Laser Diode Current Control for Dot Shape Stability
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Solution Overview
Problem
The light emitting response characteristics of laser light sources in electrophotographic-type image forming apparatuses are not constant due to varying temperature conditions and pulse width modulation (PWM) signal durations, leading to inconsistent dot shapes and challenging control system requirements.
Innovation Solution
An image forming apparatus that adjusts the driving current supplied to the laser light source based on its previous turned-on and turned-off times, using a correction amount generation unit to stabilize the light emitting response characteristics by controlling the driving current value in accordance with the driving state of the light source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the light source is turned off for a long duration, then energy consumption is reduced, but the light emitting response characteristics deteriorate when turned on again
Solution Approach 1:
The control unit performs preliminary action by adjusting the driving current in advance based on the turned-off time duration. Before the light source is actually turned on, the control unit has already determined the appropriate driving current value from a predetermined table, ensuring optimal response characteristics from the very beginning of the light emission cycle, eliminating the need for gradual ramp-up that would waste time and energy.
Solution Approach 2:
The invention applies dynamics by making the driving current adjustable and variable rather than fixed. The control unit dynamically selects different driving current values based on the specific turned-off time duration, allowing the system to adapt its electrical characteristics to match the temporal conditions of operation, thereby optimizing both energy efficiency and response performance.
2Manufacturing precision
If the control system responds quickly to maintain constant light emitting characteristics, then dot shape consistency is improved, but the response speed requirements become unrealistic for extremely short repeat cycles
Solution Approach 1:
The control unit performs preliminary calculation and determination of the driving current value based on the turned-off time duration before the actual light emission occurs. By pre-determining the appropriate current from a predetermined table, the control system eliminates the need for complex real-time calculations and feedback adjustments during the extremely short repeat cycles, making constant dot shape achievement feasible even at nanosecond-level timing.
Solution Approach 2:
The system implements feedback by monitoring the turned-off time duration and using this information to adjust the driving current accordingly. The control unit continuously tracks the temporal characteristics of the light source operation and feeds this information back into the driving current selection process, ensuring that the light emitting response characteristics remain constant despite varying on/off patterns.
3Illumination intensity
If the driving current is increased to improve light emitting response, then light intensity is improved, but the light emitting response characteristics become dependent on previous driving states
Solution Approach 1:
The invention applies parameter changes by systematically varying the driving current parameter based on the turned-off time duration. Instead of using a fixed driving current, the control unit selects from a range of current values stored in a predetermined table, each optimized for specific temporal conditions. This allows the system to maintain optimal light intensity while compensating for the effects of previous driving states on the light emitting response characteristics.
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 stabilizes the shapes of dots by improving the light emitting response characteristics, ensuring consistent dot formation even under varying conditions, and reduces the unrealistic response speed demands on the control system.
Implementation Method 1
a light source that turns on in response to a driving current supplied based on image data
Data Source
AI summary
An image forming apparatus comprises a light source, a photosensitive member and a control unit. The light source turns on in response to a driving current supplied based on image data. An electrostatic latent image is formed on the photosensitive member by exposing the photosensitive member to a light beam output from the light source turned on. The control unit controls the value of the driving current supplied to the light source in accordance with a driving state of the light source so that the value of the driving current supplied to the light source differs and changes with the passage of time in accordance with the driving state of the light source prior to the driving current being supplied to the light source.