The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Marc P. Christensen - One of the best experts on this subject based on the ideXlab platform.
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effects of sampling on the phase transfer function of incoherent Imaging Systems
Optics Express, 2011Co-Authors: Vikrant R. Bhakta, Manjunath Somayaji, Marc P. ChristensenAbstract:With the advent of modern-day computational imagers, the phase of the optical transfer function may no longer be summarily ignored. This study discusses some important properties of the phase transfer function (PTF) of digital incoherent Imaging Systems and their implications on the performance and characterization of these Systems. The effects of aliasing and sub-pixel image shifts on the phase of the complex frequency response of these sampled Systems are described, including an examination of the specific case of moderate aliasing. Key properties of this function in aliased Imaging Systems are derived and their potential treatment to a range of diverse applications encompassing traditional and computational Imaging Systems is discussed.
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Phase transfer function of digital Imaging Systems
2011Co-Authors: Marc P. Christensen, Vikrant R. BhaktaAbstract:For the past several decades, optical engineering has relied heavily on Fourier analysis of linear Systems as a valuable aid in realizing numerous Imaging applications. Today, spatial frequency analysis via the optical transfer function (OTF) remains an integral tool for the design, characterization and testing of incoherent Imaging Systems. The magnitude of the complex OTF is known as the modulation transfer function (MTF) and its phase is given by the phase transfer function (PTF). The MTF represents the contrast reduction at each spatial frequency; whereas, the PTF represents the spatial shift of these frequencies. While the MTF has been used extensively to characterize Imaging Systems, the PTF has long been ignored because it was thought to have an insignificant presence and to be difficult to understand and measure. Through theoretical analysis and experimental demonstrations, this work addresses all of these issues and shows that the PTF is a valuable tool for modern-day digital Imaging Systems. The effects of optical aberrations on the PTF of an Imaging system in the absence of aliasing have been analyzed in detail. However, for the digital Imaging Systems, the effect of aliasing on the overall system behavior becomes an important consideration. To this end, the effects of aliasing on the PTF of the sampled Imaging system are described and its key properties are derived. The role of PTF as an essential metric in today's Imaging Systems necessitates practical PTF measurement techniques. Two, easy-to-implement, image-based methods for PTF measurement are described and experimentally validated. These measurement methods and the insights gained from the theoretical analysis are leveraged for several applications spanning diverse fields such as optical system characterization, computational Imaging, and image processing.
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Surpassing the Diffraction-limit of Digital Imaging Systems using Sinusoidal Illumination Patterns
Frontiers in Optics 2009 Laser Science XXV Fall 2009 OSA Optics & Photonics Technical Digest, 2009Co-Authors: Prasanna Rangarajan, Vikrant R. Bhakta, Marc P. ChristensenAbstract:This work presents experimental evidence on surpassing the diffraction limit of digital Imaging Systems using sinusoidal illumination patterns. Unique contributions of the work include aliasing-management and the notion of incoherent bandpass filtering using sinusoidal modulation.
Vikrant R. Bhakta - One of the best experts on this subject based on the ideXlab platform.
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effects of sampling on the phase transfer function of incoherent Imaging Systems
Optics Express, 2011Co-Authors: Vikrant R. Bhakta, Manjunath Somayaji, Marc P. ChristensenAbstract:With the advent of modern-day computational imagers, the phase of the optical transfer function may no longer be summarily ignored. This study discusses some important properties of the phase transfer function (PTF) of digital incoherent Imaging Systems and their implications on the performance and characterization of these Systems. The effects of aliasing and sub-pixel image shifts on the phase of the complex frequency response of these sampled Systems are described, including an examination of the specific case of moderate aliasing. Key properties of this function in aliased Imaging Systems are derived and their potential treatment to a range of diverse applications encompassing traditional and computational Imaging Systems is discussed.
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Phase transfer function of digital Imaging Systems
2011Co-Authors: Marc P. Christensen, Vikrant R. BhaktaAbstract:For the past several decades, optical engineering has relied heavily on Fourier analysis of linear Systems as a valuable aid in realizing numerous Imaging applications. Today, spatial frequency analysis via the optical transfer function (OTF) remains an integral tool for the design, characterization and testing of incoherent Imaging Systems. The magnitude of the complex OTF is known as the modulation transfer function (MTF) and its phase is given by the phase transfer function (PTF). The MTF represents the contrast reduction at each spatial frequency; whereas, the PTF represents the spatial shift of these frequencies. While the MTF has been used extensively to characterize Imaging Systems, the PTF has long been ignored because it was thought to have an insignificant presence and to be difficult to understand and measure. Through theoretical analysis and experimental demonstrations, this work addresses all of these issues and shows that the PTF is a valuable tool for modern-day digital Imaging Systems. The effects of optical aberrations on the PTF of an Imaging system in the absence of aliasing have been analyzed in detail. However, for the digital Imaging Systems, the effect of aliasing on the overall system behavior becomes an important consideration. To this end, the effects of aliasing on the PTF of the sampled Imaging system are described and its key properties are derived. The role of PTF as an essential metric in today's Imaging Systems necessitates practical PTF measurement techniques. Two, easy-to-implement, image-based methods for PTF measurement are described and experimentally validated. These measurement methods and the insights gained from the theoretical analysis are leveraged for several applications spanning diverse fields such as optical system characterization, computational Imaging, and image processing.
