No abstract

For several years Baird-Atomic has been involved in the design, construction and testing of a breadboard oil-in-water content monitor for use with bilge and ballast wastewater. This work has been supported by the Coast Guard, the Navy, and Baird-Atomic. The basis of the monitor is the luminescence (fluorescence) of the aromatics present in all petroleum oils. The advantages of this approach include high sensitivity, real time output, fast response time, insensitivity to many interferences, and reduced sensitivity to particulates. The chief problem is the unequal luminescence response of oils. The general approach involves simultaneous excitation and monitoring at a number of wavelengths, selected to give a net response almost independent of oil type. A first approach involved a novel optical scheme involving two polychromators. The first provided excitation at different wave-lengths along a flowing sample. The second, operated in reverse, summed selected emission from different portions of the sample. This approach, called “synchronous scan,” while successful, was supplanted by a more general approach which utilized the total luminescence of the sample: i.e., all possible emissions resulting from all possible excitation. In this case, the second polychromator was used to disperse emission from the sample at right angles to the excitation dispersion. The total luminescence was then imaged at the exit plane of the second monochromator where a computer-designed mask selected those spectral regions equalizing response of various oil types. Results of tests are discussed, together with progress on a shipboard prototype.

Recent studies show that white light, or broadband, metrology systems continue to be used as the "work-horse" method for measuring features at 1.0 micron and below in production manufacturing environments. With the advances in the area of broadband optical metrology using sophisticated digital -image enhancement techniques, production quality measurements are now possible down to 0.5 micron and below. The purpose of this paper is to show substantial evidence that reliable, fully automatic, high speed, dynamic mode measurements can be made using optical methods on substrates in the range of 0.5 to 0.3 microns, with excellent repeatability and correlation to a SEM reference.

Luminescence methods have been established as very promising for continuous oil -in -water monitoring because of their high sensitivity and relative immunity to particulate backgrounds.The greatest problem with luminescence has been the highly variable response of different oil types. Previous studies have shown that it is possible to roughly equalize response to many oils by weighted summing of multiple emissions resulting from multiple excitations.The use of a large number of filter pairs or mechanically scanned monochromators is undesirable both because instrument response time is too long for a continuous monitor, and because the mechanical scanning of critical optical components does not lend itself to incorporation in a rugged shipboard instrument. This paper discusses an optical summing and weighting technique which retains the advantages of luminescence methods, retains a short response time, but eliminates mechanical scanning of wavelengths. The operation of the optical breadboard is discussed in terms of the oil -in -water problem.