Advanced lithography techniques, combined with a Class 1000 clean-room manufacturing facility, are being employed to create highly-accurate and highly repeatable optical encoder parts for the most demanding custom requirements, by Dorset, UK specialist, Tecan.

Moving forward from traditional emulsion-on-film lithography, the company is now using chrome-on-glass photo masters to produce new levels of accuracy for the optical apertures in encoder discs and similar components. The technique, coupled with a high-accuracy photo tool alignment system, within strictly controlled clean areas, produces exceptionally crisp edges, typically achieving optical aperture tolerances of ±1.6 micron. The parts are subsequently Photo ElectroFormed (PEF), creating encoder products with superior optical and mechanical performance characteristics.

It is sometimes a requirement to produce parts with selectively thicker areas, to meet specific mechanical performance needs, again this presents no problems for the company. Initially, the disc is manufactured using PEF to a thickness of 20 micron, producing optical slots of the finest possible resolution. A second PEF stage is then carried out which leaves the high-accuracy slots as they are and selectively increases the thickness of the disc in other areas. The result is a single rigid part, with localised thickness variations across its surface to suit both optical and mechanical requirements.

PEF discs are typically thinner, lighter and more robust than discs manufactured by other means. They feature slots with extremely smooth, yet optically sharp edges that facilitate a well-defined light pulse. Typical PEF tolerances are ±4 microns, and in some cases, ultra-high tolerances of ±2 microns or less can be achieved.

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