Analytical results are presented showing improved detection and location performance of point sources in a staring sensor using a hexagonal detector array or having the capability to adjust the size of its blur spot (variable focus). Square and hexagonal detector arrays are compared for detection probability versus focus, for location accuracy versus focus and signal-to-noise ratio, and for location accuracy versus blur size and detector array fill factor. We find that hexagonal detectors provide better detection probability when the point source lies near a corner of the detector, but otherwise the two detector types give comparable performance. Hexagonal detectors generally give better location accuracy than square detectors. Variable focus is shown to be advantageous for maximizing performance for both detection and location of point sources.

Abstract. The effect of noise, including system noise, background noise, and cell-to-cell nonuniformity (spatial noise), is mathematically treated and experimentally verified for staring-mode infrared cameras. Spatial noise is shown to be dominant in high background environments (3 to 5 Am or 8 to 12 Am imagery at background temperatures greater than 0°C) even after compensation. Camera sensitivity is quantified by a contrast signal-to-noise ratio that includes the effects of system, background, and spatial noise. Past analysis of camera performance has assumed that the cell-to-cell nonuniformity can be completely removed by using nonuniformity correction techniques. We present data showing that neither variations in detector spectral response nor excess low frequency noise can be fully corrected using existing nonuniformity correction techniques. Furthermore, we show that even the small amounts of nonuniformity that persist after the application of correction algorithms will significantly degrade camera performance.

We introduce a new method of finding periodic phase relief structures, which produce the desired diffraction pattern with high light efficiency (75% to 96%) and low noise (<±1%). Use is made of explicit equations for the angular spectrum of the field immediately behind such structures and of different stochastic nonlinear optimization methods.

The gradient index (GRIN) lens law for Gaussian beams is derived by matrix formalism. By use of this law, image and focal shifts are evaluated. The results are applied to Selfoc lenses to calculate positioning errors when GRIN connectors are inserted into optical communication systems.

The ray matrix method (ABCD law) is used to determine the cardinal points of a gradient index lens. An analogy to a conventional simple optical system is also established for which Gaussian and Newtonian formulas are applicable.

The White cell is a unit-magnification image relay system consisting of three noncoaxial spherical mirrors of equal curvature. The cell is used to provide a long optical path in a relatively small physical space. Multiple reflections are used, in a manner similar to an unstable laser resonator. A particular application is an optical delay line on the input of a streak camera to allow for the finite triggering time of the sweep start. This paper addresses the first- and third-order properties of the White cell. A displacement sensitivity analysis is included.

The drastically reduced costs and improved performance of fiber optic components in recent years offers an opportunity to economically incorporate high-bandwidth optical communication links within a large-scale multiprocessor system. In this paper, the design, implementation, and initial performance of a fiber optic bus for a tightly coupled multiprocessor system are discussed. This optical bus ulitizes a multiple fiber-multiple star configuration with data rates of up to 80 MHz. It transmits bus control line information by repetitively scanning the control lines and transmitting their states as a packet of bits. It is currently being used for a 30-processor system called the Heidelberg Polyp, which has a custom bus design. However, the design approach is a general one that could easily be adapted to other buses, especially asynchronous buses such as the VME bus.

The operation and features of an electronically switched, programmable binary fiber optic delay line are discussed. The design, component selection, fabrication, testing, and evaluation of a prototype are presented. The prototype comprises seven delay stages, has a maximum delay of 5µs and a resolution of 39 ns, operates over the 0.5 to 1 GHz band with a dynamic range of 36 dB, and has a power consumption of 19 W.

Many adaptive phased array radar (APAR) high-resolution spectral estimation techniques are used to determine far field signal power and location. Once this information is known, placing nulls at these locations to cancel jammers can be accomplished through a proper choice of antenna weights. The antenna weight and angular pattern domains are related through Fourier transformation. To obtain a fine sampling in the angular domain in order to accurately specify the desired nulls, it is required to extend the antenna aperture by padding it with zeros. However, in the final weight vector applied to the antenna output, the contribution of these extra elements must be zero since they do not correspond to available antenna elements. This provides two sets of constraints on the solution: the set of desired nulls in the angular domain and the available aperture in the weight domain. A method of finding a solution that matches constraints in both the time and frequency domains is the Gerch-berg-Saxton algorithm, which is often applied to image reconstruction. This paper describes an investigation into the behavior of this algorithm as applied to the discrete, one-dimensional antenna pattern synthesis case. The algorithm is presented in matrix/vector form, and its transient and steady state responses are derived. To assist in this analysis, we introduce a new matrix operator that greatly simplifies the required derivations. Computer simulation and numerical evaluations of the analytical results are included to demonstrate the applicability of the algorithm to pattern synthesis.

