Lasers inspect remote objects

12 Mar 2003

The inventors of a remote sensing system say it can determine the makeup of solid targets up to 50 meters away.

Spanish scientists have developed a remote sensing instrument that uses lasers to determine the composition of solid targets up to 50 m away. The method, known as TELELIPS, relies on the spectroscopic analysis of laser induced plasmas and is the brainchild of Javier Laserna and coworkers from the University of Malaga.

According to Laserna, TELELIPS can perform remote open-path analysis of all kinds of solid materials including metals, plastics, rock and wood. He told Optics.org that potential applications include the remote analysis of samples in a hostile environment such as radioactive waste from nuclear reactors, molten glass or other very hot targets.

Although the science at the heart of TELELIPS is not unique, laser induced plasma spectroscopy (LIPS) has been around for sometime, in the past it has been limited to use with short-reach fiber-optic delivery systems, which limits its flexibility.

Laserna and his colleagues extended the technique to free-space operation over tens of meters by using specially designed receiving optics and a very sensitive spectrometer with multichannel detection capability.

Pulses from a Q-switched Nd:YAG laser (230 mJ, 5 ns) are used to ablate the surface of a remote target. Radiation from the resulting plasma is collected via an achromatic refractor telescope and sent to a spectrometer for analysis.

To date, the Spanish team has used TELELIPs to analyse the various alloys of stainless steel placed a distance of 45 m from the spectrometer. By exploiting a pattern recognition algorithm it was able to successfully discriminate between the samples.

"What is unique in this approach is the capability to extract the elementary composition of solid materials that are a large distance from the instrument," said Javier Laserna, from the University of Malaga in Spain. "Other methods of remote chemical analysis such as LIDAR are capable of analysis at very large distances but are limited to molecular species such as gas pollutants in the atmosphere."

Author
Oliver Graydon is editor of Optics.org and Opto & Laser Europe magazine.