Point Spread Function

Field-sequential color (FSC) is a high optical throughput technique for future green liquid crystal displays (LCDs). However, the FSC-LCD faces a lethal issue, color breakup (CBU) which degrades image clarity and prevents high level LCD-TV productions. We proposed the "180 Hz Stencil Field-Sequential-Color" method to redistribute intensities of the three primary color field-images to suppress CBU. By applying local color-backlight-dimming technology to FSC-LCDs, a low resolution colorful backlight panel combined with a high resolution color filter-less LC panel generated a "green-based multi-color" field-image which showed the most image luminance in the first field. Therefore, residual red and blue field-image intensities were reduced and effectively suppressed CBU when compared to field-rate increasing methods. In addition, to further implement hardware, the number of backlight divisions of 32 24 and a proper Gaussian point spread function profile were optimized via simulations while considering CBU reduction and image fidelity. Using optimized hardware parameters, the CBU phenomenon was suppressed by 50% of traditional RGB driving in simulation and was demonstrated on a 120 Hz 46-inch MVA LCD-TV.

In this paper, we describe the procedures to make epoxy resin and agarose phantoms designed using Mie scattering calculations. The phantoms are constructed to be used in the estimation of point spread function (PSF) of an optical coherence tomography (OCT) and evaluation of optical properties extraction (OPE) algorithm.

Ocean color imagery, when viewed from space, is degraded due to scattering by the atmosphere. The effect, also known as the adjacency effect, is especially important near the coast, sea-ice, and clouds, i.e., where the environment reflectance is much different from the target reflectance. The adjacency effect, however, may not be negligible in the open ocean. This is demonstrated by processing SeaWiFS imagery acquired over a typical upwelling system off the coast of Namibia, Africa. Ignoring the atmospheric point-spread function in the atmospheric correction algorithm or, equivalently, using a large-target formalism to describe the top-of-atmosphere reflectance, errors reaching over 10% are made on chlorophyll concentration retrievals. The structure of the spatial field of chlorophyll concentration is changed significantly after correction of the adjacency effect, with the influence of local processes comparatively decreased with increased distance. Correcting systematically (i.e., not only near the coast) Level 1b ocean color imagery for the adjacency effect is recommended. As a result, the accuracy, quality, and daily coverage of aerosol and ocean-color products would be improved substantially over water surfaces contiguous to land surfaces, sea-ice, clouds, and generally regions where spatial contrast is relatively large.

We took two-dimensional spectra with the filter spectrometer TESOS at the German Vacuum Tower Telescope, Tenerife, of an absorption line of the CH molecule and a Fe II-line in the G-band at 430.3 nm. We observed a region, close to disk center of the Sun, that showed a lot of structures with enhanced G-band intensity (up to 1.3 times the mean intensity of normal granulation). Our spectroscopic investigation of these structures suggests two classes which differ in their spectroscopic signature: (a) Bright structures caused by significant (up to 40%) weakening of absorption lines of the CH molecule; (b) bright structures only caused by an enhanced continuum intensity. In order to distinguish between those two classes we introduce a Bright Point Index (BPI) defined by the ratio of the normalized line depressions of the Fe II and the CH-line. The bright structures caused by weakening of the CH-lines have high BPI values and are accompanied by downflows. The remaining G-band bright structures have low BPI and are related to granules.

Aims. We present a spectral analysis of small-scale structures in the solar photosphere and investigate the influence of the speckle deconvolution technique on the line profiles. Methods. A short sequence of two-dimensional spectra is used, taken with the Telecentric Etalon Solar Spectrometer (TESOS) at the German Vacuum Tower Telescope on Tenerife. We observed two small pores surrounded by disturbed and by regular granulation in the non-magnetic neutral Iron line at 557.6 nm. In a first step, a speckle reconstruction is computed by applying an extended Knox-Thompson algorithm to the broad-band data. In a second step, the individual narrow-band filtergrams are deconvolved utilizing the information gained in the first step. We then perform a spectral analysis of the 2D spectra and compare the results obtained with the raw and the restored data. Results. Important spectral quantities, e.g. line position, line depression and line asymmetry are largely unchanged by the image reconstruction process. We derive the line asymmetry and the line-of-sight flow for granules and intergranular lanes and also for an isolated G-band bright point and find important differences between quiet and magnetically disturbed granulation: the granule centers in the quiet region show a strong asymmetry with significant blue shift (300 m/s) toward deeper layers, while the velocity in the disturbed area show virtually no height dependence. For the intergranular lanes the situation is reversed: no height dependence in the quiet area, significant red-shift toward deeper layers in the disturbed part. An isolated G-band bright point does not show any lineof-sight motion relative to its immediate surroundings. The map of LOS velocities derived from line-wing shifts shows a significant downflow around one of the pores measured in deep layers of the photosphere. Conclusions. In most cases we do not find any artefacts in the reconstructed line profiles that would compromise their usage for quantitative spectroscopy.

To date, all synthesis of G-band spectra, done for different empirical models of flux tube atmospheres, are compared with observations that are based on imaging (c.f. Sánchez Almeida 2001; . We add the spectroscopic information to the discussion about the high contrast of G-band bright points.

