Non-inertial scan angle multiplier for expanded fields-of-view

Investigations on laser actuation and life cycle characteristics of NiTi shape memory alloy bimorph for non-contact functional applications

: The report describes the effort to design and build a high gain, electronically steerable, millimeter antenna system. The antenna was constructed, adjusted for optimum performance and an extensive testing program carried out. The tests included measurements of radiation patterns at various scan angles, gain measurements, control power requirements, scan speed, and hysteresis effects. Consideration was also given to average and peak RF power and antenna efficiency. Results indicate that an antenna array of 5 elements is capable of scanning a beam 50 degrees at a rate of one degree per millisecond. The overall efficiency of this array was 60 percent taking into account both the illumination taper and insertion loss in the feed elements. Scanning both the element and array patterns eliminated the grating lobe phenomena normally associated with arrays of many wavelength elements. (Author)

The growing interest in carbon-fiber-reinforced-plastics (CFRP) leads to a rising demand for cost-efficient, alternative production methods, such as laser-remote-cutting. Since the cycle times, particularly in the automotive industry, represent a significant cost factor, this paper presents a method for reducing the heat-affected zone (HAZ) in the CFRP-laminate while maximizing the cutting speed. In pursuing this goal, in this paper, a comparison is made between a multi- and a single-mode laser system. In addition, simulation is used to investigate which mechanisms contribute to the formation of the HAZ and the effect of the delay times between the exposures on the HAZ. For the comparison of the beam sources, attempts are made with regard to the required cumulative energy per unit length to achieve a complete cut. The developed numerical simulation takes into account the thermal decomposition of the plastic matrix as well as the fibers, the heat conduction in the laminate, the flow of the gaseous decomposition products in the kerf and the heat transfer by forced convection on the cutting edge, the layer setup, the material properties as well as the laser parameters power, scanning speed, exposure number, and the delay times between the exposures. By means of Monte-Carlo-simulation, an optimization of the HAZ or the sum of all delay times is carried out. The experiments show that a complete cut with the single-mode laser requires a higher energy than the multi-mode system. It can be shown by the simulation that the primary target conflict in laser beam cutting of CFRP with several exposures exists between the average width of the heat-affected zone and the sum of the delay times between the exposures. The sum of the delay times is decisive in particular for the effective cutting speed. The simulation also shows that as a rule at least 50% of the width of the heat-affected zone is caused by the flow of the gaseous process emission within the kerf. The optimization could be used to calculate and validate that a skillful selection of the delay times results in a reduction of the HAZ or the sum of all delay times. By comparison of the beam sources, it can be seen that the aspect ratio between laser beam diameter and laminate thickness must be optimized. In addition to the optimization of the delay times, it is also necessary to adjust the laser power and the scanning speed from exposure to exposure.

This article presents an ultralow-profile and lightweight Ku-band transmit phased array with 256 dual-polarized antenna elements for SATCOM on-the-move (SOTM) terminals. The antennas are placed in a square grid with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> /2 spacing at 14 GHz. At normal incidence, the phased array results in a measured effective isotropic radiated power (EIRP) of 64.5 and 66.5 dBm at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm {1~dB}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm {sat}}$ </tex-math></inline-formula> , respectively, per polarization. The measured patterns, in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$ </tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> -planes, show almost ideal patterns with a wide scanning range of ±60°, a 3-dB instantaneous bandwidth of 13.0–14.6 GHz, and a cross-polarization isolation of 27 dB up to ±45° and 23 dB at ±60° scan angles. In the circular polarization mode, the measured axial ratio (AR) is <1.1 dB at 14–14.5 GHz. The phased array is also capable of synthesizing deep nulls (−30 to −40 dB) over a wide range of angles, thereby reducing unintended radiation to geostationary orbit (GEO) satellites. Transmit noise analysis is presented and shows that the array signal-to-noise ratio (SNR) is dominated by the block upconverter (BUC) and not by the beamformers. An error vector magnitude (EVM) of 2.8%–3.5% was achieved over a wide scan range for QPSK, 8-PSK, and 16-PSK waveforms with 100-MHz bandwidth. The array near-ideal performance, compact size, low profile with 3.5-mm thickness, and ultralightweight of 212 g make it ideal for affordable Ku-band SATCOM terminals.

