|Re SED technology, in addition to the emitter erosion problem and potential burn-in, one issue I havenâ€™t seen brought up yet is the environmental/recycling issue re lead shielding â€“ the old CRT technology was vulnerable to stray magnetic fields (e.g. unshielded speaker drivers), but the lead shielding in CRT televisions and computer monitors is bad for the environment (i.e. landfills, ground water, etc.) While the electrons in SED technology only travel a small distance, one might speculate re the difficulty of engineering and manufacturing FCC-compliant consumer electron-spewing devices (especially large screen sizes) without substantial magnetic shielding.|
|CRT's have many other strikes against them. I'm only going to address the ones that will probably apply to SED's.
- Many contain lead to sheild the system.
- Need substantially thicker glass for the vaccum, hence weight.
- Color blooming.
- Suseptible to magnetic effects.
- Burn in is same as plasma.
|CRT's have many other strikes against them"
CRTs never offer:
* Perfect focus
* Perfect geometry
* Perfect convergence
Most of the limitations mentioned above donâ€™t apply to SEDs. Lead in the front glass of a CRT is used to shield soft xrays, which are a result of highly accelerated electrons smashing into the shadow mask. The distance from electron gun to front panel in a CRT is tens of inches vs. microns between emitters and front panel for SEDs, and therefore never accelerated anywhere near as fast. The reduced distance between emitters and front panel also means that a significantly lower HT voltage is used in SEDs, in the order of 10KV. Xrays are typically produced in bigger picture tubes requiring a HT voltage of 20KV or more. Also as there is no shadow mask in an SED display so there is nothing (at least metal) for the electrons to smash into.
There seems to be some confusion in the first post between magnetic shielding and EMI. Magnetic shielding is required to prevent the shadow mask from becoming magnetized resulting in color blotches on screen. Just as the Aluminum backing on the phosphors of a CRT collect the electrons for the return path, the same could equally apply to SEDs. Even if this were not the case it would seem relatively simple to add a transparent plastic conductive film over the glass to take care of EMI.
An SED display uses an emitter for each pixel sub-element (red, green, blue), and because there is no scanning in this type of display there is no chance, for instance, that the green electron beam can strike the red or blue phosphor dots. Therefore a shadow mask is not required.
It also seems reasonable that the vacuum required for an SED display does not pose any more mechanical loading on the front glass then the gasses required to fill each pixel on a plasma display.
Focus and convergence problems are exacerbated by the distance from the electron gun to the front screen. Focus becomes an issue because electrons of like (negative) charge want to repel each other and spread apart on the way to the screen. Similarly convergence issues result from the three different guns being in slightly different positions. As the beams scan, a correction factor must be applied to ensure all three shoot through the same hole in the shadow mask (hit the same pixel) at the same time. Any small angular error is amplified by the distance between electron gun and front screen. These issues would not manifest themselves in an SED display. Geometry for an SED is a manufacturing issue. I know that Rogo stated they are problems with regular CRTs but just wanted to clarify that these issues would not carry over to SEDs.
Other than price (of which I have no clue), we as consumers should be very excited about SED technology. This is an emissive technology that has the potential to eliminate many of the long-standing CRT deficiencies. I have not seen a display in real life but on spec these displays should produce a stunning picture.