Mechanical TV

Over on hack-a-day I found an interesting article about mechanical TV.  How many people know that prior to the invention of the CRT television in the early 1930s, there were mechanical televisions that used a spinning wheel, drum, or vibrating mirror to create the scan lines?  Eckhard Etzold has built a modern day mechanical TV that uses a spinning wheel to produce the image shown at the right.

The wheel has holes in a spiral across the rim.   When the wheel is spun, each hole describes a curved scan line.  A light source behind the wheel is synchronized to the wheel.  For this TV a bank of RGB LEDs provides the light.  The LEDs are modulated by the video signal to draw each vertical scan line as the appropriate hole passes in front.

In a mechanical TV the wheel has to be much larger than the picture in order to avoid too much of a curved appearance.  The early mechanical TVs, which were replaced shortly after their debut by CRT models, had displays of a few inches.  Imagine the size and speed of a wheel that would be required to display a 42″ 1080p image!

Steve Ravet

EDN Gadgeteer