An innovative real-time imaging Stokes spectropolarimeter is presented. The main unit of the polarimeter is an integral polarization-holographic diffraction element, which enables the complete analysis of the polarization state of light to be carried out in real time. An element is recorded by a special holographic schema using circularly and linearly polarized beams. As a result it decomposes an incoming light into orthogonal circular and linear diffraction orders. Upon simultaneous CCD intensity measurements of the corresponding points or areas in the diffraction orders and further data reduction through the calibration parameters we get real-time Stokes images of a light source. The further reduction of Stokes images allows to determine detailed polarization state of a light coming from a point or extended space object in a narrow or a wide spectral range. The operating spectral range of the polarimeter is 500-1600 nm with diffraction efficiency equal to 20% at 532 nm, 16% at 635 nm and 2% at 1550 nm. The laboratory calibration tests were obtained with a quasi-monochromatic point size depolarized light source which further were circularly or linearly polarized with known polarization parameters and a degree of polarization near to 100%. The theoretical model of relations between measured intensities in different diffraction orders and Stokes parameters, earlier developed by the authors (Kilosanidze B., Kakauridze G. SPIE Proceedings, vol. 8082-126, 2011), were used to calibrate the polarimeter. The laboratory tests show that the resulting errors for single measure are near of 10-2 or less.
An innovative real-time polarimetric method is presented based on the integral polarization-holographic diffraction element developed by us. This element is suggested to be used for real time analysis of the polarization state of light, to help highlight military equipment in a scene. In the process of diffraction, the element decomposes light incoming on them onto orthogonal circular and linear basis. The simultaneous measurement of the intensities of four diffracted beams by means of photodetectors and the appropriate software enable the polarization state of an analyzable light (all the four Stokes parameters) and its change to be obtained in real time. The element with photodetectors and software is a sensor of the polarization state. Such a sensor allows the point-by-point distribution of the polarization state in the images of objects to be determined. The spectral working range of such an element is 530 – 1600 nm. This sensor is compact, lightweight and relatively cheap, and it can be easily installed on any space and airborne platforms. It has no mechanically moving or electronically controlled elements. The speed of its operation is limited only by computer processing. Such a sensor is proposed to be use for the determination of the characteristics of the surface of objects at optical remote sensing by means of the determination of the distribution of the polarization state of light in the image of recognizable object and the dispersion of this distribution, which provides additional information while identifying an object. The possibility of detection of a useful signal of the predetermined polarization on a background of statistically random noise of an underlying surface is also possible. The application of the sensor is also considered for the nondestructive determination of the distribution of stressed state in different constructions based on the determination of the distribution of the polarization state of light reflected from the object under investigation. The prospect of this sensor application in astropolarymetry both for land and space telescopes is also discussed.
A new real-time nondestructive polarimetric method is suggested for the determination of the stressed state distribution
in different objects. Light reflected from the object is polarized in a varying degree, and the distribution of the
polarization state in the object image is related to the distribution of stresses in it. Method is based on the obtaining the
distribution pattern of the polarization state of light in the object image, which is formed by an objective. The integral
polarization-holographic diffraction element developed by us is used for real time complete analysis of the polarization
state of light at each point of the image, formed by the element in the diffraction orders. The simultaneous measurement
of the intensities in four diffracted beams by means of a matrix of photodetectors and the appropriate software enable the
polarization state of an analyzable light and its change to be obtained in real time. The laboratory model is presented.
The correlation relations between the polarization state of light reflected from the sample with the distribution of the
dosated mechanical stresses is considered. The theoretical model is presented. The experimental results are shown for
different samples with one- and two-axis stress distribution. The method is nondestructive, i.e. there is no need to drill
holes or openings or sticking transparent photoelastic plates on the object to determine the stresses. This method will
enable the distance monitoring and diagnosis of already existing constructions to be carried out. This method will differ
by universality, simplicity, high speed and comparative cheapness.