A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Review of single-shot 3D shape measurement by phase calculation-based fringe projection techniques

A method for whole-field noncontact measurement of displacement, velocity, and acceleration of a vibrating object based on image-plane digital holography is presented. A series of digital holograms of a vibrating object are captured by use of a high-speed CCD camera. The result of the reconstruction is a three-dimensional complex-valued matrix with noise. We apply Fourier analysis and windowed Fourier analysis in both the spatial and the temporal domains to extract the displacement, the velocity, and the acceleration. The instantaneous displacement is obtained by temporal unwrapping of the filtered phase map, whereas the velocity and acceleration are evaluated by Fourier analysis and by windowed Fourier analysis along the time axis. The combination of digital holography and temporal Fourier analyses allows for evaluation of the vibration, without a phase ambiguity problem, and smooth spatial distribution of instantaneous displacement, velocity, and acceleration of each instant are obtained. The comparison of Fourier analysis and windowed Fourier analysis in velocity and acceleration measurements is also presented.

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Vibration measurement by temporal Fourier analyses of a digital hologram sequence.

Phase-retrieval techniques in fringe-projection profilometry

A laser Doppler vibrometer with single photodetector is introduced to measure the vibration on multiple points of target simultaneously. A 2 x 5 beam array with various frequency shifts is generated by three acousto-optic devices, illuminating different points on a vibrating object. The reflected beams interfere with a reference beam on a high-speed photodetector, and the signal is amplified and digitized with a rate of 500 megasamples/s. To extract vibration information of different points, the carrier frequencies of each beam are elaborately designed so that they can be separated from cross-talk regions in the spectrum. The experimental results are compared with that from a commercial single-point vibrometer, and the comparison shows that it is possible to do a precise measurement on multiple points simultaneously using a single photodetector.

/pdf/spatially-encoded-multibeam-laser-doppler-vibrometry-using-a-3rudhe7ojc.pdf

Spatially encoded multibeam laser Doppler vibrometry using a single photodetector

Animated shape transformations should be an intrinsic part of visual cyberworlds. However, quite often only limited animation of the polygon-based shapes can be found there, specifically when using the virtual reality modeling language (VRML) and its successor extensible 3D (X3D). This greatly limits the expressive power of visual cyberworlds and has motivated our research in this direction. In this paper, we present function-based extensions of VRML and X3D, which allow for time-dependent shape modeling on the web. Our shape modeling approach is based on the concurrent use of implicit, explicit and parametric functions defining geometry, appearance and their transformations through time. The functions are typed straight in VRML/X3D code as individual formulas and as function scripts. We have also developed a web enabled interactive software tool for modeling function-based VRML/X3D objects.

Function-defined shape metamorphoses in visual cyberworlds

Function-based shape modelling extension of the Virtual Reality Modelling Language

Age is an important factor affecting the development of creative thinking, and digital educational games have great potential in the training of creative thinking for preschool children. However, the effect of digital educational games on the creative thinking of preschool children of different ages is still unclear. In this study, a digital educational game “Thinking Paradise” was specially developed as a training method for preschool children's creative thinking. Including 11 different types of mini-games from 5 different creative thinking forms to train preschool children's creative thinking. 102 children aged 3–6 were divided into 3 groups according to their age, G1 (3–4 years old, N = 34), G2 (4–5 years old, N = 34), G3 (5–6 years old, N = 34). All children were asked to complete the training in the classroom, using a pre-post test design to examine the effects of this digital educational game training on creative thinking. The digital Torrance test is used for pre-test and post-test measurement and is evaluated by five indicators: fluency score, detail score, original score, anti-block score, and title score. The results showed that all indicators of the children after training were significantly improved, and the experiment proved that this digital educational game training could effectively improve the creative thinking of preschool children. Training had different effects on preschool children of different ages, and there were significant differences in the improvement of fluency scores, title scores, and anti-block scores in different age groups. The fluency score of the 3-4-year-old group was significantly improved, and the total score improvement score was close to the maximum value. At the same time, the training significantly improved the title score and anti-block score of the 5-6-year-old children. This study expands on existing knowledge about creative thinking in preschool children, highlighting the need to focus on age differences when using digital educational games to train preschool children's creative thinking. This study can also provide valid evidence for the development of digital educational games in preschool children. 

The influence of digital educational games on preschool Children's creative thinking

A 3D windowed Fourier transform is proposed for fringe sequence analysis, which processes the joint spatial and temporal information of the fringe sequence simultaneously. The 2D windowed Fourier transform in the spatial domain and the 1D windowed Fourier transform in the temporal domain are two special cases of the proposed method. The principles of windowed Fourier filtering and windowed Fourier ridges are developed. Experimental verification shows encouraging results despite a longer processing time.

/pdf/generalized-three-dimensional-windowed-fourier-transform-for-4macnm7rp8.pdf

Generalized three-dimensional windowed Fourier transform for fringe analysis

In this paper, we introduce a function-based extension of Virtual Reality Modeling Language. In this extension, analytical functions are used for defining geometry and appearance of 3D shapes, as well as transformations of them. By analytical functions we understand definitions with parametric, implicit and explicit formulas. In our hybrid function-based web visualization model, these very different analytical representations can be used concurrently for defining geometry and appearance of the shapes. We also illustrate how the proposed extension can be further enriched with any proprietary function-based models. The presented VRML plug-in is very useful for building both static and interactive virtual environments on the Web. This is illustrated with the implementation of the Virtual Collaborative Shape Modeling Laboratory.

Qi Liu

Papers

Function-defined shape metamorphoses in visual cyberworlds

Function-based shape modelling extension of the Virtual Reality Modelling Language

The influence of digital educational games on preschool Children's creative thinking

Generalized three-dimensional windowed Fourier transform for fringe analysis

Function-based representation of complex geometry and appearance