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.

We present a new interferometer system devised for surface-profile metrology with multiple two-point-diffraction sources that are made from a pair of single-mode optical fibers. The diffraction interferometer system performs an absolute profile measurement by projecting multiple fringe patterns on the object surface and then fitting the measured phase data into a global model of multilateration. Test measurement results demonstrate that the proposed profiling method is suited for rough surfaces with excessive surface irregularities, which are difficult to measure with conventional two-arm interferometers.