Telescope optical path length vs focal length

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SUMMARY

The discussion focuses on the relationship between optical path length and focal length in a three-mirror off-axis telescope design. The user seeks clarification on how these two parameters can be constrained independently while using Zemax for optimization. It is established that increasing the focal length can lead to a reduction in the optical focal length when minimizing the RMS radius in the design. The user expresses confusion regarding the distinction between optical path distance and focal length, indicating a need for further explanation.

PREREQUISITES
  • Understanding of optical path length in telescope design
  • Familiarity with focal length concepts in optics
  • Experience using Zemax for optical system optimization
  • Knowledge of RMS radius in optical performance evaluation
NEXT STEPS
  • Research the principles of optical path length in multi-element systems
  • Learn about the optimization techniques in Zemax for telescope design
  • Explore the relationship between focal length and optical performance metrics
  • Investigate the implications of RMS radius on optical system quality
USEFUL FOR

Optical engineers, telescope designers, and students in optics seeking to deepen their understanding of the interplay between optical path length and focal length in complex optical systems.

balaonspace
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Hi

I am trying to design a three mirror off axis telescope. The free parameters are the offset between the apertures and distance between the surfaces.

My question is for a system with 'n' elements/surfaces (n=3 in my case) is there a relation between optical path length and focal length of the system.

I don't want to go too descriptive about this problem. If it might help I can upload a pic in some webpage.

bala
 
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the distance between well yes`. if you have one eye on a lens and the other open. Eye with more light will give more distance but less focus. some what a distortion ? or a dispacement of light'. i would like to see it
 
http://img828.imageshack.us/img828/5718/phyfor.png

In this image 'c' (which i interpret as the optical path distance) and 'f' the focal length can be constrained independently.
For example when i design a system with high focal length with optical path, and optimise the same in zemax, the system focal length reduces to optical focal length for a design with smallest 'rms' radius.
I cannot quiet grasp the difference between the two quantities here.
Thank you for reading.
I am not convinced that i explained my problem clearly. let me know if i need to clarify any part.
 
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