Increased master mould cutting accuracy for more efficient
optical structures
In collaboration with David Robertson of Durham University, Microsharp are developing master moulds to produce highly accurate optical films .
One outcome of this collaboration is the InADiT process, a patented
method of manufacturing the master moulds from which optical
structures are replicated onto thin films. | |
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The Issue |
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Many thin film structures such as Fresnel Lenses require the production of
structures in which the pitch and depth of the facets must vary across the surface
of the structure. The traditional mould manufacturing method, “Single
Point Diamond Turning” uses just one cutting tool to produce a constant
structure across the mould surface. If a variable structure is required “Diamond
Contouring” must be used which involves raising and lowering the single point to
achieve facets of variable depth.This method cannot produce facets with
sharp apexes and valleys, producing “rounding” at the extremities. The
lack of definition at the peaks and troughs causes a loss of optical efficiency in
these areas. Because a single lens may use many hundreds or thousands of
facets, these individual tiny flaws when added up lead to a significant loss in
lens efficiency. | 
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The Solution |
With the Included Angle
Diamond Turning (InADiT) process, a tool with the apex angle of the
smallest facet required in the structure is chosen. The larger facets are then
produced by moving the tool within the prism. This method produces facets
with very sharp peaks and troughs with no rounding at the extremities. |
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Co-ordinated Axis Motion Single Point Turning |
The extremely precise movement of the cutting tool required to
perform the InADit process is achieved via Co-ordinated Axis Motion.
The cutting tools’ movements can be controlled very accurately in 4 different
axes. |  |
