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A simple guide to two-finger scanner

DATE
16/2/2022
Catagory
Biometric Post
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A simple guide to two-finger scanner

By Derek Lin, Marketing Manager, Aratek Biometrics

Most people are familiar with the single fingerprint scanner used in one-to-one verifications such as those found in IT systems, and the 4-4-2 ten-print scanner used in one-to-many applications such as police bookings and border control. Yet there is a lesser-known cousin of theirs that is also worth knowing— the two-finger scanner.

‍Also called dual fingerprint scanner, the two-finger scanner might be a bit more obscure, but it serves a unique purpose — to bridge the gap between single-finger scanners and the ten-print scanners, combining portability with high image quality. This, as we shall see later, makes it the perfect option for large-scale implementations.

In this guide, you’ll learn:

  • What is a two-finger scanner
  • The product certification for two-finger scanner
  • The real-world applications of two-finger scanner
  • The benefits of using two-finger scanner in large-scale applications

A two-finger dual fingerprint scanner
A two-finger dual fingerprint scanner

What is a two-finger scanner / dual fingerprint scanner?

As the name implies, a two-finger scanner, or dual fingerprint scanner normally comes with an optical fingerprint sensor and the sensing area that is large enough to capture two fingers simultaneously. The captured fingerprint image that comes with two finger simultaneous impression is called “two-finger flats”. Besides this, a two-finger scanner can also capture single finger flat and single rolled fingerprint (if it meets the FBI Appendix F Mobile ID FAP 45 requirements).

Compared with a single-finger scanner, a two-finger scanner, especially the FBI FAP 45 certified device has a significantly wider fingerprint image capture area and gives more fingerprint capturing options.

The two-finger scanner fingerprint capturing types: Single finger flat, Two finger flats & Single rolled fingerprint
The two-finger scanner fingerprint capturing types: Single finger flat, Two-finger flats & Single rolled fingerprint

The product certification for two-finger scanner: FBI requirements

Fingerprint image size and image quality are the most-used requirements for fingerprint scanner capabilities and fingerprint image quality in the biometrics industry. The FBI has developed a classification system based on ANSI/NIST-ITL standard of image quality according to compliance with the FBI's IAFIS/NGI Image Quality Specifications (IQS).

The table shows how FBI-certified fingerprint scanners are classified. The FBI-certified two-finger scanner is considered a Mobile ID FAP 45 fingerprint scanner if image quality passes the stringent test for Appendix F image quality requirements of the FBI Electronic Biometric Transmission Specification (EBTS) and is rated Mobile ID FAP 40 device if image quality only meets the lower-level PIV requirements.

The FBI image quality certification categories for two-finger scanner
The FBI image quality certification categories for two-finger scanner

No matter if the scanner is FAP 40 or FAP 45, the fingerprint sensing area of an FBI certified two-finger scanner should always be at least 1.6 x 1.5 inch, the minimum size for capturing two fingers simultaneously.

Besides capturing plain fingerprints, the FAP 45 certified two-finger scanner can also be allowed to capture rolled livescan fingerprints. Once a two-finger scanner is FBI FAP 45 certified, it will be rated for the FBI's IAFIS/NGI system and can be used in large-scale enrollment and identification programs.

The FBI EBTS Appendix F Mobile ID FAP 45 Certification for Aratek A800 fingerprint scanner
The FBI EBTS Appendix F Mobile ID FAP 45 certification

The real-world applications of two-finger scanner:

Unlike the FAP 40 fingerprint scanner which can only be used in one-to-one fingerprint verification, the FAP 45 two-finger scanner is suitable for both one-to-one (1:1) fingerprint verification and large scale one-to-many (1:N) matching operation.

For real-world applications, the FBI FAP 45 two-finger scanner is much more versatile. With its advanced Appendix F image quality and capability in supporting different capturing modes, users are finding a host of applications, especially at the large-scale level for the FAP 45 two-finger scanner:

  • Voter registration
  • Border control
  • Finance & banking
  • National ID
  • Law enforcement

to name a few.

Two-finger scanner application scenes

The benefits of using two-finger scanner in large-scale applications :

For large scale applications that require fingerprint recognition, the quality of enrollment and the accuracy of identification are the overriding concerns. Also, with operating environments subject to change without warning, remote deployments require a fingerprint scanner with portability.

The mobile ID FAP 45 certified two-finger scanner meets the higher Appendix F image quality requirements than FAP 10/20/30/40 scanners and has a device footprint that is much smaller than FAP 50 or FAP 60 ten-print scanners. These features put the FAP 45 two-finger scanner in a unique position to be deployed in large scale applications. The three standout benefits are as follows:

The FAP 45 two-finger scanner delivers high matching accuracy with a wide range of fingerprint capturing modes

The number of fingers used, and the image quality of the fingerprint captures are the two most important requirements to ensure the matching accuracy, while also considering system integrity and data interoperability. In the field, large scale programs that require fingerprint recognition commonly enroll multiple fingerprints or combine with additional biometrics like face or iris to ensure the accuracy.

