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Proceedings Paper

Transverse Ray Aberration Measurement At 10.6 Microns
Author(s): Nigel D Haig
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Paper Abstract

In the visible part of the spectrum, Computer Aided Design is firmly established in the groove. When an optical system is designed, there is a strong probability that its computed OTF will to some extent resemble its OTF as measured on one of the many proprietary test benches now available. The same is not yet entirely true of Far Infra Red optical systems; in the UK for instance, OTF measurement is performed by a variety of methods such as Edge Scanning, Scanning by Moire Gratings, Line Spread Function Scanning and so on. Typical disadvantages of such techniques are, in the case of Edge Scanning; the need for a very uniform and highly linear responsivity across a relatively large area detector, which will almost certainly be very noisy. In the case of a Moire Scanner, a disadvantage is the need to incorporate relay lenses into the system in order to extend the frequency range to be tested. While the OTF of these lenses may be applied as a correction to the final result, they may not be perfectly aligned in the test setup and this means that the test lens is being interrogated by an already perturbed wavefront. A disadvantage associated with LSF scanning is that unless very narrow source and scanner slits are used the corrections to be applied are very large indeed and do not inspire the customer with confidence, particularly in the region of the higher spatial frequencies. This is, of course, where most of the really interesting information is contained. If, on the other hand, the slits are made so narrow that slit-width corrections become negligible the detector signal levels disappear into the noise.

Paper Details

Date Published: 1 June 1974
PDF: 5 pages
Proc. SPIE 0046, Image Assessment and Specification, (1 June 1974); doi: 10.1117/12.954016
Show Author Affiliations
Nigel D Haig, Royal Armament Research and Development Establishment (England)

Published in SPIE Proceedings Vol. 0046:
Image Assessment and Specification
David T. Dutton, Editor(s)

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