Parallel unambiguous generalized phase-shifting and T-spline fitting algorithms for optical micro-structured surface 3D topography metrology.

3D topography metrology of optical micro-structured surfaces is critical for controlled manufacturing and evaluation of optical properties. Coherence scanning interferometry technology has significant advantages for measuring optical micro-structured surfaces. However, the current research faces difficulties of designing high accuracy and efficient phase shifting, and characterization algorithms for optical micro-structured surface 3D topography metrology. In this paper, parallel unambiguous generalized phase-shifting and T-spline fitting algorithms are proposed. To avoid phase ambiguity and improve the accuracy of the phase-shifting algorithm, the zero-order fringe is determined by the iterative envelope fitting with Newton's method, and the accurate zero optical path difference is determined by a generalized phase-shifting algorithm. In particular, the calculation procedures of the multithreading iterative envelope fitting with Newton's method and generalized phase shifting are optimized with the graphics processing unit-Compute Unified Device Architecture kernel function. Additionally, to fit the base form of optical micro-structured surfaces and characterize the surface texture and roughness, an effective T-spline fitting algorithm is proposed by optimizing the preimage of the T-mesh with image quadtree decomposition. Experimental results show that the surface reconstruction of optical micro-structured surfaces using the proposed algorithm is more accurate, and the efficiency is 10 times higher than that of current algorithms; the time of the surface reconstruction is less than 1 s. Compared with the current B-spline method, the accuracy of roughness characterization using the proposed T-spline algorithm is improved by more than 10%.

Freeform optics characterization with surface registration and fitting algorithms for optical point-based spatial path 3D topography metrology.

Accurate characterization of the form error for freeform optics is critical for controlled manufacturing and evaluation of optical properties. To solve the difficulty of current surface registration and fitting algorithms, and improve characterization accuracy of the form error of freeform optics for optical point-based spatial path 3D topography metrology, in this paper, improved surface registration and fitting algorithms are proposed, including a B-spline surface description of freeform optics, point orthogonal projection, registration parameter optimization, and B-spline fitting. Limited by the angular characteristics of an optical point-based sensor, the slope and reference frame of freeform optics must be flexibly adjusted, and polynomial surfaces are described and fitted as B-spline surfaces based on B-spline geometric invariance. To efficiently determine corresponding points on B-spline surfaces, the point orthogonal projection algorithm without Bezier subdivision is proposed using the first-order Newton method. Then, the iteration procedure of coordinate adjustment in sphere space using Lie algebra registration parameters is proposed to solve the difficulty of the current registration parameter optimization procedure. To fit a spatial path form error, the least squares B-spline fitting method is proposed to improve the Zernike method. Through simulation experiments, the proposed registration algorithm with good convergence can improve accuracy by one to two orders of magnitude compared with current registration algorithms. Through repeated experiments of a freeform prism, the proposed method can significantly improve the peak-to-valley and RMS accuracies compared with the stylus method, and characterize the mid-high frequency form error (about 200 nm) of a freeform prism.

Exploring the law of color presentation of double-sided heterochromatic digital printing for textile.

With the upgrading of production technology and design aesthetic of textile products, the development and application of double-sided digital printing technology have been gradually proposed in recent years. The production of double-sided heterochromatic digital printing requires high accuracy for color management, as in the production process, different input devices, display devices, and output devices each have varying color processing capabilities and color performance characteristics, which leads to the transfer of color between different devices and not being accurately reproduced. However, there is little research involved in the color formation laws in the design and production of double-sided heterochromatic digital printing. The purpose of this paper is to explore the prediction model of color presentation in double-sided heterochromatic digital printing. Due to the influence of the fabric thickness, the gap between the textile structure, and the infiltration rate of the printing pigments, the color of each side in double-sided, heterochromatic printing results often differs from the designed color. In this paper, taking chiffon fabric, which is one of the thinnest and has the strongest permeability in silk fabric, as an example fabric base, 24 colors from six hue angles and four chromas were selected as experimental colors. According to the color gamut of the digital printing machine, 15 out of 24 colors were selected as experimental colors. These 15 colors were printed on two sides in pairs to generate 225 color pairs as double-sided experimental samples. For these experimental samples, this paper conducts experiments from both subjective and objective aspects through the combination of subjective evaluation of psychophysics experiments and objective instrument measurement. Through the analysis of experimental data, the color difference prediction under the subjective model (R2 = 0.74) and objective model (R2 = 0.85) are given, respectively. The dominant color prediction model (R2 = 0.75) during double-sided heterochromatic digital printing has also been built. The combination of the three models can predict the color regularity of double-sided heterochromatic digital printing on silk, which may have a certain significance for the design and development of silk double-sided heterochromatic digital printing products.

