Semiconductor laser transmittance analysis system

Abstract

The invention discloses a semiconductor laser transmissibility analysis system, which comprises an optical transmitter unit, an optical receiver unit and a signal analysis unit. The optical transmitter unit and the optical receiver unit are arranged on one side or two sides of the medium to be inspected. The optical transmitter unit comprises a semiconductor laser and a first convergent lens; the end of the first convergent lens corresponding to the semiconductor laser is an inclined plane; the optical distance of the principal ray of the laser beam between the semiconductor laser and the first convergent lens is shorter or equal to 7mm; The A-A sectional plane of the middle part of the first convergent lens is a random geometric shape, and the diameter of the smallest cover circle of the A-A sectional plane is bigger or equal to 25mm; the light sent out by the semiconductor laser goes into the medium to be inspected after going through the first convergent lens. The invention also discloses another semiconductor laser transmissibility analysis system.

Description

technical field [0001] The invention relates to a photoelectric analysis system, in particular to a semiconductor laser transmittance analysis system which analyzes and obtains measured parameters by measuring laser beam transmittance. Background technique [0002] The semiconductor laser analysis technology that analyzes the measured parameters by measuring the laser beam transmittance has a wide range of applications. For example, the semiconductor laser absorption spectrum analysis technology can be used to analyze the concentration of chemical components in gases and liquids, and can also analyze the temperature and velocity of gases, etc. For another example, the dust concentration can also be analyzed by analyzing and measuring the laser beam transmittance. The following uses gas concentration analysis as an example to introduce its application. Semiconductor laser absorption spectroscopy gas analysis technology is a high-sensitivity gas analysis technology. When the...

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Problems solved by technology

In addition, affected by various environmental factors (temperature changes, mechanical vibrations, etc.), the distance between the surfaces of optical components often changes slightly; due to the short wavelength of the laser, small changes will cause phase changes between multiple beams. The obvious change of the difference, thereby significantly changing the transmittance change caused by the above-mentioned multi-beam interference, that is to say, the distribution of etalon noise with the optical frequency will be affected by various environmental factors, which will bring difficulties to accurate gas parameter analysis.

Figure 4 shows the gas single-line absorption spectrum measured by the analysis system without etalon noise, and the signal-to-noise ratio of the gas single-line absorption spectrum measured with etalon noise will decrease significantly, as shown in Figure 5

For fixed-wavelength measurement methods, small wavelength shifts or changes in environmental factors will also cause changes in the apparent transmittance of the optical system, thereby affecting measurement accuracy

[0010] There are some deficiencies in the above-mentioned analysis system: 1) The structure is relatively complicated, and a converging lens is used to converge the divergent light, and at the same time, tempered glass is required to realize explosion-proof; due to the use of multiple optical components, the number of reflective surfaces is increased, and the etalon is increased. Optical noise reduces the measurement accuracy and measurement sensitivity; 2) When measuring the concentration of some media, such as measuring the concentration of trace moisture and oxygen, due to the semiconductor laser, the converging lens, the flameproof glass, the light receiving device, the convergence There are many spaces between the lens and the flameproof glass. If there are gas components to be measured in these spaces, it will affect the measurement. The current method is to either use nitrogen purging or nitrogen filling. To avoid the existence of these measured gases in these spaces; but purging increases the complexity of the system, and the potting method will produce greater measurement inaccuracy when leakage occurs, especially when the concentration of the measured medium is low, such as The order of ppm, therefore, both the light emitting unit 1 and the light receiving unit 2 need to be strictly sealed, and the requirements for leak prevention are high, which further increases the complexity of system design and manufacturing

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