III. Measurement of Light with integral detectors

Spectroradiometry - the measurement of radiation intensity as a function of wavelength - is the only way to provide full spectral information about optical radiation emitted by a light source or impinging upon a surface. Obtaining this information has its price: Spectroradiometers are highly sophisticated optical measurement devices and in general, their proper calibration, operation and maintenance is rather time consuming. However, for the vast majority of applications, integral detectors (the term Nintegrali describes the fact that the output signal of an integral detector is proportional to the wavelength integral over the measured quantity's spectral distribution, multiplied with the detector's spectral sensitivity (see III.2)) offer an economical and user friendly alternative: In most cases, it is not necessary to determine the exact spectral distribution of the measured quantity, and it is sufficient to use a detector especially designed to match a certain predefined spectral sensitivity function. As an example, the spectral sensitivity of photometric detectors is matched to the CIE spectral luminous sensitivity function V(I), and detectors for solar UV irradiance potentially harmful to the human skin are matched to the CIE erythema action spectrum.

As integral detectors provide just a single output signal (usually voltage or photocurrent), they are much easier to characterize than spectroradiometers. The main parameters determining the usability and the quality of an integral detector are

  • The detector's input optics, which determines its directional sensitivity
  • The detector's spectral sensitivity
  • The dynamic range, over which the detector's output is proportional to the input signal's intensity
  • The detector's time behaviour

Refer to III.5. for more info about calibration laboratory. More information is also available about our Calibration Services and Calibration Standards as well as Uniform Light Source Calibration Standards.


Download our Tutorials On Light Measurement. Size: 3 MB