Images obtained with adaptive optics (AO) systems can be improved by using restoration techniques, the AOcorrection being only partial. However, these methods require an accurate knowledge of the system point spread function (PSF). Adaptive optics systems allow one to estimate the point spread function (PSF) during the science observation. Using data from the wave-front sensor (WFS), a direct estimation of the averaged parallel phase structure and an estimation of the noise on the measurements are provided. The averaged orthogonal phase structure (not seen by the system), and the aliasing covariance are estimated using an end-to-end AO simulation. Finally, the estimated PSF is reconstructed using the algorithm of Véran et al. (1997). 1 However, this reconstruction is non perfect. Several approximations are done (stationary resudual phase, gaussian phase, simulated aliasing, etc...) and can impact the optical transfer function (OTF) in the case of a rather poor correction. Our aim is to give an error budget for the whole PSF reconstruction process and to link this PSF reconstruction with a deconvolution algorithm that take into account this PSF variability. Indeed, a myopic deconvolution algorithm can be feed with a priori on the object and the PSF. The latter can be obtained by studying the PSF reconstruction error budget as follows in this paper. Finally, this work will lead to an estimation of the error on the deconvolved image allowing one to perform an accurate astrometry/photometry on the observed objects and to strengthen the contrast in the images. We concluded that to neglect the global crossterm or to estimate the aliasing on the measurements using simulations has no effect on the PSF reconstruction.

Adaptive optics systems provide a real-time compensation for atmospheric turbulence. However, the correction is often only partial, and a deconvolution is required for reaching the diffraction limit. The need for a regularized deconvolution is discussed, and such a deconvolution technique is presented. This technique incorporates a positivity constraint and some a priori knowledge of the object ͑an estimate of its local mean and a model for its power spectral density͒. This method is then extended to the case of an unknown point-spread function, still taking advantage of similar a priori information on the pointspread function. Deconvolution results are presented for both simulated and experimental data.

Context.Adaptive optics (AO) systems greatly increase the resolution of large telescopes, but produce complex point spread function (PSF) shapes, varying in time and across the field of view. The PSF must be accurately known since it provides crucial information about optical systems for design, characterization, diagnostics, and image post-processing.Aims.We develop here a model of the AO long-exposure PSF, adapted to various seeing conditions and any AO system. This model is made to match accurately both the core of the PSF and its turbulent halo.Methods.The PSF model we develop is based on a parsimonious parameterization of the phase power spectral density, with only five parameters to describe circularly symmetric PSFs and seven parameters for asymmetrical ones. Moreover, one of the parameters is the Fried parameterr0of the turbulence’s strength. This physical parameter is an asset in the PSF model since it can be correlated with external measurements of ther0, such as phase slo...

One of the primary scientific limitations of adaptive optics (AO) has been the incomplete knowledge of the point spread function (PSF), which has made it difficult to use AO for accurate photometry and astrometry in both crowded and sparse fields, for extracting intrinsic morphologies and spatially resolved kinematics, and for detecting faint sources in the presence of brighter sources. To address this limitation, we initiated a program to determine and demonstrate PSF reconstruction for science observations obtained with Keck AO. This paper aims to give a broad view of the progress achieved in implementing a PSF reconstruction capability for Keck AO science observations. This paper describes the implementation of the algorithms, and the design and development of the prototype operational tools for automated PSF reconstruction. On-sky performance is discussed by comparing the reconstructed PSFs to the measured PSF's on the NIRC2 science camera. The importance of knowing the control loop performance, accurate mapping of the telescope pupil to the deformable mirror and the science instrument pupil, and the telescope segment piston error are highlighted. We close by discussing lessons learned and near-term future plans.

Nowadays, transillumination imaging is more popular used in the medical field with the development of the vein finder application and also the non-invasive diagnosis applications. The less absorption of those main chromophores (melanin, oxy-hemoglobin, deoxy-hemoglobin, and water) of biological tissue within the near-infrared range (700 -1200 nm) causes the relatively high transmission of the near-infrared light through biological tissue. They give us an "optical window" to seethrough the biological tissue non-invasively. Because of the high absorption of oxy-hemoglobin, deoxy-hemoglobin within the near-infrared range in comparison with these other parts in tissue, we can able to obtain a two dimensional (2D) transillumination image of the internal absorption structure such as blood vessel network, liver structure... in the body non-invasively. Using the lightemitting diode (LED)'s array to illuminate the human arm and using a low-cost camera to capture the image, we could obtain the blood vessel network image of the human arm. The captured image is blurred and difficult to distingue the structure inside. Because the camera captured the blood vessel network shadow that diffused on the skin surface. Professor Koichi Shimizu devised the depth-dependent point spread function (PSF) to describe the scattering effect from a light point source to the observation surface of a slab diffused medium by applying the diffusion approximation. By suppressing the scattering effect successfully, we could restore the clear image from the blurred image by de-convolution with the appropriated PSF. With our proposed technique, we could reconstruct the absorbing structures such as the kidney and liver in biological tissue. Using the restored images from different angles of view, we could reconstruct the cross-sectional images and three-dimensional image of the absorbing structures in an animal's abdomen. However, the depth information of the absorbing-structure was required in practice to calculate the appropriate PSF. Therefore, in order to make this method more practical, the depth information is crucial. In this paper, we proposed the novel techniques for estimating the parameters of absorbing structure (depth, center location, and width) in the turbid medium by using the convolution and deconvolution operations with the devised PSF. Firstly, by observing images with two-wavelength selected at which the absorption and scattering properties of the medium are different. While changing the depth step-by-step, two convoluted images were compared after convolving the captured image at one of the wavelengths with the PSF calculated by using the absorption and scattering coefficients from another wavelength. We can obtain the correct depth that gives the minimum difference between the two convoluted images. Secondly, we proposed the technique to estimate the depth information from a single transillumination image in order to make this method more practical. Finally, the absorbing structure image can be restored by suppressing the scattering effect. The proposed techniques were validated and examined not only in the simulation but also in the experiment.

