Laser Position Deviation Correction in Image Forming Apparatus
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Solution Overview
Problem
Existing electrophotographic image forming apparatuses face issues with positional deviation of laser light on photosensitive drums, leading to image misalignment and increased downtime due to the need for separate detection and correction processes, which also result in larger apparatus sizes and higher costs.
Innovation Solution
An image forming apparatus with a scanning optical unit that includes a light source, rotary polygon mirror, and a detection unit to calculate and correct positional deviations of laser light on the photosensitive member, allowing for real-time correction during printing without increasing the apparatus size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a beam splitter is used to detect laser light position on the photosensitive drum, then position detection is enabled, but the amount of light emitted onto the photosensitive drum is reduced
Solution Approach 1:
The patent divides the detection function into two separate sensors: a first position detection sensor that detects the laser light position on the photosensitive drum surface, and a second position detection sensor that detects the position of reflected light from a reference surface. This segmentation allows simultaneous position detection without beam splitting, maintaining full light intensity for image formation while enabling accurate positional deviation measurement through comparison of the two sensor outputs.
2Measurement precision
If a marking area is provided outside the photosensitive surface for position detection, then laser light writing position can be detected, but the photosensitive drum length increases
Solution Approach 1:
The patent makes the photosensitive drum surface serve dual functions: it acts as both the image formation surface and the reference surface for position detection. The laser light position on the photosensitive drum is detected directly, and the same surface is used as the reference for comparison, eliminating the need for separate marking areas and maintaining the original drum dimensions.
3Measurement precision
If positional deviation detection is performed by forming a detection pattern image on the conveying body, then position deviation can be calculated, but toner is consumed and printing cannot be performed simultaneously
Solution Approach 1:
The patent enables continuous position detection during the printing process by using the laser light scanning system itself to detect positions on the photosensitive drum surface. The first position detection sensor and second position detection sensor continuously monitor laser light positions without interrupting the printing operation, allowing real-time deviation correction while maintaining continuous production.
4Device complexity
If the laser light position is not corrected in real-time, then the apparatus structure remains simple, but image position deviation occurs due to temperature rise
Solution Approach 1:
The patent implements a feedback control system where the first position detection sensor detects the actual laser light position on the photosensitive drum, the control unit calculates the positional deviation from the reference position detected by the second sensor, and the scanning optical unit adjusts the laser light position based on this feedback to correct deviations caused by temperature rise or mechanical drift.
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
The solution enables real-time correction of laser light positional deviations, reducing downtime and apparatus size, while maintaining efficient image formation without the need for additional detection patterns or larger components.
Implementation Method 1
laser light emitted from a light source based on an image signal has an optical path deflected by a rotary polygon mirror
Implementation Method 2
a detection unit which is arranged in a position facing the photosensitive member, and is configured to output positional information on the laser light, the detection unit including a detection portion into which the laser light reflected by the photosensitive member is incident
Data Source
AI summary
An image forming apparatus, including a photosensitive member, a scanning optical unit configured to scan the photosensitive member by laser light according to image information, a detection unit arranged in a position facing the photosensitive member and configured to output positional information on the laser light. The detection unit includes a detection portion into which the laser light reflected by the photosensitive member is incident, and a control unit configured to calculate a positional deviation amount of an irradiation position on the photosensitive member which is irradiated by the laser light based on the positional information output by the detection unit, and control the scanning optical unit to correct the positional deviation of the irradiation position of the laser light.