Abstract: A soil moisture sensor uses a non-collimated light source and a photosensor, respectively, mounted at the foci of a transparent ellipsoidal plastic body. The dimensions of the body are such that emitted light rays are internally reflected toward the photosensor at the surface of the ellipsoid if the surface is dry, but refracted outwardly of the body when the surface is wet. The amount of light reflected onto the photosensor is thus a measure of the amount of moisture at the surface of the sensor. Direct illumination of the photosensor by the light source is prevented either by interposing opaque electronic components between them on a circuit board, or by taking advantage of light source characteristics to minimize the amount of transmitted light. If a circuit board is used, it is completely encapsulated against moisture penetration by fixing it in a carrier and molding the body around and onto the carrier to form a monolithic unit with the carrier and circuit board.

Abstract: The invention is directed to a method for determining repairability of an original clear coat applied over a darkly pigmented substrate with a corresponding repair clear coat used in repairing damaged original vehicle coatings. The method non-destructively determines the refractive indices of the original clear coat and the corresponding repair clear coats by acquiring the reflection spectrum of these coats with a spectrophotometer with d/8° measurement geometry with and without the specular components followed by determining the refractive indices with the assistance of the differential spectrum between the reflection spectrums with and without the specular components, and then comparing the refractive indices to determine difference between these refractive indices, wherein when the difference between the refractive indices of the original arid repair clear coats is within an acceptable range, the repair clear coat is used for repairing the original clear coat.

Abstract: A method for evaluating the refractive index homogeneity of an optical member includes passing light through an optical member (1) used for photolithography. The side surface (1a) with respect to the optical axis (AX) of the optical member (1) is retained by elastic members (4) at a plurality of positions disposed at equal intervals to pass light through the optical member (1) and measure a wave front aberration. The optical member is rotated around the optical axis (AX) by the equal interval to measure a wave front aberration again and determine the difference from the initial measurement. The optical member (1) is moved in a direction perpendicular to the optical axis (AX) to measure a wave front aberration again and determined the difference from the initial measurement. The refractive index homogeneity of the optical member can be accurately evaluated from those differences by using fitting of the Zernike cylindrical function.

Abstract: Spectroscopic ellipsometer system(s) mediated methodology for quantifying layer defining parameters in mathematical models of samples which contain a plurality of layers of different materials, at least some of which are absorbing of electromagentic radiation, wherein an acquired data set is not sufficient to allow definite one for one parameter evaluation, and wherein a global fit procedure can be applied to obtain good parameter starting values for use in a parameter evaluating regression procedure.

Abstract: Methods and systems are disclosed that include an optical device for providing information about one or more samples. The system includes well(s) for holding the sample(s), and in one embodiment, the optical device(s) have non-parallel sidewalls optically contacting the well(s) for providing the information about the sample(s) in the well(s). In some embodiments the optical devices may be truncated prism(s). In some embodiments the optical devices are part of a unibody structure with the well(s).

Abstract: A method, a portable device and a measuring instrument for standardization of a satellite measuring instrument to a corresponding master measuring instrument are disclosed. The portable device includes a device for containing a reference material, and an information unit for storing information about the reference material and measurements of the reference material on the master measuring instrument. When placed in a satellite measuring instrument, information from the master instrument stored in the information unit of the portable device is transmitted automatically and wirelessly to the satellite instrument and, together with measurements by the satellite instrument of the reference masterial in the portable device, a standardization model for the satellite instrument and the sample type is obtained.

Abstract: The present invention relates to ink output in ink jet printing systems. A refractometer is used to control the concentration of inks used in continuous ink jet printers. A concentration detector measures the total amount of light reflected from a surface. Changes in the ink cause a definite change in sensor output. As the refractive index is changed, shifting the critical angle for internal reflection, more or less light is reflected to the sensor. The index of refraction can be determined from the sensor once corrections are made to account for temperature dependencies of the sensor and light source and baseline measurement of reflected light amplitude. These dependencies are carried out in the refractometer.

Abstract: A general, closed, anisotropic kinetic turbulence theory for gases and liquids is based on new solutions of the Maxwell moment equations of the Boltzmann equations. These solutions provide a closed initial equation set for the four time average fluid mechanic variables, the sixteen time average thermal motion correlation and the sixteen time average turbulent motion correlations listed in Table I.

