A Practical System for Measuring Film Thickness by Means of Laser Interference with Laminar-Like Laser

Abstract

A practical system for measuring a film thickness based on laser interferometry has been constructed using a laminar-like laser and a CCD camera. The system can measure a film thickness at a measuring frequency of 50 Hz, which enables real-time measurement in practical use. The measurable minimum thickness by means of a blue laser having a wavelength of 405 nm was 2.4 µm, and the maximum thickness was 1.2 mm for a film with a refractive index of 1.4. The measurement error of the film thickness due to the spherical aberration of the cylindrical lens was ∆h/h = 2% at maximum, where h expresses film thickness and ∆h its error amount.

Interaction Between Line Soliton andY-Periodic Soliton: Solutions to the Asymmetric Nizhnik–Novikov–Veselov Equation

“…The value of K depends only on the optics of the sensor head as is shown in equation (6). In contrast, ε depends on both the optical sensor and data processing [12]. That is, the error can be further reduced by means of data smoothing; it is linearly proportional to 1/ √ n, where n is the number of times the data is smoothed [13].…”