In one aspect, an apparatus for determining a property of a fluid is disclosed that in one embodiment may include a transparent member having an axis and a first end substantially perpendicular to the axis and a second end having an outer surface at a first angle to the axis, a light source directing light at the first end, a detector placed spaced from the second end, the space between the second end and the detector containing a fluid, wherein the detector detects light exiting from the outer surface at a second angle to the axis and passing through the fluid, and a controller for determining the second angle from the light detected by the detector. A processor determines the bulk fluid refractive index from the light detected by the detector and a property of the fluid therefrom.

The present disclosure embodies a refractometer that includes an embodied fitting to the standardized probe with the optical structure to facilitate refractometer optics to the probe tip.

An electricity measuring type surface plasmon resonance sensor includes: a plasmon resonance intensifying sensor chip in which a prism and a sensor chip including an electrode, a silicon semiconductor film, and a plasmon resonance film electrode arranged in this order are arranged in an order of the prism, the electrode, the silicon semiconductor film, and the plasmon resonance film electrode; and an electric measuring apparatus which directly measures a current or voltage from the electrode and the plasmon resonance film electrode.

An electrical discharge machine includes a critical angle detection device that detects a critical angle of a machining fluid in which a corrosion inhibitor is added. The critical angle detection device includes a prism, a light source, an image sensor, an electrical circuit, and a slit. The prism has an incident surface, a boundary surface, a reflection surface, and an emission surface. The light source irradiates an incident light from the incident surface to the boundary surface. The image sensor includes a plurality of photodetectors that detect a reflection light. The electrical circuit calculates the critical angle by arithmetically processing output signals output from the plurality of photodetectors. The slit is arranged on an optical axis of the reflection light between the prism and the image sensor to block a scattered light.

The present disclosure embodies an improved optical instrument that includes an embodied fitting to the standardized probe with the optical structure to facilitate refractometer optics to the probe tip with a turbidity and/or color meter to form an embodied optical multimeter.

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.

An optical sensor has a body including a transparent interface wall having an outer surface in contact with a liquid, to define therewith a reflection interface. An optical module is coupled at an inner surface of the interface wall, to detect a characteristic of the liquid substance via light reflection. The optical module includes a light emitter and a light receiver facing respective inclined surfaces of the interface wall. The optical module also includes a supporting structure which is elastically flexible, to enable the light emitter and the light receiver of the optical module to vary a relative position thereof and with respect to the inclined surfaces of the interface wall, when the supporting structure is secured to the inner surface of the interface wall.

The disclosed subject matter relates to a measuring device for measuring the flow velocity of a flowing fluid, comprising a first measuring element, which is configured to measure the flow velocity of the fluid and includes an interface that can be exposed to the flowing fluid, a second measuring element, which is configured to measure a characteristic property of the fluid and includes an interface that can be exposed to the flowing fluid, and an evaluation unit, which is connected to the first and second measuring elements and configured to correct the flow velocity, measured by the first measuring element, by the influence of the property of the fluid, measured by the second measuring element, on the measurement of the flow velocity. The disclosed subject matter furthermore relates to a measuring probe for such a measuring device.

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.

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.