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Laser heterodyne spectroscopic measurement technique[1] has been proved to be a powerful and effective remote sensing tool for measurements of greenhouse gases in the atmospheric column[2-6]. In the present work, we report the development of a portable all-fiber coupled dual-channel laser heterodyne radiometer (LHR) and its field deployment. Two DFB lasers operating at 1650.9 nm and 1603.6 nm are used for the remote measurements of column CH4 and CO2, respectively. A fiber optic switch is used to modulate and split the collected sunlight into two channels for simultaneous measurements of both target greenhouse gases. Custom-made preamplifiers combined with digital lock-in amplifiers are used to extract the laser heterodyne signals. The spectral resolution of the instrument is about 0.00442 cm-1, and the signal-to-noise ratio of the measured spectrum of about 250 is achieved with 0.8 s average time per sampling datum. The developed LHR instrument was successfully deployed to a field atmospheric observation experiment (in Dachaidan district, Qinghai province, China).The experimental detail including the LHR instrument integration, dual-channel measurement results of column CH4 and CO2 and preliminary data inversion results will be presented and discussed.Acknowledgments. The project was supported by the national key R&D program of China (2017YFC0209705). The authors thank the financial supports from the CPER CLIMIBIO program, the Labex CaPPA project (ANR-10-LABX005).References[1] D. Weidmann, T. Tsai, N. A. Macleod, G. Wysocki, Opt. Lett. 36 (2011) 1951-1953.[2] E. L. Wilson, A. J. DiGregorio, G. Villanueva, C. E. Grunberg, et al., Appl. Phys. B 125 (2019) 211-219.[3] D. S. Bomse, J. E. Tso, M. M. Flors, J. H. Miller, Appl. Opt. 59 (2020) B10-B17.[4] J. Wang, G. Wang, T. Tan, G. Zhu, C. Sun, Z. Cao, W. Chen, X. Gao, Opt. Express 27 (2019) 9610-9619[5] A. Rodin, A. Klimchuk, A. Nadezhdinskiy, D. Churbanov, et al., Opt. Express 22 (2014) 13825-13834.[6] E. L. Wilson, M. L. McLinden, J. H. Miller, H. R. Melroy, et al., Appl. Phys. B 114 (2014) 385-393.

Osteopetrosis is a rare congenital bone disorder, characterized by systemic osteosclerosis due to a deficiency of or functional defect in osteoclasts. Autosomal dominant osteopetrosis (ADOP) is the most common form with a late onset, a stable condition, relatively few symptoms and a good prognosis. Few studies to date have reported successful total hip arthroplasty (THA) in patients with ADOP and its operative difficulties. We herein describe a case of left hip osteoarthritis in a patient with OP via THA in order to share our experience during the treatment process. The patient was a 52-years-old female with osteopetrosis who was referred to our department due to a history of left hip pain with activity limitation for 20 years. The patient reported no history of fracture or family history. The patient underwent THA in the left hip. At the 6-month, 1- and 2-year follow-up, the components were in a good position and the patient remained asymptomatic and pain-free. Therefore, THA may be a feasible treatment option when patients with ADOP suffer from painful hip osteoarthritis.

Laser heterodyne is a kind of technique based on coherent detection with high sensitivity and spectral resolution for spectrum measurements. For these reasons, it has been widely used in many research fields, such as trace gases’ detection of earth’s or terrestrial planets’ atmosphere. However, when the laser heterodyne spectrometer is used for measuring the spectrum, the instrument line shape (ILS) function usually smooth the spectrum, which affects the inversion results of the gas column density. In previous researches, the radio frequency (RF) filter response function was usually used as the ILS, but recent studies indicated that the ILS without consideration of the influence of lock-in amplifier was not precise enough. In order to obtain the ILS function of the laser heterodyne spectrometer, the main factors which influence the ILS are analyzed, including the RF filter bandwidth, integral time and low-pass filter of lock-in amplifier, and the process is based on the principle of laser heterodyne technology and the flow of heterodyne signal processing. The presented ILS is the convolution of RF filter, wavelength variation in the integral time and the low-pass filter. In addition, for testing the effectiveness of the ILS in this paper, the laser heterodyne spectrometer which was built in our laboratory is used for the multiple measurement of the absorption of water vapor and methane in the band of 3.53 \begin{document}${\text{μm}}$\end{document} and the column densities are retrieved with different ILS. The experimental results show that the actual resolutions of the laser heterodyne spectrometer are about 0.005 cm–1 and 0.025 cm–1 when the integral times are set to be 10 ms and 100 ms respectively. Furthermore, the RF filter response function and the ILS function presented in the paper are respectively used in the procedure of water vapor and methane inversion. The results show that when the ILS function used for the retrieval, the sum of squared residual reduces about 16% and the residuals at the peak of methane absorption reduces almost 100% compared with the scenario when using the RF filter function. Above all, the comprehensive analysis of the laser heterodyne spectrometer in this paper indicates that the ILS function is more precise than pioneering studies and this work will be helpful for retrieving the precise profiles of trace gases.

In this paper we evaluated several typical matching costs including CENSUS, mutual information (MI) and the normalized cross correlation using the ISPRS Stereo Matching Benchmark datasets for DSM generation by stereo matching. Two kinds of global optimization algorithms including semi-global matching (SGM) and graph cuts (GC) were used as optimization method. We used a sub-pixel method to obtain more accurate MI lookup table and a sub-pixel method was also used when computing cost by MI lookup table. MI itself is sensitive to partial radiation differences. So we used a kind of cost combined MI and CENSUS. After DSM generation, the deviation data between the generated DSM and Lidar was statistics out to compute the mean deviation (Mean), the median deviation (Med), the standard deviation (Stdev), the normalized median absolute deviation (NMAD), the percentage of deviation in tolerance etc., which were used to evaluate the accuracy of DSM generated from different cost.

