Patent ID: 6888559

Claim:
A laser beam scanner for forming a scanning line along a main-scanning direction with a laser beam, comprising: a laser diode that emits the laser beam; a first converging unit that converges the laser beam in a main-scanning direction; a second converging unit that converges the laser beam, that has been converged by the first converging unit, in a sub-scanning direction substantially perpendicular to the main-scanning direction; a scan start time determination unit that detects, within a predetermined detection area, the laser beam that has been converged by the first converging unit before being converged by the second converging unit, and determines a scan start time upon the detection of the laser beam; a photosensitive medium on which a scanning line is formed along the main-scanning direction; a scan controller that controls a start of, at the determined scan start time, scanning the photosensitive medium with the laser beam that has been converged by the first converging unit and the second converging unit; a first deflector that deflects the laser beam emitted by the laser diode to the first converging unit; and a third converging unit that converges, in the sub-scanning direction, the laser beam that has been converged by the first converging unit and traveling to the scan start time determination unit, so that the laser beam falls within the predetermined detection area of the scan start time determination unit, wherein a first traveling distance of the laser beam along an optical axis between the first deflector and the scan start time determination unit is greater than or equal to four times a focal length of the third converging unit.