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We present a free space optical communication system that uses electrostatically modulated microelectromechanical systems (MEMS) structures coupled with a glass total internal reflection-type corner cube retroreflector (CCR) as a nonemitting data transmitter. MEMS structures consists of an array of light scattering membranes fabricated on silicon-on-insulator wafer. The MEMS structures are bonded to a glass lid with a transparent conductive indium tin oxide film using flip chip bonding. The chip is aligned and bonded to a passive glass CCR using an ultraviolet (UV) epoxy with an accuracy of 20–30 arc-s. The MEMS structures can be modulated either toward or away from the bonded glass, thus disrupting evanescent energy delivered from a probing laser beam. Retroreflective optical communication over 300 m was achieved using an interrogating 635-nm laser. [2014-0301]

Near-field evanescent wave coupling of various subwavelength grating pairs, using a 1.55 μm infrared semiconductor laser has been demonstrated for use as an optical MEMS sensor. Subwavelength grating pairs were fabricated on both glass and silicon substrates. When coupled together the effective grating period is not subwavelength and can exhibit several diffraction orders. The 1.55 μm infrared source was incident on the coupled pairs and the first-order output intensity was recorded and compared with the output intensity from simulated results. This demonstrated evanescent wave coupling concept can be applied to MEMS systems with nanometer gap separations (e.g., pressure sensors, biosensors, and accelerometers) to allow for subnanometer displacement detection.

A new approach to etch structures with vertical sidewalls in Si is presented. This process reduces the loading effect in Deep Reactive Ion Etching (DRIE) and maintains uniform etch profile and etch rate through out the wafer. Rectangular areas were patterned under the regions to be removed. Uniform width channels encompassing these rectangular patterns were then subjected to long DRIE. These uniform width narrow channels maintain uniform etch rates while patterning structures with various fill factors on the same wafer. Average side wall angles of 89.8{degree sign} were obtained with just 0.3{degree sign} variation across the 4 Si wafer. The process showed resistance to slight variations in DRIE parameters with negligible effect on the sidewall profile. The etched vertical mirrors are used to assemble a Corner Cube Retroreflector.

A scheme for creating metal-coated vertical mirrors in silicon, along with an integrated transparent package lid for assembling, packaging, and testing microelectromechanical systems (MEMS) devices is presented. Deep reaction ion etching (DRIE) method described here reduces the loading effect and maintains a uniform etch rate resulting in highly vertical structures. A novel self-masking lithography and liftoff process was developed to ensure that the vertical mirrors undergo uniform metallization while leaving a transparent window for optical probing. Front side of a Si wafer was shallow-etched using DRIE to define an eventual optical window. This surface was then anodically bonded to a Pyrex wafer. Backside Si was then patterned to define thin channels around the optical window. These channels were vertically etched using DRIE, after which the unattached portions of the window region were removed. Negative photoresist was spun on the remaining vertical structures and the stack was exposed from the Pyrex side using Si structures as a self-mask. Subsequent metal sputtering and liftoff results in the metallized top and mirror sidewalls while leaving a clear window. These integrated mirrors and lids are then bonded to the active MEMS mirrors. Various processes and results are illustrated with an example of packaged corner cube retroreflectors (CCRs)

In marine biology study, it is important to investigate the distribution of plankton organisms. Because of the overwhelming data size, automatic processing of the large amount of image data collected by underwater image recorders becomes inevitable. However, due to the fragmentation and the large within-class variations of binary plankton images, it is difficult to extract reliable shape features. In this paper, we propose several new shape descriptors and use a normalized multilevel dominant eigenvector estimation method to select a best feature set for binary plankton image classification. We achieve more than 91% classification accuracy in experiments on more than 3000 images

Zooplankton and suspended particles were sampled in the upper 100 m of the Gulf of Mexico with the High Resolution Sampler. This towed-platform can concurrently sample zooplankton with plankton nets, an Optical Plankton Counter (OPC) and the Shadowed Image Particle Profiling and Evaluation Recorder (SIPPER), a zooplankton imaging system. This allowed for direct comparison of mesozooplankton abundance, biomass, taxonomic composition and size distributions between simultaneously collected net samples, OPC data, and digital imagery. While the net data were numerically and taxonomically similar to that of previous studies in the region, analysis of the SIPPER imagery revealed that nets significantly underestimated larvacean, doliolid, protoctist and cnidarian/ctenophore abundance by 300%, 379%, 522% and 1200%, respectively. The inefficiency of the nets in sampling the fragile and gelatinous zooplankton groups led to a dry-weight biomass estimate less than half that of the SIPPER total and suggests that this component of the zooplankton assemblage is more important than previously determined for this region. Additionally, using the SIPPER data we determined that more than 29% of all mesozooplankton-sized particles occurred within 4 mm of another particle and therefore would not be separately counted by the OPC. This suggests that coincident counting is a major problem for the OPC even at the low zooplankton abundances encountered in low latitude oligotrophic systems like the Gulf. Furthermore, we found that the colonial cyanobacterium Trichodesmium was the most abundant recognizable organism in the SIPPER dataset, while it was difficult to quantify with the nets. For these reasons, the traditional method of using net samples to ground truth OPC data would not be adequate in describing the particle assemblage described here. Consequently we suggest that in situ imaging sensors be included in any comprehensive study of mesozooplankton.

