Laser Driving Unit Bias Current Control for Tone Reproduction
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Solution Overview
Problem
Conventional semiconductor laser driving circuits face challenges in achieving high-speed operation and accurate tone reproduction due to light emission delays and inconsistencies in tone reproduction and color registration, particularly when using red or ultraviolet lasers, which require longer times to reach carrier concentration, and are prone to banding noise and low tone reproduction issues.
Innovation Solution
A laser driving unit that includes a light detecting part to adjust the driving current based on the light emission state of each light source, using a combination of bias, threshold, modulation, and overshoot currents to optimize light emission, with an auxiliary driving current generator and set part to correct for differences in light emission among multiple light sources, ensuring a high-speed and accurate optical waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a zero-biased semiconductor laser driving circuit is used, then the extinction ratio is improved, but light emission delay occurs
Solution Approach 1:
The patent applies preliminary action by setting the semiconductor laser to a biased state before the actual light emission is needed. The bias current is applied in advance to generate sufficient carrier concentration, so that when the light emission signal arrives, the laser can immediately oscillate without delay. This resolves the contradiction by preparing the system in advance to achieve both low extinction ratio and fast response.
2Loss of time
If a biased semiconductor laser driving circuit is used, then light emission delay is eliminated, but banding noise appears in the background
Solution Approach 1:
The patent applies local quality by using different bias current levels for different operational regions. During background printing areas, a lower bias current is used to minimize light emission and prevent banding noise, while during active light emission periods, the bias current is increased to ensure immediate laser oscillation. This spatial-temporal differentiation resolves the contradiction between eliminating delay and preventing noise.
3Manufacturing precision
If red or ultraviolet semiconductor lasers are used to improve resolution, then manufacturing precision is improved, but light emission delay increases
Solution Approach 1:
The patent applies preliminary action by pre-applying bias current to red and ultraviolet semiconductor lasers before light emission is required. Since these lasers have longer carrier generation times compared to conventional lasers, the bias current is applied in advance to ensure sufficient carrier concentration is built up, enabling immediate laser oscillation when the emission signal arrives, thus maintaining both high resolution and fast response.
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 reduces light emission delays, improves tone reproduction accuracy, and minimizes banding noise, enabling high-resolution image formation with consistent color registration across multiple light sources.
Implementation Method 1
a light detecting part (2) to detect light emissions from the plurality of light sources
Data Source
AI summary
A laser driving unit drives a semiconductor laser apparatus including a plurality of light sources, includes a light detecting part to detect light emissions from the light sources, a driving current generator to generate a driving current based on an input signal, an auxiliary driving current generator to generate an auxiliary driving current in an initial time period of an ON-time of the driving current, and an auxiliary current set part to set an auxiliary amount of the auxiliary driving current to be added to the driving current, for each of the light sources, based on a difference between the light emissions detected by the light detecting part and a target light emission of the light sources.