Field flattener lens is a type of lens used in modern binocular designs[a] and in astronomic telescopes to improve edge sharpness. Field flattener lenses counteract the Petzval field curvature of an optical system, mitigating the field-angle dependence of the focal length of a system.
Details
[edit]The object in designing a field flattening lens is to create a lens that shifts the focal points of the Petzval surface to lie in the same plane. Consider inserting a pane of glass in a focusing beam. Due to refraction, the focal point of the beam is shifted by dependent on the thickness of the glass. Thus we have a thickness as a function of focal shift:
- .
is given by the radius of curvature of the Petzval surface, . It can be shown, then, that the radius of curvature for the lens that would flatten out the field is given by
Examples of use
[edit]In the 21st century, the New Horizons spacecraft, which was an unmanned space probe sent past Pluto and the Kuiper belt, had a telescope instrument called the Long Range Reconnaissance Imager.[2] LORRI was a reflecting telescope but incorporated a field-flattening lens, with three elements.[2]
See also
[edit]Notes
[edit]References
[edit]- ^ Geary, Joseph (2002). Introduction to Lens Design with Practical ZEMAX Examples. Willmann-Bell. ISBN 0943396751.
- ^ a b Cheng, A. F.; Weaver, H. A.; Conard, S. J.; Morgan, M. F.; Barnouin-Jha, O.; Boldt, J. D.; Cooper, K. A.; Darlington, E. H.; Grey, M. P.; Hayes, J. R.; Kosakowski, K. E.; Magee, T.; Rossano, E.; Sampath, D.; Schlemm, C.; Taylor, H. W. (2008). "Long-Range Reconnaissance Imager on New Horizons". Space Science Reviews. 140 (1–4): 189–215. arXiv:0709.4278. Bibcode:2008SSRv..140..189C. doi:10.1007/s11214-007-9271-6. S2CID 118330150.