Invention of Television: Philo Farnsworth's Television System

Topic

applied sciences

Frequently Asked Questions (FAQ)

What is the Farnsworth Television System? This invention, filed in 1927, describes a system for the electronic transmission of moving images, also known as television. It aims to overcome the limitations of previous mechanical television systems by utilizing a novel electronic scanning method.
What are the shortcomings of prior television systems? Previous television systems relied on mechanically moving parts to dissect and transmit images. These systems were slow, imprecise, and only capable of transmitting crude silhouettes, failing to capture the full range of light shades necessary for a true visual representation.
How does Farnsworth’s system address these limitations? Farnsworth’s system replaces mechanical scanning with electronic scanning. It utilizes a photoelectric cell to convert light from an image into an “electrical image”, an electronic discharge mirroring the light intensity of the original scene. This electrical image is then systematically scanned using a combination of electric shutters and oscillating electrical potentials applied to deflecting plates.
What is the role of the ‘electric shutter’? The electric shutter, with its small aperture, allows only electrons originating from a single elementary area of the photoelectric cell’s sensitive plate to reach the anode at any given time. This effectively isolates individual pixels of the image for sequential transmission.
How does the system achieve image scanning without mechanical parts? The system utilizes two sets of plates positioned around the electron path between the photoelectric cell’s cathode and anode. By applying alternating electrical potentials of different frequencies to these plates, the electron beam is deflected both horizontally and vertically, effectively scanning the entire sensitive plate within the optical period.
How is the electrical signal transmitted and received? The resulting “light current”, representing the scanned image, can be transmitted via wires or superimposed onto a wireless carrier wave. At the receiving end, the signal is amplified and used to modulate a constant light source.
How is the image reconstructed at the receiver? The modulated light is passed through a polarizer, a light rotator influenced by the received light current, and an analyzer. This process converts the electrical signal back into a fluctuating light beam. This beam is then projected onto a screen using two synchronized oscillographs operating at the same frequencies as the analyzing potentials used in the transmitter. This ensures the received light is correctly coordinated to reconstruct the original image.
What are the main advantages of the Farnsworth system? The Farnsworth system, by employing electronic scanning, eliminates the need for mechanically moving parts, leading to higher speed, accuracy, and the ability to capture and transmit the full range of light shades for a high-fidelity image. It also allows for a greater number of scanning lines, resulting in a more detailed and clearer image.

Significance

Understanding these findings helps advance our knowledge and inform better decisions. This research represents an important contribution to the field. For the full details, watch the video above and explore the linked resources.

Resources & Further Watching

Read the patent (US 1,773,980): https://patents.google.com/patent/US1773980A/

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