JPS6413426A - Monochromatic light source dual luminous flux interferometer - Google Patents

Abstract

PURPOSE:To reduce an interference signal which returns to a laser resonator from an interferometer and to reduce the influence of harmonics by providing a lens between the laser resonator and a beam splitter. CONSTITUTION:The convex lens 30 is provided between the resonator of a laser 2 and the beam splitter 4. Incident light 32 from the laser 2 is increased in spread angle under the influence of the lens 30 as shown by a symbol 34 to generate luminous flux which is incident slantingly, and when its angle is denoted as delta, an interference signal is generated according to the sliding speed of a moving mirror 6, thereby causing a wavelength shift. The value is determined unconditionally by the distance between the lens 30 and laser 2, the area of a detector 10, and the distance from the lens 30 to the detector 10, so the value is obtained merely by multiplying the real laser wavelength by a coefficient and never affects the result of data collection. Apparent variation in the laser wavelength can be corrected by a CPU, so the quantity of the laser interference light of the splitter 4 which returns to the laser resonator is, for example, 1/200 time as large as when the lens is not provided.