Electron-optical image tubes

An electron-optical image tube system comprising a photocathode for receiving light images and converting them to photoelectrons, an extraction electrode at the emission side of the photocathode that generates a strong electric field and accelerates the photoelectrons away from the photocathode and projects these photoelectrons into a path on the output side of the extraction electrode at increased velocity, deflection electrode means on the path of the photoelectrons beyond the extraction electrode, means defining an aperture beyond said deflection electrode means on which photoelectrons received directly from the extraction electrode impinge, control means operable to scan the photoelectron image across the aperture, and pick-up means on the side of the aperture remote from the electrodes to receive photoelectrons passing through the aperture, a source of ultra-short light pulses, means providing an image of said pulses at the photocathode, voltage generating means connected to said deflection electrode means and providing voltages thereto, phase control means controlling the phase of the voltages applied to said deflection electrode means to produce a circular or spiral deflection path on said means defining said aperture, and adjustable optical delay means in the path of the light pulses to the photocathode.