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Characterization of narrow-band near-IR diodes arranged in array patterns

We examined old, not-well documented paintings before the process of restoration was started, to look for the presence of any invisible signatures and dates, as well as original line drawings and possible painted-over or hidden images. We connected IR LEDs in two-dimensional arrays to allow us to sample the surface of the artwork with approximately uniform illumination, but at different peak wavelengths. We describe the extended area infrared LED illumination sources as to their geometrical arrangement, and their resulting spectral, spatial, and power output characteristics. With these light sources, we were able to make invisible information available for review and critical assessment by the art historians.