Laser Scanning Unit Shield Blocks Ghosting Light
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Solution Overview
Problem
Laser scanning units experience ghosting light issues due to reflection of laser beams, leading to print defects, particularly when a single polygonal mirror reflects multiple laser beams and interacts with opposing post-scan optical assemblies.
Innovation Solution
A shield is implemented within the laser scanning unit's housing to block ghosting light reflections between post-scan optical assemblies, featuring a main body with slots for the laser beams and a smooth interior surface to reduce noise, positioned near the crossing points of the beams to effectively prevent unwanted reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single polygonal mirror reflects multiple laser beams with opposing post-scan optical assemblies, then the device complexity is reduced, but ghosting light is generated causing print defects
Solution Approach 1:
The patent extracts and removes the harmful ghosting light from the optical path by introducing a shield that blocks the reflected light from entering the opposing post-scan assembly, thereby eliminating the print defects while maintaining the single polygonal mirror configuration
Solution Approach 2:
A shield is introduced as an intermediary element between the polygonal mirror and the post-scan assemblies to block the harmful reflected light, allowing the single mirror design to function without generating ghosting light interference
2Ease of operation
If post-scan optics are positioned to receive reflected laser beams, then the scanning function is achieved, but light reflection off lens surfaces generates ghosting light
Solution Approach 1:
The shield extracts and removes the ghosting light generated by lens reflection before it can interfere with the scanning function, allowing the post-scan optics to operate normally without producing harmful reflections
Solution Approach 2:
The shield converts the harmful reflected light into a blocked path, preventing it from reaching the photoconductive drum and causing print defects, while the main scanning function continues uninterrupted
3Manufacturing precision
If a shield is added to block ghosting light, then print quality is improved, but the device complexity increases
Solution Approach 1:
The shield is designed to provide blocking function only in the specific region where ghosting light travels, rather than covering the entire optical path, thereby minimizing the added complexity while maximizing the print quality improvement
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 shield significantly reduces ghosting light interference, enhancing print quality by blocking secondary reflections that cause unintended discharge on photoconductive drums, thereby improving the accuracy and consistency of toner images.
Implementation Method 1
Ghosting light may be generated by reflection of the laser beam at a surface of a lens forming part of the post-scan optics. The ghosting light may be re-reflected off the polygonal mirror toward the PC drum
Data Source
AI summary
A laser scanning unit is provided comprising: a housing; a scanning device; a first pre-scan assembly generating a first light beam and directing the first light beam toward the scanning device; a second pre-scan assembly generating a second light beam and directing the second light beam toward the scanning device; a first post-scan assembly receiving the first light beam reflected from the scanning device and causing a first portion of the first light beam to scan along a first scan path; and a second post-scan assembly receiving the second light beam reflected from the scanning device and causing a first portion of the second light beam to scan along a second scan path. The first post-scan assembly further reflects a second portion of the first light beam in a direction away from the first scan path. A shield is associated with the housing for blocking the second portion of the first light beam reflected by the first post-scan assembly during at least a portion of the scan of the first portion of the first light beam along the first scan path so as to prevent the second portion of the first light beam from entering the second post-scan assembly.