The two main TV display technologies are liquid crystal displays (LCD) and organic light-emitting diode (OLED), and that isn't going to change any time soon. That's a bit of a problem, though, because in terms of contrast and black levels, OLED TVs are far superior than LCD.

Hisense is working on a way to level that playing field.

LCD vs. OLED

LCDs use backlight systems that cover the entire panel or individual sections of the panel, so when anything is lit up on the screen that light can bleed through; things that should be completely dark still emit some light.

OLEDs produce light on a per-pixel basis, so when they show something black, they can display perfect black. OLED panels are also far more expensive than LCDs, so if you want perfect black levels you need to be ready to shell out some cash.

We see some potential in Samsung's MicroLED technology, which also produces light for each individual pixel, but Samsung has been silent on the pricing and availability of any consumer MicroLED TVs.

ULED XD

Hisense's ULED XD technology could produce LCD TVs that offer near-OLED black levels. We first saw it in action at at CES 2019, and recently got a closer look at a more advanced version intended for consumers.

ULED XD addresses the LCD light-bleed problem by adding a second LCD layer. LCD TVs typically have a single LCD panel that produces the full picture, in color, illuminatd by a backlight system. ULED XD introduces a second, monochrome panel to more precisely control light output.

The monochrome LCD layer under the color LCD layer blocks light from pixels that are supposed to be dark, before they hit the color layer that produces the full picture. It effectively acts as a per-pixel light filter that controls brightness much more precisely than the zone-based backlight dimming of most other LCD TVs (LCD TVs without zone-based dimming simply brighten or darken the entire panel, producing very bright black levels).

The ULED XD concept Hisense showed at CES 2019 combined a 4K color LCD panel with a 1080p monochrome LCD panel, providing precise dimming in four-pixel blocks. Hisense has since improved the ULED XD design by incorporating a 4K monochrome panel that matches the resolution of the color panel, quadrupling the accuracy of the light control. The two panels work with a backlight system that Hisense says can reach over 1,000cd/m2 peak brightness, far exceeding the maximum light output of consumer OLED TVs.

The newest ULED XD concept is impressive. In a moderately lit room, blacks on the ULED XD TV appeared identical to blacks on an OLED TV. Since the monochrome LCD panel ultimately acts as a filter, light is still being emitted and can still bleed through, but not enough to be noticeable by the naked eye.

That would put the light output of the ULED XD concept at lower than about 0.005cd/m2, or the point where light is so low that the human eye ceases to effectively perceive color (called the scotopic vision threshold). For reference, we measure TVs only down to the hundredth of a nit, with a floor of 0.01cd/m2, and very rarely see LCD TVs hit that level.

Hisense's ULED XD TV concept shows a lot of potential as the OLED alternative we've been waiting for. You won't find it any time soon, however. Hisense doesn't plan to release a consumer ULED XD TV until 2020, and will only offer conventional single-panel LCD TVs for 2019.

Pricing for ULED XD TVs has not been announced, though Hisense says it will offer "significant value for the consumer" compared with similarly sized OLED TVs.

Further Reading

TV Reviews