Vladimir Ya. Mendeleev

Why a rough-surface scattering incident polarized laser light can be perceived as the depolarizing system

The degree of depolarization of laser light scattered from an isotropic rough silicon surface and a unidirectional rough steel surface was measured with a polarometer in the specular direction for angles of incidence from 30 degree(s) to 80 degree(s). Rms roughness of the surfaces was greater than laser light wavelength and less than correlation length of the roughness. For the laser light linearly polarized at a 45 degree(s) angle to the plane of incidence, dependence of the measured degree of depolarization on angle of incidence has one maximum and angle of incidence corresponding to the maxima is close to the pseudo-Brewster angle for a smooth surface for both the silicon and the steel. It is found experimentally that the reason for the measured depolarization is spatial variations of the azimuth and the ellipticity of the fully polarized scattered light within a polarometer aperture. Computer simulation of the scattering from a one-dimensional rough steel surface satisfactorily describing the dependence of the measured degree of depolarization on angle of incidence for the unidirectional rough steel surface for angles of incidence up to 70 degree(s) inclusive shows the single scattering makes the main contribution to the dependence of the measured degree of depolarization on angle of incidence.

Experimental study of a reason for depolarization of laser light scattered from a rough surface

The study is carried out for a unidirectional rough steel surface with rms roughness of 1.77 micrometers and rms slope of roughness of 0.135 rad. The degree of depolarization of scattered laser light with wavelength of 0.6328 micrometers was measured with a polarometer in the specular direction in the angular range of 30 - 80 degree(s). For laser light linearly polarized at a 45 degree(s) angle to the plane of incidence, the dependence of the measured degree of depolarization on angle of incidence has one maximum equal to 0.1 and an angle of incidence corresponding to the maxima is 70 degree(s). It is found experimentally that the reason for the measured depolarization is spatial variations of the azimuth and the ellipticity of the fully polarized scattered light within a polarometer aperture. Computer simulation of the scattering from a one-dimensional rough surface satisfactorily describing the dependence of the measured degree of depolarization on angle of incidence up to 70 degree(s) inclusive shows the single scattering makes the main contribution to the dependence of the measured degree of depolarization on angle of incidence.

Small optical device for measurement of surface roughness

The device based on the reflectometric method is intended to measure surface roughness parameter Ra by means of comparison of light power reflected from a measured rough surface and light power reflected from standard rough surfaces with known Ra. The light power is measured in the specular direction for the normal incidence. The range of measured Ra is 0.05 - 1.3 micrometers . The device was tested in factory conditions for measurement of surface roughness of a roller during grinding. Values of Ra measured with the device were compared with the values determined with a profilometer. Difference between values Ra measured with the both devices was no more than 10%.

Measurement of stimulated irradiation in multispectral photometry

Calibration methods of photometric spectral selection channels of biomedical in vivo photometer-spectrum analyzer which allow to measure absolute value of light fluxes at luminescence wavelength band (0.66 - 0.9 μm) during probe by wavelength 0.66 μm are presented. Three experimental calibration schemes for photometric channel are designed. Each channel consists of narrowband light filter, high sensitive pin-photoreceiver, amplifier block and ADC. Advantages and shortcomings of every scheme are discussed. Measurements of complete flux of light back scattered by the investigated sample and spectral analysis of this irradiation allow analyzing experimental data at quantitative level. The investigations of optical characteristics of biological tissues in vivo were made by means of calibrated photometer-spectrum analyzer. Tissues of volunteers belonging to different age with various diseases were investigated.

Reflectance for an approximately one-dimensional rough surface that has rms roughness greater than a wavelength

A relation between the intensity reflectances of approximately one-dimensional and one-dimensional rough surfaces within the diffraction solid angle in the specular direction for normal incidence is derived for an rms roughness greater than a wavelength. The relation shows that the reflectance of an approximately one-dimensional rough surface is proportional to the reflectance of a one-dimension rough surface. The validity of the derived relation is studied for an approximately one-dimensional rough steel surface with an rms roughness of 1.3 μm and a correlation length of 15.2 μm. The wavelength was 0.6328 μm and the angle of incidence was 4°. The reflectance of the rough steel surface was measured and estimated from the derived relation. Satisfactory agreement was found between the estimated and measured reflectance values.

