As well as a possible cost reduction, certain improvements in signal recovery and in instrument rigidity may be achieved if the two images, with oppositely oriented dispersion directions, are imaged side-by-side on one detector.
The new design has been carried out by Damien Jones of Prime Optics during 1997 and will be presented at a consortium meeting on November 20.
The gratings work near Littrow condition (split, as in PNS-1 but with zero angle between the incident and emerging beams) and tilted in the non-dispersive direction so as to move the beams to one side.
This approach ran into the problem that field distortion causes the two images to overlap somewhat at the detector rather than sitting nicely side-by-side. It can be avoided by making the angle of tilt no more than 7 degrees but this was not possible in the present design.
Prime Optics is based in Eumundi, Queensland, Australia: tel +61(07)5442 8831, fax +61(07)5442 8804