Abstract:
PROBLEM TO BE SOLVED: To provide a gas detection method and a gas detector with a low degree of dependence on temperature and on a sudden change in a wavelength. SOLUTION: This gas detector comprises at least one surface emission laser light source 1 and at least one light sensor 8 for detecting a light beam passing through a specimen chamber 4 containing a gas to be measured. A detection signal by the light sensor 8 is inputted into lock-in amplifiers 19 and 20 directly or after being differentiated in terms of time in a differential computing unit 25, and outputted therefrom as two different 2f detection signals, that is, measurement signals S MI and S MA . Here, f is the wavelength-modulated frequency of a light source. A ratio between the two measurement signals gives accurate gas concentration. In gas detection, at least first and second modulation reference signals S 2f0 and S 2f1 are used of a frequency 2f of twice the modulated frequency f of the laser light source. This gas detector excels conventional techniques since the use of the 2f modulation reference signals provides a result independent of absolute strength measurement, that is, independent of laser temperature change or mode hopping. Further, a merit is also provided that measurement accuracy is independent of gas concentration. COPYRIGHT: (C)2007,JPO&INPIT
Abstract translation:要解决的问题:提供对温度低依赖性和波长突然变化的气体检测方法和气体检测器。 解决方案:该气体检测器包括至少一个表面发射激光光源1和至少一个光传感器8,用于检测通过包含待测气体的试样室4的光束。 光传感器8的检测信号直接输入到锁定放大器19和20,或者在微分计算单元25中在时间上被区分后输出,作为两个不同的2f检测信号,即测量信号S MI SB>和S MA SB>。 这里,f是光源的波长调制频率。 两个测量信号之间的比率提供了精确的气体浓度。 在气体检测中,使用激光光源的调制频率f的两倍的频率2f的至少第一和第二调制参考信号S SB2f0和S 。 该气体检测器优于常规技术,因为使用2f调制参考信号提供独立于绝对强度测量的结果,即独立于激光器温度变化或模式跳变。 此外,还提供了测量精度与气体浓度无关的优点。 版权所有(C)2007,JPO&INPIT
Abstract:
A system and method are disclosed for gas sensing over a wide tunable wavelength range provided by one or more quantum cascade lasers. A laser beam is generated within the wide tunable wavelength range, which is given by the sum of the wavelength ranges from the individual lasers. Gas sensing or detection is achieved by obtaining an infrared absorption spectrum for a sample contained in one or more cells having different path lengths for the laser beam.
Abstract:
According to various embodiments, a Raman spectroscopy method is provided for reduction of background fluorescence signal. The method may utilize a high speed optical chopper configured to periodically interrupt the laser light beam between the laser light source and the sample; and using the high speed optical chopper to provide a synchronized time-gated optical window for receiving mostly Raman signal while rejecting most or some of the fluorescence signal transmitted from the sample in response to the laser light beam before reaching the sensor
Abstract:
Verfahren und Gasanalysator zur Messung der Konzentration einer Gaskomponente in einem Messgas Zur Messung der Konzentration einer Gaskomponente in einem Messgas (1), wird eine wellenlängenabstimmbare Laserdiode (3) mit einem Strom (i) angesteuert und das von der Laserdiode (3) erzeugte Licht (4) durch das Messgas (1) auf einen Detektor (5) geführt. Dabei wird der Strom (i) in periodisch aufeinanderfolgenden Abtastintervallen variiert, um eine interessierende Absorptionslinie der Gaskomponente wellenlängenabhängig abzutasten. Der Strom (i) kann zusätzlich im Sinne der Wellenlängenmodulationsspektroskopie mit geringer Frequenz und kleiner Amplitude sinusförmig moduliert werden. Ein von dem Detektor (5) erzeugtes Messsignal (14) wird zu einem Messergebnis (16) ausgewertet. Um das Messsignal-Rausch-Verhältnis zu verbessern und so bei gleicher Messstrecke eine deutlich niedrigere Nachweisgrenze zu erreichen, wird der Strom (i) mit mindestens einer hohen (HF-)Frequenz im GHz-Bereich moduliert, so dass keine Wellenlängenmodulation stattfindet. Die Amplitude der HF-Modulation wird unter Ausnutzung des linearen Aussteuerbereichs der Laserdiode (3) mit maximaler Höhe gewählt. Das Messsignal (14) wird vor seiner Auswertung an der Stelle der mindestens einen hohen Frequenz demoduliert.
Abstract:
The present invention concerns a method for determining at least one absorption band in a spectrum, the method at least comprising the steps of: - providing a measured absorption spectrum from the sample, - providing a calculation spectrum, - from the calculation spectrum, extracting at least one absorption band, - calculating a residual spectrum by removing each extracted absorption band from the calculation spectrum, - testing whether a predefined stop criterion is fulfilled by the residual spectrum, - if the stop criterion is not fulfilled, using the residual spectrum as the calculation spectrum and iterating the extracting step, the forming step, the calculating step and the testing step, and - if the stop criterion is fulfilled, outputting each extracted absorption band.
Abstract:
A method of stabilizing output signals from a cascade optical detector in an optical spectroscopy apparatus, particularly a reflectance anisotropy spectroscopy apparatus, and generating a stable output photocurrent signal from the optical detector by controlling the supply voltage to the detector in constant photocurrent mode, wherein control is performed at a relatively low voltage, i.e. lower than 10 V.