Fingerprint sensing techniques

0920 2007

Biometrics Tech. and Application

Dr. Hsu, Wen-Hsing

Fingerprint sensing techniques Optical readers

Reflection Transmission Sweep, sweep with a roller Touchless TFT

Electro-optical readers Capacitance

Silicon chips TFT

RF field - AC capacitance Pressure

Resistive membrane on silicon, TFT Tactile MEMS Thermal Ultra-sound

Ink

Ink and paper are the tried-and-true way to take fingerprints, but technology has found ways to eliminate smudges and ink stains.

Optical readers Reflection

The oldest 'live-scan' readers use frustrated refraction over a glass prism (when the skin touches the glass, the light is not reflected but absorbed). The finger is illuminated from one side with a LED while the other side transmits the image through a lens to a camera. (FTIR: frustrated total internal reflection).

Optical readers -Reflection

Generally, one fingerprint is taken at a time, but some devices are able to acquire several fingers at a time. (Rolling Fingerprint)

Many companies are offering such devices, this is a common technology. .

Nagoya University uses a micro-collimator instead of the fiber optic, enabling direct fingerprint comparison.

Here is the example of the Compaq fingerprint reader (CMOS camera, around 2000).

Reflection with sweep

Kinetic Sciences and Cecrop/Sannaedle have proposed sweep optical sensors based on this principle. Cecrop seems to have abandonned this device

Kinetic Sciences Paper describing the sensor Cecrop/Sannaedle

Casio + Alps Electric uses a roller with the sensor inside. The roller acts like the prism.CasioAlps Electric

As well as Digital Persona with the Firefly Digital Persona Firefly

Reflection touchless TST removed the prism by dire

ctly reading the fingerprint, so the finger does not touch anything (but still need a guide to get the right optical distance). Thales (formerly Thomson-CSF) also proposed the same, but with the use of a special powder to put on the finger. The BERC lab from Yonsei University (Korea) also developped a touchless sensor (2004). (2005) TBS launch a touchless sensor with the "Surround Imaging".

Transmission

It is also possible to directly read the light transmitted by the finger.

Mitsubishi proposes to read the fingerprint with a regular camera.

NEC and Delsy (and Secom?) use a CMOS camera which is the size of the finger, with a fiber optic in-between, the light is coming from the edges in this case. Mitsumi & NEC proposes the same but with a sweep sensor.

Delsy NEC Mitsumi

In July 2005, NanoIdent unveils a flexible fingerprint sensor using polymer/organic photodetector.

TFT optical / TFT optique Philips replaces the CMOS sensor by a TFT display, used as sensor. Philips has also worked with Ethentica to combine their technologies, but without known product. LG has also studied a TFT sensor.

Other companies proposing TFT fingerprint sensors: Casio SiliconImageWorks Silicon Display Technology Alps Electric Mitsubishi Seiko/Epson

Electro-optical readers

A variant of TFT devices is the use of capacitance information instead of reflected light.

Some polymers are able to emit light when properly excited with the proper voltage (generally quite a high voltage is required. This polymer is directly contacting a CMOS camera, which is necessarily the size of the finger. Generally, the finger acts as the ground, and the polymer emits light where the ridges touch. Ethentica and TesTech propose such a solution.

Ethentica TesTech

Capacitance After optical sensing, the measurement of the capacitance between the skin and the pixel is the most

physical effect used to acquire fingerprints. Where there is a ridge or a valley, the distance varies, as does the capacitance. Because an electrical field is measured and the distance between the skin and the pixel must be very low to provide enough sensitivity, the coating must be as thin as possible (a few microns). A significant drawback is vulnerability to strong external electrical fields, the most dangerous being ESD (Electro-Static Discharge).

Silicon chips + capacitance

Silicon chips can be seen as a variant of the CMOS cameras: instead of using the light, another physical effect is used.

Companies proposing (or having proposed) capacitance sensing: Veridicom, Fujitsu, Infineon, Sony, Upek, LighTuning, Melfas, Atrua, NTT, Symwave, ...

