Measuring Up: From Aspheres to Education

MICHAEL D. WHEELER, MANAGING EDITOR, michael.wheeler@photonics.com

The first lenses shown to have aspheric surfaces were discovered in several Viking graves on the island of Gotland in Sweden. Known as the Visby lenses, the rock crystal lenses date to the 11th or 12th century, according to “The Eye in History” by Frank Joseph Goes. It’s not entirely clear what the origin or purpose of these lenses were. What is clear, a thousand years later, is the special role aspheres play in a growing number of systems. With their unique ability to reduce spherical aberrations and focus light, a single asphere can often replace a much more complex multi-lens system. That’s a boon to manufacturers where smaller and lighter often mean better.

As with all optics, aspheres must conform to certain standards of performance — and for that, engineers turn to metrology. As we learn in this month’s cover story by Edmund Optics’ Amy Frantz, manufacturers must look beyond conventional interferometry, and weigh inspection constraints and the nature of the part before choosing a method. See “The Long and the Short of It: Techniques for Measuring Aspheres” (read article).

We shift our focus to two features that explore innovations in Raman spectroscopy, a technique prized for analyzing chemical structures without damaging the sample. In “Innovation in Surface Tracking Opens Doors to Raman Imaging Applications,” (read article), Renishaw’s Tim Batten examines improvements in focusing technology that have eliminated some of the limitations posed by rapid Raman imaging. On the subject of improvement, in cases where rugged and low-cost Raman systems are called for, linear variable filters pose an attractive alternative to gratings. See “For Compactness and Ruggedness, Linear Variable Filters Fit the Bill,” (read article).

Economic realities played a role in the discontinuation of commercial display technologies based on MEMS interferometric modulators and shutters. What is new, as we learn in contributing editor Hank Hogan’s “For MEMS Displays, Projections of Success,” (read article), is the growing role of digital micromirror devices (DMDs) in today’s projectors used in MEMS displays.

When it comes to manufacturing high-resolution displays, no ordinary laser will do. Coherent’s Rainer Paetzel and Ralph Delmdahl give us an “under the hood” look at the multiple lasers used in a multi-oscillator design required for laser annealing in “Testing the Limits of Excimer Lasers: Annealing for Advanced Displays,” (read article). Just in time for back to school, this month’s special section includes a listing of community colleges with programs in photonics and optics, (read article). Senior Editor Justine Murphy spoke with professors at several of these institutions for their take on the role of these programs in preparing tomorrow’s workforce. See “Community Colleges: Preparing the Future Photonics Workforce” (read article).

As always, thank you for reading. We hope you enjoy the issue.