Key Laboratory of Opto Electronics Information Technology

Tianjin, China

Key Laboratory of Opto Electronics Information Technology

Tianjin, China
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Yu M.,Tianjin University | Yu M.,Key Laboratory of Opto Electronics Information Technology | Huang H.,Tianjin University | Huang H.,Key Laboratory of Opto Electronics Information Technology | And 6 more authors.
Optics Express | Year: 2017

Traditional methods of discrimination for Stokes polarimetric imaging use grayscale images, in which the difference of the polarimetric properties is only reflected by the difference of grayscale. In this paper, we propose a method of colorimetric discrimination and classification for Stokes polarimetric imaging by the composed color polarimetric image, in which the objects with different polarization properties can appear in different colors. We show with real-world experiment that compared with the traditional method for the grayscale Stokes scalar image, the method proposed in this paper has a better performance for distinguishing objects with different polarization properties. © 2017 Optical Society of America.


Song Z.,Tianjin University | Li X.,Tianjin University | Li X.,Key Laboratory of Opto electronics Information Technology | Liu T.,Tianjin University | Liu T.,Key Laboratory of Opto electronics Information Technology
Optik | Year: 2017

Previous study shows that if the total integration time of intensity measurements is fixed, the variance of DOLP estimator depends on the distribution of the degree of linear polarization for two intensity measurements. However, the optimal time dependents on the quantity being measured. In this paper, the expected variance is used to define a cost function for optimization of the estimator, which overcomes the above limitation. Actually, minimizing the expected variance is equivalent to minimizing the noise power of estimator, so as to improve the precision of the estimator. We also deduce the closed-form solution of the optimal distribution of the integration time for additive Gaussian noise by employing Lagrange multiplier method. According to the theoretical analyses, it is shown that the variance of DOLP estimator can be decreased for most values of DOLP without prior knowledge, and the proposed method statistically improve the measurement accuracy of the polarimetry system. © 2017 Elsevier GmbH


Lu Q.,Tianjin University | Lu Q.,Key Laboratory of Opto electronics Information Technology | Li B.,Tianjin University | Li B.,Key Laboratory of Opto electronics Information Technology | And 3 more authors.
Optics Letters | Year: 2017

We report the lifetime enhancement of light-induced refractive index grating by applying a bias field during writing. In comparison with the lifetime of about 10 hours of the photorefractive grating prepared without a bias field, the lifetime of the grating with a 4 kV∕cm bias field can be prolonged to 7.5 years, which is obtained from the dynamic behavior of grating visualized and monitored with digital holographic microscopy. The higher the bias field is applied, the longer the dark decay time of grating can be achieved. The enhanced lifetime of phase grating is attributed to polar nanoregions oriented by external field. This effect is of great significance for electro-holographic device applications. © 2017 Optical Society of America.


Li X.,Tianjin University | Li X.,Key Laboratory of Opto electronics Information Technology | Hu H.,Tianjin University | Hu H.,Key Laboratory of Opto electronics Information Technology | And 3 more authors.
Optics Express | Year: 2017

We consider the Mueller matrix ellipsometry (MME) measuring the ellipsometric parameters of the isotropic sample and the anisotropic sample under certain conditions in the presence of either Gaussian additive noise or Poisson shot noise. In this case, the ellipsometric parameters only relate to partial elements in Mueller matrix, and we optimize the instrument matrices of polarization state generator (PSG) and analyzer (PSA) to minimize the total measurement variance for these elements, in order to decrease the variance of the estimator of ellipsometric parameters. Compared with the previous instrument matrices, the optimal instrument matrices in this paper can effectively decrease the measurement variance and thus statistically improve the measurement precision of the ellipsometric parameters. In addition, it is found that the optimal instrument matrices for Poisson shot noise are same to those for Gaussian additive noise, and furthermore, the optimal instrument matrices do not depend on the ellipsometric parameters to be measured, which means that the optimal instrument matrices of MME proposed in this paper can be widely applied in various cases. © 2017 Optical Society of America.


