In this study, a portable and large-area blackbody system was developed following a series of processes including design, computational analysis, fabrication, and experimental analysis and evaluation. The blackbody system was designed to be lightweight (5 kg), and its temperature could exceed the ambient temperature by up to 15 °C under operation. A carbon-fiber-based heat source was used to achieve a uniform temperature distribution. A heat shield fabricated from an insulation material was embedded at the opposite side of the heating element to minimize heat loss. A prototype of the blackbody system was fabricated based on the design and transient coupled electro-thermal simulation results. The operation performance of this system, such as the thermal response, signal transfer function, and noise equivalent temperature difference, was evaluated by employing an infrared imaging system. In addition, emissivity was measured during operation. The results of this study show that the developed portable and large-area blackbody system can be expected to serve as a reliable reference source for the calibration of aerial infrared images for the application of aerial infrared techniques to remote sensing.

In this paper, we report on a confocal thermoreflectance imaging system that can examine the thermal characteristics of microelectronic devices by penetrating the backside of a device through the substrate. In this system, the local reflectivity variations due to heat generation in the device are measured point by point by a laser scanning confocal microscope capable of eliminating out-of-focus reflections and the thermoreflectance is extracted via Fourier-domain signal processing. In comparison to the conventional widefield thermoreflectance microscope, the proposed laser scanning confocal thermoreflectance microscope improves the thermoreflectance sensitivity by ~23 times and the spatial resolution by ~25% in backside thermoreflectance measurements.

Micro-electronic devices are increasingly incorporating miniature multi-layered integrated architectures. However, the localization of faults in three-dimensional structure remains challenging. This study involved the experimental and numerical estimation of the depth of a thermally active heating source buried in multi-layered silicon wafer architecture by using both phase information from an infrared microscopy and finite element simulation. Infrared images were acquired and real-time processed by a lock-in method. It is well known that the lock-in method can increasingly improve detection performance by enhancing the spatial and thermal resolution of measurements. Operational principle of the lock-in method is discussed, and it is represented that phase shift of the thermal emission from a silicon wafer stacked heat source chip (SSHSC) specimen can provide good metrics for the depth of the heat source buried in SSHSCs. Depth was also estimated by analyzing the transient thermal responses using the coupled electro-thermal simulations. Furthermore, the effects of the volumetric heat source configuration mimicking the 3D through silicon via integration package were investigated. Both the infrared microscopic imaging with the lock-in method and FE simulation were potentially useful for 3D isolation of exothermic faults and their depth estimation for multi-layered structures, especially in packaged semiconductors.

This study presents a straightforward, efficient dual-mode thermoreflectance microscopy (TRM) system for analyzing the stationary and dynamic thermal properties of microelectronic devices. The proposed TRM system employs a standard visible microscope and implements two distinct imaging process schemes to obtain thermal images at different time scales. For TRM imaging of an ohmic microdevice, the optimal probing wavelength is predetermined from the thermoreflectance spectrum, acquired using a white light-emitting diode source and tunable bandpass filters to enhance thermal sensitivity. Thermoreflectance images are obtained in both stationary and transient modes using a four-bucket method and a pulsed boxcar averaging method, respectively. This thermography approach demonstrates highly sensitive, time-integrated stationary thermal imaging and time-gated transient thermal imaging with a temporal resolution of 200 ns. The system shows significant potential as an analytical tool with a sub-micron spatiotemporal resolution for evaluating heat generation and self-heating behavior in microelectronic devices.

We propose a model predictive control (MPC) method to compensate for the time-varying phase aberrations in a sensorless adaptive optics (AO) system. The approximate model for the point spread function (PSF) of the imaging system with phase diversity is mathematically derived, and its validity is verified. The proposed MPC, which considers the operating limits of the deformable mirror (DM), computes the optimal applied voltage of each actuator over a prediction horizon, and the receding horizon scheme is applied as feedback control. Numerical case studies with the time-varying phase aberrations generated by an atmospheric turbulence simulator are presented to demonstrate the correction performance of the MPC strategy. The proposed method caused a 50% improvement in the reduction in residual aberration, making it competitive with a saturation linear quadratic regulator (LQR). The computational feasibility of the proposed method is validated using fast MPC, which approximates the primal barrier method.

NDE of Low-Velocity Impact Damage in GFRP Using Infrared Thermography Techniques Low-Velocity Impact Damage;Glass Fiber Reinforced Plastic;Pulse Thermography;Lock-in Thermography; In this study, low-velocity impact damage (LVID) in glass fiber reinforced plastic (GFRP) was investigated using pulse thermography (PT) and lock-in thermography (LIT) techniques. The main objective of this study was to evaluate the detection performance of each technique for LVID in GFRP. Unidirectional and cross-ply GFRPs were prepared with four energy levels using a drop weight impact machine and they were inspected from the impact side, which may be common in actual service conditions. When the impacted side was used for both inspection and thermal loading, results showed that the suggested techniques were able to identify the LVID which is barely visible to the naked eye. However, they also include limitations that depend on the GFRP thickness at the location of the delamination produced by the lowest impact energy of five joule.