Well, I’m just back from a week in San Diego for SPIE’s Optics+Photonics meeting. WOW! Everybody seems to have some way to “model” optomechanical behavior but nobody seems to know how to verify that the results are right. That’s why I created “Unified Modeling” (the Ivory and Ebony Optomechanical Modeling Tools): to provide the engineer verifiable confidence in the results.
A good friend of mine likes to declare “You need to know the answer before you do the analysis!” Cute, huh? It always goes over well from the back of the room during a CDR. Well, the next-best-thing (I have found) is to have used the same procedures and theories to analyze a case (any case) for which you already know the answer. One of my favorite test cases is called a “six degree of freedom rigid body check.” You put the model through three translations (X, Y and Z) and three rotations (Rx, Ry and Rz). In optical systems it’s easy to predict the image motions on the detector. They’re either 1.0, computational zeros or some predictable fraction of the back image distance. And, you don’t need a finite element code. You can do it all in a spreadsheet.
AEH analyzed the stability of a hyperspectral sensor. Our client provided the optomechanical influence functions based upon the Zemax optical design. The random analysis showed that the image stability was out of specification by an order of magnitude. A subsequent six degree of freedom rigid body check showed large values in stead of computational zeros. A review of the influence functions showed that they were incomplete. AEH put the Zemax prescription into Ivory to get a complete set of influence functions. This six degree of freedom rigid body check showed computational zeros across the board in a spreadsheet! And subsequent Nastran random stability analysis predicted the performance would be within specification. Which it ultimately proved to be during qualification testing.
Unified modeling provides traceable modeling performance and helps to keep an engineer’s tools sharp.
School starts next week. Good luck to all the children!