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Displaying SmartPhones: Mini-Projector Over iWear?

A smartphone has an incredibly tiny display screen, usually just a couple of inches across. It has to be small to fit onto such a tiny device, but still the tiny size of the display often makes a smartphone incredibly difficult to operate properly. For some years now, we have had one alternative, in the form of iWear HUDs – augmented reality displays that connect to the smartphone, and project a massive copy of the display over one eye.

A Vuzix iWear System

Now, a second option is on the cards. Rather than use an augmented reality display which only you can see, what about one which everybody can see? Project your phone's display screen onto any nearby surface so that everyone around you can see exactly what you are doing.

This solution is ideal for group work when you actually wish others to see what is on your phone screen, or when you are alone and it does not matter about the size versus comfort of use. However, when receiving text messages or instant messaging, conducting video chats or even surfing the web, do you really wish everyone around you to see exactly what you are doing, as you use the nearest wall, window display, pavement, or even the back of the person in front of you to display your screen?

Admittedly some very complex engineering has gone into this new display, created by researchers at the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena, Germany. However, like most AR displays, it is a specialised tool, not really appropriate for every situation.

Based loosely on seven year old virtual laser keyboard technology, the new screen display allows similar gesture-based interface control. Machine vision and projection are combined into one, with a scanning infra-red beam sweeping onto the projection surface area to detect moving objects (such as fingers) as they cross the projection area. This means the projection is every bit as much a touch-sensitive interface as the phone's screen itself. You can use either one to control the device. Of course this also means some random passer-by can operate your phone by jabbing their fingers at the projection on the wall, but as with every technology, there are situational downsides as well as upsides.

One of the prototypes installed on an iPhone, projecting the interactive display onto a table surface.

However, the similarity to the virtual laser keyboard ends with the haptic system. The projectors themselves are very different. Yes, themselves plural. The projector system was based on the compound eye of an insect, with hundreds of tiny microprojectors in an array, each of which is generating the complete image. These then overlap onto the projected surface, with the control hardware on the phone, altering the image each projects, to compensate for the angle it is projecting onto. In other words, it adapts intelligently to the angle relative to the phone that the display is projected onto. A display down onto a table will be shown the exact same way as a display onto a wall, even with the phone in the same orientation.

This is because the degree of alteration required of each projector in order to create a sharp overall picture is a function of the angle at which the image is projected, and the same infra-red scan that is used for haptic functions is very easily adapted to determine the precise angles of the surface being projected onto. At the moment it cannot handle bumpy surfaces, always assuming the surface is flat based on the angle data it receives back. However, this is more a by-product of limited computing power on the phone than anything else.

So long as the surface is smooth, the entire image displayed is crisp and clear – even if projected at a very flat angle with the beams striking the table surface at a diagonal. If it is bumpy, the image still displays but there is distortion between the projectors, and the image swiftly becomes too blurry to use properly around the areas that diverge in direction too far from the assumed slope of the plane. Using it somewhere like the edge of a table, or on a brick wall is horrible. In the middle of a table, or on a plastered or wallpapered wall is ideal.

In theory the same technology used in the compound projector array would work for much more advanced display systems such as virtual retinal displays as well, with admittedly greater computer power required to conform to the parabola of the retina. Still, the basic technology has much promise for this type of system, bringing things full circle back to personal display systems again – and immersive interfaces.

Each of the individual images is computed using software the researchers have developed: the position sensor and the smartphone‘s camera could deliver the geometric information, which the software uses to perform its calculations and compute the individual images along with their focus setting.

The optics were manufactured on wafers containing around 300 chips, each in turn housing 200 lenses for the microprojectors, and would respond favourably to mass production lithography.

It will still be another three or four years before the projectors appear on the market, as the new projection technology requires a high pixel density on the part of the digital imaging system, which is not currently standard. At the current rate of development in digital imaging for smartphones, the commercial model will be fully compatible within this time frame – again lowering implementation costs, since the hardware required will be standard anyway by that time.



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Mini-projector for smartphones

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