Design of a compact multilayer circularly polarized phased array transmit antenna system for satellite applications

The planar quasi-Yagi antenna we developed recently promises the realization of 2D active phased arrays with optimal array bandwidth and scanning range. This paper addresses the issue of mutual coupling between quasi-Yagi elements to ensure scan-blindness-free construction of a 2D array. While the coupling between two /spl lambda//sub 0//2-spaced quasi-Yagi elements is reasonably low (-25 dB in E plane, -20 dB in H plane) in its original design, it is found by both simulation and measurement that the coupling levels can be pushed to below -30 dB in both planes by cutting a slit in the dielectric in the E plane and adding a metal fence in the H plane, making it possible to realize full 2D phased arrays which are free of scan blindness over a wide range of frequency and scan angle.

Production home building possesses characteristics similar to manufacturing processes (such as the construction of more or less similar houses repeatedly and a growing demand for mass customization of homes). Home builders generally utilize critical path method scheduling, cost estimating, and earned value analysis management tools to manage their production process. However, these tools are not responsive to many undesirable situations that arise during the production process, such as increasing cycle time and increasing amounts of work in process, both of which increase capital investment, decrease company financial performance, and slow product delivery to customers. This study examines relationships between cycle time, work in process, system throughput, new construction starts, and production system capacity using building permit data for new single family homes in Chandler, Arizona. The applicability of Little's Law, a basic equation used in factory production system design, to a residential production system is examined. This study shows a definite, predictable relationship between cycle time, work in process, and production system throughput. This study provides for further study of production system characteristics that have historically not been considered in construction management models, with the expectation of developing a new construction management system that will account for more of the characteristics of construction production systems that affect project performance and company financial performance.

As required CD (critical dimension) measuring accuracy is tighter, it is necessary to enhance the repeatability of CD-SEM on photo-mask, by optimizing charge up, scan speed, beam size, acceleration, current and temperature control. CD-SEM shows sparkle noise which degrades the image of CD-SEM. And defocus is also getting the source of worse gauge R&R. We evaluated the effect of defocus and noise on CD repeatability by extracting CD from gradient value of image after anisotropic nonlinear diffusion filtering on SEM image. As SEM image is measured after averaging the intensity of image on range of interest (ROI) to remove scan noise, anisotropic nonlinear diffusion (AND) which has different diffusivity according to direction, is efficient tool to get smooth pattern without averaging. This smoothing technique is effective in measuring isolated pattern on mask which is difficult to measure around corner. Some simple CD measuring algorithms are available to get better CD repeatability. Using the maximum intensity and gradient of image, we were able to measure CD on various shaped patterns with enhanced repeatability.

3D LIDARs (Light Detection and Ranging) with 1.5μm nanosecond pulse lasers have been increasingly used in different applications. The main reason for their popularity is that these LIDARs have high performance while at the same time can be made eye-safe. Because the laser hazard effect on eyes or skin at this wavelength region (<1.4μm) is mainly from the thermal effect accumulated from many individual pulses over a period of seconds, scanning can effectively reduce the laser beam hazard effect from the LIDARs. Neptec LIDARs have been used in docking to the International Space Station, military helicopter landing and industrial mining applications. We have incorporated the laser safety requirements in the LIDAR design and conducted laser safety analysis for different operational scenarios. While 1.5μm is normally said to be the eye-safe wavelength, in reality a high performance 3D LIDAR needs high pulse energy, small beam size and high pulse repetition frequency (PRF) to achieve long range, high resolution and high density images. The resulting radiant exposure of its stationary beam could be many times higher than the limit for a Class 1 laser device. Without carefully choosing laser and scanning parameters, including field-of-view, scan speed and pattern, a scanning LIDAR can’t be eye- or skin-safe based only on its wavelength. This paper discusses the laser safety considerations in the design of eye-safe scanning LIDARs, including laser pulse energy, PRF, beam size and scanning parameters in two basic designs of scanning mechanisms, i.e. galvanometer based scanner and Risley prism based scanner. The laser safety is discussed in terms of device classification, nominal ocular hazard distance (NOHD) and safety glasses optical density (OD).

