Optical transfer function

About: Optical transfer function is a research topic. Over the lifetime, 6079 publications have been published within this topic receiving 90526 citations. The topic is also known as: modulation transfer function & OTF.

Full breast digital mammography with an amorphous silicon‐based flat panel detector: Physical characteristics of a clinical prototype

Abstract: The physical characteristics of a clinical prototype amorphous silicon-based flat panel imager for full-breast digital mammography have been investigated. The imager employs a thin thalliumdoped CsI scintillator on an amorphous silicon matrix of detector elements with a pixel pitch of 100 μm. Objective criteria such as modulation transfer function(MTF),noise power spectrum, detective quantum efficiency (DQE), and noise equivalent quanta were employed for this evaluation. The presampling MTF was found to be 0.73, 0.42, and 0.28 at 2, 4, and 5 cycles/mm, respectively. The measured DQE of the current prototype utilizing a 28 kVp, Mo–Mo spectrum beam hardened with 4.5 cm Lucite is ∼55% at close to zero spatial frequency at an exposure of 32.8 mR, and decreases to ∼40% at a low exposure of 1.3 mR. Detector element nonuniformity and electronic gain variations were not significant after appropriate calibration and software corrections. The response of the imager was linear and did not exhibit signal saturation under tested exposure conditions.

Imaging antenna arrays

Abstract: Many millimeter and far-infrared imaging systems are limited in sensitivity and speed because they depend on a single scanned element. Because of recent advances in planar detectors such as Schottky diodes, superconducting tunnel junctions, and micro-boiometers, an attractive approach to this problem is a planar antenna array with integrated detectors. A planar line antenna array and optical system for imaging has been developed by the authors. The significant advances are a "reverse-microscope" optical configuration and a modified bow-tie antenna design. In the "reverse-microscope" configuration, a lens is attached to the bottom of the substrate containing the antennas. Imaging is done through the substrate. This configuration eliminates the troublesome effects of substrate surface waves. The substrate lens has only a single refracting surface, making possible a virtually aplanatic system, with little spherical aberration or coma. The array is characterized by an optical transfer function that is easily measured. An array with 19 dB crosstalk levels between adjacent antennas has been tested and it was found that the array captured 50 percent of the available power. This imaging system was diffraction limited.

