Introduction
This paper describes the application of a small digital computer
to automatically control the manufacture of multilayer thinfilm
optical-interference filters. These devices are an important feature
of many modern optical systems.1'4 Antireflectance coatings and cold
mirrors are two important examples. The development of control
systems to regulate various aspects of the manufacturing process has
been a subject of extensive study. Systems have ranged from simple
analogue feedback units2 to highly complex sequence and feedback
controllers that completely automate the process for particular
applications.3 Processes with the simple control systems require a
very skilled operator to achieve an acceptable product. Despite this,
the rejection rate because of inferior quality is usually high. The more
sophisticated controllers are restricted in application because of
limitations in the hardware. In addition, their complexity still requires
skilled operation. It is considered to be worthwhile, because of these
shortcomings, to investigate the feasibility of using a small digital
computer to supervise the manufacturing cycles.