Image Forming Apparatus Dither Pattern Control
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Solution Overview
Problem
Existing electrophotographic image forming technologies face issues with inconsistent toner amounts, leading to defective fixing, particularly when correction tables are generated based on output or input image data, resulting in images with toner amounts different from the target value.
Innovation Solution
The image forming apparatus controls the maximum gradation value of the toner image based on the repetition length of the dither pattern, ensuring that the maximum gradation value is adjusted accordingly, whether using a first dither pattern with a shorter length or a second dither pattern with a longer length, to stabilize toner amount and prevent defective fixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a correction table is generated based on output image data or input image data to control the toner amount, then the toner consumption is controlled uniformly, but an image having a toner amount different from the target value may be formed with respect to the maximum density value, resulting in defective fixing
Solution Approach 1:
The patent changes the parameter of maximum gradation value based on the dither pattern repetition length. When a dither pattern with a longer repetition length is used, the maximum gradation value is set to a lower value compared to when a dither pattern with a shorter repetition length is used. This parameter adjustment ensures that the toner amount is appropriately controlled regardless of the dither pattern type, preventing defective fixing while maintaining stable toner amount.
2Stability of the object's composition
If the maximum gradation value is controlled based on dither pattern repetition length, then the toner amount becomes consistent regardless of screen ruling, but the control complexity increases
Solution Approach 1:
The patent performs preliminary control by setting the maximum gradation value according to the dither pattern repetition length before image formation. The control unit determines the appropriate maximum gradation value in advance based on whether a first dither pattern (shorter repetition length) or second dither pattern (longer repetition length) is used, and applies this setting prior to actual toner deposition. This preliminary action ensures consistent toner amount without requiring complex real-time adjustments during the imaging process.
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 ensures a consistent toner amount on the photosensitive drum, regardless of the dither pattern's screen ruling, thereby preventing defective fixing and maintaining image quality.
Implementation Method 1
an exposure unit configured to expose a surface of the image bearing member to light to form an electrostatic latent image
Implementation Method 2
a developing member configured to develop the electrostatic latent image formed on the surface of the image bearing member by the exposure unit, by using toner, to form a toner image
Data Source
AI summary
An image forming apparatus includes an image bearing member, an exposure unit, a developing member, and a control unit. The exposure unit exposes a surface of the image bearing member to light to form an electrostatic latent image. The developing member develops the electrostatic latent image by using toner to form a toner image. In image formation based on input image data, the control unit uses the exposure unit to control a maximum gradation value of the toner image to be formed on the image bearing member surface, based on a repetition length of a dither pattern. The control unit performs control so that the maximum gradation value is larger in a case where a first dither pattern having a first length as the repetition length is used than where a second dither pattern having a second length longer than the first length as the repetition length is used.