A digital adaptive optics line-scanning confocal imaging (DAOLCI) system is proposed by applying digital holographic adaptive optics to a digital form of line-scanning confocal imaging system. In DAOLCI, each line scan is recorded by a digital hologram, which allows access to the complex optical field from one slice of the sample through digital holography. This complex optical field contains both the information of one slice of the sample and the optical aberration of the system, thus allowing us to compensate for the effect of the optical aberration, which can be sensed by a complex guide star hologram. After numerical aberration compensation, the corrected optical fields of a sequence of line scans are stitched into the final corrected confocal image. In DAOLCI, a numerical slit is applied to realize the confocality at the sensor end. The width of this slit can be adjusted to control the image contrast and speckle noise for scattering samples. DAOLCI dispenses with the hardware pieces, such as Shack–Hartmann wavefront sensor and deformable mirror, and the closed-loop feedbacks adopted in the conventional adaptive optics confocal imaging system, thus reducing the optomechanical complexity and cost. Numerical simulations and proof-of-principle experiments are presented that demonstrate the feasibility of this idea.

This paper presents microelectromechanical system micromirrors with sidewall electrodes applied for use as a Confocal MACROscope for biomedical imaging. The MACROscope is a fluorescence and brightfield confocal laser scanning microscope with a very large field of view. In this paper, a microelectromechanical system mirror with sidewall electrodes replaces the galvo-scanner and XYZ-stage to improve the confocal MACROscope design and obtain an image. Two micromirror-based optical configurations are developed and tested to optimize the optical design through scanning angle, field of view and numerical aperture improvement. Meanwhile, the scanning frequency and control waveform of the micromirror are tested. Analysing the scan frequency and waveform becomes a key factor to optimize the micromirror-based confocal MACROscope. When the micromirror is integrated into the MACROscope and works at 40 Hz, the micromirror with open-loop control possesses good repeatability, so that the synchronization among the scanner, XYZ-stage and image acquisition can be realized. A laser scanning microscope system based on the micromirror with 2 μm width torsion bars was built and a 2D image was obtained as well. This work forms the experimental basis for building a practical confocal MACROscope.

Atomic force microscope (AFM) is a promising tool in micro and nano size objects researches. Contact mode AFM has advantages comparing to non-contact modes: the scanning speed is higher, and atomic resolution can be achieved. The main limiting factor in contact mode AFM is scanning speed. At high scanning speed the ‘loss of contact’ phenomenon occurs, and probe in this case cannot follow the surface. In order to ensure a constant interaction force (stable contact) between the probe and scanned surface, the additional force created by air flow was applied. Proposed method is based on the idea to apply additional controllable nonlinear force on the upper surface of the AFM cantilever, which will help to keep the probe in contact with sample surface. It was found that dynamic characteristics of various AFM sensor cantilevers can be controlled using proposed method. It has been determined that the use of aerodynamic force has the greatest influence on the scanning results deviation from the real sample in the horizontal direction then scanner z axis goes down. With a compressed air pressure of 7 kPa and a scanning speed 847.6 μm/s, this deviation decreases by 20% comparing to the case when compressed air flow is not used.

