# Help with a presentation on thermal analysis of an opto-mechanical system

• Engineering
• ThermalOptoLearner

#### ThermalOptoLearner

Analysis of an opto-mechanical system

Hello,

@berkeman
I have created a presentation about the thermal analysis of an infrared seeker head and need feedback from experienced engineers. The presentation should not be longer than 10 min, so I have limited myself to the most necessary:

Slide1 preparation / data collection:
a) Main objectives of the analysis:

-Check function (spec. image quality, stability,..)
-Gain insights
-Derive suggestions for design changes

b)Environmental conditions:
Operating modes, transportation, storage
MIL-STD-310 (Global climatic data for the development of military products)
MIL-STD-810 (Test method for determining the environmental impact on equipment)

c) Characteristics of the system elements (with picture):
Mass, dimensions, cross-sectional area, surface area, surface emission
conductivity, specific heat, thermal expansion coefficients, convection coefficients

Slide 2 Modeling
a) Simplified analytical calculations as a starting point:

thermal capacities:
thermal time constants:
b) Modeling in Ansys Zemax

Can you help me to find the most important points here?

Slide 3 Analysis:
Here I also need information about the most important steps in a thermal analysis of an opto-mechanical system. Slide 4 Sources and useful information
Websites:
https://wp.optics.arizona.edu/optomech/optomechanics-reference-papers/#stray
https://support.zemax.com/hc/en-us

Publications:
Harvard-Smithsonian Center for Astrophysics, WARREN R. BROWN, DANIEL G. FABRICANT, AND DAVID A. BOYD - A Detailed Thermal Analysis of the Binospec Spectrograph
I would be very grateful if you could help me to complete the missing points.

Thank you very much
OptoThermalLearner

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For any presentation you need a good specific title (which is not void of content: an analysis of a system......Duh really?) Then
1. Say what it is you are going to say in the talk.
2. Say why it is interesting
3. Say how you will know when you are successfully finished the talk.
4. Commence.. Be charming and informative.
What you have provided is a very general outline. It seems fine (except for that ctiticism). Zemax is good for specific analysis of a completed design when it is time to finalize. Before that it is usually overkill (for a good designer). Better for a formal (documentational) design review. What is it you are trying to accomplish with the presentation? Ten minutes is no time at all.

ThermalOptoLearner
So this is a one-on-one presentation or is there an "audience". Did they give this to you as preparation for the interiew? (kinda like homework?....I've not seen this before. I think I hate it!!. Is this a second interview?)
So the basics are still the same as a lecture, I guess. Mostly it is their test of your ability to communicate I think. The technical parts can be covered by their questions. Keeping that in mind the technical analysis needs to be correct but not too involved I would think. Coherence probably more important than detail. Good Luck and make some new friends. Ask them good questions if possible.

DeBangis21
Yes, this is the second interview, the first was online.
It has been said that this is a good way to get to know the applicant better. Unusual but understandable. I have now spent many hours delving into the topic and will briefly present the most important points.

Can you tell me the key points of an optical performance analysis? e.g. RMS spot expansion? I would like to get the job and show that I am able to figure out what the most important steps and points are in a thermal drift analysis.

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I don't know the system, so it is a little difficult. I assume this is a (~far IR?) based imaging system of some kind. Not my specific area of expertise, but I'll guess that major problems have to do with the response speed of the imaging. I will offer you historical context instead (BF Skinner pigeon guided missile) This would require some highly trained and fast pigeons.

Unfortunately, the link doesn't help me.
I am looking for the top 3 evaluation criteria for an opto-mechanical system.

I think we have a disconnect here. Are you looking for us to provide general presentation advice (which is what you got so far) or to do research for you on the talk's content? (what you seem to be asking for now)

hutchphd
I was hoping to get a few hints on what other important points I could include to present as detailed a thermal analysis strategy as possible.

I am currently working through a Zemax Opticstudio beginners course,
- Evaluation of optical performance due to thermal stress

and integrate this point into my presentation.

I will give a second presentation (topic of your choice). In it I would like to cover the two points:
- Optimization with Zemax
- Tolerance analysis with Zemax
within 10 minutes

Do you think that all together is a sufficiently detailed summary of the thermal analysis of an opto-mechanical system?

It depends upon the system requirements. Why are you focussing on thermal issues? Do you know this is the largest problem? Insufficient information for detailed analysis from me.
The question for me is not what software you use or how to find the answers but do you recognize the proper questions to ask. That is the art of engineering.
The fact that you seem to think there is a one size fits all template for this process worries me....it is management fallacy IMHO. My process will be very different from yours.

I focus on thermal analysis because this is the task to present strategies for the analysis of thermal shifts in optomechanical systems. I only have freely available information about the company's product and know which software they work with. I do not have more information. In order not to make the presentation too general, I have tailored the presentation to an IR Seeker. As the topic is completely new to me and I have to give a presentation in 2 days, any advice on how and where I can get this information as quickly as possible would be very helpful.

Can you outline your process for me?

It is my process, and may not be yours. It involves knowing as much as I possibly can know. I am reminded of Prof Linus Pauling's answer to a similar question: "Dr Pauling how is it you have so many good ideas?." He said, "Well, I have a lot of ideas and I eliminate the bad ones" That is my process. Not software, not outlines, not brainstorming meetings, not Gantt charts. (These are important and alas I do not have Pauling's Brain.) But I have ideas and sufficient knowlege to efficiently and without prejudice eliminate the bad ones
Also I have some concerns about your potential employer so ask them questions too.

Vanadium 50 and ThermalOptoLearner
It sounds like at least part of what they are looking for is to see how you find out what you need to know, but don't already know. "I asked a bunch of strangers on the internet" is probably not the response they are hoping for.

I would also recommend being forthright when you don't know something. I've seen people try to bluff their way through that, and it has never gone well.

hutchphd
I would also recommend being forthright when you don't know something. I've seen people try to bluff their way through that, and it has never gone well.
Yeah, I was a bit concerned by this...
ThermalOptoLearner said:
As the topic is completely new to me and I have to give a presentation in 2 days, any advice on how and where I can get this information as quickly as possible would be very helpful.

I would also recommend being forthright when you don't know something. I've seen people try to bluff their way through that, and it has never gone well.
I was put into this position once and it is an experience I will never forget.

I had a student once, and we're at a workshop and he's clearly trying to bluff his way through it. Let's just call it the Weyland-Yutani method. Afterwards he told me that he wasn't completely sure, but he thought he managed to hide that. I told him that it might have worked, except for one thing: the guy in the front row? That's Yutani.

We'll just call that a teaching moment.

hutchphd, ThermalOptoLearner, gmax137 and 1 other person
I told him that it might have worked, except for one thing: the guy in the front row? That's Yutani.
That's classic.

Thank you guys, advice from strangers on the internet can sometimes be helpful. I have finished my presentations and am overall satisfied with what I have learned in such a short time. Above all, I noticed that I enjoy the topic and that, as a beginner, I am able to collect and implement the relevant information. Unfortunately, I spent a lot of time looking for suitable literature and consulted many books and articles on the topic, all in English and not in my native language. It was a steep learning curve including a short introduction to Zemax. But now I feel ready for the job. Wish me good luck.

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