An absorption spectrometer which measures a gas component concentration in a measured gas and which operates via wavelength modulation spectroscopy, wherein the light wavelength of a wavelength-tunable light source is periodically varied over a gas component absorption line of interest and simultaneously sinusoidally modulated with a high frequency and a low amplitude signal, and wherein the measurement signal of a detector is demodulated in a phase-sensitive manner at the frequency and/or a harmonic of the frequency and further analyzed, where modulation starts in each period or each n-th period with the frequency in a time interval before the beginning of the time function and is performed with a higher amplitude than during the time function to demodulate the measurement signal in a phase-synchronous manner, where a device provided for the phase-sensitive demodulation is synchronized during the time interval such that a cable for transmitting synchronization signals is no longer necessary.

An imaging system includes: a first light source that emits first light having a spectrum including discrete first frequency components arranged at first frequency intervals; a second light source that emits second light having a spectrum including discrete second frequency components arranged at second frequency intervals, the second frequency intervals being different from the first frequency intervals; a mixing optical system that mixes the first light and the second light to generate third light including at least one optical beat the intensity of which changes at a beat frequency expressed by the difference between at least one of the discrete first frequency components and at least one of the discrete second frequency components; an imaCCging element having a variable sensitivity in an exposure period; and a control circuit that changes the sensitivity of the imaging element at the beat frequency of the at least one optical beat.

Embodiments of the disclosure are drawn to apparatuses and methods for anomalous gas concentration detection. A spectroscopic system, such as a wavelength modulated spectroscopy (WMS) system may measure gas concentrations in a target area. However, noise, such as speckle noise, may interfere with measuring relatively low concentrations of gas, and may lead to false positives. A noise model, which includes a contribution from a speckle noise model, may be used to process data from the spectroscopic system. An adaptive threshold may be applied based on an expected amount of noise. A speckle filter may remove measurements which are outliers based on a measurement of their noise. Plume detection may be used to determine a presence of gas plumes. Each of these processing steps may be associated with a confidence, which may be used to determine an overall confidence in the processed measurements/gas plumes.

A method for generating a illumination dual-comb signal that provides a low frequency train of interferograms (180) readable by a regular video-rate camera (160) comprising N pixels and a sampling frequency of V Hz to extract hyperspectral information (170), the method comprising providing a monochromatic signal, splitting the monochromatic signal in two split monochromatic signals, frequency shifting each monochromatic signal with an offset frequency below

[00001]$\frac{V}{2}\mathrm{Hz},$

generating two frequency combs having a difference in repetition below

[00002]$\frac{V}{2}\mathrm{Hz}$

by a nonlinear modulation of the two split monochromatic signals, generate the illumination dual-comb signal, Illuminating a target and employing a video-rate camera (160) to read a low frequency train of interferograms (180) based on a reflected and/or transmitted signal of the illumination dual-comb signal and performing Fourier transformation of the low frequency train of interferograms (180) detected by each pixel from the N pixels to extract the hyperspectral information (170).

A method for obtaining chemical and/or material specific information of a sample based on scattered light. The method comprises receiving detection data comprising at least two images. Each image is indicative of the intensity of scattered light i) for incident light of a different wavelength, or ii) for incident light of a different polarization state, or iii) of a different polarization state. The scattered light comprises an elastic scattering component that is due to Rayleigh scattering of the incident light in at least a portion of the sample. Alternatively, each image is indicative of the intensity of scattered light i) of a different wavelength, or ii) for incident light of a different polarization state, or iii) of a different polarization state, wherein the scattered light comprises an inelastic scattering component that is due to Raman scattering of the incident light in at least a portion of the sample. The method further comprises determining the chemical and/or material specific information of the sample based on the change in intensity of the elastic scattering component in dependence on the change in wavelength and/or the change in polarization state of the incident and/or scattered light.

A method for coherent multidimensional spectroscopy may comprise illuminating a location in a sample with a set of m coherent light pulses, each coherent light pulse having an initial frequency ω.sub.m and an initial wave vector {right arrow over (k)}.sub.m, wherein m≥2, to generate a coherent output signal having an initial frequency ω.sub.output=Σ±ω.sub.m and an initial wavevector wave vector {right arrow over (k)}.sub.output=Σ±{right arrow over (k)}.sub.m; scanning a first coherent light pulse of the set of m coherent light pulses across a set of i frequency values, wherein i≥2, the set of i frequency values including the first coherent light pulse having initial frequency ω.sub.1; scanning, simultaneously, a second coherent light pulse of the set of m coherent light pulses across a set of i correlated frequency values, the set of i correlated frequency values including the second coherent light pulse having initial frequency ω.sub.2, wherein each correlated frequency value is associated with a corresponding frequency value of the set of i frequency values as a correlated frequency grouping; and detecting the coherent output signal. Each correlated frequency value is selected so that the coherent output signal generated at each correlated frequency grouping equals the initial frequency ω.sub.output and the coherent output signal generated at each correlated frequency grouping equals the initial wavevector {right arrow over (k)}.sub.output.

Detector data representative of an intensity of light that impinges on a detector after being emitted from a light source and passing through a gas over a path length can be analyzed using a first analysis method to obtain a first calculation of an analyte concentration in the volume of gas and a second analysis method to obtain a second calculation of the analyte concentration. The second calculation can be promoted as the analyte concentration upon determining that the analyte concentration is out of a first target range for the first analysis method.

An embodiment of a system for measuring trace gas concentration is described that comprises a laser absorption spectrometer configured to detect an absorbance measure from a trace gas, as well as a temperature value and a pressure value that correspond to an environment in a gas cell; and a computer having executable code stored thereon configured to perform a method comprising: receiving the absorbance value, the temperature value, and the pressure value; defining a fitting range associated with the trace gas; applying a curve fitting model in the fitting range to the absorbance value using the temperature value and the pressure value as model parameters; and producing a concentration measure of the trace gas.

Provided is a terahertz wave spectrometry system that is capable of identifying analyzing target molecules contained in an analyte even if the analyte contains water, by activating a water remover to remove water according a comparison of absorption spectrums so that water in the analyte is easily removed without causing the analyzing target molecules to disappear due to decomposition or denaturation.

A photo-thermal speckle spectroscopy device having an infrared laser, a visible laser, a foam, and a camera. The infrared and visible lasers are focused on the foam, which causes the visible laser to scatter. A camera records the speckle pattern, which shifts when the IR laser is turned on. The related method of photo-thermal speckle spectroscopy is also disclosed.