PURPOSE: To decide whether the polarity is positive or negative even when the range of a phase difference is expanded greatly by obtaining an envelope signal on which an interference signal of interference light consisting of plural known wavelength components is superposed.
CONSTITUTION: The intensity of output interference light when coherent light beams which have wavelength λ and are mutually out of phase is expressed as 2(1+cosi). When this interference light output is superposed as to i=1, 2 and spectrum component of λ1 and λ2 are detected at the same time, the sum IT is as shown by an equation 1 and the difference is as shown by an equation 2; when 1 and 2 vary uniformly, the IT and ID draw what is called 'beat waveform'. Then, envelope outputs IHC and IHS of the equations 1 and 2 are as shown by an expression 3. A two-wavelength system using the equation 1 is judged within a range 0≤B≤π on condition that envelope informa tion is obtained at the same time. Namely, the direction of variation is judged from B, so the direction of variation is judged over a wide range without reference to the values 1 and 2 when 1-2 is set small.
ISHIHARA SATOSHI
TAGAWA MASAFUMI
YAMAZAKI HIROSHI
SUMITA OPTICAL GLASS
YAMATAKE HONEYWELL CO LTD
| JPS58169004A | 1983-10-05 | |||
| JPS60306A | 1985-01-05 |