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30 January 2003 The Dittoscope
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Abstract
If a collector is very large - square kilometers in size - it may be easier to fabricate flat optics than curved optics. If the primary objective is a flat diffraction grating, microscopic grooves would reshape the incident wave front rather than the 3D surface of a conventional parabolic reflector. I discuss diffractive optics that potentially can cover areas of square kilometers. The geometry of grazing incidence and evanescence allows for very large grating surfaces in ribbons or aggregated segmented modules. Diffraction grating primaries are attractive in that they are well suited for spectrographic astronomy, particularly the Doppler shift studies that have recently been useful in extra-solar planet detection. I propose a unique static mount for ground-based observations where the only moving part is the earth itself. For space-based installations, a new type of membrane telescope is disclosed that can be orbited as a roll of plastic and unfurled over multiple kilometer lengths. Holographic gratings are capable of very fine angular resolution, and only their extreme chromatic dispersion has inhibited their use. The bug is a feature. When taking spectra, chromatic dispersion is useful.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Thomas Ditto "The Dittoscope", Proc. SPIE 4840, Future Giant Telescopes, (30 January 2003); https://doi.org/10.1117/12.459878
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