Abstract: The invention relates to a refractometer and to a refractive index measuring method. The invention directs an incident light ray onto an interface of a medium of known refractive index and of the medium studied, then measuring the intensity of the reflected light ray. The ratio between the intensity of the incident ray and the intensity of the reflected ray allows the refractive index of the medium studied to be calculated by means of Fresnel's formulas.

Abstract: A soil moisture sensor has a cylindrical body of transparent cyclic olefin polymer (COC). A pair of axially spaced cavities tapered toward each other are formed in the body. A light source is placed in one of the cavities, and a light sensor is placed in the other. The walls of the cavities are so curved that divergent light rays from the light source are refracted at the cavity-body interface into parallelism, and that reflected parallel rays are refracted at the body-cavity interface so as to focus on the light sensor. The parallel rays coming from the light source are reflected or refracted at the outer surface of the body, depending upon whether the ambient environment of the sensor is dry or wet.

Abstract: A refractometer with blazed Bragg gratings. In order to measure the refractive index of a medium, for example a liquid or a gas, the refractometer includes a waveguide having a blazed Bragg grating, the spectral response of which depends on the refractive index of the medium and a light source in order to make this light interact with the grating. Further, spectral analysis of the light which has interacted with the grating is performed, the spectrum provided by the spectral analysis is recovered, and, from the recovered spectrum, the spectral response of the grating is correlated with one value of the refractive index of the medium.

Abstract: Methods and instruments are provided for measuring differences in fractional reflectivity changes between transverse electric (TE or s-polarized) and transverse magnetic (TM or p-polarized components of an obliquely incident light with high sensitivity and low noise. Also provided are high sensitivity, low noise methods and instruments for measuring differences in fractional reflectivity changes between R-polarized (right-circularly polarized) and L-polarized (left-circularly polarized) components of a near-normal incident light. The methods take advantage of a nulling step to minimize harmonics of the optical signal derived from a first sample. Determination of odd and even harmonics of the optical signal derived from a second sample allows determination of refractive index and optical absorption coefficient differences between two samples to be determined with high sensitivity and low noise.

Abstract: A metrology system includes a laser, a position sensitive detector array, a first collimator, a second collimator, and a mirror. The position sensitive detector array and the first collimator are positioned at a reference point. The second collimator and the mirror are positioned at a point target at a distance from the reference point. A laser beam is alternately provided to the first collimator and the second collimator by optical fiber. The position sensitive detector array measures position data from a first laser crosshair generated by the first collimator and from a second laser crosshair generated by the second collimator. By alternating the activation of the first collimator and the second collimator it is possible to measure 5 degrees-of-freedom for the point target. A metrology system processing unit provides analog data processing. The metrology system that is suitable for, but not limited to, facilitating active compensation of large spacecraft structures.

Abstract: Disclosed herein is an apparatus and method for detecting a selected material that change an effective dielectric constant of a circular resonator. An example of the apparatus includes an input waveguide, an output waveguide and a circular resonator. The input waveguide receives electromagnetic wave from an electromagnetic wave source. The circular resonator is located adjacent to the input and output waveguides, which enables the resonator to receive electromagnetic wave from the input waveguide. The circular resonator bonds to a selected material, e.g. chemical gas, chemical liquid, and bio-agent. The selected material can change the effective dielectric constant of the circular resonator, which in turn causes a change in the electromagnetic wave intensity of the circular resonator. The output waveguide receives the change in electromagnetic wave intensity from the circular resonator, which can be used to determine the selected material qualitatively and quantitatively.

Abstract: A method and system for measuring the temporal response of a micromirror array to a variety of driving signals. A micromirror array is illuminated with a coherent light source so that a diffraction pattern is reflected from the micromirror array. One or more photodetectors are aligned with spots of light in the diffraction pattern that correspond to orders of the diffraction pattern. Diffraction pattern theory predicts that the intensity of these spots of light will vary as the tilt angle of the micromirrors is changed. Thus, by measuring the relative intensity of the spots of light as the micromirror array is provided with a variety of driving signals, many performance characteristics of the micromirror array can be measured. Some of these characteristics include the impulse response, the forced resonant frequency (i.e. the natural frequency), the damped resonant frequency, the quality factor of the micromirror response, the damping factor of the micromirror response, and the frequency transfer function.

Abstract: A system, method and apparatus provide the ability to detect a chemical in an analyte. To detect the chemical, the invention utilizes a laser having an open cavity. A photonic crystal lattice structure having a defect defines a suitable geometry for such a cavity. The analyte is introduced directly into a high optical field of the cavity. Thereafter, the cavity is pumped and an emission from the laser is used to detect the presence of the chemical in the analyte.

