PURPOSE: To eliminate the influence of jitter and to reduce the gradation error, by making the phase different by 180° between saw tooth waves in raster-scanned even lines and odd lines to extract a pulse width modulated digital signal.

CONSTITUTION: A signal (i) is supplied to a line counter 12 in every one line for original scanning, and logical "1" is generated for an odd line, and logical "0" is generated for an even line. A signal (n) (or m) is supplied to a saw tooth wave generator 4 from a frequency divider 3 through an AND circuit 14' (or 14) in accordance with the odd line (or even line), and a saw tooth wave (b) (or b') is supplied to a comparator 1. Since saw tooth waves (b) and b' are different in phase by 180°, gradation levels of picture elements in odd lines and even lines are extracted with phases shited from each other by 180°. Even if jitter is includ ed at the rise of the saw tooth wave (b) or b', it is hardly apparent as hard copy recording.