Image Forming Apparatus Light Output Correction for Halftone Streak Elimination
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Solution Overview
Problem
Existing image forming apparatuses face challenges in maintaining consistent light output across solid-state light emitting elements, leading to vertical streaks in halftone images due to variations in beam diameter and tilt, which are exacerbated by different correction requirements for low and high gradation images.
Innovation Solution
An image forming apparatus that calculates a fourth correction coefficient based on first and second correction coefficients, adjusting light emission time according to image gradation to correct light output for each light emitting point, thereby aligning beam profiles and eliminating streaks across various gradations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the light amount is kept constant by adjusting the light emission time of each element, then the light output uniformity is improved, but vertical streaks occur in halftone images due to beam diameter variations
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting both light emission time and emission intensity of each solid-state light emitting element based on pre-stored correction data. The control unit modifies the drive signal parameters (duty cycle and amplitude) according to the element position and type, transforming the fixed parameter operation into a variable parameter system that compensates for beam diameter variations while maintaining uniform light output and eliminating vertical streaks in halftone images
2Shape
If spot diameter correction is applied to align beam diameter at specific beam height, then the beam profile uniformity is improved, but the correction conditions vary depending on device state making it difficult to maintain optimal performance
Solution Approach 1:
The patent implements preliminary action by pre-storing correction data (first and second correction values) for each solid-state light emitting element during the manufacturing phase. This correction data is calculated based on the element's position and characteristics, and stored in advance in the control unit. During actual operation, the control unit simply retrieves and applies the pre-computed correction values, eliminating the need for real-time complex calculations and adapting to various device states without requiring re-calibration
3Measurement precision
If two types of correction data are stored and a third correction value is calculated for each light emitting point, then the correction accuracy is improved, but the complexity of the correction system increases
Solution Approach 1:
The patent applies segmentation by dividing the correction system into independent element-level corrections. Instead of applying a single global correction, the system segments the correction process into individual correction values for each solid-state light emitting element based on its position and characteristics. The control unit stores and applies these segmented correction values independently, which simplifies the overall correction logic while maintaining high accuracy, as each element's specific characteristics are addressed individually without requiring complex inter-element coordination
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 corrects light output variations, eliminating white streaks in low gradation and color streaks in high gradation images, resulting in improved image formation with reduced density unevenness across a wide range of gradations.
Implementation Method 1
an exposure device that uses a solid-state head such as a liquid emitting diode (LED) or an organic light emitting diode (OLED)
Implementation Method 2
a latent image is formed on a photoconductor by irradiating the photoconductor with image light from an exposure device
Data Source
AI summary
An image forming apparatus equipped with an exposure device including a plurality of light emitting points, includes a photoconductor and a processor. The processor controls the light emission of each of the plurality of light emitting points of the exposure device based on the image to be formed. The processor calculates a fourth correction coefficient by changing a third correction coefficient, which is calculated based on a first correction coefficient for correcting a first physical quantity related to the exposure condition of the photoconductor by the light emitting point, and a second correction coefficient for correcting a second physical quantity related to the exposure condition of the photoconductor by the light emitting point, based on the light emission time set according to the gradation of the image to be formed, and corrects the light output of each of the plurality of light emitting points by the fourth correction coefficient.