Inner drum exposure apparatus
The inner drum exposure apparatus records an image by scanning a recording material held on an arcuate inner peripheral surface of a support with a circularly polarized light beam that is emitted from a light source and modulated in accordance with image information and deflected by a total internal reflection mirror plane of a rotatably driven scanning device such as a spinner. The image is record on the recording material by scanning the recording material with the modulated light beam using the scanning unit. The scanning unit further includes an optical member having on its surface a polarizing beam splitter plane spaced apart from the mirror plane by a predetermined distance. Two beam spots formed on the recording material by two parallel beams obtained by the polarizing beam splitter plane and the mirror plane are combined into a synthetic beam spot in which the beam spots are disposed side by side in a sub scanning direction so as to overlap each other.
1 . An inner drum exposure apparatus, comprising:
a support having an arcuate inner peripheral surface on which a recording material on which an image is record is held;
a light source which emits circularly polarized light as a light beam;
modulating means which modulates in accordance with image information of said image said light beam emitted from said light source; and
scanning means which is rotatably driven, has a total internal reflection mirror plane, and scans said recording material held on said arcuate inner peripheral surface of said support with said light beam that is modulated in accordance with said image information by said modulating means and deflected by said total internal reflection mirror plane of said rotatably driven scanning means, wherein
said image is record on said recording material by scanning said recording material with said modulated light beam using said scanning means,
said scanning means further comprises an optical member having on its surface a polarizing beam splitter plane which is spaced apart from said total internal reflection mirror plane by a predetermined distance, and
two beam spots respectively formed on said recording material by two parallel beams that were obtained by said polarizing beam splitter plane and said total internal reflection mirror plane are combined into a synthetic beam spot in which said two beam spots are disposed side by side in a sub scanning direction so as to overlap each other.
2 . The inner drum exposure apparatus according to claim 1 , wherein said predetermined distance between said polarizing beam splitter plane and said total internal reflection mirror plane approximates to a half-width of said light beam.
3 . The inner drum exposure apparatus according to claim 1 , wherein said polarizing beam splitter plane has optical properties according to which a P-polarized component of said light beam is substantially transmitted through said polarizing beam splitter plane but an S-polarized component of said light beam is substantially reflected therefrom.
4 . The inner drum exposure apparatus according to claim 1 , wherein said optical member is a thin film formed on said total internal reflection mirror plane by a thin film forming technique, said polarizing beam splitter plane is a surface of said thin film formed on said total internal reflection mirror plane by said thin film forming technique.
5 . The inner drum exposure apparatus according to claim 1 , wherein said optical member includes a transparent support member formed on said total internal reflection mirror plane and a thin film formed on said transparent support member by a thin film forming technique, and said polarizing beam splitter plane is a surface of said thin film formed by said thin film forming technique on said transparent support member, which in turn is formed on said total internal reflection mirror plane.
6 . The inner drum exposure apparatus according to claim 1 , wherein said scanning means further includes a support block having said total internal reflection mirror plane formed thereon and a balance adjusting member which is provided on said polarizing beam splitter plane, is substantially identical in weight with said support block, and is made of a transparent material.
7 . The inner drum exposure apparatus according to claim 1 , wherein an anti-reflection layer is formed on said polarizing beam splitter plane.