Handheld libs spectrometer

Abstract

A handheld LIBS analysis method features a moveable laser focusing lens, and a laser beam directed to a sample via the laser focusing lens. A first mirror includes an aperture for the laser beam. This mirror is oriented to re-direct plasma radiation for delivery to a detection fiber.

What is claimed is: 
     
         1 . A handheld LIBS analysis method comprising:
 providing a laser source which produces a laser beam;   directing the laser beam from the laser source through an aperture in a first fixed mirror and through a movable laser focusing lens to a sample;   directing plasma radiation from the sample through the movable laser focusing lens and to a detection fiber via the first fixed mirror;   directing said plasma radiation to a spectrometer subsystem via the detection fiber;   controlling movement of the movable laser focusing lens; and   detecting and reporting elements present in the sample via an output of the spectrometer subsystem.   
     
     
         2 . The method of  claim 1  in which the first fixed mirror with said aperture is an off-axis parabolic mirror which focuses the plasma radiation. 
     
     
         3 . The method of  claim 2  in which the numerical aperture of the off-axis parabolic mirror matches the numerical aperture of the detection fiber. 
     
     
         4 . The method of  claim 2  in which the off-axis parabolic mirror is approximately 12.5 mm in diameter and approximately 15 mm long. 
     
     
         5 . The method of  claim 1  in which the detection fiber is oriented along an axis parallel to the laser beam. 
     
     
         6 . The method of  claim 5  further including re-directing plasma radiation from the first fixed mirror to the detection fiber via a second mirror. 
     
     
         7 . The method of  claim 1  in which the detection fiber is oriented along an axis perpendicular to the laser beam. 
     
     
         8 . The method of  claim 1  further including performing a calibration routine. 
     
     
         9 . The method of  claim 8  in which said calibration routine includes moving the laser focusing lens until the laser beam strikes a calibration standard. 
     
     
         10 . The method of  claim 1  further including performing an auto-focus routine, an auto-clean routine, a moving spot cycle, and a purge cycle. 
     
     
         11 . The method of  claim 10  in which performing said moving spot cycle includes moving the laser focusing lens to a plurality of locations and, at each location, powering the laser to produce a laser beam, and processing an output of the spectrometer subsystem. 
     
     
         12 . The method of  claim 10  in further including performing a purge cycle during said moving spot cycle. 
     
     
         13 . The method of  claim 1  in which directing said plasma radiation to the spectrometer subsystem via the detection fiber includes directing said plasma radiation via a plurality of optical bundles coupled between the optical fiber and the spectrometer subsystem. 
     
     
         14 . The method of  claim 1  further including directing the laser beam through an aperture in an end plate. 
     
     
         15 . The method of  claim 1  further including:
 initiating a laser pump sequence in response to a fire command, 
 analyzing radiation to determine if the laser is aimed at a sample, 
 if the analysis reveals the laser is aimed at the sample, continuing the laser pump sequence, and 
 if the analysis reveals the laser is not aimed at the sample, halting the laser pump sequence. 
 
     
     
         16 . The method of  claim 15  in which the analyzed radiation is low intensity pre-firing radiation emitted by the laser and the method further includes detecting said low intensity pre-firing radiation produced by the laser and reflected by the sample. 
     
     
         17 . The method of  claim 16  including comparing the intensity of said detected low intensity pre-firing radiation to a predetermined minimum and halting the laser pump sequence if the detected intensity of said low intensity pre-firing radiation is less than said predetermined minimum. 
     
     
         18 . The method of  claim 15  in which the analyzed radiation is the plasma radiation and in which determining if the laser is aimed at the sample includes analyzing said plasma radiation. 
     
     
         19 . The method of  claim 18  including measuring the maximum signal output in a predetermined wavelength range. 
     
     
         20 . The method of  claim 19  including automatically halting the laser pump sequence if the maximum signal amplitude in a predetermined wavelength range is less than a predetermined amplitude. 
     
     
         21 . The method of  claim 20  in which the predetermined amplitude is 200 and the predetermined wavelength range is 200-400 nm. 
     
     
         22 . A handheld LIBS analysis method comprising:
 providing a laser source which produces a laser beam;   directing the laser beam from the laser source through an aperture in a first fixed mirror and through a movable laser focusing lens to a sample;   directing plasma radiation from the sample through the movable laser focusing lens and to a detection fiber via the first fixed mirror, the numerical aperture of the first fixed mirror matching the numerical aperture of the detection fiber;   directing said plasma radiation to a spectrometer subsystem via the detection fiber; and   detecting and reporting elements present in the sample via an output of the spectrometer subsystem.