How to Get HDTV Without Pixels
While most people who watch TV in HD do so on large LCD flatscreens, there are and have been a number of competing technologies. Perhaps the least common form of HD is with a CRT display.
How Does a CRT TV Work?
The first thing to understand is that CRT is an analog display technology. This means that it has a number of unique characteristics. One of the biggest factors is that it doesn't have a native resolution, unlike digital display panels. This means that the same display can show both 480i and 1080i images at their actual resolutions, not by interpolating from a single fixed resolution. A television's cathode ray tube consists of three main elements, all sealed within the vacuum of the picture tube.
- Electron Guns: A color TV such as a Sony Trinitron uses three electron guns to fire streams of charged particles at the screen, one beam for each of the three colors in a television picture.
- Magnets: Mounted inside the tube, between the electron guns and the back of the screen are a series of magnets that deflect the electron beams, so they can sweep across the tube to create the picture.
- Phosphor Coating: The inner layer of the tube is coated with phosphor dots which glow when hit with high velocity electrons. These dots lay down in patterns of three, one for each color.
What About HD?
What many people don't realize is that high definition TV isn't limited to widescreen LCD and plasma panels. You can also find CRT monitors with HD support and some even have HDMI inputs. One thing that you should be aware of is that every CRT TV has to have certain characteristics to meet NTSC analog video transmission standards:
- Interlacing: Early TV was limited in bandwidth, so the only way to transmit enough data for a stable image was to draw half the picture on each sweep. This led to the development of interlacing, where the system alternated transmitting odd and even lines; it relied on phosphor persistence to maintain a full-screen image.
- Scan Lines: One area where HDTV CRTs are popular is with retro gamers, partly due to the presence of scan lines. Many early generation video games only showed every second line, without going back and interlacing. These games generally work better on CRTs than digital TVs.
Using CRT Televisions
Even in a digital world there is something to be said for a large 34-inch class CRT HDTV. These Sony Trinitron models support 1080i resolution, taking advantage of the technology's contrast ratio and ability to deliver true blacks for a strong picture.