| 摘要 |
PROBLEM TO BE SOLVED: To provide a replacement detection apparatus capable of detecting replacement in the height direction of a member to be measured with high precision and performing stable measurement at high speed.SOLUTION: A replacement detection apparatus 1 includes a light source 2, which irradiates a member to be measured with light, a luminous flux splitting part 3, a transmission type grating 4, a reflection part 6, a returning reflection part 5A, an optical path correction member 7A, a luminous flux coupling part 3, a light reception part 8 and relative position information output means 10. The grating 4 diffracts a first luminous flux L1 reflected by a surface to be measured of a member to be measured 9, and makes the first diffracted luminous flux L1 incident again on the surface to be measure of the member to be measured 9. The returning reflection part 5A makes the first luminous flux L1 diffracted by the grating 4 and reflected on the surface to be measured of the member to be measured 9 be reflected on the surface to be measured of the member to be measured 9 and incident again on the grating 4. The optical path correction member 7A is provided between the member to be measured 9 and the returning reflection part 5A, and corrects an optical path of the first luminous flux L1. |
