Image: The Focus, December 1941 https://archive.org/details/focus171941181942sanf?q=%22Lite+Beam+Focuser%22
“In 1939, [James Caughey “Coy” Watson, Jr.] invented and manufactured the Coy Watson Lite Beam Focuser, a built-in camera device that assured accurate still camera focusing in total darkness. It’s believed this invention marked the first time a battery was ever placed in a camera.”
Excerpt from Associated Press obituary at http://archive.signalscv.com/archives/10797/ .
Coy was an actor, photographer and cinematographer with an interesting life. Click on the archive link to learn about him.