Phase difference measuring device with visible light source for

Abstract

A phase difference measuring device includes a first light source, an optical branching device, an optical path length adjusting device, a combining device, a measuring unit, and a second light source. Ultraviolet light emitted by the first light source is branched into a first portion of luminous flux that passes along a sample optical path in which the object to be measured is provided and a second portion of luminous flux that passes along a reference optical path. The optical path length adjusting device is provided in the reference optical path and adjusts the difference in optical path length between the sample optical path and reference optical path. The first portion of luminous flux that has passed along the sample optical path and the second portion of luminous flux that has passed along the reference optical path are recombined by the combining device. The measuring unit then calculates the phase difference of the two portions of luminous fluxes caused by the object to be measured based on the spacing and light intensity of the interference fringes produced by the luminous flux combined by the combining device. The second light source irradiates visible light for illumination, and this visible light is directed to the measuring unit such that its optical axis coincides with the optical axis of the combined ultraviolet light.