| 摘要 |
Various edge detection arrangements are disclosed, including an edge detection method and arrangement that utilizes outputs of commonly illuminated reference and edge sensors as the inputs for a comparator. The reference sensor is configured to have a wide field of view and the edge sensor is configured to have a narrow, high gain, field of view. Therefore, the reference sensor has a broad signal response to an edge passage and the edge sensor a steep and narrow signal response. When the two signals are biased to cross each other, the comparator output changes state, indicating passage of an edge. Because the reference sensor provides a base signal level directly related to the real time illumination level that the edge sensor also receives, the reference sensor provides a switch point along the transition ramp of the edge sensor that integrates a majority of the random error sources.
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