Nipkow disk

Can an entire image be seen one small hole at a time?

Spin the disk fast and watch.

You see the entire image, although you are actually only seeing one small portion of the image at a time.

You are seeing with your brain. Each hole passes over the image and the image is fed to your eyes point by point and line by line. Due to the afterimage phenomenon, you see a complete image; the visual perception of each part of the image remains in your brain for a sufficient period of time. Paul Nipkow patented this type of disk in Berlin in 1884. It can be used for mechanical scanning.

Nipkow’s invention was an important stepping stone for the development of television: Using light cells, the points visible through the disk can be transformed into an electric current and transmitted as ultrashort waves. The receiver converts the electric current back into visual dots, which shine with a different brightness depending on the intensity of the current, and they reproduce the transmitted image onscreen for viewing.