Gas leak detector

• US 20030086091A1
• Filed: 11/08/2001
• Published: 05/08/2003
• Est. Priority Date: 11/08/2001
• Status: Active Grant

• Current Assignee: Uvia Group LLC
• Original Assignee: Pacific Advanced Technology, Inc. (PAT Industries, Inc.)
• Inventors: Hinnrichs, Robert, Hinnrichs, Michele
• Granted Patent: US 6,680,778 B2
• Time in Patent Office: Days
• US Class Current: 356/436
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0208 using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• CPC Class Codes: G01J 3/0229 using masks, aperture plates, spatial light modulators or spatial filters, e.g. reflective filters
• CPC Class Codes: G01J 3/0237 Adjustable, e.g. focussing
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 3/457 Correlation spectrometry, e.g. of the intensity G01J3/453 takes precedence
• CPC Class Codes: G01N 2021/1793 Remote sensing
• CPC Class Codes: G01N 2021/1795 Atmospheric mapping of gases
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis

Abstract

A remote sensing method for detecting and analyzing gases, vapors and flame plumes using an imaging spectrometer. The spectrometric instrument uses Image Multispectral Sensing (IMSS) technology, enhanced by advanced imaging processing techniques and micro-miniature circuitry. These enhancements provide a portable instrument with the capability to remotely detect and image gases, including gas leaks. The technology also provides an analysis of the gas including chemical species and concentrations. The instrument can also remotely detect, image and analyze flames and plumes in the same manner, providing an analysis of the chemical species and concentrations in the flame. Advanced image processing techniques are used to provide gas and plume images and analysis to the operator. These processing algorithms are implemented in micro-miniature circuits such as digital signal processors (DSP'"'"'s) and field programmable gate arrays (FPGA'"'"'s) to provide a field portable instrument.

Claims

1. A method for detecting the presence of a particular gas in a volume of gas comprising the steps of:

(i) presenting an image multispectral sensing apparatus operable for measuring the spectral composition of light emanating from a remote volume of gas, the apparatus having a light input aperture;

then

(ii) gathering light from said volume of gas and focusing an image containing said light on said input aperture;

then

(iii) measuring the spectral composition of light from different parts of the image, and performing image and signal processing algorithms indicating the presence of a gas leak.

2. The method of claim 1 wherein said image multispectral sensing apparatus comprises:

(a) an input optical element adapted to receive and transmit said light emanating from a remote volume of gas; and

(b) a diffractive optical element having an optical axis and disposed to receive said light transmitted by said input optical element and adapted to disperse spectral components of said light into a volume having an area A and a length L; and

(c) an addressable spatial mask disposed between said input optical element and said diffractive optical element comprising a sheet having a planar array of discrete addressable switchable apertures disposed thereon, said apertures being independently operable for directing a controllable portion of said light incident thereon to said diffractive optical element in response to a control signal; and

(d) a photodetector array with pixels having an area substantially equal to the pixel footprint at the addressable mask, if used, said photodetector array being disposed to receive dispersed light from said diffractive optical element; and

(e) means for measuring said controllable portion of said light that is focused upon said photodetector array, said measured controllable portion comprising an image; and

(f) means for changing the distance between said diffractive optical element and said photodetector array in the direction of L.

3. The method of claim 2 wherein said image multispectral sensing apparatus further comprises:

(a) means for controlling the direction of said light incident upon each of said plurality of apertures of said addressable spatial mask to impinge upon said diffractive optical element; and

(b) means for measuring said distance between said diffractive optical element and said photodetector array;

said spectral composition of light emanating from said remote target being determined by combining the images for each position along L; and

(c) computer means operable for applying image processing algorithms to the gas image to provide an enhanced image of the gas.

4. The method of claim 1 further comprising the step of illuminating said volume of gas with light having a wavelength that is absorbed by said particular gas.