Patent ID: 8736896

Claim:
An optical scanning unit, comprising: a light source including a plurality of light-emitting elements; a light detector to detect a light beam emitted from the light source; a light-flux splitter disposed at an angle to the optical axis of the light beam emitted from the light source, having an aperture, a portion of reduced thickness susceptible to warping, a concave face of the warped light-flux splitter as a reflecting face, and a convex face of the warped light-flux splitter opposite the concave face as a non-reflecting face; a light-flux splitter holding member to hold the light-flux splitter thereon; and a light-flux splitter pressing unit to press the light-flux splitter held on the light-flux splitter holding member without blocking the aperture of the light-flux splitter, wherein a portion of light beam emitted from the light source passes through the aperture of the light-flux splitter as a write-use light flux for forming an electrostatic latent image on an image bearing member, the reflecting face of the light-flux splitter faces the light source in an optical path of the light beam emitted from the light source, the reflecting face of light-flux splitter reflects a light flux other than the write-use light flux as a monitor-use light flux for adjusting a light intensity of the light source, the monitor-use light flux being guided to the light detector, the light-flux splitter pressing unit presses a portion of maximum convexity of the non-reflecting face of the light-flux splitter held on the light-flux splitter holding member.