Abstract: The focus detecting unit includes, a light source unit emanating a collimated light, an optical unit to be inspected, which is equipped with a container having translucency, a lens and liquid, a deflection unit which irradiates a light to the unit to be inspected by diffracting a light from the light source, a spot position detecting means 4 arranged near a backside focus plane of the optical unit to be inspected, and an operating means which calculates the composite focal length of a lens and liquid in the optical unit to be inspected by using the spot position detected by the spot position detecting means.

Abstract: The invention relates to a portable refractometer comprising a depression (7) for samples, located on an insertion tip (11) in such a way that once the insertion tip (11) has penetrated a liquid or a fruit, a sufficient quantity of the sample liquid remains in the depression (7) for samples, thus wetting a measuring surface (4) that is delimited in said depression by a transparent body. The refractive index of the wetting liquid can be determined by measuring the intensity of an optical beam that is reflected by the measuring surface (4).

Abstract: A high-pressure resistant compact precision measurement head for highly exact optical refractive index measurements in liquids and/or gases comprising a refractive index reference body, mounted on a high-pressure bulkhead fitting. The body is composed of a single, optically homogenous material produced by pre-calculation of its geometry economically, mechanically and automatically with extremely low tolerances. The measurement head can be formed in such a manner that it has on its front portion an especially small measurement volume to as little as less than 0.5 mm3, through which a very thin optical measurement ray passes. The latter is produced behind a high-pressure bulkhead fitting in a pressure-protected interior cavity of the instrument and also evaluated there as an incoming ray after passing through the measurement medium. The precision measurement head possesses thereby no assembly and adjustment elements of optical components in the high-pressure area of the measurement medium.

Abstract: An improved differential refractometer incorporating a photodetector array is disclosed. Using a multi-element photo array provides the basis for measurement of differential refractive index values with a heretofore unattainable combination of sensitivity of measurement and concurrent range of measurement. Within the large dynamic range attainable, the detector structure provides equal sensitivity irrespective of deflection within the range. The transmitted light beam is tailored to provide a spatial variation of the light intensity at the array improving thereby the precision of measurement of its displacement. This in turn results in improved precision in the reported differential refractive index and in the calculation of the differential refractive index increment dn/dc. Integrating the detector array into the flow cell structure of the parent case results in a detector of exceptional sensitivity and range for sample quantities far smaller than required by conventional differential refractometers.

Abstract: The invention relates to refractometry and attenuated reflectance spectrometry in a wellbore environment. Specifically, it pertains to a robust apparatus and method for measuring refractive index of fluids along a continuum (rather than in steps), and for measuring attenuated reflectance spectra, and for interpreting the measurements made with this apparatus to determine a variety of formation fluid parameters. The present invention provides a method and apparatus to distinguish between gas and liquid based on the much lower index of refraction of gas. It can also be used to monitor fluid sample clean up over time. The refractive index of a wellbore fluid is determined from the fraction, R, of light reflected off the interface between a transparent window that has a known refractive index and this fluid. Preferably, the refractive index is measured at some wavelength of light for which the fluid is not highly attenuating but is optimally attenuating.

Abstract: A method of monitoring an immersion lithography system in which a wafer can be immersed in a liquid immersion medium. The method detects an index of refraction of the immersion medium in a volume of the immersion medium through which an exposure pattern is configured to traverse and determines if the index of refraction is acceptable for exposing the wafer with the exposure pattern. Also disclosed is a monitoring and control system for an immersion lithography system.

Abstract: A method and apparatus detects dew precipitation and determines dew precipitation onset pressure in a sample of formation fluid located downhole in an oilfield reservoir. In a preferred embodiment, the method includes (a) isolating a sample of formation fluid downhole; (b) illuminating the sample downhole with fluorescence excitation light; (c) measuring at least one characteristic of fluorescence short from the sample; (d) reducing pressure on the sample; (e) repeating steps (b) to (d); (f) detecting dew precipitation when a change is detected in a parameter that is a function of the at least one characteristic of fluorescence emission; and (g) setting dew precipitation onset pressure equal to pressure on the sample when the change in the parameter is detected. The parameter preferably is a function of fluorescence intensity and fluorescence red shift, and the change is an increase in fluorescence intensity and detection of fluorescence red shift.

