Fiber deflection probing method based on micro focal-length collimation.

In order to improve the low displacement sensitivity in sensing the 2D deflection of a fiber probe used for measurement of micro cavities with high aspect ratio, a fiber stem with a ball mounted on its end is used as a probe and a small segment of it is used as a cylindrical lens to collimate a point light source and image it to a camera. The deflection of the fiber stem can be inferred from the change in image acquired by the camera with ultrahigh displacement sensitivities of 10,000 and 20,000 in two dimensions using a fiber stem of 44 mum in diameter, and the corresponding resolutions are better than 1 nm and 3 nm respectively.