Surface Emitting Element Array Light Control for Image Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electrophotographic image forming apparatuses using surface emitting elements in exposure heads face issues with variations in light emission, leading to defective images like streaks and unevenness, requiring complex circuitry for high-accuracy light adjustment and increased response speed, which complicates the system.
Innovation Solution
An image forming apparatus with a controller that adjusts drive current for each surface emitting element array chip to control light emission, using a light amount adjustment unit and medium tone processing to correct light variations with reduced image data, simplifying the circuitry and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a light amount adjustment unit is provided for all surface emitting elements and a light amount adjustment unit for each of the surface emitting elements, then light emission uniformity is improved, but circuit complexity increases and response speed requirements increase
Solution Approach 1:
The exposure head is divided into multiple array chips, each containing multiple surface emitting elements. A single light amount adjustment unit is provided for each array chip rather than for each individual element, segmenting the control function to reduce overall circuit complexity while maintaining light emission uniformity across all elements.
Solution Approach 2:
The light amount adjustment unit for each array chip serves multiple surface emitting elements simultaneously, making it a multi-functional component that controls light emission for all elements within its array chip without requiring separate dedicated units for each element.
2Measurement precision
If pulse width control using a triangle wave is performed in a multi-bit configuration, then light amount adjustment precision is improved, but a high-accuracy DA converter is required causing errors from heat and power supply voltage variations
Solution Approach 1:
The system changes the control parameter from pulse width modulation (PWM) using triangle waves to direct current amplitude control. This parameter change eliminates the need for high-accuracy DA converters and triangle wave generation circuits, reducing sensitivity to heat and power supply voltage variations while maintaining light amount adjustment precision.
3Manufacturing precision
If each pixel is corrected individually requiring switching of DAC output for each pixel, then light emission uniformity is improved, but response speed requirements increase and circuit becomes complicated
Solution Approach 1:
Instead of correcting each pixel individually, the system segments elements into array chips and applies correction at the array chip level. This segmentation reduces the number of correction operations required and eliminates the need for rapid DAC switching between pixels, maintaining uniformity while reducing response speed requirements.
Solution Approach 2:
The correction function is merged from the pixel level to the array chip level, where a single light amount adjustment unit controls multiple elements simultaneously. This merging reduces the total number of control operations and eliminates complex timing requirements for individual pixel correction.
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 variations between surface emitting elements using a smaller amount of image data, reducing circuit complexity and improving image quality by ensuring consistent light emission across the exposure head.
Implementation Method 1
The exposure head includes rows of light emitting elements arranged in a longitudinal direction of the photosensitive drum and a rod lens array configured to cause light beams from the rows of light emitting elements to form an image on the photosensitive drum. A known configuration of the LED or the organic EL element has a surface emitting shape
Implementation Method 2
a light emitting diode (LED) or an organic electro luminescence (EL) diode or element is used, for example
Implementation Method 3
a rod lens array configured to cause light beams from the rows of light emitting elements to form an image on the photosensitive drum
Implementation Method 4
expose the photosensitive member by the plurality of surface emitting elements
Data Source
AI summary
An image forming apparatus includes an exposure portion including a plurality of surface emitting elements configured to expose a photosensitive member, a drive unit configured to turn ON the surface emitting elements based on image information, and a light amount control unit configured to adjust a drive current value to control an amount of light to be emitted from the surface emitting elements; and a controller configured to output the image information to the exposure portion. The controller includes a light amount adjustment unit configured to correct the image information based on an adjustment value to adjust the amount of light to be emitted from the surface emitting elements and a medium tone processing unit configured to quantize the image information corrected by the light amount adjustment unit by error diffusion to reduce a number of tones in the image information.