It has been proven that cavity enhanced absorption spectroscopy is a high sensitive spectral technique. The aim of our study was to apply this spectral technique to the detection of carbon monoxide with a narrow line width tunable DFB diode laser and high Q factor optical cavity. Absorption signals were extracted from a measurement recording the average of 20 highest light intensities that leak out of the cavity. The absorption spectrum of CO centered at 6354.18 cm −1 was recorded; the experiment results indicate that cavity enhanced absorption spectroscopy could produce accurate high resolution spectrum. A detection sensitivity about 5.687 × 10 −7 cm −1 has been achieved in a 45 cm-long cell.

Fifteen new absorption lines were observed when studying CO2 absorption spectroscopy by wavelength modulation technique with a distributed feedback laser. The overtone spectra of CO2 around 1.31μm and the corresponding spectral parameters (i.e. positions, intensities, self-broadening coefficients) are presented. The intensity of the weakest line detected is 2.25163×10−27cm−1/(molecule.cm−2) at the pressure of 667Pa, with a corresponding absorption of 3.88×10−8.

We have recorded the transmission spectrum of an optical cavity absorption cell filled with methane gas using a tunable continuous-wave light source in the mid-infrared region. To determine the absorption strength of the gas, we have measured the linewidth of the cavity fringe. This method corresponds to frequency-domain measurements of cavity ring-down spectroscopy (CRDS) because the linewidth is the Fourier transform of the photon lifetime from which the absorption strength is derived in CRDS. The absorption strengths determined from the present linewidth measurements indicate excellent agreements with both those derived from the transmittance measurements and those calculated from line parameters listed in the HITRAN 2004 database.

The high-resolution absorption spectrum of CH4 at 1.51 μm is observed by direct absorption spectroscopy technique with a White absorption cell. Multi-peak fitting technique is adopted to reveal line positions and line intensities of CH4 from 6608 cm−1 to 6625 cm−1. Special attention is paid on the determination of the line positions, and the accuracy is better than ±0.002 cm−1. A minimum measurable absorption of 2.1×10−8 (3σ) has been achieved based on the measured direct absorption spectroscopy.

Fifteen new absorption lines are observed when studying CO2 absorption spectroscopy by wavelength modulation (WM) technique with a distributed feedback laser. The overtone spectra of CO2 around 1.31 μm and the corresponding spectral parameters (i.e. positions, intensities, self-broadening coefficients) are presented. The intensity of the weakest line detected is 2.25163×10−27 cm−1/(molecule.cm−2) at the pressure of 5 Torr, with a corresponding absorption of 3.88×10−8.

Water vapor in a sealed glass container processed by lyophilization is a main factor for drug metamorphism. The key to knowing whether there is a leakage occurring in the container is how to detect water concentration and pressure in the sealed container quickly and accurately. In the present paper, a strong absorption line of H2O near 1.39 m is carefully selected to avoid the interference of neighboring transitions. A distributed feedback laser semiconductor laser near 1.396 m is employed as the light source with a power of 10 mW and typical linewidth of 2 MHz by combining with tunable diode laser absorption spectroscopy technique, the concentrations and pressures of water vapor in the sealed container are successfully detected under static condition and dynamic condition. In order to isolate the interference absorption from the ambient water vapor in the air, a differential absorption technique is employed in our experiment, which makes our system simpler than routine nitrogen purging based system. During the measurement, the second harmonic signal is utilized for measuring the concentration and pressure, the concentration is retrieved by the peak value while the pressure is calculated by the full width at half maximum. For the measurement of concentration ranging from 0.2% to 12%, the linear correlation coefficient between the real values and the inversed values and the standard deviation ratio are 0.9978 and 4.81%, respectively. For the measurement of pressure, the correlation coefficient and standard deviation ratio are 0.982 and 5.6%, respectively. The minimum detection limits of the concentration and pressure are 400 ppm and 2.5 Torr, respectively. Moreover, in order to test the system for on-line applications in the pharmaceutical industry, measurements are performed in vials which are placed on a rotary stage to simulate the process of the assemble line. In particular, the amplitude of sinuous signal without absorption is used as the reference signal to validate whether the vial is in the optical path. Besides, this amplitude is also utilized to normalize the laser power. The results show that our system can handle about 300 bottles in one minute, which can meet well the requirements for rapid and real-time detections. This system can be applied directly to the medicine bottle on-line detection, and multicomponent detection can also be realized by employing two or more lasers (e.g. H2O, oxygen, etc.). In the future, we plan to build a system for detecting water vapor and oxygen simultaneously, as oxygen is another import indicator for drug metamorphism.

We present a signal-processing system developed for enhancing the sensitivity of absorption measurement based on tunable diode laser wavelength modulation spectroscopy. A signal-to-noise ratio enhancement of an order of magnitude was observed when digital signal-processing algorithms were applied to wavelength modulation spectrometers in the near-infrared，at the same time a new spectra was found by observation of CO2 near 1.53 μm. These algorithms include digital low-pass filters, multiple averages, and a least squares fit. Digital signal processing has a practical advantage over other noise suppression techniques because it is easy to implement and adapt able to all experiments.