This PDF file contains the editorial “Editorial: The Logical Place to Publish” for OE Vol. 30 Issue 09

A common method of estimating the attenuation capabilities of military smokes/obscurants is to use a band-averaged mass extinction coefficient with concentration length values in the Beer-Bouguer transmission law. This approach ignores the effects of source spectra, sensor response, and normal atmospheric attenuation on broadband transmittance characteristics, which can significantly affect broadband transmittance. The differences that can occur in predicting relative transmittance as a function of concentration length by using band-averaged mass extinction coefficients as opposed to more properly computing the bandaveraged transmittance are discussed in this paper. Two examples are provided to illustrate the differences in results. The first example considers 3- to 5-μm and 8- to 14-μm band transmission through natural fogs. The second example considers 3- to 5-μm and 8-to 12-μm transmission through phosphorus-derived smoke (a common military obscurant) produced at 17% and at 90% relative humidity. Major differences are found in the values of concentration lengths predicted by the two methods when the transmittance relative to an unobscured atmosphere falls below about 20%. These results can affect conclusions concerning the detection of targets in smoke screens, smoke concentration lengths required to obscure a target, and radiative transport through polluted atmospheres.

Light scattering and light absorption of hydrocarbon fuels was utilized to gain information about the presence and the space-time distribution of liquid and vaporized fuel inside the combustion chambers of optically accessed research engines. The design and application of the experimental method is described. Semiquantitative results about the mixing of fuel with in-cylinder air are presented. The conclusions drawn therefrom yield time scales for diesel spray penetration, evaporation, and fuelair mixture formation. In a gasoline engine, different modes of fuel air mixing are identified.

Statistical properties of plastically roughened metallic surfaces are studied together with the relation between the angular distribution of the reflected-plus-scattered intensity from such a surface and the plastic deformation it has experienced. The height probability density distribution ofthe plastically roughened surfaces is shown to be Gaussian. The surface autocorrelation function is neither Gaussian nor exponential, even though the former fits the experimental data better. The combination of a scalar scattering theory and the plasticity-induced surface roughening empirical relations yields some new expressions. These expressions relate scattered light with plastic deformation for surfaces with Gaussian or exponential autocorrelation. The applicability, convergence, and limitation of the thus obtained expressions are also studied. A theoretical-numerical analysis provides background to some existing strain measuring methods, such as the maximum intensity, half width, and correlation coefficients. The present approach is verified favorably by some experiments on aluminum alloys and is in support of the experimental results in literature.

A reflecting off-axis paraboloid is frequently used either to collimate the light from a point source or to concentrate in a point the light from a collimated beam. Because these paraboloids are expensive and difficult to manufacture, a spherical mirror is frequently used instead. The aberrations arising with this substitution are analyzed and evaluated.

Two electronic exposure systems employing active-matrix addressed liquid crystal light modulators are described for printing on lowsensitivity photographic materials such as the new 3M Dry Silver Color and Mead Cycolor™ papers. The feasibility of using a liquid crystal light modulator to expose these new materials was first demonstrated on a system employing simple projection optics. The image quality, printing speed, and complexity of projection type systems make them poor candidates for low-cost video printers. A new Multiline Multilevel Scanned Printing System, which is especially well suited to printing with liquidcrystal light modulators, is described. This is a large-aperture digital technique using an incandescent light source. It can produce a near-continuous-tone color print on photographic materials in a single pass below the light modulator. The system is intrinsically insensitive to isolated defects in the modulator and can also easily accommodate corrections for single pixel and column defects. The system has been used to make prints on a variety of photographic materials varying by over three orders of magnitude in sensitivity. A figure of merit is introduced that can be used as a starting point when one is comparing various exposure schemes.

An electro-optical system for the detection and quantitative measurements of surface or subsurface defects is presented; it is based on a holographic contouring technique and digital image processing for an automatic analysis of fringe patterns. Several approaches have been followed on models, so that the defects can be unambiguously detected and possibly quantitatively analyzed. Some examples of applications in deterioration investigations of ancient artworks are reported.

