Optical Beam Scanning Apparatus with Flat Plate Aberration Correction
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Solution Overview
Problem
Conventional optical beam scanning systems face challenges in achieving high resolution and speed while maintaining image quality, as they require large polygon mirrors that increase motor load, noise, and vibration, and suffer from wave front aberration due to the use of edge parts of the polygon mirror in overillumination scanning systems.
Innovation Solution
An optical beam scanning apparatus with a pre-deflection optical system forming a luminous flux as a line image in the main scanning direction, a scanning unit with a wider luminous flux than its reflecting surface, and a post-deflection optical system including at least two flat plates to transmit and correct the luminous flux, ensuring suitable beam diameter and profile on the photoconductive drum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of polygon mirror surfaces is increased to achieve high resolution and speed, then image quality and scanning performance are improved, but motor load, noise, and vibration increase
Solution Approach 1:
The patent segments the scanning function by using multiple independent light sources (laser diodes) to generate multiple beams simultaneously, rather than relying on a single light source scanning across all surfaces. This allows the system to achieve high-resolution scanning without requiring an excessive number of polygon mirror surfaces, thereby reducing motor load and vibration while maintaining image quality.
2Productivity
If the number of polygon mirror surfaces is increased to achieve high resolution and speed, then scanning performance is improved, but noise and vibration increase
Solution Approach 1:
The patent divides the scanning task into multiple parallel beams generated by separate light sources, each targeting specific color components. This segmentation allows the polygon mirror to operate with fewer surfaces at lower speeds, significantly reducing noise and vibration while maintaining high scanning productivity through simultaneous multi-color processing.
Solution Approach 2:
The patent replaces the conventional single-beam mechanical scanning system with a multi-beam optical system. By using multiple laser diodes to generate parallel beams that are processed through a pre-deflection optical system, the system reduces reliance on high-speed polygon mirror rotation, thereby decreasing mechanical noise and vibration while achieving high scanning speed.
3Area of stationary object
If edge parts of the polygon mirror are used in overillumination scanning systems, then scanning coverage is improved, but wave front aberration occurs
Solution Approach 1:
The patent applies local quality by using a pre-deflection optical system that directs each beam to specific regions of the polygon mirror surfaces. This ensures that only the high-precision central portions of the reflecting surfaces are utilized, avoiding the edge parts that cause wave front aberration. Each beam is locally optimized to scan only the necessary area with high precision, maintaining both coverage and image quality.
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 reduces motor load, noise, and vibration, while effectively correcting wave front aberration and maintaining high image quality by utilizing the entire reflecting surface of the polygon mirror, allowing for high-speed and high-resolution image formation.
Implementation Method 1
a pre-deflection optical system configured to form a luminous flux emitted from the light source to image the luminous flux as a line image in a prescribed direction corresponding to a main scanning direction
Implementation Method 2
a scanning unit configured to scan the imaged luminous flux by the pre-deflection optical system against a scanning subject
Implementation Method 3
a post-deflection optical system configured to image the luminous flux scanned by the scanning unit on the scanning subject
Data Source
AI summary
In an image forming apparatus provided with an optical beam scanning apparatus according to the invention, an optical beam scanning apparatus of an overillumination scanning optical system includes a semiconductor laser device as a light source, a pre-deflection optical system, a polygon mirror, and a post-deflection optical system, with a width of the luminous flux made incident on the polygon mirror being wider than a width of one reflecting surface forming the polygon mirror, wherein at least two sheets of flat plate for transmitting the luminous flux scanned by the polygon mirror are provided in the post-deflection optical system. In accordance with an image forming apparatus provided with an optical beam scanning apparatus according to the invention, not only a wave front aberration on a photoconductive drum can be suitably corrected, but suitable beam diameter and beam profile can be obtained on the photoconductive drum.