| 摘要 |
PROBLEM TO BE SOLVED: To provide an interval measuring instrument and a surface shape measuring instrument, of small size and excellent versatility, capable of measuring the interval between optical elements, their thicknesses, or their surface shapes, with high accuracy. SOLUTION: A light beam from a light source 11 is reflected by first and second reflection surfaces 15a and 16a. The light coming into a division beam splitter 17 is divided into measurement light M and reference light R with their phases inverted relative to each other. The light M and the light R are caused to interfere with each other by a composite beam splitter 22. A corner cube 22 is moved by a moving stage 20 to change the optical path length of the light M, thereby changing the contrast of interference light. The distance between the surfaces 15a and 16a is found from the contrast of the interference light and the position of the stage 20. This enables the distance between the surfaces 15a and 16a to be found without upsizing the whole of the instrument even if the distance is large from a polarization beam splitter 13 to the surfaces 15a and 16a.
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