In many holographic recording regimes polarization and symmetry pose conflicting requirements. The author takes another look at this problem to seek helpful guidance. Several important regimes of recording are discussed and levels of information and fog are calculated. Overall, the holographic method is seen to be often less than satisfactory and the author concludes that very great care is necessary to elevate the fringe contrast from a lowly level imposed by experimental inadequacy to still potentially low theoretical limits imposed by polarization and symmetry.

A divergent laser beam was used to record holograms of moving iron fibers with submicron diameter (0.5 μm) and high velocity (125 m/s). Analysis based on geometric optics is used to derive the magnification factors for recording and reconstruction. Experimental results consisting of single-shot holograms of fast-moving fibers are presented. The divergent laser beam technique can be used for dynamic measure of particle size and fiber orientation distribution.

Holography concepts have been evaluated as nonintrusive tools that can measure earthquake effects and earthquake resistance of structures. The methods offer potential toward the application of advanced design techniques in civil and earthquake engineering. Our study produced methods to holographically monitor large, distant surfaces, which could be used to inspect buildings, bridges, storage tanks, or dams during interaction with geological or meteorological forces. This work included the successful demonstration of holography in obtaining modal information of a 3.4-m-tall liquid storage tank at a distance of 20 m.

An analysis of the properties of the centroid method for subpixel accuracy image feature location is presented. This method is free of systematic error if the maximum spatial frequency of the image incident on the image sensor is less than the sensor's sampling frequency. This can be achieved by using a lens aperture setting such that the modulation transfer function cut-off frequency due to diffraction is appropriately small. Both simulation and experimental tests of this prediction are presented for the case of the location of the center lines of the images of projected light stripes in a triangulation-based three-dimensional shape measurement system.

A new technique is proposed to reconstruct an astronomical image using phase retrieval from exponential filtered and unfiltered images based on the Fourier series expansion method. The amplitude of the Fourier transform of the filtered image is a mixture of the information of the amplitude and phase in the Fourier space corresponding to the unfiltered image. Therefore, the phase information can be derived from the Fourier modulus ofthe filtered image based on the Fourier decomposition method described. This method is applied to stellar speckle interferometry and the successful reconstruction of a double star image is obtained.

A cost-effective method of synthesizing images of arbitrary complexity is described that combines high-resolution depth maps of scale model scenes with reflectivity data. A small scale model is made of a scene of interest. Regions of the model are textured according to the type of surface they will represent. The model is digitized under different iilumination directions, and a depth map is calculated by photometric stereo. Tables of reflectivity and/or emissivity data for scene materials are cornbined with the surface gradient map and flight geometry information to yield an intensity image at any desired wavelength, after which various kinds of noise can be incorporated into the image. The method is discussed with respect to the simulation of airborne active thermal infrared images of surface-laid minefields. However, no specialized sensors are necessary, and the method can be used for active or passive sensors of any wavelength, provided reflectivity or emissivity values are published or can be measured. The method may be also applied to the generation of images that are more general than aerial views of terrain.

A new approach to modeling and evaluating storage media for archival purposes is presented. Different models are presented with varying document storage requirements ranging from 25,000 to 1 million per day. This evaluation process can be very useful for a variety of industrial applications where very large amounts of storage over the years is required. A media selection methodology is given to assist users in the evaluating process. The optical disk is a stable, reliable, high-capacity, high-performance, and very cost-effective storage media for data storage and archival applications. The disk provides very high data storage capacity for a low cost per megabyte compared to other on-line storage devices. Optical disk-based storage technology is recommended for archival storage for various applications in the data and image processing area, such as engineering, manufacturing, document management, banking, insurance, and health care. We evaluate different storage media for long-term archival of large amounts of data and the cost-effectiveness of different storage media for various models based on document storage requirements.

