Optical Data Processing Techniques Research Articles

Plasmon extinguishment by bandedge shift identified as a second-order spectroscopic differentiation

Abstract Optical excitation of metallic nanostructures induces strong intraband transitions, leaving transient depletion below the Fermi level, which allows transient interband transition to this depletion band. This is equivalent to the lowering of the threshold for interband transitions and pushes the plasmonic band to the red. As a result, localized surface plasmon resonance (LSPR) is “extinguished” or “quenched” around the bandedge, in contrast, the interband optical absorption becomes enhanced and redshifted. The corresponding transient absorption (TA) signals have equal lifetimes and opposite signs. Moreover, the TA spectrum is found to be a second-order differential of the steady-state optical extinction spectrum over the studied band. This is a commonly existing mechanism for metallic nanostructures and verified with gold in this work. Such a discovery is completely different from the optical-excitation-induced redshift of LSPR through enhanced electronic scattering and is important for understanding the ultrafast spectroscopic response of plasmonic nanostructures with clear photophysical insights, supplying solid basis for exploring optical logic device and optical data processing techniques.

Inspection of Integrated Circuit Photomasks using Optical Data Processing Techniques

AbstractThe application of optical signal processing techniques for the inspection of integrated circuit photomasks, could prove to be a fast and cheap means of photomask inspection. In this paper we discuss two possible optical inspection techniques and their suitability for use as a practical inspection tool.

Parallax Measurement Using Coherent Optics

We have used coherent optical data processing techniques to measure parallax in stereo aerial photographs. This is accomplished by cross-correlating one aerial photograph with a small region in another photograph. Experiments were performed on a breadboard system which was used both for making matched spatial filters (Fourier transform holograms) and for measuring parallax. This system has a 100-mm x 100-mm useful aperture which is scanned by a telecentric beam steering device controlled by a minicomputer. Parallax data obtained from this system proved to be in good agreement with similar data produced by an operational electronic stereo-compilation system. These experimental results and certain inherent advantages discussed in the paper lead us to conclude that coherent optical techniques may provide the basis for a fast, cost-effective automatic stereo-compilation system.

OPTICAL DATA PROCESSING AND PROJECTED APPLICATIONS OF THE ERTS‐1 IMAGERY COVERING THE 1973 MISSISSIPPI RIVER VALLEY FLOODS1

ABSTRACT. Flooding along the Mississippi River and some of its tributaries was detected by the multispectral scanner (MSS) on the Earth Resources Technology Satellite (ERTS‐1) on at least three orbits during the spring of 1973. The ERTS data provided the first opportunity for mapping the regional extent of flooding at the time of the imagery. Special optical data processing techniques were used to produce a variety of multispectral color composites enhancing flood‐plain details. One of these, a 2‐color composite of near infrared bands 6 and 7, was enlarged and registered to 1:250,000‐scale topographic maps and used as the basis for preparation of flood image maps. Two specially filtered 3‐color composites of MSS bands 5, 6, and 7 and 4, 5, and 7 were prepared to aid in the interpretation of the data. The extent of the flooding was vividly depicted on a single image by 2‐color temporal composites produced on the additive‐color viewer using band 7 flood data superimposed on pre‐flood band 7 images. On May 24, when the floodwaters at St. Louis receded to bankfull stage, imagery was again obtained by ERTS. Analysis of temporal data composites of the pre‐flood and post‐flood band 7 images indicate that changes in surface reflectance characteristics caused by the flooding can be delineated, thus making it possible to map the overall area flooded without the necessity of a real‐time system to track and image the peak flood waves. Regional planning and disaster relief agencies such as the Corps of Engineers, Office of Emergency Preparedness, Soil Conservation Service, interstate river basin commissions and state agencies, as well as private lending and insurance institutions, have indicated strong potential applications for ERTS image‐maps of flood‐prone areas.

Additional optical data processing techniques for surface roughness studies

Three methods for determining the statistics of a surface's roughness are proposed. All three use some variation of the phase contrast method, and all appear to have advantages over a recently suggested method.

A Review of Optical Data-processing Techniques

Various optical data-processing techniques are reviewed in this article. Both coherent and incoherent optical systems are considered. Coherent systems are described in terms of spatial filtering concepts and two principal methods for implementing a general linear integral operator are discussed: one using space-domain reference function masks and one using frequency-domain spatial filters. Incoherent systems are described in terms of geometrical optics.

Use of optical data processing techniques for surface roughness studies

A report is given of preliminary work on a process of studying surface roughness of materials. The technique analyzes the statistics of the Fourier components of the surface roughness and uses conventional optical data processing procedures.

An Optical Range-Gated Filtering Technique for Mti Radar

Moving targets submerged in clutter can be more readily detected by range-gated filtering techniques. Range-gated filtering is a two-dimensional process in which target Doppler frequency and range are desired output quantities. Optical data processing techniques are inherently multidimentsional. An experimental system using a He-Ne laser source and film transparencies representing radar echoes gave output patterns in agreement with theoretical predictions. Major advantages of an optical filter are simplicity and relatively small size.