Transparent Displays
T-OLED and TLM
Displays impress with their luminosity, high resolution and brilliant colors. They have one thing in common: when they are turned off, a black hole remains. You can't see through them. Transparent displays, on the other hand, are available in various technologies. Similar to a pair of glasses for augmented reality, it can allow you to see through to the workpiece on a machine or to the exhibits in a shop window, providing additional information about them.
The basic requirement for transparency is that the display technology allows light to pass through the panel. This is not the case with reflective TN such as in calculators or ePaper. The display can then hide individual segments (e.g. TFT) or add content (transparent OLED or transparent LED module).
Special attention must be paid to the design of the content. The color "black" does not exist - there the display is simply transparent and shows the background. To show off the transparency, the displayed content must consist of slim lines rather than large areas.
Viewing Distance and Pixel Pitch
Transparent displays have a special property: when the display is switched off, it can only be distinguished from its surroundings by a slightly darker tint. When switched on, however, it shines with bright colors. Large-format transparent displays are suitable for use in otherwise transparent window areas and provide valuable additional information about the outside world as “augmented reality”. This can be a system in industrial automation, a head-up display in a construction machine, timetable information in the subway or glazing in a museum that explains the exhibit.
Different technologies are suitable depending on the application and viewing distance.
Outdoor digital signage displays need to be large so they can be read from a distance. Displays such as wayfinding signs through the mall, on the other hand, need a low pixel pitch because they are viewed up close. The figure shows a relationship between the distance of the viewer and the necessary spacing of the pixels of a display. The y-axis shows the corresponding distance at the pitch given in the x-axis. Two conclusions can be drawn from this: To achieve the same impression as on the TV set, the pitch should not be larger, i.e. not below the straight line. To achieve the same impression, however, the pitch does not need to be finer either, i.e. it does not need to be above the straight line.
Whitepaper: Transparent Displays
TFT, T-OLED and TLM
Displays impress with their luminosity, high resolution and brilliant colors. They have one thing in common: when they are turned off, a black hole remains. You can't see through them. Transparent displays, on the other hand, are available in various technologies. Similar to a pair of glasses for augmented reality, it can allow you to see through to the workpiece on a machine or to the exhibits in a shop window while providing additional information about them.
The use cases are as varied as the technologies: shop windows for the presentation of goods, fronts of elevators or windows in building technology, "augmented reality" at the machine or safety through through-view in public areas.
Transparent OLED
The display with a view
OLED displays have their place where brilliant, bright colors and high contrast are required. They outperform LCD (TFT) in several ways: The colors are generated by actively light-emitting pixels, and not from the interaction of backlight and color filter as with TFT. If they are switched off, the pixel is black, whereas in TFTs a dark gray spot remains, which results from the transmission of the liquid crystal when the backlight is fully switched on. Only with local area dimming, where the brightness of the backlight is controlled depending on the image content, does the TFT catch up.
The new transparent OLED from LG Display brings another factor into play: transparency. This means that not only can bright images and information be displayed, but the background can also be included.
The illustration shows a simulation for a museum installation: while the object in the background is optimally illuminated and strongly protected against theft and vandalism, information can be displayed in the foreground.
The transparency of the OLED is about 40%. As a comparison, a conventional TFT is well below 10%.
The self-luminous display offers perfect picture quality. With Full HD resolution and a wide color gamut and simultaneous transparency for the world behind the display, it impresses every viewer. The electronics almost completely disappear: The surrounding frame is very slim and the control board is connected with a 3m long cable and can be mounted remotely. This also simplifies the assembly of several displays to a large screen.
Technical data
- Dimensions: 55"
- Display area: 1209.6 x 680.4 mm
- Resolution: Full HD = 1920 x 1080
- Color depth: 10 bit
- Refresh: 120 Hz
- Thickness (incl. cover glass): 5,7 mm
- Lifetime: 30.000 h
- Operating temperature: 0°C...+40 °C
- Brightness: 400 cd/m² (max)
- contrast: 150.000
- Dimensions: 30"
- Display area: 664,29 x 373,4 mm
- Resolution: HD = 1366x768
- Color depth: 10 bit
- Refresh: 120 Hz
- Thickness (without cover glass): 1,6 mm
- Lifetime: 30.000 h
- Operating temperature: 0°C...+45 °C
- Brightness: 350 cd/m²
- contrast: 135.000
The display controller can be controlled with HDMI or DisplayPort signals.
Transparent LED module
Vision with foresight
Passive matrix (PM) OLEDs are used for small-format displays. They achieve an astonishing level of brightness, which can exceed 1,000 cd/m². Customized designs are possible here, unlike with T-OLED. As structures can be very fine, they can also be used in the beam path of optical instruments or as head-up displays.
Multi-color LEDs can not only be used to build huge displays for outdoor use. If you mount them at a distance on a transparent film, you get a display that can not only be read from a great distance, but thanks to its transparency also allows you to see what is behind it.
The illustration shows an installation at the front of a café.
Features of the TLM
- Bright up to 3,500 cd/m²
- High transparency up to 85
- Transparent carrier film with adhesive layer for direct mounting on glass
- Lightweight and flexible
- Easy to string together
- Size can be adjusted by cutting the foil
Applications for transparent displays
In contrast to Asia, transparent displays have not yet gained widespread acceptance in Europe. Ideas for applications already exist:
- Functional discs: Partition panes to maintain hygienic distance (public authority, hotel, information desk, cab), partition panes of meeting rooms with controllable trans¬parency (for confidentiality), shading (e.g. skylight)
- Augmented reality, e.g. on the machine for visualization of problems, or in commercial vehicles
- Front sides of vending machines and freezers for viewing the product and simultaneously displaying information about it
- Showcases with explanation of the exhibits, e.g. luxury goods or museums
- Infotainment at product presentations, e.g. vehicle showroom
- Transport: information at bus and train stops: timetable and map; timetables and advertising in public transport vehicles
- Building technology: elevators with glass fronts, flanks of escalators, window fronts, transparent doors
- Digital signage: display windows of fast-food restaurants, shopping centers
- Security: guidance of flows of people where visibility must be guaranteed
Consulting and contact
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