| 摘要 |
PURPOSE:To detect the phase difference between a reference light and a light to be detected with a high accuracy by dividing a light comprising the reference light and the light to be detected into a plurality of optical paths and, after providing a phase difference with a value different from one another to every optical path, causing an interference. CONSTITUTION:A light beam from a light source 1 is transmitted through a polarizer 3 to become a linear polarized light. An S component linear polarized light in said linear polarized light is reflected by a polarized light divider 4 to develop into a reference light and, after reflected by a plane mirror 10, passes again the divider 4. On the other hand, a P component linear polarized light passes the divider 4 to develop into a light to be detected and, after converged by a condenser lens 6, is reflected by a concave mirror 8 to retrograde, being reflected by the divider 4 to proceed to an unpolarized light divider 11. Polarized light components with the same direction of oscillation are extracted from the reference light and the light to be detected which have passed the divider 11 to be made to interfere with each other and led to light receiving means 19. The reference light and the light to be detected that are reflected by the divider 11 are provided by a phaser 12 with phase differences of values different from that of an optical path that has passed the divider 11. Then, polarized light components with the same direction of oscillation are extracted by another polarizer 14 to be made interfere with each other and led to light receiving means 21. The outputs from the positions corresponding to the means 19 and 21 are calculated by calculating means 24.
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