Laser Driver Bias Current Control for Optical Scanning
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Solution Overview
Problem
Existing optical scanning devices face challenges in accurately controlling laser light emission quantity due to variations in laser characteristics and lens transmittance, leading to degraded resolution and optical displacement at low target light quantities.
Innovation Solution
The optical scanning device incorporates a laser driver that adjusts the excess current over a bias current based on an input analog signal, with an offset value determiner setting an offset value for the analog signal based on the target light quantity, and a bias current setter controlling the bias current according to laser characteristics or lens transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed bias current is used in the laser driver, then the device complexity is reduced, but the manufacturing precision deteriorates due to variations in laser characteristics and lens transmittance
Solution Approach 1:
The patent implements dynamic bias current adjustment by introducing a bias current adjustment unit that modifies the bias current based on detected light quantity variations. This transforms the static fixed bias current system into a dynamic adaptive system that compensates for manufacturing variations in laser characteristics and lens transmittance, thereby improving manufacturing precision without significantly increasing device complexity
Solution Approach 2:
The patent employs feedback control by using a light quantity detector to monitor the actual laser output and feed this information back to the bias current adjustment unit. This closed-loop feedback mechanism enables automatic compensation for manufacturing variations, allowing the system to maintain precise light emission control while keeping the overall device structure relatively simple
2Speed
If the bias current is increased to reduce delay time, then the speed of laser response is improved, but the reliability deteriorates due to constant laser oscillation
Solution Approach 1:
The patent dynamically adjusts the bias current based on the actual light quantity detected, rather than using a fixed high bias current. This dynamic adjustment allows the bias current to be optimized for each operating condition, achieving fast response when needed while preventing constant laser oscillation by reducing the bias current when the target light quantity is low, thus improving reliability
Solution Approach 2:
The patent changes the bias current parameter adaptively based on detected light quantity variations and target light quantity requirements. By adjusting this critical parameter dynamically, the system achieves fast laser response when high speed is needed while preventing unwanted laser oscillation when the target light quantity is low, thereby resolving the contradiction between speed and reliability
3Device complexity
If a uniform offset value is applied to the analog signal, then the device complexity is reduced, but the manufacturing precision deteriorates due to defects in laser light emission quantity
Solution Approach 1:
The patent implements dynamic offset adjustment by introducing an offset adjustment unit that modifies the offset value based on detected light quantity variations. This transforms the static uniform offset system into a dynamic adaptive system that compensates for manufacturing variations in laser characteristics and lens transmittance, thereby improving manufacturing precision without significantly increasing device complexity
Solution Approach 2:
The patent employs feedback control by using a light quantity detector to monitor the actual laser output and feed this information back to the offset adjustment unit. This closed-loop feedback mechanism enables automatic compensation for manufacturing variations, allowing the system to maintain precise light emission control while keeping the overall signal processing structure relatively simple
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 ensures the required offset amount is secured, maintaining resolution at large target light quantities and preventing optical displacement, while avoiding constant laser oscillation due to individual and temperature variations.
Implementation Method 1
a laser light emitter 200a that emits laser beams
Data Source
AI summary
An optical scanning device includes a laser driver, an offset value determiner, a bias current setter, and a laser driver controller. The laser driver controls a laser light emitter to increase or decrease an excess of a current over a bias current in response to an input analog signal. The offset value determiner determines an offset value of the analog signal input to the laser driver based on a target light quantity of the laser light emitter. The bias current setter controls the bias current of the laser driver to a setting value in accordance with laser characteristics or lens transmittance of the laser light emitter. The laser driver controller controls a light emission quantity of the laser light emitter by inputting, to the laser driver, the analog signal offset based on a signal of the determined offset value.