for the collection of diffuse diffraction data in anticipation of coherent x-ray imaging experiments that will be conducted at the Linac Coherent Light Source (LCLS) at the Stanford Linear Accelerator Center (SLAC). The detector is designed to collect x-rays scattered from femtosecond pulses produced by the LCLS x-ray laser at framing rates up to 120 Hz. Because x-rays will arrive on femtosecond time scales, the detector must be able to deal with instantaneous count-rates in excess of 10 17 photons per second per pixel. A low-noise integrating front-end allows the detector to simultaneously distinguish single photon events in low-flux regions of the diffraction pattern while recording up to several thousand x-rays per pixel in more intense regions. The detector features a per-pixel programmable twolevel gain control that can be used to create an arbitrary 2-D, two-level gain pattern across the detector; massively parallel 14bit in-pixel digitization; and frame rates in excess of 120 Hz. The first full-scale detector will be 758 x 758 pixels with a pixel size of 110 x 110 microns made by tiling CMOS ASICs that are bumpbonded to high-resistivity silicon diodes. X-ray testing data of the first 185 x 194 pixel bump-bonded ASICs is presented. The measurements presented include confirmation of single photon sensitivity, pixel response profiles indicating a nearly single-pixel point spread function, radiation damage measurements and noise performance.

We study the noise characteristics of an image reconstruction algorithm that incorporates a model of the non-stationary detector blurring (DB) for a mouse-imaging positron emission tomography (PET) scanner. The algorithm uses ordered subsets expectation maximization (OSEM) image reconstruction, which is used to suppress statistical noise. Including the non-stationary detector blurring in the reconstruction process (OSEM(DB)) has been shown to increase contrast in images reconstructed from measured data acquired on the fully-3D MiCES PET scanner developed at the University of Washington. As an extension, this study uses simulation studies with a fully-3D acquisition mode and our proposed FORE+OSEM(DB) reconstruction process to evaluate the volumetric contrast versus noise trade-offs of this approach. Multiple realizations were simulated to estimate the true noise properties of the algorithm. The results show that incorporation of detector blurring (FORE+OSEM(DB)) into the reconstruction process improves the contrast/noise trade-offs compared to FORE+OSEM in a radially dependent manner. Adding post reconstruction 3D Gaussian smoothing to FORE+OSEM and FORE+OSEM(DB) reduces the contrast versus noise advantages of FORE+OSEM(DB).

This article describes a single ring version of the micro crystal element scanner (MiCES) and investigation of its spatial resolution imaging characteristics for mouse positron emission tomography (PET) imaging. This single ring version of the MiCES system, referred to as QuickPET II, consists of 18 MiCE detector modules mounted as a single ring in a vertical gantry. The system has a 5.76-cm transverse field of view and a 1.98-cm axial field of view. In addition to the scanner and data acquisition system, we have developed an iterative reconstruction that includes a model of the system's detector response function. Evaluation images of line sources and mice have been acquired. Using filtered backprojection, the resolution for a reconstructed line source has been measured at 1.2 mm full width at half maximum. F-18-2-fluoro-2-deoxyglucose mouse PET images are provided. The result shows that QuickPET II has the imaging characteristics to support high-resolution, static mouse PET studies using 18-F labeled compounds. Mol Imaging (2005) 4, 117 -127.

Physical positioning of scintillation crystal detector blocks in Positron Emission Tomography (PET) scanners is not always exact. We test a proof of concept methodology for the determination of the six degrees of freedom for detector block positioning errors by utilizing a rotating point source over stepped axial intervals. To test our method, we created computer simulations of seven Micro Crystal Element Scanner (MiCES) PET systems with randomized positioning errors. The computer simulations show that our positioning algorithm can estimate the positions of the block detectors to an average of one-seventh of the crystal pitch tangentially, and one-third of the crystal pitch axially. Virtual acquisitions of a point source grid and a distributed phantom show that our algorithm improves both the quantitative and qualitative accuracy of the reconstructed objects. We believe this estimation algorithm is a practical and accurate method for determining the spatial positions of scintillatio...

The FORE+OSEM(DB) image reconstruction method has been proposed for the fully-3D MiCES PET scanner under construction at the University of Washington. It is based on Fourier rebinning followed by 2D OSEM and an incorporated model of detector blurring (DB). As an extension, this paper presents the noise/resolution characteristics of this method. Multiple realizations were simulated to estimate the noise properties of the algorithm. The results are compared with OSEM followed by post reconstruction 3D Gaussian smoothing. The results show that the incorporation of detector blurring (OSEM(DB)) into the system matrix improves resolution compared to OSEM, while also inducing an increased variance at all radial locations. In addition, radially-varying noise characteristics are more apparent with OSEM(DB) than with OSEM.