We discuss an in situ marine imaging system based on high-speed digital line scan cameras for collection of a continuous picture of microscopic marine particles ranging in size from 200 /spl mu/m to several centimeters. The system is built to operate on a 53-cm-diameter autonomous underwater vehicle or a tethered platform. The digital imaging system provides a continuous record of all particles passing through a symmetric 96/spl times/96 mm sampling tube and provides views from two orthogonal directions. Data are compressed using a lossless encoding technique and stored onto a disk drive. Over 50 h of continuous imaging is possible using the system. Data are suitable for studies requiring sizing, identification, quantification, and spatial recording of semi-transparent and opaque particles. This paper summarizes the mechanical, optical, and data processing design of this instrument and discusses recent improvements. We also present images and quantitative results from recent deployments in the Gulf of Mexico.

Irrigation in hot, humid areas is particularly challenging because irrigation must be applied in a timely manner to prevent yield loss due to crop water stress, yet avoid flooding should a rain event follow irrigation. Moreover, it is difficult to detect the onset of crop water stress under environmental conditions that limit evaporative cooling. The goal of this project is to develop reliable, easy to use irrigation scheduling tools that integrate crop monitoring and accurate weather predictions to improve the timing and application of irrigation in humid, high rainfall environments for better water management. The irrigation decision support system is based on calculations of crop water use from weather data collected from weather stations throughout Mississippi using crop coefficients developed from weighing lysimeters and other sources. A water balance approach is used to indicate when supplemental irrigation is needed based on available water and crop water use. This is integrated with other publicly available, spatially registered farm and soil databases to develop specific irrigation scheduling recommendations. A web-based interface is being developed to deliver the irrigation decision support system to producers through an easy to use and readily accessible format. Training materials will be developed and presented to producers through on-site training and other standard Extension mechanisms.

A technique was developed to couple near-field evanescent waves into observable diffraction orders in the far-field region. This investigation was of two gratings that have a 1.0 microm grating period in glass and 1.1 microm in silicon and are individually subwavelength, but when coupled together yield an 11.0 microm effective grating period. This effective grating period is not subwavelength to a 1.550 microm infrared incident source and exhibits higher diffraction orders. Optimum evanescent wave coupling efficiency was simulated by varying the grating thickness and the grating separation between the subwavelength gratings. This proposed evanescent wave coupling concept is being investigated for use in a bulk silicon MEMS accelerometer.

A small form factor microsensor system with optical MEMS devices is discussed in this paper. The key components in the microsensor system include a temperature and humidity sensor for environmental monitoring, a microprocessor for signal processing, and an optical MEMS device (active corner cube retroreflector or CCR) for remote free space optical communication. A flexible circuit design and a folded packaging scheme have been utilized to minimize the overall form factor. Flat, flexible polymer batteries are incorporated to minimize the vertical profile to a few millimeters. The entire fully packaged sensor system is about 30mmx30mmx6 mm. MEMS design of the CCR, fabrication, hermetic packaging of CCR, flexible circuit design and fabrication, flip chip bonding of die form microprocessor, and a battery replacement scheme for extended operation lifetime are crucial elements for the development of a real product for the microsensor system. Optical MEMS CCR is a torsion mirror design and was fabricated using surface micromachining with Si 3 N 4 as a structural layer. A finite element analysis (FEA) model was developed to optimize design and performance of the MEMS structures. The sensor system has a miniature mechanical switch for local actuation and an optical switch for remote actuation. The applications of such a microsensor system include both tracking, tagging, locating (TTL) and remote sensing.

