| 摘要 |
A distance judging system (S) includes at least two spaced apart marker devices (10) formed on a first object (12) and providing a signal (14). A viewer (A) is adapted to detect relative position of the signals (14) from the markers (10), and create an image (22) of the relative positions of the markers (10) within a field of view (16). A reticle (18) is superimposed on the field of view (16) of the viewer (A). The reticle (18) is selected to form a control area (20) within which simultaneous appearance of at least two images (22) of the markers (10) indicates that the first object (12) is at a distance (24) at least as great as a desired distance from the viewing apparatus (A); whereas, simultaneous appearance of less than two images (22) of the markers (10) within the control area (20) indicates that the first object (12) is at a distance (24) less than the desired distance.
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