| 摘要 |
PURPOSE:To secure a long operation distance and to measure the position of a sample by converging and projecting a couple of positive and negative diffracted light beams on the sample, making their reflected diffracted light beams interfere with each other, and observing interference fringes (or not making them interfere). CONSTITUTION:Light beams diffracted by a diffraction grating 6, e.g. (+ or -1)th order diffracted light beams pass through a lens 7 and is reflected by mirrors 8B and 8A and projected on the sample T by being converged so as to cross itself on the focus O0 of the lens 7. When the sample T is positioned closely to a light source by deltaz from the point O0, the couple of diffracted light beams are reflected by the sample T to cross each other at a point P0 close to the light source by 2deltaz from the point O0. Their reflected light beams pass through the mirrors 8A and 8B lens 7, and grating 6 and deviate in traveling direction by 2deltaphi to form interference fringes. The angle of diffraction f this light varies with the position of the sample T. Consequently, the displacement quantity deltaz is measured by measuring the number of the interference fringes in a specific range or intervals of light or dark parts, or moving an optical system so that no interference fringes are formed.
|