Miniaturization of laboratory sensors has been enabled by continued evolution of technology. Field portable systems are often desired, because they reduce sample handling, provide rapid feedback capability, and enhance convenience. Fieldable sensor systems should include a method for initiating the analysis, storing and displaying the results, while consuming minimal power and being compact and portable. Low cost will allow widespread usage of these systems. In this paper, we discuss a reconfigurable Personal Data Assistant (PDA) based control and data collection system for use with miniature sensors. The system is based on the Handspring visor PDA and a custom designed motherboard, which connects directly to the PDA microprocessor. The PDA provides a convenient and low cost graphical user interface, moderate processing capability, and integrated battery power. The low power motherboard provides the voltage levels, data collection, and input/output (I/O) capabilities required by many MEMS and miniature sensors. These capabilities are relayed to connectors, where an application specific daughterboard is attached. In this paper, two applications are demonstrated. First, a handheld nucleic acid sequence-based amplification (NASBA) detection sensor consisting of a heated and optical fluorescence detection system is discussed. Second, an electrostatically actuated MEMS micro mirror controller is realized.

We present a system to recognize underwater plankton images from the shadow image particle profiling evaluation recorder (SIPPER). The challenge of the SIPPER image set is that many images do not have clear contours. To address that, shape features that do not heavily depend on contour information were developed. A soft margin support vector machine (SVM) was used as the classifier. We developed a way to assign probability after multiclass SVM classification. Our approach achieved approximately 90% accuracy on a collection of plankton images. On another larger image set containing manually unidentifiable particles, it also provided 75.6% overall accuracy. The proposed approach was statistically significantly more accurate on the two data sets than a C4.5 decision tree and a cascade correlation neural network. The single SVM significantly outperformed ensembles of decision trees created by bagging and random forests on the smaller data set and was slightly better on the other data set. The 15-feature subset produced by our feature selection approach provided slightly better accuracy than using all 29 features. Our probability model gave us a reasonable rejection curve on the larger data set.

The goal of this project is to develop a broadly-capable software package, to automatically classify digital images of zooplankton. The software is being developed initially for classification of images from the SIPPER linescan imaging instrument, but will also be able to process images from imaging systems that produce high quality digital image. Towards this end, the software is being created to include both training and multi-stage classification portions. The input is digital images in standard computer format. The output is an Internet-addressable classified particle database, including pertinent particle hydrographic information and sorted images. The project has application in rapid classification of microscopic marine particles, which have an effect on the optical properties and long-term variation in the local and global water column.

The long term goal is development and utilization of a suite of high-resolution, linescan-camera based imaging systems to investigate the distribution and composition of plankton and suspended particles in the marine environment. The system is designed with wide dynamic range and will ultimately be used for high speed, high resolution characterization of water column particle fields in high, medium and low latitudes. Such a system will have broad application to areas of defense and environmental interests such as ecological modeling efforts, Autonomous Ocean Sampling Networks (AOSN), and ground-truthing of satellite data.

The long term goal is development and utilization of a comprehensive (broadly capable) marine particle analysis system. The system is designed with wide dynamic range, thus, it will ultimately be used for high speed, high resolution characterization of water column particle fields in high, medium and low latitudes. As part of a broader goal this project continues advancement of the AOSN concept through development of both towed platforms and autonomous underwater vehicles.

The number of photonic devices based on integrated-optic waveguides with domain-inverted regions are currently experiencing rapid expansion. Implementation of domain reversals in guided-wave structures brings about an opportunity to significantly increase device efficiency as well as to simplify the structure. Domain inversion has proven beneficial both for nonlinear devices and electro- optic modulators. It should be noted in this regard that while the use of domain reversals for nonlinear interactions has been studied extensively, little information on the characteristics of electro-optic devices with such domain- inverted regions is available in the literature. This paper addresses the latter issue by studying the performance of an integrated-optic Mach-Zehnder interferometer modulator with electric-field poled domain-inverted sections. With this device, both the realization of waveguide sections with opposing values of the electro-optic coefficient (r33), and the measurement of the value of r33 have been demonstrated experimentally.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In our proposed method of near field optical microscopy, the near field is probed by a vibrating solid stylus and the radiation downstream from the stylus is measured. The underlying idea is that at the sharp stylus tip or edge, evanescent fields are converted into traveling waves which are subsequently detected conventionally. The area of perturbation, i.e. the resolution, is determined by the vibration of the stylus and labeled by the frequency or frequencies of vibration.

Recently we reported results of 1-D beam profiling with a scanning, vibrating knife edge and its implications for near-field optical microscopy.1 We now report on the implementation of this idea in two dimensions. A knife edge corner is made to vibrate in two orthogonal directions with frequencies of 1000 Hz and 1100 Hz and amplitudes w1 and w2, respectively. A photodiode downstream from the knife edge detects the mixing signal at 100 Hz and records its amplitude, while the vibrating knife edge corner scans the optical field. A gray scale recording of this amplitude yields an image of the field with (electronically variable) resolution w1 × w2. In this paper we show images achieved with this mixing technique and with another more sensitive one that uses 2-D scanning with a 1-D vibrating knife edge, combined with computer postprocessing.

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