Light Scanning Optics With Aspherical Surfaces for Ghost Suppression
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Solution Overview
Problem
Existing light scanning apparatuses face issues with optical performance reduction and increased sensitivity to light beam vibrations due to the use of aspherical surfaces with third-order coefficients, leading to ghost and return light that degrade image quality.
Innovation Solution
The apparatus employs a design where the incident and exit surfaces of imaging optical elements have aspherical coefficients represented by specific equations, with Mmn not equal to 0 for m not equal to 0, and M01 of the same sign, to correct sagittal tilt angles and reduce ghost and return light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a sagittal tilt surface is provided to suppress ghost and return light, then image quality is improved, but scanning-line curvature occurs and optical performance deteriorates
Solution Approach 1:
The patent changes the surface shape parameters from a simple tilt surface to a complex aspherical surface with multiple coefficients (Mmn). By adjusting parameters M01, M03, M11, M13, M21, M23, M31, and M33, the invention achieves both suppression of ghost/return light and correction of scanning-line curvature, resolving the contradiction between harmful factor suppression and optical performance maintenance.
Solution Approach 2:
The patent combines multiple aspherical surface characteristics (different Mmn coefficients) to create a composite optical surface that performs multiple functions simultaneously: suppressing ghost and return light while correcting scanning-line curvature and maintaining focus, thereby resolving the contradiction between harmful factor suppression and optical performance.
2Manufacturing precision
If one aspherical surface is provided to correct scanning-line curvature, then optical performance is improved, but it is insufficient in perpendicularly-incident systems
Solution Approach 1:
The patent divides the aspherical surface correction into multiple independent coefficients (M01, M03, M11, M13, M21, M23, M31, M33) that can be optimized separately. This segmentation allows each coefficient to address specific optical errors, making the correction more comprehensive and reliable in perpendicularly-incident systems where a single aspherical surface is insufficient.
Solution Approach 2:
The patent extends the correction approach from a single-dimensional aspherical surface to a multi-dimensional parameter space with eight independent Mmn coefficients. This dimensional expansion enables comprehensive correction of various optical errors including scanning-line curvature, maintaining focus, and suppression of ghost/return light simultaneously.
3Manufacturing precision
If third-order aspherical coefficients are used, then scanning-line curvature is corrected, but sensitivity to light beam vibrations increases
Solution Approach 1:
The patent changes from using only third-order coefficients to a comprehensive set of coefficients including zeroth-order (M01), second-order (M03, M11), and fourth-order (M13, M21, M23, M31, M33) terms. This parameter expansion allows for more precise control of the wavefront, reducing sensitivity to vibrations while maintaining scanning-line curvature correction.
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 design maintains optical performance while suppressing ghost and return light, enhancing image quality and stability in both-side scanning systems.
Implementation Method 1
an aspherical coefficient is represented by Mmn, a curvature radius within the sub-scanning cross section including the optical axis is represented by r, a variation coefficient is represented by Ei, and shapes within the sub-scanning cross section of the incident surface and the exit surface of each of the first optical element and the second optical element are represented by the following equations
Data Source
AI summary
An apparatus including: a deflector deflecting a light flux from a light source to scan a surface in a main scanning direction; and an imaging optical system including first and second optical elements, and guiding the light flux deflected by the deflector to the surface. When sagittal shapes of an incident surface and an exit surface of each of the first and second optical elements are represented by the following equations:x=z2/r′1+(1-(z/r′)2)1/2+∑n=18∑m=016Mmnymznr′=r(1+∑i=116Eiyi)in at least one of incident surface or exit surface of first optical element and each of incident surface and exit surface of second optical element, at least one of values of Mmn is not equal to 0 provided that m is not equal to 0, and incident surface and exit surface of second optical element have M01 of the same sign.