Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
277 words
An fθ lens system in a light scanning device which has means for focusing a light beam emitted from a light source unit as a linear image, and a rotating polygonal mirror having a reflecting surface near the focused linear image for deflecting the light beam at a constant angular velocity, for focusing the deflected light beam as a light spot on a surface to scan the latter with the light spot, said fθ lens system placing the reflecting position of the rotating polygonal mirror and the surface being scanned in conjugate relationship with respect to an auxiliary scanning direction, and having an fθ function, said fθ lens system comprising first and second lenses successively positioned in the named order from said rotating polygonal mirror toward said surface being scanned, said first lens comprising a single anamorphic lens having a first spherical surface and a second cylindrical surface and also having negative refractive power, said second lens comprising a single anamorphic lens having a first cylindrical surface and a second toric surface and also having positive refractive power, the surfaces of said first and second lenses being defined as first through fourth surfaces successively from said rotating polygonal mirror toward said surface being scanned, said fθ lens system satisfying the following conditions: (I) 0.35<R4x/R1x<0.85 (II) -0.120<(1/R3y)+(1/R4y)<-0.095 where Rix is the radius of curvature of the ith lens (i=1 through 4) in a plane in which the light beam is deflected by the rotating polygonal mirror, RiY is the radius of curvature of the ith lens in the auxiliary scanning direction, with the focal length fM of the fθ lens system in the main scanning direction being 100.
Claim 2
Dependent Claim
277 words
An fθ lens system in a light scanning device which has means for focusing a light beam emitted from a light source unit as a linear image, and a rotating polygonal mirror having a reflecting surface near the focused linear image for deflecting the light beam at a constant angular velocity, for focusing the deflected light beam as a light spot on a surface to scan the latter with the light spot, said fθ lens system placing the reflecting position of the rotating polygonal mirror and the surface being scanned in conjugate relationship with respect to an auxiliary scanning direction, and having an fθ function, said fθ lens system comprising first and second lenses successively positioned in the named order from said rotating polygonal mirror toward said surface being scanned, said first lens comprising a single anamorphic lens having a first spherical surface and a second cylindrical surface and also having negative refractive power, said second lens comprising a single anamorphic lens having a first cylindrical surface and a second toric surface and also having positive refractive power, the surfaces of said first and second lenses being defined as first through fourth surfaces successively from said rotating polygonal mirror toward said surface being scanned, said fθ lens system satisfying the following conditions: (I) 0.35<R4x/R1x<0.85 (II) -0.120<(1/R3y)+(1/R4y)<-0.095 where Rix is the radius of curvature of the ith lens (i=1 through 4) in a plane in which the light beam is deflected by the rotating polygonal mirror, RiY is the radius of curvature of the ith lens in the auxiliary scanning direction, with the focal length fM of the fθ lens system in the main scanning direction being 100.
Claim 3
Dependent Claim
19 words
An fθ lens system according to claim 1, wherein R4x/R1x and (1/R3y)+(1/R4y) meet the conditions: (I) 0.35<R4x/R1x<0.7 (II) -0.115<(1/R3y)+(1/R4y)<-0.095
Claim 4
Dependent Claim
20 words
An fθ lens system according to claim 1, wherein R4x/R1x and (1/R3y)+(1/R4y) meet the conditions: (I) 0.40<R4x/R1x <0.85 (II) -0.120<(1/R3y)+(1/R4y)<-0.100.