In this paper we discuss the performance of low order adaptive optics (AO) systems. We present improved calculations of Strehl ratio achievable at various D/r<SUB>o</SUB> ratios for AO systems up to 7<SUP>th</SUP> order. Additionally we present calculations concerning the throughput of low order AO systems used in conjunction with spectrometers. We then show the results of a detailed simulation of the expected interaction of the University of Hawaii prototype AO system with spectrometers through the V,I,J,H,K optical bands. This simulation shows that AO spectroscopy performance should always be acceptable in the near IR (J,H,K), and often in the visible (V,I). We show the results of our initial efforts at deconvolving the AO PSF. These results indicate that deconvolution is likely to be quite widely applicable to AO images. Finally we discuss how it might be possible to extend the applicability and accuracy of deconvolution using the AO drive and wavefront error signals. The following results are for on-axis system, the effects of atmospheric anisoplanitism have not been addressed in this paper.

A method by which intensity profile and diameter of focussed CO2 laser beam are determined from the evaporated shape in PMMA (polymethyl methacrylate) has been developed. This method utilizes the fact that PMMA is sublimated by intenselaser beam with negligible thermal conduction and reflection losses. Two essential thermal constants of PMMA for estimating the intensity of the laser beam are determined; energy for evaporation H=3000 J/cm3, and threshold energy for evaporation G=6 J/cm2. It is shown that thus estimated profile is in good agreement with the profile determined by the probe techniques, and that the axi-symmetrical intensity distribution is determined from the deconvolution by Harker method. The optimum scanning speed, and tolerable scanning speed range in this technique are given as a function of power and spot size of laser beam. It is also shown that arbitrary intensity distributions can be determined by using PMMA.

At Penn State, two new instrument component technologies, namely silicon gratings and gaussian-shaped pupil masks, have been developed and are ready for producing high quality components for all three NGST IR instruments. Fabrication of silicon grisms with sizes up to 2 inches in dimension has become a routine process at Penn State thanks to newly developed techniques in chemical etching, lithography, and post-processing. The newly etched silicon grisms have a typical rms surface roughness of ~ 9 nm with the lowest of 0.9 nm, significantly lower than our previous ones (~ 20-30 nm) and have ~ 0.035 wave wavefront distortion at 0.6328 &#956;m, indicating diffraction-limited performance in the entire infrared wavelengths (1.2 -10 &#956;m) where silicon has excellent transmission. These processes have also significantly eliminated visible defects due to grating mask break during chemical etching. For the best grisms, we have less than 1 defect per cm². The measured total integrated scatter is less than 1% at 0.6238 mm, indicating similar or lower scatter in the IR when grisms are operated in transmission. Silicon grisms and silicon immersion gratings will both boost spectral resolving power by more than 3 times for NGST near-IR MOS and mid-IR camera and spectrograph without pushing current instrument design. The higher dispersed spectra can be selected either by a filter or a low resolution grism cross-disperser. Our current grating techniques allow us to make gratings with a groove period from a few microns to more than 100 microns. For the first order grism, the theoretical grating efficiency is beyond 80% with a single layer of AR coating. The immersion gratings will have similar grating efficiency. Based on our previous measurements of a silicon echelle grism, this kind of grism can provide ~ 60% efficiency when they are operated in high orders. We have also developed Gaussian-shaped pupil masks for high contrast imaging with the NGST IR cameras. Depending on its final mirror configuration, this kind of mask can offer 10^-6 contrast imaging as close as 5 lambda/D to a bright point source. The advantage of using this mask instead of a conventional graded Lyot coronagraph is that it is much easier to implement by simply inserting it at a pupil location to reach deep null. Therefore, the observing efficiency can be significantly improved. A prototype of this kind of mask has been tested at the Mt. Wilson 100inch telescope with adaptive optics and demonstrates 10^-3-10^-4 contrast at ~ 5 &#955;/D at the initial observations. The contrast level is comparable to an IR coronagraph in the same IR instrument, but is about one order of magnitude worse than the scattered light levels caused by the mirror surface. We have also studied other mask coronagraph designs for high contrast imaging. The hybrid and band-limited designs show great promise for further improving image contrast. The NGST IR cameras with new coronagraph designs will allow high contrast imaging for extra-solar planets and substellar companions around nearby stars.