Laser Driving Current Control for Uniform Image Density
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Solution Overview
Problem
Image forming apparatuses face challenges in achieving uniform image density due to variations in laser driving current along the scanning direction, leading to light quantity ununiformity and density variations in the main scanning direction, particularly in Over Field Scanner (OFS) optical systems.
Innovation Solution
An image forming apparatus is designed with a laser light emitting unit, a laser driving current controlling unit, and a laser driving signal adjusting unit, which continuously changes the laser driving current and adjusts the laser driving signal along the main scanning direction to correct light quantity ununiformity, ensuring uniform image density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an Over Field Scanner (OFS) optical system is used to increase scanning speed, then productivity is improved, but light quantity distribution uniformity deteriorates
Solution Approach 1:
The patent applies local quality by adjusting the laser driving current differently at different positions along the main scanning direction. Specifically, the laser driving current is increased at the end portion of the scanning direction where light quantity is reduced, and adjusted accordingly at the central portion, to achieve uniform light quantity distribution across the entire photosensitive surface while maintaining high scanning speed
Solution Approach 2:
The patent changes the parameter of laser driving current along the main scanning direction to correct light quantity ununiformity. By continuously adjusting the laser driving current based on the scanning position, the system compensates for the inherent light quantity distribution issues in OFS optical systems, achieving uniform image density while preserving the high productivity benefits
2Manufacturing precision
If the number of scanning lines is increased to improve image quality, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical adjustments in the optical system with an electrical control approach. Instead of modifying the physical optical path or adding complex mechanical components to correct light quantity distribution, the system uses software-based control to adjust laser driving current dynamically, achieving image density uniformity through electrical parameter modulation rather than mechanical complexity
3Manufacturing precision
If laser driving current is increased to compensate for light quantity loss at scanning end, then light quantity ununiformity is corrected, but heat generation increases
Solution Approach 1:
The patent applies dynamics by making the laser driving current adjustable and position-dependent rather than using a constant current. The laser driving current is dynamically changed along the main scanning direction, being higher at the end portion and adjusted at the central portion, allowing the system to compensate for light quantity loss while minimizing overall heat generation through precise, localized control
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 corrects variations in image density caused by differences in laser driving current, optimizing image quality by maintaining consistent light quantity across the scanning direction, thereby enhancing the overall image forming process.
Implementation Method 1
a laser light emitting unit configured to emit laser light on the basis of laser driving current and image data
Implementation Method 2
an optical system using an Over Field Scanner (OFS) method as a method of scanning the drum surface at a higher speed
Data Source
AI summary
An image forming apparatus in which a BD signal, which is a main-scanning reference signal, and image data are input to an image signal generating unit. Using a converting unit, main-scanning coordinate information, output from a main scanning coordinate measuring counter, and correction amounts, recorded in a correction amount LUT, are referred to, to convert a proper amount of image data. Here, the converting unit performs calculations in accordance with the main-scanning coordinate information, to obtain the image data of correction amounts that differ in accordance with coordinates. The correction amounts are in correspondence with different amounts of driving current in a main-scanning direction. Therefore, laser light emission, which provides a light quantity in accordance with the image data, is controlled.