Knowing the amounts of energy and nutrients in an individual’s diet is important for maintaining health and preventing chronic diseases. As electronic and AI technologies advance rapidly, dietary assessment can now be performed using food images obtained from a smartphone or a wearable device. One of the challenges in this approach is to computationally measure the volume of food in a bowl from an image. This problem has not been studied systematically despite the bowl being the most utilized food container in many parts of the world, especially in Asia and Africa. In this paper, we present a new method to measure the size and shape of a bowl by adhering a paper ruler centrally across the bottom and sides of the bowl and then taking an image. When observed from the image, the distortions in the width of the paper ruler and the spacings between ruler markers completely encode the size and shape of the bowl. A computational algorithm is developed to reconstruct the three-dimensional bowl interior using the observed distortions. Our experiments using nine bowls, colored liquids, and amorphous foods demonstrate high accuracy of our method for food volume estimation involving round bowls as containers. A total of 228 images of amorphous foods were also used in a comparative experiment between our algorithm and an independent human estimator. The results showed that our algorithm overperformed the human estimator who utilized different types of reference information and two estimation methods, including direct volume estimation and indirect estimation through the fullness of the bowl.

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We present a highly reproducible method of fabricating a tapered intrinsic Fabry-Perot interferometer (IFPI) device with 5~6-m diameter at the taper waist. A femtosecond laser was applied to inscribe an IFPI with 3-cm cavity length in a single-mode fiber. A CO2 laser heated tapering process enabled by digitally controlled mirrors and a precision motorized fiber feed system was used to create a stable heating zone with the desired temperature profile for tapering the fiber IFPI cavity. The well-engineered tapering process produced tapered IFPI devices with insertion loss less than 0.3-dB at 1550-nm. A strong evanescent field exposed by the taper section was explored for refractive index sensing. Using swept optical frequency domination reflectometry, the tapered IFPI fiber sensor achieved a minimal refractive index sensing resolution 210 -5 . This paper demonstrates an integrated laser fabrication technique to produce tapered fiber optic devices for sensing applications.

We report a CO2 laser fabrication method to produce a tapered intrinsic Fabry-Perot interferometer (IFPI) device with 5~6-um diameter of the taper waist with transmission losses of <0.3dB at 1550nm for sensing application.