To eliminate the defects of inconvenience operation,puff-by-puff detection that can't be done online which caused by using non-dispersive infrared method to detect CO in cigarette mainstream smoke,a new online detection system using tunable diode laser absorption spectroscopy(TDLAS)technology is established based on LabVIEW.The system hardware mainly consists of a smoking machine for cigarette smoking and a TDLAS controller for CO detection.By processing the data acquired from the lock-in amplifier that housed in TDLAS controller,the concentration of CO in cigarette mainstream smoke is calculated.Thus the content of CO in each puff can also be calculated with definite volume.The result shows that the system can effectively detect the content of CO in cigarette mainstream smoke puff-by-puff and online with a stable and reliable operation.

Tunable diode laser absorption spectroscopy (TDLAS) technology combined with wavelength modulation spectroscopy (WMS) technology is an important technique for trace gas detection. Detected with the lock-in amplifier, the second harmonic signal obtained after demodulation is analyzed to get the gas absorption information. However, the second harmonic signal is affected by noise which reduces the accuracy and stability of the detection system. To improve the signal to noise ratio (SNR) of the TDLAS detection system, a denoising method based on Gabor transform is proposed for second harmonic signal noise reduction. Taking the CH4 absorption spectrum at 1 653.72 nm as an example, the effectiveness of the noise reduction method is verified through simulation and experiments. The simulation results show that the signal to noise ratio for the second harmonic signal of 0 dB can be improved 15.73 dB with Gabor transform-based denoising method. Experimental results show that with the Gabor transform-based denoising method, the linear correlation coefficient r can be as high as 0.996 59 between the second harmonic peak value and the CH4 concentration in the range of 0.001%~0.02%. At the same time, the detection accuracy and stability of the system have been improved significantly.

In order to provide an alternative method for cigarette authenticity discrimination,a method based on near-infrared reflectance spectroscopy(NIRS) was experimented.The sample was dried(2 hours at 40 ℃),ground and sieved(40 mesh) prior to NIRS test to eliminate errors caused by the variation of moisture content and size of cut tobacco.Three samples were tested and the accuracy was 97.52%,96.94%,and 98.61%,respectively.The results showed that it was feasible to use NIRS for cigarette authenticity discrimination.