| 摘要 |
PURPOSE:To precisely carry out wavelength correction corresponding to the alteration of refractive index of the gas in the case that the displacement between two parts which are displaced relatively is detected in the ambient gas using coherent light beams. CONSTITUTION:The part from a pass of a laser beam B2 of an interference refractive index measuring meter to a pass of a laser beam A2 of an inter-ferometer for measurement is covered with a ventilation duct 24. The ambient gas ventilated by a temperature controlling apparatus and a ventilating fan is led to the direction of a cornor cube 2 of a movable stage 5 along the laser beam A2. |
