Laser Scanning Unit Asymmetric Mirrors Deflection Error
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Solution Overview
Problem
Color laser printers face issues with relative errors in scanning line deflections due to different properties of four laser scanning units, leading to jitter and periodic shakes, which affect picture quality and increase manufacturing costs.
Innovation Solution
A laser scanning unit is designed with symmetrically disposed light sources and a rotatable deflector that deflects light beams in the sub-scanning direction, using f-θ lenses and asymmetrically positioned mirrors to ensure scanning line deflections occur in the same direction, reducing relative errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If four laser scanning units are used in a color laser printer, then each color can be printed with dedicated scanning, but manufacturing costs increase significantly and assembly complexity increases
Solution Approach 1:
The patent merges four separate laser scanning units into a single scanning unit that handles all four colors. This is achieved by using one laser diode that emits light for multiple colors and a single polygonal mirror that deflects the light for different colors onto different photosensitive drums, thereby reducing device complexity while maintaining printing quality
Solution Approach 2:
The single laser scanning unit is designed to perform multiple functions by scanning different colors (cyan, magenta, yellow, black) using one laser diode and one polygonal mirror. The system achieves multi-functionality by time-division multiplexing where the single scanner serves all four colors sequentially, eliminating the need for four dedicated scanning units
2Reliability
If four separate laser scanning units are used, then each color has dedicated scanning capability, but manufacturing costs increase due to component proliferation
Solution Approach 1:
The patent combines four scanning systems into one by using a single laser diode and single polygonal mirror that can scan all four colors. This merging reduces the number of components that need to be manufactured and assembled, thereby reducing manufacturing costs while maintaining scanning precision through proper optical design
Solution Approach 2:
The system changes the scanning parameters dynamically by controlling the rotation speed and position of the single polygonal mirror to scan different colors at different times. By adjusting these parameters, the single scanner achieves the functionality of four scanners, reducing component costs while maintaining precision
3Manufacturing precision
If slanting incidence scanning optical systems are used, then scanning line deflection is reduced, but relative error in deflection occurs due to different light paths
Solution Approach 1:
The patent introduces asymmetric mirror arrangements in the optical paths to compensate for the slanting incidence effects. By carefully designing the mirror positions and angles asymmetrically, the system corrects the relative deflection errors that occur with slanting incidence, achieving high precision for all four colors simultaneously
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 minimizes relative errors in scanning line deflections, improving picture quality and reducing manufacturing costs by allowing a single laser scanning unit to be used for color printing, enhancing the economic viability of color laser printers.
Implementation Method 1
first and second f-θ lenses which focus the light beams reflected by the deflector on scanning lines on photosensitive drums
Implementation Method 2
mirrors which are disposed asymmetrically with respect to the rotational axis of the deflector so that scanning line deflections in directions substantially equal to one another are formed on the respective photosensitive drums
Implementation Method 3
a rotatable deflector which deflects slantingly incident light beams in a sub-scanning direction from multiple light sources
Data Source
AI summary
A laser scanning unit and an image forming apparatus having the same are provided. The laser scanning unit includes a plurality of light sources symmetrically disposed, and a rotatable deflector deflecting slantingly incident light beams symmetrically in a sub-scanning direction from the plurality of light sources. First and second f-θ lenses focus the light beams reflected by the deflector on scanning lines on photosensitive drums and are disposed symmetrically with respect to a rotational axis of the deflector. Mirrors guide the light beams that have passed through the first and second f-θ lenses toward the respective photosensitive drums. The mirrors are disposed asymmetrically with respect to the rotational axis of the deflector so that the scanning lines formed on the respective photosensitive drums may be deflected in the same direction.