| 摘要 |
A door obstacle sensor in which an optical transmitter and a receiver are located on the same side of an entranceway, and a retroreflector is placed on the opposite side. A controller measures the time of flight of a light beam that is reflected from the retroreflective target. All future target distances are compared to the initial distance, and a decision is made as to an object being present in or absent from the entranceway.
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