What causes sampling artifacts?

Gerald C. Holst

doi:10.1117/12.783715

15 April 2008 What causes sampling artifacts?

Gerald C. Holst

Proceedings Volume 6941, Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XIX; 694102 (2008) https://doi.org/10.1117/12.783715
Event: SPIE Defense and Security Symposium, 2008, Orlando, Florida, United States

Abstract

The sampling process creates an infinite number of new frequencies that were not present in the original scene. For an under-sampled system (which is characteristic of nearly all imaging systems), the replicated frequencies can overlap scene frequencies. An optical anti-alias filter can eliminate the overlapping but does not prevent frequency replication. Frequencies above the Nyquist frequency are eliminated by an ideal reconstruction filter. As overlapping increases or with less than ideal reconstruction, the resultant image is distorted. The phases associated with the replicated frequencies violate linear-shift-invariant system requirements. As a result, movement of the scene with respect to the detector array creates ambiguity in edge locations further distorting imagery. While sampling theory suggests that sharp cutoff filters are required, these filters will create ringing (Gibbs phenomenon) in the image. Replicated spectra that appear in the image are called the spurious response. Out-of-band spurious response (above Nyquist frequency) looks very similar to the input but with phase variation. The phase errors interfere with target recognition and identification. In-band spurious response (frequencies less than the Nyquist frequency) appears somewhat like noise. At this juncture it is not clear how this "noise" interferes with recognition and identification tasks. It may only affect detection. Since the sampling process replicates frequencies, it is possible to extract information with reconstruction band-pass filters whose center frequency is above the Nyquist frequency.

Citation Download Citation

Gerald C. Holst "What causes sampling artifacts?", Proc. SPIE 6941, Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XIX, 694102 (15 April 2008); https://doi.org/10.1117/12.783715

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available