Abstract: An RF system (100) can include one or more RF circuits (108) coupled to a fluid dielectric (106). The RF circuit can be disposed on a portion of a dielectric substrate (102) which also contains the fluid dielectric. A light source 302 is provided for transmitting optical radiation through a portion of the fluid dielectric in a transmitted direction. A sensor (304) measures at least one parameter indicative of a change of direction of the optical radiation relative to the transmitted direction. According to one aspect, the light source and/or the sensor can be disposed within the dielectric substrate of the RF system. An output of the sensor can be coupled to a processor (322, 422) for determining a condition of the fluid dielectric based on the measured parameter.

Abstract: The invention relates to a refractometer and to a method of measuring the refractive index of a medium. An incident light ray is directed onto an interface consisting of a medium of known refractive index and of the medium being studied. Then the intensity of the reflected light ray is measured. The incident and reflected light rays are propagated in an optical fiber section. The ratio between the intensity of the incident ray and the intensity of the reflected ray allows the refractive index of the medium studied to be calculated by means of Fresnel's formulas.

Abstract: A sensitivity-enhanced flow cell to be used in the determination of the differential refractive index increment of a sample fluid relative to a reference fluid is disclosed. The invention permits the use of smaller sample amounts without sacrificing overall sensitivity. Equally important, said improved flow cell produces measurements of increased precision without requirement for increased sample amount. This is achieved by means of two chambers within said cell whose volumes are different. The sample fluid chamber is the smaller of the two with the reference fluid chamber constructed so that the incident illumination beam, upon passage through said sample chamber and displacement by the partition element located therebetween said sample and reference chambers, passes through said reference chamber without grazing any of the confining walls or striking corners of said sensitivity-enhanced flow cell.

Abstract: The matter for which the refractive index is to be determined, is made available in the form of a theoretically determinable scattering or diffraction pattern. Two or more orders of diffraction may then be defined to form at least one intensity ratio. At least one intensity distribution may be formed by irradiating the scattering pattern using one light beam of a defined shape. Subsequently thereto, the intensity ratio may be formed based on the orders of diffraction of the intensity distribution. In addition, at least one portion of a characteristic curve may be determined, which represents the dependency of the intensity ratio on the refractive index, and, with whose assistance, the corresponding refractive index can be assigned to the intensity ratio formed.

Abstract: A method of evaluating optical disturbances occurring in a flow field around a solid body. The method includes performing a computational fluid dynamics (CFD) calculation to obtain a three-dimensional index-of-refraction field outside the solid body, and performing one or more ray tracing calculation based on the sindex-of-refraction field to botain a numerical estimater of the optical disturbances.

Abstract: A refractive power measuring method is disclosed wherein a pattern plate 8 is disposed at a certain position in a measuring optical path in a measuring optical system 1, a measuring light emitted from a measuring light source 5 is received by a photosensor 9 through the pattern plate 8, a soft contact lens TL is disposed at a certain position in the measuring optical path, and a change of a pattern light received by the photosensor 9 is obtained to determine optical characteristic values of the soft contact lens.

Abstract: A method for calculating the refractive index and the extinction coefficient for materials relates the physical parameters being calculated to the scattering caused by interband states in the material using a model which includes a quantum mechanical transition equation for transitions between valence and/or conduction bands and interband states of the material. The method can be used for material engineering, process control for processes affecting the interband states in the material, and in estimation of the amount of interband states which have been introduced into a material as a result of such a process. Apparatus for implementing the method are also disclosed.

Abstract: Real time determination of the presence of emulsion in a formation fluid is accomplished using an optical probe, preferably an attenuated total reflectance probe. The determination can then be used to appropriately increase, decrease or leave unchanged the use of demulsification additives or other means to control emulsion formation. The method is particularly useful for free water knock-out separations, where a plurality of probes can be used to distinguish the location and/or volume of emulsion, or “rag”, layer and thereby to facilitate decantation of relatively pure oil and water fractions. It can also be effectively used in pipelines, and can optionally determine the degree of emulsification and trends toward emulsification or demulsification.

Abstract: A method of measuring a radial index distribution of a rod lens has the steps: (1) the rod lens is processed so that the length is approximately P/2 (where P is pitch length) or an integer multiple thereof and so end surfaces parallel, (2) a patterned surface is set as an object surface in the proximity of one end surface, and an image surface is formed in the proximity of the other end surface by irradiating the patterned surface with condensed monochromatic light, (3) the positions of paraxial focal points and the curves of curvature of field are obtained by observing the image surface, and (4) higher-order index distribution coefficients are calculated back by a fitting process on the basis of the positions of paraxial focal points and the curves of curvature of field.

