Scophony
Scophony was a sophisticated mechanical television system developed in Britain by Scophony Limited. A black and white image was produced by an early form of acousto-optic modulation of a bright light using a piezoelectric crystal and water or other transparent liquid column. The light modulator worked as follows. Crystal vibrations at one end of a horizontal water column would cause waves to propagate through the water. The light was passed through this column from the side across the waves as they propagated through the column, via separate horizontal and vertical orientated cylindrical lenses. The vibrations through the water  would act as a diffraction grating, the higher the amplitude, the more that the light passing through would be diffracted. The light passed through the water column was then horizontally focussed onto either a slit or narrow optical block, depending on whether positive or negative modulation of the water column was used. The amount of light which would either pass through the slit or go around the block depended on the amplitude of the modulation, thereby causing the light amplitude to be modulated. Following the slit/block, the light would hit the high speed horizontal rotating mirror drum which was  synchronised to the propagation of the waves through the water bath, in order that a particular wave in the water bath would appear at a fixed position on the screen, although that wave would actually be moving through the water column. This technique allowed significantly more of the light from the light source to be used compared to previous light modulation techniques. Vertical scanning was achieved by a separate much larger rotating mirror drum. It is a common misconception that the water column would contain a complete video line, but this was not necessary with the Scophony system. The company  Scophony Limited was established by entrepreneur Solomon Sagall in the early 1930s to exploit the patents of inventor George William Walton and William Stephenson. In 1932, Ferranti invested £3,500 in the company, however in 1934 Ferranti turned down the option to invest a further £10,000 to re-structure Scophony Limited, and in 1935 EKCO replaced Ferranti as the company's main investor. In 1938, the Scophony company demonstrated three types of 405 line mechanical television receivers at the Radiolympia exhibition in London: a home receiver, with a picture area of approximately and two systems intended for theater operation , one producing a image and the other a image. Several of the theatre systems were installed and operated successfully but none of the receivers were sold as production was halted due to the impending war. Scophony's system used several innovative devices: Scophony Limited operated as a television manufacturer in Britain up to WWII and then in the USA. During WWII Scophony moved to Somerset and worked on war work. "Of all the electro-mechanical television techniques invented and developed by the mid-1930s, the technology known as Scophony had no rival in terms of technical performance." In November 1948, Scophony  merged with John Logie Baird Ltd to become Scophony-Baird; offering for sale a line of four Baird-branded television sets the following year.