A device for detecting rain includes a camera and a lighting source for emitting visible light onto a window. The camera and the lighting source are configured and arranged in such a way that the camera can detect a signal of the visible light which the lighting source emits onto the window. The signal which is detected by the camera correlates with visible light of the lighting source, which visible light is reflected or scattered at the inner face of the window or outer face of the window and/or at the raindrop. The visible light passes through a shutter device which causes the light to be blocked or highly attenuated in a predefined direction perpendicular to the illumination direction of structures of the shutter device. In contrast, the light in the direction perpendicular to the predefined direction and to the illumination direction can propagate virtually unimpeded through the shutter device.

A device for detecting rain includes a camera and a lighting source for emitting visible light onto a window. The camera and the lighting source are configured and arranged in such a way that the camera can detect a signal of the visible light which the lighting source emits onto the window. The signal which is detected by the camera correlates with visible light of the lighting source, which visible light is reflected or scattered at the inner face of the window or outer face of the window and/or at the raindrop. The visible light passes through a shutter device which causes the light to be blocked or highly attenuated in a predefined direction perpendicular to the illumination direction of structures of the shutter device. In contrast, the light in the direction perpendicular to the predefined direction and to the illumination direction can propagate virtually unimpeded through the shutter device.

An exemplary method for measuring a refractive index of a substance being measured through an optical window, includes arranging the optical window in contact with the substance being measured, directing light to the interface of the optical window and substance being measured, where part of the light is absorbed by the substance being measured and part of it is reflected from the substance being measured to form an image, in which the location of the boundary of light and dark areas expresses a critical angle of the total reflection dependent on the refractive index of the substance being measured, and examining the formed image. Light is directed on a first structure and to desired angles on an interface between the optical window and substance being measured. Light reflected from the interface of the optical window and substance being measured is directed on a second structure.

An exemplary method for measuring a refractive index of a substance being measured through an optical window, includes arranging the optical window in contact with the substance being measured, directing light to the interface of the optical window and substance being measured, where part of the light is absorbed by the substance being measured and part of it is reflected from the substance being measured to form an image, in which the location of the boundary of light and dark areas expresses a critical angle of the total reflection dependent on the refractive index of the substance being measured, and examining the formed image. Light is directed on a first structure and to desired angles on an interface between the optical window and substance being measured. Light reflected from the interface of the optical window and substance being measured is directed on a second structure.

Provided is an optical device including a dielectric transparent substrate and a metallic layer having a thickness between about 20 nm and about 1000 nm disposed on the transparent substrate. The metallic layer comprises at least one localized group of cavities, each localized group being confined within a diameter smaller than about 5 um, and each localized group comprising at least two cavities, with a distance between two adjacent cavities in the localized group being between about 100 nm and about 2000 nm. Each cavity in the localized group is shaped as a through-hole in the metallic layer, the through hole having a polygonal cross-section having a polygon side length between 50 nm and 2000 nm.

Apparatus and methods for performing optical analyses in a harsh environment are disclosed. Some of the systems and methods of the present disclosure include fluorescence, absorption, and reflectance detection using a drum spectrometer. Other systems and methods of the present disclosure include a measurement channel and a parallel reference channel concurrently filtering optical signals.

A method of determining a refractive index of a material sample comprises removably mounting the material sample into a sample holder having a thermal control mechanism, a thermal expansion compensation mechanism, and a rotation mechanism; projecting a laser beam into the material sample, wherein the material sample has a predetermined orientation and temperature, wherein the material sample has parallel sides defining parallel planes for entry and exit of the laser beam into and out of the material sample; collecting a refracted laser beam from the material sample, and determining the refractive index for the material sample at the predetermined temperature. The laser beam may be a visible laser and/or an infrared laser. The thermal control mechanism comprises a thermal controller coupled to an induction coil apparatus and a temperature sensor. The sample holder comprises a refractory metal consisting of one or more of a niobium/molybdenum alloy and a tantalum/tungsten alloy.

A method of determining a refractive index of a material sample comprises removably mounting the material sample into a sample holder having a thermal control mechanism, a thermal expansion compensation mechanism, and a rotation mechanism; projecting a laser beam into the material sample, wherein the material sample has a predetermined orientation and temperature, wherein the material sample has parallel sides defining parallel planes for entry and exit of the laser beam into and out of the material sample; collecting a refracted laser beam from the material sample, and determining the refractive index for the material sample at the predetermined temperature. The laser beam may be a visible laser and/or an infrared laser. The thermal control mechanism comprises a thermal controller coupled to an induction coil apparatus and a temperature sensor. The sample holder comprises a refractory metal consisting of one or more of a niobium/molybdenum alloy and a tantalum/tungsten alloy.

A method for determining a residual retardance of an LCOS (Liquid Crystal on Silicon) panel includes transmitting a light beam to the LCOS panel at an angle of incidence and measuring an intensity of a reflected light beam. The method includes biasing the LCOS panel in a dark state and measuring a dark state intensity of the reflected light beam. The method also includes biasing the LCOS panel in a bright state, and measuring a bright state intensity of the reflected light beam. A residual retardance of the LCOS panel is determined based on a contrast ratio of the bright state intensity and the dark state intensity. The method can also include selecting a compensator for the LCOS panel based on the residual retardance.

A method for determining a residual retardance of an LCOS (Liquid Crystal on Silicon) panel includes transmitting a light beam to the LCOS panel at an angle of incidence and measuring an intensity of a reflected light beam. The method includes biasing the LCOS panel in a dark state and measuring a dark state intensity of the reflected light beam. The method also includes biasing the LCOS panel in a bright state, and measuring a bright state intensity of the reflected light beam. A residual retardance of the LCOS panel is determined based on a contrast ratio of the bright state intensity and the dark state intensity. The method can also include selecting a compensator for the LCOS panel based on the residual retardance.