| 摘要 |
PURPOSE:To obtain the resolution equal to that of an A/D converting circuit, by providing a white level tracing circuit for calculating an upper-limit reference voltage and a black-level tracing circuit for calculating a lower-limit reference voltage, and controlling the upper and lower limits of a dynamic range. CONSTITUTION:Prior to a scan on an original picture, a scanning circuit 4 scans on a plate having reference white to store a white level envelope signal in a storage circuit 6 through a bus switching gate 5, and then scans on reference black while incident light is cut off to store a black level envelope signal in a storage circuit 7. A pseudo white signal H is specified by the white level tracing circuit 1 by specifying density in a density range close to white density stored in the original picture and supplied to the black level tracing circuit 2. The circuits 1 and 2 generate the upper-limit and lower-limit reference voltages by the stored values of the circuits 6 and 7 and supply them to an A/D converting circuit 3. Therefore, a scan 4 on the original picture is made to allow the circuit 3 to output a digital picture signal Ba according to a decision level between the upper-limit and lower-limit reference voltages, improving the picture quality of a reproduced picture. |