Developing a digital archive system for imperial Chinese robe in the Qing Dynasty.

The digital archive of cultural heritage provides new opportunities for the protection of the cultural heritage and the development of online museums. One of the essential requirements for the digitization is to achieve accurate color reproduction. Taking the Imperial Chinese robes in the Qing Dynasty as an example, this study aims to develop a digital achieve system to digitize the robes using a high-end imaging system and accurately reproduce their color properties on a display. Currently, there has been very limited study focused on the color reproduction of silk fabrics or other textile materials. The conventional color management process using a traditional color chart, however, may not be suitable for the reproduction of silk fabrics because they have very high gloss. To address this difficulty, a unique "Qianlong Palette" color chart, consisting of 210 silk fabric samples, has been specifically produced for optimizing the color reproduction of silk fabrics and a color image reproduction system has been developed for the digitization and archiving of the clothing fabric for the royal court. Color characterization models using both the "Qianlong Palette" color chart and the traditional color chart, and different mapping methods, are compared and the model with highest accuracy used in a self-programmed interface for automatically processing textile images in the future. Finally, the digital archive system has been validated using six garments of silk fabric relics. The color differences after the color image reproduction are all less than 3.00ΔE* ab , indicating acceptable color reproduction of the system. The images after color reproduction have also been evaluated subjectively by experts from the museum and the results are considered satisfactory. Our results show that the newly designed "Qianlong Palette" color chart exhibits superior performance over the conventional color chart in effectively predicting the color of the silk fabrics. The self-programmed graphical user interface for image color management can serve as a powerful tool to truly reproduce the color of various silk fabric relics in museums in the future and digitally archive those valuable cultural relics for different uses.

Dietary Antioxidant Indices in Relation to All-Cause and Cause-Specific Mortality Among Adults With Diabetes: A Prospective Cohort Study.

Background: The potential beneficial effect of individual antioxidants on mortality has been reported. However, the association of overall intakes of dietary antioxidants with all-cause and cause-specific mortality among adults with diabetes remained unclear. Methods: A total of 4,699 US adults with diabetes were enrolled in 2003-2014 in the National Health and Nutrition Examination Survey (NHANES) and followed for mortality until 31 December 2015. The Dietary Antioxidant Quality Score (DAQS) and the Dietary Antioxidant Index (DAI), which indicate the total antioxidant properties, were calculated based on the intakes of vitamins A, C, E, zinc, selenium, and magnesium. The Cox proportional hazards regression models were used to investigate the associations of the DAQS or the DAI with all-cause and cause-specific mortality. Results: A total of 913 deaths occurred during 27,735 person-years of follow-up, including 215 deaths due to cardiovascular disease (CVD) and 173 deaths due to cancer. The higher intakes of antioxidant vitamins A, E, magnesium, and selenium were associated with lower all-cause mortality. The adjusted hazard ratios (HRs) (95% CIs) comparing the highest DAQS (5-6) to the lowest DAQS (0-2) were 0.70 (0.53-0.92) for all-cause mortality, 0.56 (0.35-0.90) for CVD mortality, and 0.59 (0.33-1.04) for cancer mortality. Consistent inverse associations were found between the DAI and mortality. Conclusion: Higher intake of overall dietary antioxidants was associated with lower risk of death from all-cause and CVD in adults with diabetes. Future dietary intervention studies are needed to determine whether increasing overall antioxidant micronutrients intake could prevent premature death among adults with diabetes.

Physical Activity, Obesity, and Hypertension among Adults in a Rapidly Urbanised City.

BACKGROUND: Few studies have explored the relationship between the level of physical activity and the occurrence or prevalence of obesity and hypertension among people residing in urbanised areas. METHOD: A cross-sectional study involving a sample of 1,001 adults was conducted. Descriptive statistics were used to describe sociodemographic variables, physical activity levels, body mass index (BMI), and prevalence of hypertension. Logistic regression models were adopted to investigate the relationship between these factors. RESULTS: A total of 939 respondents who provided valid responses were included. Among them, 56.5% of the participants reported engaging in high levels of physical activity. However, 40.4% of the respondents were classified as overweight or obese, and 31.9% had diagnosed hypertension. After adjusting for sociodemographic factors, logistic regression analysis revealed that physical activity levels were negatively correlated with the prevalence of BMI (OR = 0.564, 95% CI: 0.352-0.905; OR = 0.583, 95% CI: 0.375-0.907) and hypertension (OR = 0.556, 95% CI: 0.348-0.888). CONCLUSIONS: Our study confirms recent evidence regarding the amount of physical activity that is associated with lower prevalence of obesity and hypertension in Pingshan District. Furthermore, different physical activities of various intensity levels had different effects on hypertension. Residents should be encouraged to engage in physical activities and maintain a healthy weight to improve their quality of life.