In this paper, we investigated the performance characteristics of continuous miniature crystal element (cMiCE) detectors. Versions with a 25 mm by 25 mm by 4 mm-thick LSO crystal and with a 50 mm by 50 mm by 8 mm-thick LYSO crystal were evaluated. Both detectors utilize a 64-channel flat panel photomultiplier tube (PMT). The intrinsic spatial resolution for the detectors was evaluated using Anger (i.e., simple centroid) positioning and a statistics based positioning (SBP) algorithm. We also compared the intrinsic spatial resolution for the 8-mm-thick LYSO crystal using different reflective materials (e.g., TFE Teflon, white paint, and a polymer mirror film) applied on the entrance surface of the crystal. The average energy resolution was 20% for the 4-mm-thick LSO crystal and ranged from 16% to 21%, depending upon reflective material, for the 8-mm-thick LYSO crystal. The average intrinsic spatial resolution for the 4-mm-thick crystal was 1.8-mm full width at half maximum (FWHM) for ...

Objective : Detector designs for small animal scanners are currently dominated by discrete crystal implementations. However, given the small crystal cross-sections required to obtain very high resolution, discrete designs are typically expensive, have low packing fraction, reduced light collection, and are labor intensive to build. To overcome these limitations we have investigated the feasibility of using a continuous miniature crystal element (cMiCE) detector module for high resolution small animal PET applications. Methods : The detector module consists of a single continuous slab of LSO, 25×25 mm 2 in exposed cross-section and 4 mm thick, coupled directly to a PS-PMT (Hamamatsu R5900-00-C12). The large area surfaces of the crystal were polished and painted with TiO 2 and the short surfaces were left unpolished and painted black. Further, a new statistics based positioning (SBP) algorithm has been implemented to address linearity and edge effect artifacts that are inherent with c...

We study the noise characteristics of an image reconstruction algorithm that incorporates a model of the non-stationary detector blurring (DB) for a mouse-imaging positron emission tomography (PET) scanner. The algorithm uses ordered subsets expectation maximization (OSEM) image reconstruction, which is used to suppress statistical noise. Including the non-stationary detector blurring in the reconstruction process [OSEM(DB)] has been shown to increase contrast in images reconstructed from measured data acquired on the fully-3D MiCES PET scanner developed at the University of Washington. As an extension, this study uses simulation studies with a fully-3D acquisition mode and our proposed FORE+ OSEM(DB) reconstruction process to evaluate the volumetric contrast versus noise trade-offs of this approach. Multiple realizations were simulated to estimate the true noise properties of the algorithm. The results show that incorporation of detector blurring FORE+OSEM(DB) into the reconstructi...

We study the noise characteristics of an image reconstruction algorithm that incorporates a model of the non-stationary detector blurring (DB) for a mouse-imaging positron emission tomography (PET) scanner. The algorithm uses ordered subsets expectation maximization (OSEM) image reconstruction, which is used to suppress statistical noise. Including the non-stationary detector blurring in the reconstruction process (OSEM(DB)) has been shown to increase contrast in images reconstructed from measured data acquired on the fully-3D MiCES PET scanner developed at the University of Washington. As an extension, this study uses simulation studies with a fully-3D acquisition mode and our proposed FORE+OSEM(DB) reconstruction process to evaluate the volumetric contrast versus noise trade-offs of this approach. Multiple realizations were simulated to estimate the true noise properties of the algorithm. The results show that incorporation of detector blurring (FORE+OSEM(DB)) into the reconstruction process improves the contrast/noise trade-offs compared to FORE+OSEM in a radially dependent manner. Adding post reconstruction 3D Gaussian smoothing to FORE+OSEM and FORE+OSEM(DB) reduces the contrast versus noise advantages of FORE+OSEM(DB).

Physical positioning of scintillation crystal detector blocks in Positron Emission Tomography (PET) scanners is not always exact. We test a proof of concept methodology for the determination of the six degrees of freedom for detector block positioning errors by utilizing a rotating point source over stepped axial intervals. To test our method, we created computer simulations of seven Micro Crystal Element Scanner (MiCES) PET systems with randomized positioning errors. The computer simulations show that our positioning algorithm can estimate the positions of the block detectors to an average of one-seventh of the crystal pitch tangentially, and one-third of the crystal pitch axially. Virtual acquisitions of a point source grid and a distributed phantom show that our algorithm improves both the quantitative and qualitative accuracy of the reconstructed objects. We believe this estimation algorithm is a practical and accurate method for determining the spatial positions of scintillation detector blocks.

The FORE+OSEM(DB) image reconstruction method has been proposed for the fully-3D MiCES PET scanner under construction at the University of Washington. It is based on Fourier rebinning followed by 2D OSEM and an incorporated model of detector blurring (DB). As an extension, this paper presents the noise/resolution characteristics of this method. Multiple realizations were simulated to estimate the noise properties of the algorithm. The results are compared with OSEM followed by post reconstruction 3D Gaussian smoothing. The results show that the incorporation of detector blurring (OSEM(DB)) into the system matrix improves resolution compared to OSEM, while also inducing an increased variance at all radial locations. In addition, radially-varying noise characteristics are more apparent with OSEM(DB) than with OSEM.

