A see-through display is an electronic display that allows the user to see what is shown on the glass screen while still being able to see through it. It is a technology that has been around for a decade or two, but only as of 2012 was it being incorporated by companies such as Samsung, Planar Systems, and taptl into consumer products like handheld devices, televisions, and other technology as well as building materials such as glass. These screens can be used for augmented reality, a way of enhancing your view of the world with digital images overlaid onto real ones, and other applications such as shopping displays and more sophisticated computer screens.
MIT Researchers are working on creating Transparent Displays inexpensively using nano-particles.
How it works
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There are two major see-through display technologies, LCD and LED. The LCD technology is older, though OLED see-through displays are becoming more widely available. Both technologies are largely derivative from conventional display systems, but in see-through displays the difference between the absorptive nature of the LCD and emissive nature of the OLED gives them very different visual appearances. LCD systems impose a pattern of shading and colors on the background seen through the display, while OLED systems impose a glowing image pattern on the background.
LCD
Any LCD panel is by nature "see through," though conventional LCDs have relatively low transmission efficiency so that they tend to appear somewhat dark against natural light. Unlike LED see-through displays, LCD see-throughs do not produce their own light but only modulate ambient light. LCDs intended specifically for see-through displays are usually designed to have improved transmission efficiency. Small scale see-through LCDs have been commercially available for some time, but only recently have vendors begun to offer units with sizes comparable to LCD televisions and displays. Samsung released a specifically see-through designed 22-inch panel in 2011. As of 2016, they were being produced by Samsung, LG, and MMT, with a number of vendors offering products based on OEM systems from these manufacturers. An alternative approach to commercializing this technology is to offer conventional back-lit display systems without the back light system. LCD displays often also require removing a diffuser layer to adapt them for use as transparent displays.
The key limitation to see-through LCD efficiency is in the polarizing filters, which inherently limit the transmission efficiency for unpolarized light to 50% or less. Inexpensive polarizing films also have relatively low transmission efficiency, though commercial development efforts have had some success in improving it.
LED
LED screens have two layers of glass on both sides of a set of addressable LEDs. Both inorganic and organic (OLED) LEDs have been used for this purpose. The more flexible (literally and figuratively) OLEDs have generated more interest for this application, though as of July 2016 the only commercial manufacturer Samsung announced that the product would be discontinued. OLEDs consist of an emissive and conductive layer. Electrical impulses travel through the conductive layer and produce light at the emissive layer. This is different from LCDs in that OLEDs produce their own light, which produces a markedly different visual effect with a see-through display. The narrow gap between the pixels of the screen as well as the clear cathodes within allow the screens to be transparent. These types of screen have been notoriously difficult and expensive to produce in the past, but are now becoming more common as the method of manufacturing them is advancing.
Applications
Augmented reality
See-through screens are an emerging market that have several potential uses. Cell phones, tablets and other devices are starting to use this technology. It has an appealing appearance but more importantly it is also effective for augmented reality applications. The device can add its own twist to what is behind the screen. For example, if you look through a tablet with a see-through display at a street, the device could overlay the name of the street onto the screen. It could be similar to Google street view, except in real time. There is an app available for smart phones that allows the user to point the camera at a sign or writing in another language and it automatically displays the same view, but with the writing in the language of your choosing. This could be possible with see-through displays as well, but without the need for the camera. A device using a transparent display has much higher resolution and displays much more realistic augmented reality than video augmented reality, which takes video and adds its own supplement to it and then displays that onto the screen. It is much simpler to display the addition onto the see-through screen instead.
Retail
These displays are also used in shopping windows. The shopping windows show the product on the inside as well as show text or advertisements on the glass. For example, there could be a pair of shoes behind the window and at the same time the window has information scrolling across it like prices, special deals, or advertisement video clips. This type of showcase is becoming more popular as see-through screens are becoming cheaper and more available .
Current technology utilizing see-through displays
Samsung
Samsung has designed and marketed several see-through display products, the most notable being the Samsung Smart Window. The Smart Window is a transparent LCD meant to act as both a window and smart device capable of using apps and widgets, as well as connecting to the internet.
Planar Systems
Planar also develops display cases similar to Samsung for stores. In addition, they develop transparent displays for use in vehicles as heads-up displays that can show speed and other information such as alerting the user to incoming dangers more quickly and efficiently.
taptl
taptl develops, manufactures and sells transparent touch-screens. The touch-screens can be used as windows, kiosks, directories, "TVs," or computers for personal or business use. The technology is currently being marketed to the luxury interiors industry, including retail, yachts, aircraft, and homes. They are offered in sizes 5"-110", available in HD and UHD, and are environmentally sustainable, with endless applications.
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