When was HD tv invented-?

Answer 1

HD technology has been in development for many years with HD equipment being available as far back as the early nineties.

There was no "invention" as such. The large broadcasting standards committees agreed a set of HD formats to be used in development and broadcasting manufacturers have used the agreed standards to develop hardware to support the standards.

One of the major hurdles of high definition was the transmission of the data stream to homes. The problem was overcome using digital compression techniques that allow video and audio data to be squeezed into a much lower data rate and still retain most of the detail that HD offers. This technique was one of the later developments in HD and paved the way for public broadcasts in HD to begin in the late 90s.

Answer 2

The HD tv was invented in the early 90s. It has been in gradual developments since then.