An HREM (High-resolution electron microscope) image analysis approach has been developed. The image filtering, segmentation and partides extraction based on gray-scale mathematical morphological operations, are performed on the original HREM image. The final image is a pseudocolor image, with the background removed, relatively uniform brightness, filtered slanting elongation, regular shape for every kind of particle, and particle boundaries that no longer touch each other so that the superconducting material structure can be shown clearly.

The proposed approach to stereo image coding takes advantage of the singleness of vision property of the human visual system. A stereo image pair, in which one of the images is low-pass filtered and subsampled, is perceived stereoscopically as a sharp 3-D image. The depth information is perceived due to the stereopsis effect, and the sharpness is maintained due to the details in the nonfiltered image. Low-pass filtering, subsampling, and discrete cosine transform image coding are used for the compression of the stereo images. A methodology for the evaluation of the compression effects on the 3-D perception of compressed stereo images is presented. It is based on measurements of response time and accuracy of human subjects performing simple 3-D perception tasks.

Finite difference and finite element methods, and the coupled mode theory are combined to study in detail the ion-exchanged glass channel waveguides. Ordinary and grating-assisted waveguides are analyzed. The effect of various device parameters on waveguide behavior is investigated. Design curves to make waveguides with required characteristics are provided.

Optical reception antennas (telescopes) must be capable of receiving communications even when the deep-space laser source is at a small solar elongation (appears from Earth to be located within a small angle of the Sun.) Direct sunlight must not be allowed to shine on the primary reflector of an optical reception antenna, because too much light would be scattered into the signal detectors. A conventional sunshade that does not obstruct the antenna aperture would have to be about five times longer than its diameter for reception at a solar elongation of 12 deg. Such a long sunshade is unwieldy, either on the ground or in space. Since a new large-aperture optical reception antenna will probably have a hexagonally segmented primary reflector, a sunshade consisting of closely packed hexagonal tubes is proposed. It will be mounted in alignment with the segmentation to avoid producing any additional geometric obstruction. The tubes will be extended downward toward the primary reflector, until they reach the envelope of the focused beam to the secondary reflector. When the optical reception antenna is ground based, the other ends of the tubes will be trimmed and the antenna will be mounted so that both the sunshade and the antenna will swing within a sphere whose diameter is only six-fifths the diameter of the primary reflector. If the segmentation involves four rings of hexagons around an absent central hexagon, then this sunshade will be useful when the solar elongation is as small as 12 deg. The usefulness can be extended to 10 deg by adding shutters to block the tube corners that admit off-axis sunlight. Vanes or slats may be inserted in the tubes to permit operation at 6 deg, or double vanes down to 3 deg. The structure of the sunshade is very strong and may be used to support the secondary reflector instead of an independent support.

The reversible nonlinear interface (RNI) devices as universal logic gates are discussed. The optical implementation of a generalized pipeline cellular array using these devices for multifunctional binary arithmetic unit is proposed. This approach may eliminate geometrical constraints imposed in electronic implementation and, therefore, facilitate direct microminiaturization.

Hartmann wavefront sensors rely on an exact correlation between a transverse ray aberration measurement in the focal plane and the sampling hole position in the pupil identifying that ray. lf this relationship breaks down, the reconstructed wavefronts will not correspond to the actual incident wavefronts. This occurs if rays yielding certain transverse errors are misidentified, e.g., if sampling is in a plane not conjugate to the pupil. A case study is made of the SHAPE wavefront sensor in which such ray misidentification can arise.

The scanning knife edge method is widely employed to measure the modulation transfer function (MTF) of solid state charge-coupled device (CCD) imagers. This paper presents a method to correct for the situation where the knife edge is skewed at a small angle with respect to the CCD. Experimental results for a time-delay-and-integration charge-coupled device (TDI-CCD) imager demonstrate that the knife-edge skew introduces a degradation in the measured MTF. A model to explain this effect and a quantitative method to correct for small-angle skew is presented. A good agreement between the model and experiment is obtained. In a TDI-CCD imaging system, the effect of small-angle skew is amplified and cannot be ignored.

