A D V E N T U R E S   in   C Y B E R S O U N D

Invisible Light, Noctovision - Infra Red Television in 1926

John Logie Baird, besides being the inventor behind the early television system used in the UK and, arguably, being the inventor of television itself, developed several advanced versions. He was able to demonstrate large-screen, colour and stereoscopic television in the 1920s and also developed a system for recording the images on disc ...Phonovision

Exactly 70 years ago he also demonstrated the use of infrared light as illumination for television and came up with a device he called a Noctovisor. Alexander Russell, writing in the February 5 1927 edition of Nature, described how he and W.R. Crookes were shown Noctovision in action at Baird's laboratory in London on December 23rd 1926

"One of us stayed in the sending room with a laboratory assistant in apparently complete darkness. In the receiving room, on another floor [of the building], the image of the assistant's head, and all the motions he made, could be readily followed."

Russell goes on to describe the images as...

"not so clearly defined as when visible rays were used, but we easily recognised the figures we saw, and made out their action"

lodge_nocto.gif

Baird prepares to ''Noctovise' Sir Oliver Lodge

The distinguished scientist Sir Oliver Lodge was successfully Noctovised at a meeting of the British Association held in Leeds in 1927. It is said that the demonstration of this equipment was so exciting that police had to be called in to regulate the queues of people wanting to see it.

By 1929, Baird had refined the system sufficiently for a demonstration of a self-contained infra-red viewer on Box Hill in Surrey on August 9th. The device (or one similar) is shown in the photograph below. A simulated fog made by viewing through a thin piece of ebonite (which is opaque to visible light) was used and the Noctovisor clearly showed lights which were invisible to the unaided eye.

Baird and assistant with the Noctovisor

Baird and assistant with the Noctovisor

The authors of the description of Baird's demonstration on Box Hill, written up in a 1931 book called Television: Today and Tomorrow, were clearly excited by the naval and military possibilities. They wanted this infrared technology to provide a capability for night and fog-bound vision that was, in reality, only achieved by RADAR during World War II. Whether the Noctovisor was what we would now call a Night Vision Scope using near infrared or a Thermal Imager using far infrared is unclear.

Baird's television system used a rotating mechanical disc with holes in it arranged to scan the light from a brightly-lit scene so that was 'seen' by a photo-electric cell. The 30 scan lines were vertical (this apparently looking better than a horizontal scan) and the picture was refreshed 12.5 times a second. The receiver (or monitor) had a lamp behind the scanning disc but otherwise the process just worked in reverse. An experimental broadcasting service using the London station of the BBC (call-sign 2LO) was inaugurated on September 30th 1929.

Unlike his rivals in the USA, Baird successfully synchronised the transmitted and received scans to achieve a stable picture without the motors at both ends being powered by the same synchronised AC power source. Unfortunately he was also wedded to mechanical scanning and eventually his system was replaced by the electronic, cathode-ray-based television we still make use of today.


Source: http://www.demon.co.uk/atsf/ilight/noctovision.html

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