CAMERA AUTOFOCUSING METHOD Russian patent published in 2014 - IPC G02B7/36 

FIELD: physics, optics.

SUBSTANCE: invention relates to optical-electronic devices intended for autofocusing of objective lenses. The method consists in evaluation of sharpness, at which for each pixel of the image the conversion of RGB signals of main colours into uniform colour space is performed. For this purpose the image is scanned using a sliding window with the sizes 3×3. At each iteration in the window the algorithm of recognition of the image of fine structure is performed. Binary images of fine structures are used for recognition, using which the spatial coordinates of pixels of object and background are determined. The analysis is performed for all types of fine structures, starting from the first one (point object). The average values of coloured coordinates of the background and object are calculated, the requirements of colour difference between adjacent pixels of the background and between adjacent pixels of object, noticeable for eyes are checked. The object contrast with reference to the background is calculated, at which the fine details are resolved by eyes, meanwhile the point object is considered recognized and its spatial coordinates of centre are fixed. Parameter of the image sharpness is estimated by count of total amount of the recognized blocks in percentage ration to the total number of the image pixels.

EFFECT: improvement of accuracy of focusing at shooting of small objects with low contrast.

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