Improved Image Sensor Calibration with Labsphere’s SpectrALL Tunable LED Uniform Light Sources

22 Oct 2020

Pro-Lite is pleased to announce the SpectrALL spectrally tunable LED uniform light sources from Labsphere.

Traditionally, image sensor and camera calibration has been performed using integrating sphere uniform light sources equipped with tungsten halogen incandescent lamps. Such lamps are very stable but do not match the spectrum of fluorescent lighting, LED solid state lighting or sunlight. This leads to the commonly seen effect whereby a camera image suffers from a distinct colour shift compared to how the object appears to the naked eye. Ideally, the spectrum of the light source used to calibrate an image sensor would match that of the illumination spectra encountered in real life. In other words, if you can precisely match the spectrum of sunlight with your reference source, you can then calibrate a camera so that it more faithfully records a true likeness of an object under sunlight illumination.

Labsphere’s solution is SpectrALL, a family of spectrally tunable LED-based uniform light sources. Building on decades of experience providing calibration sources for camera systems and other detectors, Labsphere have developed the Spectra-FT and Spectra-UT tunable sources to support the calibration of sensors where image fidelity is vitally important.

SpectrALL sources all employ integrating spheres which ensure that the source output is spectrally and spatially uniform. Every pixel on the image sensor sees the exact same luminance, colour temperature and spectrum, thereby providing a means for both colour correction of the sensor and also providing for pixel gain normalisation and flat field correction.

The Spectra-FT uses up to 84 LEDs to spectrally tune the light source output to a range of pre-set or user-defined spectra or colour temperatures. The spectral radiance is monitored with an embedded spectrometer which is accurately calibrated with the supplied tungsten halogen NIST traceable calibration lamp.

The Spectra-UT employs advanced polychromator technology to provide a near perfect spectral reproduction of almost any target spectrum in the visible light region using a sophisticated spectral matching algorithm. It can render narrow-band targets on the order of 10nm full-width half-max, broad VIS spectra and complex spectral shapes. As with the Spectra-FT, the Spectra-UT has an internal calibrated spectrometer for monitoring the spectral radiance that the system produces.

An external spectrometer accessory allows the operator to record the spectrum of light sources, displays or the light reflected from objects and then simulate them using the Spectra-UT LED light source. This allows the user to quickly and easily reproduce spectra when required giving unrivalled flexibility to calibration labs and production lines.

Want to know more? https://www.pro-lite.co.uk/File/light_sources.php