Multi-Beam Image Forming Apparatus Scan Speed Correction
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Solution Overview
Problem
Image forming apparatuses using multiple scan beams without fθ characteristics face challenges in maintaining constant pixel width due to varying scan speeds, leading to image defects, as the positions of scan beams differ in the main scanning direction, affecting exposure and light emission periods.
Innovation Solution
The apparatus employs a control unit to perform corrections in light emission periods and exposure amounts for each scan beam based on the section scanned, using detection timing to synchronize start timings and adjust scan speeds, ensuring consistent pixel width across the photosensitive member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a scan lens with fθ characteristics is used, then the scan speed is made constant, but the size and cost of the image forming apparatus increase
Solution Approach 1:
The invention changes the parameters of the image signals (frequency and phase) to compensate for the non-constant scan speed. By adjusting the frequency of image signals based on the position of scan beams, constant pixel width is achieved without requiring an fθ lens, thus avoiding the size and cost penalties while maintaining scanning performance
2Productivity
If multiple scan beams are used to scan different positions simultaneously, then productivity is improved, but image quality deteriorates due to varying pixel widths
Solution Approach 1:
The invention applies different frequency adjustments to image signals based on the local position of each scan beam. Each scan beam's image signal frequency is individually adjusted according to its position in the main scanning direction, ensuring that each beam produces constant pixel width at its specific location, thereby maintaining image quality while enabling parallel scanning for high productivity
Solution Approach 2:
The invention uses a detection unit to detect the first scan beam and provides feedback to the control unit, which then adjusts the frequency of image signals for both scan beams based on the detected position information. This feedback mechanism ensures that pixel width remains constant across all scan beams while maintaining high scanning productivity
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 solution effectively maintains consistent pixel widths and image quality by dynamically adjusting scan parameters, reducing image defects and enabling downsizing of the apparatus without the need for expensive fθ lenses.
Implementation Method 1
causes the scan beam to be transmitted through a scan lens
Implementation Method 2
causes the scan beam to be reflected by a rotative polygonal mirror
Implementation Method 3
the charged photosensitive member is irradiated with the scan beam. The image forming apparatus forms an electrostatic latent image on the photosensitive member
Data Source
AI summary
An image forming apparatus includes a detection unit configured to detect a first scan beam from a first light source; and a control unit. The control unit performs corrections in which a light emission period of scan beams per pixel is changed in accordance with which section is scanned by the scan beams, and performs corrections in which a light exposure amount by which the photosensitive member is exposed to light by the scan beams is changed in accordance with which section in the main scanning direction is scanned by the scan beams. Based on a detection timing at which the detection unit has detected the first scan beam, the control unit controls scan start timings at which the scan beams start scanning of the photosensitive member.