Patent ID: 7196723

Claim:
A streak apparatus comprising: a streak tube having: a vacuum container which has, at one end thereof, a photocathode for converting a received light beam into photoelectrons and, at the other end thereof, an output surface for converting an image formed by the photoelectrons into a visible optical image, an accelerating electrode arranged to oppose said photocathode along a tube axis of said vacuum container and to accelerate the photoelectrons emitted from said photocathode, a deflecting electrode formed of a pair of electrodes opposing each other between said accelerating electrode and said output surface to sandwich the tube axis, and a plurality of focusing magnetic flux generators for generating a focusing magnetic flux between said photocathode and an incident port of said deflecting electrode to focus the photoelectrons emitted from said photocathode; a deflecting voltage generation circuit for supplying a voltage to said deflecting electrode so as to generate a deflecting electric field; an acceleration voltage generation circuit for supplying a voltage to said accelerating electrode; and a drive power supply for supplying a current to said focusing magnetic flux generators, wherein, said plurality of focusing magnetic flux generators form a main focusing electron lens for forming an electron image, formed on said photocathode, on said output surface, a prefocus lens arranged between said photocathode and said main focusing electron lens to focus the photoelectrons, emitted from said photocathode, toward a center of said main focusing electron lens; and said prefocus lens surrounds the tube axis.