Abstract: A method and system are provided with which it is possible to detect non-firing and untimely firing events in internal combustion and, if necessary, the temperature of the gas in the exhaust gas pipe. This is performed in general by measuring the speed of sound and determining the phase angle between the sender and receiver either arranged on different sides of the exhaust gas pipe or on the same side of the exhaust gas pipe. The receiver, depending on the measurement principle, can include one, two, or in special applications three receivers. Additionally, if necessary, it is possible to suppress the structure-borne sound influence on a speed of sound measurement with low cost and high stability.

Abstract: A sensor arrangement and method for measuring the speed of sound in a gas to determine gas characteristics, such as composition, temperature and/or humidity of the gas. The sensor arrangement includes a sound sender, first and second sound receivers, and a signal processing unit. The sound sender and sound receivers are arranged such that the travel distance of the sound provided by the sender to the first receiver is different from the travel distance of the sound provided by the sender to the second receiver. Further the arrangement includes the signal processing unit connected with the sender and the receivers which operates to determine the gas characteristics.

Abstract: The invention relates to a laser diode structure, specifically for use in gas detection, with a hermetically sealed housing with electrical connections having a bottom and a window. A laser diode chip and a temperature control system for the laser diode chip are provided in the housing. A thermo element in the form of a Peltier element forms the temperature control system, and is connected via a lower flat surface to the bottom of the housing and via an upper flat surface to the laser diode chip, with a temperature-controlled beam shaping element as collimator provided between the laser diode chip and the window of the housing that acts on a laser beam emerging from a laser aperture of the laser diode chip before it passes through the window. The beam shaping element is in contact with the laser diode chip and is preferably connected via a boundary surface to the laser aperture with surface-to-surface contact or adhesively, or is made in one piece together with the laser aperture.

Abstract: An TDLS gas sensor with a measuring pick-up to be arranged outside of the interior chamber of an incubator or a climate chamber of similar design, and with an absorption pick-up to be arranged inside the interior chamber, and also with a window separating the measuring area and absorption area for the atmospheric separation of the laser diode from the interior chamber of the incubator, with the window being arranged at an angle to the axis of the laser beam emitted by a laser diode, and with the optronic components being arranged in a block of material in the measuring pick-up, said block being made of thermally well-conducting material and serving as heat sink, and with a heating system for the window in the measuring pick-up. In addition, a process for measuring the moisture and the carbon dioxide concentration.

Abstract: A laser diode structure for generating a collimated or divergent laser beam, preferably for application in gas detection, with a laser diode arranged in a closed housing, with the housing comprising a housing bottom, an exit window, electrical connections, a temperature control device for the laser diode, and an optical element for influencing the laser beam. The temperature control device carrying the laser diode is arranged on the housing bottom and the optical element is positioned at a distance from the laser diode. The invention proposes an electrically controllable power device for the cyclic alteration of the position and/or alignment of the optical element in relation to the laser diode so that the optical path length for the laser beam in the housing changes periodically.

Abstract: The invention relates to a laser diode structure, specifically for use in gas detection, with a hermetically sealed housing with electrical connections having a bottom and a window. A laser diode chip and a temperature control system for the laser diode chip are provided in the housing. A thermo element in the form of a Peltier element forms the temperature control system, and is connected via a lower flat surface to the bottom of the housing and via an upper flat surface to the laser diode chip, with a temperature-controlled beam shaping element as collimator provided between the laser diode chip and the window of the housing that acts on a laser beam emerging from a laser aperture of the laser diode chip before it passes through the window. The beam shaping element is in contact with the laser diode chip and is preferably connected via a boundary surface to the laser aperture with surface-to-surface contact or adhesively, or is made in one piece together with the laser aperture.

Abstract: A combined gas sensor device allowing the measuring of the concentration of a gas by tunable diode laser spectrometry as well as by resonant photo-acoustics within one housing. A laser beam used for laser spectrometry is sent across the openings of a measuring cell usually used for resonant photo-acoustic determination. Thus, both measuring principles use the same gas sensing module with a minimum of space consumption, so that the device can be produced with minimum dimensions. Further, a common opto-electronics and electronics platform can be used which reduces the overall costs of such a combined gas sensor.

