Scanning optical system
AssigneePENTAX Corporation
InventorDaisuke Koreeda
Life of this patent
Estimating the term…
Abstract
A scanning optical system includes first and a second lens elements, at least one of which is a plastic lens element. Each surface of the plastic lens element is an aspherical surface that is configured such that a shape in a main scanning plane is defined as a function of a distance, in the main scanning direction, from a surface reference axis thereof, and that a curvature in an auxiliary scanning plane which is perpendicular to the main scanning plane is defined as another function of a distance, in the main scanning direction, from the surface reference axis. At least one of the two surfaces of the plastic lens element are arranged such that the surface reference axis thereof is decentered from an axis of the beam in the auxiliary scanning direction.
Claims17
A scanning optical system for converging a beam scanning in a main scanning direction on a surface to be scanned, comprising a first lens element and a second lens element, at least one of said first lens element and said second lens element being a plastic lens element formed of plastic material,
- wherein each of two surfaces of said plastic lens element is an aspherical surface that is configured such that a shape in a main scanning plane is defined as a function of a distance, in the main scanning direction, from a surface reference axis thereof and that a curvature in an auxiliary scanning plane which is perpendicular to the main scanning plane is defined as another function of a distance, in the main scanning direction, from the surface reference axis, and
- wherein at least one of said two surfaces of said plastic lens element is arranged such that the surface reference axis thereof is decentered from a reference beam axis in the auxiliary scanning direction.
A scanning unit, comprising:
- a light source that emits a beam;
- a deflector that deflects the beam to scan within a predetermined angular range in a main scanning direction;
- and
- a scanning optical system for converging the beam scanned by the deflector on a surface to be scanned, said scanning system comprising a first lens element and a second lens element, at least one of said first lens element and said second lens element being a plastic lens element formed of plastic material,
- wherein each of two surfaces of said plastic lens element is an aspherical surface that is configured such that a shape in a main scanning plane is defined as a function of a distance, in the main scanning direction, from a surface reference axis thereof and that a curvature in an auxiliary scanning plane which is perpendicular to the main scanning plane is defined as another function of a distance, in the main scanning direction, from the surface reference axis, and
- wherein at least one of said two surfaces of said plastic lens element is arranged such that the surface reference axis thereof is decentered from a reference beam axis in the auxiliary scanning direction.
Dependencies are inferred from the claim text.