Patent ID: 7548313

Claim:
A spectrograph comprising: a relay lens assembly having not more than a first and a second lens or lens assembly and further including a transmission grating, and a spectral filter assembly including a spectral filter, the first lens or lens assembly having positive optical power and collimating light from an input source; the transmission grating dispersing the collimated light from the first lens into different spectral components; the second lens or lens assembly having positive optical power and focusing the dispersed light from the transmission grating onto an optical detector; the spectral filter assembly located between the first lens and the transmission grating and mounted in an enclosed cylindrical structure with openings for admitting and transmitting light located on the faces of the cylindrical structure and removing the elastically scattered light from the input source and the spectral filter comprises an optical interference or absorption filter which attenuates the elastically scattered light wavelength; and the transmission grating being mounted to the spectral filter assembly as a single unit and comprising a plurality of opague, light-absorbing optical channel plates which limit the optical acceptance angle that can be transmitted through the spectral filter assembly; and an exit focal plane for the placement of at least one optical detector for measuring and converting the optical signals into electrical signals.