Prevent Undesired Side Views

Electronic Control of Display Viewing Angle

18. Juni 2018, 18:36 Uhr | Markus Haller
Neue Displays von Mobilgeräten, die die Seitenblick vom Mitlesern verhindern
New displays for mobile devices that prevent people from seeing from the side - in a simple way this time.
© fizkes – Shutterstock

Wide display viewing angles are not ideal for every situation. If you work with your laptop in public places, you should expect e.g., that the person sitting next to you will attempt to view your screen from the side. An easy-to-install device can prevent this in the future.

This kind of data espionage is called »Shoulder Surfing« in modern German. Unauthorized access to third party screens can easily put company secrets in the wrong hands – financial, personnel or technical. The vast majority of such cases go unnoticed. According to a study by 3M, this reduces productivity by 50%. What to do? Setting up a partition wall is not possible. Don't even turn on your laptop in such an environment? This may leave urgent work to be done.

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Controlling the Width of the Field of View

Das Prinzip von „sioShield“: ganz unten konventionelle Hinterleuchtung, darüber Kollimatorplatte zur Lichtausrichtung
Figure 1. The principle of »sioShield«: conventional backlighting at the very bottom, collimator plate for light alignment above, plate with scattering particles above, LEDs on the edges, LCD at the very top.
© siOptica

Years ago, display manufacturers came up with a lot of ideas to widen the viewing angle of LCDs. This is exactly what turns out to be a disadvantage in these cases. It would take a narrow angle here. However, returning to an older technology would not be a good solution, because sometimes you want to show something to several people on the screen. A variable viewing angle with at least two settings would be ideal: narrow for private use and wide for public use.

Countless inventors around the world have used their creativity to find practicable solutions. Up to now, all these devices have been more or less cumbersome to handle. For example, an optical disk structured with micro lamellas can be placed in front of it, allowing light to pass through only in one preferred direction.

When not in use, however, it must be removed and the user must stow it away when packing the laptop. Most products of this type absorb a lot of light, which is compensated by up-regulating the backlighting. This reduces the battery life. Overall, such and comparable solutions are not ideal.

The developers at siOptica in Jena have now found a promising principle. Using »sioShield«, the viewing angle can be electronically switched between narrow and wide, simply by pressing a button or by software. The basic idea has gone through a whole series of development stages, the latest version works as follows: Two additional optical elements are placed between the screen and the standard backlight unit. These are thin plates that only slightly increase the overall thickness (Fig. 1).

The lower plate contains a large number of tiny microprisms and thus acts as a collimator, which preferentially lets light through in the direction of the surface normal and reflects light running obliquely back to the source. The »Optical Lighting Film« from 3M, for example, can be used for this.

The second plate above it consists of a plastic with embedded microscopic scattering particles. White LED strips on the narrow sides couple in light, which is distributed more or less evenly in all directions. So the LCD has two different backlights. If the lower, conventional one is switched on, the light is strongly directed through the collimator plate and the viewing angle is narrow.

Unwanted side views are then no longer possible. The screen appears dark from a larger angle. If the upper one is switched on, the backlighting light is diffuse and thus the viewing angle is wide.

Figure 2 shows the effect. When looking straight ahead, there is practically no difference between the two operating modes; when looking obliquely (e.g. 45 °), the image is either clearly visible or black. A continuous transition between both modes of operation is also possible if both sources are mixed in an appropriate manner.

Infotainment for the Passenger

Die Wirkung: bei gerader Draufsicht kaum ein Unterschied zwischen beiden Betriebsarten, bei Schrägsicht entweder klar erkennbares Bild oder dunkel
Figure 2. The effect: with straight top view there is hardly any difference between the two operating modes, with a slanted view either a clearly visible image or dark.
© siOptica

There will be no shortage of applications. In addition to notebooks, the option is also relevant for ATMs and payment terminals to make it more difficult for unauthorized persons to secretly read the PIN.

In the automotive sector, it would be possible, with a limited viewing angle on the central display, to run a film to entertain the passenger that would not distract the driver while driving. For navigation, however, he should be able to see the screen. The changeover can be controlled automatically.

The limited viewing angle can also be  off-center, for instance turned  to the right for the passenger – by up to 30°. It can also be adjusted in horizontal and vertical directions - useful for ATMs where side view must be prevented, but visibility should be equally good for people of different height. Both can be achieved by suitable structuring of the collimator plate.

The two additional plates are only a few millimeters thick and can be installed in standard laptops without any major problems. Various patents have been granted or applied for; working designs are demonstrated at relevant trade fairs. Larger series production will start as soon as the East Asian laptop manufacturers have recognized this function as a convincing sales argument.

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