Zhang Z.,Beijing Normal University | Chen X.,Beijing Normal University | Yu P.,Beijing Normal University | Zhang Q.,Jining Medical University | And 17 more authors.
Neuropsychopharmacology | Year: 2015

Nitric oxide (NO), a gaseous neurotransmitter, has been implicated in the pathogenesis of schizophrenia. Accordingly, several polymorphisms of the gene that codes for the main NO-producing enzyme, the nitric oxide synthase 1 (NOS1), have been found to convey a risk for schizophrenia. This study examined the role of NOS1 gene polymorphisms in cognitive functions and related neural mechanism. First, with a sample of 580 schizophrenia patients and 720 healthy controls, we found that rs3782206 genotype had main effects on the 1-back task (P=0.005), the 2-back task (P=0.049), the AY condition of the dot-pattern expectancy (DPX) task (P=0.001), and the conflict effect of the attention network (ANT) test (P<0.001 for RT differences and P=0.002 for RT ratio) and interaction effects with diagnosis on the BX condition of the DPX (P=0.009), the AY condition of the DPX (P<0.001), and the Stroop conflict effect (P=0.003 for RT differences and P=0.038 for RT ratio). Simple effect analyses further showed that the schizophrenia risk allele (T) of rs3782206 was associated with poorer performance in five measures for the patients (1-back, P=0.025; BX, P=0.017; AY, P<0.001; ANT conflict effect (RT differences), P=0.005; Stroop conflict effect (RT differences), P=0.019) and three measures for the controls (for the 2-back task, P=0.042; for the ANT conlict effect (RT differences), P=0.013; for the ANT conflict effect (RT ratios), P=0.028). Then, with a separate sample of 78 healthy controls, we examined the association between rs3782206 and brain activation patterns during the N-back task and the Stroop task. Whole brain analyses found that the risk allele carriers showed reduced activation at the right inferior frontal gyrus (IFG) during both tasks. Finally, we examined functional connectivity seeded from the right IFG to the dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex under three conditions (the N-back task, the Stroop task, and the resting state). Results showed reduced connectivity with the DLPFC for the risk allele carriers mainly in the Stroop task and the resting state. Taken together, results of this study strongly suggested a link between NOS1 gene polymorphism at rs3782206 and cognitive functions and their neural underpinnings at the IFG. These results have important implications for our understanding of the neural mechanism underlying the association between NOS1 gene polymorphism and schizophrenia. © 2015 American College of Neuropsychopharmacology. All rights reserved.


Huang B.,Tianjin University | Huang B.,Key Laboratory of Opto electronics Information Technology | Liu T.,Tianjin University | Liu T.,Key Laboratory of Opto electronics Information Technology | And 4 more authors.
Optics Express | Year: 2015

In polarimetric imaging, the uneven illumination could cause the significant spatial intensity fluctuations in the scene, and thus hampers the target detection. In this paper, we propose a method of illumination compensation and contrast optimization for Stokes polarimetric imaging, which allows significantly increasing the performance of target detection under uneven illumination. We show with numerical simulation and realworld experiment that, based on the intensity information contained in the polarization information, the contrast can be effectively enhanced by proper approach, which is of particular importance in practical applications with spatial illumination fluctuations, such as remote sensing. © 2015 Optical Society of America.


Li X.,Tianjin University | Liu T.,Tianjin University | Liu T.,Key Laboratory of Opto Electronics Information Technology | Huang B.,Tianjin University | And 4 more authors.
Optics Express | Year: 2015

We consider the typical Stokes polarimetry system, which performs four intensity measurements to estimate a Stokes vector. We show that if the total integration time of intensity measurements is fixed, the variance of the Stokes vector estimator depends on the distribution of the integration time at four intensity measurements. Therefore, by optimizing the distribution of integration time, the variance of the Stokes vector estimator can be decreased. In this paper, we obtain the closed-form solution of the optimal distribution of integration time by employing Lagrange multiplier method. According to the theoretical analysis and real-world experiment, it is shown that the total variance of the Stokes vector estimator can be significantly decreased about 40% in the case discussed in this paper. The method proposed in this paper can effectively decrease the measurement variance and thus statistically improves the measurement accuracy of the polarimetric system. © 2015 Optical Society of America.


