skip to main content

Title: Avoiding the False Peaks in Correlation Discrimination

Fiducials imprinted on laser beams are used to perform video image based alignment of the 192 laser beams in the National Ignition Facility (NIF) of Lawrence Livermore National Laboratory. In many video images, matched filtering is used to detect the location of these fiducials. Generally, the highest correlation peak is used to determine the position of the fiducials. However, when the signal to-be-detected is very weak compared to the noise, this approach totally breaks down. The highest peaks act as traps for false detection. The active target images used for automatic alignment in the National Ignition Facility are examples of such images. In these images, the fiducials of interest exhibit extremely low intensity and contrast, surrounded by high intensity reflection from metallic objects. Consequently, the highest correlation peaks are caused by these bright objects. In this work, we show how the shape of the correlation is exploited to isolate the valid matches from hundreds of invalid correlation peaks, and therefore identify extremely faint fiducials under very challenging imaging conditions.
Authors:
Publication Date:
OSTI Identifier:
964503
Report Number(s):
LLNL-CONF-415387
TRN: US0903861
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: Presented at: SPIE Optics & Photonics, San Diego, CA, United States, Aug 02 - Aug 06, 2009
Research Org:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 42 ENGINEERING; 99 GENERAL AND MISCELLANEOUS; ALIGNMENT; DETECTION; LASERS; LAWRENCE LIVERMORE NATIONAL LABORATORY; OPTICS; REFLECTION; SHAPE; TARGETS; US NATIONAL IGNITION FACILITY