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Actinic patterned mask inspection (APMI) is the last major part of the infrastructure required for EUV lithography to be developed. A coherent imaging approach is proposed as a plausible solution requiring incremental improvements to available components. Diffractive optics direct a mW 13.5nm coherent beam to the mask and to interfere at the imaging detector. A motion system translates the mask between exposures. A non-iterative algorithm generates a complex reflectivity (mask image) estimate from each interferogram, in real time with GPU hardware. Realistic simulation results and requirements for the system components are presented. Except for the FEL that is likely required, many elements of the system are simpler and likely less costly than an incoherent imager. The system can be configured to image the mask through a pellicle. Of note, focus tolerance is loose as the focal distance is a software parameter.

Surface-assisted laser desorption/ionization (SALDI) substrates have been fabricated using nanospiked polyurethane (PU) substrates that are replicated by a low-cost soft nanolithography method from silicon nanospike structures formed with femtosecond laser irradiations. The strongest mass spectrometry (MS) signal of Angiotensin II was obtained on 45-nm Au-coated nanospiked PU substrates. The effective ionization appears to be due to surface plasmon excitation. Such low-cost and identical SALDI substrates can be used for MS analysis of various molecules with high reproducibility. Copyright © 2011 John Wiley & Sons, Ltd.

Nearly index-matched optical elements are described that have application to aspherical, diffractive, and hybrid refractive -diffractive elements. Owing to the small difference in index, tolerances on the interfacial surface profile are much looser than for conventional aspherical and diffractive elements. A condition on both the index and the dispersion is described that results in an achromatic phase, thereby allowing for diffractive elements with high efficiency over broad spectral bands. Properties of the elements are described and compared with those of conventional diffractive elements. Analytical results and experimental measurements with an inexpensive element with 40 waves of asphericity are presented.

We describe a new high-resolution neutron-imaging detector. A neutron scintillator is imaged onto a photon-counting 2D imaging detector, with most of the scintillation used for event discrimination in this patented detector. Detection time and location are recorded, so neutron energy (time-of-flight) is measured for accelerator-based sources. We are currently fabricating a 25cmx25cm detector with 512x512 pixels and 100 ns time resolution. Results are presented for scintillator characterization measurements and imaging characteristics measured at IPNS, where the detector will reside.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A new gamma camera with intrinsically high-resolution is described. A scintillating crystal is imaged onto a photon-counting 2D imaging detector. Most of the light is directed to PMTs for energy determination in this patented detector. Detection time and position can be recorded. Time resolution is as fine as the scintillation pulse allows. Sub-millimeter resolution has been achieved and 2048 linear pixels are possible. We are fabricating a transportable detector with 25 cm sensitive diameter and 1024x1024 pixels. Results taken with a prototype detector are presented.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A method for designing and fabricating aspherical transmissive beam shaping elements for the visible and near-IR is described. Both rotationally symmetric and non-symmetric aspheres can be fabricated as Near-Index-Match™ optics. The aspherical surface is machined or mastered using a conventional NC machine. A sandwich of two transmissive materials is formed, with the refractive phase the product of the surface relief and the index difference. Both far-field (Dickey, Romero, and Holswade 1 ) beam shapers and near-field (Rhodes and Shealy 2 ) beam shapers can be realized, as well as two-element systems with phase correction of the shaped beam. Design methodologies and results are presented. Keywords: laser beam shaping, asphere, refractive 1. INTRODUCTION Near-Index-Match™ (NIM™) optics 3,4 are a convenient, low cost means of fabricating aspherical and diffractive optical elements. The principle behind NIM™ optics is illustrated in Figure 1. Two different materials with refractive indices n

Nematic liquid crystal spatial light modulators (LC-SLMs) have been proposed as wavefront correctors for adaptive optics (a summary of which is described in ref. 1 and references therein). For example, at the last OSA/ESO meeting on adaptive optics in Garching (1995) we described a high-quality LC-SLM which had 69-direct driven pixels which was custom designed for adaptive optics applications2. Additional work has been done with the goal of producing a polarization insensitive LC-SLM which does not suffer the reduced efficiency of a device which only works with a single polarization3. This paper demonstrates successful application of an LC-SLM to wavefront compensation and the first successful application of phase diversity sensing4 to wavefront compensation, to the best of our knowledge.

We report research results on phase diversity imaging, a technique for pre and post processing of atmospherically degraded images. The method uses an in-focus image and an out-of-focus Image to deduce the aberrating wavefront introduced by the atmosphere and telescope; and deconvolves the measured images to produce a near-diffraction-limited estimate of the object.

A novel design for a zero-order achromatic diffractive optical element is presented. Applications of the optical element are discussed. Tolerances on the material properties and fabrication considerations are presented. The predicted performance characteristics, including optical efficiency and effective bandwidth, are presented.

We present the first experimental results of recovery of the 2-D spatial coherence modulus and phase using fourth order correlation interferometry (FOCI). The technique, a generalization of intensity interferometry and laser speckle correlography, measures the correlation (I(x)A*(x+A)A(x+A+c)), where 1(x) and A*(x+E)A(x+A+e) are measured with separate, unconnected apertures. The result of the measurement is t*(A)i(+c), a cross-product of the spatial coherence factor that is analogous to the Knox-Thompson cross-spectrum in astronomical speckle imaging. The technique has applicability when the coherence function must be measured over distances A which are larger than the diameter D >> XE of the largest diffraction limited optic or amplitude interferometer and the field is a circular complex Gaussian random variable. An experiment is described which makes the correlation measurement on a series of laser speckle patterns. 1(x) and A*(x+A)A(x+A+e) are obtained from the focal spots of an array of lenslets. The measured coherence function is shown to agree with the expected value. The intensity image, given by the Fourier transform of the coherence function, is calculated and gives good agreement with the experiment target. The usefulness of the technique is discussed.

