spectrometre

A spectrometre, or spectrometer, is a scientific instrument that measures the spectral properties of light. It disperses light into its constituent wavelengths and records the intensity at each wavelength, producing a spectrum that can be used to identify materials, determine concentrations, or study physical processes. The term covers a range of devices designed to analyze electromagnetic radiation from the ultraviolet through visible and infrared regions, and sometimes beyond.

A typical spectrometre comprises a light source or a sample in the light path, an entrance optical system with a slit, a collimator to produce a parallel beam, a dispersive element such as a prism or diffraction grating (in dispersive spectrometers) or an interferometer (in Fourier transform spectrometers), a focusing element, and a detector. Detectors may be photographic plates in older instruments, or modern charge-coupled devices (CCD), photomultiplier tubes, or arrays of photodiodes. Signal processing and data analysis convert detected signals into a spectrum, often with wavelength calibration and intensity calibration.

Spectrometers are classified by how they separate wavelengths and by their mode of operation. Dispersive spectrometers rely on prisms or gratings to spread light, while interferometric instruments use interference patterns to derive spectra, as in Fourier transform spectroscopy. Applications span chemistry, physics, astronomy, environmental monitoring, materials science, and life sciences, including absorption, emission, fluorescence, and reflectance measurements.

Key performance parameters include spectral range, spectral resolution, wavelength accuracy, sensitivity, and signal-to-noise ratio. Calibration against known standards and correction for instrumental artifacts are essential for quantitative work.