Improved Methods of Controlling Carbon Arc Position
This paper shows, both from previous data and fundamental considerations, the close control of carbon position necessary to obtain constant light on the projection screen, particularly with reflector-type high-intensity carbon arc lamps. Review of the characteristics of this type of lamp and optical system reveals that in order to obtain constant light on the screen it is necessary to avoid variation of carbon position and changes in arc current due to line-voltage fluctuations. Methods of arc control employing photoelectric cells and bimetallic thermostats directly responsive to carbon position have been analyzed with regard to their applicability for this purpose. Some examples of these have been constructed and have demonstrated that automatic devices of simple construction are capable of maintaining constant the intensity, distribution, and color of the light on the projection screen.
- Print ISSN
- 0097-5834
- Published
- 1941-11
- Content type
- Original Research
- DOI
- 10.5594/J01247