Laser Driver Current Control for Electrophotographic Print Stability
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Solution Overview
Problem
Electrophotographic devices face challenges in maintaining accurate laser power control due to inherent imprecision in scanning systems, leading to bow and skew in scan paths and nonlinearity in spacing between print elements, which complicates the reliable production of short video pulses as print rates increase.
Innovation Solution
A laser driver system comprising multiple current sources, including a bias current source and switched current sources, with a control system that adjusts the magnitudes of these sources based on output power error measures to converge and stabilize the laser output power over time, using differential efficiency and scalar constants to manage the current sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If scan rate is increased to improve printed page rates, then productivity is improved, but the time available to write each slice of each Pel decreases, making it difficult to reliably produce short video pulses
Solution Approach 1:
The laser driver circuit divides the current control into multiple independent current sources (first current source, second current source, third current source) that can be selectively activated. This segmentation allows the system to maintain reliable current control even at high scan rates by independently managing different current components rather than relying on a single complex control mechanism.
Solution Approach 2:
The circuit pre-configures multiple current sources with their respective control logic ready for rapid switching. By having the current sources and control circuitry prepared in advance, the system can immediately respond to scan rate changes and produce accurate video pulses without delay, ensuring reliable operation at increased printed page rates.
2Manufacturing precision
If multiple current sources are added to improve laser power control accuracy, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple current sources (first, second, and third current sources) into a single integrated laser driver circuit that controls all sources through a unified control mechanism. This merging approach maintains manufacturing precision by providing accurate laser power control while reducing device complexity compared to having separate control circuits for each current source.
Solution Approach 2:
The laser driver circuit is designed with multi-functionality, where a single control system manages multiple current sources that can be selectively activated based on printing requirements. This universal control approach achieves high manufacturing precision through flexible current management without proportionally increasing device complexity, as the same control infrastructure serves multiple functions.
Data Source
AI summary
Laser driver systems and methods are provided for controlling a laser driver coupled to a suitable laser source. The laser driver comprises a plurality of current sources, including at least one bias current source and at least two switched current sources. To control the laser driver, a laser power control signal is provided for each switched current source that corresponds to a desired laser output power. An output power error measure is defined based upon an error between a measured laser output power and the desired laser output power for each switched current source and a control system is characterized in which the output power error measures combine to change a magnitude of each of the switched current sources and the bias current source(s) such that the output power error measures converge over time.