Hyperspectral prism-grating-prism imaging spectrograph

A new type of a direct vision dispersing component, the prism-grating-prism (PGP), was invented by the author in 1991. This patented component allows small, low-cost hyperspectral imaging spectrographs suitable for industrial and research applications in the wavelength range from 320 nm to 2700 nm, limited by the transmission of the grating material. The PGP spectrograph optics and the design procedure are described. The concept has been applied to many hyperspectral imaging spectrographs. The potential of the PGP construction is shown by introducing four designs in detail. 1) The prototype of a low-cost airborne hyperspectral imaging spectrograph, AISA, was the first application of the PGP concept. 2) A microscope imaging UV-VIS-NIR spectrometer system for spectral measurement of micrometersized objects such as wood fibers was developed. 3) A multiple-points PGP spectrograph connected to optical fibre probes was designed for industrial applications such as on-line colour and oil film thickness measurements. 4) The PGP spectrograph design for a high-speed interrogation system for large-scale fibre optic Bragg grating arrays is described. The PGP concept and the results of the developement work were so promising, that a company was founded in 1995 to commercialize, further develope and manufacture PGP spectrograph technology. Today PGP spectrographs are used world-wide for industrial machine vision and spectral analysis, airborne remote sensing and scientific applications in the form of standard products and customized OEM components.