Laser-based machining of fine features scales for high precision optical position encoders

High precision optical motion encoders provide reliable high-accuracy position feedback and contribute to the accuracy of automated precision manufacturing. They can be found in machine tools, assembly systems and robotics as well as in medical applications. Traditionally, the highest resolution scales have been lithographically formed on glass substrates. These are limited in length, fragile and expensive. Rugged scales have traditionally been mechanically embossed into flexible tape, and are limited in resolution. A change of approach to high resolution scale manufacture is required in order to develop technology which is appropriate to highly dynamic or rugged environments where extreme reliability is essential, for example in medical or satellite applications. This involves a reduction of flexible tape scale's features' geometry and size. In this academic-industrial partnership, we are investigating novel techniques for the production, at commercially viable rates, of optical encoder scales with features of the required precision (200 ± 10 nm). In this paper we will present the results of our experimental programme to review and compare the robustness and repeatability of different laser-based methods to generate fine features.