Abstract
The market for wearable devices such as smart watches and smart glasses continues to grow rapidly. Smart glasses are attracting particular attention because they offer convenient features such as hands-free augmented reality (AR). Since smart glasses directly touch the face and head, the device with high temperature has a detrimental effect on human physical health. This paper presents a thermal network model in a steady state condition and thermal countermeasure methods for thermal management of future smart glasses. It is accomplished by disassembling the state by wearing smart glasses into some parts, creating the equivalent thermal resistance circuit for each part, approximating heat-generating components such as integrated circuits (ICs) to simple physical structures, setting power consumption to the heat sources, and providing heat transfer coefficients of natural convection in air. The average temperature difference between the thermal network model and a commercial thermal solver is 0.9 °C when the maximum temperature is 62 °C. Results of an experiment using the model show that the temperature of the part near the ear that directly touches the skin can be reduced by 51.4% by distributing heat sources into both sides, 11.1% by placing higher heat-generating components farther from the ear, and 65.3% in comparison with all high conductivity materials by using a combination of low thermal conductivity materials for temples and temple tips and high conductivity materials for rims.
Highlights
Wearable devices have become popular as state-of-the-art electronic devices, such as smart watches, smart glasses, smart clothing, and fitness trackers, have been made commercially available for consumer and industrial uses
Smart glasses have advantages that users can look at various things such as maps and movies with augmented reality (AR) through a display, and their eye and facial movements can be recognized for medical care, health monitoring, and dozing prevention
Heat issues will become more serious because smart glasses will require faster central processing unit (CPU) and larger memory to deal with enormous amounts of data
Summary
Wearable devices have become popular as state-of-the-art electronic devices, such as smart watches, smart glasses, smart clothing, and fitness trackers, have been made commercially available for consumer and industrial uses. The device body consists of many heat generating electronic components, including processors, memory, wireless modules, and power management integrated circuits (ICs). Upcoming advanced features including 4K/8K resolution processing are expected to need additional power to render the images [40,41,42,43,44,45] This will require more organized thermal management with overviewing packages, boards, and systems as well as heating processor chips [46]. Motion detection is another power consuming factor. The main sources of heat generation of smart glasses come from power consumptions of ICs. Thermal countermeasures within IC chips must be mainly low power designs and have a limit.
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