Objective: Detector designs for small animal scanners are currently dominated by discrete crystal implementations. However, given the small crystal cross-sections required to obtain very high resolution, discrete designs are typically expensive, have low packing fraction, reduced light collection, and are labor intensive to build. To overcome these limitations we have investigated the feasibility of using a continuous miniature crystal element (cMiCE) detector module for high resolution small animal PET applications. Methods: The detector module consists of a single continuous slab of LSO, 25 Â 25 mm 2 in exposed cross-section and 4 mm thick, coupled directly to a PS-PMT (Hamamatsu R5900-00-C12). The large area surfaces of the crystal were polished and painted with TiO 2 and the short surfaces were left unpolished and painted black. Further, a new statistics based positioning (SBP) algorithm has been implemented to address linearity and edge effect artifacts that are inherent with conventional Anger style positioning schemes. To characterize the light response function (LRF) of the detector, data were collected on a coarse grid using a highly collimated coincidence setup. The LRF was then estimated using cubic spline interpolation. Detector performance has been evaluated for both SBP and Anger based decoding using measured data and Monte Carlo simulations. Results: Using the SBP scheme, edge artifacts were successfully handled. Simulation results show that the useful field of view (UFOV) was extended to B22 Â 22 mm 2 with an average point spread function of B0.5 mm full width of half maximum (FWHM PSF ). For the same detector with Anger decoding the UFOV of the detector was B16 Â 16 mm 2 with an average FWHM PSP of B0.9 mm. Experimental results yielded similar differences between FOV and resolution performance. FWHM PSF for the SBP and Anger based method was 1.4 and 2.0 mm, uncorrected for source size, with a 1 mm diameter point source, respectively. Conclusion: A continuous detector module with an average FWHM PSF approaching one millimeter has been built and tested. Furthermore, the results demonstrate that our SBP scheme yields improved performance over traditional Anger techniques for our cMiCE detector.

Exoplanet direct imaging using adaptive optics (AO) is often limited by non-common path aberrations (NCPAs) and aberrations that are invisible to traditional pupil-plane wavefront sensors (WFSs). This can be remedied by focal-plane (FP) WFSs that characterize aberrations directly from a final science image. Photonic lanterns (PLs) can act as low-order FPWFSs with the ability to direct some light to downstream science instruments. Using a PL on the SEAL (Santa Cruz Extreme AO Laboratory) high-contrast imaging testbed, we demonstrate (1) linear ranges and (2) closed-loop control. Additionally, we simulate the use of the PL in a multi-wavefront sensor AO system, in which multiple WFSs feed back to the same common-path deformable mirror. Building on previous multi-WFS AO demonstrations on SEAL, we simulate a modulated pyramid WFS to sense aberrations of high spatial order and large amplitude, and the PL to sense low order aberrations including NCPAs. We assess adaptive optics performance in this setting using three different PL wavefront reconstruction algorithms. We also provide a new method to experimentally identify the propagation matrix of a PL, making advanced model-based algorithms practical. This work demonstrates the role of photonic technologies and multi-stage wavefront sensing in the context of extreme AO and high contrast imaging.

High-contrast imaging has been used to discover and characterize dozens of exoplanets to date. The primary limiting performance factor for these instruments is contrast, the ratio of exoplanet to host star brightness that an instrument can successfully resolve. Contrast is largely determined by wavefront error, consisting of uncorrected atmospheric turbulence and optical aberrations downstream of AO correction. Single-point diamond turning allows for high-precision optics to be manufactured for use in astronomical instrumentation, presenting a cheaper and more versatile alternative to conventional glass polishing. This work presents measurements of wavefront error for diamond-turned aluminum optics in the Slicer Combined with an Array of Lenslets for Exoplanet Spectroscopy (SCALES) instrument, a 2-5 micron coronagraphic integral field spectrograph under construction for Keck Observatory. Wavefront error measurements for these optics are used to simulate SCALES' point spread function using physical optics propagation software poppy, showing that SCALES' contrast performance is not limited by wavefront error from internal instrument optics.

Focal plane wavefront sensing and control is a critical approach to reducing noncommon path errors between the a conventional astronomical adaptive optics (AO) wavefront sensor (WFS) detector and science camera. However, in addition to mitigating non-common path errors, recent focal plane wavefront sensing techniques have been developed to operate at speeds fast enough to enable "multi-WFS" AO, where residual atmospheric errors are further corrected by a focal plane WFS. Although a number of such techniques have been recently developed for coronagraphic imaging, here we present one designed for non-coronagraphic imaging. Utilizing conventional AO system components, this concept additionaly requires (1) a detector imaging the focal plane of the WFS light source and (2) a pupil plane optical chopper device that is non-common path to the first WFS and is synchronized to the focal plane imager readout. These minimal hardware requirements enable the temporal amplitude modulation to resolve the sine ambiguity of even wavefront modes for both low, mid, and high wavefront spatial frequencies. Similar capabilities have been demonstrated with classical phase diversity by defocusing the detector, but such techniques are incompatible with simultaneous science observations. This optical chopping techniqe, however, enables science imaging at up to a 50% duty cycle. We present both simulations and laboratory validation of this concept on SEAL, the Santa Cruz Extreme AO Laboratory testbed.

