Optomechanics – Overcoming the Optical Lexicon for Mechanical Engineers

Colleagues:

Reflecting on the year just (barely) passed a couple of older stories keep coming to mind. 

Early-on, a lens designer friend, Tom, asked me to mount an afocal triplet in a weapon sight.  He said he wanted it to be on a kinematic mount.  I hadn’t heard the term “kinematic mount” before so I did a little research.  Mark’s Handbook had no entry.  Maleev and Hartman’s Machine Design had no entry.  Ham and Crane’s Mechanics of Machinery had no entry.  Sears and Zemansky’s University Physics was not helpful.  Finally, in J. L. Meriam’s Mechanics, Part 2, I found a partial definition, “kinematics … the study of the motions of bodies without reference to the forces which cause the motions….”  I went back to Tom and asked him,  “What kind of mount for optics in a weapon sight doesn’t consider the forces involved?”  Well, he was patient in explaining his higher level of abstract reasoning and suggested that I expand my library. 

Some time later I was sent by the Air Force to a design review in Texas and to report what I found.  I wrote you about this a year or so ago.  The physicists had designed one of the hottest doubled-YAG lasers I’d ever seen and they requested that the cavity be installed on a kinematic mount.  The engineers complied with a classic three-ball mount.  It worked like a champ in the brassboard but the flight unit was unstable.  Everyone was perplexed.  Well, it turned out that the kinematic mount wouldn’t survive the service vibration so the mechanical engineers had conveniently provided screws at each of the balls to lock them out for flight.

In the first case Tom and I worked it out, I ate my humble pie and Tom put me on his patent as a co-inventor.  In the second case the Air Force lost faith in the contractor and cancelled the entire project.

One of the challenges faced by mechanical engineers in the optics industry is lexical:  The engineer may hear what is said but not clearly understand what is meant.

To address this challenge the engineer must ferret-out the acceptable mechanical behavior, regardless of how it was originally expressed, and design it into the required structures and mechanisms.  It takes a little extra digging but has proved to be a winning strategy.

And with that. . . A Happy New Year to you all!

Al H.
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