Labs working (or having worked) on silicon capacitance sensors:

Seoul University A 600-dpi Capacitive Fingerprint Sensor C

hip and Image-Synthesis Technique (Lee & als, Seoul National University, 1998)

Kaist IML KAIST

NTT NTT Microsystem Integration Laboratories A Single-Chip Fingerprint Sensor and Identifier (

Shigematsu & als)

Capacitance + TFT

Flat panel technology rather than bulk silicon has been studied by Philips Korea and some others, using capacitive sensing. This is still at the laboratory stage.

A Capacitive Fingerprint Sensor with Low-Temperature Poly-Si TFTs Mitsubishi Electric Corp.

(April 2004) Alps Electric develops 2 fingerprint sensors. One is transparent, electrostatic (capacitive).

RF field - AC capacitance

Sometimes confused with capacitance sensing, the only common point between RF field sensing and capacitance sensing is the "capacitance" connection of the signal.

Companies proposing (or having proposed) RF/AC-capacitance sensing:

Authentec, Fingerprint Cards

Labs working (or having worked) on RF capacitance sensing:

Labs working (or having worked) on RF capacitance sensing: Validity / Philips Korea

An alternate solution consists in having connection through wires, so the finger is not mandatory directly in contact with the silicon part.

Validity

Pressure

This is one of the oldest ideas, because when you put your finger on something, you apply a pressure. Piezo-electric material has existed for years, but unfortunately, the sensitivity is very low. Moreover, when you add a protective coating, the resulting image is blurred because the relief of the fingerprint is smoothed. These problems have been solved, and now some devices using pressure sensing are available.

Several solutions, depending on the material, have been proposed: Conductive membrane on a CMOS silicon chip. Conductive membrane on TFT. Micro-electromechanical switches on silicon chip.

Conductive membrane on silicon

Opsis (a french company) offered a device using a conductive membrane deposited on a CMOS chip (July 1994).

Conductive membrane on TFT

Since 2002, BMF is offering a product using a TFT substrate (developed with Sanyo)

Fidelica offers since mid-2004 the FIS-3002, also using a TFT substrate from Sanyo.

(April 2004) Alps Electric develops 2 fingerprint sensors. One is based on pressure.

The Fraunhofer IKTS is working on 1-3 piezocomposites to create a fingerprint sensor (for CrossMatch, 2004).

Tactile MEMS

Micro electro-mechanical devices allow engineers to make extremely tiny silicon switches. When a ridge touches a switch, it closes. But the coating remains a significant problem, and moreover, a binary image is the result, leading to minimal information. No further development has been done with this technique beyond the laboratory.

NTT Microsystem Integration Laboratories

NTT research group

Michigan University (Wise)

Tima homepage N.Galy thesis page and the

thesis

• Leti, pressure sensors (Rey)

• LighTuning

Micron Technology: Tactile sensor using an insulated flexible matrix loaded with filler particles US 6,561,044

Thermal Pyro-electric material is able to convert changes in temperature into a specific voltage. This effect is quite large, and is used in infrared cameras. This type of sensor doesn't measure the difference of temperature between the skin in the ridges and valleys, because the difference is negligible. In fact, as the finger is directly placed on the material, the ridge's temperature is what's measured, as it's in contact. The valleys don't make contact, so the temperature of the pyro-electric material under the valleys remains almost unchanged. A drawback of the technique is that the image disappears quickly. When you place your finger on the sensor, there is a big change of temperature, and therefore signal, but after a short period (less than a tenth of a second), the image vanishes. The finger and the chip have reached thermal equilibrium, and as there is no change in temperature, there is no signal. This effect disappears when you sweep your finger over the sensor, because of the touch/no touch of ridge/valley.

