Optical Scanning Device Free-Form Lens Spherical Aberration Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optical scanning devices with polygon mirrors having curved reflecting surfaces are costly to manufacture and face challenges in maintaining beam focus across the photosensitive drum due to varying optical path lengths and aberrations, especially with changes in deflection angles.
Innovation Solution
The optical scanning device employs a free-form-surface lens in combination with a collimator lens and a polygon mirror, generating different spherical aberrations based on the beam's path, allowing focus on every point of the photosensitive drum without additional optical elements between the mirror and drum, reducing manufacturing costs by eliminating the need for curved reflecting surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a polygon mirror with curved reflecting surfaces is used, then the beam can be focused on the photosensitive drum, but the manufacturing cost increases
Solution Approach 1:
A collimator lens is introduced as an intermediary optical element between the light source and the polygon mirror. This lens pre-collimates the light beam, allowing a flat polygon mirror to achieve proper focus on the photosensitive drum without requiring expensive curved reflecting surfaces. The collimator lens mediates the optical path to compensate for the flat mirror's limitations.
2Adaptability or versatility
If the deflection angle changes, then the scanning range increases, but the beam focus and intensity consistency deteriorates
Solution Approach 1:
The optical system is designed with position-dependent optical properties. The collimator lens and scanning lens work together to provide different optical path compensations for different deflection angles. This local optimization ensures that beam focus and intensity remain consistent across the entire scanning range, addressing the specific requirements of each angular position rather than using a uniform approach.
Solution Approach 2:
The patent employs optical elements with specific focal lengths and positions that change the optical parameters dynamically with deflection angle. By carefully selecting the focal lengths and positions of the collimator lens and scanning lens, the system maintains beam quality across varying deflection angles, compensating for optical path length variations through parameter optimization.
3Manufacturing precision
If additional optical elements are added between the polygon mirror and photosensitive drum, then beam focus can be maintained, but the device complexity increases
Solution Approach 1:
The collimator lens and scanning lens are designed to perform multiple functions simultaneously. The collimator lens not only collimates the light but also contributes to focus maintenance across different deflection angles. The scanning lens serves both to scan the beam and to compensate for optical path variations. This multi-functionality reduces the need for additional dedicated focus adjustment elements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration maintains consistent beam focus and intensity across the photosensitive drum, reducing the impact of deflection angle changes and allowing for high-quality image writing without the need for costly curved mirrors, thus enhancing image writing performance and reducing production costs.
Implementation Method 1
generating different spherical aberrations based on the beam's path, allowing focus on every point of the photosensitive drum
Implementation Method 2
The collimator lens 14 and the free-form-surface lens 16 form an optical system 17 for causing the beam B0 that is a divergent light to converge and to be focused onto the photosensitive drum 20
Implementation Method 3
a polygon mirror having cylindrical or spherical reflecting surfaces is employed
Data Source
Figure 1~2
Figure 3~4
Figure 5~7
AI summary
An optical scanning device (10) for scanning a photoreceptor surface (20) with a beam, said optical scanning device (10) comprising: a light source (12) for emitting the beam; an optical system (17) for causing the beam emitted from the light source (12) to converge; a deflector (18) that includes a polygon mirror with a plurality of reflecting surfaces and that deflects the beam that has passed through the optical system (17) by rotations of the polygon mirror. In the optical scanning device (10), no optical system for causing the beam to converge or diverge is disposed between the deflector (18) and the photoreceptor surface (20). The optical system (17) generates spherical aberration depending on which part of the optical system (17) in a main-scanning direction the beam passes through. The beam enters into three or more adjacent reflecting surfaces of the polygon mirror at a time.