Fingerprint capture types
Techniques de capture d'empreintes digitales

Several ergonomics exist to acquire a fingerprint:

Plusieurs ergonomies existent pour acquérir une empreinte digitale:


Rolled finger / Doigt roulé

Rolled fingerprinting is only used in police application when using ink & paper. The main objective of rolling the finger is to get the whole fingerprint of the finger, from "nail to nail", in order to maximize the recognition rate.

La technique du doigt roulé n'est guère qu'employée par la police, avec la méthode de l'encre et du papier. Le principal objectif est d'obtenir l'empreinte digitale la plus complète possible, "d'ongle à ongle", afin d'avoir le maximum de chance d'identification.

Inked finger for rolled impression
Rolled finger

Static sensing / Capture statique

static sensing (!)

Static sensing is the most common method to read fingerprint: the user press without moving his/her finger on the sensor, which is necessarily the size of the finger.
Pro & cons of static sensing:

  • Obvious use: just put your finger on the sensor.
  • The user don't know what pressure to apply. It is generally necessary to press a little bit to make sure that a large area of the skin touches the sensor.
  • If the capture time is long, then the user has a natural tendancy to press more and more, which is not necessary most of the time, but may broke the sensor in worst cases.
  • If the user apply at the same time a rotation (which is never recommended), the skin plasticity makes a distorted image.
  • After a while, the sensor becomes dirty (especially on the edge) which may be a problem for the acquisition, and users may become reluctant to use it.
  • A latent fingerprint remains on the sensor: it is like leaving the key on the door...

La capture d'empreinte statique, où on pose le doigt sans bouger sur le capteur, est la méthode la plus courante. Le capteur est alors nécessairement de la taille du doigt.
Avantages/inconvénients de la capture statique:


Sweep (or swipe) reading / Capture à balayage

When using a silicon sensor, the cost of the sensor is directly linked to the silicon area. To reduce the cost, sweep sensing has been proposed (see my patent): the sensor has the shape of a small bar, and the user sweeps his/her finger over the bar. Small slices of fingerprint are collected, and the whole fingerprint information is available at lower cost.

Common pro/cons of sweep reading are:

More swipe sensors on a wafer than area sensors

Lorsque l'on utilise la technique des puces microélectronique (silicium), le prix du capteur est directement lié à la surface du capteur. Pour réduire les coûts, la technique du balayage a été proposée (voir mon brevet): le capteur a la forme d'une barrette, et l'utilisateur doit glisser son doigt à sa surface. De petites tranches d'empreintes sont collectées, et l'information contenue dans l'empreinte totale est alors disponible.

Les avantages et problèmes courants de la capture à balayage sont:

FingerChip fingerprint thermal sweep sensor

The very first commercial sweep sensor was the FingerChip using the thermal effect.

Le premier capteur à balayage commercialisé fût le FingerChip, utilisant un effet thermique.

History of sweep fingerprint sensors.
Image from 50 years of biometric research: Accomplishments, challenges, and opportunities
Anil K. Jain, Karthik Nandakumar, Arun Ross / Jan 2016.