- Front Matter: Volume 8708
- Advance in the Mid-Wavelength Infrared Window Technology I
- Advance in the Mid-Wavelength Infrared Window Technology II
- Advance in the Mid-Wavelength Infrared Window Technology III
- Advances in Long-Wavelength Infrared Window and Dome Processing Technology
- Optical Surface Treatments, Coatings, and Microstructures
- Novel Applications and Characterization Tools for Optical Windows and Domes
- Metrology and Finishing of Flat, Free-Form, and Conformal Optics
Temperature non-uniformity in a heated window can result in a significant distortion in the transmitted wavefront. Aberrations are introduced by actual physical distortion of the window due to differential thermal expansion and by localized optical path variations due to the change in index with temperature (dn/dT) of the substrate material. Typically, the second factor is the more pronounced. This effect represents a significant limitation in the performance of windows with non-symmetric geometries made from materials that exhibit combinations of high dn/dT and low thermal conductivity.
LightWorks Optical Systems (LWOS) has recently developed a software tool capable of quantitatively modeling the thermal distribution of a heated window in operation. This capability allows the design team to optimize the heater layer sheet resistance (whether the layer is a metallic grid or a transparent conducting oxide thin film) and the configuration of the bus-bar (electrode) connections prior to any hardware fabrication. Consideration of both of these factors is critical to achieving a uniform thermal distribution at the specified temperature across a given window.
This presentation will describe the recent efforts of LWOS to establish the capability for quantitatively modeling the temperature homogeneity across a heated window based on window material and dimensions, heater layer characteristics and bus-bar configuration. Data will be presented that demonstrates the validity of these models via comparison to actual heated windows observed under heated conditions.
Future optical systems are moving away from traditional spherical optics. The anticipated benefits are numerous for freeform optics as they provide better aerodynamic characteristics for aircraft, lighter weight for space missions, and smaller size for medical procedures.
Currently the design and utilization of conformal and freeform shapes are costly due to the difficulties introduced with fabrication and metrology of these parts. Techniques for creating these complex optical surfaces are still in development for traditional optical materials. OptiPro has a unique opportunity create manufacturing solutions through computer controlled multi-axis optical generating, polishing, and metrology machines. OptiPro Systems is continuing to develop advanced optical manufacturing technologies. OptiPro has made toric and freeform arch shapes. OptiPro’s existing manufacturing platforms include its eSX grinding, UltraForm Finishing, and UltraSurf non-contact surface scanning system, which will be used for grinding, polishing, and measuring conformal and freeform shapes.
Freeform surfaces are initially generated using deterministic micro-grinding with diamond bonded tools. Tool paths with up to five axes of simultaneous motion are required to generate and polish the optical figure of conformal surfaces. Sub-aperture corrective polishing will need to vary the amount of time the tool contacts at each location in order to remove the proper amount of material. These locations and dwell times are derived from a surface figure error map provided by OptiPro’s UltraSurf. Research and development of the freeform manufacturing process will be presented.