During the last years, Time-of-Flight sensors achieved a significant impact onto research fields in machine vision. In comparison to stereo vision system and laser range scanners they combine the advantages of active ...
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ISBN:
(纸本)9781479921805
During the last years, Time-of-Flight sensors achieved a significant impact onto research fields in machine vision. In comparison to stereo vision system and laser range scanners they combine the advantages of active sensors providing accurate distance measurements and camera-based systems recording a 2D matrix at a high frame rate. Moreover low cost 3D imaging has the potential to open a wide field of additional applications and solutions in markets like consumer electronics, multimedia, digital photography, robotics and medical technologies. This paper focuses on the classification task of typical industrial products in the close-up range. A new approach due to the use of the photonic-mixer-device (PMD) sensor technology is presented which achieves a much simpler real-time classification. Experimental results show that the proposed approach is well suited for machine vision applications.
During the last years, Time-of-Flight sensors achieved a significant impact onto research fields in machine vision. In comparison to other common 3D sensing devices they combine the advantages of active sensors provid...
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ISBN:
(纸本)9781457717710
During the last years, Time-of-Flight sensors achieved a significant impact onto research fields in machine vision. In comparison to other common 3D sensing devices they combine the advantages of active sensors providing accurate distance measurements and camera-based systems recording a 2D matrix at a high frame rate. This paper focuses on the currently implemented 4-phase-shift algorithm to calculate the range image in this type of sensors. A new approach is presented which increases the range calculation time by a factor of four. Experimental results show that the proposed algorithm is well suited for real-time processing of the range images of TOF cameras.
In phaseshifting interferometers, spatial non-uniformity of the phase modulation often happens in such cases where an aspherical (or spherical) mirror is compared to the corresponding aspherical standard surface whic...
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ISBN:
(纸本)0819430382
In phaseshifting interferometers, spatial non-uniformity of the phase modulation often happens in such cases where an aspherical (or spherical) mirror is compared to the corresponding aspherical standard surface which is translated along the optical axis by piezo electric transducer to introduce phase modulation. The amount of phaseshift is then different across the observing aperture depending on the gradient of the testing surface. The nonlinear sensitivity of the phase modulator causes a significant errors in measured phase when there is a spatial nonuniformity in phaseshift. Many phase measuring algorithms reported to date cannot compensate for the spatial nonuniformity if there is a nonlinear phaseshift. It is shown that if we add a new symmetry to the sampling functions of the phase measuring algorithm we can suppress the phase errors caused by the spatial non-uniformity of the phaseshift. The new algorithms need at least one more image frame to acquire the symmetry. The lowest-order algorithm compensating for quadratic spatially nonuniform phase modulation consists of six frames.
Registered depth and intensity data at a high frame rate, a compact design, low weight and a reduced power consumption have motivated the increasing usage of lock-in time-of-flight cameras in research areas such as co...
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ISBN:
(纸本)9781467346214
Registered depth and intensity data at a high frame rate, a compact design, low weight and a reduced power consumption have motivated the increasing usage of lock-in time-of-flight cameras in research areas such as computer graphics, machine vision and robotics. State of the art is to use continuous wave modulation with square waves for TOF cameras. Square waves can be easily generated digitally with a high accuracy and stability using programmable logic devices. In this paper a modulation method based on sine waves is proposed, which significantly reduces the depth distortion offset (wiggling effect) of lock-in TOF cameras.
In a phase-shifting interferometer, spatial non-uniformity of the phase modulation happens in such a case where an aspherical mirror is compared to the corresponding aspherical standard surface which is translated alo...
