TECHNICAL FIELD

The present invention relates generally to infrared imaging and, more particularly, to gas detection and quantification using thermal images.

BACKGROUND

In the field of optical gas imaging (OGI), various techniques are employed to detect the presence of gases. For example, specific gases may emit and/or absorb infrared (e.g. thermal) radiation in characteristic ways at particular wavelengths. Images may be captured of a scene and analyzed to determine the presence or absence of radiation at certain wavelengths. By comparing these wavelengths to the wavelengths associated with known gases, the presence of a particular gas of interest may be determined.

However, even if the presence of a gas is detected, many existing OGI systems cannot quantify the amount of gas present in a scene to a desirable level of accuracy. As such, conventional gas quantification techniques can be problematic.

For example, gas quantification calculations can be complicated by certain time varying factors such as scattering, emissivity, and reflectance related to infrared radiation associated with background objects and/or passing through the atmosphere. These factors can be problematic when trying to measure minute gas concentration lengths and mass flows in real life situations utilizing passive gas visualization.

Although some of the atmospheric factors can be reduced by decreasing the distance of the infrared imager to the imaged scene, variations in reflectance associated with background objects in the scene can remain problematic, even with short distances. In particular, such reflectance can vary significantly as a function of wavelength, depending on the surface properties of background objects.

For example, background objects may comprise various types of materials such as concrete, grass, wood, steel, paint, and many others. These materials may exhibit different radiometric properties. For example, such materials may have different reflectance properties over different ranges of infrared wavelengths.

A gas present in the scene may also have different radiometric properties over different ranges of infrared wavelengths (e.g., which may or may not overlap with those associated with the background materials). As a result, it can be difficult for conventional OGI systems to successfully quantify an amount of detected gas in a scene if they are not also provided with sufficient information regarding the radiometric values associated with the background portions of the scene over different ranges of infrared wavelengths. In particular, many conventional OGI systems are generally limited to detection in a single wavelength band and are therefore unable to support sufficiently accurate gas quantification determinations.

SUMMARY

Improved techniques for quantification of detected gases are provided. In various embodiments, two or more types of infrared sensors may be used to detect different ranges of infrared (e.g., thermal) wavelengths for background portions of a scene. By tracking the motion of background objects and imaging them with infrared sensors associated with different wavelength ranges (e.g., wavebands), a radiometric scene map of multiple radiometric values corresponding to the different wavelength ranges may be determined for the background portions of the scene. The radiometric scene map may be used to better discriminate between a detected gas and background portions of the scene, thus improving the system's ability to quantify the gas with improved accuracy over conventional single-band techniques.

In one embodiment, a method includes receiving infrared radiation from a scene at a sensor array comprising first and second sets of infrared sensors associated with first and second wavelength ranges of the infrared radiation, respectively; capturing first and second images by the first and second sets of infrared sensors, respectively; detecting a background object in the first image; tracking the background object to identify the background object in the second image; updating a radiometric scene map with first and second radiometric values associated with the first and second images and correlated to a location of the background object in the scene; and performing gas quantification using the radiometric scene map.

In another embodiment, a system includes a sensor array configured to receive infrared radiation from a scene, the sensor array comprising: a first set of infrared sensors configured to capture a first image associated with a first wavelength range of the infrared radiation, and a second set of infrared sensors configured to capture a second image associated with a second wavelength range of the infrared radiation; and a processor configured to: detect a background object in the first image, track the background object to identify the background object in the second image, update a radiometric scene map with first and second radiometric values associated with the first and second images and correlated to a location of the background object in the scene, and perform gas quantification using the radiometric scene map.

The scope of the invention is defined by the claims, which are incorporated into this section by reference. A more complete understanding of embodiments of the invention will be afforded to those skilled in the art, as well as a realization of additional advantages thereof, by a consideration of the following detailed description of one or more embodiments. Reference will be made to the appended sheets of drawings that will first be described briefly.

