Claims
- 1. A scanning lens comprising a single f.theta. lens for scanning a scanned surface with a convergent luminous flux from a point of deflection, wherein a first surface and a second surface of the single f.theta. lens are both aspherical and wherein the following conditions are fulfilled: ##EQU18## where r.sub.1 is a paraxial radius of curvature of the first surface, r.sub.2 is a paraxial radius of curvature of the second surface, a.sub.ymax is a distance between a position of the point of deflection and a position at which a luminous flux passing an upper limit of an effective height of the lens passes through the first surface which distance is measured parallel to the optical axis, a' is a distance between the position of the point of deflection and a position at which a luminous flux passing the upper limit of the effective height of the lens passes through a spherical surface extending from a position of an optical axis on the first surface with a paraxial radius of curvature r.sub.1, G is a distance between the point of deflection and an image surface, a is a distance between the point of deflection and the first surface, t is a thickness of a center of the lens, L is a width of scanning, and f is a focal length.
- 2. A scanning lens as claimed in claim 1, wherein the following condition is further fulfilled: ##EQU19##
- 3. A scanning lens as claimed in claim 1, wherein the following condition is further fulfilled: ##EQU20## where 2.multidot.y.sub.max is a length of the scanning lens in a main scanning direction.
- 4. A scanning lens as claimed in claim 1, wherein said scanning lens has a surface such that a radius of curvature in a main scanning direction is an aspherical surface and that a radius of curvature in a sub scanning direction continuously varies with a displacement in the main scanning direction.
- 5. A scanning lens as claimed in claim 1, wherein said scanning lens is made of a resin.
- 6. A scanning lens as claimed in claim 1, wherein a configuration of the scanning lens has only one point of inflection.
Priority Claims (3)
Number |
Date |
Country |
Kind |
5-214311 |
Aug 1993 |
JPX |
|
5-322556 |
Dec 1993 |
JPX |
|
6-101102 |
May 1994 |
JPX |
|
Parent Case Info
This is a division of prior application Ser. No. 08/620,103, filed on Mar. 21, 1996, U.S. Pat. No. 5,721,631 , which is a division of U.S. Ser. No. 08/296,020, filed on Aug. 25, 1994, and issued as U.S. Pat. No. 5,563,729 on Oct. 8, 1996.
US Referenced Citations (9)
Foreign Referenced Citations (2)
Number |
Date |
Country |
62-139520 |
Jun 1987 |
JPX |
63-157122 |
Jun 1988 |
JPX |
Divisions (2)
|
Number |
Date |
Country |
Parent |
620103 |
Mar 1996 |
|
Parent |
296020 |
Aug 1994 |
|