1. A method for determining the number of objects in an IR image obtained by an IR imaging system, the method comprising: collecting a total of N intensity values for each pixel in an IR image said intensity values having been collected using an IR imaging system comprising a single IR detection device and a sequentially illuminating N band IR Illuminator, where (N≧3), with one fixed filter, said intensity values comprising: 
 I c ( i )=α∫ λ1 λ2 I s i (λ)[ T G 2 (λ) R o (λ)+η R G (λ)] T L (λ) D (λ) dλ+I b where i=1. .. N, such that i is the i th IR band from said illuminator that is sequentially illuminating, α is a constant that depends on an angle and distance from said illumination source, an attenuation of an IR wave in the air, and an integration time of said detecting device, I b is a background intensity, R o (λ) is a reflectance of an object detected by said detection device, R G (λ) and T G (λ) are a reflectance and a transmittance of glass, otherwise R G (λ)=0 and T G (λ)=1, constant η is a percentage of light reflected from glass and received by said detector, otherwise η=0, T L (λ) is a transmittance of said fixed filter, and D(λ) is a responsivity of said detection device; determining a classification for each pixel in said IR image using one of: a best fitting method of a reflectance, and a correlation method; and determining a total number of objects in said IR image based upon said pixel classification.