Abstract: A plastic optical element for an optical system of an optical scanner includes a plurality of optical effective portions through which a plurality of light beams transmit, respectively, formed on at least one of an incidence surface and an exit surface in a sub scan direction, and an optical ineffective portion formed between neighboring optical effective portions not to allow the light beams to transmit therethrough, and including an area in which a local contraction occurs at a time of resin molding.

Abstract: An optical element having an antireflection effect includes an incident plane and an emission plane and a conical microstructure formed on at least one plane of the incident plane and the emission plane. The conical microstructure includes a first structure formed of a plurality of conical microprojections with an average height H1 and a second structure formed of a plurality of conical microrecesses with an average height H2. The average height H1 satisfies an inequality H1?1/3*?/n and the average height H2 satisfies an inequality H2?1/3*?/n. An average pitch P between the first structure and the second structure satisfies following conditions: H1/2?P?1/3*?/n, and H2/2?P?1/3*?/n, in which the use wavelength is defined as ? and the refractive index relative to the use wavelength is n.

Abstract: A plastic optical element for an optical system of an optical scanner includes a plurality of optical effective portions through which a plurality of light beams transmit, respectively, formed on at least one of an incidence surface and an exit surface in a sub scan direction, and an optical ineffective portion formed between neighboring optical effective portions not to allow the light beams to transmit therethrough, and including an area in which a local contraction occurs at a time of resin molding.

Abstract: A plastic optical element for an optical system of an optical scanner includes a plurality of optical effective portions through which a plurality of light beams transmit, respectively, formed on at least one of an incidence surface and an exit surface in a sub scan direction, and an optical ineffective portion formed between neighboring optical effective portions not to allow the light beams to transmit therethrough, and including an area in which a local contraction occurs at a time of resin molding.

Abstract: An optical element using visible light from wavelengths ?S to ?L (?L>?S), is formed of a translucent material having refractive indexes nS and nL, respectively, for light having the wavelengths ?S and ?L. The optical element includes an incident face; an exit face; and a micro convexo-concave structure used as an anti-reflection structure (ARS), being formed at least one of the incident face and the exit face. An average distance P between adjacent micro convexo-concave structures satisfies condition (1) P?0.8·?S/nS. Dimensionless parameters mS and mL satisfy condition (2) 0.8?mS?1.1 and condition (3) 0.8?mL?1.1. The parameters mS and mL, an average height H, the wavelengths ?S and ?L, and the refractive indexes nS and nL of the micro convexo-concave structure satisfy condition (4) mS·?S/(2·nS)?H?mL·?L/(2·nL).

Abstract: An optical element having an antireflection effect includes an incident plane and an emission plane and a conical microstructure formed on at least one plane of the incident plane and the emission plane. The conical microstructure includes a first structure formed of a plurality of conical microprojections with an average height H1 and a second structure formed of a plurality of conical microrecesses with an average height H2. The average height H1 satisfies an inequality H1?1/3*?/n and the average height H2 satisfies an inequality H2?1/3*?/n. An average pitch P between the first structure and the second structure satisfies following conditions: H1/2?P?1/3*?/n, and H2/2?P?1/3*?/n, in which the use wavelength is defined as X and the refractive index relative to the use wavelength is n.

Abstract: An optical scanning device that scans a plurality of surfaces to be scanned in a main scanning direction by using a light beam includes: a plurality of light sources; a light deflector that deflects a plurality of light beams emitted from the light sources; and a scanning optical system that individually guides each one of the light beams deflected by the light deflector to a corresponding one of the surfaces to be scanned. The scanning optical system includes one scanning lens shared by the light beams, and at least one surface of the scanning lens has a plurality of optical surfaces corresponding to the plurality of light beams disposed in a sub-scanning direction with a flat surface provided between the optical surfaces.

Abstract: An optical element using visible light from wavelengths ?S to ?L (?L>?S), is formed of a translucent material having refractive indexes nS and nL, respectively, for light having the wavelengths ?S and ?L. The optical element includes an incident face; an exit face; and a micro convexo-concave structure used as an anti-reflection structure (ARS), being formed at least one of the incident face and the exit face. An average distance P between adjacent micro convexo-concave structures satisfies condition (1) P?0.8·?S/nS. Dimensionless parameters mS and mL satisfy condition (2) 0.8?mS?1.1 and condition (3) 0.8?mL?1.1. The parameters mS and mL, an average height H, the wavelengths ?S and ?L, and the refractive indexes nS and nL of the micro convexo-concave structure satisfy condition (4) mS·?S/(2·nS)?H?mL·?L/(2·nL).

Abstract: A plastic optical element for an optical system of an optical scanner includes a plurality of optical effective portions through which a plurality of light beams transmit, respectively, formed on at least one of an incidence surface and an exit surface in a sub scan direction, and an optical ineffective portion formed between neighboring optical effective portions not to allow the light beams to transmit therethrough, and including an area in which a local contraction occurs at a time of resin molding.

Abstract: An optical scanning device that scans a plurality of surfaces to be scanned in a main scanning direction by using a light beam includes: a plurality of light sources; a light deflector that deflects a plurality of light beams emitted from the light sources; and a scanning optical system that individually guides each one of the light beams deflected by the light deflector to a corresponding one of the surfaces to be scanned. The scanning optical system includes one scanning lens shared by the light beams, and at least one surface of the scanning lens has a plurality of optical surfaces corresponding to the plurality of light beams disposed in a sub-scanning direction with a flat surface provided between the optical surfaces.

Abstract: A resin casting mold includes a mold member forming a cavity that includes first and second surfaces facing each other in a first direction. The mold member further includes an insert member which forms a part of a third surface and which is slidable in a second direction perpendicular to the first direction. At least one cross-sectional shape of the cavity satisfies h<A<H, where “A” is the length of the insert member in the first direction, “h” is a spacing in the first direction between a portion of the first surface closest to the insert member and a portion of the second surface closet to the insert member, and “H” is the length in the first direction on the third surface. The insert member is disposed to include a region having the spacing “h”.