Abstract: The invention relates to a method and system for measuring the internal refractive index of an optical fiber preform with high precision. The internal refractive index of an optical fiber preform (2) is measured from the state of bending of a light ray (4) passing across the optical fiber preform (2), so that the refractive index distribution of the optical fiber preform (2) is found on the basis of the angle of bending of the light ray calculated from a specific relation between a light ray start position (8) and a light ray detection position (9). The surface of a light source (1) is scanned by a knife-edge (6) and the light ray start position (8) on the light source is determined depending on the interception of the light ray (4) by the knife-edge (6) or the de-interception of the light ray, thereby learning the start position (8) of the detected light ray (4) on the light source (1).

Abstract: An integrated optical chip device for molecular diagnostics comprising a tunable laser cavity sensor chip using heterodyned detection at the juncture of a sensor laser and a reference laser, and including a microfluid chip to which the sensor chip is flip-chip bonded to form a sample chamber that includes exposed evanescent field material of the tunable laser cavity to which fluid to be diagnosed is directed.

Abstract: The present invention provides a method and system for controlling mineral scale deposition from a formation fluid. The rate at which scaling is occurring is measured in real time using an attenuated total reflectance probe and a photometer. The results are then used to determine whether to increase, decrease or leave unchanged addition of anti-scaling additives.

Abstract: In a process of manufacturing a semiconductor device, after a gate oxide film is formed, the thickness of the gate oxide film is measured by measuring an exposure period defined from a time at which the oxide film is formed to a time at which the thickness of the oxide film is measured. In addition, if necessary, the measurement of the oxide film is corrected to determine the real thickness based on the exposure period. Accordingly, the thickness of the gate oxide film can be measured accurately.

Abstract: Biochemical devices comprising a sensing surface that is at least partially covered by a nanocrystalline metal oxide semiconductor film which provides a recipient surface for immobilizing biochemical species on. The film has a mesoporous surface that gives up to a 1000 increase in biochemical species adsorption when compared to a flat surface. The biochemical devices comprising these surfaces can be optical and electrochemical biosensors and reactors for synthetic or biodegradation reactions.

Abstract: A new method is provided for monitoring silicon quality, the new method is applied at the time of pre-salicidation of the silicon substrate. The optical refractive index of the pre-salicide substrate is monitored, this monitoring provides insight into the quality of the silicon substrate at that time of a substrate processing cycle.

Abstract: An apparatus for handling liquids and including a lighting installation for lighting an approximately punctiform illumination point in the room, an approximately punctiform light-receiving device having a photodetector for providing a measuring signal dependent on the intensity of the light received, an imaging system for imaging the illumination point onto the approximately punctiform light-receiving device, and an evaluation device for detecting the approaching of an interface between two media of different refractive indices to the illumination point by evaluating the measuring signals provided by the photodetector.

Abstract: A method for detecting a substance or substances in a sample or in a matrix of samples combining detection methods that are, on the one hand, based on direct detection with integrated optical (bio)chemo-sensitive waveguide grating structures and, on the other hand, based on a mass-spectrometric detection effected by way of a desorption process. The method permits an increase in detection security and/or detection sensitivity.

Abstract: A method for designing and tuning a refractive index of a magnetic fluid is performed by adjusting some characteristic parameters. The characteristic parameters include the type of carrier, the type of magnetic particles, the concentration of the magnetic ingredient; the wavelength of an intended light onto the magnetic fluid layer; the strength of applied magnetic field; the sweep rate of the magnetic field; the direction of the applied magnetic field; the strength of applied magnetic field associated with the thickness of the magnetic fluid layer; and the strength of applied magnetic field associated with the temperature. A magnetic fluid with a designed value of refractive index under zero magnetic field is synthesized by carefully selecting the carrier and the volume concentration of the magnetic particles, and this value can further be tuning around the designed value by changing the forgoing characteristic parameters.

Abstract: An optical sensor for volatile organic compounds includes a light transmission medium and a porous medium, having an interface therebetween. A light source directs a beam of light into the light transmission medium at an incidence angle with respect to the interface. A detector is provided for measuring an intensity of light reflected by the interface or transmitted by the porous medium. The light transmission medium and the porous medium have different mediums of refraction to create a total internal reflection condition. The condition is gradually deteriorated as the porous medium is exposed to volatile organic compounds, since the adsorption of the compounds modifying the index of refraction of the porous medium.

