| 摘要 |
PURPOSE:To detect abnormality for only dust, etc., which is stuck fixedly by detecting the same value being obtained as position information on dust, etc., sticking on the optical system when a prescribed number of continuous bodies are scanned. CONSTITUTION:An image signal S1 obtained by a line sensor 4 is compared by a comparing circuit 11 with a reference level S2 and converted into a binary signal, which is supplied to a belt processing circuit 13 to mask a part which becomes a dark signal owing to a conveyor belt 1 with a mask signal S4. A position detecting circuit 5 for dust, etc., stores position information on the dark signal according to an image signal and updates it every time a scan is made to detect the position information on the dust, etc., sticking on the optical system. A continuity check means 16 inputs the position information from the detecting circuit 15 every time one body is scanned and counts the number of pieces of the same position information. A decision means 17 decides the sticking of the dust according to the counted number from the continuity check means 16. |
