Patent
1989-12-21
1991-05-14
Dzierzynski, Paul M.
350433, 350434, 350 67, G02B 2608, G02B 304
Patent
active
050150502
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 and is then formed by an image forming lens system in the shape of a spot on a scanned face to optically scan the scanned face. The f.theta. lens system focuses and forms the light beam deflected by the rotary polygon mirror as an image on the scanned face. The f.theta. lens system comprises a functional device having a function for connecting a reflecting position of the rotarty polygon mirror and the scanned face in an approximately conjugate relation in geometrical optics in a secondary scanning direction, and comprises an f.theta. function in a main scanning direction, and has two groups of first and second lenses sequentially arranged from the side of the rotary polygon mirror toward the scanned face side. The lenses have first to fourth lens faces provided from the side of the rotary polygon mirror and having shapes on a deflecting plane composed of a combination of an arc and a straight line from the first to fourth lens faces. The first and second lenses may have respective refracting powers on a plane parallel to the deflecting plane.
REFERENCES:
patent: 4447112 (1984-05-01), Matsuoka et al.
patent: 4756584 (1988-07-01), Takanashi
patent: 4836630 (1989-06-01), Takanashi
patent: 4846539 (1989-07-01), Takahashi et al.
patent: 4919502 (1990-04-01), Yamakawa
Dzierzynski Paul M.
Phan James
Ricoh & Company, Ltd.
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