Target induced, turbulence-modulated speckle noise

Conference · Fri Jul 01 04:00:00 EDT 1994

OSTI ID:79896

Scharlemann, E T

Many papers on DIAL for remote sensing have been devoted to the averaging properties of speckle noise from diffuse-target returns; i.e., how many (N) return pulses can be averaged before the I/N reduction in signal variance expected from uncorrelated noise fails. An apparent limit of about 100 pulses or fewer has been the most important factor in determining the accuracy of DIAL measurements using diffusely-scattering targets in the field. The relevant literature is briefly reviewed, and various explanations for the apparent limit are summarized. Recent speckle experiments at LLNL`s Site 300 may suggest that the limit of {approximately}100 pulses is not fundamental. The speckle experiments very clearly show that the limit on signal averaging in this data was the result of long-term ({approximately}1 minute) drifts in the signal returns rather than of any more subtle statistical properties. The long-term drifts are completely removed to the useful limits of the data sets by working with the log-ratio of adjacent pulses. This procedure is analogous (but not identical) to processing the log-ratios of the powers at different wavelengths in a multi-line DIAL system. We think the Site 300 data therefore suggests that as long as the laser system is constructed to ensure that any long-term drifts are identical among the transmitted wavelengths, the log-ratio of the individual returns will provide a data set that does usefully average over a large number of pulses.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 79896
• Report Number(s): UCRL-JC--118287; CONF-9404162--22; ON: DE95014202
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
99 GENERAL AND MISCELLANEOUS
ABSORPTION SPECTROSCOPY
LIGHT SCATTERING
NOISE
OPTICAL RADAR
REMOTE SENSING
SIGNAL CONDITIONING
STATISTICS