For tracking a plurality of objects in a three-dimensional space two-dimensional pictures objects are recorded with two black and white cameras out of two different imaging directions. Both first pictures and second pictures of the two cameras are simultaneously exposed at two points in time in equal ways, a point in time at which the second pictures are exposed for a first time following to a point in time at which the first pictures are exposed for a last time at a much shorter interval than the two points in time of exposure of both the first and second pictures. First and second distributions of real positions of the individual objects are determined from their images in the first and second pictures, respectively; and temporally resolved trajectories of the individual objects in the three-dimensional space are determined from the first and second distributions of real positions.

Spectroscopic apparatus and methods incorporating a gas sensor configured to detect low concentration gases, including gases that are hazardous volatiles are provided. Low concentration gases can comprise gases where detection of concentrations on the order of parts-per-million (ppm), and in many embodiments part-per-billion (ppb) is required. The gas may be a species, such as, for example hydrogen sulfide (H.sub.2S) that may be produced in drilling and/or volcanic eruptions. The spectroscopic apparatus and methods are configured to operate in particular atmospheres where gas detection can be challenging, such as in ambient air and/or in space where various contaminants may be present. The spectroscopic apparatus and methods may incorporate a long path length detector, such as, for example, a cavity-enhanced absorption spectrometer. The methods and apparatus further incorporate a wavelength modulation technique to improve the signal-to-noise ratio.

The present application discloses a terahertz based self-feedback system for detecting atmospheric high-risk chemical. In the system, a detecting device is configured to detect information of an atmospheric high-risk chemical. A mechanical adjusting device is configured to adjust a height and an orientation of the detecting device to obtain the information at different heights and orientations. A mobile carrying device is configured to drive the detecting device to move to obtain the information of the atmospheric high-risk chemical at different locations. A processing device is configured to process the information and feedback an instruction to adjust the height and the orientation of the detecting device and control the mobile carrying device to move. The processing device is also configured for imaging the information of the atmospheric high-risk chemical. The present application also discloses terahertz based methods for detecting a distribution and a leakage source of the atmospheric high-risk chemical.

A gas detection system, comprising a sample gas inlet, a reference gas inlet and a gas modulation valve alternatingly connecting one of the sample gas inlet and the reference gas inlet to a gas sensor, is characterized in that a selective transfer filter is located in the gas flow path connecting the gas modulation valve and the gas sensor.

For tracking a plurality of objects in a three-dimensional space two-dimensional pictures objects are recorded with two black and white cameras out of two different imaging directions. Both first pictures and second pictures of the two cameras are simultaneously exposed at two points in time in equal ways, a point in time at which the second pictures are exposed for a first time following to a point in time at which the first pictures are exposed for a last time at a much shorter interval than the two points in time of exposure of both the first and second pictures. First and second distributions of real positions of the individual objects are determined from their images in the first and second pictures, respectively; and temporally resolved trajectories of the individual objects in the three-dimensional space are determined from the first and second distributions of real positions.

A gas detection system, comprising a sample gas inlet, a reference gas inlet and a gas modulation valve alternatingly connecting one of the sample gas inlet and the reference gas inlet to a gas sensor, is characterized in that a selective transfer filter is located in the gas flow path connecting the gas modulation valve and the gas sensor.

Spectroscopic apparatus and methods incorporating a gas sensor configured to detect low concentration gases, including gases that are hazardous volatiles are provided. Low concentration gases can comprise gases where detection of concentrations on the order of parts-per-million (ppm), and in many embodiments part-per-billion (ppb) is required. The gas may be a species, such as, for example hydrogen sulfide (H.sub.2S) that may be produced in drilling and/or volcanic eruptions. The spectroscopic apparatus and methods are configured to operate in particular atmospheres where gas detection can be challenging, such as in ambient air and/or in space where various contaminants may be present. The spectroscopic apparatus and methods may incorporate a long path length detector, such as, for example, a cavity-enhanced absorption spectrometer. The methods and apparatus further incorporate a wavelength modulation technique to improve the signal-to-noise ratio.

In some examples, a method includes transmitting first light pulses according to a pre-determined pulse pattern in a first measurement period. The method also includes transmitting second light pulses according to the pre-determined pulse pattern in a second measurement period consecutive to the first measurement period, in which at least some of the first and second light pulses being unequally spaced in time across the first and second measurement periods. The method also includes receiving first detection signals representing detection of the first light pulses. The method also includes receiving second detection signals representing detection of the second light pulses. The method also includes providing a first light scattering measurement signal representing the first measurement period responsive to the first detection signals. The method also includes providing a second light scattering measurement signal representing the second measurement period responsive to the second detection signals.

A method and a system for detecting the presence of propellant gas in a gaseous sample exploit laser light especially in the 3.30-3.5 m range. The propellant can be propane, n-butane, i-butane, dimethyl ether, methyl ethyl ether, HFA 134a, HFA 227, or any other propellant exhibiting absorption in the requisite wavelength range. The presence of the application of this method in leak testing of propellant-containing containers such as aerosols or fuel canisters, permits high-speed, high accuracy leak detection capable of replacing existing testing methods.

In some examples, a method includes transmitting first light pulses according to a pre-determined pulse pattern in a first measurement period. The method also includes transmitting second light pulses according to the pre-determined pulse pattern in a second measurement period consecutive to the first measurement period, in which at least some of the first and second light pulses being unequally spaced in time across the first and second measurement periods. The method also includes receiving first detection signals representing detection of the first light pulses. The method also includes receiving second detection signals representing detection of the second light pulses. The method also includes providing a first light scattering measurement signal representing the first measurement period responsive to the first detection signals. The method also includes providing a second light scattering measurement signal representing the second measurement period responsive to the second detection signals.