Built environment, physical activity, and obesity of adults in Pingshan District, Shenzhen City in Southern China.

BACKGROUND: The relation between neighbourhood built environment and obesity has been described as both nuanced and complex. AIM: The objective of this study was to examine the relationship between the built environment, physical activity, and obesity in a rapidly urbanised area of China. SUBJECTS AND METHODS: This is a cross-sectional study. Descriptive statistics were used to describe the socio-demographic variables, physical activity levels and BMI status. Multivariable logistic regression models were used to examine the association between neighbourhood environment, the likelihood of engaging in different types of physical activity, and BMI. RESULTS: A total of 842 respondents completed the questionnaires and were included (84.1% response rate). Among them, 56.4% reported meeting high physical activity levels, while 40.7% were overweight or obese. Multivariable regression analysis showed that better road conditions (ß = 0.122, t = 2.999, p = 0.003) and access to physical activity facilities (ß = 0.121, t = 3.193, p = 0.001) were significantly associated with higher levels of physical activity. Physical activity levels were inversely associated with the likelihood of being overweight (OR = 0.565, 95%CI: 0.3 4 9-0.917) or obese (OR = 0.614, 95%CI: 0.3 9 0-0.966). CONCLUSION: The built environment has an important impact on physical activity. However, the direct impact of leisure physical activity on BMI is not significant. This research provides a summary of recent evidence in Pingshan District on built environments that are most favourable for physical activity and obesity.

Neighbourhood built environment and leisure-time physical activity: A cross-sectional study in southern China.

This study conducted scientific evidence linking neighbourhood built environment to adults' leisure-time physical activity (LTPA) among adults in China. Data were obtained from a questionnaire survey conducted from April to July 2017 among 1002 adults aged 18-69 years old in Pingshan District, Shenzhen, China. Chinese Walkable Environment Scale for urban community residents and International Physical Activity Questionnaire were used to measure participants' neighbourhood built environment and leisure-time physical activity, which was categorised into leisure-time walking (LTW) and leisure-time moderate-to-vigorous physical activity (LTMVPA). A total of 986 participants (mean age = 40.7 years, 53.3% females) were included in this research. Descriptive statistics were used to describe the socio-demographic variables, LTW and LTMVPA by sex. Multivariable logistic regression models were used to examine the association between neighbourhood environment characteristics and the likelihood of engaging in active LTW and LTMVPA. Only 20.7% of participants engaged in active LTW and 17.8% active LTMVPA. Better road condition was associated with higher likelihood of active (at least 150 min/week) LTW and LTMVPA. High perceived esthetic was positively associated with LTW and LTMVPA. Active LTW was related to better perception of traffic condition as well. The improvement of the neighbourhood environment characteristics can promote active LTPA among adults living in Shenzhen, China. Our findings support the importance of considering population health effects in urban planning and development.

Non-contact method of thickness measurement for a transparent plate using a laser auto-focus scanning probe.

In this paper we propose a novel non-contact method of thickness measurement for a transparent plate using a laser auto-focus scanning (LAFS) probe. Through the analysis of the focus error signal (FES) from the actual specimen's upper and lower surface reflectances, a measurement model is introduced to find the best focus position on the corresponding surface of the transparent plate. Thus, the thickness of a specimen can be obtained. Herein, the LAFS probe measurement characteristics by auto-searching the FES method can be analyzed, which can then realize non-contact measurement and focus detection of micro-displacements. Therefore, we have successfully designed a low-cost, high-precision auto-focusing thickness measurement system with linear piezoelectric nano-positioning. To verify the proposed method, some transparent specimens were evaluated, and the thicknesses were rapidly and successfully measured. Experiments confirm the validity of the proposed system, and the results show that the method is effective for the thickness measurement of transparent plates.

Continual in-plane displacement measurement with temporal wavelet transform speckle pattern interferometry.

A heterodyne temporal speckle pattern interferometer that measures the in-plane displacement dynamically has been built. The object is displaced in its plane continuously and the frequency-modulated output signals with a carrier frequency are recorded by a CCD camera. The displacement information is extracted with wavelet transform technique. Preliminary experiments have been performed with such interferometer. The respective measurement results recovered from wavelet transform and Fourier transform are compared.