File:Spinning disk television projector 1931.jpg

English: A mechanical-scan television projector from 1931, for displaying a television image on a screen. It was a prototype made by De Forest Radio Co. in collaboration with Jenkins Television Corp. of Passaic, New Jersey. During the 1930s before modern technology was developed, many stations broadcast low-resolution experimental television programs using mechanical scanning devices. This device consists of a spinning disk pierced with a spiral pattern of holes called a Nipkow disk in front of a bright neon bulb called a "crater lamp". Each hole moving in front of the bulb created a spot of light sweeping across the screen to make a scan line, and the scan lines collectively created the picture. The video signal from the television receiver electronics was applied to the crater bulb, so the brightness of the spot at any point was proportional to the brightness of the image at that point. A problem with earlier "spinning disk" mechanical televisions was that so little light got through the holes that the image could only be about 2 inches square. The water-cooled crater bulb in this device was bright enough to project an image 2 feet square. The image on the screen in this picture is of course artificial.