Light Source Control for Electrophotographic Imaging
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Solution Overview
Problem
Existing light source control systems for electrophotographic image forming apparatuses face challenges in correcting unevenness of electric potential and illumination distribution due to rapid changes, leading to decreased image quality, especially with photoconductors having uneven thin film thickness and multi-beam laser systems with varying illumination patterns.
Innovation Solution
A light source control apparatus that stores drive control data at multiple positions, generates interpolation data between these points, and uses a low-pass filter with a higher cut-off frequency than sampling frequency, allowing for improved tracking and correction of electric potential and illumination distribution without increasing storage capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of measurement points is increased to correct rapid changes in illumination distribution, then the correction precision is improved, but the storage capacity requirement increases
Solution Approach 1:
The patent divides the scanning region into multiple regions and performs separate correction for each region. By segmenting the correction task, the system can achieve high correction precision for rapid illumination changes without needing to store data for every single point, thus reducing overall storage requirements while maintaining measurement precision.
Solution Approach 2:
The patent applies partial correction by focusing computational resources on regions with rapid illumination changes rather than uniformly processing all areas. This allows the system to achieve effective correction where needed most without the storage overhead of processing every point at full resolution.
2Stability of the object's composition
If a low-pass filter with low cut-off frequency is used to smooth illumination distribution, then noise is reduced, but the tracking of rapid changes becomes poor
Solution Approach 1:
The patent dynamically adjusts the cut-off frequency of the low-pass filter based on the local characteristics of illumination distribution. In regions with rapid changes, a higher cut-off frequency is used to maintain tracking speed, while in stable regions, a lower cut-off frequency provides better noise reduction. This dynamic adaptation resolves the contradiction between stability and speed.
Solution Approach 2:
Different filtering characteristics are applied to different regions of the scanning area. Regions with rapid illumination changes receive filtering with higher cut-off frequencies to preserve tracking capability, while uniform regions receive stronger filtering for noise reduction. This local differentiation allows simultaneous optimization of both noise reduction and tracking performance.
3Speed
If the cut-off frequency of the low-pass filter is increased to improve tracking, then the tracking of rapid changes is improved, but noise increases
Solution Approach 1:
The system dynamically adjusts the cut-off frequency based on the local spatial frequency content of the illumination distribution. Where rapid changes are detected, higher cut-off frequencies are applied to maintain tracking. In smoother regions, lower cut-off frequencies reduce noise. This dynamic adjustment resolves the trade-off between tracking speed and noise level.
4Stability of the object's composition
If APC control is performed for each scan to maintain fixed light quantity, then the light emission stability is improved, but the response to rapid illumination changes is delayed
Solution Approach 1:
The patent pre-calculates correction data for multiple regions before actual scanning occurs. By preparing the correction map in advance, the system maintains APC stability while enabling rapid response during scanning without real-time computational delays. The preliminary action resolves the contradiction between stability and response speed.
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 corrects uneven electric potential and illumination distribution, resulting in high-quality images even with photoconductors having rapid changes in electric potential or laser optical systems with rapid illumination changes, without the need for increased storage or control data.
Implementation Method 1
a low-pass filter with a higher cut-off frequency than sampling frequency, allowing for improved tracking and correction of electric potential and illumination distribution
Implementation Method 2
a laser chip constituted by one laser and one photodiode sensor... the light-emitting characteristic of the laser is improved... the amount of bias current is automatically controlled
Implementation Method 3
an output signal from the PD sensor is inputted to an I/V converter, amplified by an amplifier, and inputted as a signal to an APC circuit
Data Source
AI summary
A light source control apparatus for controlling the output of a light source for forming an electrostatic latent image on an image carrying member in an electrophotographic image forming apparatus, the light source control apparatus according to the present invention including a storing unit that stores first drive control data of the light source on two or more positions of the image carrying member, an interpolating that generates second drive control data on at least one interpolation position between the two or more positions based on the first drive control data, a digital-analog converting unit that converts the first and second drive control data to an analog signal, a low-pass filter that cuts a high-frequency component of the analog signal outputted from the digital-analog converting unit, and a driving unit that drives the light source in response to the analog signal from which the high-frequency component has been cut by the low-pass filter, wherein the low-pass filter has a cut-off frequency higher than a frequency for sampling on the two or more adjacent positions on the image carrying member and lower than a frequency for sampling on the two or more positions and the interpolation position.