| 摘要 |
PROBLEM TO BE SOLVED: To provide an image writing device which is reduced in size on the whole and can perform a high-precision synchronous detection by arranging a beam detection sensor at a desired position. SOLUTION: A BTL (barrel toroidal lens) 6A which is scanned with the incident beam from a laser diode corresponding to image data through an fθlens after the beam is converged by a cylinder lens and deflected by a polygon mirror, is provided with a detection light deflection part 12 having a refractive index discontinuous from an image write area W at the peripheral part outside an image write area W. The detection light deflection part 12 deflects a part of the laser beam from the laser diode to a specific direction and the beam is photodetected by a beam position detection sensor 9 which is reduced in size on the whole and arranged at a deflection position, and the high-precision synchronous detection is performed at the beam position in the horizontal scanning direction and the beam in the image write area W is reflected by a mirror 7 to precisely perform the write scanning of an image to an image carrier.
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