In Fourier transform profilometry （FTP）, we must restrain spectrum overlapping caused by the nonlinearity of the charge coupled device （CCD） and increase the measurement accuracy of the object shape. Firstly, the ...In Fourier transform profilometry （FTP）, we must restrain spectrum overlapping caused by the nonlinearity of the charge coupled device （CCD） and increase the measurement accuracy of the object shape. Firstly, the causes of producing higher-order spectrum components and inducing spectrum overlapping are analysed theoretically, and a simple physical ex- planation and analytical deduction are given. Secondly, aiming to suppress spectrum overlapping and improve measurement accuracy, the influence of spatial carrier frequency of projection grating on them is analysed. A method of increasing the spatial carrier frequency of projection grating to restrain or reduce the spectrum overlapping significantly is proposed. We then analyze the mechanism of how the spectrum overlapping is reduced. Finally, the simulation results and experimental measurements verify the correction of the proposed theory and method.展开更多
A method of 2-D Fourier transform used in 3-D surface profilometry is proposed,analyzed and compared with 1-D Fourier transform method in theory and practical measuring result.It was proved that the 2-D Fourier transf...A method of 2-D Fourier transform used in 3-D surface profilometry is proposed,analyzed and compared with 1-D Fourier transform method in theory and practical measuring result.It was proved that the 2-D Fourier transform method has more advantages over 1-D Fourier transform method in biggest crook-rate limits,accuracy and sensitivity of measuring.Study on measuring object surface details with large crook-rate changing accurately used new higher-power index low-pass filter of spatial frequency domain.A new method of automatic produced reference grating image and error-correcting is proposed.One undeform row of deform grating image is used to extend a complete reference grating image,and some error-correcting method is used to process the result to get accurate surface shape and the deflection of reference surface normal line deviated from the axle of camera.By this new method,one deform rectangle grating image is only used to get the 3-D shape accurately.展开更多
In this paper, we proposed a new concept: depth of drowsiness, which can more precisely describe the drowsiness than existing binary description. A set of effective markers for drowsiness: normalized band norm was suc...In this paper, we proposed a new concept: depth of drowsiness, which can more precisely describe the drowsiness than existing binary description. A set of effective markers for drowsiness: normalized band norm was successfully developed. These markers are invariant from voltage amplitude of brain waves, eliminating the need for calibrating the voltage output of the brain-computer interface devices. A new polling algorithm was designed and implemented for computing the depth of drowsiness. The time cost of data acquisition and processing for each estimate is about one second, which is well suited for real-time applications. Test results with a portable brain-computer interface device show that the depth of drowsiness computed by the method in this paper is generally invariant from ages of test subjects and sensor channels (P3 and C4). The comparison between experiment and computing results indicate that the new method is noticeably better than one of the recent methods in terms of accuracy for predicting the drowsiness.展开更多
Fringe projection technique is a non-contact, full field 3-D shape measurement method. The object depth information is recorded in one or several deformed fringe patterns. The phase-shifting algorithm or the Fourier t...Fringe projection technique is a non-contact, full field 3-D shape measurement method. The object depth information is recorded in one or several deformed fringe patterns. The phase-shifting algorithm or the Fourier transform method can be used to extract the wrapped phase data. A phase unwrapping process is then applied to retrieve a continuous phase distribution, which represents the surface profile of the test object. In this paper, a quality-guided phase unwrapping approach is incorporated and two novel phase quality evaluation methods are proposed to facilitate the phase unwrapping process.展开更多
In order to study the strength of the composite material plate problems, need to adopt a nondestructive testing method to obtain the specimen surface under the effect of high-speed impact regularity of shape. The proj...In order to study the strength of the composite material plate problems, need to adopt a nondestructive testing method to obtain the specimen surface under the effect of high-speed impact regularity of shape. The projection profilometry was used to measure the surface profile or the full field deformation. Furtherly, by using the Fourier transform algorithm, there is only one frame of captured image</span><span style="font-family:Verdana;"> which</span><span style="font-family:Verdana;"> is needed in the measurement, so that it can be introduced into the high speed impaction procedure measurement. An experimental system, which was contained with an impact setup and the projection profilometry measurement part, was constructed for the impaction action characteristic research. The metallic impact object can be launched by a gas gun or a spin fan, respectively. The detected object </span><span style="font-family:Verdana;">is</span><span style="font-family:Verdana;"> manufactured by composite materials. In order to increase the surface deformation measurement accuracy, the calibration method and the error was discussed with different calibration specimen. And then, the proposed profilometry measurement method is proved by the gas gun and spin fan projectile test. The surface deformation of the manufactured composite plates and fan case are measured in the impaction procedure. So that the impact action details can be described much more clearly than the traditional video monitoring method.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61173122, 60970098, 60803024, 90715043, and 61144006)the Postdoctoral Startup Foundation of Central South University, China (Grant No. 1332/74341016030)
文摘In Fourier transform profilometry （FTP）, we must restrain spectrum overlapping caused by the nonlinearity of the charge coupled device （CCD） and increase the measurement accuracy of the object shape. Firstly, the causes of producing higher-order spectrum components and inducing spectrum overlapping are analysed theoretically, and a simple physical ex- planation and analytical deduction are given. Secondly, aiming to suppress spectrum overlapping and improve measurement accuracy, the influence of spatial carrier frequency of projection grating on them is analysed. A method of increasing the spatial carrier frequency of projection grating to restrain or reduce the spectrum overlapping significantly is proposed. We then analyze the mechanism of how the spectrum overlapping is reduced. Finally, the simulation results and experimental measurements verify the correction of the proposed theory and method.
