Biometric verification is a technology that delivers accuracy, positive identification and fast throughput times … if the right devices are specified. However, the technology can also create frustration, delays and poor performance if installers and integrators get it wrong. HID Global has upgraded the performance of its V-Series readers, and that a benefit for those seeking to design biometric solutions.
Over the years, Benchmark has tested a wide range of biometrics devices and few have lived up to the hype. This is certainly true when it comes to fingerprint readers. Low cost readers (and some higher cost ones too) tend to utilise two dimensional scans, and whilst these work well in certain conditions, they tend to fail if fingers are damp, cold, dirty or damaged.
While many manufacturers will shrug their shoulders and declare that’s the way fingerprint scanners are, the reality is that’s simply not the case. Many years ago Benchmark worked with a manufacturer – Lumidigm – who created multispectral imaging technologies for biometric readers. During our tests we established that the readers worked with damp, dirty and dry digits, with some lightweight latex gloves, and to satisfy our curiosity we even fitted a reader which worked accurately and consistently under water. Think about that the next time you present a slightly damp finger and watch a reader fail!
Today Lumidigm is part of HID Global, and the company has announced important enhancements to its V-Series biometrics solutions. The developments include features that improve accuracy and interoperable image transfer of the product line while also quadrupling the image capture speed of the embedded sensors and modules.
This makes the biometrics solution ideal for faster user authentication requirements, such as for deployment at ATMs, authentication for medical dispensing and other applications where positive ID and quick throughput are essential.
The enhanced features of the V-Series include faster finger image capture offering improved usability while reducing user errors.
The problem with simple two-dimensional scanning is that the scan is merely creating an optical representation of the fingerprint.
Whenever Benchmark tests fingerprint readers, one challenge that the units always face is what we refer to as ‘the wet finger test’. Living in the UK, we have to accept that it can, on occasions, rain. This means people arriving at work or other sites with wet hands.
When a digit is placed on the sensor glass of an optical fingerprint reader, a slight pressure is applied. This usually highlights the ridges and grooves that form the fingerprint for an optical scan. This captures an image of the digit, from which points are plotted to map the fingerprint for the biometric template.
Now, if that finger is wet, when the slight pressure is applied against the sensor glass, the water spreads and fills the grooves that make up the fingerprint. The resultant scan shows little more than a solid dark blob, which gives the algorithm nothing to plot against to create a profile for template comparison.
It’s not only moisture that can cause this problem; dirt particles can also affect performance, as can damage to the skin or other injuries. To date, the use of a wet or dirty finger has created difficulties for every fingerprint reader that Benchmark has tested apart from those that use multispectral imaging.
Multispectral imaging scans using differing light frequencies to capture more than a simple image of a fingerprint pattern.
By using blue (430 nanometres), green (530 nanometres) and red (630 nanometres)light, as well as white light scans, the technology is able to capture differing aspects of the physiology of the registered digit. This is because the varying frequencies of light have different reflectance and refractance properties.
Because of this, each frequency of light discerns different information about the presented finger. It is possible to scan the skin surface – the epidermis – to obtain ridge and groove information.
Because the refraction and reflection of the varied light frequencies differs, multispectral imaging technology can also scan the dermis, the second layer of skin. Whilst the benefit of this might not be immediately obvious, the fingertips are literally riddled with tiny blood vessels. This is what makes touch so sensitive. You’ll be aware of these vessels if you’ve ever had a significant cut on a fingertip; it takes a long time to stop the bleeding!
These blood vessels mimic the ridges in the fingerprint; indeed, the ridges of a fingerprint conform to the dermal papillae. By scanning these, much information about the fingerprint can be gathered, even if the digit is applied to the sensor surface with high or low pressure, is dirty or wet, or even if the skin is damaged.
Multispectral imaging technology additionally has a degree of ‘fraud detection’ about it, as oxygenated blood has a different level of light absorbancy to non-oxygenated blood. This can be seen from the refractance, and prevents the use of various devices – including a removed finger – to gain access.
Whilst the background technology of multispectral imaging is indeed complex, the products that are using it are not. The benefit of the reader element is that it captures a clean and well defined fingerprint to use as a basis for biometric processing.
The good news for installers and integrators is that throughput times are now improved, making the technology more attractive for a wider range of applications.