Ghosting Compensation in Electrophotographic Printing via Laser Energy Control
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Solution Overview
Problem
Electro-photography printing devices experience ghost appearances due to memory of previous images, leading to variations in latent image development and increased print costs, especially in large-scale printing where seamless drums are difficult to implement.
Innovation Solution
Adjusting the laser writing energy in image areas to compensate for ghosting by increasing the size of developed dots and controlling the laser writing energy using dedicated software, pre-determined correlations, and closed-loop control based on iterative measurements of optical density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the same image is printed repeatedly at the same position, then productivity is improved through high-volume printing, but ghost appearances occur due to memory of previous images
Solution Approach 1:
The patent applies local quality by differentiating treatment between ex-image areas and ex-nonimage areas. The system selectively increases laser writing energy only in ex-image areas where ghosting occurs, while maintaining normal energy levels in ex-nonimage areas. This localized adjustment compensates for ghosting effects without unnecessarily increasing energy consumption across the entire printing surface.
Solution Approach 2:
The patent changes the laser writing energy parameter dynamically based on the printing history. When ghosting is detected in ex-image areas, the system increases the laser energy parameter for subsequent prints in those specific areas. This parameter adjustment compensates for the degraded surface properties caused by repeated printing, thereby eliminating ghost appearances while maintaining overall printing efficiency.
2Reliability
If laser writing energy is increased globally to compensate for ghosting, then print quality is improved, but energy consumption increases unnecessarily
Solution Approach 1:
The system implements local quality by selectively applying increased laser writing energy only to ex-image areas where ghosting is detected, rather than increasing energy across the entire printing surface. This localized approach maintains print quality in affected areas while avoiding unnecessary energy consumption in areas that do not require compensation.
Solution Approach 2:
The patent applies partial action by providing compensation only where needed (in ex-image areas with ghosting) rather than applying uniform compensation across all areas. The system adjusts laser energy selectively based on the specific location and severity of ghosting, thereby achieving the minimum necessary energy increase to maintain print quality without excessive energy consumption.
3Reliability
If seamless drums are used to avoid ghosting, then print quality is maintained, but device complexity increases and implementation becomes difficult in large-scale printing
Solution Approach 1:
Instead of requiring a complex seamless drum structure, the patent applies local quality by selectively adjusting laser writing energy in specific ex-image areas where ghosting occurs. This software-based local compensation approach achieves the same print quality improvement as seamless drums would provide, but without the mechanical complexity and implementation difficulties associated with seamless drum construction in large-scale printing systems.
Solution Approach 2:
The patent replaces the mechanical solution (seamless drum structure) with a software-based control system that dynamically adjusts laser writing energy. This substitution eliminates the need for complex mechanical modifications to the drum while achieving equivalent or superior ghosting compensation through intelligent energy management based on printing history and real-time monitoring.
4Reliability
If photoreceptor or blanket is replaced early to eliminate ghosting, then print quality is maintained, but print cost increases
Solution Approach 1:
The system performs preliminary action by detecting and compensating for ghosting effects before they become severe enough to require photoreceptor or blanket replacement. By continuously monitoring print quality and adjusting laser energy in advance, the system extends the operational life of these components while maintaining acceptable print quality, thereby avoiding the cost of premature replacement.
Solution Approach 2:
The patent implements feedback control by monitoring print output for ghosting effects and using this information to dynamically adjust laser writing energy. This closed-loop feedback system allows the printer to maintain print quality over extended periods by making real-time compensations, thereby delaying the need for expensive component replacement and reducing overall operating costs.
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
Effectively reduces ghost appearances by improving dot transfer and optical density in affected areas, extending the life of photoreceptor and blanket surfaces without requiring hardware upgrades, thus reducing print costs and maintaining print quality.
Implementation Method 1
The charged photoreceptor and/or photoconductive surface are exposed to a light image from, for example, a writing head laser that discharges specific areas on the photoconductive surface. This records an electrostatic latent image on the photoconductive surface.
Data Source
AI summary
A method of operating a printing system includes determining whether ghosting is expected on a photoreceptor and applying power to a laser applied to the photoreceptor based on whether the ghosting is expected.