Abstract: In an exposure device, a light source device having multiple light emitting devices arranged in one-dimensional or two-dimensional directions projects light against an image bearing member. A light source holding member holds the light source device in place. An optical device condenses the light projected from the light source device onto the image bearing member. An optical device holding member holds the optical device to maintain a predetermined gap between the optical device and the light source device on the light source holding member. A positioning member supports the light source holding member above the image bearing member to maintain a predetermined gap between the image bearing member and the light source device on the light source holding member. When seen from a light emitting point of the light source device, a position at which the positioning member supports the light source holding member is opposite the image bearing member.

Abstract: In the optical deflector, the mean width of profile elements of a cross section of the deflection surface in the sub scan direction is set to be less than the spacing between spots of the light beams formed in the sub scan direction of the deflection surface. This makes it possible to prevent a variation in the size and shape of the spots of the light beams deflected by the deflection surface due to the undulation (unevenness) of the deflection surface. As a result, it is able to suppress a decrease of the granularity of images and form images with high quality.

Abstract: A hydrodynamic bearing unit using oil includes a shaft to be driven, a bearing member configured to support the shaft in a non-contact manner through a bearing gap by a hydrodynamic pressure of the oil, which is generated in the bearing gap while the shaft relatively rotate with respect to the bearing member, a housing configured to house the bearing member and having an opening at one end thereof, another end thereof being enclosed, a sealing member configured to seal a part of the opening of the housing, a channel configured to communicate a space formed between the shaft, the bearing member and the housing with an outside air, and a pressing member configured to press and fix the bearing member on the housing. At least one open part configured to release an air bubble contained in the housing is provided between the bearing member and the sealing member.

Abstract: An optical scanning device includes an optical housing in which a polygon mirror that is rotated by a motor is accommodated and an air inlet that includes a filter. An airflow guiding member is arranged at a position opposite to a surface of the polygon mirror on the air inlet side. An air inducing path is provided, which includes a first flowing path and a second flowing path. The first flowing path includes a first end linked to the air inlet and a second end arranged close to a mirror surface of the polygon mirror. The second flowing path is formed with a surface of the airflow guiding member on an opposite side of the air inlet and a top surface of the polygon mirror.

Abstract: A rotary drive apparatus includes a rotary body with a support portion, a rotor magnet supported by the support portion of the rotary body, a fixation section facing the rotor magnet and rotatably supporting the rotary body, and a winding coil provided in the fixation section, in which an expression E1/E2?0.75 is satisfied where Young's modulus of the rotor magnet is E1 [GPa], and Young's modulus of the support portion is E2 [GPa].

Abstract: An optical deflector includes a rotary body including a polygon mirror; a rotation shaft fixed to the rotary body; a bearing unit rotatably supporting the rotation shaft; and a board to which the bearing unit is fixed. Where P [rpm] is the number of revolutions of the rotary body, l [m] is a distance between a center of gravity of the rotary body and the board, m [kg] is mass of the rotary body, r [m] is a radius of the rotation shaft, E [Pa] is Young's modulus of the rotation shaft, and t [mm] is a thickness of the board, the following inequalities are satisfied: 1 2 ? ? ? ? ? 3 ? ? ? ? Er 4 4 ? ? ml 3 ? 2 × P 60 ? ? and ? ? 0.8 ? t ? 1.8 .

Abstract: An optical deflector includes a rotary body including a polygon mirror; a rotation shaft fixed to the rotary body; a bearing unit rotatably supporting the rotation shaft; and a board to which the bearing unit is fixed. Where P [rpm] is the number of revolutions of the rotary body, l [m] is a distance between a center of gravity of the rotary body and the board, m [kg] is mass of the rotary body, r [m] is a radius of the rotation shaft, E [Pa] is Young's modulus of the rotation shaft, and t [mm] is a thickness of the board, the following inequalities are satisfied: 1 2 ? ? ? 3 ? ? ? ? Er 4 4 ? ml 3 ? 2 × P 60 and 0.8 ? t ? 1.8 .

Abstract: A hydrodynamic bearing unit using oil includes a shaft to be driven, a bearing member configured to support the shaft in a non-contact manner through a bearing gap by a hydrodynamic pressure of the oil, which is generated in the bearing gap while the shaft relatively rotate with respect to the bearing member, a housing configured to house the bearing member and having an opening at one end thereof, another end thereof being enclosed, a sealing member configured to seal a part of the opening of the housing, a channel configured to communicate a space formed between the shaft, the bearing member and the housing with an outside air, and a pressing member configured to press and fix the bearing member on the housing. At least one open part configured to release an air bubble contained in the housing is provided between the bearing member and the sealing member.

Abstract: A light-amount detecting device includes: a light source which emits a light beam; a branching optical element which divides the light beam emitted from the light source into a first light beam traveling in a predetermined direction and a second light beam traveling in a direction different to the predetermined direction; a light-condensing element which condenses the second light beam; a light-receiving element having a light-receiving surface which receives the second light beam condensed by the light-condensing element; and a detector which detects a light-amount of the second light beam received by the light-receiving element, and at least one of a direction of reflected light of the second light beam reflected from the light-receiving surface of the light-receiving element and spread of the reflected light of the second light beam reflected from the light-receiving surface of the light-receiving element is adjusted to control a light-amount of the reflected light of the second light beam returning to the

Abstract: A rotary drive apparatus includes a rotary body with a support portion, a rotor magnet supported by the support portion of the rotary body, a fixation section facing the rotor magnet and rotatably supporting the rotary body, and a winding coil provided in the fixation section, in which an expression E1/E2?0.75 is satisfied where Young's modulus of the rotor magnet is E1 [GPa], and Young's modulus of the support portion is E2 [GPa].

Abstract: In the optical deflector, the mean width of profile elements of a cross section of the deflection surface in the sub scan direction is set to be less than to spacing between spots of the light beams formed in the sub scan direction of the deflection surface. This makes it possible to prevent a variation in the size and shape of the spots of the light beams deflected by the deflection surface due to the undulation (unevenness) of the deflection surface. As a result, it is able to suppress a decrease of the granularity of images and form images with high quality.