Scanning optical system for use in a laser beam printer

Claim 2

An optical system comprising: a semiconductor laser; a collimating lens that produces a beam of generally parallel rays from laser light emitted from said semiconductor laser; a cylindrical lens that has a curvature in a first cross section and which once performs a focusing of the laser light to form an image in said first cross section; a deflector that is disposed behind a point at which said image has been formed in the first cross section as a result of focusing by said cylindrical lens; and an anamorphic scanning lens system by which the deflected beam from said deflector is concentrated on a scanning plane, said anamorphic optical system satisfying the following condition: 0.03f<l<0.25f (1) where l is the distance between a plane of deflection of said deflector and a point at which said image has been formed in said first cross section as a result of focusing with said cylindrical lens, and f is the focal length of the scanning lens system in a second cross section, substantially perpendicular to said first cross section.

Claim 3

An optical system comprising: a semiconductor laser; a collimating lens that produces a beam of generally parallel rays of beam from laser light emitted from said semiconductor laser; a cylindrical lens that has a curvature in a first cross section and which once performs a focusing of the laser light to form an image in said first cross section; a deflector that is disposed behind a point at which said image has been formed in the first cross section as a result of focusing by said cylindrical lens; and an anamorphic scanning lens system by which the deflected beam from said deflector is concentrated on a scanning plane, said anamorphic lens system being composed, in order from a side of said deflector, of a first, a second and a third lens group; a lens of said first lens group being a negative lens that has a concave cylindrical surface with a curvature being present in the first cross section; a lens of said second lens group being a convex meniscus lens that has a concave surface directed toward the side of said deflector; and a lens of said third group having a planar surface on the side of said deflector and a convex toric surface on the side of the scanning plane which has a stronger curvature in the first cross section than in a second cross section perpendicular thereto.

Claim 4

An optical system comprising: a semiconductor laser; a collimating lens that produces a beam of generally parallel rays of beam from laser light emitted from said semiconductor laser; a cylindrical lens that has a curvature in a first cross section and which once performs a focusing of the laser light to form an image in said first cross section; a deflector that is disposed behind a point at which said image has been formed in the first cross section as a result of focusing by said cylindrical lens; and an anamorphic scanning lens system by which the deflected beam from said deflector is concentrated on a scanning plane, said anamorphic lens system being composed, in order from a side of said deflector, of a first, a second and a third lens group; a lens of said first lens group being a negative lens that has a concave cylindrical surface with a curvature being present in the first cross section; a lens of said second lens group being a convex meniscus lens that has a concave surface directed toward the side of said deflector; and a lens of said third group having a planar surface on the side of said deflector and a convex toric surface on the side of the scanning plane which has a stronger curvature in the first cross section than in a second cross section perpendicular thereto.

Claim 5

An optical system according to claim 2 which satisfies the following condition: 1.7<m<2.7 where m is the magnification of an image formed on the scanning plane by focusing with said lens system relative to said image formed in the first cross section by focusing with said cylindrical lens.

Claim 6

An optical system as recited in claim 3, wherein said anamorphic scanning lens system consists of three lenses, each lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r' i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r' i+1 in said first cross section, a thickness d i , an aerial separation to a lens further away from said deflector of d i+1 and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 -227.748 -227.748 7.46 1.71230 2 ∞ 34.870 5.12 3 -168.731 -168.731 10.00 1.60910 4 -154.768 -154.768 0.50 5 ∞ ∞ 16.80 1.71230 6 -88.050 -26.170 ______________________________________

Claim 7

An optical system as recited in claim 3, wherein said anamorphic scanning lens system consists of three lenses, each lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r' i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r' i+1 in said first cross section, a thickness d i , an aerial separation to a lens further away from said deflector of d i+1 and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 -224.410 -224.410 7.00 1.73814 2 ∞ 27.470 4.58 3 -164.214 -164.214 10.00 1.60910 4 -151.400 -151.400 0.50 5 ∞ ∞ 16.27 1.73814 6 -89.509 -24.180 ______________________________________

