Thermal Model and Countermeasures for Future Smart Glasses

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.

Emerging Sensing Technologies in Consumer Electronics

“…Smart glasses are attracting particular attention because they offer convenient features such as hands-free augmented reality (AR) [14]. Since smart glasses directly touch the face and head, the device with high temperature has a detrimental effect on human physical health [14].…”

“…Smart glasses are attracting particular attention because they offer convenient features such as hands-free augmented reality (AR) [14]. Since smart glasses directly touch the face and head, the device with high temperature has a detrimental effect on human physical health [14]. K. Matsuhashi considered a thermal network model in a steady state condition and thermal countermeasure methods for thermal management of future smart glasses [14].…”

“…Since smart glasses directly touch the face and head, the device with high temperature has a detrimental effect on human physical health [14]. K. Matsuhashi considered a thermal network model in a steady state condition and thermal countermeasure methods for thermal management of future smart glasses [14]. 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 [14].…”

“…K. Matsuhashi considered a thermal network model in a steady state condition and thermal countermeasure methods for thermal management of future smart glasses [14]. 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 [14]. 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 [14].…”

Thermal management of wearable and implantable electronic healthcare devices: Perspective and measurement approach

“…48,84,85 This design involves direct contact with the skin at the face and head, which can have detrimental effects at a high temperature. Matsuhashi et al 86 presented a thermal network in a steady-state condition and a thermal countermeasure for smart glasses, as illustrated in Figure 4A. When the heat-generating components are farther from the ear, temperature increase can be reduced by 11.1% ( Figure 4B).…”