Knox-Thompson Speckle Imaging is studied when partial adaptive optic compensation is employed. A generalization of previous analysis allows treatment of the compensation, finite exposure time, anisoplanatism and non-zero spectral bandwidth within the extended Huygens-Fresnel framework. The compensation process is assumed statistically stationary and accounts for wavefront sensor photon noise. The effect of finite exposure time is treated assuming Taylor's hypothesis and the Bufton wind model. An innovation is a perturbation treatment of fmite spectral bandwidth effects accurate to Significant improvement results from partial compensation when 10 degrees of freedom can be corrected with < lrad2of phase error due to shot noise. The compensation also allows significantly greater spectral bandwidth for the speckle images relative to the uncompensated case. Strategies optimizing over compensation scale, spectral bandwidth, and exposure time are chosen to optimize the SNR for a fixed observation time. The results of the analysis are compared to a computer simulation with a wave-optics propagation code.

Small-scale thermal blooming is investigated with a linear theory, a fully non-linear wave optics propagation code, and a laboratory experiment The linear theory and the wave optics code show excellent agreement. The laboratory experiment shows excellent agreement with the modelling for the high spatial frequency modes.

We describe an instantaneous modal wave-front sensor. The sensor uses a Shack-Hartmann lenslet array to encode the wave-front distortion. A novel parallel electro-optic processor continuously converts the spot pattern to wave-front modes, e.g. Zernike polynomials, without a separate reconstructor. Using readily available components, the sensor can achieve MHz bandwidths for twenty modes. The bandwidth, sensitivity, and number of bits can vary for each mode to match the sensor to the disturbance in an optimal fashion. The proposed sensor has immediate application to beam control and turbulence sensing applications that require wide bandwidths. The measured wave-front modes can also be those of an adaptive optics system, directly providing control signals for the actuators of a deformable mirror. A similar electronic reconstructor mode is also described.

A method is presented for recovering the modulus and phase of the spatial coherence of a circular complex Gaussian random field, e.g., laser speckle, from fourth-order field correlations. A one-dimensional experimental verification of the method is described, and its usefulness for coherence function imaging is demonstrated. The variance of the measured quantity is shown to agree with a calculation for the high-light-level regime.

The variance of certain estimators relevant to intensity interferometry, laser speckle correlography, and fourth-order correlation interferometry are considered when the field amplitude obeys circular complex Gaussian statistics and the classical or high-light-level regime is obtained. A family of optimal unbiased estimators for |μ(Δ)|2, the squared modulus of the spatial-coherence factor, is found when a single measurement is performed and 〈I〉, the mean intensity, is known a priori. Calculations of the variance of multiple-measurement estimators for |μ(Δ)|2 and μ*(Δ)μ*(Δ + e) are performed. Results of statistical measurements of laser speckle are presented and are shown to agree with the calculations.

A generalization of intensity interferometry and imaging laser correlography (Hanbury Brown-Twiss effect) is described. The technique measures 〈l(x)A*(x + Δ + ϵ)A(x + Δ)〉, the correlation of the intensity at x with the field cross product at x + Δ over a distance ϵ. The result yields a term, μ*(Δ + ϵ)μ(Δ), analogous to the cross spectrum measured with the Knox-Thompson method for astronomical speckle imaging. The modulus and phase of the spatial coherence function can be recovered from this phase-difference-type term. The measurements involved do not require co-phasing over the large distance Δ. A light bucket measures l(x), and an interferometer with aperture ϵ (a lens is sufficient) measures A*(x + Δ + ϵ)A(x +Δ). The two measurements are numerically correlated. The results of a demonstration experiment that shows that the technique recovers modulus and phase information are presented.

A technique for finding the most probable object to have resulted in a set of images taken through the turbulent atmosphere is compared to speckle interferometry . The technique involves taking a Karhunen-Loeve decomposition of the set of distortion functions and approximating the probability distributions of the coefficients of the Karhunen-Loeve basis. The probability of an object giving rise to an image is defined as the product of the probabilities of the presumed independent coefficients of the basis vectors. A computer simulation was performed and parameter estimation was performed using the new technique and standard speckle interferometry. The maximum probability technique generates parameter estimates that have standard deviations over an order of magnitude smaller than the speckle interferometry estimates.

A new 2-D photon-counting camera, the PAPA (precision analog photon address) detector has been built, tested, and used successfully for the acquisition of speckle imaging data. The camera has 512 x 512 pixels and operates at count rates of at least 200,000/sec. In this paper, technical details on the camera are presented and some of the laboratory and astronomical results are included which demonstrate the detector's capabilities.

A new method is described for recovering the object energy spectrum in stellar speckle interferometry. An initial division estimate is improved with a constrained iterative algorithm that uses projections onto convex sets. The technique is demonstrated to recover the energy spectrum out to frequencies where the signal-to-noise ratio is

An integral representation of the bispectral optical transfer function, 〈T(α1)T(α2)T(−α1 − α2)〉, has been obtained in terms of the spatially random wave-front aberrations induced by the turbulent atmosphere and the deterministic wave-front aberrations of an optical system with an exit pupil in the shape of a slit (narrow rectangular aperture). Representative numerical calculations have been carried out for focused and defocused nonaberrated optical systems as well as for systems suffering from third-order coma. The phase of the bispectral transfer function is identically zero for the former cases but not for the latter case. The resultant contour plots of equal phase are shown and discussed.