Design and Applications of Super-Continuum Lasers and Time-of-Flight Camera in Spectroscopy and Healthcare

The work in this dissertation focuses on expanding the capabilities of various technologies that enable optical contactless detection in various fields of applications. Specifically, we first discuss the design and implementation of supercontinuum (SC) lasers with ultra-broadband spectrum coverage into Long-Wave Infrared (LWIR). We then demonstrate a versatile Contactless Vital Sign Monitoring (CVSM) by leveraging the additional depth information from a ToF camera. Finally, we show that the CVSM system we demonstrate could be a key enabler for unobtrusive driver/passenger monitoring in a driving vehicle. We solve the conundrum of generating ultra-broadband infrared spectrum and high output power at the same time in Chapter 2. We generate a 417mW supercontinuum spectrum from 1.57 to 12μm with a soft glass fiber cascade consisting of ZBLAN fiber, As2S3 fiber and As2Se3 fiber pumped by a nanosecond thulium MOPA system. By separating LWIR SC generation processes into a cascade of SC fibers with optimized coupling between each SC fiber, we circumvent the need of complex optical parametrical amplifiers and improved the reliability of the SC source. Our study also suggests that to efficiently generate SC into LWIR, fiber parameters, such as numerical aperture, core size, and core/cladding composition, need to be optimized. Our SC generation methodology allows us to build monolithic all-fiber supercontinuum sources, which we then use to explore the benefits of SC-based stand-off spectroscopy systems for non-destructive quality inspections. Specifically, we demonstrate infrared spectroscopy systems that can predict concentrations of key chemical components of food samples in both the short-wave and mid-wave infrared spectral range. We measure 32 French fry and wheat flour samples with different acrylamide/wheat protein concentrations. Our predicted concentrations show a good linear correlation to the reference concentration obtained through gold-standard methods. Our results indicate that the SC-based system could provide an alternative, non-destructive method to determine the concentration of key chemical components in processed food samples at a stand-off distance. The latter half of this dissertation considers contactless technology for physiological parameter monitoring. In response to the COVID-19 pandemic, we develop a Contactless Vital Sign Measurement (CVSM) system that measures the heart rate (HR) and respiratory rate (RR) of an individual with an indirect ToF camera. Compared with conventional cameras, the additional depth information from the ToF camera allows us to compensate for motion artifacts during the HR measurement and directly derive the RR through the detection of chest wall movement during breathing. We conduct a pilot human study with 29 participants to show the system performs reliably across users of different skin color, age, and gender. We also show that our depth-based motion compensation greatly increases the reliability as well as the success rate (results within 10% of reference measurements) of the HR measurements. We then further develop the CVSM system and use the system to measure HR and RR in a driving vehicle. The indirect ToF used in the study is inherently robust against the illumination changes in the vehicle, while the depth information is used to compensate for motion induced intensity artifacts encountered during driving. We investigate the system’s performance in various scenarios including monitoring drivers while driving on both highway and local roads. Our results show that our CVSM system is ambient light agnostic and the success rates of HR measurements on highway are 82% and 71.9% for passenger and driver respectively.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/172743/1/kaiwguo_1.pd