F-θ lens

Claim 2

An f-θ lens, said lens being adapted to receive an input beam which comprises a combination of beams each of which is at a predetermined wavelength and has a predetermined vergence in a scan direction, said lens comprising: means for correcting in a scan direction for lateral color aberrations of said beams at a receiving medium; and means for correcting in a scan direction for axial color aberrations of said beams at the receiving medium when at least one of said beams has a non-zero vergence.

Claim 3

An f-θ lens, as defined in claim 1, wherein each of said beams has a wavelength in the infrared.

Claim 4

An f-θ lens, as defined in claim 2, wherein said input beam is a combination of one beam having a wavelength of about 750 nm, a second beam having a wavelength of about 810 nm, and a third beam having a wavelength of about 870 nm.

Claim 5

An f-θ lens, as defined in claim 3, wherein in the scan direction said one beam has a positive vergence, said second beam has zero vergence, and said third beam has a negative vergence.

Claim 6

An f-θ lens comprising in combination a doublet which includes a meniscus negative element and a first meniscus positive element, a second meniscus positive element adjacent said first meniscus positive element, a first double convex positive element adjacent said second meniscus positive element, a second double convex positive element adjacent said first double convex positive element, and a double concave negative element adjacent said second double convex positive element.

Claim 7

An f-θ lens comprising in combination a doublet which includes a meniscus negative element and a first meniscus positive element, a second meniscus positive element adjacent said first meniscus positive element, a first double convex positive element adjacent said second meniscus positive element, a second double convex positive element adjacent said first double convex positive element, and a double concave negative element adjacent said second double convex positive element.

Claim 8

An f-θ lens, as defined in claim 5, wherein numerical data of the lens are as follows: ______________________________________ SURF. RADIUS THICKNESS GLASS ______________________________________ Entrance Pupil 30.800 r1 -13.9300 2.500 762265 r2 -50.0263 6.900 651559 r3 -20.6003 0.500 r4 -119.667 5.320 651559 r5 -36.5497 0.500 r6 139.895 5.850 651559 r7 -64.1175 0.500 r8 63.2356 5.190 651559 r9 -269.725 2.517 r10 -93.2760 4.280 785258 r11 71.0150 ______________________________________ where r1-r11 represent radii of curvature of the respective lens elements.

Claim 9

An F-θ lens, said lens being adapted to be used in the optical path of a laser printer comprising a rotatable polygon scanner which provides an input beam composed of a plurality of beams of different wavelengths to the lens and a cylindrical optical element which receives the beam from said lens and directs the beam onto a receiving medium, said lens comprising: means for correcting in a scan direction for lateral color aberrations of each of said beams; and means operable with said cylindrical optical element for correcting in a cross-scan direction for axial color aberrations in each of said beams, said means operable with said cylindrical optical element including means for collimating said beam in the cross-scan direction in all of said wavelengths.

Claim 10

An F-θ lens, said lens being adapted to be used in the optical path of a laser printer comprising a rotatable polygon scanner which provides an input beam composed of a plurality of beams of different wavelengths to the lens and a cylindrical optical element which receives the beam from said lens and directs the beam onto a receiving medium, said lens comprising: means for correcting in a scan direction for lateral color aberrations of each of said beams; and means operable with said cylindrical optical element for correcting in a cross-scan direction for axial color aberrations in each of said beams, said means operable with said cylindrical optical element including means for collimating said beam in the cross-scan direction in all of said wavelengths.