Medical Imaging Signals and Systems

Abstract: Preface Part I: Basic Imaging Principles Overview. Chapter 1Introduction. History of Medical Imaging. Physical Signals. Imaging Modalities. Projection Radiography. Computed Tomography. Nuclear Medicine. Ultrasound Imaging. Magnetic Resonance Imaging. Summary and Key Concepts. Chapter 2: Signals and Systems.Introduction. Signals. Point Impulse. Line Impulse. Comb and Sampling Functions. Rect and Sinc Functions. Exponential and Sinusoidal Signals. Separable Signals. Periodic Signals. Systems. Linear Systems. Impulse Response. Shift Invariance. Connections of LSI Systems. Separable Systems. Stable Systems. The Fourier Transform. Properties of the Fourier Transform. Linearity. Translation. Conjugation and Conjugate Symmetry. Scaling. Rotation. Convolution. Product. Separable Product. Parseval's Theorem. Separability. Transfer Function. Circular Symmetry and the Hankel Transform. Sampling. Sampling Signal Model. Nyquist Sampling Theorem. Anti-aliasing Filters. Summary and Key Concepts. Chapter 3: Image Quality.Introduction. Contrast. Modulation. Modulation Transfer Function. Local Contrast. Resolution. Line Spread Function. Full Width at Half Maximum. Resolution and Modulation Transfer Function. Subsystem Cascade. Resolution Tool. Temporal and Spectral Resolution. Noise. Random Variables. Continuous Random Variables. Discrete Random Variables.Independent Random Variables. Signal-to-Noise Ratio. Amplitude SNR. Power SNR. Differential SNR. Nonrandom Effects. Artifacts. Distortion. Accuracy. Quantitative Accuracy. Diagnostic Accuracy. Summary and Key Concepts. Part II: Radiographic Imaging.Overview. Chapter 4: Physics of Radiography.Introduction. Ionization. Atomic Structure. Electron Binding Energy. Ionization and Excitation. Forms of Ionizing Radiation. Particulate Radiation. Electromagnetic Radiation. Nature and Properties of Ionizing Radiation. Primary Energetic Electron Interactions. Primary Electromagnetic Radiation Interactions. Attenuation of Electromagnetic Radiation. Measures of X-ray Beam Strength. Narrow Beam, Monoenergetic Photons. Narrow Beam, Polyenergetic Photons. Broad Beam Case. Radiation Dosimetry. Exposure. Dose and Kerma. Linear Energy Transfer. The f --factor. Dose Equivalent. Effective Dose. Summary and Key Concepts. Chapter 5: Projection Radiography.Introduction. Instrumentation. X-ray Tubes. Filtration and Restriction. Compensation Filters and Contrast Agents. Grids, Airgaps, and Scanning Slits. Film-Screen Detectors. X-ray Image Intensifiers. Image Formation. Basic Imaging Equation. Geometric Effects. Blurring Effects. Film Characteristics. Noise and Scattering. Signal-to-Noise Ratio. Quantum Efficiency and Detective Quantum Efficiency. Compton Scattering. Summary and Key Concepts. Chapter 6: Computed Tomography.Introduction. CT Instrumentation. CT Generations. X-ray Source and Collimation. CT Detectors. Gantry, Slip Ring, and Patient Table. Image Formation. Line Integrals. CT Numbers. Parallel-Ray Reconstruction. Fan-Beam Reconstruction. Helical CT Reconstruction. Cone Beam CT. Image Quality in CT. Resolution. Noise. Artifacts. Summary and Key Concepts. Part III: Nuclear Medicine Imaging.Overview. Chapter 7: The Physics of Nuclear Medicine.Introduction. Nomenclature. Radioactive Decay. Mass Defect and Binding Energy. Line of Stability. Radioactivity. Radioactive Decay Law. Modes of Decay. Positron Decay and Electron Capture. Isomeric Transition. Statistics of Decay. Radiotracers. Summary and Key Concepts. Chapter 8: Planar Scintigraphy.Introduction. Instrumentation. Collimators. Scintillation Crystal. Photomultiplier Tubes. Positioning Logic. Pulse Height Analyzer. Gating Circuit. Image Capture. Image Formation. Event Position Estimation. Acquisition Modes. Anger Camera Imaging Equation. Image Quality. Resolution. Sensitivity. Uniformity. Energy Resolution. Noise. Factors Affecting Count Rate. Summary and Key Concepts. Chapter 9: Emission Computed Tomography.Instrumentation. SPECT Instrumentation. PET Instrumentation. Image Formation. SPECT Image Formation. PET Image Formation. Iterative Reconstruction. Image Quality in SPECT and PET. Spatial Resolution. Attenuation and Scatter. Random Coincidences. Contrast. Noise and Signal-to-Noise. Summary and Key Concepts. Part IV: Ultrasound Imaging.Overview. Chapter 10: The Physics of Ultrasound. Introduction. The Wave Equation. Three-Dimensional Acoustic Waves. Plane Waves. Spherical Waves. Wave Propagation. Acoustic Energy and Intensity. Reflection and Refraction at Plane Interfaces. Transmission and Reflection Coefficients at Plane Interfaces. Attenuation. Scattering. Doppler Effect. Beam Pattern Formation and Focusing. Simple Field Pattern Model. Diffraction Formulation. Focusing. Summary and Key Concepts. Chapter 11: Ultrasound Imaging Systems.Introduction. Instrumentation. Ultrasound Transducer. Ultrasound Probes. Pulse-Echo Imaging. The Pulse-Echo Equation. Transducer Motion. Ultrasound Imaging Modes. A-Mode Scan. M-Mode Scan. B-Mode Scan. Steering and Focusing. Transmit Steering and Focusing. Beamforming and Dynamic Focusing. Three-Dimensional Ultrasound Imaging. Summary and Key Concepts. Part V: Magnetic Resonance Imaging.Overview. Chapter 12: Physics of Magnetic Resonance.Introduction. Microscopic Magnetization. Macroscopic Magnetization. Precession and Larmor Frequency. Transverse and Longitudinal Magnetization. NMR Signals. Rotating Frame. RF Excitation. Relaxation. The Bloch Equations. Spin Echoes. Contrast Mechanisms. Summary and Key Concepts. Chapter 13: Magnetic Resonance Imaging.Instrumentation. System Components. Magnet. Gradient Coils. Radio-Frequency Coils. Scanning Console and Computer. MRI Data Acquisition. Encoding Spatial Position. Slice Selection. Frequency Encoding. Polar Scanning. Gradient Echoes. Phase Encoding. Spin Echoes. Pulse Repetition Interval. Realistic Pulse Sequences. Image Reconstruction. Rectilinear Data. Polar Data. Imaging Equations. Image Quality. Sampling. Resolution. Noise. Signal-to-Noise Ratio. Artifacts. Summary and Key Concepts. Index.

Synthetic aperture fourier holographic optical microscopy.

Abstract: We report a new synthetic aperture optical microscopy in which high-resolution, wide-field amplitude and phase images are synthesized from a set of Fourier holograms. Each hologram records a region of the complex two-dimensional spatial frequency spectrum of an object, determined by the illumination field's spatial and spectral properties and the collection angle and solid angle. We demonstrate synthetic microscopic imaging in which spatial frequencies that are well outside the modulation transfer function of the collection optical system are recorded while maintaining the long working distance and wide field of view.

A novel blind deconvolution scheme for image restoration using recursive filtering

Abstract: We present a novel blind deconvolution technique for the restoration of linearly degraded images without explicit knowledge of either the original image or the point spread function. The technique applies to situations in which the scene consists of a finite support object against a uniformly black, grey, or white background. This occurs in certain types of astronomical imaging, medical imaging, and one-dimensional (1-D) gamma ray spectra processing, among others. The only information required are the nonnegativity of the true image and the support size of the original object. The restoration procedure involves recursive filtering of the blurred image to minimize a convex cost function. We prove convexity of the cost function, establish sufficient conditions to guarantee a unique solution, and examine the performance of the technique in the presence of noise. The new approach is experimentally shown to be more reliable and to have faster convergence than existing nonparametric finite support blind deconvolution methods. For situations in which the exact object support is unknown, we propose a novel support-finding algorithm.