Jenny Atwood is a project manager and optical designer with varied experience ranging from astronomical instrumentation to semi-conductor equipment to high-powered laser systems. She presently works as an optical engineer for the National Research Council National - Herzberg Astronomy and Astrophysics, in Victoria BC. Her skills are focused on designing and building optical systems used on large ground-based telescopes around the world.
This will count as one of your downloads.
You will have access to both the presentation and article (if available).
This paper details the design, prototyping and testing of several types of low-cost semi-kinematic optical mounts at NRCHerzberg from a practical standpoint. Optical mounts tested cover a range of types intended to be easy to manufacture, quick to assemble and suitable for various instrument environments. Assembly repeatability in tip/tilt/focus, assembly time, and wavefront error due to stress birefringence (simulated) are quantified and results presented. Thermal stability, suitability for use in cryogenic environments and ease of manufacture/assembly are also analyzed. Various qualitative metrics are also discussed. Quantitative and qualitative metrics are discussed and presented in a design table to aid in directly comparing lens mounting concepts. Results are also interpreted to determine the direction of future R&D efforts towards creating large-scale, multiplexed instruments.
The adjusters must achieve a resolution of 10 μrad and a range of 1 mrad to satisfy the NFIRAOS requirements for laser guide star stability on the wavefront sensors. The adjuster design has many unknowns so a prototype of these adjusters was developed and tested to determine the best design and material selection for use in NLGS. It was found that, although the resolution is unpredictable, the designed adjuster can meet the NFIRAOS requirements with feedback from the optical alignment system. It was also found that material selection and grease are very important to prevent seizing of the adjusters. The results from testing will be used to improve upon the current NLGS adjuster design.
Overview of the final design of the imaging system for the Gemini Infrared Multi-Object Spectrograph
Adaptive optics (AO) systems deliver high-resolution images that may be ideal for precisely measuring positions of stars (i.e., astrometry) if the system has stable and well-calibrated geometric optical distortions. A calibration unit equipped with a back-illuminated pinhole mask can be utilized to measure instrumental optical distortions. AO systems on the largest ground-based telescopes, such as the W. M. Keck Observatory and the Thirty Meter Telescope (TMT), require pinhole positions known to be ∼20 nm to achieve an astrometric precision of 0.001 of a resolution element. In pursuit of that goal, we characterize a photolithographic pinhole mask and explore the systematic errors that result from different experimental setups. We characterized the nonlinear geometric distortion of a simple imaging system using the mask, and we measured 857-nm root mean square of optical distortion with a final residual of 39 nm (equivalent to 20 μ for TMT). We use a sixth-order bivariate Legendre polynomial to model the optical distortion and allow the reference positions of the individual pinholes to vary. The nonlinear deviations in the pinhole pattern with respect to the manufacturing design of a square pattern are 47.2 nm ± 4.5 nm (random) ± 10.8 nm (systematic) over an area of 1788 mm2. These deviations reflect the additional error induced when assuming that the pinhole mask is manufactured perfectly square. We also find that ordered mask distortions are significantly more difficult to characterize than random mask distortions as the ordered distortions can alias into optical camera distortion. Future design simulations for astrometric calibration units should include ordered mask distortions. We conclude that photolithographic pinhole masks are >10 times better than the pinhole masks deployed in first-generation AO systems and are sufficient to meet the distortion calibration requirements for the upcoming 30-m-class telescopes.
View contact details
No SPIE Account? Create one
