Optomechanics – Fracture of Cemented Lenses at Temperature

Colleagues:

I recently completed a job as an advisor to an airborne multi-spectral sensor system project.  My tasks included advice on lens mounting (metal rings vs. adhesive bonding), environmental sensitivities (temperature, vibration and shock), alignment procedures (tooling and adjustments) and manufacturing processes (bonding, glass finishing and failure analysis).

A major concern was the fracture of cemented lenses at high and low temperatures.  Understanding the physics of glass fracture was instrumental in both understanding the causes of the fractures of cemented assemblies and designing them to avoiding failures in the service environment.  The figures below show the analysis and test of a cemented glass coupon.  The contour plot shows the stress distribution in the test coupon and the photo shows the resulting de-lamination and fracture at low temperature.

In one of the finished cemented doublets, analyzed below, the fillet in Glass 2 needed special finishing to strengthen it against the stresses at low temperature.

This project was very challenging.  Great sport!

I hope your summertime was as interesting as mine. 

Look out, here come the Holidays.  Cheers!

Al Hatheway
10-12-07

Optomechanics – SPIE

Colleagues:

I’ll be presenting my tutorial “Optomechanical Analysis” at SPIE’s Optics and Photonics Symposium.  The time and date are:

28 August 2007
830 AM to 530 PM
Marriott Marina Hotel, San Diego and
San Diego Convention Center (next door to the hotel)

I’ll be discussing and comparing various methods to evaluate the mechanical engineers’ impacts on the optical instruments and systems they design and analyze.  You may read the abstract and sign-up for the course by clicking on the following web-site:

http://spie.org/x1139.xml?course_id=E0783533

I’ll also be hosting a meeting of the Optomechanical/Instrument Technical Group that same evening, the 28th, 8 to 10 PM.  Larry Stepp will be our feature speaker and will discuss the mechanical challenges of the Thirty Meter Telescope project, of which he is the Telescope Department Head.  Following Larry we’ll get an up-date from Rob Bernier on how he implemented some of your suggestions from last year’s meeting on metrology challenges in the JWST project at Tinsley.

Then, on Wednesday the 29th and Thrusday the 30th I and some of our colleagues will chair sessions of our biennial conference, “New Developments in Optomechanics.”  We’ll have over 30 oral presentations during the days and almost a dozen poser papers Wednesday evening.

It ought to be a great time!  I hope to see you all there.

Al H.
7-19-07

Optomechanics – Ivory: Accurate Model of Imaging Behavior

Colleagues:

An interesting, and challenging, recent job was:

“Find a way to assure a 7 microradian boresight shift
and image jitter performance specification for a mid-wave FLIR
in an airborne thermal and random vibration environment”.


The solution used the Unified Modeling mode of the Ivory Optomechanical Modeling ToolsIvory accurately modeled the imaging behavior of the FLIR and generated a NASTRAN optomechanical finite element model for the dynamic analysis. 

The model’s results were validated against Zemax environmental analyses, longhand (Excel, actually) calculations and rigid body checks in NASTRAN giving the instrument’s focal length.  (Yes, NASTRAN can calculate the focal length of on optical instrument.)  The indicated uncertainties were all less than 1.8%.

The model turned out to be a very effective design tool.  It was run more than 50 times over a few weeks.  We were able finally to demonstrate safety margins of between 25 and 1000 on the image jitter and boresight shift requirements. 

You may see some of the product from this effort in the attached “pdf” file.  My client has all of my modeling files, which are heavily annotated, so he can “mesh” his ProE solid models as they mature and replace the beam and shell elements of my early model.  Ivory’s Unified Optomechanical Model will work, of course, in any NASTRAN model he chooses to put together to check the progress of the design.

The Ivory Optomechanical Modeling Tools answered the challenge.  If you have any interest in these kinds of things, please feel free to give me a call.  I’d be happy to talk with you.

I hope you all survived Spring Break!

