FIELD: physics.
SUBSTANCE: focusing device is moved in one extreme position and the image sharpness parametre for the given position of the focusing device is calculated. The calculated value of the sharpness parametre is taken as a preliminary maximum value of the sharpness parametre of the captured image. The preliminary maximum value of the sharpness parametre of the captured image is calculated through movement the focusing device from one extreme position to another through a step given when adjusting the focusing system, calculation of the current value of the image sharpness parametre, pair-wise comparison of the current value of the sharpness parametre with the preliminary maximum value. If the current value of the sharpness parametre is greater than the preliminary maximum value, the current value of the sharpness parametre is taken as the preliminary maximum value of the sharpness parametre of the captured image. The maximum value of the sharpness parametre of the captured image is determined after a preset number of steps for correcting the preliminary maximum value of the sharpness parametre of the captured image, where said number of steps is not less than one. For this purpose, the focusing device is moved to a position corresponding to the preliminary maximum value of the sharpness parametre. The step through which the focusing device is moved is reduced by a value defined during adjustment of the focusing system. The focusing system is moved by one step to the right or to the left from the preliminary maximum value. The current value of the sharpness parametre is calculated and compared with the preliminary maximum, and if it is greater than the preliminary maximum, the current value of the sharpness parametre is taken as the preliminary maximum value of the sharpness parametre of the captured image. The next correction step is carried out. Otherwise the focusing device is moved one step in the opposite direction from the preliminary maximum value of the sharpness parametre of the captured image. The current value of the sharpness parametre is calculated. The current value of the sharpness parametre is compared with the preliminary maximum. If is it greater than the preliminary maximum, the current value of the sharpness parametre is taken as the preliminary maximum value of the sharpness parametre of the captured image. Otherwise the next correction step is carried out.
EFFECT: more accurate focusing, mainly in such situations as capturing through glass, capturing on the background of a remote object or group of objects.
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