Laser measurement system for on-line control of a manufacturing process

A nondestructive method of determining the thickness of a coated surface is developed using an He-Ne laser and a charge-coupled device (CCD) sensor. The CCD has a linear array of image sensor elements (photosites) separated by a silicon dioxide surface. When light rays fall on the sensor, image photons pass through the transparent silicon, creating hole-electron pairs. The photon-generated electrons acculate in the photosites which will build the charge as a linear function of incident illumination intensity and integration period. The laser-CCD system is proposed for quality control and to maintain the desired thickness of coating by integrating the measurement system with an adaptive controller. Simulation is performed to study the effectiveness of an adaptive control algorithm using an autoregressive (AR) model for online implementation.<>