[irradiance, irradianceS] =…
WattsToRetIrradiance(relativeSpectrum, relativeSpectrumS, readingInWatts, [radiometer])

The assumption underlying this routine is that the relative spectrum of a light
is available, as well as the total power of the light passing through an aperture
of known size. This is the situation in the apparatus we use in Sterling’s lab.
The routine computes the irradiance (watts/um^2-wlinterval) from the relative spectrum
(relative power, not relative quanta) and a measurement of the total power in watts,
given the radiometer properties specified.

Radiometers do not typically have an ideal flat spectral response, and the actual
spectral response is often provided as part of the instrument calibration. In addition,
the instruments are typically calibrated to provide an accurate reading for one
particular reference spectrum, which is also specified. This routine is set up
to use this calibration information together with the known relative spectrum to
provide a correct result. The radiometer properties may be passed in the radiometer
structure. A default structure is set up that describes the radiometer used in
the Sterling lab. This structure also describes the collecting area of the measurement

This routine could be easily modified to deal with a photometric head.

Input variables: relativeSpectrum is the relative power as a function of wavelength.
relativeSpectrumS is the wavelength sampling information for the relativeSpectrum.
readingInWatts is the total power measured.
radiometer is a structure describing the radiometer. (default = Sterling Lab’s IL1400A).

04/29/03 lyin Wrote it with advice from DHB
05/06/03 lyin Put wls into variable: lightSource
05/06/03 lyin Correction for wavelength sampling interval
06/12/03 lyin Change the way, variable being passed
6/26/03 dhb Change some names, also compute power per wavelength interval, not per nm.
6/30/03 dhb Lots more changes.
7/08/03 dhb Monochromatic ref spectrum default, as per manual.

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