V. Dangendorf A new imaging method that combines high-efficiency fast-neutron detection with sub-ns time resolution is presented. This is achieved by exploiting the high neutron detection efficiency of a thick scintillator and the fast timing capability and flexibility of light-pulse detection with a dedicated image intensifier. The neutron converter is a plastic scintillator slab or, alternatively, a scintillating fibre screen. The scintillator is optically coupled to a pulse counting image intensifier which measures the 2-dimensional position coordinates and the Time-Of-Flight (TOF) of each detected neutron with an intrinsic time resolution of less than 1 ns. Large-area imaging devices with high count rate capability can be obtained by lateral segmentation of the optical readout channels.

We present a new approach to the pointing determination of Imaging Atmospheric Cherenkov Telescopes (IACTs). This method is universal and can be applied to any IACT with minor modifications. It uses the trajectories of the stars in the field of view of the IACT's main camera and requires neither dedicated auxiliary hardware nor a specific data taking mode. The method consists of two parts: firstly, we reconstruct individual star positions as a function of time, taking into account the point spread function of the telescope; secondly, we perform a simultaneous fit of all reconstructed star trajectories using the orthogonal distance regression method. The method does not assume any particular star trajectories, does not require a long integration time, and can be applied to any IACT observation mode. The performance of the method is assessed with commissioning data of the Large-Sized Telescope prototype (LST-1), showing the method's stability and remarkable pointing performance of the LST-1 telescope.

We present a new approach to the pointing determination of Imaging Atmospheric Cherenkov Telescopes (IACTs). This method is universal and can be applied to any IACT with minor modifications. It uses the trajectories of the stars in the field of view of the IACT's main camera and requires neither dedicated auxiliary hardware nor a specific data taking mode. The method consists of two parts: firstly, we reconstruct individual star positions as a function of time, taking into account the point spread function of the telescope; secondly, we perform a simultaneous fit of all reconstructed star trajectories using the orthogonal distance regression method. The method does not assume any particular star trajectories, does not require a long integration time, and can be applied to any IACT observation mode. The performance of the method is assessed with commissioning data of the Large-Sized Telescope prototype (LST-1), showing the method's stability and remarkable pointing performance of the LST-1 telescope.

The Infrared Multi-Object Spectrometer (IRA408 is a principle investigator class instrument for the Kitt Peak National Observatory 4 and 2.1 m telescopes. IRA4OS is a near-IR (0.8 -2.5 pm) spectrometer with low-to mid-resolving power (R = 300 -3000). IRA4OS produces simultaneous spectra of -100 objects in its 2.8 x 2.0 arc-min field of view (4 m telescope) using a commercial Micro Electro-Mechanical Systems (MEMS) micro-mirror array (MMA) from Texas Instruments. The I W O S optical design consists of two imaging subsystems. The focal reducer images the focal plane of the telescope onto the MMA field stop, and the spectrograph images the MMA onto the detector. We describe ambient breadboard subsystem alignment and imaging pe~%ormance of each stage independently, and ambient imaging performance of the fully assembled instrument-Lnterferometric measurements of subsystem wavefront error serve as a qualitative alignment guide, and are accomplished using a commercial, modified Twyman-Green laser unequal path interferometer. Image testing provides verification of the optomechanical alignment method and a measurement of nearangle scattered light due to mirror small-scale surface error. Image testing is performed at multiple field points. A mercury-argon pencil lamp provides a spectral line at 546.1 nm, a blackbody source provides a line at 1550 nm, and a CCD camera and IR camera are used as detectors. We use commercial optical modeling sofiware to predict the pointspread function and its effect on inshument slit transmission and resolution. Our breadboard and instrument level test results validate this prediction. We conclude with an instrument performance prediction for cryogenic operation and first light in late 2003.

Purpose-To determine the relative contributions of optical and non-optical sources of intrinsic blur to variations in visual acuity (VA) among normally sighted subjects. Methods-Best-corrected VA of sixteen normally sighted subjects was measured using briefly presented (59 ms) tumbling E optotypes that were either unblurred or blurred through convolution with Gaussian functions of different widths. A standard model of intrinsic blur was used to estimate each subject's equivalent intrinsic blur (σ int ) and VA for the unblurred tumbling E (MAR 0 ). For 14 subjects, a radially averaged optical point spread function due to higher-order aberrations was derived by Shack-Hartmann aberrometry and fit with a Gaussian function. The standard deviation of the best-fit Gaussian function defined optical blur (σ opt ). An index of nonoptical blur (η) was defined as: 1-σ opt /σ int . A control experiment was conducted on 5 subjects to evaluate the effect of stimulus duration on MAR 0 and σ int . Results-Log MAR 0 for the briefly presented E was correlated significantly with log σ int (r = 0.95, p < 0.01), consistent with previous work. However, log MAR 0 was not correlated significantly with log σ opt (r = 0.46, p = 0.11). For subjects with log MAR 0 equivalent to approximately 20/20 or better, log MAR 0 was independent of log η, whereas for subjects with larger log MAR 0 values, log MAR 0 was proportional to log η. The control experiment showed a statistically significant effect of stimulus duration on log MAR 0 (p < 0.01) but a non-significant effect on σ int (p = 0.13). Conclusions-The relative contributions of optical and non-optical blur to VA varied among the subjects, and were related to the subject's VA. Evaluating optical and non-optical blur may be useful for predicting changes in VA following procedures that improve the optics of the eye in patients with both optical and non-optical sources of VA loss. visual acuity; Gaussian blur; intrinsic blur; optical blur Clinical measures of best-corrected visual acuity (VA) can vary substantially among normally sighted individuals, 1 for reasons that have not been fully resolved. A potential factor that may underlie the variation is inter-subject differences in equivalent intrinsic blur, which is an estimate of the intrinsic blur of the visual system. Although the intrinsic blur of the visual system cannot be measured directly, its value can be estimated using the equivalent intrinsic blur paradigm.

