Considerations and Examples for Determining Precision of Indirect Optical Monitoring

Optical monitoring is the control method of choice for precision optic manufacturers. Advances in control systems over the last decade have made available powerful and convenient components for ease in manufacturing of optical thin films. Never the less, the level of precision obtainable using these systems is dependent upon other process choices made by the system manufacturer and the thin film engineer. In this paper we discuss these process choices and how they affect precision. Then, using a fully automated optical monitor system, we make a series of coatings where the process control parameters are varied to show the variation in the precision obtainable. Precision in this case will be determined by the computer stored monitor data, data observed by the technician during the deposition and the spectrally measured placement of the measured result.