Laser Write Timing Correction via Photodetector Gain Switching
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Solution Overview
Problem
Image forming apparatuses experience shifts in write start timing due to changes in light intensity, leading to positional misalignments and color shifts, which degrade image quality, particularly in color image forming, and existing solutions either fail to suppress degradation, increase costs, or are not optimized for each apparatus.
Innovation Solution
The image forming apparatus includes a photosensor with a gain switching circuit that adjusts sensitivity based on multiple sensitivity settings, using characteristic value information to correct shifts in write start timing and update correction values accordingly, without altering light intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light intensity is changed to adjust detection sensitivity, then detection sensitivity is improved, but write start timing shifts causing positional misalignment and color shifts
Solution Approach 1:
The patent changes the sensitivity parameter of the photodetector element by switching between multiple predetermined sensitivity settings rather than changing light intensity. This allows adjustment of detection sensitivity while maintaining constant light intensity, thereby preventing write start timing shifts and positional misalignments.
Solution Approach 2:
The system dynamically switches between multiple sensitivity settings of the photodetector element based on the required detection sensitivity. This dynamic adjustment mechanism allows the system to adapt to different detection requirements without altering the light intensity, thus maintaining write start timing accuracy while achieving variable detection sensitivity.
2Manufacturing precision
If multiple sensitivity settings are implemented with characteristic value correction, then write start timing accuracy is improved, but device complexity increases
Solution Approach 1:
The patent manages device complexity by systematically organizing characteristic values that represent the relationship between sensitivity settings and write start timing. The control circuit switches between predetermined sensitivity settings and applies corresponding characteristic value corrections, which simplifies the management of multiple sensitivity configurations while maintaining write start timing accuracy.
Solution Approach 2:
The system incorporates feedback mechanisms where the control circuit monitors the sensitivity setting and applies appropriate characteristic value corrections to compensate for any write start timing shifts. This feedback loop ensures write start timing accuracy is maintained across different sensitivity settings without requiring overly complex circuitry.
3Reliability
If sensitivity is switched to maintain detection accuracy across different light intensities, then detection reliability is improved, but write start timing shifts occur
Solution Approach 1:
The patent resolves this contradiction by changing the sensitivity parameter of the photodetector element through discrete switching between multiple predetermined sensitivity settings. Each sensitivity setting has associated characteristic values that are used to correct write start timing, allowing the system to maintain both detection reliability and write start timing accuracy simultaneously.
Solution Approach 2:
The control circuit implements feedback by monitoring which sensitivity setting is active and applying the corresponding characteristic value correction to the write start timing. This feedback mechanism ensures that regardless of which sensitivity setting is used for reliable detection, the write start timing remains accurate by compensating for any potential shifts.
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 effectively corrects write start timing shifts, maintains image quality, and reduces implementation costs by optimizing correction values for each apparatus, ensuring stable detection of laser beams.
Implementation Method 1
a photodetector element to detect the beam with multiple sensitivities to determine a write start timing at which the light-emitting element start emitting the beam
Data Source
AI summary
An image forming apparatus includes a photoconductor; a light-emitting element; a deflector to deflect a beam emitted by the light-emitting element to scan the photoconductor with the beam; a photodetector element to detect the beam with multiple sensitivities to determine a write start timing at which the light-emitting element start emitting the beam; and circuitry. The circuitry switches to any one of the multiple sensitivities of the photodetector element; controls the light-emitting element to set a light intensity of the beam; switches the multiple sensitivities according to the light intensity; uses characteristic value information of a relationship between the light intensity and an amount of change in the write start timing to correct a shift in the write start timing; calculates the amount of change while switching to each of the multiple sensitivities; and updates a characteristic value in the characteristic value information based on the amount of change.