Optomechanics – Keep Your Tools Sharp


If spherical surfaces didn’t make pretty good images our optical industry would be entirely different.  As befits a technology that basically works as intended, cliches and rules-of-thumb perform a yeoman’s service.  And they work!  I’m glad that many of you enjoyed my parable about “kinematic” mounts.  Well, that is, they work until they don’t, as in that misunderstanding between the laser physicists and the mechanical engineers.  Thanks for all of your comments.

More recently I’ve been inspired by some of my students to publish the optomechanical influence coefficients of diffraction gratings (i.e., the ratios of a spectrum’s motions to the grating’s motions).  Gratings are often simulated as mirrors.  But the grating’s influence coefficients differ slightly from the mirror’s and there are more of them.  I’ll present my results in Mark Kahn’s conference, “Optical Modeling and Performance Predictions VI,” at SPIE’s meeting in San Diego this August. 

Imaging spectrometers (using gratings of course) are particularly challenging to the optomechanical engineer because the images of both the far-field object and the near-field slit (the spectrum) need to be stabilized simultaneously on the detector plane.  The slit operates as a field stop and the two images behave somewhat (and sometimes importantly) differently.  “Mining” the resulting “data cube” requires close registration between the spectrum and the far-field object’s image.  The grating will work in my Ivory Optomechanical Modeling Tools software.

In San Diego I’ll also present a paper in my own conference, “Optomechanical Engineering 2013.”  This presentation will describe the use of my Jade Optomechanical Modeling Tool.  Jade models the subsurface cracks induced by grinding and polishing.  I use it to engineer, for structural safety, components made of glasses, ceramics and other brittle materials.  As an example I’ll show how I applied Jade to meter-class optical windows for a civilian transport-class aircraft.  The windows have been in service for years.

Engineers develop tools to keep themselves out of trouble.  In the public works domain these have developed into codes and standards that engineers are obligated (by their insurance companies) to follow.  Elsewhere, engineers develop tools for themselves.  In optomechanical engineering there are few rules of thumb to help.  There are, however, a few cliches. 

Summer is coming!  Get out the sunscreen and water skis again!

Keep your tools sharp and your wits even sharper.

Hasta luego, caimán.

Al H.

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