Claim 8

An optical system as recited in claim 3, wherein said anamorphic scanning lens system consists of three lenses, each lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r' i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r' i+1 in said first cross section, a thickness d i , an aerial separation to a lens further away from said deflector of d i+1 and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 -225.620 -225.620 7.95 1.71230 2 ∞ 32.200 4.83 3 -189.738 -189.738 10.20 1.60910 4 -166.077 -166.077 0.40 5 ∞ ∞ 16.80 1.71230 6 -88.700 -25.10 ______________________________________

Claim 9

An optical system as recited in claim 3, wherein said anamorphic scanning lens system consists of three lenses, each lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r' i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r' i+1 in said first cross section, a thickness d i , an aerial separation to a lens further away from said deflector of d i+1 and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 -176.700 -176.700 11.19 1.71230 2 ∞ 53.2 3.60 3 -173.952 -173.952 7.50 1.51072 4 -128.547 -128.547 0.50 5 ∞ ∞ 17.00 1.71230 6 -76.90 -25.5 ______________________________________

Claim 10

An optical system as recited in claim 3, wherein said anamorphic scanning lens system consists of three lenses, each lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r' i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r' i+1 in said first cross section, a thickness d i , an aerial separation to a lens further away from said deflector of d i+1 and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 -159.750 -159.750 12.00 1.71230 2 ∞ 61.6 6.30 3 -850.409 -850.409 12.30 1.51072 4 -172.480 -172.480 2.70 5 ∞ ∞ 17.40 1.71230 6 -144.50 -40.5 ______________________________________

Claim 11

An optical system as recited in claim 3, wherein said anamorphic scanning lens system consists of three lenses, each lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r' i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r' i+1 in said first cross section, a thickness d i , an aerial separation to a lens further away from said deflector of d i+1 and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 -193.485 -193.485 11.40 1.71230 2 ∞ 51.3 4.37 3 -220.000 -220.000 7.95 1.51072 4 -166.058 -166.058 0.50 5 ∞ ∞ 17.00 1.71230 6 -86.50 -26.95 ______________________________________

Claim 12

An optical system comprising: a semiconductor laser; a collimating lens that produces a beam of generally parallel rays from laser light emitted from said semiconductor laser; a cylindrical lens that has a curvature in a first cross section and which once performs a focusing of the laser light to form an image in said first cross section; a deflector that is disposed behind a point at which said image has been formed in the first cross section as a result of focusing by said cylindrical lens; and an anamorphic scanning lens system by which the deflected beam from said deflector is concentrated on a scanning plane, said scanning lens system being composed, in order from a side of said deflector, of a first and a second lens group; a lens in said first lens group being a negative lens that has a concave cylindrical surface with a curvature being present in said first cross section; and a lens in said second lens group having a planar surface on a side of said deflector and a convex toric surface on a side of the scanning plane which has a stronger curvature in the first cross section than in a second cross section perpendicular thereto.

Claim 13

An optical system comprising: a semiconductor laser; a collimating lens that produces a beam of generally parallel rays from laser light emitted from said semiconductor laser; a cylindrical lens that has a curvature in a first cross section and which once performs a focusing of the laser light to form an image in said first cross section; a deflector that is disposed behind a point at which said image has been formed in the first cross section as a result of focusing by said cylindrical lens; and an anamorphic scanning lens system by which the deflected beam from said deflector is concentrated on a scanning plane, said scanning lens system being composed, in order from a side of said deflector, of a first and a second lens group; a lens in said first lens group being a negative lens that has a concave cylindrical surface with a curvature being present in said first cross section; and a lens in said second lens group having a planar surface on a side of said deflector and a convex toric surface on a side of the scanning plane which has a stronger curvature in the first cross section than in a second cross section perpendicular thereto.

Claim 14

A optical system according to claim 10 which satisfies the following condition: 1.1<m<1.7 where m is the magnification of the image formed on the scanning plane by focusing with said lens system relative to said image formed in said first cross section by focusing with said cylindrical lens.

Claim 15

An optical system according to claim 10 which satisfies the following condition: 0.15f<|f.sub.1 '|<0.35f where f 1 ' is the focal length of said lens in said first lens group in the first cross section, and f is a focal length of the anamorphic scanning lens system in said second cross section.