Atmel (formerly Thomson-CSF) proposes the FingerChip Hunno Technologies & Hyung-Kew Lee (Korea, KAIST) have studied a thermal fingerprint s

ensor in 1999, probably using bolometers. Nagoya University has studied a thermal sensor based on MEMS, using a resistor to heat a

sensor above a cavity. INO (Institut National d'Optique / Canada) has used bolometers to make a 160x120 pixel fin

gerprint sensor (US patent 6,633,656). Bolometric FPA for fingerprint recording

Ultra-sound Ultra-sound fingerprint reading is not common. It may be seen as a kind

of echography. Ultra-sound sensing requires quite a big device with mechanical parts, and is quite expensive. Moreover, it takes a few seconds to grab an image. It is not suited for large production volumes at low cost. Its main advantage is the reading of the derma, the sub-surface of the skin, rather than the surface.

Ultrascan Optel is still at R & D stage

Surface impedance impediography (2004) CrossMatch is developping a fingerprint sensor based on piezo-electric pillars glued in teflon and covered with urethan, based on ultra-sound

Fingerprint: List of silicon sensors

List of fingerprint sensors / sensing area / JF Mainguet 2005 ( sweep sensor area sensor)

CompanySensing type

Brand TPart number

Releasedate

Res.

dpi

xpixel

ypixel

xmm

ymm

notes

Atmel formerlyThomson-CSF

thermal FingerChip

FC8x8 1997508

160

160

8.08.0

prototype

FC2x17 1997508

350

4017.

52.0

prototype

FC15A140

1998508

280

3014.

01.5

prototype

AT77C101B

2000508

280

814.

00.4

formerly FCD4B14

AT77C104

2004508

232

811.

60.4

navigation

AT77C105

2005

508

232

811.6

0.

4

navigation & low voltage I/Os

Alps

pressure - proto

2004 - - - - - -

optical TFT - proto

2004 - - - - - -

Alps/Casio optical roller - proto

2003 Feb 600 288 - 12.2 - sweep rolling tube

Atrua capacitive - ATW100

2002 363 192 8 13.5 0.6 Formely I-Control / ICS-3000

Authentec spin-offfrom Harris

RF modulation

FingerLoc

AF-S2

2000 May 250 128 128 13.0 13.0 -

AFS8500

2002 May 250 96 96 9.75 9.75 Discontinued.

AFS8600

2004 Jan 250 96 96 9.75 9.75 -

Entr壆ad

AES4000

2000 Sep 250 96 96 9.75 9.75 -

AES3500

2001 Oct 500 128 128 6.5 6.5 USB. Discontinued.

AES3400

2002 Sep 500 128 128 6.5 6.5 -

AES2500

2002 Nov 500 192 16 9.75 0.81 USB. Replaced by the AES2501.

AES2501

2003 Dec 500 192 16 9.75 0.81 USB

AES2502

2003 Dec 500 192 16 9.75 0.81 SSI

AES2510

2004 Jun 500 192 16 9.75 0.81 serial, 8 bit-parallel

1510 2005 Mar 500 128 8 6.4 0.4 4bit-parallel, master SSI

BMF pressure TFT -

BLP-100

2002 Feb 438 256 384 14.8 22.2 pixel pitch is 0.058mm (width/height not OK)

BLP-60

2003 508 192 192 9.6 9.6 Hitachi

Casio optical TFT

- proto 2004 Oct 423 368 368 22.08 22.08 demonstrated over a LCD display / CEATEC 2004

- proto 2004 500 200 240 10.0 12.0 Backlight

Delsy optical trans.

-CMOS

2001 508 288 384 12 18

Discontinued?

- CCD 2001 - 512 576 - -

Digital Persona optical roller FireFly Firefly

2003 May 600 345 - 14.5 - 600dpi max (500dpi sweep dir.) depends on speed.

Ethentica electro-optical TactileSenseT-FPM

2001 403 225 306 14.2 19.3 Formerly Who?Vision

Fidelica pressure -FIS-3002

2004 Feb 508 256 256 12.8 12.8 -

Fingerprint Cards activecapacitive

-

FPC1010

2002 363 152 200 10.6 14.0 FPC1011

FPC1030

2002 363 152 32 10.6 2.2 FPC1031

Fujitsu capacitive -

MBF110

2001 500 300 300 15.0 15.0 (= Veridicom FPS110)

MBF200

2001 500 256 300 12.8 15.0 USB. (= Veridicom FPS200)

MBF300

2002 Mar 500 256 32 12.8 1.7 Discontinued.

MBF310

2003 Jul 500 218 8 10.9 0.4 Replaces the MBF300.

Idex AC capacitive SmartFinger - 2000 500 256 - 12.8 - Sweep 1 line. Non-active pixels on silicon.

