We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
SOME TELEVISION DETAILS 651
constants of the optical system. Butyl bromide is the liquid used in the United States. Heptane has also been used. When there is no signal the light beam emerging from the valve is focused upon an opaque barrier which blocks it entirely and keeps it from reaching the theatre screen.
Built into the light valve is a small crystal which, like a crystal loud speaker, vibrates in accordance with the received signal. It imparts that vibration to the butyl bromide. A train of waves of compression sweep across the liquid at the frequency and intensity with which the crystal oscillates. Where the liquid is compressed by these waves its index of refraction is altered, the light beam is deflected accordingly, does not come to focus on the opaque barrier, consequently is not obstructed by that barrier and eventually reaches the theatre screen as a concentrated beam of light. The intensity of the light depends upon the degree of compression of the butyl bromide and therefore upon the volume of the received signal. The frequency with which the light is enabled to reach the theatre screen depends upon the frequency of the received signal.
(4) To cause the light beam to scan the screen there are two "mirror polygons," or wheels with mirrors set around their edges. One revolves horizontally and the other vertically. The former revolves more rapidly than the latter. It carries the light beam across one "line" of the theatre screen. Fly-back across occurs when the edge of one mirror passes beyond the beam limit and the edge of the next mirror comes into the beam.
'The horizontal mirror polygon, however, does not reflect the light beam to the theatre screen directly. It reflects it to one of the mirrors of the low speed mirror polygon which causes vertical scanning. From that mirror the beam is reflected to the theatre screen.
The motor of the low speed or vertical-scanning polygon is driven by the synchronizing impulses received from the transmitting station, those impulses having first been amplified to the point where they are strong enough to drive the motor. The motor of the high speed or