Laser Diode Brightness Control via Temperature Compensation
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Solution Overview
Problem
Laser displays face challenges in maintaining accurate brightness control across a wide dynamic range due to temperature variations and self-heating effects, which affect the relationship between light output and operating current.
Innovation Solution
A measuring circuit measures reference voltage and current to determine the temperature and threshold current of the laser diode, allowing a driver to apply corrected operating currents, compensating for temperature effects and increasing the dynamic range by using look-up tables and current-voltage measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the dynamic range of the laser diode is increased to enhance image quality, then brightness control accuracy deteriorates due to temperature variations and self-heating effects
Solution Approach 1:
The patent implements a feedback mechanism where the measured light output is compared to the desired light output, and the operating current is adjusted based on the difference. This closed-loop control compensates for temperature variations and self-heating effects, maintaining brightness control accuracy across the extended dynamic range.
Solution Approach 2:
The patent changes the operating parameters (current, voltage, frequency) dynamically based on measured conditions. By monitoring the light output and adjusting the driving parameters in real-time, the system maintains accurate brightness control while operating across a wide dynamic range despite temperature changes.
2Ease of operation
If the relationship between current and light output is utilized for amplitude modulation, then brightness control is simplified, but accuracy deteriorates under temperature variations
Solution Approach 1:
The system maintains the simplicity of current-based amplitude modulation while adding a feedback loop that measures actual light output and adjusts the current accordingly. This preserves ease of operation while compensating for temperature-induced inaccuracies in the current-light output relationship.
Solution Approach 2:
The patent replaces reliance on the fixed electrical-optical conversion relationship with a measurement and control system that actively monitors and adjusts based on actual light output. This substitution of passive electrical control with active optical measurement and feedback maintains simplicity while improving accuracy.
3Stability of the object's composition
If self-heating effects are present during operation, then device stability improves through thermal equilibrium, but brightness control accuracy deteriorates
Solution Approach 1:
The feedback mechanism continuously measures light output and adjusts the operating current to compensate for self-heating effects. As the laser diode temperature changes during operation, the system dynamically corrects the current to maintain accurate brightness control while allowing thermal equilibrium to establish.
Solution Approach 2:
The system performs preliminary measurements and adjustments to account for expected self-heating effects. By anticipating temperature changes and pre-adjusting operating parameters or compensation factors, the system maintains accuracy throughout the thermal transition to equilibrium.
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 approach enables precise control of light output across a large dynamic range, reducing uncertainty and achieving accurate brightness levels with improved stability and accuracy, even under temperature variations.
Implementation Method 1
A laser display includes a laser diode that emits light having a desired intensity
Implementation Method 2
self-heating effects, which affect the relationship between light output and operating current
Data Source
AI summary
A laser display system 100 is configured to increase the dynamic range of a laser diode by modulating an operating current applied to the laser diode based on a desired sequence of brightness levels and a temperature of the laser diode. In some embodiments, a measuring circuit measures a voltage of the laser diode at a given current, which indirectly indicates the temperature of the laser diode, thus obviating the need for a direct measurement of temperature. In addition, in some embodiments, the measuring circuit identifies a threshold current of the laser diode based on a range of current values at which values of the current multiplied by the derivative of the voltage against the current vary relatively rapidly. By compensating for temperature effects and identifying the threshold current, a driver of the laser diode more precisely controls light output of the laser diode across an increased dynamic range.