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.
VOLUME I, No. 33
AUGUST 18, 1928
428
Movietone Pick-up System
OVIETONE projectionists will find the screw M holding the tube containing the slit immediately in front of the exciting lamp, sealed. This is for the reason that it, the slit, must be located with
such extreme ac| Optical System for Sound Pick-up |
form of a spot much in the same manner the light beam is made to cover the projector aperture. In the side of the slit barrel is a window through which the spot of light at the slit may be observed and adjusted by the projectionist.
As you will see by examining the
curacy that the projectionist would find great
difficulty in performing the operation. So accurate must this adjustment be, that it is made at the factory by means of a specially constructed microscope.
The slit is well protected. T he likelihood of any
thing getting into or upon it is extremely remote. Should you suspect anything of that sort to have happened—and it is possible, though, as I have said,
ConpenserR Sut Osu ECTIVE
Now the slit is very narrow.
diagram, the slit cell also carries an objective lens combination, the office of which is to project an image of the slit, in just the right proportion of reduction to the sound band of the tilm as it passes thru the sound gate.
It is scarcely more than a line itself, located in a horizontal, not a vertical position, and when its image is projected to the
sound band in still further reduced form, and in correspondingly greater brilliance, of course, it will illuminate each one of the film sound band lines separately, or very nearly so.
I think you get the idea, do you not? I might, however, add that the reduction is such that the slit image length is just a trifle less than that of the sound band lines.
Up to this point in re-reading what I have written, it seems as though I have succeeded in making the matter at least fairly clear. Now follow closely and we will proceed.
We now have a tiny, brilliant line of light, approximately the length and width of the sound lines upon the sound band of the film, incident upon the sound lines as they pass through the sound gate. It then follows that each of these lines is illuminated separately, or very nearly so, as it passes through the light line.
highly improbable—have the service man get on the job and examine it. It is strictly a service man job.
By way of explanaton, the light source is the straight coil filament of the exciting or “sound” lamp. As you all know, a point source of light would be ideal for motion picture projection, but as you also all know it cannot be used because it could not supply sufficient illumination. So also a line source—source having length but without appreciable width—would be ideal for an exciting lamp. That, too, is impossible, however, so in lieu thereof the slit is interposed, which gives us what amounts to a secondary light source in the form of a line of suitable length, having the light cut off cleanly and sharply by the two carefully adjusted knife edges which form its sides.
The light from the exciting lamp passes through a condenser, as you may see by examining the accompanying diagram, and is focused at the slit in the