The invention relates to a method for detecting a local change in refractive index of a dielectric medium located on the surface of an optical sensor, said optical sensor comprising for this purpose a waveguide comprising a region, called the active region, covered with at least one metallic layer in contact with the dielectric medium, said method comprising the following steps: a) emitting a light beam at the input of the waveguide so that this light beam can be propagated, within the waveguide, according to at least N propagation modes, where N is a natural integer such that N≥2; b) measuring the intensity of at least one zone of the spatial distribution of the intensity of the light beam reflected by said active region of the optical sensor; and c) detecting the local change in the refractive index of the dielectric medium by means of a database supplying the link between the intensity of said at least one zone of the spatial distribution of the intensity of the light beam reflected by the active region of the optical sensor and a change in refractive index of a reference medium.

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.

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.

A droplet sensor has an optical cover with a curved surface that forms a part of a spheroid, a light source positioned at a first focal point of an ellipse, the first focal point facing the curved surface, and a photodetector positioned at a second focal point of the ellipse. The ellipse has an eccentricity determined such that the curved surface has an effective detection area that satisfies conditions for total internal reflection at an interface with a gas and that does not satisfy the conditions for total internal reflection at an interface with a liquid.

A droplet sensor has an optical cover with a curved surface that forms a part of a spheroid, a light source positioned at a first focal point of an ellipse, the first focal point facing the curved surface, and a photodetector positioned at a second focal point of the ellipse. The ellipse has an eccentricity determined such that the curved surface has an effective detection area that satisfies conditions for total internal reflection at an interface with a gas and that does not satisfy the conditions for total internal reflection at an interface with a liquid.

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.

The prism-coupling systems and methods include using a prism-coupling system to collect a 2D digital mode spectrum of an IOX article. The mode line and critical angle positions and orientations are found by performing a weighted fit to mode line and critical angle images and are used to define a compensated mode spectrum. If mode line tilt is found, it is removed from the 2D digital mode spectrum to define the compensated mode spectrum. The compensated mode spectrum is then processed using techniques known in the art to provide a more accurate estimate of stress-related characteristics of the IOX sample versus using the uncompensated mode spectrum. Derivative-based methods of accurately establishing positions of intensity transitions in a mode spectrum of an IOX sample using a derivative spectrum and curve fitting are also disclosed.

Disclosed herein, according to an aspect of some embodiments, is a dipping refractometer. The dipping refractometer includes a prism and a casing, housing a light source and a light sensor. The prism is mounted in/on the casing such as to allow dipping the prism in a fluid such that two surfaces of the prism and the fluid forming two respective direct prism-fluid interfaces. The prism, the light source, and the light sensor are configured such that for a continuous range of values of fluid refractive indices, most of the light incident on the light sensor, originating from the light source, undergoes total internal reflection off of each of the two direct prism-fluid interfaces.

A pre-aligner for pre-aligning a wafer having a notch. The pre-aligner includes a wafer platform having a wafer receiving surface, and a drive device. A detector is provided to detect the notch, and a memory is provided to store a notch window defining a range of angles in which the notch is predicted to be located in relation to a start position. A controller performs a pre-alignment operation where the wafer is rotated from the start position to an alignment location. The controller performs the operation such that the wafer is rotated at maximum acceleration/deceleration values from the start position to a notch location detected by the detector: where the operation is limited to a maximum velocity for rotation of the wafer from the start position to a notch window; and where the operation is limited to a scanning velocity within the notch window until the notch location is detected.