Touch-trigger measurement of micro-cavity by optical fiber coupling

In order to measure the geometric dimension of a micro-cavity, a touch-trigger measurement method is proposed, in which the light coming from the incident optical fiber is transmitted in the reversal direction via the optical fiber coupling into the effluent optical fiber, the lateral displacement of the touch-trigger sensor is transformed into the deflexion of light coming out from the effluent optical fiber, and the deflexion is transformed into an image signal by the object lens and CCD capturing system. The effectiveness of the proposed method is verified by experiments. Experimental results indicate that the proposed method can be used to measure the geometric dimension of a micro-cavity. A blind hole of 1.5 mm deep and about 0.2 mm in diameter is measured with the touch-trigger sensor and self-developed micro-hole diameter measuring machine with a repeatability uncertainty of less than 0.2 μm.