Touchless fingerprint sensors
Once again, as the name implies, there is no direct contact or interface, which is required by the end user. There are three specific types of touchless technologies:
- Reflection-based technology
This shines a light onto the physiological trait from different angles using just one type of camera. In this case (if fingerprint recognition is being used), the images from both the ridges and valleys are captured, unlike the full contact sensors. A primary disadvantage of this type of sensor technology is that the end user must keep his or her finger absolutely steady. Also, this technology must come into compliance with the best practices and standards as set forth by the FBI.
- Transmission-based technology
A special red light is shone through the physiological trait. With fingerprint recognition, this light is aimed towards the sides of the finger.
- Three dimensionally based technology
With this, either parametric modelling or nonparametric models are used. With the former, the raw images of the physiological trait are projected onto a cylindrical model. With the latter, mathematical algorithms are used to model the unique features of the physiological trait. As a result, much more granular detail can be captured.
Other types of sensors
There are also other types of sensor technologies which are available, but these are primarily used in facial recognition, and the behavioural-based biometric modalities. This includes:
Charge-coupled devices (CCDs) are cameras and can yield pictures of the face from surveillance video. The output can be black and white and even colour, and can also work with other spectrums of light, not just those in the visible light range. With CCD sensors, multiple images of the face are taken in a rapid-fire succession and then are compiled into one facial image from where the unique featured can be extracted.
- Active sensors
With this type of sensor technology, typically only one camera is used to take the various pictures of the face. A special light is then used to project a specific pattern (such as a geometric plane) onto the face. The differences captured from this special pattern allows for a 3-D image of the face to be constructed.
- Passive sensors
With this, multiple cameras are utilised, and the 3-D images of the face are then constructed through a process known as “triangulation.” Typically, in these scenarios, two calibrated cameras are used to take pictures of the face from the left to the right, and vice versa.
As it has been reviewed in this article, the biometric sensor is at the heart of any modality. Being that it is such a crucial component, it is very important that it is constantly monitored for any signs of physical damage, dirt issues, or even technological failures. The sensor must be maintained at an optimal performance level 24 X 7 X 365.
The trend is now to start using non-contactless sensors with all of the biometric modalities. This is not only convenient from the standpoint of deployment for the business or corporation, but also, it will help to greatly increase the user acceptance of it, primarily because of hygiene-related issues.
The technology behind biometric sensors is continuing to grow at a very rapid pace. There is strong movement within the biometrics industry to make them as miniature as possible so that they can be used on wireless devices and smartphones. In fact, Apple has already adopted the use of fingerprint recognition for their iPhone 5 and later models.
At the very bottom of the device, one can notice a circular object. This is, in fact, the fingerprint recognition sensor. To deploy this technology, Apple bought out a leading biometric sensor manufacturer known as “Authentic.” Apple has patented this technology and is planning to use it further in their other wireless devices as well.
Click here to read Part 1 of this series.