The remote VIS/NIR hyperspectral imaging system operating over the spectral range 400-1000 nm with a spectral resolution of 2.8 nm consists of a spectrograph, a CMOS camera and a telescope. It collects spectra for one spatial line at a time in a pushbroom fashion using an automated pan/tilt stage. A Tungsten light with long range projection capability is used for indoor imaging or imaging at night. For outdoor imaging, daylight is sufficient. The system is placed on a computer controlled motorised pan/tilt stage that allows for convenient imaging of any areas of a monument or object from one position on the ground. The system has an operational range up to tens of metres. It is used for detailed hyperspectral imaging at targeted areas remotely at large distances and at inaccessible height with submm spatial resolution and high spectral resolution.
The main advantage of remote reflectance hyperspectral imaging is the ability to access large monuments or objects at inaccessible height from the ground level without the need for scaffolds. It is particularly suitable to architectural and archaeological sites. The specific advantage of remote reflectance hyperspectral imaging compared with the remote spectral imaging system for large areas survey (PRISMS) is the high spectral resolution which allows the for firm identification of a handful of pigments and dyes with sharp spectral features (e.g. cobalt pigments, anthraquinone dyes) in addition to those identifiable by the moderate spectral resolution spectral imaging system (PRISMS) for targeted areas. It can give RGB true colour images and images through any of the spectral channels and more importantly separating areas of different material composition. It can give material identification (both original and degraded material) to be confirmed with complementary techniques such as remote Raman spectroscopy and if appropriate remote LIBS spectroscopy. The images can also reveal faded drawings, writings and preparatory sketches, as well as areas of degradation and past intervention.