Purpose-To determine the relative contributions of optical and non-optical sources of intrinsic blur to variations in visual acuity (VA) among normally sighted subjects. Methods-Best-corrected VA of sixteen normally sighted subjects was measured using briefly presented (59 ms) tumbling E optotypes that were either unblurred or blurred through convolution with Gaussian functions of different widths. A standard model of intrinsic blur was used to estimate each subject's equivalent intrinsic blur (σ int ) and VA for the unblurred tumbling E (MAR 0 ). For 14 subjects, a radially averaged optical point spread function due to higher-order aberrations was derived by Shack-Hartmann aberrometry and fit with a Gaussian function. The standard deviation of the best-fit Gaussian function defined optical blur (σ opt ). An index of nonoptical blur (η) was defined as: 1-σ opt /σ int . A control experiment was conducted on 5 subjects to evaluate the effect of stimulus duration on MAR 0 and σ int . Results-Log MAR 0 for the briefly presented E was correlated significantly with log σ int (r = 0.95, p < 0.01), consistent with previous work. However, log MAR 0 was not correlated significantly with log σ opt (r = 0.46, p = 0.11). For subjects with log MAR 0 equivalent to approximately 20/20 or better, log MAR 0 was independent of log η, whereas for subjects with larger log MAR 0 values, log MAR 0 was proportional to log η. The control experiment showed a statistically significant effect of stimulus duration on log MAR 0 (p < 0.01) but a non-significant effect on σ int (p = 0.13). Conclusions-The relative contributions of optical and non-optical blur to VA varied among the subjects, and were related to the subject's VA. Evaluating optical and non-optical blur may be useful for predicting changes in VA following procedures that improve the optics of the eye in patients with both optical and non-optical sources of VA loss. visual acuity; Gaussian blur; intrinsic blur; optical blur Clinical measures of best-corrected visual acuity (VA) can vary substantially among normally sighted individuals, 1 for reasons that have not been fully resolved. A potential factor that may underlie the variation is inter-subject differences in equivalent intrinsic blur, which is an estimate of the intrinsic blur of the visual system. Although the intrinsic blur of the visual system cannot be measured directly, its value can be estimated using the equivalent intrinsic blur paradigm.

We design microsphere arrays with predetermined positions of microspheres, for capturing targets at low concentrations. To optimize the design parameters, we compute the Ziv-Zakai bound (ZZB) on the errors in estimating the target concentrations. We numerically demonstrate our design by computing the minimal distance between the microspheres and the optimal imaging temperature, for a desired level of errors. We also validate that, at low target concentrations, the statistical design using the ZZB is more precise than that using the posterior Cramér-Rao bound. We further quantitatively evaluate the effect of the fluorescence microscope point-spread function on the design performance, which provide useful guides to the device design and implementation. The key advantages of the proposed microsphere arrays are error-free target identification, simplified data analysis, high packing density, and reduced cost.

Realizing both high temporal and spatial resolution across a large volume is a key challenge for 3D fluorescent imaging. Towards achieving this objective, we introduce an interferometric multifocus microscopy (iMFM) system, a combination of multifocus microscopy (MFM) with two opposing objective lenses. We show that the proposed iMFM is capable of simultaneously producing multiple focal plane interferometry that provides axial superresolution and hence isotropic 3D resolution with a single exposure. We design and simulate the iMFM microscope by employing two special diffractive optical elements. The point spread function of this new iMFM microscope is simulated and the image formation model is given. For reconstruction, we use the Richardson-Lucy deconvolution algorithm with total variation regularization for 3D extended object recovery, and a maximum likelihood estimator (MLE) for single molecule tracking. A method for determining an initial axial position of the molecule is also proposed to improve the convergence of the MLE. We demonstrate both theoretically and numerically that isotropic 3D nanoscopic localization accuracy is achievable with an axial imaging range of 2um when tracking a fluorescent molecule in three dimensions and that the diffraction limited axial resolution can be improved by 3-4 times in the single shot wide-field 3D extended object recovery. We believe that iMFM will be a useful tool in 3D dynamic event imaging that requires both high temporal and spatial resolution.

Multiparticle tracking with scanning confocal and multiphoton fluorescence imaging is increasingly important for elucidating biological function, as in the transport of intracellular cargo-carrying vesicles. We demonstrate a simple rapid-sampling stochastic scanning multiphoton multifocal microscopy (SS-MMM) fluorescence imaging technique that enables multiparticle tracking without specialized hardware at rates 1,000 times greater than conventional single point raster scanning. Stochastic scanning of a diffractive optic generated 10x10 hexagonal array of foci with a white noise driven galvanometer yields a scan pattern that is random yet space-filling. SS-MMM creates a more uniformly sampled image with fewer spatio-temporal artifacts than obtained by conventional or multibeam raster scanning. SS-MMM is verified by simulation and experimentally demonstrated by tracking microsphere diffusion in solution.

