Print Head Light Emission Control for Color Shift Correction
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Solution Overview
Problem
In electrophotographic printers, slight displacement of print heads during mounting leads to image displacement and color shift issues in the main scanning direction, affecting print quality.
Innovation Solution
A multi-function peripheral (MFP) image forming apparatus with a sensor to detect color shift, a processor to set correction values, and an image forming unit that controls light emission of print heads based on displacement and color shift data to ensure image alignment within a valid image area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-precision positioning is used to mount print heads, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent performs preliminary measurement of the actual positions of light emitting elements during or after manufacturing, and stores this position information in a lookup table. This preliminary action allows the system to compensate for positioning errors without requiring complex real-time adjustment mechanisms, thus improving manufacturing precision while avoiding increased device complexity.
Solution Approach 2:
The patent replaces complex mechanical positioning adjustment systems with an optical control approach. Instead of mechanically adjusting the print head positions during operation, the system uses software-based light emission control (turning on/off specific light emitting elements) to achieve the desired image positioning, thereby eliminating the need for complex mechanical adjustment mechanisms.
2Productivity
If multiple print heads are used for color printing, then productivity is improved, but manufacturing precision deteriorates due to cumulative displacement
Solution Approach 1:
The patent implements a feedback mechanism where the actual positions of light emitting elements in multiple print heads are measured and stored in a lookup table. During printing, the control unit refers to this pre-stored position information to accurately control the light emission timing and intensity of each print head, ensuring proper image alignment even when print heads are slightly displaced during manufacturing. This feedback approach maintains manufacturing precision while allowing high productivity through parallel processing.
Solution Approach 2:
The patent applies local quality control by individually measuring and controlling the position characteristics of each light emitting element in each print head. Instead of assuming uniform positioning across all print heads, the system tailors the control parameters for each specific element based on its actual measured position, thereby maintaining high image alignment precision while using multiple print heads for improved productivity.
3Manufacturing precision
If light emission control is implemented to correct displacement, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent performs preliminary measurement of light emitting element positions and stores this data in a lookup table during or after manufacturing. This pre-computed position information is then used during normal printing operations without requiring complex real-time measurement or adjustment systems. By performing the measurement action in advance, the patent improves image position accuracy while avoiding the complexity of continuous adaptive control systems.
Solution Approach 2:
The patent creates a digital copy (lookup table) of the actual light emitting element positions during manufacturing. This copied position information is then referenced during printing operations to control light emission, eliminating the need for complex real-time position sensing and adjustment mechanisms. The lookup table serves as a simplified representation of the physical positioning characteristics, reducing control system complexity while maintaining manufacturing precision.
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 effectively reduces image displacement and color shift, ensuring high-quality prints by adjusting light emission patterns according to detected displacement and color shift amounts, even when print heads are not precisely aligned.
Implementation Method 1
The print head includes a plurality of light emitting elements such as a light emitting diode (LED) or an organic light emitting diode (OLED)
Implementation Method 2
The print head includes a plurality of light emitting elements such as a light emitting diode (LED) or an organic light emitting diode (OLED)
Implementation Method 3
A photoconductive drum is exposed to the light output from the plurality of light emitting elements, a latent image is formed on the photoconductive drum
Data Source
AI summary
An image forming apparatus includes a plurality of print heads, a sensor, a processor, and an image forming unit. The plurality of print heads are arranged in parallel. The sensor detects a color shift amount of each color to be printed by the plurality of print heads in a main scanning direction based on an output result of a test pattern by the plurality of print heads. The processor sets a color shift correction value for correcting the color shift amount on the basis of a color having a largest color shift amount. The processor controls light emission of the plurality of print heads based on the color shift correction value and image data. The image forming unit forms an image based on the image data on a sheet by light emission of the plurality of print heads.