文摘A method of 2-D Fourier transform used in 3-D surface profilometry is proposed,analyzed and compared with 1-D Fourier transform method in theory and practical measuring result.It was proved that the 2-D Fourier transform method has more advantages over 1-D Fourier transform method in biggest crook-rate limits,accuracy and sensitivity of measuring.Study on measuring object surface details with large crook-rate changing accurately used new higher-power index low-pass filter of spatial frequency domain.A new method of automatic produced reference grating image and error-correcting is proposed.One undeform row of deform grating image is used to extend a complete reference grating image,and some error-correcting method is used to process the result to get accurate surface shape and the deflection of reference surface normal line deviated from the axle of camera.By this new method,one deform rectangle grating image is only used to get the 3-D shape accurately.
文摘In this paper, we proposed a new concept: depth of drowsiness, which can more precisely describe the drowsiness than existing binary description. A set of effective markers for drowsiness: normalized band norm was successfully developed. These markers are invariant from voltage amplitude of brain waves, eliminating the need for calibrating the voltage output of the brain-computer interface devices. A new polling algorithm was designed and implemented for computing the depth of drowsiness. The time cost of data acquisition and processing for each estimate is about one second, which is well suited for real-time applications. Test results with a portable brain-computer interface device show that the depth of drowsiness computed by the method in this paper is generally invariant from ages of test subjects and sensor channels (P3 and C4). The comparison between experiment and computing results indicate that the new method is noticeably better than one of the recent methods in terms of accuracy for predicting the drowsiness.
文摘Fringe projection technique is a non-contact, full field 3-D shape measurement method. The object depth information is recorded in one or several deformed fringe patterns. The phase-shifting algorithm or the Fourier transform method can be used to extract the wrapped phase data. A phase unwrapping process is then applied to retrieve a continuous phase distribution, which represents the surface profile of the test object. In this paper, a quality-guided phase unwrapping approach is incorporated and two novel phase quality evaluation methods are proposed to facilitate the phase unwrapping process.
文摘In order to study the strength of the composite material plate problems, need to adopt a nondestructive testing method to obtain the specimen surface under the effect of high-speed impact regularity of shape. The projection profilometry was used to measure the surface profile or the full field deformation. Furtherly, by using the Fourier transform algorithm, there is only one frame of captured image</span><span style="font-family:Verdana;"> which</span><span style="font-family:Verdana;"> is needed in the measurement, so that it can be introduced into the high speed impaction procedure measurement. An experimental system, which was contained with an impact setup and the projection profilometry measurement part, was constructed for the impaction action characteristic research. The metallic impact object can be launched by a gas gun or a spin fan, respectively. The detected object </span><span style="font-family:Verdana;">is</span><span style="font-family:Verdana;"> manufactured by composite materials. In order to increase the surface deformation measurement accuracy, the calibration method and the error was discussed with different calibration specimen. And then, the proposed profilometry measurement method is proved by the gas gun and spin fan projectile test. The surface deformation of the manufactured composite plates and fan case are measured in the impaction procedure. So that the impact action details can be described much more clearly than the traditional video monitoring method.
