An exemplary arrangement includes a prism-shaped measuring window, which has a measuring surface adapted to contact a substance being measured. A first surface is adapted to direct light originating from a light source to the measuring surface through the measuring window. A second surface is adapted to direct totally reflected light from an interface between the measuring surface in contact with the substance being measured and a substance being measured outside of the measuring window. A first lens arrangement is adapted to focus the light from the light source on the first surface. A second lens arrangement is adapted to focus the totally reflected light passing through the second surface to a device used for analysis. A lens in each of the first and second lens arrangements closest to the measuring window is integrated into the measuring window and establishes optical refractive power in the first and second surfaces.

Disclosed is a method of measuring a surface refractive index of a strengthened glass including causing light to enter a surface layer of the strengthened glass through a liquid provided with a refractive index equivalent to that of a surface of the surface layer; a process of causing the light to be emitted from the strengthened glass through the liquid; converting two types of light components into two types of emission line sequences; capturing an image of the two types of emission line sequences; measuring positions of respective emission lines of the two types of emission line sequences from the image; and calculating refractive indexes of a surface of the strengthened glass corresponding to the two types of light components, or refractive index distributions of the strengthened glass in a depth direction from the surface corresponding to the two types of light components.

Apparatus and methods for measuring mode spectra for ion-exchanged glass substrates having a steep index region are disclosed. An interfacing fluid is provided between the coupling prism and the glass substrate. The interfacing fluid thickness is selected so that the variation in modal birefringence with fluid thickness is reduced to an acceptable level. The coupling prism can include a prism coating on the coupling surface so that the substrate-prism interface includes the prism coating. The coupling prism can also include stand-off members that serve to define the thickness of the interfacing fluid.

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 N2; 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.

Apparatus and methods for measuring mode spectra for ion-exchanged glass substrates having a steep index region are disclosed. An interfacing fluid is provided between the coupling prism and the glass substrate. The interfacing fluid thickness is selected so that the variation in modal birefringence with fluid thickness is reduced to an acceptable level. The coupling prism can include a prism coating on the coupling surface so that the substrate-prism interface includes the prism coating. The coupling prism can also include stand-off members that serve to define the thickness of the interfacing fluid.

A plasmonic sensor includes at least a substrate and a thin film metallic glass formed on the substrate. The dielectric constant (.sub.r) of the thin film metallic glass is negative. Since the thin film metallic glass with negative .sub.r is used in the plasmonic sensor, the material cost can be significantly reduced, the mechanical property can be improved, and the optoelectronic property can be increased. Since the thin film metallic glass is a kind of supercooled alloy with amorphous structure, it can be applied for imprinting deformation and amorphous without grain boundary scattering.

A method for monitoring an oil level in a machine includes transmitting a light beam into an optical system to be reflected or refracted to a receiver to generate a reception signal. The light beam is emitted at a set transmission power, and an oil deficiency is recognized when the reception signal exceeds a predefined level value. The transmission power of the light beam is settable between a minimum and a maximum transmission power, and contamination of the optical system is analyzed by: (a) the transmitter transmits a first light beam at the maximum transmission power to generate a first reception signal, and (b) analyzing the difference between the first reception signal and a second reception signal generated by a light beam at less than the maximum transmission power, the magnitude of the difference representing a measure of the degree of contamination of the optical system.

A detection tube includes a main body and an optical structure. The main body includes a bottom wall and a side wall extending from a periphery of the bottom wall to a first direction, and the side wall and the bottom wall jointly form a detection groove. The optical structure is connected to the bottom wall, the optical structure includes an incident surface and an exit surface, the incident surface and the exit surface are extending from the periphery of the bottom wall to a second direction opposite to the first direction. A first distance between portions of the incident surface and the exit surface adjacent to the bottom wall is greater than a second distance between portions of the incident surface and the exit surface away from the bottom wall.

A deflecting prism for electromagnetic radiation, in particular for refractometer- and/or ATR-measurements, is part of a measuring configuration. The deflecting prism has a body produced in one piece from a mono-crystal. The body has at least two beam conductive surfaces on a side of the body opposite each other or circumferentially about the body and a measuring surface lying between the beam conductive surfaces or surrounded by the latter. The body further has at least one beam entry surface or a beam exit surface. Accordingly, the measuring surface lies on an elevation formed on the body, which crosses over via a ledge surrounding the elevation into the remaining part of the body. On the remaining part, the beam conductive surfaces and/or the beam entry surface or exit surface lie.

Method and device for measuring the Abbe number in a process liquid. Light generates successively at wavelengths of 486.1 nm, 589.3 nm and 656.3 nm and different light wavelengths are directed successively through a measuring window in the process liquid so total reflection occurs at each wavelength on the measuring window surface and process liquid. Partial light reflected at each wavelength is directed to a sensor, whereby an image forms on the sensor surface; between light and dark boundary region corresponding to each wavelength critical angle, in which total reflection occurs. At each wavelength between light and dark boundary region detection by image analysis. At each wavelength, dependency between light and dark boundary region and refractive-index of process liquid measurement is detected, the Abbe number by refractive-index values obtained from: $V_D=\frac{n_D-1}{n_F-n_C};$
n.sub.D=refractive-index of process liquid to measure at 589.3 nm; n.sub.F=refractive-index at 486.1 nm; and n.sub.C=refractive-index at 656.3 nm.