Single-molecule-based super-resolution fluorescence microscopy has recently been developed to surpass the diffraction limit by roughly an order of magnitude. These methods depend on the ability to precisely and accurately measure the position of a single-molecule emitter, typically by fitting its emission pattern to a symmetric estimator (e.g. centroid or 2D Gaussian). However, single-molecule emission patterns are not isotropic, and depend highly on the orientation of the molecule&#39;s transition dipole moment, as well as its z-position. Failure to account for this fact can result in localization errors on the order of tens of nm for in-focus images, and ~50-200 nm for molecules at modest defocus. The latter range becomes especially important for three-dimensional (3D) single-molecule super-resolution techniques, which typically employ depths-of-field of up to ~2 μm. To address this issue we report the simultaneous measurement of precise and accurate 3D single-molecule position an...

Wide-field microscopy with a double-helix point spread function (DH-PSF) provides three-dimensional (3D) position information beyond the optical diffraction limit. We compare the theoretical localization precision for an unbiased estimator of the DH-PSF to that for 3D localization by astigmatic and biplane imaging using Fisher information analysis including pixelation and varying levels of background. The DH-PSF results in almost constant localization precision in all three dimensions for a 2 μm thick depth of field while astigmatism and biplane improve the axial localization precision over smaller axial ranges. For high signal-to-background ratio, the DH-PSF on average achieves better localization precision.

We analyze the optical properties of m-sized rings of gold nanoparticles by the combination of extinction spectroscopy, surface enhanced Raman scattering ͑SERS͒ spectroscopy and microscopic dark field imaging in two variants. The imaging process relies on either SERS from methylene blue dye molecules adsorbed on the nanoparticles or elastically scattered light. Whereas elastically scattered light images are governed by the coherence and intensity of the light scattered from the particles, SERS images reflect the optical near field of the particles averaged incoherently over a surface area corresponding to the point spread function of the microscope. From the analysis of the extinction spectra, scattered light and SERS images, we find that near field interaction of the single gold nanoparticles in the rings plays a minor role. Both scattered light and SERS images are well reproduced by simple model calculations. Due to the different signal generation and coherence properties, the combination of both imaging methods is a useful means in the characterization of optical properties of nanostructured metal surfaces.

The Murchison Widefield Array (MWA) is a low frequency radio synthesis array currently under construction in the radio quiet Western Australian outback. The MWA will be the first of a new generation of interferometers to capitalize on the enormous recent technological advances in the capabilities of digital signal processing hardware and increased affordability of computing. The MWA design has been

Low-coherence interferometry is combined with confocal scanning to provide remote refractive index and thickness measurements of transparent materials. The influence of lens aberrations in the confocal measurement is assessed through investigation of the axial point-spread functions (APSFs) generated using optical configurations comprised of paired aspherics and paired achromats. Off-axis parabolic mirrors are suggested as an alternative to lenses and are shown to exhibit much more symmetric APSFs provided the system numerical aperture is not too high. Refractive index and thickness measurements are made with each configuration with most mirror pairings offering better than twice the repeatability and accuracy of either lens pairing.

Laser countermeasures against infrared focal plane array cameras aim to saturate the full camera image. In this paper we will discuss the results of three different dazzling experiments performed with MWIR lasers and show that the obtained results are independent of the read-out mechanism of the camera and can be explained by an expression derived from the point spread function of the optics. This expression also allows us to estimate the required laser power to saturate a complete focal plane array in a camera system. Simulated Images with simulated dazzling effects based on this expression will be shown.

Coded aperture 3D imaging techniques have been rapidly evolving in the recent years. The two main directions of evolution are in aperture engineering to generate the optimal optical field and in development of computational reconstruction to reconstruct the object’s image from the intensity distribution with a minimal noise. The goal is to find the ideal aperture-reconstruction method pair and if not, to optimize one to match the other for designing an imaging system with required 3D imaging characteristics. Lucy-Richardson-Rosen algorithm (LR2A), a recently developed computational reconstruction method was found to perform better than its predecessors such as matched filter, Weiner filter, phase-only filter, Lucy-Richardson algorithm and non-linear reconstruction (NLR) for certain apertures when the point spread function (PSF) is a real and symmetric function. For other cases of PSF, NLR performed better than the rest of the methods. In this tutorial, LR2A has been presented as a g...

Characterizing the point spread function (PSF) of a PET tomograph is important for assessing its performance and provides a useful model for restoration of the tomographic image. The PSF of ring PET tomographs is known to be spatiallyvariant and difficult to obtain because it must be reconstructed from projections. A mathematical model was developed to simulate the data acquisition from a point source and to reconstruct the PSF taking into account the full description of the detector response functions. In order to investigate the effect of the detector weighting function on the PSF, the reconstruction, based on the filtered backprojection algorithm, was implemented with three classes of weighting functions of decreasing complexity: exact, locally invariant and constant. Significant discrepancies are observed to result from the different hypothesis and this is shown to lead to distorted PSF and to erroneous estimates of the intrinsic resolution off the center of the tomograph.