So, how many fingerprints is enough? It depends on the specific requirements and resources. But the effectiveness of using two fingerprints as a starting point to improve matching accuracy is uncontested. According to NIST, as compared to only using single finger, fusing two fingerprints can result in a 48-90% reduction in false reject rate (FRR) at a constant false accept rate (FAR) of 0.0001, that means the True Accept Rate (TAR) and matching accuracy has been greatly improved.

The results of fusing fingerprint scores in various groupings of multiple fingers from NIST's Studies of Biometric Fusion
The results of fusing fingerprint scores in various groupings of multiple fingers from NIST's Studies of Biometric Fusion

NIST also indicates that using two fingers was about as accurate as using face plus single fingerprint (with variance based on finger position) and using two fingers plus face is more accurate than just using four-finger slap. Furthermore, using two fingers data can also minimize the possibility of finger sequence errors, this also helps to boost the accuracy.

In this regard, use of the FAP 45 two-finger scanner can deliver a relatively high level of matching accuracy in large-scale applications. With a wide range of capturing modes including: single finger flat, two finger flats, single rolled fingerprint, and even a 4-finger slap (via image-stitching but under limited conditions), the FAP 45 two-finger scanner does benefit the users to adopt multi-finger fusion or multi-biometrics methods for a better identification performance.

The FAP 45 two-finger scanner is portable and mobile

The environment for massive scale applications like voter registration, border control or remote banking can be challenging for both staff and users.

As the below images show, remote sites often have limited working spaces that need to accommodate a panoply of gears like laptops, scanners, cameras, printers, and extra batteries. Fingerprint scanners that take up the least real estate will be a most useful tool in such situations.

Embed from Getty Images

For the Appendix F certified scanner types, the FAP 45 two-finger scanner’s footprint is on average 30%~50% smaller than that of the 4-4-2 ten-print scanner, freeing up valuable space while also easily integrating into biometric registration kits or toolsets. The use of FAP 45 two-finger scanners in remote sites serves to unburden the staff, making them more productive and efficient, even as it ensures Appendix F high image quality in every capture.

The footprint size difference between two-print and ten-print fingerprint scanner
The footprint size difference between two-print and ten-print fingerprint scanner


The FAP 45 two-finger scanner delivers cost efficiency

Making large-scale applications cost efficiently is important. As far as the cost of FBI Appendix F certified fingerprint scanners go, the FAP 45 fingerprint scanner prices are way cheaper than the FAP 50 and FAP 60 4-4-2 ten-print scanners.

This makes the FAP 45 two-finger scanner ideal for those large-scale programs which, while requiring high fingerprint image quality, do not specify ten-print, and is a proven way to bring down cost without sacrificing image quality. (In fact, however, the FAP 45 two-finger scanner can still be used to enroll ten-print via image-stitching method but under limited conditions.)

Furthermore, if the FAP 45 two-finger scanner is water-proof and dust-proof (rated in IP65 or higher) like the Aratek A800, it could also be deployed for outdoor and heavy-duty use with minimal maintenance cost, further increasing cost-efficiency.

The wrap up for two-finger scanner

Compared to a single fingerprint scanner, the two-finger scanner or dual fingerprint scanner is a fingerprint capture device that features a larger sensing area (at least 1.6 x 1.5 inch) which can perform simultaneous capture of two fingers. It can also capture single finger flat and single rolled fingerprints, while providing more capture capabilities than a single fingerprint scanner.

The product certification for two-finger scanner would be FBI Mobile ID FAP 40 with PIV-071006 specification & Mobile ID FAP 45 with Appendix F specification. The FAP 45 certified two-finger scanner boasts of better accuracy than single fingerprint scanner making it ideal for various large-scale applications like voter registration, border control, finance & banking, national ID, and law enforcement, etc.

The use of FBI FAP 45 two-finger scanners benefits large-scale applications in three ways: it ensures high matching accuracy with a wide range of fingerprint capturing modes, its smaller footprint makes it more portable and mobile, and it achieves cost efficiency. Overall, the FBI FAP 45 two-finger scanner could be the perfect fingerprint solution for use in the field, it’s convenient and cost efficient while ensuring the high-level of accuracy.

About Aratek

Aratek is a global leader in the biometrics and securities industry. We are dedicated to providing cost-effective products and tailored solutions. We enable governments, educational institutions, banks, and many other industries to become increasingly efficient. With our sophisticated end-to-end product portfolio ranging from fingerprint modules, fingerprint scanners, biometric mobile terminals to facial recognition terminals, Aratek is here to provide real-world solutions to real-world problems.

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