| 摘要 |
PURPOSE:To shield the correction position of a projected image with a white marker by attaching an auxiliary light source, which has the quantity of light matched to the quantity of projected light from an overhead projector (OHP), to an optical sensor which scans the surface of a white board. CONSTITUTION:Marker characters 4 and a projected optical image 5 exist together on the surface of a white board 1. If a correction position 6 is found on the projected optical image 5, the correction position 6 is hidden with the white marker having a proper density, and the hidden position is corrected with a marker of black or the like. When the surface of the white board is scanned with an optical senor 2, the image of only the black marker corrected on the white marker is picked up without picking up the image of the correction position 6 of the projected optical image 5 because the quantity of light of the auxiliary light source of the sensor 2 is matched to the quantity of light of the OHP.
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