LED Head Latent Image Shift Correction in Electrophotographic Printers
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Solution Overview
Problem
In electrophotographic printers using LED heads, the linearity of latent images in the main scanning direction is compromised due to alternating shifts in the sub-scanning direction caused by the rotational movement of the photoconductor, leading to misalignment and color shifts, especially when the light emitting elements are arranged in a staggered manner.
Innovation Solution
An image forming apparatus that includes a photoconductor and a light emitting unit with a generating unit to create correction data based on the configuration of the light emitting elements, their emission time, and the photoconductor's rotation speed, a correcting unit to adjust image data, and a control unit to synchronize light emission, ensuring the formation of a straight latent image by correcting shifts in the sub-scanning direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the light emitting element array is divided into multiple blocks and controlled to sequentially emit light in inverse directions, then misalignment at block boundaries is reduced, but linearity of the latent image in the main scanning direction is decreased
Solution Approach 1:
The patent applies preliminary anti-action by calculating and applying correction data in advance to counteract the expected shift in the sub-scanning direction. The correction amount is determined based on the sequential emission time of light emitting elements and the rotation speed of the photoconductor, allowing the system to pre-compensate for the alternating shifts caused by inverse directional emission control.
Solution Approach 2:
The patent changes the parameter of light emission timing for each light emitting element based on its position and the photoconductor's rotation speed. By adjusting the emission time parameter individually for elements in different blocks, the system compensates for the shifts caused by inverse directional control while maintaining the benefits of reduced misalignment at block boundaries.
2Device complexity
If light emitting elements are arranged in a staggered manner, then device complexity is reduced, but positional shifts in the sub-scanning direction increase
Solution Approach 1:
The patent compensates for positional shifts caused by staggered arrangement by changing the emission time parameter for each light emitting element. The correction amount is calculated based on the staggered position, sequential emission time, and photoconductor rotation speed, allowing the system to maintain positioning precision despite the simplified staggered structure.
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 effectively reduces positional shifts in the sub-scanning direction, maintaining linearity of the latent image and minimizing color shifts during printing, even with staggered light emitting elements, thereby improving the quality and consistency of the printed images.
Implementation Method 1
exposure is performed by use of an exposure head (hereinafter referred to as an LED head) provided with a light emitting element such as an LED (Light Emitting Diode)... forming a latent image by exposing a photoconductive drum
Data Source
AI summary
An image forming apparatus including a photoconductor and a light emitting unit further includes a generating unit configured to generate correction data used for correcting a shift in the sub-scanning direction of a latent image to be formed on the photoconductor; a correcting unit configured to correct image data based on the correction data; and a control unit configured to control light emission of the light emitting unit so as to form the latent image on the photoconductor. The generating unit is configured to generate the correction data based on configuration information of the light emitting unit, information indicating time required for causing a plurality of light emitting elements to emit light, and information indicating a rotation speed of the photoconductor.