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ISBN:
(纸本)0819432245
In a phase-shifting interferometer, spatial non-uniformity of the phase modulation happens in such a case where an aspherical mirror is compared to the corresponding aspherical standard surface which is translated along the optical axis by a piezo electric transducer. The amount of phaseshift is different from position to position across the observing aperture depending on the direction cosine of the testing surface. In another case, when the reference optical flat is translated by two or more piezo-electric transducers, we cannot ensure that the reference surface moves strictly parallel to the optical axis. When these transducers have different sensitivities, the phase modulation is no longer spatially uniform and varies across the observing aperture. Many phase measuring algorithms reported to date cannot compensate for the spatial nonuniformity if there is a nonlinear phaseshift. It is shown that even-order nonlinear sensitivity of the phase modulator causes a significant errors in measured phase when there is a spatial nonuniformity in the phaseshift. However, if we add a new symmetry to the sampling functions of the phase measuring algorithm we can suppress the lowest order of these errors. The new algorithms need at least one more image frame to acquire the symmetry. The lowest-order algorithm compensating for quadratic spatially non-uniform phase modulation consists of six frames. Since the new algorithm acquires a new symmetry, it usually suffers from a larger random noise than the conventional algorithms. The random noise can be decreased if we added more sampling frames to the algorithm. The sampling amplitudes are determined by a Lagrangian method. The resultant algorithms show that the random noise decreases inversely proportional to the square-root of the numberer of samples.
Single-pixel imaging, with the advantages of a wide spectrum, beyond-visual-field imaging, and robustness to light scattering, has attracted increasing attention in recent years. Fourier single-pixel imaging (FSI) can...
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Single-pixel imaging, with the advantages of a wide spectrum, beyond-visual-field imaging, and robustness to light scattering, has attracted increasing attention in recent years. Fourier single-pixel imaging (FSI) can reconstruct sharp images under sub-Nyquist sampling. However, the conventional FSI has difficulty balancing imaging quality and efficiency. To overcome this issue, we proposed a novel approach called complementary Fourier single-pixel imaging (CFSI) to reduce the number of measurements while retaining its robustness. The complementary nature of Fourier patterns based on a four-step phase-shift algorithm is combined with the complementary nature of a digital micromirror device. CFSI only requires two phase-shifted patterns to obtain one Fourier spectral value. Four light intensity values are obtained by loading the two patterns, and the spectral value is calculated through differential measurement, which has good robustness to noise. The proposed method is verified by simulations and experiments compared with FSI based on two-, three-, and four-step phaseshiftalgorithms. CFSI performed better than the other methods under the condition that the best imaging quality of CFSI is not reached. The reported technique provides an alternative approach to realize real-time and high-quality imaging.
In machine vision applications, Time-of-Flight (TOF) sensors like the Photonic Mixer Devices (PMD) became considerable alternatives to common 3D sensing devices. Because of the enormous progress in TOF-vision systems,...
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ISBN:
(纸本)9781479961153
In machine vision applications, Time-of-Flight (TOF) sensors like the Photonic Mixer Devices (PMD) became considerable alternatives to common 3D sensing devices. Because of the enormous progress in TOF-vision systems, nowadays 3D matrix cameras can be used for many applications such as robotic, automotive, industrial, medical and multimedia applications. This paper focuses on the range data resolution for machine vision applications in the close-up range. For many applications the 3D information of objects are required in Cartesian coordinates. However TOF cameras normally deliver polar coordinates. In this paper different polar to Cartesian coordinate system conversion methods and their influence of the range resolution in the close-up range of TOF cameras are investigated.
Registered depth and intensity data at a high frame rate, a compact design, low weight and a reduced power consumption have motivated the increasing usage of lock-in time-of-flight cameras in research areas such as co...
详细信息
ISBN:
(纸本)9781467346214
Registered depth and intensity data at a high frame rate, a compact design, low weight and a reduced power consumption have motivated the increasing usage of lock-in time-of-flight cameras in research areas such as computer graphics, machine vision and robotics. State of the art is to use continuous wave modulation with square waves for TOF cameras. Square waves can be easily generated digitally with a high accuracy and stability using programmable logic devices. In this paper a modulation method based on sine waves is proposed, which significantly reduces the depth distortion offset (wiggling effect) of lock-in TOF cameras.
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