A streak camera having improved time resolving capacity in the femtosecond regime. The streak camera uses magnetic and/or electric fields in such a way as to minimize the adverse effects of angular distribution and energy distribution of photoelectrons simultaneously emitted from a photocathode in response to the impinging of light thereon. In one embodiment, the streak camera comprises a streak camera tube including a housing, the housing having disposed therein a photocathode (33), an aperture (35) sized to selectively permit the passage therethrough of substantially on-axis photoelectrons, an accelerating mesh (37), a pair of focusing electrodes (39), or a cylindrical focusing electrode for focusing the photoelectrons into a beam, a pair of isolation plates or an isolation cylindrical (11), means for creating an electric field and/or a magnetic field, (43) whereby the beam of photoelectrons passing therethrough is caused to be dispersed into a plurality of trajectories in accordance with the distribution of velocities of the photoelectrons, an aperture (45) sized to selectively permit the passage therethrough of photoelectrons traveling along a narrow band of trajectories, i.e. photoelectrons within a narrow velocity range, a pair of sweep electrodes (47), a microchannel plate (55), and a phosphor screen (57). The streak camera also includes an input slit (27) disposed in front of the photocathode and optics for imaging the input slit on the photocathode. To minimize dispersion of the optical pulse as it is focused onto the photocathode, the optics preferably include a mirror arrangement instead of a lens system.
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