Laser Beam Correction for Image Density Uniformity
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Solution Overview
Problem
Existing electrophotographic image forming apparatuses face challenges in inhibiting nonuniformity in image density when using multiple beams of laser light with varying optical-path characteristics, particularly due to the lack of specific corrections for each beam's optical-path characteristic at the main scanning position on the photoconductor.
Innovation Solution
An image forming apparatus is designed with an optical scanner that emits multiple beams of laser light, featuring a pixel size calculator, light-quantity value quantizer, storage for conversion data, and a signal converter to adjust the laser light driving signals based on pixel size and light-quantity values, ensuring uniformity by correcting for each beam's optical-path characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a scanning lens having an fθ characteristic is used, then constant exposure duration per pixel is achieved, but the apparatus becomes large in size and high in cost
Solution Approach 1:
The patent divides the correction process into two independent segments: partial scaling factor correction and partial light-quantity correction. Each correction is calculated and applied separately for different scanning positions on the photoconductor, allowing complex optical correction to be achieved through multiple simple correction steps rather than requiring a complex fθ lens
Solution Approach 2:
The patent changes the parameters of the laser light by independently adjusting the exposure time (scaling factor) and light quantity (light-quantity correction) for different scanning positions. This allows the system to compensate for optical path variations without requiring an fθ lens, thereby reducing apparatus complexity while maintaining exposure uniformity
2Device complexity
If no scanning lens or scanning lens without fθ characteristic is used, then apparatus size and cost are reduced, but nonuniformity in image density occurs
Solution Approach 1:
The patent performs preliminary correction by calculating partial scaling factors and light-quantity correction values for each scanning position before the actual imaging process. This pre-calculation of correction parameters compensates for the lack of fθ characteristic, enabling uniform image density to be achieved without requiring a complex scanning lens
Solution Approach 2:
The system implements feedback correction by using calculated correction values based on the relationship between scanning positions and optical path characteristics. The correction data is stored and applied to adjust the laser output, creating a feedback mechanism that compensates for optical path variations and ensures uniform image density
3Manufacturing precision
If partial scaling factor correction and partial light-quantity correction are performed, then image density nonuniformity is inhibited, but the correction system becomes complex without specific descriptions for multiple beams
Solution Approach 1:
The patent creates a universal correction system that can handle multiple laser beams with different optical path characteristics using the same correction framework. The correction data storage and selection mechanism is designed to be multi-functional, accommodating any number of beams by storing correction data for each beam and selecting the appropriate correction set, thereby avoiding the need for separate correction systems for each beam
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 inhibits nonuniformity in image density by independently correcting the pixel size and light-quantity for each beam, resulting in improved image quality with multiple beams of laser light having variable moving velocities on the photoconductor.
Implementation Method 1
An electrophotographic-system image forming apparatus is equipped with an optical scanning unit (optical scanner) that irradiates the surface of a photoconductor with laser light, to form an electrostatic latent image
Data Source
AI summary
An image forming apparatus includes: a photoconductor; an optical scanner configured to cause a plurality of light beams to scan simultaneously on a surface of the photoconductor; a pixel size calculator configured to calculate a pixel size corresponding to a scanning position of each of the light beams; a light-quantity value quantization converter configured to quantize a light-quantity value corresponding to the scanning position of each of the light beams; a storage configured to store conversion data for conversion from image density data into a light beam driving signal; a signal converter configured to perform, with the conversion data, conversion from the image density data into the light beam driving signal; a selector configured to select the conversion data, according to the pixel size calculator and the light-quantity value quantization converter; and a light source configured to emit the plurality of light beams, based on driving data obtained through conversion by a driving data converter with the conversion data selected by the selector, in which a number of pieces of the conversion data correspond to a number resulting from a number of obtainable pixel size values×a number of obtainable light-quantity quantized values×a number of light beams.