Improvement of speckle correlation fringes by adaptive correction using twisted nematic LCD

Erwin Hack; Phanindra Narayan Gundu

doi:10.1117/12.695289

15 September 2006 Improvement of speckle correlation fringes by adaptive correction using twisted nematic LCD

Erwin Hack, Phanindra Narayan Gundu

Proceedings Volume 6341, Speckle06: Speckles, From Grains to Flowers; 63410L (2006) https://doi.org/10.1117/12.695289
Event: Speckle06: Speckles, From Grains to Flowers, 2006, Nimes, France

Abstract

Subtraction correlation fringes in Digital Speckle Pattern Interferometry are described as a smoothly varying intensity distribution multiplied with high-frequency noise that is due to the random distribution of speckle intensity and speckle phase across the image plane. Although intensity modulation and speckle phase can be eliminated by phase stepping or other phase retrieval methods, noise is not eliminated completely due to the limited dynamic range of image processing, given by the saturation level of the camera, the digitisation depth and the electronic noise. Digital image processing techniques have been developed to reduce the speckle noise from the fringe pattern, but in most cases the fringes are not restored completely. In this paper the speckle noise is reduced before image digitisation by reducing the range of either the modulation intensity values or the speckle phase values, or both, in the interference pattern. This is done adaptively by using programmable twisted nematic LCDs. Since the manipulation is performed for each pixel independently in the reference beam, the imaging quality is retained and no blurring occurs. We quantitatively discuss the improvement and limitation of the method. The experimental verification is performed using an amplitude-only or phase-only spatial light modulator in a conventional ESPI setup.

Citation Download Citation

Erwin Hack and Phanindra Narayan Gundu "Improvement of speckle correlation fringes by adaptive correction using twisted nematic LCD", Proc. SPIE 6341, Speckle06: Speckles, From Grains to Flowers, 63410L (15 September 2006); https://doi.org/10.1117/12.695289

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