Exposure head and exposure apparatus
An exposure head, which is capable of sufficiently increasing pixel density without particularly decreasing the size of the light emitting elements of a planar light emitting element array, while being small in size itself. Linear light emitting element arrays are constituted by a plurality of light emitting elements, which are arranged in a main scanning direction at a predetermined pitch. A plurality of the linear light emitting element arrays are arranged in a sub scanning direction, which is substantially perpendicular to the main scanning direction, to constitute a planar light emitting element array. The sizes a and b of the light emitting elements in the main and sub scanning directions, respectively, and the arrangement pitches P 1 and P 2 in the main and sub scanning directions, respectively, satisfy the relationships P 1 ≦2a and P 2 ≦2b.
1 . An exposure head for exposing photosensitive material, comprising:
a plurality of linear light emitting element arrays, in each of which a plurality of light emitting elements are arranged in a main scanning direction at a predetermined pitch; and
a planar light emitting element array, comprising the plurality of linear light emitting element arrays, which are arranged in a sub scanning direction substantially perpendicular to the main scanning direction; wherein
the size a of each light emitting element in the main scanning direction and the pitch P 1 , at which they are arranged in the main scanning direction, satisfy the relationship:
P 1 ≦2a; and
the size b of each light emitting element in the sub scanning direction and the pitch P 2 , at which they are arranged in the sub scanning direction, satisfy the relationship:
P 2 ≦2b.
2 . An exposure head as defined in claim 1 , wherein:
the relationships:
a<b and P 1 =b are satisfied.
3 . An exposure head as defined in claim 1 , wherein:
at least a portion of the light emitting elements of adjacent linear light emitting element arrays are shifted and overlap in the main scanning direction.
4 . An exposure head as defined in claim 1 , wherein:
a plurality of the planar light emitting element arrays, each having light emitting elements that emit light at different spectrums, are employed; and
the plurality of planar light emitting element arrays are arranged in the sub scanning direction.
5 . An exposure head as defined in claim 4 , wherein:
the spectrums of light emitted from the light emitting elements of the planar light emitting element arrays are in the R (red), G (green), and B (blue) regions, respectively.
6 . An exposure head as defined in claim 1 , wherein:
the light emitting elements are organic EL elements.
7 . An exposure head as defined in claim 1 , further comprising:
a magnifying/focusing optical system, for focusing an image formed by the planar light emitting element array on the photosensitive material at 1× magnification.
8 . An exposure head as defined in claim 7 , wherein:
the magnifying/focusing optical system comprises a gradient index lens array.
9 . An exposure apparatus for exposing two dimensional images on photosensitive material, comprising:
an exposure head comprising a plurality of linear light emitting element arrays, in each of which a plurality of light emitting elements are arranged in a main scanning direction at a predetermined pitch; and a planar light emitting element array, comprising the plurality of linear light emitting element arrays, which are arranged in a sub scanning direction substantially perpendicular to the main scanning direction; wherein the size a of each light emitting element in the main scanning direction and the pitch P 1 , at which they are arranged in the main scanning direction, satisfy the relationship: P 1 ≦2a; and the size b of each light emitting element in the sub scanning direction and the pitch P 2 , at which they are arranged in the sub scanning direction, satisfy the relationship: P 2 ≦2b; and
a sub scanning means, for moving the exposure head and the photosensitive material relative to each the in the sub scanning direction.
10 . An exposure apparatus as defined in claim 9 , wherein:
the exposure head satisfies the relationships:
a<b and P 1 =b.
11 . An exposure apparatus as defined in claim 9 , wherein:
at least a portion of the light emitting elements of adjacent linear light emitting element arrays are shifted and overlap in the main scanning direction.
12 . An exposure apparatus as defined in claim 9 , wherein:
a plurality of the planar light emitting element arrays, each having light emitting elements that emit light at different spectrums, are employed; and
the plurality of planar light emitting element arrays are arranged in the sub scanning direction.
13 . An exposure apparatus as defined in claim 12 , wherein:
the spectrums of light emitted from the light emitting elements of the planar light emitting element arrays are in the R (red), G (green), and B (blue) regions, respectively.
14 . An exposure apparatus as defined in claim 9 , wherein:
the light emitting elements are organic EL elements.
15 . An exposure apparatus as defined in claim 9 , further comprising:
a magnifying/focusing optical system, for focusing an image formed by the planar light emitting element array on the photosensitive material at 1× magnification.
16 . An exposure apparatus as defined in claim 15 , wherein:
the magnifying/focusing optical system comprises a gradient index lens array.