Rear-projection television

Newer technologies include DLP (reflective micromirror chip), LCD projectors, Laser TV and LCoS.

[2] The largest practical tube that could be made that was capable of being mounted horizontally in a television cabinet of acceptable depth was around nine inches.

Twelve inch tubes could be manufactured, but these were so long that they had to be mounted vertically and viewed via an angled mirror in the top of the cabinet.

[b] The principal driver for the British government's move was to establish cathode ray tube production facilities which it believed would be vital if the anticipated World War 2 was to materialise.

In 1937, both Philips and HMV put on display at the Radiolympia show in London, television sets that had a screen size of 25 inches based on the same MS11[c] Philips/Mullard[d] tube.

Unfortunately, both Philips and HMV had to withdraw their sets from exhibition by the afternoon of the first day as the cathode ray tubes had failed in both cases.

Customers who had purchased these sets were disappointed to discover that their tubes rarely lasted longer than a few weeks (bearing in mind that there was only one hour of television broadcasting each day).

By November 1937, Philips decided that it was more economic to buy the sets back rather than keep replacing tubes under warranty, which were becoming harder to source as the demand outstripped supply.

[5] This new tube was basically similar but had a larger cathode that required more heater power which was able to support a higher beam current.

The television set also had a smaller 21 inch screen which was roughly three quarters of the area of the previous year's model which meant that the tube did not have to be driven so hard.

Both models of the television had a problem in that the high accelerating voltage on the tube meant that it produced substantial X-radiation.

[k][12] Although the basic idea of the tube had not changed, it was smaller at just 2+1⁄2 inches and now featured a convex screen face, taking advantage of the intervening American developments.

[13] The difference was solely the position of the tube's screen relative to the concave mirror and the optical characteristic of the Schmidt lens.

This inconvenience was somewhat offset by the tube's relatively low price compared with the larger direct view versions, partly due to the quantities in which they had to be produced, plus the fact that they were fairly easy to replace.

Further: much simpler deflection systems had been developed that could generate the large currents required without consuming the power of earlier circuits.

Using the superior white phosphor of the post war period and higher accelerating voltages,[n] televisions were larger and brighter.

As television technology developed and picture quality improved, limitations in cathode ray tube sizes became an issue once again.

Modern color rear-projection television had become commercially available in the 1970s,[15][16][17] but at that time could not match the image sharpness of a direct-view CRT.

While popular in the early 2000s as an alternative to more expensive LCD and plasma flat panels despite increased bulk, the falling price and improvements to LCDs led to Sony, Philips, Toshiba and Hitachi dropping rear-projection TVs from their lineup.

The bulk of earlier rear-projection TVs meant that they cannot be wall-mounted, and while most consumers of flat-panels do not hang up their sets, the ability to do so is considered a key selling point.

Samsung exited the market by 2008, leaving Mitsubishi as the sole remaining manufacturer of RPTVs until it stopped in 2012 due to low profit margins and popularity.