A Theoretical Analysis of the Operation of Flying Spot and Camera Tube Microscopes in the Ultraviolet

The minimum specimen exposure at television scanning rates required to yield pictures with acceptable signal-to-noise ratio and the best resolution optically attainable is computed for flying-spot, image-orthicon, and vidicon television microscopes for the ultraviolet. This exposure is found to be slightly less for the flying-spot microscope than for the image-orthicon microscope. For microscopes employing experimental ultraviolet-sensitive vidicons with optimal quantum efficiency, the exposure is greater than for the image-orthicon microscope by a factor of 2, and it may be greater by a factor up to 10 for vidicon microscopes with less favorable characteristics. Picture lag is absent in flying-spot microscopes and is not a serious consideration in image-orthicon microscopes, but may limit the permissible motion in the field of an ultraviolet vidicon microscope. On the other hand, the attainable radiance of flying-spot tube screens limits the usefulness of the flying-spot microscope in high-resolution studies, particularly when examination with sharply defined spectral bands is desired. No similar limitation exists for the image-orthicon and vidicon microscopes.