Color Misregistration Correction Using Composite Toner Patterns
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Solution Overview
Problem
Electrophotographic image forming apparatuses face challenges in accurately detecting color misregistration due to variations in the surface state of the intermediate transfer member, which affects the reflection state and makes it difficult to set appropriate threshold values for digital signal conversion, especially when detecting achromatic toner images like black toner images with low reflectance.
Innovation Solution
The apparatus includes a detection unit that forms a pattern image with multiple detection images of different colors on the intermediate transfer member, allowing the controller to determine adjustment values for image write start timing based on detected color misregistration, using a composite toner pattern that includes a black toner image superimposed on a chromatic toner image to facilitate detection and set appropriate threshold values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a black toner image with low reflectance is formed on the intermediate transfer member for color misregistration detection, then the detection sensitivity for black color is improved, but the optical sensor has difficulty in accurately detecting the pattern image due to low reflected light amount
Solution Approach 1:
A yellow toner image is formed as an underlying layer on the intermediate transfer member before forming the black measurement image. This yellow background serves as an intermediary that enhances the reflectance of the black measurement image, allowing the optical sensor to detect the pattern image accurately while maintaining the low reflectance characteristics of black toner for color misregistration detection
Solution Approach 2:
The measurement pattern is formed as a composite structure with a yellow toner image layer and a black measurement image layer superimposed on it. This composite structure combines the high reflectance of yellow toner with the low reflectance of black toner, creating a pattern that provides sufficient reflected light for optical sensor detection while maintaining the ability to detect black color misregistration
2Ease of operation
If the threshold value for converting analog signal to digital signal is set based on a fixed value, then the conversion process is simple, but the position of the pattern image cannot be detected accurately when the reflection state of the intermediate transfer member changes
Solution Approach 1:
The system automatically adjusts the threshold value based on feedback from the optical sensor's detection of the yellow toner image reflectance. The controller sets the threshold value dynamically according to the actual reflection state of the intermediate transfer member, ensuring accurate pattern image position detection while maintaining simple operation through automated adjustment
Solution Approach 2:
The yellow toner image is formed in advance as a background layer before the black measurement image is formed. This preliminary action creates a stable reference reflectance level that enables accurate threshold value setting and pattern detection, compensating for variations in the intermediate transfer member's surface state
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 solution enables accurate detection and correction of color misregistration, improving image quality by effectively handling variations in the intermediate transfer member's surface state and ensuring precise positioning of toner images, even when forming achromatic images.
Implementation Method 1
The optical sensor emits light from the light emitting unit toward the image bearing member and the pattern image on the image bearing member. The light receiving unit receives the reflected light.
Data Source
AI summary
An image forming apparatus includes a plurality of image forming units, an intermediate transfer member, a detection unit, and a controller. The controller is configured to control the plurality of image forming units to form, on the intermediate transfer member, a pattern image including a first detection image having a reference color among the plurality of detection images and a second detection image having another color among the plurality of detection images. The first detection image and the second detection image are superimposed on a predetermined detection image. The controller is configured to control the detection unit to detect the amount of color misregistration which is related to a relative position of the first detection image and the second detection image, and to determine an adjustment value for adjusting an image write start timing of the other color different from the reference color.