Patent ID: 8441641

Claim:
A method for producing color spectral data of an article, said method comprising the steps of: a) measuring individual specimen reflection intensity data S n of lights emitted from a number n light unit of a first set of one or more light emitting units and reflected by said article using one or more detectors, said S n is measured over a range of wavelength λ and under a voltage U n applied to said number n light unit; b) obtaining individual characterized spectral power distribution data SPDC n,λ,t of said number n light unit, said SPDC n,λ,t characterizes the number n light unit over the range of wavelength λ, at one or more known temperatures t and under one or more individual voltages V n,t applied to said number n light unit; c) generating individual raw spectral power distribution data SPDR n,λ of said number n light unit based on said SPDC n,λ,t and the U n ; d) generating individual normalized spectral power distribution data SPDN n,λ of the number n light unit by normalizing said SPDR n,λ ; e) obtaining an individual white normalization factor W n of the number n light unit; f) repeating the steps of a) through e) for k light units of said first set of one or more light emitting units; and g) producing a high resolution spectrum H λ for said k light units by a process comprising the steps of: g1) generating a COG n of the number n light unit using the formula (i): COG n = ∑ λ = 380 760 ⁢ λ × SPDN n , λ ∑ λ = 380 760 ⁢ SPDN n , λ ; ( i ) g2) generating a specimen reflectance value L n unit using the formula (ii): L n =S n ×W n (ii); g3) generating a spectral optimization seed value T λ by interpolating said COG n and said L n ; g4) optionally, generating an initial medium resolution spectrum M λ based on the T λ ; g5) generating an initial high resolution spectrum H λ by interpolating from the spectral optimization seed value T λ , or optionally from the initial medium resolution spectrum M λ ; g6) calculating an estimated low resolution reflectance value E n at each COG n using the formula (iii): E n = ∑ λ = 380 760 ⁢ H λ × SPDN n , λ ; ( iii ) g7) calculating an error function Δ using the formula (iv): Δ = ∑ n = 1 k ⁢ ( E n - L n ) 2 ; ( iv ) g8) adjusting the spectral optimization seed value T λ to a subsequent T λ , or optionally adjusting the initial medium resolution spectrum M λ to a subsequent M λ , and repeating steps g5) through g7) using the subsequent T λ to replace the spectral optimization seed value T λ or using the subsequent M λ to replace the initial medium resolution spectrum M λ , if the error function Δ in step g7) is not converged; and g9) producing said high resolution spectrum H λ based on the spectral optimization seed value T λ or the subsequent T λ , or optionally, based on said initial medium resolution spectrum M λ or said subsequent M λ , when the error function Δ is converged; wherein: k is the number of the light emitting units measured; n is an index of the light emitting units and is in a range of from 1 to k; λ is a wavelength of lights in a range of from 380 nm to 760 nm.