Infineon capacitive FingerTipFTF 1100

2000 513 224 288 11.1 14.3 Discontinued in 2004.

INO thermal - FPA 2003 Sep 488 160 120 8.3 6.2 Bolometers

KAIST univ. capacitive

- proto 2002 500 210 100 10.5 5.0 -

- proto 2005 462 200 160 11.0 8.8 integrated processor for recognition.

KSI / Cecrop optical sweep - - 2000 900 - 3 19.1 - -

Leti MEMS pressure - proto 2002 391 92 92 6.0 6.0 -

LighTuning

capacitive - LTT C300

2003 313 192 128 15.4 10.3 -

capacitive - LTT C500

2003 500 236 192 11.8 9.6 -

capacitive - LTT S500

2004 Oct 500 200 16 10 0.8 sweep-type

LG-Philips optical TFT FingerTalk proto 2000 300 240 256 20.1 26.8 backlight

Melfas capacitive - MFCS1000

- 400 150 - 9.6 - -

Michigan univ. tactile - proto - 500 16 16 0.8 0.8 -

Mitsubishi

Optical TFT - proto 2003 feb 423 250 320 15.0 19.2 -

capacitive TFT - proto 2003 Feb 423 250 320 15.0 19.2 -

optical trans. - R&D 2003 - - - - - -

Mitsumi optical - SEF-A1

2005 jun 600 256 - 10.8 - Proto shown May 2004.

NanoIdent photo-organic - proto 2005 250 256 256 - - (announced resolution is likely an error)

NEC optical trans. FingerThrough SA301-10

2002 Oct 800 480 540 15 18 (approximative values)

Fingerprint sweep sensing

Fingerprint sweep (or swipe) sensors is a subcategory of fingerprint sensors, useful because of its lower cost production compared to static (or area) sensors.

History of fingerprint sweep sensors 1997 May: Thomson-CSF (now Atmel) demonstrated the FingerChip FC2x17, at the CTST'97. 1998 May: Thomson-CSF demonstrated the FingerChip FC15A140. May: Seoul University submits a paper about a capacitance swipe sensor (published April '99). July: First prototype from Idex on its first sweep sensor. 1999 May: Sannaedle / Cecrop demonstrates MyFin, a swipe optical reader. May: Kinetic Sciences demonstrates the KC-901 at the CTCT. 2000 May: Atmel unveils the FingerChip AT77C101. May: Kinetic Sciences demonstrates a new version of their swipe optical sensor (K-1000?).

