LED Exposure Device Adjustment for Electrophotographic Printers
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Solution Overview
Problem
Electrophotographic printers using exposure devices with light-emitting diodes (LEDs) face issues with uneven optical density in printed images due to variations in LED light intensity, lens mechanism imperfections, and height differences, leading to suboptimal image quality.
Innovation Solution
A method and apparatus for adjusting the exposure device by energizing selected LEDs according to a selection scheme, measuring exposure intensity distribution, predicting toner area coverage distribution using a pre-established transfer function, and determining setting values for energy levels to achieve even optical density, which involves a selection and energizing module, a measuring module, and an adjusting module to automatically set energy levels for each LED.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LEDs are used in the exposure device, then productivity is improved through non-impact printing, but unevenness of optical density occurs due to LED light intensity variations and lens imperfections
Solution Approach 1:
The patent applies local quality by determining individual setting values for energy output levels of each light-emitting element based on its specific light intensity characteristics. Instead of uniform settings, each LED is adjusted locally to compensate for variations in light intensity, lens transparency, and height differences, thereby achieving uniform optical density across the printed image while maintaining high printing speed.
Solution Approach 2:
The patent changes the parameter of energy output level for each light-emitting element based on measured light intensity distributions and predicted toner area coverage. By adjusting the energy output parameter individually for each LED, the system compensates for manufacturing variations and optical imperfections, resolving the contradiction between high productivity and optical density uniformity.
2Manufacturing precision
If individual adjustment of each LED is performed, then optical density uniformity is improved, but device complexity increases due to multiple setting values required
Solution Approach 1:
The patent implements self-service by enabling the exposure device to automatically determine and store individual setting values for each light-emitting element through a systematic process. The device measures light intensity distributions, predicts toner area coverage using a transfer function, and calculates optimal energy output levels autonomously, reducing the need for manual adjustment while achieving uniform optical density.
Solution Approach 2:
The patent manages device complexity by systematically changing energy output parameters based on measured light intensity and predicted toner coverage. The method uses a transfer function to predict toner area coverage from light intensity distributions, enabling automated determination of setting values that balances optical density uniformity with manageable device complexity.
3Manufacturing precision
If multiple energy levels are applied to LEDs, then image quality with gradation is improved, but the complexity of energy level control increases
Solution Approach 1:
The patent applies local quality by determining individual setting values for energy output levels of each light-emitting element based on its specific light intensity characteristics. Instead of uniform settings, each LED is adjusted locally to compensate for variations in light intensity, lens transparency, and height differences, thereby achieving uniform optical density across the printed image while maintaining high printing speed.
Solution Approach 2:
The patent changes the parameter of energy output level for each light-emitting element based on measured light intensity distributions and predicted toner area coverage. By adjusting the energy output parameter individually for each LED, the system compensates for manufacturing variations and optical imperfections, resolving the contradiction between high productivity and optical density uniformity.
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 method achieves significantly reduced unevenness in optical density, ensuring more reliable setting values for energy levels, resulting in high evenness of printed images and minimizing banding effects.
Implementation Method 1
A plurality of light-emitting elements record latent images on a photosensitive member. An exposure device may be provided with an array of light-emitting elements such as light emitting diodes (LEDs).
Implementation Method 2
A lens mechanism such as a rod lens array (commercially available under the trade-marked name SELFOC) can be used in the printhead for focussing the light emitted by the LEDs on the photosensitive recording member.
Implementation Method 3
If a charge area development process is used, a light spot projected on the photosensitive member with a light intensity larger than a so-called print threshold intensity is discharging locally the photosensitive material and no toner is developed locally
Data Source
AI summary
A method of adjusting an exposure device suited for an electrophotographic printer, the exposure device includes a plurality of light-emitting elements. The method includes the steps of energizing selected light-emitting elements according to a selection scheme, using a pre-determined energy level for energizing each selected light-emitting element and obtaining a corresponding exposure intensity distribution from the exposure device. The method further includes the steps of predicting a toner area coverage distribution, based on the obtained exposure intensity distribution and on a pre-established transfer function, obtaining an attribute of the predicted toner area coverage distribution and determining the setting values for the energy levels for energizing each selected light-emitting element such that the obtained attribute becomes a target attribute.