Light Scanning Optics With Fine Structure for Uniform Illuminance
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Solution Overview
Problem
Existing light scanning apparatuses suffer from uneven illuminance on the scanned surface due to differences in reflectivity of deflecting surfaces and folding mirrors caused by varying incident angles of light fluxes, leading to increased size and cost with the use of a λ/2 plate to mitigate this issue.
Innovation Solution
A light scanning apparatus with a first element featuring a fine structure on its incident or exit surfaces, including protruding portions arranged in specific directions, and a deflecting unit to deflect light fluxes, while using resin-made fθ lenses with birefringence to manage polarization and reflectivity, thereby reducing uneven illuminance without increasing size or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a λ/2 plate is provided in the incident optical system to suppress uneven illuminance, then uneven illuminance on the scanned surface is reduced, but the apparatus size increases
Solution Approach 1:
The patent combines the function of the λ/2 plate with the existing fθ lens by forming a fine structure (protruding portions) directly on the lens surface. This integration merges the polarization control function into the imaging optical element, eliminating the need for a separate λ/2 plate and reducing apparatus size while maintaining uniform illuminance across the scanned surface.
Solution Approach 2:
The fθ lens is given multiple functions: it serves both as an imaging lens and as a polarization control element through the integrated fine structure. This multi-functionality allows the single component to perform both beam shaping and polarization management, replacing what would traditionally require separate optical elements.
2Illumination intensity
If a λ/2 plate is provided in the incident optical system to suppress uneven illuminance, then uneven illuminance on the scanned surface is reduced, but the cost increases
Solution Approach 1:
The patent combines the function of the λ/2 plate with the existing fθ lens by forming a fine structure (protruding portions) directly on the lens surface. This integration merges the polarization control function into the imaging optical element, eliminating the need for a separate λ/2 plate and reducing apparatus size while maintaining uniform illuminance across the scanned surface.
Solution Approach 2:
The fθ lens is given multiple functions: it serves both as an imaging lens and as a polarization control element through the integrated fine structure. This multi-functionality allows the single component to perform both beam shaping and polarization management, replacing what would traditionally require separate optical 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
The apparatus effectively suppresses uneven illuminance on the scanned surface, maintaining printing performance by minimizing light amount differences between image heights, thus reducing density unevenness in printed images.
Implementation Method 1
the first fine structure on at least one of the incident surface or the exit surface of the first optical element includes a plurality of protruding portions each extending in a first direction, the plurality of protruding portions being arrayed in a second direction perpendicular to the first direction, and wherein the following condition is satisfied: 1/20≤Δ1/λ1≤1/6, where Δ1 represents a phase difference between the first direction and the second direction of birefringence
Data Source
AI summary
Provided is an apparatus including: an element in which a fine structure changing a polarization state of a light flux from a light source is formed on at least one of an incident surface or an exit surface thereof; a deflecting unit deflecting light flux that has passed through optical element to scan a scanned surface in a main scanning direction; and an optical system guiding light flux deflected by deflecting unit to scanned surface, wherein fine structure includes a plurality of protruding portions each extending in a first direction, the plurality of protruding portions being arrayed in a second direction perpendicular to first direction, and wherein the following condition is satisfied:1/20≤Δ1/λ1≤1/6,where Δ1 represents a phase difference between first direction and second direction of birefringence caused by fine structure, and λ1 represents a wavelength of light flux.