2001 April: Idex & STm announce the development of SmartFinger. Sept: Fingerprint Cards announces the FCP1030. Nov: Citizen & IBM shows the WatchPad, the first watch with a built-in fingerprint reader, the FingerChip. 2002 Feb: Fujitsu announces the MBF300, and shows it at the CTST in May. Summer: Tima publishes about a sweep tactile sensor. Oct: I-Control promotes the ICS3000 / PDS3000 Nov: Authentec introduces the AES2500. Nov: The HP iPAQ h5450 is the first PDA with a built-in fingerprint sensor, the FingerChip AT77C101 from Atmel. Nov: STm unveils a TouchStrip prototype at the COMDEX. 2003 Feb: Alps Electrics + Casio unveiled their "rolling-tube head" scanner. March: STm displays the TouchStrip on the web. May: Digital Persona unveils the Firefly, a sweep optical fingerprint sensor using a roller. Jul: Sharp announces the Mebius Muramasa, the first Tablet PC with a build-in sweep fingerprint sensor, the FingerChip. Jul: Fujitsu announces the MBF310. Sept: Melfas announces the MFCS1000. Oct: YRP shows the Ubiquitous Communicator, a R&D study prototype, containing the Atrua sweep sensor. Nov: Elsafe installs the first safe with a sweep fingerprint reader, the FingerChip. 2004 Feb: I-Control becomes Atrua and promotes "Atrua Wings" (ATW100). Feb: Atmel announces the AT77C104, the FingerChip with integrated navigation. Feb: Atmel announces the colored FingerChip. Feb: The Fujitsu F900i cell phone contains the Authentec AES2500. (Japan only) March: Upek becomes a spin-off from STm. March: Fingerprint Cards announces the FPC1031B. March: Validity unveils the VFS101 (USB), VFS131 (SPI) & FVS161 (LPC) (RF Fingerprint imaging on flexible tape) March: Ritech announces the BioSlimDisk iCool containing the Upek TouchStrip. March: Trek announces Thumdrive Swipe containing the Upek TouchStrip (to check). April: Fujitsu announces the LOOX T series notebooks (t50H & T70H) with the Authentec AES2500. April: Motion Computing announces the M1400 tablet PC with the Authentec AES2500. April: MPC unveils the Transport X3000 with the Upek TouchStrip. May: The Fujitsu F506i cell phone contains the Upek TouchStrip. (Japan only) June: The F900it is the same as F900i, but with a twist screen. June: The Gateway notebook 450XL contains the Upek TouchStrip. June: Authentec announces the AES2510, a swipe sensor + navigation, available mid-June, $6. July: The Fujitsu P7000 laptop containing the Authentec AES2500 is released. Very close from the Loox T series (the same?). July: Texas Instrument release a DSP development board + Fingerprint Cards FPC1031. The FingerChip is scheduled 04Q3 July: A prototype of the Hitachi G1000 PDA phone containing the Atrua sensor is demonstrated in Japan. August: The Pantech GI100 cellphone containing the Fujitsu MBF310 swipe sensor is announced. August: LG releases the LG-LP3800 cameraphone containing the Authentec AES2500. August: Validity unveils more info about Chip-On-Film, Module, kits... Sep: A Lexar flash disk containing the Fujitsu MBF310 swipe sensor is released. Sep: YRP shows a new release of the new Ubiquitous Communicator (Atrua sweep sensor?) Oct: LighTuning announces the LTT-S500, a capacitance swipe sensor. Nov: Jstac's Victoria 125, 126, 115, 116 hard drive with LightTuning sweep sensor. Nov: The HP iPAQ hx2750 featuring the Atmel FingerChip AT77C104B is released. Dec: NEC unveiled a sweep sensor prototype. Dec: Linpo announces a flash disk with the S500 sensor from LightTuning. Dec: The F901iC cell phone contains the Authentec swipe sensor.

2005 Jan: Bionopoly unveilsBio-USB flash drive & Fingerprint Passcode Generator

using the Atmel FingerChip. Feb: IBM announces a keyboard (and peripheral) with a swipe sensor. Feb: Atmel releases the FingerChip AT77C105 Feb: Yulong announces the Coolpad 858F GSM with the Atrua swipe fingerpri

nt sensor. March: Authentec unveils the Entr壆 ad 1510, a swipe sensor + navigation, $

5. March: Sandisk unveils the Cruzer?Profile USB drive (using the Upek swipe s

ensor?). March: IRevo introduces the Gateman MB740 door lock using the Atmel Finge

rChip March: Atrua announces the ATW200. No photo. March: G&D unveils the StarSign Bio Token containing the FingerChip sweep

sensor.

