Bortz dot

From the first person who I heard use the term, a week or so ago. Minor edits have been made, for clarity, and my comments appear within []:

Back in the day the tightest beam available to lighting designers was a Beam Projector. This was way before aircraft landing lights.
So when aircraft landing lights became the norm in the late 70s and 80s, some designers were looking for the same beam definition provided by the previous (way heavy in weight and power hog heavy [I disagree with both characterizations]) beam projectors. Now if you remember how those lights worked, they had a vertical light source behind a small parabolic [spherical] reflector that was designed to sit at the appropriate distance from yet another opposing and much larger parabolic reflector. Rear reflection technology was the key, (I think it might have been from old light houses). So when aircraft landing lights became all the rage because of their limited power use in banks of four, eight, or ten, depending on the specific bottle [the low voltage is the reason for multiples, not limited power], people started slapping them into par cans at the appropriate diameter. We being purists to the art of lighting in Chicago, (think you have been there too) decided to try and find a way to remove the projected filament lines from the ACLs.
The answer was putting a piece of screen in the par can that would A) be a safety screen and B) be a mount for a fender washer or aluminum disk that would by being mounted on center at the appropriate focal range eliminate the filament lines. The light would be just as bright, yet a bit more defined, especially if viewed on TV. As far as the name Bortz, I was told that he was the original designer of the reflector/lamp holder, and the name kinda stuck with touring guys, kinda like Hod versus Loom for cables, etc....

Now this is the only person I've ever heard tell this story, so am awaiting third-party verification before offering it up as fact. At some point, the practice of affixing a washer to the ParCan's safety screen became obsolete, as the ACL lamp got its own mini-reflector or disc inside the lamp. On a Beam Projector, I have heard the black cylinder and black dot (later a small spherical reflector) referred to as "filament blockers." I have heard the small spherical reflector referred to as a "kickback reflector," prior to them being used in ERSs.

See also the thread What is a Bortz dot?.