Claim 16

An optical system as recited in claim 12, wherein said anamorphic scanning lens system consists of two lenses, each lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r' i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r' i+1 in said first cross section, a thickness d i , an aerial separation to a lens further away from said deflector of d i+1 and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 ∞ -22.4 10.95 1.60910 2 392.892 392.892 8.59 3 ∞ ∞ 19.50 1.76591 4 -82.70 -25.5 ______________________________________

Claim 17

An optical system as recited in claim 12, wherein said anamorphic scanning lens system consists of two lenses, each lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r' i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r' i+1 in said first cross section, a thickness d i , an aerial separation to a lens further away from said deflector of d i+1 and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 ∞ -32.5 8.90 1.71230 2 423.000 423.000 7.94 3 ∞ ∞ 21.96 1.76591 4 -82.000 -26.2 ______________________________________

Claim 18

An optical system as recited in claim 12, wherein said anamorphic scanning lens system consists of two lenses, each lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r' i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r' i+1 in said first cross section, a thickness d i , an aerial separation to a lens further away from said deflector of d i+1 and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 ∞ -22.3 9.89 1.71230 2 425.000 425.000 10.23 3 ∞ ∞ 22.60 1.76591 4 -87.75 -26.5 ______________________________________

Claim 19

An optical system comprising: a semiconductor laser; a collimating lens that produces a beam of generally parallel rays from laser light emitted from said semiconductor laser; a cylindrical lens that has a curvature in a first cross section and which once performs a focusing of the laser light to form an image in said first cross section; a deflector that is disposed behind a point at which said image has been formed in the first cross section as a result of focusing by said cylindrical lens; and an anamorphic scanning lens system by which a deflected beam from said deflector is concentrated on a scanning plane, said anamorphic scanning lens system being composed, in order from a side of said deflector side, of four lens groups; a first-group lens being a negative lens that has a concave cylindrical surface with a curvature being present in the first cross section; a second-group lens being a convex meniscus lens that has its concave surface directed toward the deflector side; a third-group lens having a planar surface on the deflector side and a convex toric surface on the side of the scanning plane which has a stronger curvature in the first cross section than in a second cross section perpendicular thereto; and a fourth-group lens having convex cylindrical surface which has a curvature in the first cross section.

Claim 20

An optical system comprising: a semiconductor laser; a collimating lens that produces a beam of generally parallel rays from laser light emitted from said semiconductor laser; a cylindrical lens that has a curvature in a first cross section and which once performs a focusing of the laser light to form an image in said first cross section; a deflector that is disposed behind a point at which said image has been formed in the first cross section as a result of focusing by said cylindrical lens; and an anamorphic scanning lens system by which a deflected beam from said deflector is concentrated on a scanning plane, said anamorphic scanning lens system being composed, in order from a side of said deflector side, of four lens groups; a first-group lens being a negative lens that has a concave cylindrical surface with a curvature being present in the first cross section; a second-group lens being a convex meniscus lens that has its concave surface directed toward the deflector side; a third-group lens having a planar surface on the deflector side and a convex toric surface on the side of the scanning plane which has a stronger curvature in the first cross section than in a second cross section perpendicular thereto; and a fourth-group lens having convex cylindrical surface which has a curvature in the first cross section.

Claim 21

An optical system according to claim 16 which satisfies the following condition: 0.8<m<2.0 where m is a magnification of the image formed on the scanning plane by focusing with said anamorphic scanning lens system relative to said image formed in the first cross section by focusing with said cylindrical lens.

