SUMMARY In this work we analyze optical distortion for three types of missiles using three different turbulent models, with different degree of complexity, for the density fluctuations and show the effect that turbulent flow has on the performance of optical systems, like MTF and Strehl Ratio.
In this work a comparison with experimental results of two types of models of density fluctuation for
turbulent jets is presented. I also use realization method of the turbulence field in order to calculate beam
Optical radiation passing through compressible turbulent shear layer is distorted due
to fluctuations in the index of refraction. Most of the known data comes from
measurement of the optical phase change. Knowledge of the fluctuating density field
within the shear layer enables us to calculate the optical distortions. In the present
work, a series of models are presented with different type of complexity. All the
expressions presented are dependent on the turbulent kinetic energy and dissipation
rate calculated by CFD codes. Calculations based on the models are compared with
available experimental results. Some examples of application to aero-optics are
In this work a new model of density fluctuation for turbulent shear layers is presented. The density fluctuations are calculated by new numerical and analytical models based on CFD and are compared to those calculated by existing models. Some comparisons to experimental results are presented as well. I also use realization method of the turbulence field in order to calculate beam wander directly.
In this work we present results of turbulent effects on the propagation of laser beam through turbulent jets. Several jets were examined, using CFD computations and then the density fluctuations were calculated using several models. The effect of the jet on imaging and on the optical resolution is presented.
In this work we investigate optical distortions caused by the existence of a turbulent shear layer in a beam path. We look at several propagation paths and evaluate the loss of resolution caused by the inhomogeneous layer located at various distances from the transmitter.
We use our wave-optics code for atmospheric propagation and implement into it propagation through a shear layer. Thus we are able to calculate a combined beam propagation, either emanating from the optical window or incoming from an outside source. The fluctuations of the index of refraction are calculated using the Wye's model
The impact of aerodynamic flow upon the performance of an airborne optical system is becoming a critical issue in the development and engineering of IR electro-optic systems. The analysis of this impact is now in the state of the art of IR electro-optic system research. Significant effort has been made on this issue during recent years. In this work we describe a novel technique for aero-optic calculations. The technique is based on commercially available software. In this work CodeV is the optical ray tracing code and Fluent is the Computational Fluid Dynamics (CFD) code. The synergetic combination between the output of the CFD code and optical software leads to the development of the method. The optically relevant data from the CFD results is transformed into index of refraction field and introduced as an input to the optical code. It is important to note that the data must not necessarily be presented in an analytical form; rather it is introduced in the most general form - as a discrete set of values located at a non-uniform grid of points.
The modified quadratic Shepard method has been adopted for the data interpolation. This enables a simple interface with virtually any software output. Such compatibility ensures that the technique can be easily extended for the solution of a whole spectrum of optical problems that involve arbitrary index of refraction changes in the bulk and arbitrary optical surface shapes. For example image quality degradation caused by dome heating can be easily assessed. Both index of refraction changes of the dome and dome shape distortion being taken into account. Several numerical simulations demonstrating the technique are presented.
Turbulence models of density are needed for predicting the performance of airborne optical systems. The existing CFD codes model velocity fluctuations. To avoid rewriting large CFD codes, there is a need for simple yet accurate models, which will be based on the result of standard CFD codes. The applicability of these models to Aero-Optics problems is done by using the relation between the variance of density fluctuation to the optical distortion. The algebraic model that we present here gives good agreement with experimental result for Mach number as high as 9. We also presents models that can be implemented into existing CFD codes by using the result of regular two-equations turbulence models and compare the result to those obtained using CFD results and airborne experiments. We calculated the effects of turbulent fluctuations on optical systems.
A resonator based on a positive branch confocal unstable resonator with toroidal curvature mirrors is presented. The mirrors have different radii of curvature in perpendicular directions. In one direction, the curvature (main curvature) is strong, and it governs the main properties of the resonator. In the perpendicular direction, there is a weaker (secondary) curvature acting to decrease resonator's sensitivity to mirror tilts. Resonators of different size, gain, and output coupling are examined, and attention is given to phase distributions, near-field intensity, beam quality, and intensity distribution. Focus is placed on basic eigenmodes for uniform and nonuniform gains, mirror tilt, and phase perturbations. High far-field intensity and increased power-extraction efficiency in nonuniform active media in such a resonator are emphasized.
A detailed calculations of the optical quality of a large aperture
telescope mounted aboard an aircraft is presented. The open fuselage platform
flies at high altitude, at near sonic speed. The optical degradation of the
telescope performance due to the surrounding is evaluated.