Optical Writing Device Light Uniformity Correction
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Solution Overview
Problem
Conventional optical writing devices face challenges in suppressing light amount differences along the main and sub scanning directions due to the optical characteristics of rod lens arrays, leading to uneven image density and requiring large dynamic ranges for correction circuits, which increases the complexity and cost of semiconductor elements.
Innovation Solution
An optical writing device with a correction unit that adjusts signal values for light-emitting elements and a control unit that manages light emission durations for different element arrays to eliminate light amount differences, reducing the dynamic range required for correction and simplifying the correction circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a rod lens array is used to collect light from two-dimensionally arranged light-emitting elements, then light collection and image formation are achieved, but light amount differences occur along the main scanning direction resulting in uneven image density
Solution Approach 1:
The patent applies local quality by assigning different light emission amounts to individual light-emitting elements based on their positional characteristics. The correction unit adjusts the driving current for each element according to a correction value that compensates for the specific light amount differences caused by the rod lens array's optical characteristics, thereby achieving uniform image density across different regions.
Solution Approach 2:
The patent changes the parameter of light emission amount for each light-emitting element to compensate for optical path differences. By varying the driving current parameters according to position-dependent correction values, the system counteracts the non-uniform light transmission characteristics of the rod lens array.
2Manufacturing precision
If correction values are applied to all light-emitting elements to compensate for light amount differences, then image density uniformity is improved, but the dynamic range of the correction circuit increases requiring more bits and larger circuit size
Solution Approach 1:
The patent applies partial correction by identifying and correcting only the significant light amount differences rather than applying full correction to all elements. By focusing correction on elements with larger deviations and using clustering to group elements with similar characteristics, the system achieves acceptable image density uniformity with reduced correction circuit dynamic range and smaller circuit size.
Solution Approach 2:
The patent segments the light-emitting elements into clusters based on their positional characteristics and light amount differences. By processing elements in groups rather than individually, the system reduces the overall dynamic range requirement for the correction circuit while maintaining correction effectiveness within each cluster.
3Illumination intensity
If light emission amounts are adjusted for all element arrays, then light amount differences along the sub scanning direction are reduced, but the correction complexity and required dynamic range increase
Solution Approach 1:
The patent applies partial correction along the sub-scanning direction by focusing on compensating for significant light amount differences between element arrays rather than achieving perfect uniformity. This selective correction approach reduces the overall correction complexity and dynamic range requirements while maintaining acceptable image quality.
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 reduces the dynamic range needed for correcting light amounts, resulting in a smaller and less costly correction circuit while maintaining accurate image formation by ensuring uniform light exposure across the photoreceptor.
Implementation Method 1
a rod lens array that collects light emitted by a plurality of light-emitting elements, and exposes a photoreceptor to the light
Implementation Method 2
a plurality of light-emitting elements 900 are arranged two-dimensionally
Data Source
AI summary
An optical writing device including light-emitting elements forming element arrays. The element arrays are each composed of light-emitting elements arranged in line in a main scanning direction, and reside at respective positions along a sub-scanning direction. A correction unit receives signal values in one-to-one correspondence with the light-emitting elements and performs correction to acquire corrected signal values each indicating a light amount of a corresponding light-emitting element. The correction is for eliminating a light amount difference in the main scanning direction occurring for each element array. A driving unit supplies driving currents to the light-emitting elements based on the corrected signal values, and a control unit performs a control of causing at least two element arrays to emit light for different durations within one main scanning period. The control is for eliminating a light amount difference in the sub scanning direction occurring between the at least two element arrays.