| 摘要 |
PROBLEM TO BE SOLVED: To reduce the reflection loss and improve the signal to nose ratio by focusing a measuring light near on a movable plate mirror set at specified inclination angle to reflect toward an object to be measured and forming an image of the measuring light focus on the object, thereby simplify the adjustment and avoiding the parasitic reflection. SOLUTION: A measuring light 36 is focused on a focus 40 near on a movable plate mirror 41 through a lens 36, the movable plate mirror 41 is set at an inclination angleαand its virtual image moves when the focus is in front of the mirror surface, the measuring light 36' outgoing from the dynamic focus is approximately collimated by a lens 44 and guided toward a body by revolution type deflection mirrors 45, 46 having rotary axes 45', 46', a lens 47 focuses the measuring light 36' on a focus 40" projected on the body 49 to be measured, a reflected light flue 51 returning back from the dynamic focus 50 arrives at a light detector 53 to interfere with a reference light beam 37 and this interference is enabled by moving a roof type prism 38 and/or mirror 35.
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