Progress on development of prototype laser reference system for stylus profilometry of large optics

In this progress report, the authors discuss the use of a laser beam, propagating freely in air, as a reference line for profilometry with a large travel length. The reference beam is detected by a position-sensitive detector and any variation is compensated physically by a two-axis flexure system in closed loop operation. Air turbulence is the main obstacle for the stability of the reference system. It is shown that the relative positions of the position-sensitive detector and the height measurement system is critical for correcting the rotational error of the carriage