3D thermoreflectance (TR) imaging utilizing light field camera is proposed and developed in this study. With the capability of resolving light direction and intensity simultaneously, we are able to measure directional TR signal from tilted or curved surfaces through the light field camera. Once the directional TR coefficients of the target surface is collected, we can then estimate the temperature distributions of tilted or curved surfaces based on the measured directional TR signal. This new 3D TR imaging approach has the potential to measure temperature of surfaces with different configurations as long as the TR signal is strong enough. In this technical paper, we first present basic principles of 3D TR imaging techniques based on light field theory. The construction and calibration procedures of the resulting 3D TR imaging system are then presented. At the end of the technical paper we present steady-state surface temperature measurements of microscale electronic devices including an infrared laser diode and a gold wire with the current 3D TR imaging system. The obtained temperature distributions of the microscale samples showing high temperature and spatial resolutions in real-time temperature measurement on the 3D surfaces that cannot be achieved with traditional 2D TR imaging techniques.

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