Laser Diode Array Non-Uniform Spacing for Thermal Management
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Solution Overview
Problem
Current range imaging systems face reliability issues due to the limited lifespan of laser diodes and LEDs, which affect the performance of time-of-flight cameras, especially in applications requiring consistent illumination over tens of thousands of hours.
Innovation Solution
An array of laser diode emitters on a common semiconductor substrate is used, with non-uniform spacing to reduce thermal gradients and provide redundancy, allowing the remaining emitters to maintain output power and accuracy even if one emitter fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single laser diode or LED is used for illumination, then the device structure is simple, but the reliability is low due to limited lifespan and single point of failure
Solution Approach 1:
The illumination source is segmented into multiple laser diode emitters arranged in an array on a common semiconductor substrate. Each emitter functions as an independent unit, so that if one fails, the others continue to provide illumination, thereby improving reliability while managing complexity through modular organization.
Solution Approach 2:
Multiple laser diode emitters are merged into a single array structure on a common semiconductor substrate, sharing common control and mounting infrastructure. This combining approach improves reliability through redundancy while avoiding the full complexity of completely independent systems.
2Reliability
If multiple laser diode emitters are used in an array, then the reliability is improved through redundancy, but the thermal gradients increase causing wavelength spread
Solution Approach 1:
The laser diode emitters are non-uniformly spaced with tighter spacing at the edges and wider spacing at the center. This local variation in spacing compensates for thermal gradients, as edge emitters experience less thermal accumulation and center emitters experience more, thereby reducing overall wavelength spread across the array.
3Ease of manufacture
If uniform spacing is used for laser diode emitters, then the manufacturing is easier, but the thermal gradients cause increased wavelength spread
Solution Approach 1:
The laser diode emitters are arranged with non-uniform spacing rather than uniform spacing. The asymmetric spacing pattern, with tighter spacing at edges and wider spacing at center, is specifically designed to compensate for thermal gradient effects, improving wavelength consistency across the array despite the increased manufacturing complexity.
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 enhances the reliability and longevity of the illumination source, ensuring consistent performance and extended operational life of time-of-flight cameras by distributing the load across multiple emitters and minimizing thermal effects.
Implementation Method 1
The illuminator comprises a laser diode array including a plurality of laser diode emitters on a common semiconductor substrate
Implementation Method 2
measuring, for every pixel of the image, of the time that it takes light to propagate from a light source to the object and back to the detector
Implementation Method 3
an optical camera for time-gated or phase-sensitive imaging of the object illuminated with the illuminator
Data Source
AI summary
An array of laser diode emitters is used as an illumination source for a range imaging system. The laser diode emitters are disposed on a common substrate. When one of the emitters fails, the remaining emitters emit enough light to meet the output optical power specification. The emitters can be disposed with a tight spacing. The tight spacing facilitates packaging of the entire array into a compact single package on a common heat sink.