Product Code: ICAL09_1103

Laser-based Machining of Fine Features Scales for High Precision Optical Position Encoders
Authors:
Stephanie Giet, Heriot Watt University; Edinburgh Scotland
Charalampos Michakis, Heriot Watt University; Edinburgh Scotland
Jonathan Parry, Heriot Watt University; Edinburgh Scotland
Matthew Kidd, Renishaw Plc; Edinburgh Scotland
A. Ellin, -; -
Jonathan Shephard, Heriot Watt University; Edinburgh Scotland
Nick Weston, Renishaw Plc; Edinburgh Scotland
Duncan Hand, Heriot Watt University; Edinburgh Scotland
Presented at ICALEO 2009

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 industrial partnership, we are investigating novel techniques for the production, at commercially viable rates (100 metres of scale per day), of optical encoder scales with features of the required precision (200±10nm). 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. Their characteristics will be assessed with an existing encoder read-head to determine the impact of the features topography on the overall scale and encoder performance.