Patent ID: 8577639

Claim:
A calibration assembly for a spectrometer, the assembly comprising: a spectrometer having first through one hundredth detector elements, each of the first through one hundredth detector elements being assigned predetermined respective wavelength values (λ 1 , λ 2 , . . . λ 100 ); a first source emitting a first radiation for calibrating the spectrometer; a device placed in the path of the first radiation to split the first radiation into a first beam and a second beam; wherein one of the first and second beams travels a path-difference distance (d) longer than the other of the first and second beams; wherein the spectrometer is configured to generate an actual output signal when the first beam and the second beam enter the spectrometer; a controller operable for processing the actual output signal; wherein the controller is adapted to calculate respective correction factors for the respective wavelength values by comparing the actual output signal with a theoretically-predicted output signal; a first blocking device to selectively block the first beam and a second blocking device to selectively block the second beam; wherein the spectrometer is configured to generate a reference signal when the first beam is selectively blocked and the second beam enters the spectrometer; wherein the spectrometer is configured to generate a dark signal when the first beam and the second beam are selectively blocked from entering the spectrometer; an algorithm stored on and executable by the controller to cause the controller to; determine a dark-corrected reference signal by subtracting the dark signal from the reference signal; determine a dark-corrected output signal by subtracting the dark signal from the output signal; determine an actual normalized output by dividing the dark-corrected output signal by the dark-corrected reference signal; correlate the actual normalized output with a correlation function to determine a first function, the correlation function and the first function having a variable parameter z; determine a first-approximation for the path-difference distance (d) occurring at a maximum value for the first function; add an integration correction factor to the first function to obtain a second function; and determine the path-difference distance between the first beam and the second beam, the path-difference distance occurring at a maximum value for the second function; wherein the correlation function is represented by an array [(cos(2πz/λ 1 ))/λ 1 , (cos (2πz/λ 2 ))/λ 2 , . . . , cos(2πz/λ 100 ))/λ 100 ,]; and wherein the first function is approximated by an expression {Σ i=1 to 100 [(1+cos (2πd/λ i ))] cos(2πz/λ i )(Δλ i /λ i )}, such that Δλ i is a spacing between respective wavelengths.