oiCalculateIlluminance

 Calculate illuminance (lux) of optical image spectral irradiance.

  [illuminance,meanIlluminance] = oiCalculateIlluminance(opticalImage)  

 The optical image spectral irradiance data are converted into
 illuminance (Lux) using the CIE formula.

 Suppose the spectral irradiance is irradianceE (watts/m2) and sampled
 at various wavelength values (nm); vLambda is the photopic sensitivity
 function sampled at the same set of wavelengths; suppose the wavelength
 spacing is binwidth (nm). Then the formula for illuminance in units of
 lux is

       illuminance = (683*binwidth)* irradianceE * vLambda;

 The mean illuminance can also be computed and returned.

Examples:

  illuminance = oiCalculateIlluminance(oi);
  oi = oiSet(oi,'illuminance',illuminance);

 Copyright ImagEval Consultants, LLC, 2003.