Patent
1989-12-08
1991-07-16
Arnold, Bruce Y.
350 67, 350433, 350434, G02B 2608, G02B 304
Patent
active
050319795
ABSTRACT:
In an f .theta. lens system in an optical scanner, a light beam from a light source is formed as a line image extending in a main scanning corresponding direction and is deflected at an equal angular velocity by a rotary polygon mirror having a reflecting face in the vicinity of an image forming position of the line image. The f .theta. lens system focuses and forms the light beam deflected by the rotary polygon mirror as an image on the scanned face and comprises a functional device having a function for connecting a reflecting position of the rotary polygon mirror and the scanned face in an approximately conjugate relation with respect to a secondary scanning direction, and an f .theta. function for moving the deflected scanning light beam on a scanned medium face at an approximately equal speed with respect to a main scanning direction; and two groups of first and second lenses sequentially arranged from the side of the rotary polygon mirror toward the scanned face side. A lateral magnification of the formed image on the scanned face with respect to the linear image in the secondary scanning direction is provided in a range of -9.15 to -2.20. The lenses have first to fourth lens faces having shapes on a deflecting plane respectively composed of a straight line, an arc, an arc and an arc. The first and second lenses have a positive refracting power on a plane parallel to the deflecting plane.
REFERENCES:
patent: 4836630 (1989-06-01), Takanashi
patent: 4919502 (1990-04-01), Yamakawa
Arnold Bruce Y.
Phan James
Ricoh & Company, Ltd.
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