Abstract: A method for performing quartz-enhanced photoacoustic spectroscopy of a gas, includes providing a light source configured to introduce a laser beam having at least one wavelength into the gas such said at least one molecule within in the gas is stimulated generating an acoustic signal, accumulating the acoustic signal in a resonant acoustic detector, generating a resonant absorption signal (SA) relative to the gas concentration by at least one tuning fork serving as resonant acoustic detector, generating additionally a resonant intensity signal (SI) proportional to the intensity of the laser beam travelling through the gas, and providing an output signal (SGC) from said absorption signal (SA) and said intensity signal (SI) being independent of the intensity of the light relative to the presence or concentration of the gas.

Abstract: A combined gas sensor device allowing the measuring of the concentration of a gas by tunable diode laser spectrometry as well as by resonant photo-acoustics within one housing. A laser beam used for laser spectrometry is sent across the openings of a measuring cell usually used for resonant photo-acoustic determination. Thus, both measuring principles use the same gas sensing module with a minimum of space consumption, so that the device can be produced with minimum dimensions. Further, a common opto-electronics and electronics platform can be used which reduces the overall costs of such a combined gas sensor.

Abstract: A method for etalon suppression in a gas detection device by determining an etalon fringe period during a calibration step without gas in dependency of the DC drive current. A measuring signal which is a function of the gas absorption and substantially independent of an intensity modulation of an initial light signal at an initial frequency (f) is generated by determining a first pre-measuring signal when the laser source is operated at the center of the gas absorption peak, a second pre-measuring signal when the laser source is operated with a DC drive current below the gas absorption peak of the gas to be detected, and a third pre-measuring signal when the laser source is operated with a DC drive current above said gas absorption peak, with a difference between said DC drive currents which corresponds to the etalon fringe period determined in a calibration step before.

Abstract: A gas detection method by using a photo acoustic near infrared gas sensor with a laser source and such a gas sensor comprising at least one amplitude modulated laser source, a gas chamber for receiving the gas to be detected, a microphone attached to the gas chamber, a photo detector for receiving the laser light after having passed through the gas filled gas chamber, processing means comprising a modulation frequency generator for providing a modulation signal for the at least one laser source and a control means for determining the gas concentration. The laser source changes it output wavelength across each cycle of the amplitude modulation between a minimum wavelength and a maximum wavelength. The result of this measurement scheme is that during each modulation cycle, the laser source scans its complete available wavelength range so that the absorption features of the target gas are levelled out to a mean value.

Abstract: The invention proposes a method for etalon suppression in a gas detection device by determining an etalon fringe period during a calibration step without gas in dependency of the DC drive current. A measuring signal which is a function of the gas absorption and substantially independent of an intensity modulation of an initial light signal at an initial frequency (f) is generated by determining a first pre-measuring signal when the laser source is operated at the center of the gas absorption peak, a second pre-measuring signal when the laser source is operated with a DC drive current below the gas absorption peak of the gas to be detected, and a third pre-measuring signal when the laser source is operated with a DC drive current above said gas absorption peak, with a difference between said DC drive currents which corresponds to the etalon fringe period determined in a calibration step before.

Abstract: The gas detector device comprises at least a VCSEL source and at least a light sensor for detecting a light beam having passed through a sample chamber containing a given gas to be detected. The detection signal of the sensor directly provided to or is time derivated by an electronic derivator and then provided to respective lock-in amplifiers in order to generate a two different 2f-detection, f being the frequency of a wavelength modulation of the source, and thus to provide two corresponding measuring signals the division of which gives a precise value of the gas concentration. The invention uses at least a first modulation reference signal at twice and a second modulation reference signal at twice of the modulation frequency of the laser source.

