Multispectral Method for Air Tract Influence Attenuation

Abstract

multispectral method for air tract influence attenuation on basis of color detector with Bayer filter is introduced. The difference in position of target image in different colors allows compensating the air tract refraction.OCIS codes: 120.4570, 150.3045 Optical-electronic systems for position control of large-scale objectsOptical-electronic systems are widely used for the position control of large and critical objects (geodesic systems for engineering structures, etc.). Often the accuracy less than 0.1 mm at the distance up to 20 m is required, for example the turbine units of atomic plant should be aligned with accuracy less than 0.06 mm [1]. As a rule an opticalelectronic system consists of a reference target (light source or reflector) mounted at the object under test and of a detecting part with a lens, sensor and image processing unit.Generally at the distances more 10-20 m the main negative influence on the accuracy of mentioned systems exert the state of the air tract: air refraction and turbulence. This influence increases if the system operates at the open air or at rugged environment. The refraction causes the systematical deflection of the ray path because of the air temperature gradient that changes the air refractive index, while the turbulence acts as a random motion of air layers and flows. Multispectral method for air refraction attenuation based on a color matrix sensorMultispectral method is one of known that allows attenuation and compensation of the air tract refraction [2]. The method is based on the analysis of two or more wavelength propagation through the air tract. It's known that the air refraction could be compared with wedge, so used wavelengths will deflect in a separate way (according to wedge refractive index) and at specific distance a linear spacing between them could be measured. This spacing allows estimating the value of air temperature gradient and as a result to attenuate the air refraction.The main idea of the paper is the possibility analysis of realization of the multispectral method on basis of a widespread color matrix detector (CCD or CMOS sensor) with Bayer filter [3]. Such a sensor allows registration the difference in the position of target images in different spectral ranges just using the information from different color channels (RGB scheme). The target (light source) should be multispectral too (white LED is proposed to be used). The figure shows the position of target image at blue, red and green frames. 0 X Y pby p bx Yb EC

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