The touch of the fingertip

Published in August 2004, “Twoja Komórka” nr 8/79

Mobile phones have become an inseparable companion of many people and are useful in more and more cases. However, it is increasingly necessary to ensure that they can only be used by an authorized person, i.e. only the owner of the phone.

These include, of course, functions such as paying for services, carrying out banking operations, access control and so on. All passwords, PINs and the like have many disadvantages - you can forget them, someone can steal them, and so on. It is worth noting that it would be best to equip the phone with the functions of recognizing authorized persons.

The chances of this increase and identifying a person from a fingerprint will soon cease to be fiction. Techniques allowing for such a solution have been developed by various companies for some time now. They hope that by means of voice analysis, appearance, iris pattern and above all fingerprints it will be possible to identify people reliably. There are many indications that the most practical will be the technique that allows for reliable recognition of fingerprints, which have been identifying their owners for over a hundred years without any doubt. Unfortunately, it is not easy to build a device that will do this as reliably as skilled dactyloscopic specialists.

Fingerprint patterns are not very contrasting, classic recognition methods do not cope with dirt, water and fats, which by nature occur on their surface. It is also not easy to unequivocally state whether the examined object is actually a finger - and also a living person. The solution, which can not only provide non-water identification of the phone user, but also add some interesting functions to the device, is being developed in Poland, in one of Wrocław's companies.

Its foundations were developed by Optel - it is an assumption, adopted as early as in 1986, that it is best to use ultrasound to recognize fingerprints. The realization of the device based on this idea was not easy - it requires mastering new solutions and many years of work. The result is a prototype device, protected by many patents, as well as a fairly advanced idea of what can be used in mobile phones.

The base will be a glass or plastic plate, on the edges of which the ultrasound transmitters and receivers will be placed. Under the plate there will be a screen, e.g. a liquid crystal screen. Besides, of course, you will need electronics that will fit into a few chips.

As you can easily imagine, the whole thing works on the following principle: applying anything to the surface of the glass plate changes the way the sound waves propagate inside it, which allows you to observe what comes into contact with it. It would be difficult to explain exactly how the device "feels" what is happening on its surface. However, it is worth to say in short that the ideas known from holography were used for this purpose, although in a completely unprecedented configuration, and the whole device is nothing else but a holographic acoustic camera - undoubtedly the only one of its kind.

The images produced by this camera reproduce the places that come into contact with the tile. So you can see the fingerprints of an applied finger, but of course you can also see where it is. This allows not only to recognize it, but also - by the way - to eliminate the keyboard (the whole tile is the equivalent of today's contact screens and may be a virtual keyboard). You can also, of course, put a pencil on the tile and see where it is located. Undoubtedly, you can also use it to write or draw, and the device will track its movement - similarly to the computer graphic tablets. This function can be used, e.g. to give a signature. However, something else is important to recognize the user: As the ultrasounds penetrate deep into the object, it is possible to determine whether it is a skin and not a gelatinous dummy, for example, and it is also easy to check whether it is the finger of a living person - because the blood flowing in it is noticeable. The marks left by the previously applied fingers - classic prints - are not visible at all. Ultrasounds, contrary to e.g. light, do not react to them.

A phone equipped with such a "sensitive disc" will not need a separate keyboard, because its surface will perform this function perfectly. This may allow you to significantly increase the screen area, which in some applications will be very useful, and also make it much easier to make the phone much more resistant to environmental influences than the current one (tight, with a uniform contour, etc.). Such a phone will have another interesting function: reading information, recorded in a similar way as nature offers in the form of fingerprints, i.e. as a flexible relief.

This can be used, for example, to read information on business cards, but also printed in books, magazines and all kinds of information. Such a function may turn out to be very convenient in many cases, because it is much simpler than taking a note and its carrier does not have to be more expensive than ordinary printing.