Abstract: A gas detector device comprises at least a VCSEL source (34, 36) and at least a light sensor (54, 56) for detecting a light beam (50, 52) having passed through a sample chamber (48) containing a given gas to be detected. The sensor is a photodiode in a first embodiment and its detection signal is time derivated by an electronic derivator (64) and then provided to two lock-in amplifiers (84, 86) in order to generate a F-detection and a 2F-detection, F being the frequency of a wavelength modulation of the source, and thus to provide two corresponding measuring signals the division of which gives a precise value of the gas concentration. In a second embodiment, the source is a pyroelectric sensor which directly provides a detection signal proportional to the time derivate of the light beam incident on this sensor. In this last case, the electronic derivator is thus eliminated.

Abstract: The gas detector device comprises at least a VCSEL source and at least a light sensor for detecting a light beam having passed through a sample chamber containing a given gas to be detected. The detection signal of the sensor directly provided to or is time derivated by an electronic derivator and then provided to respective lock-in amplifiers in order to generate a two different 2f-detection, f being the frequency of a wavelength modulation of the source, and thus to provide two corresponding measuring signals the division of which gives a precise value of the gas concentration. The invention uses at least a first modulation reference signal at twice and a second modulation reference signal at twice of the modulation frequency of the laser source.

Abstract: A gas detector device comprises at least a VCSEL source (34, 36) and at least a light sensor (54, 56) for detecting a light beam (50, 52) having passed through a sample chamber (48) containing a given gas to be detected. The sensor is a photodiode in a first embodiment and its detection signal is time derivated by an electronic derivator (64) and then provided to two lock-in amplifiers (84, 86) in order to generate a F-detection and a 2F-detection, F being the frequency of a wavelength modulation of the source, and thus to provide two corresponding measuring signals the division of which gives a precise value of the gas concentration. In a second embodiment, the source is a pyroelectric sensor which directly provides a detection signal proportional to the time derivate of the light beam incident on this sensor. In this last case, the electronic derivator is thus eliminated.

Abstract: The invention concerns an infrared sensor (2) comprising a plurality of pixels (12) having a structured layer (20) for infrared light absorption located at the sensor upper surface. The invention is characterised in that the absorption layer (20) is formed of colloidal particles, in particular graphite or metal oxide wafers embedded or sealed in a binder. The method for making such a sensor consists in forming the structured layer by deposit of the colloidal particles in accordance with a standard technique and then in eliminating partly the thus formed absorption layer to obtain a plurality of elementary absorption zones respectively associated with the plurality of pixels.

Abstract: Method for manufacturing a plurality of pyroelectric sensors by forming a thin pyroelectric film or layer on one face of a silicon wafer or substrate, wherein electric polarization of this film is provided between lower and upper electrodes defining pixels forming these sensors. In order to protect the wafer in the event of a short-circuit between two electrodes of a pixel, resistors are arranged in series with the lower or upper electrodes by connecting these electrodes to each other by subsets in order to carry out the electric polarization. Once this polarization has been carried out, the electric connections connecting the upper or lower electrodes are removed to allow each pixel to supply an elementary electric signal when the sensor is operating. In order to minimize the risk of short-circuits and in order to reduce the stray capacity of the electrodes, the upper and lower electrodes of the pixels are structured.

Abstract: Method for manufacturing a plurality of pyroelectric sensors by forming a thin pyroelectric film or layer on one face of a silicon wafer or substrate, wherein electric polarisation of this film is provided between lower and upper electrodes defining pixels forming these sensors. In order to protect the wafer in the event of a short-circuit between two electrodes of a pixel, resistors are arranged in series with the lower or upper electrodes by connecting these electrodes to each other by subsets in order to carry out the electric polarisation. Once this polarisation has been carried out, the electric connections connecting the upper or lower electrodes are removed to allow each pixel to supply an elementary electric signal when the sensor is operating. In order to minimise the risk of short-circuits and in order to reduce the stray capacity of the electrodes, the upper and lower electrodes of the pixels are structured.