Patent ID: 8715202

Claim:
A method for image-based determination of carbon dioxide (CO 2 ) concentration in exhaled breath in a non-contact, minimally invasive, respiration measurement environment, the method comprising: receiving at least one IR image of the exhaled airstream of a subject of interest, said image having been captured using a mid-wave infrared camera system having at least one optical filter tuned to an infrared absorption band of CO 2 , each of said received images comprising, in part, an array of pixels having respective measured intensity values obtained at an absorption band of CO 2 ; processing, via a processor, said IR image to isolate pixels in regions associated with background objects in said image, an area of said subject's nose and face, and said exhaled airstream; and to obtain a digital intensity value for each region comprising values of I O , I BB and I CO 2 , respectively, where I O is the intensity value in said area of said subject's nose and face, I BB is the intensity value in said background, and I CO 2 is the intensity value of said exhaled airstream; determining respective radiances R BB and R O from each of said digital intensity values I BB and I O , where R BB is a background radiance and, R O is a radiance of said nose and face; determining a radiance of said subject's exhaled airstream, R CO 2 , based upon said radiances R BB and R O and said digital intensities I O , I BB and I CO 2 ; and determining CO 2 concentration level of said subject's exhaled airstream based on said determined radiance R CO 2 .