Disclosed herein is an all-digital phase and timing correction procedure for coherent averaging in dual-comb and multiheterodyne spectroscopy—applicable to any dual-comb spectroscopy setup. It can account for large frequency/phase instabilities of the used sources, yielding a significant reduction of the noise pedestal and an increase in signal-to-noise ratio (SNR) of the radio frequency (RF) beat notes. This technique is computationally efficient and can be conveniently implemented either as a post-processing algorithm or in a real-time data acquisition and processing platform without the necessity of adding any additional optical elements to the dual-comb spectroscopy system. By implementing this technique, the performance of any comb- or comb-like-source-based DCS system with a sufficient degree of mutual coherence between the optical modes can be improved in terms of SNR and number of spectroscopically-usable RF beat notes. The described technique is compatible with a DC-centered RF spectrum, where the negative frequencies are folded to the positive domain to double the number of beat notes within the detector bandwidth. The technique enables coherent averaging over extended time-scales even for free-running combs, thus increasing the sensitivity of absorption and dispersion DCS measurements.

A system for real-time assessment of systemic hydration includes a light source configured to operably emit light of first and second wavelengths; means for delivering the emitted light to a target site to excite at least one first spot at the target site, and collecting Raman scattering light scattered from the target site at a plurality of second spots; a detector coupled with said means for obtaining a plurality of spatially offset Raman spectra from the collected Raman scattering light, each spatially offset Raman spectrum corresponding to a respective second spot of the target site and associated with a depth of tissues at which the Raman scattering light is scattered; and a controller configured to process the plurality of spatially offset Raman spectra so as to identify spectral features from the plurality of spatially offset Raman spectra, and assess systemic hydration from the identified spectral features.

Systems and methods disclosed herein provide for detecting gas by: illuminating, with a controllable illuminator system, a scene with light including radiation within the infrared (IR) wavelength range; controlling the illuminator system to emit light at a first wavelength corresponding to a first absorption level of a gas and at a second wavelength corresponding to a second absorption level of a gas, such that an equal amount of radiant energy over a time period is emitted onto the scene for each of said first and second wavelengths; and capturing a first IR image of the scene being illuminated with light at said first wavelength and a second IR image of the scene illuminated with light at said second wavelength, and comparing said first and second IR images to determine whether a characteristic for at least one specific gas is represented in said first and/or second IR images.

Systems and methods disclosed herein provide for detecting gas by: illuminating, with a controllable illuminator system, a scene with light including radiation within the infrared (IR) wavelength range; controlling the illuminator system to emit light at a first wavelength corresponding to a first absorption level of a gas and at a second wavelength corresponding to a second absorption level of a gas, such that an equal amount of radiant energy over a time period is emitted onto the scene for each of said first and second wavelengths; and capturing a first IR image of the scene being illuminated with light at said first wavelength and a second IR image of the scene illuminated with light at said second wavelength, and comparing said first and second IR images to determine whether a characteristic for at least one specific gas is represented in said first and/or second IR images.

In an embodiment, an apparatus (100) is described. The apparatus comprises an infrared, IR, generating system (102). The IR generating system comprises a first IR source (104) configured to produce IR radiation for forming a first IR beam (106) in a first spectral band. The IR generating system further comprises a second IR source (108) configured to produce IR radiation for forming a second IR beam (110) in a second spectral band. The apparatus further comprises a beam manipulation system (112) configured to combine a beam path of the first and second IR beams and direct the first and second IR beams along the beam path through a gas sample region (114). The apparatus further comprises an IR detection system (116) configured to detect an intensity of the first and second IR beams after passage through the gas sample region. The IR detection system is configured to produce a signal (118) from which an indication of a concentration of a target gas in the gas sample region can be derived.

A beating spectroscopy device includes: first and second quantum cascade lasers; a quantum cascade detector; and a sample holder configured to hold a sample on an optical path between the second quantum cascade laser and the quantum cascade detector. Lights from the first and second quantum cascade lasers are detected by the quantum cascade detector while a wavelength of the light from the second quantum cascade laser is changed to scan a frequency of a beating signal having a frequency in accordance with a wavelength difference between the lights from the first and second quantum cascade lasers.

A beating spectroscopy device includes: first and second quantum cascade lasers; a quantum cascade detector; and a sample holder configured to hold a sample on an optical path between the second quantum cascade laser and the quantum cascade detector. Lights from the first and second quantum cascade lasers are detected by the quantum cascade detector while a wavelength of the light from the second quantum cascade laser is changed to scan a frequency of a beating signal having a frequency in accordance with a wavelength difference between the lights from the first and second quantum cascade lasers.

The invention relates to a photometer (30) for analysing the composition of a sample gas. The photometer comprises an infra-red (IR) source (20) configured to direct a first plurality of pulses (40) of IR radiation through the sample gas to an IR detector (26), at least two of the first plurality of pulses being of different wavelength. The photometer further comprises an ultraviolet (UV) source (32) configured to generate a second plurality of pulses (38) of UV radiation for conveyance to a UV detector (36), at least two of the second plurality of pulses being of different wavelength. A path selection arrangement (22, 42-50) is configured to selectively convey different ones of the second plurality of pulses (38) to one of the sample gas and the UV detector (36). The photometer further comprises processing circuitry coupled to the IR source (20), the UV source (32), the IR detector (26), the UV detector (36) and the path selection arrangement (22, 42-50). The processing circuitry is configured to (i) select the wavelength to be used for a given UV pulse of the second plurality of pulses (38), (ii) receive a plurality of detection signals from each of the IR detector (26) and the UV detector (36) and (iii) based on the detection signals, determine a concentration of at least one component of the sample gas. A method for analysing the composition of a sample gas is also disclosed.

The invention relates to a photometer (30) for analysing the composition of a sample gas. The photometer comprises an infra-red (IR) source (20) configured to direct a first plurality of pulses (40) of IR radiation through the sample gas to an IR detector (26), at least two of the first plurality of pulses being of different wavelength. The photometer further comprises an ultraviolet (UV) source (32) configured to generate a second plurality of pulses (38) of UV radiation for conveyance to a UV detector (36), at least two of the second plurality of pulses being of different wavelength. A path selection arrangement (22, 42-50) is configured to selectively convey different ones of the second plurality of pulses (38) to one of the sample gas and the UV detector (36). The photometer further comprises processing circuitry coupled to the IR source (20), the UV source (32), the IR detector (26), the UV detector (36) and the path selection arrangement (22, 42-50). The processing circuitry is configured to (i) select the wavelength to be used for a given UV pulse of the second plurality of pulses (38), (ii) receive a plurality of detection signals from each of the IR detector (26) and the UV detector (36) and (iii) based on the detection signals, determine a concentration of at least one component of the sample gas. A method for analysing the composition of a sample gas is also disclosed.

Methods, apparatuses, and systems for improving gas detecting devices are provided. An example gas detecting device may include a receiver element. In some examples, the receiver element may include a sample filter component and a reference filter component. In some examples, the sample filter component may be positioned coaxially with the reference filter component.