EAGER: Laser 4D light field thermoreflectance (TR) imaging for non-intrusive high accuracy temperature measurement of 3D targets with high spatial and high temporal resolutions

Texas A&M Engineering Experiment Station, College Station TX

Investigators

Abstract

The principal investigator will develop a technique to determine the temperature distribution on a three-dimensional (3D) surface or object. The technique is similar to 3D photography, with the added and much more complicated challenge in mapping out the temperature. A camera with an array of micro-sized lenses will be aimed at the object. Because at different angles these lenses project the images, the effect of three dimensions is achieved. At the same time the intensities of the light reflected from various points of the surface is related to temperatures, the temperature on the 3D surface can be determined. The PI will also involve high school teachers, especially those from schools with high minority population, in addition to supervising graduate and undergraduate students. The proposed study will create a microlens array (MLA) for thermal imaging, numerical algorithms to extract thermal information, and determination of transient 3D temperature profiles of LED packages during operating conditions and in transient state. The author will apply an approach known as 4D light field imaging, which enables imaging of 3D surfaces by the array of lenses, each having a different perspective on the object, to project images of the target (i.e., plenoptic images) onto a CCD sensor. The 3D image of the surfaces can then be reconstructed from the multiple perspectives, using an algorithm previously developed by the PI. Based on the temperature-dependent reflectivity and the reflected light intensity of the surfaces (i.e., their thermoreflectance), temperature changes can be identified. The proposed technique can achieve high accuracy (~ 10 mK), high spatial resolutions (~ half of light wavelength; i.e. diffraction-limited), and nano-second temporal resolutions. The technique can therefore be used for steady, quasi-steady, and transient state thermal imaging, enabling a wide range of applications including extreme conditions, light emitting diodes (LEDs) and laser diodes (LDs).