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Surpassing the Diffraction-limit of Digital Imaging Systems using Sinusoidal Illumination Patterns
Frontiers in Optics 2009 Laser Science XXV Fall 2009 OSA Optics & Photonics Technical Digest, 2009Co-Authors: Prasanna Rangarajan, Vikrant R. Bhakta, Marc P. ChristensenAbstract:This work presents experimental evidence on surpassing the diffraction limit of digital Imaging Systems using sinusoidal illumination patterns. Unique contributions of the work include aliasing-management and the notion of incoherent bandpass filtering using sinusoidal modulation.
Carl E Ravin - One of the best experts on this subject based on the ideXlab platform.
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detector or system extending the concept of detective quantum efficiency to characterize the performance of digital radiographic Imaging Systems
Radiology, 2008Co-Authors: Ehsan Samei, Nicole T Ranger, Alistair Mackenzie, Ian D Honey, James T Dobbins, Carl E RavinAbstract:Purpose: To develop an experimental method for measuring the effective detective quantum efficiency (eDQE) of digital radiographic Imaging Systems and evaluate its use in select Imaging Systems. Materials and Methods: A geometric phantom emulating the attenuation and scatter properties of the adult human thorax was employed to assess eight Imaging Systems in a total of nine configurations. The noise power spectrum (NPS) was derived from images of the phantom acquired at three exposure levels spanning the operating range of the system. The modulation transfer function (MTF) was measured by using an edge device positioned at the anterior surface of the phantom. Scatter measurements were made by using a beam-stop technique. All measurements, including those of phantom attenuation and estimates of x-ray flux, were used to compute the eDQE. Results: The MTF results showed notable degradation owing to focal spot blur. Scatter fractions ranged between 11% and 56%, depending on the system. The eDQE(0) results ran...
Aydogan Ozcan - One of the best experts on this subject based on the ideXlab platform.
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Deep learning-based super-resolution in coherent Imaging Systems
Scientific Reports, 2019Co-Authors: Kevin De Haan, Yair Rivenson, Yibo Zhang, Xin Zeng, Aydogan OzcanAbstract:We present a deep learning framework based on a generative adversarial network (GAN) to perform super-resolution in coherent Imaging Systems. We demonstrate that this framework can enhance the resolution of both pixel size-limited and diffraction-limited coherent Imaging Systems. The capabilities of this approach are experimentally validated by super-resolving complex-valued images acquired using a lensfree on-chip holographic microscope, the resolution of which was pixel size-limited. Using the same GAN-based approach, we also improved the resolution of a lens-based holographic Imaging system that was limited in resolution by the numerical aperture of its objective lens. This deep learning-based super-resolution framework can be broadly applied to enhance the space-bandwidth product of coherent Imaging Systems using image data and convolutional neural networks, and provides a rapid, non-iterative method for solving inverse image reconstruction or enhancement problems in optics.
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Deep learning-based super-resolution in coherent Imaging Systems
arXiv: Computer Vision and Pattern Recognition, 2018Co-Authors: Kevin De Haan, Yair Rivenson, Yibo Zhang, Xin Zeng, Aydogan OzcanAbstract:We present a deep learning framework based on a generative adversarial network (GAN) to perform super-resolution in coherent Imaging Systems. We demonstrate that this framework can enhance the resolution of both pixel size-limited and diffraction-limited coherent Imaging Systems. We experimentally validated the capabilities of this deep learning-based coherent Imaging approach by super-resolving complex images acquired using a lensfree on-chip holographic microscope, the resolution of which was pixel size-limited. Using the same GAN-based approach, we also improved the resolution of a lens-based holographic Imaging system that was limited in resolution by the numerical aperture of its objective lens. This deep learning-based super-resolution framework can be broadly applied to enhance the space-bandwidth product of coherent Imaging Systems using image data and convolutional neural networks, and provides a rapid, non-iterative method for solving inverse image reconstruction or enhancement problems in optics.
Ehsan Samei - One of the best experts on this subject based on the ideXlab platform.
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detector or system extending the concept of detective quantum efficiency to characterize the performance of digital radiographic Imaging Systems
Radiology, 2008Co-Authors: Ehsan Samei, Nicole T Ranger, Alistair Mackenzie, Ian D Honey, James T Dobbins, Carl E RavinAbstract:Purpose: To develop an experimental method for measuring the effective detective quantum efficiency (eDQE) of digital radiographic Imaging Systems and evaluate its use in select Imaging Systems. Materials and Methods: A geometric phantom emulating the attenuation and scatter properties of the adult human thorax was employed to assess eight Imaging Systems in a total of nine configurations. The noise power spectrum (NPS) was derived from images of the phantom acquired at three exposure levels spanning the operating range of the system. The modulation transfer function (MTF) was measured by using an edge device positioned at the anterior surface of the phantom. Scatter measurements were made by using a beam-stop technique. All measurements, including those of phantom attenuation and estimates of x-ray flux, were used to compute the eDQE. Results: The MTF results showed notable degradation owing to focal spot blur. Scatter fractions ranged between 11% and 56%, depending on the system. The eDQE(0) results ran...
