Technical Article

The ID ‘Card’ You Can’t Lose!

[picture of M22-ESA fingerprint reader] Do you want a convenient, dependable and inexpensive method for controlling access to buildings or for preventing unauthorised operation of machines and computers? Look no further than the ends of your fingers, says Paul Bennett of Moeller Electric.

The modern world is awash with PIN codes, passwords, ID cards and security passes, all of which are supposed to provide security with a minimum of inconvenience. But things often don't work out that way. When codes and passwords are forgotten, the inconvenience is anything but minimal. Also, codes and passwords are easily shared or copied, making their effectiveness questionable.

Cards and passes are no better. How many employee-hours are lost each year, for example, simply because people forget to bring their security pass to work? In addition, cards and passes are easily lost or stolen and, unless they're very sophisticated, they can be copied.

These shortcomings are the driving forces behind the growth of biometric security systems. For many, however, the very word biometric conjures up visions of complex systems that are difficult and expensive to install and operate.

It's true that if your system is for use at a border crossing and its objective is to protect your country against the entry of persons deemed undesirable, it will need significant investment. If your requirements are more modest, however, simple inexpensive solutions are available.

Biometric security is based on measuring some physical characteristic of a person which unambiguously identifies them. Options include, for example, facial recognition and iris scanning. The most popular choice, however, is fingerprint recognition.

Why is this? One reason is that it is well established that no two people, not even identical twins, share the same fingerprints. Another is that fingerprint recognition systems are readily accepted by users whereas not everyone would, for example, be comfortable with undergoing an iris scan every time they entered their office!

Another factor is cost. Fingerprint recognition systems that are reliable yet hard to defeat can be produced at a much lower cost than other types of biometric security device. That's not to say, however, that all fingerprint recognition systems are equal in these respects.

Some types, for example, use laser scanners, while others use electromagnetic waves to scan below the surface of the skin. These technologies are fine where the highest levels of security are needed but, for more routine applications, there's a better choice: thermal scanning.

Thermal fingerprint scanners use a line sensor which is a row of tiny individual temperature sensors. The user simply drags his or her finger across the sensor and it registers the time intervals between the different temperatures corresponding to the ridges and grooves of their fingerprint. In this way, the sensor generates a characteristic pattern which is unique to that person.

When a user is registered, their pattern is stored in the scanner. Subsequently, the pattern of anyone using the scanner is compared with all of the stored patterns and identification is confirmed only if a match is found.

Though simple in operation, this thermal system offers a high degree of security. If a mould were made of someone's fingerprint, for example, its thermal characteristics would be very different from that of a live finger. Defeating the system in this way is, therefore, virtually impossible.

So much for the theory, but what is a practical thermal fingerprint recognition unit like? Taking Moeller Electric's M22-ESA as an example, it has a slim fascia, which includes the scanner, and is about the same size as a pack of playing cards. Behind the panel on which the fascia is mounted is a control unit of similar size.

Wiring the unit is very simple. There are two terminals for a 24V DC supply, and three more terminals for the changeover contacts on an internal relay which shows when a fingerprint has been recognised.

Registering users is equally straightforward. A handheld programming device, or a PC with suitable software, is plugged in, and learn mode is selected. Persons to be registered pull their finger across the scanner three times, and their fingerprint is stored. After use, the programmer or PC is unplugged, and the fingerprint recognition unit operates as a standalone device.

This use of an external programmer has two benefits. The first is that it keeps down costs, as one programmer can be used for any number of recognition units. The second is that it adds an extra level of security, as no fingerprints can be added or deleted without the use of a programmer.

Despite their undeniable advantages, biometric security systems are rejected by many potential users because they believe them to be too costly and too expensive. As we have seen, however, modern fingerprint recognition systems eliminate these objections and make the benefits of biometrics available to all.

This page last updated: 8 March 2006