A light source has a transparent substrate, a fixed substrate disposed in facing relation to the transparent substrate, at least one electron emitter disposed on the fixed substrate, a phosphor layer disposed on a surface of the transparent substrate which confronts the fixed substrate, and a trajectory deflector for deflecting the trajectory of a pulsed electron flow intermittently emitted from the electron emitter. The pulsed electron flow is deflected by the trajectory deflector to two-dimensionally scan a position of the phosphor layer which is irradiated with the pulsed electron flow for thereby spreading the pulsed electron flow.