VCSEL Array Thermal Management in TOF Depth Cameras
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Solution Overview
Problem
Time-of-flight (TOF) depth cameras face challenges in illuminating large environments effectively and achieving accurate depth measurements due to limitations in peak power and modulation speed of existing light sources, such as multiple LED or edge-emitting laser diodes, which result in reduced depth detection accuracy and increased optics costs.
Innovation Solution
A TOF depth camera configuration utilizing a vertical-cavity surface emitting laser (VCSEL) array device with a chip-on-submount (CoS) configuration, where the VCSEL array emits coherent light independently, providing high power output and sharp edge definitions, and is mounted on a printed circuit board (PCB) with a driver for efficient thermal management and reduced inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple LED or edge-emitting laser diodes are used as light sources, then the device complexity is reduced, but the peak power and modulation speed are insufficient resulting in reduced depth detection accuracy
Solution Approach 1:
The patent divides the light source into multiple VCSEL elements arranged in an array, where each element can be independently controlled. This segmentation allows the system to achieve high peak power and fast modulation speed through coordinated operation of individual elements, thereby improving depth detection accuracy while maintaining manageable device complexity through modular architecture
Solution Approach 2:
The patent introduces a heat spreading superstrate as an intermediary component between the VCSEL array and the mounting substrate. This superstrate not only manages thermal effects but also serves as a platform for positioning conductive elements that provide electrical isolation and signaling, thereby enabling high-performance operation without proportionally increasing overall device complexity
2Illumination intensity
If a high peak power light source is used to illuminate the entire environment, then the illumination intensity is improved, but the operating temperature increases
Solution Approach 1:
The heat spreading superstrate acts as a thermal intermediary that distributes heat away from the VCSEL elements across a larger area. This intermediary thermal management structure enables the system to maintain high illumination intensity from the VCSEL array while preventing excessive localized temperature rise, thus resolving the contradiction between illumination intensity and operating temperature
Solution Approach 2:
The patent transitions from point-source illumination to an array of multiple VCSEL elements distributed across a two-dimensional plane. This dimensional expansion allows the illumination function to be distributed across multiple elements, each operating at lower individual power levels, thereby maintaining total illumination intensity while reducing the thermal load on any single element
3Speed
If the VCSEL array device is mounted close to the driver, then the inductance is reduced, but the thermal management becomes more challenging
Solution Approach 1:
The heat spreading superstrate serves as a dual-function intermediary: it provides a mounting platform that enables close positioning of the VCSEL array to the driver for reduced inductance, while simultaneously functioning as a thermal management system that spreads heat away from the VCSEL elements. This intermediary structure resolves the contradiction between speed optimization and thermal management
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 VCSEL array device enhances illumination homogeneity, reduces operating temperature, and increases depth detection accuracy while minimizing optics costs and radiated emissions, offering improved performance over traditional light sources.
Implementation Method 1
a vertical-cavity surface emitting laser (VCSEL) array device... configured to generate illumination light
Implementation Method 2
a heat sink having a mounting surface... The VCSEL array device and the driver are mounted to the PCB
Implementation Method 3
The image sensor is configured to detect at least a portion of illumination light reflected from the image environment
Data Source
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AI summary
Various embodiments relating to a time-of-flight (TOF) depth camera including a vertical-cavity surface emitting laser (VCSEL) array device are disclosed. In one embodiment, a TOF depth camera includes a heat sink having a mounting surface, an illumination module mounted to the mounting surface, and an image sensor mounted to the mounting surface. The illumination module includes a printed circuit board (PCB), a VCSEL array device configured to generate illumination light to illuminate an image environment, and a driver configured to deliver an operating current to the VCSEL array device. The VCSEL array device and the driver are mounted to the PCB. The image sensor is configured to detect at least a portion of illumination light reflected from the image environment.