We describe three methods to measure the inhomogeneity of a window material. The first method immerses the window in a liquid between two planes. However, this method is inconvenient for some applications. The second method measures the optical figure of the front surface and then measures the return wavefront that transmits through the window and reflects from the rear surface of the window. The advantage of this method is that it can remove the contributions of both the surface figures and the return flat plus the system error of the interferometer. The disadvantage is that a small wedge must be fabricated between the two surfaces to eliminate spurious interference. The third method derives the inhomogeneity of the window material by measuring the optical figure of the front surface of the window and then flipping the mirror to measure the back surface. The advantage of this method is that it is not necessary to have a wedge between the two surfaces. The disadvantage of the window-flipping method is that the contribution of system error can increase.

A method for testing the surfaces of large mirrors has been developed at the National Astronomy Observatories (NOAO) to be used even when conditions ofvibration and thermal turbulence in the light path cannot be eliminated. The full aperture ofthe mirror under test is examined by means of a scatterplate interferometer that has the property of being a quasi-common-path method, although any means for obtaining interference fringes will do. The improvements in the NOAO method lie in the means for capturing the fringe pattern and the analysis that follows. The method uses a remotely operated CCD camera system to record the fringe pattern from the workpiece. Recording the spot pattern resulting from a Hartmann test screen placed over the workpiece is also possible, but the analysis methods will differ from those discussed. By operating the test equipment remotely, the optician does not cause unnecessary vibrations or heat in the testing area. The typical test is done with a camera exposure of about a millisecond to "freeze" the fringe pattern on the detector. Averaging up to 10 separate exposures effectively eliminates the turbulence effects. The analysis program is based on a method originally developed for examining telescope images affected by atmospheric seeing. From the intensity information, a phase map of the wavefront reflected from the surface is obtained using a new phase-unwrapping technique. The resolution is limited only by the number of fringes in the test aperture. The method described provides the optician with complete numerical information and visual plots for the surface under test and the diffracted image the method will produce, all within a few minutes, to an accuracy of 0.01 μm measured peak-to-valley. The method has been extensively used for a variety of tests of a 1.8-m-diam borosilicate glass honeycomb mirror, where the method was shown to have a sensitivity equal to a Foucault test. The test setup is described, including the analysis technique, and examples of the results obtainable are provided. The method continues to be used at NOAO for testing large optics (currently a 3.5-m honeycomb mirror).

We have developed a star-and-sky chopping polarimeter for accurate measurements of linear polarization of starlight in the standard astronomical photometric U, B, V, R, and I bands. The instrumental polarization, as determined by observing the standard unpolarized stars, is 0.04%. It is possible to use the instrument for the measurements of circular polarization as well. A UNICORN microcomputer controls the various operations of the instrument, acquires the data, and does the on-line data reduction. This paper describes the design and performance of the polarimeter.

We describe the design, fabrication, and performance of the frame-addressed spatial light modulator (FASLM), a frame-updated 128 x 128 deformable mirror device (DMD) spatial light modulator(SLM). This new DMD consists of a 128 x 128 array of mirror elements addressed by an underlying virtual phase CCD array. Each mirror element consists of four cantilever beam mirrors attached to a central pillar, allowing contiguous placement of the elements. The FASLM operates at higher speed (up to 4-kHz frame rate with 100% pixel addressing) and with a higher optical duty cycle (96%) than previous DMD SLMs.

This PDF file contains the editorial “Book Rvw: Fiber Optics and Optoelectronics," by Peter K. Cheo for OE Vol. 30 Issue 09

This PDF file contains the editorial “Book Rvw: Laser-Induced Plasmas and Applications," edited by Leon J. Radziemski and David A. Cremers for OE Vol. 30 Issue 09