Our publications

# Borovitsky V., Fesenko V., Molodyk A. Performance evaluation of infrared imaging systems

The paper presents an approach for performance evaluation and parametric optimization of imaging system design. This approach is based on calculation
and minimization of image distortion. It applies the criterion based on minimization of normalized least-square image error. The proposed mathematical apparatus makes possible evaluation of the performance and calculation of optimal parameters that reduces image distortion caused by spatial filtering and noise. The paper illustrates the application of the proposed technique for performance analysis of a scanning system.

# Borovytsky V., Chorna V. Intensity distribution near focal point of high aperture optical system formed by partly polarized light

The paper presents the mathematical technique for calculation of three dimensional intensity distribution near a focal point of a high aperture optical
system in case of quasi monochromatic partly polarized light. This technique is extension of the vector diffraction theory for high aperture optical systems. It is based on Huygens-Fresnel principle: spherical wave at an exit pupil is considered as a numerous set of elementary secondary partly polarized light sources. The total intensity is calculated as superposition of complex wave amplitudes taking into account polarization orientation, degree of polarization defined by Stokes parameters, orientation of detector aperture and coherence length of quasi-monochromatic light.

# Borovytsky V., Fesenko A. Diffraction depth of focus in optical microscope

The paper presents the mathematical technique for calculation of the diffraction depth of focus of an optical system of a widefield microscope. The proposed technique applies the Rayleigh criterion based on evaluation of the wave aberration appeared due to defocus in a high aperture optical system. The maximal value of a linear approximation of the defocus wave aberration is used to define the depth of focus. It is proven that in optical systems with numerical aperture higher than 0.5 have the diffraction depth of focus 25 - 40 % smaller than the widely known formula defines. This fact is important for implementation of autofocus and digital focus extension algorithms. The nonsophisticated formula for calculation of the depth of focus is proposed. The results of experimental measurements of the depth of focus are presented and discussed.

# Borovytsky V., Fesenko V. Imaging system performance evaluation: NETD, least-square error, or correlation

There are several techniques for performance evaluation of an imaging system (IS). The first is the classical one: performance is considered as a
characteristics called minimum resolvable temperature difference (MRTD). The second one is fidelity which is a parameter based on the least-square error
between output signals of the idealized IS and an investigated one. The leastsquare error takes into account noise and distortions introduced by high spatial frequencies suppression. The third technique is defined via correlation coefficient between output signals of the idealized IS and a definite one. The paper discusses the application of the mentioned approaches for performance evaluation.

# Borovytsky V., Fesenko V. Nonuniformity correction in infrared imaging systems

The paper represents the approach for residual non- uniformity evaluation after two-points linear non-uniformity correction. The approach takes into
consideration parameters of an imaging system, reference source, non-linearity and noise of multi-element photodetector.

# Borovytsky V., Fesenko V. Performance evaluation of sampled imaging systems

The paper discusses several techniques for performance evaluation of passive digital imaging systems. The principal approach of these techniques is a
comparison of the output signals from a real imaging system and from the idealized one. The first technique applies the normalized least-square error
called fidelity as an absolute measure of the output signal difference. The second technique uses the correlation coefficient that reflects the difference
between linear combinations of the output signals as an estimation of performance. The third technique is based on evaluation of the information rate
of the output signals.

# Borovytsky V., Fesenko V., Molodyk A., Zavorotny P. Imaging system performance analysis and optimization using objective image quality criteria

The paper presents an approach for performance evaluation and parametric optimization for IR imagin system design. This approach is based on calculations and minimization of image distortion. It applies the criterion like minimization of normalized least-square image error. The proposed mathematical apparatus makes possible evaluation of the performance and calculation of optimal parameters that reduces image distortion caused by spatial filtering and noise. The paper illustrates the application of the posed techniques for scanning system performance analysis and design.

# Borovytsky V., Fesenko V., Molodyk A., Zavorotny P. Application of correlation techniques to infrared imaging system optimization

The paper describes an approach to optimization of passive infrared imaging systems based on maximization of the correlation between output signals of an idealized imaging system and a real one. This approach guarantees the optimal balance between temperature and spatial resolutions of the imaging system for any given test object. The paper represents a mathematical apparatus that binds a coefficient of correlation between the output signals with parameters of an imaging system such as focal distance, aperture diameter, dimensions of photosensitive element and etc. This apparatus allows to evaluate the performance and to get a merit function for optimization. Results of optimization and problems of identification of the best relationships between spatial temperature and resolutions are discussed.

# Borovytsky V., Fesenko V., Zavorotny P., Molodyk A. Parametric optimization of imaging system based on minimization of image distortion

The paper describes an approach to parametric optimization of an IR imaging system. This approach is based on minimization of image distortion of a multibar test object. The quality of imaging system is defined by a probability of correct pixel classification. This probability characterizes an error of image
binarization. The paper represents the mathematical model that binds the probability of correct pixel classification with parameters of an imaging system
such as focal length, aperture diameter, dimensions of photosensitive element, integration time and etc. It allows to get the merit function for parametric optimization and to identify the optimal relationship between spatial resolution and temperature resolution.

# Borovytskyi V. Comparison analysis of illumination systems for digital light microscope according to uniformity of irradiance distribution

This paper represents comparison analysis of schemes for illumination channel in a light microscope - Kohler illumination, projection and critical illuminations.
It is proved that these schemes are particular cases of the proposed common scheme for microscope illumination. It is calculated uniformity of irradiance
distribution on sample surface produced by different particular cases of this common scheme with a halogen lamp or a uniform extended light source. It is showed that the high uniformity can be reached not only in Kohler illumination.