Abstract: The thickness of a tissue layer is calculated using optical measurements from a wearable physiological monitor. In general, a model—e.g., an analytical, empirical, or statistical model—can be created that interrelates distance from a light source (directed into the skin from the surface), light intensity, and tissue thickness. With this model, a suitable light source can be directed into skin, and measurements of light intensity at various distances along the surface of the skin from the light source can be used to calculate thickness of a tissue layer in a multi-layer structure such as the dermis over layers of fat, muscle, bone, and the like. Changes in dermal thickness can be tracked over time, and used to assess a user's health or fitness. The thickness can also support an evaluation of other characteristics such as dermis elasticity, e.g., tracking over time and correlating to health, hydration, and so forth.

Abstract: A physiological monitor uses a light source and a number of detectors to determine whether a physiological monitor is positioned for acquisition of physiological data. More specifically, an intensity of the light source, as measured at two photodetectors at different distances from the light source, can be used to accurately detect whether the monitor is properly positioned for use. The disclosed methods may advantageously leverage existing physiological monitoring hardware (such as light emitting diodes and photodetectors), and may improve on the accuracy of prior art techniques using, e.g., capacitive sensors and/or other hardware to detect proper device positioning.