Laser induced breakdown spectroscopy for geological analysis

A laser induced breakdown spectroscopy (LIBS) scanning system, comprising:

• a LIBS scanning head comprising:
• a housing;
• an oscillating planar focus laser received in the housing, the oscillating planar focus laser having a laser light emission path along which laser light is directed;
• an optical receiver received in the housing, the optical receiver having an optical output port, the optical receiver having a light reception path along which observed natural light is received, wherein the light reception path is perpendicular to the laser light emission path;
• a dichroic element received in the housing and oriented at 45 degrees relative to the light reception path and the laser light emission path;
• a first focus lens received in the housing for focusing the laser light emitted by the oscillating planar focus laser and receiving natural light;
• and
• a pair of rotatable scanning mirrors received in the housing and located between the dichroic element and the first focus lens, the dichroic element and the pair of scanning mirrors being arranged to provide a shared optical path for the laser light emitted by the oscillating planar focus laser and natural light between the dichroic element and the first focus lens, the pair of scanning mirrors being adapted to two-dimensionally rotate the shared optical path to define a position of a focal plane of the LIBS scanning head, wherein the dichroic element is positioned for directing light emitted by the oscillating planar focus laser along the shared optical path and directing the natural light for reception by the optical receiver, wherein the focal plane forms an intersection with a surface of the geological sample, the intersection comprising multiple focused points on the surface;
• and
• and
• one or more spectrometers coupled to the optical receiver, the one or more spectrometers selected from the group consisting of a visible light spectrometer, ultraviolet light spectrometer, and infrared light spectrometer.

A scanning system for geological samples, comprising:

• a scanning table having a scanning surface;
• a laser induced breakdown spectroscopy (LIBS) scanning head mounted to be moveable relative to the scanning surface of the scanning table, the LIBS scanning head comprising:
• a housing;
• an oscillating planar focus laser received in the housing, the oscillating planar focus laser having a laser light emission path along which laser light is emitted;
• an optical receiver received in the housing, the optical receiver having a optical output port, the optical receiver having a light reception path along which observed natural light is received, wherein the light reception path is perpendicular to the laser light emission path;
• a dichroic element received in the housing and oriented at 45 degrees relative to the light reception path is perpendicular to the laser light emission path;
• a first focus lens received in the housing for focusing the laser light emitted by the oscillating planar focus laser and receiving natural light;
• and
• a pair of rotatable scanning mirrors received in the housing and located between the dichroic element and the first focus lens, the dichroic element and the pair of scanning mirrors being arranged to provide a shared optical path for the laser light emitted by the oscillating planar focus laser and natural light between the dichroic element and the first focus lens, the pair of scanning mirrors being adapted to two-dimensionally rotate the shared optical path to define a focal plane of the LIBS scanning head, wherein the dichroic element is positioned for directing light emitted by the oscillating planar focus laser along the shared optical path and directing the natural light for reception by the optical receiver, wherein the focal plane forms an intersection with a surface of the geological sample, the intersection comprising multiple focused points on the surface;
• a controller for controlling the moveable scanning table and controlling the LIBS scanning head, wherein the controller is configured to:
• (i) cause the scanning table to move with the geological sample disposed upon the scanning surface thereof to a table position in a plurality of table positions defined by a scanning path, wherein the plurality of table positions correspond to a region of interest of the geological sample, the scanning table and the geological sample each being elongate and having a longitudinal axis, the geological sample being disposed on the scanning surface so that a length of the geological sample extends parallel to a length of the scanning table, the scanning table being moved laterally in a direction of the length of the geological sample along the longitudinal axis of the geological sample;
• (ii) cause the focal plane of the LIBS scanning head to be positioned in accordance with the table position;
• (iii) cause laser ablation to be performed on the geological sample using the oscillating planar focus laser of the LIBS scanning head;
• and
• (iv) contemporaneously with performing laser ablation on the geological sample, cause spectroscopy to be performed on the emitted light received by the optical receiver;
• wherein steps (i) to (iv) are performed for each table position in the plurality of table positions.

A method for laser induced breakdown spectroscopy (LIBS), comprising:

• receiving three-dimensional (3D) coordinates of the geological sample;
• determining 3D coordinates of an exposed surface of the geological sample relative to a reference based on a 3D coordinates and orientation of the focal plane of a LIBS scanning head relative to the reference, and 3D coordinates of a scanning surface of a scanning table relative to the reference;
• determining a scanning path for the LIBS scanning head by determining, for each position in a plurality of table positions of the scanning table corresponding to a region of interest of the geological sample, a curve of intersection of the focal plane of the LIBS scanning head and the 3D coordinates of the exposed surface of the geological sample in the region of interest;
• moving the scanning table from a start position to an end position for each position in the plurality of table positions of the scanning table corresponding to the region of interest of the geological sample;
• during the movement of the scanning table from the start position to the end position, at each position in the plurality of table positions of the scanning table corresponding to the region of interest of the geological sample:
• positioning the focal plane of the LIBS scanning head in accordance with the scanning path;
• performing laser ablation on the exposed surface of the geological sample located on the scanning surface of the scanning table using an oscillating planar focus laser of the LIBS scanning head;
• and
• contemporaneously with performing laser ablation on the exposed surface of the geological sample, performing spectroscopy on the emitted light received by an optical receiver.