Aspherical Imaging Lens for Multi-Beam Optical Scanning
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Solution Overview
Problem
Existing optical scanning systems face challenges in reducing wavefront aberration distortion when multiple light beams are incident on an optical deflector at oblique angles, leading to complex system structures and difficulties in producing high-quality images due to spot rotation and lens manufacturing issues.
Innovation Solution
An optical scanning system is designed with a common imaging lens that directs multiple light beams onto a single deflecting surface at different angles, using an imaging optical element with optical surfaces defined by different functions for each region, ensuring that meridional lines shift towards the same side relative to the optical reference axis, reducing wavefront aberration distortion and simplifying the system structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple light beams are incident on an optical deflector at oblique angles, then the system can scan multiple photosensitive drums simultaneously, but wavefront aberration distortion occurs causing spot rotation and poor image quality
Solution Approach 1:
The imaging lens is designed with different aspherical coefficients for different regions (inner and outer regions) corresponding to different light beam incident angles. This local differentiation of optical properties allows each region to correct wavefront aberration specifically for its corresponding light beam, thereby reducing spot rotation and improving image quality while maintaining multi-drum scanning capability
Solution Approach 2:
The patent changes the aspherical coefficient parameter of the imaging lens based on the incident angle of light beams. By adjusting this optical parameter across different regions of the lens, the system compensates for wavefront aberration distortion caused by oblique incidence, thus maintaining spot quality across all scanned drums
2Manufacturing precision
If four long lenses are used to correct wavefront distortion for each light beam, then spot rotation is reduced, but the system structure becomes very complicated
Solution Approach 1:
The patent merges the wavefront aberration correction function into a single imaging lens by designing it with spatially varying aspherical coefficients. Instead of using four separate long lenses as in prior art, this unified lens structure integrates the correction functionality for all light beams, significantly simplifying the system structure while maintaining spot quality
Solution Approach 2:
The imaging lens is designed to perform multiple functions simultaneously: it focuses light beams from different angles onto the scan surface and corrects wavefront aberration for all beams. This multi-functional design eliminates the need for separate correction lenses, reducing system complexity
3Manufacturing precision
If the lens surface is divided into inner and outer regions with different aspherical surfaces, then wavefront distortion is reduced, but sink or shrink occurs at discontinuous points during injection molding
Solution Approach 1:
The patent uses continuous parameter changes (aspherical coefficients) across the lens surface rather than discontinuous surface definitions. This allows the lens to achieve wavefront aberration correction while maintaining manufacturing continuity, preventing sink or shrink defects at discontinuous points during injection molding
Solution Approach 2:
The patent employs aspherical surface geometry with continuous curvature transitions. By using smooth curved surfaces with varying aspherical coefficients rather than abrupt discontinuities, the design achieves optical performance while ensuring manufacturability and preventing molding defects
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 approach allows for effective reduction of wavefront aberration distortion, enabling optical scanning with good spot quality and simplifying the system structure, while also facilitating easier lens production by reducing the thickness and refractive index distribution of the imaging lens.
Implementation Method 1
an imaging optical element with optical surfaces defined by different functions for each region, ensuring that meridional lines shift towards the same side relative to the optical reference axis, reducing wavefront aberration distortion
Implementation Method 2
directing a plurality of light beams from the plurality of light emitting portions onto one and the same deflecting surface of the optical deflector, at different angles relative to a normal to the deflecting surface
Data Source
AI summary
An optical scanning system having an imaging optical system for imaging a plurality of light beams deflected by a deflecting surface of a optical deflector upon different scan surfaces. The imaging optical system includes an imaging optical element which has at least one optical surface defined, with respect to the sub-scan sectional plane, in accordance with different functions related to different regions. When with respect to the sub-scan sectional plane the plurality of light beams incident on one and the same deflecting surface of the optical deflector have the same reflection point thereon, there is relationship defined for a meridional line of the optical surface of the imaging optical element defined in accordance with the function, whereas when the plurality of light beams have different reflection points on the optical deflector, there is a different relationship for the meridional line.