Simple autocollimation laser refractometer with highly sensitive, fiber-optic output

Refractive index measurement by fiber point diffraction longitudinal shearing interferometry

A refractive index measurement method by measuring the longitudinal displacement of a point light source (PLS) after passing through a plane-parallel-plate sample is proposed. The displacement is derived by applying two point-diffraction longitudinal shearing interferometric measurements if the distance from the PLS to the exit pupil is predetermined. With two fibers to simulate the ideal PLS, an experimental system for solid and liquid sample tests is proposed to verify the principle. The experimental results indicate that its accuracy is in the order of 10(-4). Ways to improve the accuracy are discussed based on the detailed error analysis.

Simple wide-range method for angle measurement with a point fiber-optic output

We propose a simple optical method for precise, wide-range angle measurement based on the use of a single-mode optical fiber as a registration scheme output. Because of its micrometric core dimensions, the fiber serves as a point receiver that is highly sensitive to angular displacements of focused laser emission. The method allows the independent photoelectric measurement of both rotation and spatial angles of various optical elements, combining a wide angular dynamic range (from 0 degrees to 360 degrees ) with high accuracy (exceeding 3 arcsec).