US-12625266-B2 - Method of operating a LIDAR system for detection of gas

US12625266B2US 12625266 B2US12625266 B2US 12625266B2US-12625266-B2

Abstract

A lidar system for detection of a gas comprises an optical transceiver for transmitting and receiving optical radiation. A method of operating the system comprises performing spatially scanned sensing measurements of the gas across a system field of view, and analyzing the sensing measurements to determine the presence and location of excess of the gas in the system field of view. Based on the determined location, an adjusted system field of view is determined and spatially scanned sensing measurements of the gas are performed across the adjusted system field of view to obtain sensing measurements at higher spatial resolution.

Inventors

Xiao Ai
James Titchener
Alexander DUNNING

Assignees

QLM Technology Limited

Dates

Publication Date: 20260512
Application Date: 20220608

Claims (11)

1 . A lidar system, comprising: a lidar light transceiver; an optical beam scanner including a plurality of encoders configured to generate encoder data corresponding to a direction of spatially scanned light; and at least one of a processor configured to process the encoder data and generate spatially registered range and gas concentration data based thereon and a set of processors configured to cooperate to process the encoder data and generate the spatially registered range and gas concentration data based thereon, wherein the lidar light transceiver, the optical beam scanner, and the at least one of the processor and the set of processors are operably coupled and configured to cooperate to determine, based on a first optical beam, a distance to a remote surface, and determine, based on the first optical beam, a gas absorption of the spatially scanned light over the distance.
2 . The lidar system of claim 1 , wherein the lidar light transceiver includes a laser device operable to output first output radiation having a continuous wave output, wherein the lidar light transceiver includes at least one detector configured to receive scattered radiation, and wherein the lidar light transceiver includes at least one optical guide element configured to guide the received scattered radiation to the at least one detector.
3 . The lidar system of claim 1 , wherein the lidar light transceiver is mechanically fixed with respect to the optical beam scanner, and wherein the lidar light transceiver includes pan and tilt stages to point the lidar light transceiver at a target area for transmission and reception of laser radiation.
4 . The lidar system of claim 1 , wherein the optical beam scanner includes a plurality of prisms.
5 . The lidar system of claim 4 , wherein the optical beam scanner includes a plurality of drive motors, and wherein each of the drive motors is operably coupled to a respective one of the prisms to rotationally drive the respective one of the prisms.
6 . The lidar system of claim 1 , further comprising: a system controller operably coupled to the at least one of the processor and the set of processors to receive the spatially registered range and gas concentration data therefrom; and an image processor operably coupled to the system controller to send first signals thereto and receive second signals therefrom, wherein the system controller is configured to form a gas concentration image based on the spatially registered range and gas concentration data.
7 . The lidar system of claim 1 , further comprising: a controller configured to: control the optical beam scanner to perform first spatially scanned sensing measurements of a gas across a system field of view at a first spatial resolution, form a gas concentration image from analyzing the sensing measurements, determine presence and location of excess of the gas in the system field of view based on the gas concentration image, determine an adjusted system field of view based on the determined location, and control the optical beam scanner to perform second spatially scanned sensing measurements of the gas across the adjusted system field of view at a second spatial resolution.
8 . The lidar system of claim 7 , wherein the controller is further configured to: control the optical beam scanner to perform a spatially scanned lidar measurement of ranges to surfaces and corresponding gas concentration pathlength.
9 . The lidar system of claim 1 , wherein the lidar light transceiver, the optical beam scanner, and the at least one of the processor and the set of processors are operably coupled and configured to detect a concentration of a greenhouse gas.
10 . The lidar system of claim 1 , wherein the lidar light transceiver, the optical beam scanner, and the at least one of the processor and the set of processors are operably coupled and configured to locate and quantify at least one of: methane and carbon dioxide.
11 . The lidar system of claim 1 , wherein the lidar light transceiver, the optical beam scanner, and the at least one of the processor and the set of processors are operably coupled and configured to locate and quantify at least one of: ammonia and carbon dioxide.

Description

CROSS REFERENCE TO RELATED APPLICATION The present application claims the benefit of priority of U.S. Provisional Patent Application No. 63/202,375, filed Jun. 8, 2021, entitled METHOD OF SCANNING IN A LASER LIDAR SYSTEM, the entire disclosure of which is incorporated herein in its entirety by reference. FIELD OF THE INVENTION The present invention relates to a method of operating a lidar system for detection of a gas, for example a particular gas that might be present in an environment in a larger concentration than normal. BACKGROUND An example of a lidar system for gas detection is described in UK Patent Application Publication No. GB2586075A by J. Titchener and X. Ai, entitled “Rapidly tunable diode lidar” and published 3 Feb. 2021 (“GB2586075A”), which uses a tuned laser wavelength to detect a gas. Some of the methods and systems described below are directed to improving the resolution of gas detection. Some of the methods and systems described below may solve other problems. SUMMARY There is provided in the following a method of operating a lidar system for detection of a gas, wherein the system comprises an optical transceiver for transmitting and receiving optical radiation. The method comprises performing spatially scanned sensing measurements of the gas across a system field of view; analyzing the sensing measurements to determine the presence and location of excess of the gas in the system field of view; based on the determined location, determining an adjusted system field of view and performing spatially scanned sensing measurements of the gas across the adjusted system field of view to obtain sensing measurements at higher spatial resolution. There is also provided a system configured to perform the foregoing method. The method may be implemented by way of a computer readable medium. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings in which: FIG. 1 is a schematic diagram of a lidar gas detection system in which any of the methods to be described here may be implemented; FIGS. 2A-C are a series of diagrams illustrating how dual prisms may be used to steer an optical beam; FIGS. 3A and 3B are respectively a perspective and a cut-away view illustrating how dual rotating prisms may be incorporated into a mechanical design; FIGS. 4A and 4B show examples of how an optical beam can be made to scan around a field of view in a variety of different patterns by using dual rotating prisms; FIGS. 5A and 5B show examples of how an optical beam can be made to scan around in circles with different sizes by using synchronized rotation of dual prisms; FIGS. 6A-C show an example of how an optical beam can be made to scan around a reduced size field of view by superimposing a sinusoidal oscillation of the relative prism-to-prism angle onto a synchronized rotation of dual prisms; FIGS. 7A-C show an example of how an optical beam can be made to scan around a field of view in a spiral pattern by reducing the rate of the superimposed oscillation of the prism-to-prism angle with respect to the rate of the synchronous rotation of the prism pair; FIGS. 8A-C show an example of how an optical beam being scanned in a spiral pattern can be made to maintain beam scanning speed by increasing the synchronous rotation rate of the prism pair as the scan spirals towards the center of the field of view; FIGS. 9A-C show a series of images obtained with a lidar gas detection system with different fields of view created by a dual rotating prism scanner; FIG. 10 is a schematic diagram of a gas lidar beam pointing and scanning system; FIG. 11 is a flowchart of a method of operating a lidar gas detection system. DETAILED DESCRIPTION OF ONE OR MORE EMBODIMENTS For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. At least one embodiment of the present invention will be described and shown, and this application may show and/or describe other embodiments of the present invention, and further permits the reasonable and logical inference of still other embodiments as would be understood by persons of ordinary skill in the art. It is understood that any reference to “the invention” is a reference to an embodiment of a family of inventions, with no single embodiment including an apparatus, process, or composition that should be included in all embodiments, unless otherwise stated. Further, although there may be discussion wi