Rod Lens Array Symmetry Control for Print Streak Reduction
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Solution Overview
Problem
Image forming apparatuses using electrophotographic methods often suffer from streaks and uneven density in images due to variations in optical characteristics between rod lenses in the lens array, leading to suboptimal print quality.
Innovation Solution
The exposure unit is configured to ensure a symmetric light amount distribution by adjusting the distance between LED elements and rod lenses, allowing for a higher symmetric property of the light amount distribution, which suppresses streak-form patterns and uneven density, thereby improving print quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If variations in optical characteristics between rod lenses are present, then the lens array can be manufactured with standard precision, but streaks and uneven density occur in the formed image
Solution Approach 1:
The patent applies local quality by individually adjusting the position of each rod lens along the optical axis to compensate for its specific optical characteristics. Each rod lens is positioned at a different axial position (first axial position, second axial position, or third axial position) based on its measured optical properties, ensuring uniform light distribution across the photosensitive drum despite variations in manufacturing precision.
2Device complexity
If rod lenses are positioned with standard tolerance, then device assembly is simplified, but unintentional bias in exposure amount distribution occurs
Solution Approach 1:
The patent implements preliminary action by measuring the optical characteristics of each rod lens before final assembly, and pre-determining the optimal axial position for each lens based on its measured properties. This preliminary characterization and positioning planning ensures that when the lens array is assembled, the exposure amount distribution is uniformly controlled, preventing unintentional bias while maintaining manageable assembly complexity through systematic positioning.
3Reliability
If uniform light distribution is achieved through precise lens positioning, then image quality is improved, but measurement and adjustment complexity increases
Solution Approach 1:
The patent applies feedback by measuring the actual optical characteristics of each rod lens (such as focal length and aberration properties) and using this measurement information to determine the appropriate axial position for each lens. This closed-loop approach ensures that the light distribution becomes uniformly controlled based on real optical data, improving image quality while managing measurement complexity through targeted optical measurements rather than comprehensive characterization.
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 configuration ensures reduced unintentional bias in exposure amount distribution, resulting in improved image quality with reduced streaks and density unevenness, enhancing the overall print quality of the images formed.
Implementation Method 1
The exposure unit may include light-emitting elements such as light-emitting diode (LED) elements and a lens array
Implementation Method 2
Each of the rod lenses 11 focuses a light beam 30L emitted from the LED element 30 to be output from the end surface 12A as a light beam 11L
Implementation Method 3
Each of the rod lenses 11 focuses a light beam 30L emitted from the LED element 30 to be output from the end surface 12A as a light beam 11L
Implementation Method 4
a light beam 30L emitted from the LED element 30 enters the rod lens 11, and the rod lens 11 focuses the light beam 30L
Data Source
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AI summary
An exposure unit (3) includes a light-emitting element array (300) and a lens array (1). The light-emitting element array (300) includes a plurality of light-emitting elements (30) that are disposed in a first direction (X) and each emit a light beam (30L). The lens array (1) faces the light-emitting element array (300) in a second direction (Z) that is orthogonal to the first direction (X), and focuses the light beams (30L) emitted from the respective light-emitting elements (30). The following expression [3] is satisfied. A symmetric property (S), determined from the following expression [1], of a light amount distribution (E(X)) in the first direction (X) of at least one of the light beams (11L) focused by the lens array (1) satisfies the following expression [2]. S=HL−HR/XE/2 0≤S≤0.65 Lo≠LB