How Did Those Early Home Theatre TVs Work?

[Jinx]

Do you recall those early home theatre TVs? They had three beams (of the three primary colors) projected onto a screen. But, how did they ever reproduce an image? How did this work? Was there a lot of distortion if you didn’t look at the screen head-on? And, why wasn’t this technology ever applied to the big screen?

• Jinx

[aaslatten]

I don’t know exactly how they worked, but I can tell you my stepdad’s Sony model was fairly worthless for the most part. You had to view it head-on for a decent picture, and it was a fairly grainy picture. Still, it was fun for the novelty of it.

[MrFantsyPants]

It consisted of a small TV, on the floor facing up, a fresnel lens and a mirror to focuse the picture on the screen. And a highly reflective screen, that only reflected the picture back to certain angles to maximize brightness.

[astro]

@MrFantsyPants

It consisted of a small TV, on the floor facing up, a fresnel lens and a mirror to focuse the picture on the screen. And a highly reflective screen, that only reflected the picture back to certain angles to maximize brightness.

I think he’s thinking of the earliest projection TV’s from the mid to late 70’s, not what you’re describing. IIRC keeping focus was a bear, brightness was low, they ran hot, and image quality (even for the 70’s) stank.

[How things work](CRT
Like conventional TVs, some projectors have smaller CRT tubes built into them. These tubes are small (perhaps 9-inch diagonal), expensive and extremely bright. In the basic layout, you have one or more CRT tubes that form the images. A lens in front of the CRT magnifies the image and projects it onto the screen. There are three CRT configurations used in CRT projectors:

One color CRT tube (red, blue, green phosphors) displays an image with one projection lens.

One black-and-white CRT with a rapidly rotating color filter wheel (red, green, blue filters) is placed between the CRT tube and the projection lens. The rapid succession of color images projected onto the screen forms an apparently single color image (the images are projected too quickly for your brain to distinguish between them).

Three CRT tubes (red, green, blue) with three lenses project the images. The lenses are aligned so that a single color image appears on the screen.
One of the problems with CRT projectors is that, with anywhere from one to three tubes and accompanying lenses and/or a filter wheel built in, the projectors can be quite heavy and large. Also, CRT devices do not have the fine resolution that LCD devices do, especially when projected.

)

CRT
Like conventional TVs, some projectors have smaller CRT tubes built into them. These tubes are small (perhaps 9-inch diagonal), expensive and extremely bright. In the basic layout, you have one or more CRT tubes that form the images. A lens in front of the CRT magnifies the image and projects it onto the screen. There are three CRT configurations used in CRT projectors:

One color CRT tube (red, blue, green phosphors) displays an image with one projection lens.

One black-and-white CRT with a rapidly rotating color filter wheel (red, green, blue filters) is placed between the CRT tube and the projection lens. The rapid succession of color images projected onto the screen forms an apparently single color image (the images are projected too quickly for your brain to distinguish between them).

Three CRT tubes (red, green, blue) with three lenses project the images. The lenses are aligned so that a single color image appears on the screen.
One of the problems with CRT projectors is that, with anywhere from one to three tubes and accompanying lenses and/or a filter wheel built in, the projectors can be quite heavy and large. Also, CRT devices do not have the fine resolution that LCD devices do, especially when projected.