Continuous wave time-of-flight (ToF) cameras have been rapidly gaining widespread adoption in many applications due to their cost effectiveness, simplicity, and compact size. However, the current generation of ToF cameras suffers from low spatial resolution due to physical fabrication limitations. In this paper, we propose an imaging architecture to achieve high spatial resolution ToF imaging using optical multiplexing and compressive sensing (CS). Our approach is based on the observation that, while depth is non-linearly related to ToF pixel measurements, a phasor representation of captured images results in a linear image formation model. We utilize this property to develop a CS-based technique that is used to recover high resolution 3D images. Based on the proposed architecture, we developed a prototype 1-megapixel compressive ToF camera that achieves as much as 4 x improvement in spatial resolution. We believe that our proposed architecture provides a simple and low-cost solution to improve the spatial resolution of ToF and related sensors.
A current focus of art conservation research seeks to accurately identify materials, such as oil paints or pigments, used in a work of art. Since many of these materials are fluorescent, measuring the fluorescence lifetime following an excitation pulse is a useful non-contact, quantitative method to identify pigments. In this project, we propose a simple method using a dynamic vision sensor to efficiently characterize the fluorescence lifetime of a common pigment named Egyptian Blue, which is consistent with x-ray techniques. We believe our fast, compact and cost-effective method for fluorescence lifetime analysis is useful in art conservation research and potentially a broader range of applications in chemistry and materials science.
Three-dimensional tissue cultures have been used as effective models for studying different diseases, including epilepsy. High-throughput, nondestructive techniques are essential for rapid assessment of disease-related processes, such as progressive cell death. An ultrahigh-resolution optical coherence microscopy (UHR-OCM) system with ∼1.5 μm axial resolution and ∼2.3 μm transverse resolution was developed to evaluate seizure-induced neuronal injury in organotypic rat hippocampal cultures. The capability of UHR-OCM to visualize cells in neural tissue was confirmed by comparison of UHR-OCM images with confocal immunostained images of the same cultures. In order to evaluate the progression of neuronal injury, UHR-OCM images were obtained from cultures on 7, 14, 21, and 28 days in vitro (DIVs). In comparison to DIV 7, statistically significant reductions in three-dimensional cell count and culture thickness from UHR-OCM images were observed on subsequent time points. In cultures treated with kynurenic acid, significantly less reduction in cell count and culture thickness was observed compared to the control specimens. These results demonstrate the capability of UHR-OCM to perform rapid, label-free, and nondestructive evaluation of neuronal death in organotypic hippocampal cultures. UHR-OCM, in combination with three-dimensional tissue cultures, can potentially prove to be a promising tool for high-throughput screening of drugs targeting various disorders.
Understanding the mechanism of angiogenesis could help to decipher wound healing and embryonic development and to develop better treatment for diseases such as cancer. Microengineered devices were developed to reveal the mechanisms of angiogenesis, but monitoring the angiogenic process nondestructively in these devices is a challenge. In this study, we utilized a label-free imaging technique, ultrahigh-resolution optical coherence microscopy (OCM), to evaluate angiogenic sprouting in a microengineered device. The OCM system was capable of providing ∼1.5-μm axial resolution and ∼2.3-μm transverse resolution. Three-dimensional (3-D) distribution of the sprouting vessels in the microengineered device was imaged over 0.6×0.6×0.5 mm 3 , and details such as vessel lumens and branching points were clearly visualized. An algorithm based on stretching open active contours was developed for tracking and segmenting the sprouting vessels in 3-D-OCM images. The lengths for the first-, second-, and third-order vessels were measured as 127.8±48.8 μm (n=8 ), 67.3±25.9 μm (n=9 ), and 62.5±34.7 μm (n=10 ), respectively. The outer diameters for the first-, second-, and third-order vessels were 13.2±1.0 , 8.0±2.1 , and 4.4±0.8 μm , respectively. These results demonstrate OCM as a promising tool for nondestructive and label-free evaluation of angiogenic sprouting in microengineered devices.
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