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Compact large-area uniform colour-selectable calibration light source

Solid-state lighting and display technology are under rapid development. Photometric measurement devices such as imaging systems or tristimulus sensors encounter complex spatial, spectral and temporal conditions. Sufficiently large uniform calibration sources are required to adequately match the field application and to facilitate acceptable calibration uncertainties. We present a relatively compact, large-area uniform source employing plate diffusers and a patterned mask. The source is easily configured with colour-selectable, temperature-stabilized high power LED modules. We achieve 99% spatial uniformity within a 16 cm × 16 cm square field with Lambertian angular characteristics.