Si-OLED Technology for Smaller Display Modules

Si-OLED Technology for Smaller Display Modules

The sharp, clear augmented reality (AR) experience that smart glasses in Epson's Moverio series deliver is enabled by the tiny, 0.45-inch, high-definition silicon organic light-emitting diode (Si-OLED) displays found in a micro projection system. This micro projection system is an extension of the technology used in Epson's market-leading projectors. Read on to learn how Si-OLED displays are ushering in a new era of visual communication.

Microdisplays for smart glasses

BT-40

Microdisplays are a category of displays that have a screen size of around one inch (2.54 cm). Epson originally developed microdisplays primarily for projectors. Now, however, they are also used in Moverio smart glasses, in the emerging field of wearables.

Since Moverio headsets have a form factor that is very much like that of ordinary eyeglasses, the projection system had to be built into a very limited amount of space. The projection system in earlier models of Moverio used TFT liquid crystal displays. Beginning with the BT-300, however, we switched to an Si-OLED display, which provides exceptional brightness and a wide color gamut. At the same time, the display module was also made smaller and lighter.

Module miniaturized by using silicon-OLEDs

Smart glasses require complex optics that must be built into a very limited space and must also provide excellent image quality. The HTPS TFT LCDs used in early Moverio models, however, had issues in terms of the brightness, color gamut, field of view, and module size. Si-OLED displays enabled us to shrink the size of the modules yet still provide remarkable image quality. OLEDs are self-illuminating, so, unlike LCD panels, they do not need a backlight. Epson integrated the driver circuitry in the displays to shrink the area of the driving board and reduce the size of the display module. The displays used in the BT-40 are only 0.453 inches in size but can project high-definition images with 4,866 ppi and 1920 x 1080 pixels.

A smaller display module

Previous model BT-200

BT-200

Current model

Current model

Compact, lightweight display modules that deliver bright images with great color

The quality of images delivered by Moverio smart glasses improved dramatically because the Si-OLED displays can produce strong contrast.
Because see-through smart glasses with HTPS TFT LCD panels have lower contrast, a user sees AR images as if they are displayed in a rectangular window overlaid on the real world. This window then may become an obstacle in his/her field of view. To make the projected image blend naturally into the surroundings, the contrast of the image must be increased. HTPS TFT LCD panels have a backlight from which light would leak when rendering dark images, making the rectangular window visible.
On the other hand, since Si-OLEDs themselves emit light, they do not require a backlight and black can be expressed as black. Si-OLEDs can be controlled so that only the pixels that are needed to form the image emit light, while those in dark areas remain off. This enabled Epson to dramatically increase the contrast ratio from 230:1 on the BT-200 to 500,000:1 on the BT-300. Bright areas of an image are thus rendered brighter while dark areas are rendered darker, making the display frame invisible.

Field of view comparison (conceptual image)

Previous model BT-200

BT-200

A window is visible in the field of view

Current model

Current model

The AR image blends seamlessly
with the background so that window is invisible

Display movie subtitles and even increase the efficiency of work in the field

Moverio smart glasses are being used to deliver subtitles for the hearing impaired at movie theaters because they offer binocular see-through vision, can be used hands-free, and a natural-looking screen (without a rectangular window). Moverio Pro is a smart headset for enterprise applications that can be worn comfortably for long periods of time. Users can work hands-free while viewing information projected on-screen, receive instructions from remote support personnel as they work, and check work performed while work instructions are displayed in the field of view. These headsets can help improve the efficiency of factory and field work. They are even being used in agriculture, to enable elderly farmers to provide guidance to young people who are out working the fields.
Smaller, lighter display modules make it possible to view perceived big-screen images anywhere you want, stress-free, and enable video experiences you never dreamed of.

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