Optical Encoder LED Current Regulation for Light Degradation
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Solution Overview
Problem
Optical encoder systems are susceptible to light degradation due to reduced brightness over time and contamination, leading to decreased performance as the current generated by photodetectors decreases.
Innovation Solution
An LED current regulation system that includes a light emitter regulating circuit with analog multipliers, a summing circuit, and a comparator to detect light degradation and adjust the LED current in real-time, enhancing light intensity by comparing sinusoidal and cosinusoidal detector signals to generate a regulating signal for the light emitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the light emitter operates continuously in the encoder system, then the encoder can perform motion detection, but the brightness of the light emitter deteriorates over time due to light degradation and contamination
Solution Approach 1:
The patent implements a feedback mechanism where the photodetector continuously monitors the light intensity from the LED, and this information is fed back to a regulating circuit that adjusts the LED current accordingly. This closed-loop feedback system automatically compensates for LED brightness degradation over time, allowing continuous encoder operation while maintaining stable light intensity without manual intervention
Solution Approach 2:
The patent dynamically changes the operating parameters of the LED by adjusting its current based on detected brightness levels. The regulating circuit modifies the LED current parameter in real-time to compensate for degradation, thereby maintaining constant light output intensity despite prolonged operation and contamination
2Ease of manufacture
If contaminants accumulate on the light emitter or lens, then the brightness of the light emitter decreases, but the encoder system structure remains simple
Solution Approach 1:
The patent uses a feedback-based automatic compensation system where the photodetector monitors light intensity reductions caused by contamination and signals the regulating circuit to increase LED current. This approach maintains brightness without adding complex mechanical cleaning mechanisms or filters, preserving encoder simplicity while compensating for contamination effects
Solution Approach 2:
The encoder system performs self-diagnosis and self-correction by using the photodetector to detect brightness changes and automatically adjusting LED current through the regulating circuit. This self-service mechanism compensates for contamination without requiring external maintenance or complex additional components
3Reliability
If the photodetector current decreases due to light degradation, then the encoder performance deteriorates, but adding a regulation system increases device complexity
Solution Approach 1:
The patent implements a feedback loop where the photodetector output signal is directly used to control the LED current regulation. This feedback mechanism ensures that as long as some light reaches the photodetector, the system can automatically adjust and maintain reliable encoder performance without requiring complex external control systems
Solution Approach 2:
The patent makes the photodetector serve dual functions: it acts as both the primary sensor for position detection and as the monitor for LED brightness regulation. This multi-functionality eliminates the need for separate monitoring components, reducing overall device complexity while maintaining reliable encoder performance through automatic compensation
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 system effectively compensates for light degradation by boosting LED brightness, maintaining encoder performance and overcoming issues related to reduced signal photocurrents, thereby ensuring consistent motion detection accuracy.
Implementation Method 1
a light emitter configured to emit a collimated beam of light
Implementation Method 2
The light beam is interrupted by the encoder disk as the encoder disk moves
Implementation Method 3
The photodetectors detect these light patterns to generate corresponding output signals
Data Source
AI summary
An LED current regulator can regulate an LED current of an encoder system. The LED current regulator may comprise a first analog multiplier and a second analog multiplier. Each of the first and second analog multipliers may be configured to receive respective photodetector output signals, characterized by a peak-to-peak voltage, Vpp, and may be configured to generate respective first and second multiplier output signals. The first and second multiplier output signals may be combined to produce a first DC level, which may be representative of the peak-to-peak voltage, Vpp, of the photodetector output signals.