John Baird and Philo Farnsworth made significant contributions to the development of television systems, each using different methods to obtain a visual input from radio waves. I'll provide a brief overview of their respective approaches.
- John Baird's Mechanical Television: John Baird's early television system, known as mechanical television, employed a rotating disc called a Nipkow disk. The Nipkow disk had a series of spiraling holes arranged in a pattern, and it was mounted on a motorized shaft. When the disc rotated, it scanned the scene in front of it through the holes, capturing the light intensity and converting it into a series of rapidly changing electrical signals.
These electrical signals were then amplified and transmitted as radio waves. At the receiver end, a similar Nipkow disk was used to recreate the scanning pattern. The received electrical signals were used to control the intensity of a neon lamp or a similar light source behind the Nipkow disk. As the disk rotated synchronously, the varying intensity of light passing through the holes reproduced the original image, which could be observed by the viewer.
- Philo Farnsworth's Electronic Television: Philo Farnsworth's television system, known as electronic television, utilized a completely different approach. Instead of mechanical scanning, Farnsworth's system relied on electronic components.
In Farnsworth's system, the scene to be transmitted was focused onto a specialized surface called an image dissector. The image dissector consisted of a photoelectric cell with a light-sensitive surface. When the focused light struck the surface, it generated a corresponding electrical signal that carried information about the intensity of light at each point.
The electrical signals from the image dissector were then processed and amplified. They were then transmitted as radio waves to the receiving end, where they were converted back into electrical signals and displayed on a cathode ray tube (CRT) or similar display device. The CRT used an electron beam to scan the screen and illuminate the appropriate pixels, creating a visual representation of the original scene.
Both Baird's mechanical television and Farnsworth's electronic television systems were important steps in the development of television technology. While Baird's mechanical approach was eventually phased out in favor of electronic systems due to their superior performance and reliability, both pioneers played crucial roles in shaping the early stages of television.