| 摘要 |
PURPOSE:To eliminate the influence of variance of using environment to be inflicted on the titled device by sample-holding the floor brightness in using as the reference value for each scanning cycle of an image sensor, and comparing the holding value with the brightness of a reflecting table for detection of the boundary between the floor and the reflecting tape. CONSTITUTION:A floor detecting circuit 8 sample-holds the output of an image sensor corresponding to the floor brightness to output as the reference value. An edge deciding circuit 9 compares the present brightness value of the floor obtained by the circuit 8 with the video signal V outputted from the image sensor to binarize them into a part corresponding to the floor and a part corresponding to the reflecting tape. In such a way, said deciding action is performed based on the difference between the floor brightness and that of the reflecting tape obtained at the relevant time point. Thus it is possible to detect an edge with high accuracy despite the level of the signal V that is caused by the level difference of the floor surface is totally changed.
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