Laser Power Control for Electro-Optical Readers
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Solution Overview
Problem
Existing electro-optical systems for reading bar code symbols face challenges in maintaining optimal laser power output while ensuring safety and reliability, as stringent safety standards limit maximum power and require effective monitoring of reader malfunctions.
Innovation Solution
Implementing laser power control arrangements that monitor and adjust the output power based on operating conditions, using a combination of monitor photodiodes and a microcontroller to deenergize the laser in case of preestablished settings not being met, and incorporating redundant photodiodes for enhanced safety and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser power output is increased to enhance reading performance, then reading efficiency is improved, but safety standards are violated
Solution Approach 1:
The laser power output is made dynamically adjustable rather than fixed at maximum. The system can adapt the power level based on reading conditions, allowing optimal performance when safe and reduced power when safety limits are approached, thus resolving the contradiction between reading efficiency and safety compliance
Solution Approach 2:
A feedback mechanism using monitor photodiodes continuously monitors laser output power and provides real-time information to the control circuitry. This feedback loop enables the system to automatically adjust or shut down the laser when safety thresholds are exceeded, maintaining both reading efficiency and safety standards
2Productivity
If laser power is increased to improve reading performance, then reading efficiency is enhanced, but reader malfunction risk increases
Solution Approach 1:
The system performs preliminary monitoring of laser operating conditions before malfunctions can occur. By continuously tracking parameters such as current, voltage, and output power, the system can detect early signs of malfunction and take preventive action, thereby maintaining both high reading efficiency and reliability
Solution Approach 2:
Redundant monitoring circuits and safety margins are built into the system beforehand to cushion against potential malfunctions. The dual photodiode monitoring system provides backup detection capabilities, ensuring that even if one monitoring path fails, the system can still detect and respond to abnormal conditions, thus maintaining reliability while operating at high power levels
3Reliability
If monitoring circuits are added to control laser power, then safety and reliability are improved, but device complexity increases
Solution Approach 1:
The monitor photodiodes serve multiple functions: they monitor laser output power for safety, provide feedback for power control, and can detect malfunction conditions. This multi-functionality reduces the need for separate dedicated monitoring components, thereby improving reliability without proportionally increasing device complexity
Solution Approach 2:
The monitoring system uses the laser's own output light (diverted through photodiodes) to monitor itself, rather than requiring external monitoring equipment. This self-monitoring approach integrates the monitoring function into the existing laser pathway, minimizing additional complexity while maintaining comprehensive safety and reliability monitoring
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 enhances reader performance by dynamically controlling laser power, ensures safety by discontinuing the laser beam in case of malfunctions, and provides reliable monitoring to prevent over-powering, thereby improving reading efficiency and safety.
Implementation Method 1
generating a laser beam having an output power upon energizing a laser
Implementation Method 2
The photodetector or sensor is positioned such that it has a field of view which ensures the capture of the reflected or scattered light, and converts the latter into an electrical analog signal
Implementation Method 3
the laser includes a laser diode, and a monitor photodiode for monitoring the output power of the laser
Data Source
AI summary
Laser power control arrangements interrupt power to a laser used in electro-optical readers upon detection of operating conditions not conforming to preestablished standards, and adjust power to the laser to enhance reader performance without violating prevalent safety standards. Dual monitors are used to independently monitor the output power of the laser.