| 摘要 |
PURPOSE:To carry out high resolution interference fringe measurement, by realizing the interfefence between basic waves and second harmonics, utilizing a feature of a nonlinear crystal. CONSTITUTION:A laser beam 1 passes through a lens 2, is incident upon a nonlinear crystal 3, collimated by a lens 4 after second harmonics are generated, propagated in the air for interferometry, etc., passes through lens 7 and is incident upon a nonlinear crystal 8 after the polarization state of reflected light from a reflecting mirror 5 is adjusted by a wavelength plate 6, etc. The second harmonics travel as they are, but a part of basic waves are converted into second harmonics and interfere with the former second harmonics. The number of this interference fringes becomes about 4X10<-6> of the number of normal interference fringes owing to a single wavelength by second harmonics, because the fringes are generated only for a portion of the difference between basic waves and second harmonics in the dispersion characteristics of air as a medium, the number of interference fringes to be measured becomes extremely few, and the very accurate phase measurement of interference fringes can be carried out.
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