| 摘要 |
PURPOSE: To measure the wavelength accurately over the entire wavelength region by extending the memory section in an operating section so that the count of a length measuring unit is recorded for every interference fringe of measurement and a numerical calculation is made. CONSTITUTION: A beam splitter 1 branches a light 20 to be measured having wavelength ofλin two which are then reflected, respectively, on a fixed mirror 2 and a moving mirror 3 toward the splitter 1. The interference light is subjected to photoelectric transduction at a light receiving section 4 which generates a pulse signal for every interference fringe interval 1/2 as the moving mirror 3 moves. A length measuring unit 5 measures a moving amount 3 and generates a pulse signal 22 at an interval of measurement resolution (d). An operating section 6 counts the count M of the signal 21 and the count N(M) of the signal 22. Sinceλ/2=d(N(M)+εM) is satisfied assuming the fraction isεM, the wavelengthλis determined according to a formulaλM=2dN (M)/M using the counts M and N(M). The operating section 6 comprises a memory section 6A and the wavelength of light close to true value is selected from the count N(M) through a numeric calculation.
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