| 摘要 |
<p>PURPOSE:To improve measuring accuracy, by obtaining the length to be measured by an interferometer by using the operation, which does not include refractive index of air as a medium of light. CONSTITUTION:A laser light source 1 with a wavelength lambda1 and a laser light source 2 with a wavelength lambda2 are provided. The laser light beams are mixed in a beam mixer 3. The mixed laser light beams are inputted to a beam splitter 5 through a collimator 4 and divided into the reflected light, which goes to a variable light path multiplier 6, and the transmitted light, which goes to a fixed light path multiplier 7. The reflected light through a beam splitter 8 is inputted to a detector 11. The interference fringes are detected and inputted to a phase lock 15 through an amplifier 12, a squaring device 13, and a filter 14. Then the signal is amplified by about 400 times. The phase of the interference fringes is fixed. A scale line signal S is inputted to a gate 16, and the interference signal is counted by a counter 17 through the gate 16. The transmitted light is inputted to a detector 22 through a filter 21 in parallel with the reflected light. The interference fringes are detected and counted by the counter 17 through an amplifier 23, a phase lock 24, and a gate 25.</p> |
