Fabrication of Freeform Optics

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Fabrication of Freeform Optics

• Brian Creber, P Eng
• B-Con Engineering inc
• www.bconeng.com

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Fabrication of Freeform Optics

• About B-Con Engineering
• Typical Applications
• Design and Software Interface
• Materials and Methods
• Metrology
• Future Challenges

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B-Con Engineering inc

• Located in Ottawa, Canada
• Established in 1988
• Holder of 11 international patents
• Remote access process metrology and control
• Bio photonics
• Direct diamond turning of gold and gold alloys
• Optic and system design
• Optic fabrication, diamond turning, Freeform

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Typical Freeform Applications

• Conformal Windows
• Airborne Vehicle sensor windows
• Wind tunnel metrology optics
• Large Projection Displays
• BMW Heads Up Display
• Back projection television
• Illumination applications of White LEDs
• Lens arrays
• Ruled Surfaces

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Automotive HUD
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Projection Lenses
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Illumination Applications
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Design and Software Interface

• Moore 500 Freeform Generator
• Standard G-code CNC machine programming
• Man machine interface for rotational optic fab
• No standard MMI for Freeform
• Optic design software for creating surfaces
• Zemax, Code V, Oslo, others
• Defines a surface in space, and relative
  co-ordinate system

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Design and Software Interface

• Machine needs a tool path in the machine
  co-ordinate system
• Moore 500FG is a cylindrical system.
• Freeform tool path software developed by B-Con
  Engineering
• Handles translation and rotation of the design
  software co-ordinate system, unlimited terms
• Material shrinkage for molding tool fabrication
• Grinding/Flycutting tool geometry
• Surface position resolution lt 100 nm

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Design and Software Interface

• Moore 500FG on board metrology (WECS)
• Designed for rotationally symmetric parts
• Contact metrology for Freeform parts
• Needs probe path software generated by B-Con
• Measures relative to theoretical tool path
• Single Path only, surfaces may be stitched from
  multiple path measurements.
• Resolution 100 nm
• Part can not be dismounted from the machine.

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Materials and Tools

• Raster Flycutting
• Plastics, Acrylic, Polycarbonate, Zeonex
• Aluminum, Copper, Electro less Nickel
• AlBeMet (Aluminum Beryllium alloy), BeCu
• Precision Grinding
• Tool Steel (Rc gt54)
• Optical Glass
• Fused Silica
• Silicon Carbide

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Materials and Tools

• Raster flycutting tools
• Single point diamonds
• Standard and custom shapes
• Precision Grinding tools
• Diamond wheels
• CBN wheels
• Custom diamond and CBN tools

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Future Challenges

• Volume production requires molding tools
• Freeform shape molding requires easy to use
  metrology of the molded components
• Freeform nulls and CGHs for conventional
  Interferometer
• New interferometric or other metrology methods
  for steep freeforms.
• Freeform molding tools require new materials
• Grinding precision freeform surfaces are time
  consuming and costly

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Tele613-727-0021 Fax [phone] www.bconeng.co
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