How did SONY Make REAR SCREEN PROJECTION TV? (television technology history electronics VIDEO Japan)

SONY JAPAN: For discussion and comment, we look at a vintage tech documentary and compare how this may be done today. An inside look into SONY manufacturing of rear projection TVs, at SONY's Pittsburgh Pennsylvania factory (STCP = "SONY Technology Center Pittsburgh"). Film excerpt shows how Videoscope television screens are made at SONY's massive facility, of over 3.5 million square feet. Also mentions "American Video Glass," manufacturer of glass for televisions and computer monitors. See behind the scenes production facilities of these giant display screens. Also see the Display System Service Company opened by SONY to service display units. Provided for educational and historical comment only. Was this a viable technology?