Arrangement for recording images appearing on a cathode ray tube

Abstract

An arrangement for making a hard copy of a cathode ray tube display. Each horizontal line of a video signal is subdivided into a predetermined number of intervals. The amplitude of the video signal within each interval is digitized, and the digitized data, after being stored in a first-in-first-out shift register, is recorded on any desired recording medium, such as heat-sensitive or electro-sensitive paper. Each horizontal line is printed along a line on the paper, and the paper is advanced by one line when the next horizontal line of the video signal is ready to be recorded. The subdividing of each horizontal line is carried out by a phase-lock loop which functions as a frequency multiplier and provides a predetermined number of pulses for each horizontal sync pulse. Each horizontal line being processed is identified by a line counter to ensure that the horizontal lines of a frame are sequentially printed. The digitizing of the amplitude of the video signal permits printing of gray intensities of the video signal displayed on the cathode ray tube. A frequency-controlled oscillator provides image darkness by determining the duration of current applied to the printing element against the sensitive paper for recording the information taken from the shift register.