Polygon Mirror Deflection Surface Profile for High-Speed Scanning
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Solution Overview
Problem
Conventional optical deflectors used in image formation apparatuses face issues with noise, vibration, and image quality due to increased rotation speed, leading to deteriorated high-density image formation and scan precision, particularly with multiple light beams causing scattered light and ghost images from uneven deflection surfaces.
Innovation Solution
An optical scan apparatus with a polygon mirror deflector that has deflection surfaces with a mean width of profile elements in the sub scan direction smaller than the spacing of adjacent light beams, and a cutting process that sets the cutting width greater than the illumination area, ensuring precise cutting and reducing scattering, along with a processing method using a rotatable support body with distinct rough and finish cutting members to process complex-shaped polygon mirrors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotation speed of the polygon mirror is increased to speed up image outputs, then productivity is improved, but noise and vibration from the drive system increase and image quality deteriorates
Solution Approach 1:
The patent divides the single polygon mirror into multiple small-sized polygon mirrors (first polygon mirror and second polygon mirror) that are superimposedly disposed. Each polygon mirror handles a portion of the light beams, allowing the system to achieve high-speed scanning without requiring excessive rotation speed from individual mirrors, thereby reducing noise and vibration.
Solution Approach 2:
The patent arranges multiple polygon mirrors in the rotation axis direction (vertical stacking), utilizing the third dimension to distribute the deflection task. This dimensional arrangement allows parallel processing of light beams without increasing the rotation speed of individual mirrors, thus maintaining low noise and vibration levels while improving productivity.
2Productivity
If the rotation speed of the polygon mirror is increased to speed up image outputs, then productivity is improved, but image quality deteriorates due to trade-off with high-density image formation
Solution Approach 1:
By segmenting the light beam deflection task across multiple polygon mirrors, each mirror operates at moderate speed while collectively achieving high throughput. This segmentation allows maintenance of precise spot shapes and sizes for each beam, ensuring high-density image formation quality without sacrificing productivity.
3Productivity
If conventional optical deflectors are used with multiple light beams, then productivity is improved through concurrent scanning, but spots of light beams have different shapes and sizes causing generation of scattered light
Solution Approach 1:
The patent designs each polygon mirror with specific deflection surface characteristics tailored to its position and function. The deflection surfaces are configured to produce uniform spot shapes and sizes for the specific light beams they deflect, ensuring consistent image quality across all concurrent beams while maintaining high productivity.
4Ease of manufacture
If the deflection surface has undulation around incident positions of light beams, then manufacturing is simplified, but spot shapes are differentiated due to lens effect resulting in deteriorating granularity of images
Solution Approach 1:
The patent specifies precise deflection surface configurations that must be established during manufacturing to prevent spot shape differentiation. By pre-configuring the deflection surfaces with appropriate profiles before use, the system maintains uniform spot shapes and sizes, ensuring good image granularity while allowing for practical manufacturing methods.
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 enhances scan speed and precision, prevents light beam scattering, and maintains uniform spot sizes, resulting in improved image quality and reduced noise, enabling high-precision image formation with reduced vibration and environmental impact.
Implementation Method 1
an optical deflector which rotates around a predetermined rotation axis to scan a scanning plane with at least three or more light beams in a main scan direction
Data Source
AI summary
In the optical deflector, the mean width of profile elements of a cross section of the deflection surface in the sub scan direction is set to be less than the spacing between spots of the light beams formed in the sub scan direction of the deflection surface. This makes it possible to prevent a variation in the size and shape of the spots of the light beams deflected by the deflection surface due to the undulation (unevenness) of the deflection surface. As a result, it is able to suppress a decrease of the granularity of images and form images with high quality.