Particularities of diffraction filtration by tissues in coherent and incoherent illumination

A new technique of image processing, based on signal resolution in accordance with its own functions of transformation of Fourier-Hermite functions, is represented in this work. The present technique was used to estimate the structure of biotissue under research. Experimentally obtained images of a model medium and tissue of a mans ear (volunteer) in vivo were compared under conditions of coherent and non-coherent optical illumination. The obtained results and prospects of the present method developing in medical application are discussed. The possibility of the suggested method of image processing being an element of optical tomograph of new type is analyzed in this work.

Estimation of biological mediums structure

The new technique of biological medium structure estimation based on optical diffraction filtration method is represented. Biological medium is considered as a superposition of cluster molecular structures. Depending on wavelength of probing optical radiation, during scattering the different particles participate which make a unique volume diffraction grating for each wavelength. The probing radiation characteristics variation allow to estimate the structure of the researched medium. Experiments on studying of coherent and not coherent optical radiation with biological media interaction have been carried out. The images of rabbits tissues, human tissues in vivo and fluoroplastic images were processed. For the first time scattered radiation image processing technique based on signal decomposition of the Hermite functions which are the eigenfunctions of Fourier transform was applied for such class of tasks. It has allowed to reveal in strongly scattered radiation a structural component. Estimating the characteristics of a structural component it is possible to receive geometrical parameters appropriate to probing radiation diffraction grating. The offered technique is perspective for studying biological molecular structures and creating tomographs of a new class.

Effect of surface roughness on measuring errors of optical constants estimated from spectral distribution of reflectance

Relative measuring errors of optical constants calculated from modified Kramers-Kronig relations are estimated for steel and gold surfaces having rms roughness 0.01 μm, 0.02μm, and 0.03μm. Spectral distributions of intensity reflectance used for the calculations are given for two spectral ranges of 0.14-6.4 eV and 1.4-6.4 eV. It is found the measuring errors slightly depend on the spectral range variations and the main contribution to these errors is brought by the surface roughness.

Experimental investigation of the penetration depth of laser light influence on the distribution of backscattered radiation intensity

In this work the research of influence of the laser radiation penetration depth in fluoroplastic on distribution of backscattered radiation intensity is carried out. The comparison of results received at intensity measurement of backscattered low intensive laser radiation in photometer and the geometrical sizes of the images of distribution of backscattered radiation intensity, registered CCD-camera is carried out. The well adjusted dependences are received. They show, that with growth of scatterer thickness the intensity of backscattered radiation increases, and the geometrical sizes of backscattered beam increases. On thickness, which depends on fluoroplastic optical characteristics and characteristics of initial radiation, the growth of the fixed characteristics ceases.

Possibility of remote sensing of surface roughness with a projector microscope based on a copper vapor optical quantum generator

Rough surfaces were illuminated by yellow (?=O.5782 ?m) and green (?=O.5106 ?m) light of a copper vapor optical quantum generator, and the light scattered from the surfaces passed through a projector microscope. The microscope included a laser tube of the quantum generator and a Glan prism placed inside an unstable resonator of the quantum generator. Slightly and very rough steel surfaces with small rms slopes of roughness were studied. The original ratio between intensities of the illuminating yellow and green light was transformed by both the rough surface and the projector microscope. Rough surfaces amplified the ratio of intensities of the scattered yellow to green light and the amplification factor depended on the statistics of rough surfaces. The ratio of intensities of the yellow to green light at the output of the projector microscope increased with increasing intensity at the input of the microscope. For the relative intensity greater than 0.4, the projector microscope amplified this ratio and the ratio was attenuated by the microscope for smaller relative intensity. Two methods for measuring surface roughness are proposed.