| 摘要 |
PURPOSE:To improve the using efficiency of a memory and to reduce the memory capacity, by dividing a direction X with every scanning line and comparing successively the X coordinates at the start and end points of a mask region with the X coordinates of an X coordinate means. CONSTITUTION:A horizontal synchronizing signal Hsync of a horizontal scan is supplied to a front-rear pulse generating circuit 10, and then a front pulse F is produced under the front edge of the circuit 10. This pulse F is sent to memories 1 and 2 respectively to read the rise point coordinates XRY1,1 of a mask region 1' of the memory 1 and the rise coordinates XRY1,1 of the region 1' stored in the memory 2. Then a rear pulse R is sent to latch circuits 3 and 4 respectively at the rear edge R of the signal Hsync to the latched there. A comparator 5 compares the coordinates XRY1,1 supplied from the latch 3 with the X coordinates from an X coordinate generator 7. A signal of a high level is delivered at a time point when the coincidence is obtained from the above-mentioned comparison. Then a mask output is generated. While a comparator 6 compares the coordinates XFY1,1 with the X coordinates and stops the mask output when the coincidence is obtaned. |
