Bigscreen Beyond 2 Outsells Original in First Day, Surpassing Months of Beyond 1 Sales

TL;DR: microOLED and OLED panels are somewhat different technologies, with microOLED allowing more of the generated light to actually reach the eye thanks to the lightsource/filter/lens setup, making them usable with pancakes that in comparison to other lenses allow only a small fraction of the light to make it through.

Yes, OLED displays and microOLED are very different, they just both rely on organic (complex, carbon based) molecules as the light source. OLED panels are basically large sheets like LCD panels, only where LCD uses adjustable color filters in front of a white backlight, the OLED pixels themselves emit red, green and blue light. Unfortunately the organic elements are more fragile than semiconductor based LED, so you cannot crank them up to the same brightness, and they will degrade fast if always run at the highest power. So their max brightness is limited.

OLED also emit in all directions, while LCD sends light mostly forwards thanks to the backlight plus color filters in front setup. Usually this is a positive, giving OLED a much wider viewing angle, but it is a major disadvantage with pancake lenses, who are very inefficient due to using multiple internal reflections using polarization, losing about 90% of the light that enters the lens, compared to less than 15% loss in Fresnel/aspheric lenses.

microOLED work around that in several ways. They are for one much smaller, using OLED molecules directly placed on a silicon carrier. In all current microOLEDs these are white OLED that again have to pass through a color filter like on LCD, but while on LCD the filters also have to control brightness, which doesn't work perfectly, on microOLED the white backlight pixel can be turned completely off for max contrast. Like LCDs the microOLED is more directional thanks to the backlight/filter setup, so a lot more of the light makes it to the lens. And in addition microOLEDs place a tiny collimating lens in front of each pixel that focuses all the light directly into the pancake lens.

So while technically OLED panels and microOLEDs use the same technology to create light and each pixel isn't actually brighter, the specific setup of microOLEDs allows way more light to reach the eye in an HMD. There are other ways to make OLED brighter, for example current iPad Pros use tandem OLED, two OLED panels sandwiched together, increasing brightness and extending lifetime due to each panel being run at lower power.

And eMagin has been working on microOLEDs that don't use white OLED plus color filters, but directly emit RGB, in theory saving 2/3 of the energy that's wasted by first creating white light and then filtering out two colors. In reality different color (O)LED have very different efficiencies, with white LED being very efficient. eMagin created 4K direct RGB OLED prototypes that were very likely intended for Valve's Deckard, so this might become the first implementation.

And we need these and similar improvements, as even though microOLED work with the lossy pancakes, the image is still rather dim. In the Beyond 1 using 2.5K BEO microOLEDs this was compensated by the very tight light seal preventing light bleed, so it still looked bright enough. Apple worked around the problem in AVP by using Sony 3.5K microOLEDs that again use two stacked layers of OLED, increasing brightness, but significantly driving up the cost due to low yield. For the tech to become feasible in for example a mass market Quest 4, it will have to become both much brighter and cheaper first.