Claim 22

An optical system as recited in claim 17, wherein said anamorphic scanning lens system consists of four lenses, each lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r' i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r' i+1 in said first cross section, a thickness d i , an aerial separation to a lens further away from said deflector of d i+1 and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 -177.221 -177.221 12.96 1.71230 2 ∞ 60.68 9.09 3 -7l4.254 -7l4.254 14.79 1.51072 4 -201.889 -201.889 2.01 5 ∞ ∞ 15.94 1.71230 6 -152.654 -52.88 51.85 7 ∞ ∞ 15.00 1.51072 8 ∞ -154.56 ______________________________________

Claim 23

An optical system as recited in claim 17, wherein said anamorphic scanning lens system consists of four lenses, each lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r' i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r' i+1 in said first cross section, a thickness d i , an aerial separation to a lens further away from said deflector of d i+1 and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 -218.512 -218.512 17.65 1.63552 2 ∞ 20.6 5.46 3 -267.583 -267.583 9.60 1.51072 4 -199.640 -199.640 0.60 5 ∞ ∞ 19.11 1.68443 6 -102.54 -37.60 48.59 7 ∞ ∞ 9.60 1.51072 8 ∞ -55.53 ______________________________________

Claim 24

An optical system as recited in claim 17, wherein said anamorphic scanning lens system consists of four lenses, each lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r' i+1 in said first cross section, a thickness d i , an aerial separation to a lens further away from said deflector of d i+1 and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 -194.926 -194.926 12.12 1.71230 2 ∞ 38.96 8.71 3 -654.385 -654.385 12.36 1.51072 4 -211.817 -211.817 1.91 5 ∞ ∞ 17.71 1.71230 6 -142.685 -46.87 54.90 7 ∞ 114.53 13.40 1.51072 8 ∞ ∞ ______________________________________

Claim 25

An optical system comprising: a semiconductor laser; a collimating lens that produces a beam of generally parallel rays from laser light emitted from said semiconductor laser; a cylindrical lens that has a curvature in a first cross section and which once performs a focusing of the laser light to form an image in said first cross section; a deflector that is disposed behind a point at which an image has been formed in the first cross section as a result of focusing by said cylindrical lens; and an anamorphic scanning lens system by which the deflected beam from said deflector is concentrated on a scanning plane, said anamorphic scanning lens system consisting of a single lens group that has a convex toric surface on the side of the scanning plane which has a stronger curvature in the first cross section than in a second cross section perpendicular thereto.

Claim 26

An optical system comprising: a semiconductor laser; a collimating lens that produces a beam of generally parallel rays from laser light emitted from said semiconductor laser; a cylindrical lens that has a curvature in a first cross section and which once performs a focusing of the laser light to form an image in said first cross section; a deflector that is disposed behind a point at which an image has been formed in the first cross section as a result of focusing by said cylindrical lens; and an anamorphic scanning lens system by which the deflected beam from said deflector is concentrated on a scanning plane, said anamorphic scanning lens system consisting of a single lens group that has a convex toric surface on the side of the scanning plane which has a stronger curvature in the first cross section than in a second cross section perpendicular thereto.

Claim 27

An optical system according to claim 21 which satisfies the following condition: 1.7<m<2.7 where m is the magnification of the image formed on the scanning plane by focusing with said anamorphic scanning lens system relative to the image formed in the first cross section by focusing with said cylindrical lens.

Claim 28

An optical system as recited in claim 22, wherein said anamorphic scanning lens system consists of one lens, said lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r' i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r'i+1 in said first cross section, a thickness d i and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 ∞ ∞ 11.80 1.51072 2 -120.8 -40.4 ______________________________________

Claim 29

An optical system as recited in claim 22, wherein said anamorphic scanning lens system consists of one lens, said lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r' i+1 in said first cross section, a thickness d i and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 ∞ ∞ 11.75 1.48479 2 -114.7 -37.8 ______________________________________

Claim 30

An optical system as recited in claim 22, wherein said anamorphic scanning lens system consists of one lens, said lens having a surface facing said deflector of a radius of curvature r i in said second cross section and of a radius of curvature r i in said first cross section and a surface facing away from said deflector of a radius of curvature r i+1 in said second cross section and a radius of curvature r' i+1 in said first cross section, a thickness d i and a refractive index of n i , said anamorphic scanning lens system satisfying the following table: ______________________________________ i r.sub.i r'.sub.i d.sub.i n.sub.i ______________________________________ 1 ∞ -200 11.00 1.48479 2 -120.0 -29.2 ______________________________________