| 摘要 |
The invention relates to an autofocussing method, especially for telescopes pertaining to surveying equipment, said telescopes being fitted with image sensors which split the image signal into individual image elements (pixel), such as CCD lines and/or matrices and CMOS image sensors. Starting from the pixel lying closest to the optical axis, the local signal amplitude is calculated from the monotonously falling or rising signal to the next local maximum and minimum. As long as said local signal amplitude is substantially smaller than the maximum signal, and the focussing element pertaining to the telescope lens is in the focussing position for short target distances, said focussing element is displaced in large steps. The step distance is shortened according to the size of the local signal amplitude in relation to the maximum signal, and according to the position of the focussing element in the region of larger target distances. For a certain size of local signal amplitude in relation to the maximum signal, the cross-correlation functions (KKF) are formed respectively from certain pixels pertaining to the signal, and suitable comparison structures. For a particular relation between a reference function formed from the KKF, and the local signal amplitude, a step distance which is comparable with the optical depth of field is selected and focussed on the maximum of the KKF.
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