A single-channel gas concentration measurement method and apparatus. According to the method, a radiant source is employed to generate a measuring signal, the measuring signal is subsequently directed to a measurement object containing a gas mixture to be measured, the measuring signal is subsequently bandpass filtered using at least two passband wavelengths, and the filtered measuring signals are detected by a detector. According to the invention, the bandpass filtering step is implemented by a single electrostatically tunable, short-resonator Fabry-Perot interferometer.

Single-channel gas concentration measurement method and apparatus using a short-resonator Fabry-Perot interferometer

A Fabry-Perot filter device for selectively transmitting three wavelength bands of infrared radiation, including a reference light band, wherein the filter device comprises a fixed mirror formed on a substrate; a movable mirror arranged opposite to the fixed mirror with a gap formed therebetween so that the movable mirror is displaced with respect to the fixed mirror by applying an external force; a fixed electrode formed on the fixed mirror; and a movable electrode formed on the movable mirror and arranged opposite to the fixed electrode wherein the movable electrode is displaced by applying a potential difference across the fixed and movable electrodes so that the width of the gap is varied in at least three steps, whereby at least three wavelength bands of infrared radiation are selectively transmitted through the filter device.

Fabry-Perot filter, wavelength-selective infrared detector and infrared gas analyzer using the filter and detector

A spectrally tunable optical detector and methods of manufacture therefore are provided. In one illustrative embodiment, the tunable optical detector includes a tunable bandpass filter, a detector and readout electronics, each supported by a different substrate. The substrates are secured relative to one another to form the spectrally tunable optical detector.

Spectrally tunable detector

A spectral image input device has an image forming optical system for forming an image of image light on an image forming surface and a phase difference generating unit disposed anterior to the image forming surface in the direction of image light travel. The phase difference generating unit constitutes, sequentially in the direction of image light travel, a polarizer for transmitting only polarized light in a specific direction, an optical element formed of a solid material having a birefringence, and arranged such that the principal refraction index axis is inclined 45° relative to the polarization angle of the analyzer, the optical element generating a phase difference in accordance with the wavelength of the image light based on the difference in the physical thickness of the optical element in the direction of image light travel and an analyzer for transmitting only the image light of a polarization angle of 90° relative to the direction of the polarized light of the polarizer.

Spectral image input device

A test object (13) is analyzed electronically, i.e. without the use of photographic film. The invention generates a pair of laterally-dis­placed images of the object (13) which interfere with each other to pro­duce a pattern that can be recorded without a high-resolution detector. The object (13) is illuminated with at least partially coherent light. Reflected light (25, 27) from the object (13) is directed through a bi­refringent material (15), a lens system (17), a polarizer (19), and then to an image detector (21), such as a video camera. The birefringent ma­terial (15) causes non-parallel beams originating from a unique pair of points (29, 31) on the object to become nearly parallel, and orthogonally polarized. The polarizer (19) modifies the polarization of the parallel beams so that they will interfere with each other. Because the interfer­ing light beams are nearly parallel, the spatial frequency of the inter­ference pattern is sufficiently low that the pattern can be recorded by a low-resolution detector, such as a video camera. Interference patterns due to the superposition of two laterally-displaced images of the same object (13) are recorded while the object is in an undeformed and a de­formed state. A computer (23) compares these interference patterns and produces a resultant pattern which depicts the deformation of the test object (13). Because photographic film is not needed, the invention can analyze objects very rapidly. Also, since the interference pattern is derived from pairs of distinct points on tDe object (13), the invention directly provides information on strain.

Apparatus and method for electronic analysis of test objects

Interferometric device for the detection and/or analysis of gas, of the type comprising an optical assembly forming the image of a light source on the sensitive element of the detector, comprising a photoelastic modulator comprising a silica or fluorine plate associated to a piezoelectric ceramic to vibrate in order to give the plate a birefringency variable by compression, having an axis parallel to that of a birefringent plate and an interferential filter constituted by a grating multiplexer device; and having application to the interferometric detection of gas through high-sensitivity.

Interferometric device for detecting gas

Process and interferometric device for detecting and measuring the concentration, in a single operation, of all gases, having almost periodic absorption structures, contained in a gaseous mixture, each of the gases being associated with a characteristic path difference. Luminous flux is analyzed after passage through a cell containing the mixture, using to a multiple-wave interferometer, for example, a Fabry-Perrot interferometer, in which the inside faces of plates therein are highly reflective, and one of which plates is displaceable at a constant speed, it thus being possible to sweep a very wide range of path difference. Analysis of the output signal is performed frequency band by frequency band, by seeking the maximum.

Process for the simultaneous detection of several gases in a gaseous mixture, and equipment for using the process

DISPOSITIF INTERFEROMETRIQUE POUR LA DETECTION ETOU L'ANALYSE DE GAZ, DU GENRE COMPRENANT UN ENSEMBLE OPTIQUE FORMANT L'IMAGE D'UNE SOURCE LUMINEUSE SUR L'ELEMENT SENSIBLE D'UN DETECTEUR. IL COMPORTE UN MODULATEUR PHOTOELASTIQUEM COMPRENANT UNE LAME DE SILICE OU DE FLUORINE ASSOCIEE A UNE CERAMIQUE PIEZOELECTRIQUE MISE EN VIBRATION POUR DONNER A LADITE LAME UNE BIREFRINGENCE VARIABLE PAR COMPRESSION, D'AXE PARALLELE A CELUI D'UNE LAME BIREFRINGENCEL ET UN FILTRE INTERFERENTIEL CONSTITUE PAR UN DISPOSITIF MULTIPLEXEUR A RESEAUXH. APPLICATION A LA DETECTION INTERFEROMETRIQUE DE GAZ A GRANDE SENSIBILITE.

Detecteur interferometrique de gaz

The subject of the present invention is an installation for remotely detecting, locating and quantifying a gas in an atmosphere. This installation comprises a two-wave interference spectrometer comprising a modulable-transmission spectral filter with a birefringent assembly with a large angular field adjusted to the characteristic path difference of the gas being searched for, placed between a polariser P and an analyser A, one of which is set in rotation in order to modulate the interference phenomenon, this assembly being preceded by an objective O and an interference filter F adapted to transmit light only in the absorption band of the gas being searched for, the installation furthermore comprising a device for scanning the object space, which the atmosphere constitutes, by an elementary field, the flux emitted by this field being collected by the spectrometer, an image acquisition device placed downstream of the said spectrometer and forming an image which is processed by a module which is synchronised with the position of the rotating analyser, this module being adapted to supply a video signal s which is a function of the concentration of the gas in the field scanned, the installation furthermore comprising means for utilising the said video signal s.

Method and installation for remotely detecting, locating and quantifying a gas in an atmosphere and modulable-transmission spectral filter intended for implementing this method and producing this installation

Fortunato Gerard

Papers

Interferometric device for detecting gas

Process for the simultaneous detection of several gases in a gaseous mixture, and equipment for using the process

Detecteur interferometrique de gaz

Method and installation for remotely detecting, locating and quantifying a gas in an atmosphere and modulable-transmission spectral filter intended for implementing this method and producing this installation

Detecteur de gaz par interferometrie