Speckle in active millimeter-wave and terahertz imaging and spectroscopy

David M. Sheen; Douglas L. McMakin; Thomas E. Hall

doi:10.1117/12.721323

1 May 2007 Speckle in active millimeter-wave and terahertz imaging and spectroscopy

David M. Sheen, Douglas L. McMakin, Thomas E. Hall

Proceedings Volume 6548, Passive Millimeter-Wave Imaging Technology X; 654809 (2007) https://doi.org/10.1117/12.721323
Event: Defense and Security Symposium, 2007, Orlando, Florida, United States

Abstract

Wideband millimeter-wave imaging techniques and systems have been developed at Pacific Northwest National Laboratory (PNNL) for concealed weapon detection and other applications. These techniques evolved from singlefrequency millimeter-wave holographic imaging methods to wideband three-dimensional planar and cylindrical techniques and systems. The single-frequency holographic method was derived from optical and ultrasonic holography techniques. Speckle is highly significant in this case, and is caused by constructive and destructive interference from multiple scattering locations or depths within a single resolution cell. The wideband three-dimensional techniques developed at PNNL significantly reduce the speckle effect through the use of high depth resolution obtained from the wide bandwidth of the illumination. For these techniques, speckle can still be significant in some cases and affect image quality. In this paper, we explore the situations in which speckle occurs and its relationship to lateral and depth resolution. This will be accomplished through numerical simulation and demonstrated in actual imaging results. Speckle may also play a significant role in altering reflection spectra in wideband terahertz spectra. Reflection from rough surfaces will generate speckle, which will result in significant variation in the reflection spectrum as measured over very wide bandwidths. This effect may make if difficult to interpret spectral absorption features from general reflectance data. In this paper, physical optics numerical simulation techniques will be used to model the reflection from arbitrary random surfaces and explore the effect of the surface on the reflection spectra and reconstructed image. Laboratory imaging and numerical modeling results in the millimeter-wave through the terahertz frequency ranges are presented.

Citation Download Citation

David M. Sheen, Douglas L. McMakin, and Thomas E. Hall "Speckle in active millimeter-wave and terahertz imaging and spectroscopy", Proc. SPIE 6548, Passive Millimeter-Wave Imaging Technology X, 654809 (1 May 2007); https://doi.org/10.1117/12.721323

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