Retro Refractions   /   blog
Brandon Dube,   Optical Designer & Metrology Specialist

I am currently based in Rochester, NY and employed by the Center for Freeform Optics and Optical Diagnostics and Applications Laboratory as a Research Assistant, and serve as the Director of Metrology at Olaf Optical Testing. I specialize in the design, fabrication, and testing of nonrotationally symmetric systems, and MTF measurement at high speed and volume with exacting accuracy through automation. I also enjoy a passion for food, cinema, photography, music, and travel.

Consumer Lens MTF and Variance

An ongoing project at Olaf Optical Testing in partnership with LensRentals to measure and document the real MTF and variance of consumer photographic and cinema lenses. Lenses have their resolution measured in sample sizes of 10 or greater and the results tabulated; statistics are run on the populations and made publicly available on the LensRentals Blog. This style of testing is unique to us, and will be available in the future as a service for manufactures and consumers alike. Here is a log of our past work.

Reflected Wavefront Testing of a Convex Diffraction Grating

An offner-based relay system was used to pass the diffracted-in-reflection beam to a point diffraction interferometer. The observed interferogram was used to quantify both errors of form – low-order Zernikes – and the grating ruling. The fabrication error was determined to be primarily power and astigmatism. Future work will include the fabrication and testing of the mirrors used in the system, as well as final assembly and system-level testing. For additional information, please see this page.

Using a Schmidt Telesope to Verify Nodal Aberration Theory for Freeform Optics

Assembly of complete system and interferometric measurement in order to map aberration field. A plate has been polished via Magnetorhelogical Finishing to a freeform surface and is used to "inject" aberrations into the system. The plate will be scanned through several positions and 81 field points will be sampled for each. More information will be disclosed after the publishing of Kyle Fuerschbach's PhD.

Using a Ritchey-Chrétien Telescope to Verify Nodal Aberration Theory for Misalignment

The Robert S. Hilbert Memorial Telescope is a Ritchey–Chrétien telescope developed to demonstrate NAT applied to tilted and/or decentered geometries. The experiment includes construction of a test setup for the telescope, which has its secondary mirror mounted to a hexapod for controlled decenter and tilt. The wavefront will be measured in many locations of the field of view to validate the predictions of NAT. Later, an artificial starfield will be projected into the telescope and measured, to provide a realtime view of the full-field aberrations before and after decenter and tilt.