Interferometric gauge block measurement with 633 nm He - Ne and 1,064 nm Nd: YAG lasers

摘要

We have developed a laser interferometer to calibrate gauge blocks utilizing 2 lasers, 633 nm He -Ne and 1,064 nm Nd: YAG. At only 633 nm of. wavelength, several kinds of practical He -Ne lasers have been developed and manufactured, while there is not practical laser light source for interferometer other than at 633 nm. To realize practical light source in addition to 633 nm, we stabilized the wavelength of 1,064 nm Nd:YAG laser, utilizing linear absorption of iodine at 532 nm. The iodine cell was inserted between two non linear crystals for second harmonic generation and first derivative signal was generated by dispersion effect near the absorption line of iodine, without any electric circuit for modulation or for phase sensitive detection. Gauge blocks were measured with the two wavelengths of 633 and 1,064 nm. The fringe pattern was detected by CCD camera and the length was estimated by excess fraction method. It is easy to determine the integer part of the fringe order, since the wavelength difference between these two is large and the wavelength ratio is not expressed by a simple combination on integers. The results agreed with those obtained by conventional method with ↑(198) Hg isotope lamp.