1957 年 4 巻 2 号 p. 35-39
A 5m, scaFle is standardized based on light wave standard by the interference compa rator, a slight modification of the one described in a previous report . The optical standards used are 5 cm. and 50 cm. Fabry-Perot etalons made of iron pipe and a 5 m, etalon constructed on a concrete block. The 5 cm. etalon is determined in terms of the wave length of the cadmium red line. The 5 m. etalon is determined by the successive comparisons of the shorter etalons using normal incident ray by spectroscopic method . To eliminate the effect of the change in the length of the etalons and the systematic error due to timed measurements of respective etalons, the 5m, etalon is determined symmetrically before and after its comparison with the 5m, scale, by either departing from the measurement of the 5 cm, etalon or from the comparison of the 5 m. etalon with the 50cm, etalon. The mean of the two values obtained from the go and back measurements is adopted as the length of the 5 m. etalon when it is compared with the 5 m, scale. The systematic error due to the timed measurements is clearly recognized according to the order of measurements, especially in the 5 m . etalon (Table I). When this error is elimi nated, however, the 5 m, etalon is found to change its length much less than the other etalons do (Table II) and the amount is estimated more or less lμ during the comparison with the 5 m, scale. From 11 sets of measurements, the scale is determined with the standard deviation of ±1.05μ and the mean error of±0.32μ (Table IV).