Optical sensors, systems and methods of use thereof are provided. Aspects of the subject systems include a sensor having a sensing surface and a configuration that directs a first optical signal to interact with the sensing surface at a first incident angle, and directs a second optical signal to interact with the sensing surface at a second incident angle. The subject sensors, systems and methods find use, e.g., in the diagnosis of dry eye disease.

Optical sensors, systems and methods of use thereof are provided. Aspects of the subject systems include a sensor having a sensing surface and a configuration that directs a first optical signal to interact with the sensing surface at a first incident angle, and directs a second optical signal to interact with the sensing surface at a second incident angle. The subject sensors, systems and methods find use, e.g., in the diagnosis of dry eye disease.

An apparatus for detecting one or more properties of a downhole fluid includes a housing. The apparatus also includes a location-sensitive optical detector, arranged within a chamber formed by the housing. The apparatus further includes a light source, arranged within the chamber. The apparatus also includes a lens, positioned at an end of the housing, the lens preferably having a flat side and a curved side, the flat side positioned proximate the chamber to position the flat side closer to the light source than the curved side. The apparatus further includes a mirror, arranged outside the housing.

Methods of improving the measurement of knee stress in an ion-exchanged chemically strengthened Li-containing glass sample that includes a knee are disclosed. One of the methods includes compensating for a shift in the location of the TIR-PR transition location associated with the critical angle location, wherein the shift is due to the presence of a leaky mode. Another method includes applying select criteria to the captured mode spectra image to ensure a high-quality image is used for the knee stress calculation. Another method combines direct and indirect measurements of the knee stress using the mode spectra from multiple samples to obtain greater accuracy and precision as compared to using either the direct measurement method or the indirect measurement method alone. Quality control methods of forming the glass samples using measured mode spectra and related techniques for ensuring an accurate measurement of the knee stress are also disclosed.

Methods of improving the measurement of knee stress in an ion-exchanged chemically strengthened Li-containing glass sample that includes a knee are disclosed. One of the methods includes compensating for a shift in the location of the TIR-PR transition location associated with the critical angle location, wherein the shift is due to the presence of a leaky mode. Another method includes applying select criteria to the captured mode spectra image to ensure a high-quality image is used for the knee stress calculation. Another method combines direct and indirect measurements of the knee stress using the mode spectra from multiple samples to obtain greater accuracy and precision as compared to using either the direct measurement method or the indirect measurement method alone. Quality control methods of forming the glass samples using measured mode spectra and related techniques for ensuring an accurate measurement of the knee stress are also disclosed.

Disclosed are systems and methods of label-free detecting cellular physiological activities involving monitoring local refractive index changes associated with cellular physiological activities using a single ultracompact light emitting diode (LED) chip serving as a refractometer.

Disclosed are systems and methods of label-free detecting cellular physiological activities involving monitoring local refractive index changes associated with cellular physiological activities using a single ultracompact light emitting diode (LED) chip serving as a refractometer.

A droplet sensor includes an optical cover that forms part of a spheroid, a major axis of the spheroid being a vertical axis, a light emitting/receiving device disposed at a position offset from a first focal point of the spheroid along the major axis, and a reflector disposed in vicinity of a second focal point of the spheroid. The optical cover has an effective detection area between the light emitting/receiving device and the reflector. The effective detection area satisfies a total internal reflection condition at an interface with a gas, and does not satisfy the total internal reflection condition at an interface with a liquid. The reflector reflects, towards a light receiving surface of the light emitting/receiving device, light totally reflected by the effective detection area, or reflects, towards the effective detection area, light directly incident on the reflector from the light emitting/receiving device.

A droplet sensor includes an optical cover that forms part of a spheroid, a major axis of the spheroid being a vertical axis, a light emitting/receiving device disposed at a position offset from a first focal point of the spheroid along the major axis, and a reflector disposed in vicinity of a second focal point of the spheroid. The optical cover has an effective detection area between the light emitting/receiving device and the reflector. The effective detection area satisfies a total internal reflection condition at an interface with a gas, and does not satisfy the total internal reflection condition at an interface with a liquid. The reflector reflects, towards a light receiving surface of the light emitting/receiving device, light totally reflected by the effective detection area, or reflects, towards the effective detection area, light directly incident on the reflector from the light emitting/receiving device.

A droplet sensor includes an optical cover having a curved surface that forms a part of a spheroid, a protective film that covers the curved surface of the optical cover, a light source provided at a first focal point of an ellipse facing the curved surface, and a photodetector provided at a second focal point of the ellipse. The refractive index of the protective film is greater than the refractive index of a liquid to be detected. A sensing region is determined by a range of an incident angle at which a light beam emitted from the light source and incident onto the curved surface is totally reflected at the interface between the protective film and a gas, and is not totally reflected at the interface between the protective film and the liquid to be detected.