Patent ID: 7733363

Claim:
A line head comprising: a lens array having a positive lens system in a first direction, the positive lens system having a pair of lenses with positive refractive power; a light emitter array disposed on an object side of the lens array and having a plurality of light emitting elements disposed corresponding to the positive lens system; and an aperture plate forming an aperture stop on the object side of the pair of lenses, wherein where f 1 denotes a focal distance of one of the pair of lenses disposed on the object side, the following conditional formula is satisfied: f 1 ≦d 0 /(1 +W 0 /D 1 ) where d 0 denotes a distance between the light emitter array and a front principal surface of the lens on the object side; W 0 denotes a distance between light emitting elements located at both ends of the plurality of light emitting elements disposed corresponding to the positive lens system in the first direction; and D 1 denotes an effective diameter of the lens on the object side.