| 摘要 |
An auto focusing mechanism is provided in a surveying instrument, such as an electronic level, that is capable of automatically focusing a telescope on a sighted staff. As a focusing lens ( 21 b) is moved by a motor ( 41 ) along the optical axis of a telescope ( 20 ), the image of a staff ( 1 ) sighted by the telescope ( 20 ) is converted into an electrical signal by a line sensor ( 24 ). The output signal of the line sensor ( 24 ) is converted into a digital signal by an A/D converter ( 27 ) and stored in a RAM ( 28 ). Based on the data stored in the RAM ( 28 ), a microcomputer ( 3 ) monitors frequencies of the component signals, or wavelets, contained in the output signal of the line sensor ( 24 ) stored in the RAM ( 28 ). When a particular frequency of the output signal associated with the position of the focusing lens ( 21 b) is detected a determination is made that the focusing lens ( 21 b) is located at a focusing position, and the distance from the telescope ( 20 ) to the staff ( 1 ) is calculated.
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