Research On Optical Realization Of Texture Direction Detection

Image is the carrier which records the information of object scene in the form of light perception, texture is the essential attributes of image and the important basis for image analysis and processing. Texture itself has the characteristics of direction,periodicity and randomness. Among them, texture direction is the statistical regularities of grayscale distribution arrangement in image regions. So texture direction detection is the proper meaning for researching texture attributes.Compared with the electronic information processing, optical information processing has the advantages of parallelism, high speed and large capacity. However,the optical method of texture direction detection has not yet appeared. This thesis mainly focuses on the texture direction regularity, spatial frequency characteristics,energy properties of image and the features of optical information processing method. It researches on the relationship between directionality and energy in the distribution of texture "element" and the characteristics of optical information processing system, and analyzes the connection between two mathematical models, then forms the optical realization method for texture direction detection based on energy measurement.The frequency components of texture in the same direction will redistribute in a regular arrangement at zero frequency in the spectrum by performing Fourier transform,and the direction of distribution is perpendicular to the texture direction, therefore, the texture direction and the energy distribution of frequency are interrelated. As directional filter has directional spectral selectivity, the ideal directional filters and the non-ideal directional filters with shift invariance and good spectrum weighting characteristic are obtained according to the spectrum division and the filters' generation structure. Then the optical directional filter is obtained according to the information processing process and limitation of optical 4f system. The energy distribution of frequency can be obtained by the intensity of final images when texture image is being optical directional filtered, then the texture direction will be obtained according to the vertical relationship between the directions in spatial frequency domain. In order to reduce the error of texture direction detection, the method of energy value vector is adopted to correct the direction.For this purpose, this thesis firstly introduces the texture's characteristics in spatial frequency domain, the existing methods of texture direction detection and the designmethod of optical directional filter. What's more, the filter mode is selected by comparing the effect of texture direction detection of ideal and non-ideal directional filter. After that, the method of texture direction detection based on energy measurement is described, and the correctness and validity are verified by the simulation under optical condition. Then, the optical realization of texture direction detection is obtained combining with the characteristics of energy distribution and optical directional filter.Finally, the feasibility of the optical realization method of texture direction detection is verified by the actual optical system.