I.P.Torshina, Y.G.Yakushenkov

Moscow State University of Geodesy and Cartography (MIIGAiK)

Gorokhovsky by-str., 4, Moscow 105064, Russia

General Methodology of Modern Electro-Optical Devices’ Computer Modeling

Electro-optical systems are the devices which use optical radiation (optical signals) as a carrier of information on the object being investigated or observed and convert the energy of radiation into electric energy for preliminary data processing. The electro-optical devices (EOD) engage with wide variety of applications, as example, ground, air, and space based systems. Setting of the range performance for the complex target-background situation is a difficult and expensive task enough. Many traditional methods of designing don’t take account of complexity and changeability of the target-background situation, the particular feature of the concrete system, and other factors. Therefore it has been proposed to utilize a computer modeling for assessment.

A certain version of generalized EOD computer model (EOD CM) has been worked out by the Electro-Optical Design Department, the Moscow State University of Geodesy and Cartography (MIIGAiK). Our general methodology of EOD CM construction has been stated in [1,2,3]. The peculiarities of multispectral EOD modeling based on general EOD CM has been marked in [4, 5].

The functional program ensuring of EOD CM may be divided into two parts: 1. composition of EOD CM, and 2. appraisal of its adequacy.

The structure EOD CM is the aggregate of its main blocks (submodels). These submodels are: “Starting Data”, “Figures of Merit”, “Scenario”, “EOD Structure”, “Result of Computer Modeling”, “Data Base of Computer Model” (Fig.1). Due to modular structure of the model it is possible to simulate a wide range of different EOD and interactions between the EOD, the observed scene, its environment, and the date processing algorithms.

The model executive allows user to realize various conceptions of EOD operating and to modify these conceptions working out in its details, or simplifying the model in accordance with the available data bases and the requirements to model adequacy and robustness.

For EOD 3th generation which are named usually the devices working in two- or multi-spectral ranges with matrix focal plane arrays, computer model may be formed on the basis of the general EOD CM by means of addition special module “Correction of General EOD CM” supplementing of “Data Base of Computer Model” [5].

Fig.1. Structure of EOD general model

Individual subsystems of the “EOD Structure” submodel (“Optical System”, “Detector”, “Electronic Block”, “Display”, etc.) may be represented by their modulation transfer functions (MTF). The functions as well as specific parameters of the EOD elements may be packed into special blocks of submodel “Data Base of Computer Model”. The MTF of the entire EOD is composed of a number of partial MTF. These functions may be used to determine a noise bandwidth and others figures of merit of EOD, for example, “Signal-Noise Ratio at EOD Exit”. The submodel “Data Base of Computer Model” concludes a set of different blocks: “Radiators”, “Atmosphere”, “EOD Elements and Algorithms Base Data” “EOD Figures of Merit”, and many others. These blocks (data bases) may be realized as analytic forms, for example, transfer functions of individual EOD blocks, as numeric, graphs, tables, etc. Parameters and characteristics of many possible radiators and the earth atmosphere have been packed into separate blocks. The block “Atmosphere” has been designed to incorporate path transmission and path radiance for different EOD fields-of-view. An EOD working scenario may be built by selecting required files and manipulating their input parameters. This block architecture has been successfully implemented using object-oriented engineering software techniques.

A structure and form of the different blocks of the “Data Base of Computer Model” may be changed for the various concrete EOD, for example, for different figures of merit. So for the electro-optical warning systems the block “Atmosphere” may contain the data about atmospheric transmission and radiation only, and for the electro-optical servo systems with high spatial resolution this block may contain the data about atmospheric turbulence too.

After receiving results of modeling in the form of demanded figures of merit it is necessary to find an adequacy of the model using the criteria of adequacy to be selected.

Calculation algorithms of definition the reflection, the transmission, and the absorption for various surfaces of targets, backgrounds, and obstacles must take into consideration changing these physical quantities for different wavelengths and orientations of the surfaces.

User can use such specific EOD-3 figures of merit as the spectral contrast ratio, the difference of individual spectral signals, the spectral ratio, the logarithmic spectral ratio.

At the first stages of EOD designing it is advisable CA evaluation through the rejection of EOD figures of merit from the meaning to have been assigned. It may be convenient to evaluate an adequacy with the help of numeral methods. So the meaning is depended on EOD parameters and characteristics changes it is possible to use the method of exact differential for CA calculating. Separate parts of the perfect differential (the partial derivatives) are determined by parameters of individual EOD blocks. Forming the histograms of figure of merit differences as a functions of the input EOD parameters it may be possible to find the partial derivatives of a figure of merit function and calculate the perfect differential as a CA.

BIBLIOGRAPHY

1. I.P.Torshina . “Computer Modeling of Electro-Optical Preliminary Data Processing Systems”. - Moscow, Logos Publisher, 2009.– 248 p. (rus.),

2. Y.G.Yakushenkov. Electro-Optical Devices: Theory and Design. - Moscow, Logos Publisher, 2011.– 568 p. (rus.),

3. I.P.Torshina and Y.G.Yakushenkov. “Structure of General Electro-Optical Systems’ Computer Model”.- Science-Technical Herald of Sankt-Petersburg State University IFMO, 2009, № 6(64). P.5-9 (rus),

4. V.V.Tarasov, I.P.Torshina and Y.G.Yakushenkov. “Infrared Systems of 3-th Generation”.- Moscow, Logos Publisher, 2011.– 240 p. (rus.),

5. I.P.Torshina and Y.G.Yakushenkov. Peculiarities of Computer Modeling for Electro-Optical Systems of 3th generation. – Optical Journal (Journal of Soviet Optical Technology), 2009, № 2, P. 87-89 (rus)

I.P.Torshina – Dr.Sc., Dean of Optical-Information Systems and Technologies Faculty, the Moscow State University of Geodesy and Cartography (MIIGAiK)

Y.G.Yakushenkov – Prof., Dr. Sc., Chief of Electro-Optical Department, Optical-Information Systems and Technologies Faculty, the Moscow State University of Geodesy and Cartography (MIIGAiK)