Hu H.,Tianjin University | Hu H.,Key Laboratory of Opto electronics Information Technology | Liu T.,Tianjin University | Liu T.,Key Laboratory of Opto electronics Information Technology | Zhai H.,Nankai University
Optics Express | Year: 2015

The dynamic process of material ejection and shock wave evolution during one single femtosecond laser pulse ablation of aluminum target in water and air is experimentally investigated by employing pumpprobe technique. Shadowgraphs and digital holograms with high temporal resolution are recorded, which intuitively reveal the characteristics of femtosecond laser ablation in the water-confined environment. The experimental result indicates that the liquid significantly restrict the diffusion of the ejected material, and it has a considerable effect on the attenuation of the shock wave. In addition, the expansion Mach wave generated by the ultrasonic expansion of the shock wave is observed. © 2015 Optical Society of America.


Cao X.-L.,Institute of Laser and Opto electronics | Yao J.-Q.,Institute of Laser and Opto electronics | Zhong K.,Institute of Laser and Opto electronics | Xu D-G.,Institute of Laser and Opto electronics | Xu D-G.,Key Laboratory of Opto electronics Information Technology
Optical Engineering | Year: 2013

Abstract. The intersubband absorptions between the conduction ground state and excited states in Al0.5Ga0.5As/GaAs/Al0.2Ga0.8As multiple asymmetric quantum well (AQW) have been investigated based on optical difference frequency in the 9 to 11 μm region. Under an intense resonant excitation from a dual-wavelength CO2 laser, the saturation intensity of intersubband absorption for pump waves is estimated to be 0.3 MW/cm2. As the well width variation, the position of absorption peak for pump waves and the absorption of terahertz (THz) wave by DFG show concomitant changes. For an AQW of 7 nm deep well-width and 27 nm total well-width, the maximum of absorption for the THz wave is 6.01×105 m-1 when the two pump wavelengths are 9.69 and 10.64 μm, respectively. These manipulative transitions in AQW can be applied to tunable optical semiconductor devices and implemented in THz wave devices to achieve additional functionalities. © 2013 Society of Photo-Optical Instrumentation Engineers (SPIE).


Tian Q.,Tianjin University | Tian Q.,Key Laboratory of Opto Electronics Information Technology | Yang Y.,Tianjin University | Yang Y.,Key Laboratory of Opto Electronics Information Technology | And 4 more authors.
Optics and Lasers in Engineering | Year: 2014

Laser line scanning 3D digitising systems have a wide range of applications. Their working performance is mainly determined by the system calibration procedure and is also affected by the working conditions, CCD camera imperfections, and object surface optical characteristics. Therefore, a comprehensive evaluation of working performance is necessary before and during use. This study proposes an experimental method for the performance evaluation of a laser line scanner (LLS) with 8 scanning sensors developed in our laboratory. This method first obtains the dense point clouds of standard parts composed of disks, cylinders, and squares. Next, the single-layer point clouds located in horizontal planes of different heights are fitted using the least squares method to obtain the enclosed contours S. Three parameters, namely, the standard deviation of the distance distribution between points and S, the mean distance of the distance distribution, and the shape feature sizes, are used to evaluate the performance. The proposed method evaluates both the scanner as a whole and each scanning sensor. Using this method, more comprehensive information can be acquired to evaluate the scanner performance. The experimental results show that the absolute dimension size error and relative error are less than 5 mm and 3%, respectively, and the relative shape error is less than 2%; therefore, the evaluated LLS system can meet the requirements for human anthropometry applications. Although each scanning sensor has different random and systematic error, these errors are the function of measurement depth. These conclusions are helpful for the further use of this scanner system and can be utilised to optimise this LLS system further. © 2013 Elsevier Ltd.

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