [7], collimation testing [8,9], light spot array generation [10] and vortex array generation [11].…”