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. Principle of operation 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. Innovation Scophony's system used several innovative devices: A split horizontal and vertical focus optical system invented by Walton, developed specially for use with mirror scanning systems and the Jeffree cell. Light beams were focused by crossed cylindrical lenses, concentrating the light in two planes. This allowed the use of smaller lenses and mirrors, thus reducing size and cost. This was particularly important to Scophony since they intended to produce extremely large images. A light modulator developed by J.H. Jeffree in 1934 and known as the Jeffree cell, a cell filled with a transparent fluid which used mechanical oscillations to modulate the light