Patent ID: 7486021

Claim:
An electron tube comprising: an envelope formed with a photocathode at a predetermined part of the internal surface thereof; a fixing plate which is disposed in the envelope and which has a central position and an outer periphery surrounding the central position; an electron-bombarded semiconductor device which is fixed to the central position of the fixing plate and which faces the photocathode; a first tubular wall which is fixed to a position between the central position and the outer periphery of the fixing plate, the first tubular wall surrounding the semiconductor device and extending toward the photocathode; an evaporation source generating metal vapor, the evaporation source being disposed inside the envelope on the photocathode side relative to the fixing plate and being disposed at a position between the first tubular wall and an imaginary-extended-curved-surface of the outer periphery of the fixing plate that extends toward the photocathode, the semiconductor device detecting photoelectrons emitted from the photocathode in response to an incident light thereon; and a cover which is disposed at a position between the electron-bombarded semiconductor device and the photocathode, the cover being surrounded by the first tubular wall.