Spectroradiometer

Spectroradiometers are devices designed to measure the spectral power distribution of a source. From the spectral power distribution, the radiometric, photometric, and colorimetric quantities of light can be determined in order to measure, characterize, and calibrate light sources for various applications.

Spectroradiometers typically take measurements of spectral irradiance and spectral radiance. This spectral data can be used to calculate CIE tristimulus values through mathematical integration. CIE chromaticity coordinates and luminosity can then be calculated, providing a complete description of the source’s color, including chromaticity, spectral power, illuminance, and luminance. Spectroradiometers are stand-alone systems that work independently without the need to be connected to a PC. This makes them highly portable while maintaining the accuracy of a spectrometer.

The field of spectroradiometry concerns itself with the measurement of absolute radiometric quantities in narrow wavelength intervals. It is useful to sample the spectrum with narrow bandwidth and wavelength increments because many sources have line structures Most often in spectroradiometry, spectral irradiance is the desired measurement. In practice, the average spectral irradiance is measured, shown mathematically as the approximation:

Where ${\displaystyle E}$ is the spectral irradiance, ${\displaystyle \Phi }$ is the radiant flux of the source (SI unit: watt, W) within a wavelength interval ${\displaystyle \Delta \lambda }$ (SI unit: meter, m), incident on the surface area, ${\displaystyle A}$ (SI unit: square meter,m²). The SI unit for spectral irradiance is W/m³. However it is often more useful to measure area in terms of centimeters and wavelength in nanometers, thus submultiples of the SI units of spectral irradiance will be used, for example μW/cm²*nm

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