Spektroradiometer

A spektroradiometer, or spectroradiometer, is an instrument designed to measure the spectral power distribution of light or radiant flux as a function of wavelength. It provides measurements of spectral irradiance or spectral radiance, allowing the characterization of light sources, scenes, or materials in terms of how their output varies across wavelengths.

The basic principle combines dispersion and detection: light is collected and directed through an entrance optic and often an integrating sphere or diffuser, then dispersed by a grating or prism. The dispersed light is detected by a photodetector array or a scanning detector, producing a signal that is converted into units of power per wavelength (such as W/m^2/nm) or radiance. Wavelength calibration, spectral responsivity, and radiometric calibration are essential to convert raw counts into physical units. Many systems include a reference detector and a calibration standard to maintain accuracy. Typical spectral resolutions range from a few tenths of a nanometer to several nanometers, depending on the instrument and configuration.

Configurations vary: bench-top devices with fixed slits, portable or handheld models, and imaging spectroradiometers that provide spatially resolved spectra. Accessories such as cosine correctors, integrating spheres, and fiber optics extend measurement capabilities to hemispherical, diffuse, or remote sensing geometries.

Applications include characterization of light sources (LEDs, lamps), measurement of solar spectral irradiance, color science and photometry, material reflectance and transmittance studies, and calibration/validation in remote sensing and plant growth research. Calibration against recognized radiometric standards ensures accuracy and traceability.