A simple new method of automatically reconstructing the 3-D surface of an object from 2-D moire patterns is proposed. The method can automatically and accurately obtain phase value at every pixel point without assigning fringe orders and interpreting data in the regions between fringes by using a discrete cosine transform based algorithm, which is free from errors caused by the higher harmonic components, the variation of dc light level, and the modulations of amplitudes on a fringe pattern. The method is capable of fully automatic distinction between depression and elevation on an object surface. Theoretical analysis and experimental verification are presented.

The standard single-target acquisition model used in military applications for human target acquisition using infrared systems has been extended to the multitarget scenario. It incorporates three possible versions, depending on the underlying causes for the nonunity detection probability at infinite time and the degree of correlation between targets.

The Center for Night Vision and Electro-Optics search model is extended to cover cases involving multiple observers under conditions with time-varying obscurants. We find that simulations with two levels of visibility conditions indicate that the persistence time of an obscurant and the correlation between observers are crucial parameters for determining the average time for first detection.

A system is described for obtaining both an estimate of the spatial mean bidirectional reflectance factor (BRF) for a tree canopy (displaying a horizontally heterogeneous foliage distribution) and the statistical significance of that estimate. The system includes a manlift support-ing a horizontal beam 7 m long on which are mounted four radiometers. These radiometers may be pointed, and radiance data acquired, in any of 11 view directions in the principal plane of the sun. A total of 80 data points, acquired in 3 min, were used to estimate the BRF of a walnut orchard 5 m tall and detect true differences of 12% of the mean approximately 90% of the time.

A generalized polychromatic point spread function applicable to optical imaging systems under broadband illumination is derived. The combined wavelength-dependent function, i.e., the product of the object radiance, medium transmittance, and detector response, is characterized by two parameters, the mean and standard deviation.

A complementary field method has been devised for interferometric tomographic reconstruction of high-speed aerodynamic flows involving a shock. It is based on the reconstruction of the complementary field, which is the difference between the object field to be reconstructed and its estimate. The method is iterative in nature and incorporates a priori information. This study demonstrates advantages of the method in alleviating the deficiencies associated with computational reconstructors and measured data. Substantial reconstruction improvement is obtained, especially near a shock when its position is utilized as a priori information. Under the test conditions, convergence of the method is rapid.

Twenty-first century demands on "Top Gun" pilots are so great that the relative narrow field of view of head-up displays (HUDs), approximately 20° in a fixed direction, is far too limiting and confining for all the tactical information that is needed to be displayed for them to make split-second decisions based on sound judgement. This inadequacy has led, in part, to the development of helmet-mounted displays (HMDs), and thence to helmet integrated systems (HISs). This paper gives highlights from the patent description of a HIS that dates back to World War I and that is a forerunner of the concept of those being developed today.

On Friday, October 16, 1987, the Dow Jones industrial average fell a record 108 points for a single day. Only three days later, on "Black Monday," the Dow fell an incredible 508 points, followed by yet another huge loss of 157 points just one week later, on Monday, October 26, 1987. What was going on? The event that was alleged to have triggered all of this downside activity was "the report of a larger-than-expected trade deficit." However, certain usually reliable but unnamed sources suggested that there may have been a connection between these record-setting plunges and the optics community; after all, they occurred on the Friday prior to, during the week of, and on the Monday following the annual meeting of the Optical Society of America. This suggestion was summarily dismissed, because there simply couldn't be any way for a meeting of a few thousand optical scientists and engineers to influence the stock market. Impossible! Ridiculous! No way!

This is truly a classic book in our field. By all accounts and by the text itself, it is clear that R. W. Wood was what we call today an optical engineer. So far as I can tell the only new content(since Wood's 1933 revision) is a preface by John Howard.