Patent ID: 7589837

Claim:
A method for calculating a scaling factor for a sensor, comprising: (a) providing a white tile with known reflectance R w (λ) over a spectra having wavelengths λ; (b) providing two or more color tiles with known reflectance R i (λ) over said spectra; (c) obtaining, via the sensor, measurements V w (λ) for the reflectance of said white tile at each wavelength of said spectra; (d) obtaining, via the sensor, measurements V i (λ) for the reflectance of each of said color tiles at each wavelength of said spectra; (e) calculating a wavelength dependent adjustable constant A(λ) for each wavelength of said spectra as a function of R w (λ) and V w (λ) for said white tile and R i (λ) and V i (λ) for each of said color tiles; and (f) calculating a scaling factor f(λ) for each wavelength of said spectra, as follows: f ⁡ ( λ ) = R w ⁡ ( λ ) V w ⁡ ( λ ) + A ⁡ ( λ ) ⁢ .