Al Hatheway
5-3-07

Optomechanics – SPIE

Colleagues:

This is a final reminder:  I’ll be presenting my tutorial “Optomechanical Analysis” at the SPIE’s Orlando conference on Defense and Security.  The time and date are,

12 April 2007
830 AM to 530 PM
Orlando World Center Marriott Resort and Convention Center

In it I’ll be discussing and comparing various methods to evaluate the mechanical engineer’s impact on the optical instruments and systems.  You may read the abstract and sign-up for the course by clicking the following web-site:

http://spie.org/Conferences/Programs/07/dss/shortcourses/index.cfm?fuseaction=shortcoursedetail&course=SC781

I’ll also be Exhibiting at Booth No. 1307.  I’ll be passing out complimentary demonstration copies of my Ivory Optomechanical Modeling Tools as long as they last.  Please drop by and say “Hello.”

I hope to see you all there.

Al Hatheway
3-21-07

Optomechanics – Very High Precision Optical Vibrometer

Colleagues:

I have recently finished the mechanical design of a very high precision optical vibrometer (it can measure picometer motions at distances of kilometers).  I helped to conceive the instrument and my name is one of those on my client’s patent application.  It all came out of a brain-storming session about two years ago.  It was intended for use by one individual so size and weight were critical.

The design was developed as a 3D solid model in AutoCad 2007.  A partial view of the assembly is attached.  It is a zooming optical system with six (6) moving lens groups.  The lens groups are all servo-controlled.  An alternate lens attachment (not shown) permits working distances as short as 50 meters.  The layout along with indentured drawing and parts lists were delivered to my customer who wished to prepare the (160 or so) mechanical drawings in-house.  They converted the AutoCad file to ProE for their draftsmen without difficulty and are now proceeding into the hardware.

I’m looking around for another interesting project.  If you think you might have something I’d like to talk to you about it.

I hope the beginning of 2007 has found you healthy and prosperous.

Al Hatheway
3-2-07

Optomechanics – SPIE’s Optomechanical/Instrument International Technical Group

Dear Colleagues:

Welcome all to the grand year of 2007!  This is also the 20th anniversary of SPIE’s Optomechanical/Instrument International Technical Group.

On August 20, 1987, we had our first gathering during SPIE’s Annual Meeting in San Diego.  That first meeting was chaired by Roger Reiss and the agenda included Roger, Bill Barnes Jr., Paul Yoder, Dan Vukobratovich, Don O’Shea, Warren Smith and myself.  The assembly elected Roger to be the first chairman of the Group and we decide to organize our own conferences dedicated to the arts of optomechanical engineering and instrument design.  We’ve been presenting them every-other year (and sometimes more frequently) ever since.

This summer we will be presenting our biennial conference (see the attachment).  This is the perfect opportunity to get the acclaim you deserve for all your hard work and to network with the best pool of technical talent in our industry.

We are also planning an informative evening meeting that should stimulate conversation and a lot of good ideas.  Last year we stirred-up the metrology activities at SSG-Tinsley.  Who knows what trouble we’ll get you into this August?

I plan to renew old friendships, stir-up some new ideas, meet new people and have a great time.  Just what this great year, 2007, ought to be all about!

Here’s to hoping to see you all there.

Al Hatheway
1-2-07

P.S. – Be sure to get your abstracts in early!

Optomechanics – Year in Review

Colleagues:

Happy Holidays!!!

We have been very busy this year: a very advanced multi-spectral sensor, an active remote optical sensor with six moving lens groups, actuators for an spacecraft assembly shop and a FLIR with stringent boresight requirements (among other joys).  I’ll try to get out more on these later.

We have also been busy incorporating NASTRAN unified modeling capabilities into Version 2.0 of our Ivory(tm) Optomechanical Modeling Tools suite of software.

As an expression of the Season’s Goodwill we will honor all purchases of Ivory2 received by January 31, 2007, by including the NASTRAN unified modeling tools and respecting our current prices.  Just the kind of offer to tickle an optomechanical engineer’s sugar-plumb dreams.

For more information on Ivory2 please open the attachment or visit our web site.

Have a Merry Christmas and a Happy New Year!

Let the good times roll.

from all us folks at Alson E. Hatheway Inc.
December 12, 2006