Light source for low-coherence interferometry surface diagnostics

Abstract

We describe in this paper a pilot experiment of optimization of a white-light source for a low-coherence interferometry. The white-light source combines the light beams generated with colour LEDs. By modelling of the white light spectra, a contrast of a white light interference fringe could be changed and set to the maximal value.The second part of this paper is a description of a white-light fringe analysis ensured with a low-cost colour CCD camera. The used detection technique employs a phase-crossing algorithm which identifies a zero optical path difference as the point where the phase difference between the red, green and blue part of the white-light interference fringe becomes equal to zero.The optimized white light source is designed to be a crucial part of an experimental setup for the surface diagnostics and automatic calibration of gauge blocks.

Detection of Interference Phase by Digital Computation of Quadrature Signals in Homodyne Laser Interferometry

“…As a consequence, the method also scales well, e.g., when several measurement axes would be required within a measurement system. In such a case, the added complexity per each added axis is minimal in comparison to the traditional means—it has been already demonstrated in a practical application for surface diagnostics [22] and multi-axis geometric measurements [23]. An extra axis requires only a small amount of additional optical components and poses no substantial additional requirement on the laser source (assuming there is enough power available, but it is usually not an issue, e.g., for green Nd:YAG lasers).…”