Abstract: A method of reducing the effects of varying environmental conditions on a measuring instrument includes thermally insulating a measuring unit such that the effects of variations of environmental conditions on selected components of the measuring unit are substantially reduced, while allowing dissipated heat generated within the measuring unit to leave the measuring unit. The method also includes controlling a first temperature in the measuring unit by means of a control loop which includes a temperature sensor and means to influence the first temperature in the measuring unit in such a way that temperatures at locations with selected components are kept substantially constant.

Abstract: The invention relates to a refractometer and to a refractive index measuring method. The invention consists in directing an incident light ray onto an interface consisting of a medium of known refractive index and of the medium studied, then in measuring the intensity of the reflected light ray. The ratio between the intensity of the incident ray and the intensity of the reflected ray allows the refractive index of the medium studied to be calculated by means of Fresnel's formulas.

Abstract: The invention relates to a refractometer comprising an optical module (4) arranged floatingly inside a housing structure, which module comprises an optical window (2) to be positioned in a process fluid (3), and means for forming an illuminating beam and for directing it into the process fluid (3) through the optical window (2) and for directing back the part of the illuminating beam that is reflected from the process fluid, and further, means for watching the image formed in said manner. The optical module (4) is arranged to be supported against the housing structure by means of sealing (5) arranged between the optical window (2) and the housing structure. In order to provide a device suitable for difficult conditions, the housing structure part (6) in contact with the process fluid (3) against which the optical window (2) is arranged to be supported via sealing (5) is formed of a material that is chemically durable, mechanically rigid and durable and has good thermal conductivity.

Abstract: The invention relates to a portable refractometer comprising a depression (7) for samples, located on an insertion tip (11) in such a way that once the insertion tip (11) has penetrated a liquid or a fruit, a sufficient quantity of the sample liquid remains in the depression (7) for samples, thus wetting a measuring surface (4) that is delimited in said depression by a transparent body. The refractive index of the wetting liquid can be determined by measuring the intensity of an optical beam that is reflected by the measuring surface (4).

Abstract: The invention relates to refractometry and attenuated reflectance spectrometry in a wellbore environment. Specifically, it pertains to a robust apparatus and method for measuring refractive index of fluids along a continuum (rather than in steps), and for measuring attenuated reflectance spectra, and for interpreting the measurements made with this apparatus to determine a variety of formation fluid parameters. The present invention provides a method and apparatus to distinguish between gas and liquid based on the much lower index of refraction of gas. It can also be used to monitor fluid sample clean up over time. The refractive index of a wellbore fluid is determined from the fraction, R, of light reflected off the interface between a transparent window that has a known refractive index and this fluid. Preferably, the refractive index is measured at some wavelength of light for which the fluid is not highly attenuating but is optimally attenuating.

Abstract: In order to measure an electrical voltage in an electrooptical voltage converter, polarized light at two wavelengths is sent through the medium (1). On the output side, the light is passed through a polarizer (10) and the remaining signal is measured. In order to compensate for the temperature dependency of the electrooptical coefficients, the measurement results at the two wavelengths are compared with one another, and that voltage value which is consistent with both measurements is used.

Abstract: The invention relates to a method and to a device for detecting dispersive effects on the measurement along a line of sight according to the principle of phase or pulse modulation. The propagation times of electromagnetic radiation of at least two different carrier wavelengths are measured along a path. A first carrier wavelength in a wavelength range without molecular or atomic absorption of atmospheric gases (B) is selected and a second carrier wavelength in a wavelength range with molecular or atomic absorption, preferably in a spectral range with effective spectral lines, of atmospheric gases (B) is selected, and the dispersive effects are calculated from at least two measured propagation times of the electromagnetic radiation.

Abstract: An optical configuration for measuring a difference in refractive index between a first sample and a second sample comprises partitioned first and second optical interfaces symmetrically illuminated by an illumination beam to provide first and second partial beams defined by the refractive index of the first and second samples, respectively. A linear scanned array is aligned in a meridional plane of the optical configuration for detection purposes, and an optical multiplexor is provided upstream of the linear scanned array for receiving the first and second partial beams and defining first and second optical channels carrying optical signal information corresponding to the first and second partial beams. The optical multiplexor switches between optical channels, such that the linear scanned array detects either the first or second optical channel at a given time. Thus, differential measurements are possible using a single linear array.