March: The Fujitsu Stylistic ST5022 Tablet PC with the Authentec swipe sensor. April: IBM unveils the ThinkPad X41 with the TouchStrip from Upek. April: LG releases the LG-LP3550 cameraphone containing the Authentec AES2500. April: Scandinavian Ecotechnologies presents a biometric card with an embedded swipe sensor likely from Fingerprint Cards. April: Toshiba introduces the Libretto U100 with the Authentec AES2500. April: Toshiba introduces the Portege R200 = the Dynabook SS SX/190 with the Authentec AES2500. April: Tychi unveils the BioKnob (door knob) April: MPC's Transport X3100 with the sweep-type Upek TouchStrip. May: Ritech unveils the iDEA containing the Upek TouchStrip. May: Ritech unveils the BioMouse with the Upek TouchStrip. May: Motion Computing announces the M1600 tablet PC with the Authentec AES2500. May: Fujitsu LifeBook S6240, S7020 & S7021 / B6000 with the Authentec swipe sensor. June: IBM unveils the ThinkPad X41 Tablet with the TouchStrip from Upek. June: Aratek Fingo Mouse / Fingo Reader / Fingo Lock using a swipe sensor from Authentec. June: NEC Versa C250/M350/P550 with the Upek TouchStrip sweep sensor June: LaCie unveils the SAFE Mobile Hard Drive using a Upek TouchStrip sensor. June: HP nx6125 laptop with an Authentec 2501 swipe sensor. June: Mitsumi announces an optical sweep fingerprint sensor, the SEF-A1 July: The Pantech & Curitel PT-K1200 cellphone containing an Authentec swipe sensor is unveiled. July: Motion Computing unveils the LS800 A5 tablet PC with the Authentec AES2501. July: Card Media announces the Storeguard with the AUthentec swipe sensor. July: MPC's Transport T3100 with the Upek TouchStrip. Aug: Fujitsu LifeBook P1500 with the Authentec swipe sensor. Aug: More info about the Symwave capacitance sweep fingerprint sensor SW-6888 Aug: The Fujitsu Stylistic ST5032 Tablet PC with the Authentec swipe sensor. Aug: Sony announces the Vaio BX series with the Upek swipe sensor. Aug: The Lenovo ThinkPad R52 now offers a Upek fingerprint sensor (as an option). Sep: Itronix announces the GoBook?VR-1 with the Upek swipe sensor. Sep: Lenovo unveils the ThinkPad Z60m & Z60t with the Upek swipe sensor. Sep: Toshiba announces the Tecra S3 M740 & M780 Sep: Willcom unveil a cellphone proto using the Fujitsu swipe fingerprint sensor. Sep: HP released the HP iPAQ hx2790 with Windows Mobile 5.0 with the Atmel FingerChip. Oct: Fujitsu Lifebook FMV P8210, T8210 & TB12 Tablet PCs with the Authentec swipe sensor. Oct: Sony introduces the Vaio AX series (VGN-AX570G) with the Upek swipe sensor. Oct: Samsung unveils the SCH S370 cellphone using the Authentec swipe sensor. Oct: Amoi announces the M606, M616 and A717 notebook PCs with the Upek swipe sensor. Oct: Medion introduces the MD 96500 notebook PC with the Authentec EntrePad 2501A swipe sensor. Oct: The F902i cell phone contains the Authentec swipe sensor. Nov: The Fujitsu P7120 laptop containing the Authentec AES2500 is released.

Atmel

· Official homepage of the FingerChip: Atmel website

See also the (local) FingerChip products page for more information.

Seoul University · A 600-dpi Capacitive F

ingerprint Sensor Chip and Image-Synthesis Technique (Lee & als, Seoul National University, 1998)

Idex · Homepage: Idex · (1998) IFF120: first swe

ep active AC capacitance sensing prototype, started with Sintef.

· (2001) SmartFinger©: development with ST.

SmartFinger© IFF 120

Sannaedle / Cecrop / Kinetic Sciences Homepage: Cecrop/Sannaedle. Homepage: Kinetic Sciences (KSI). In 1999, Sannaedle (now Cecrop) offered a device called MyFin. At the same time, KSI offered the KC-901, which was probably the same device. In 2002, Cecrop was offering the CFS2000, while KSI offered the K-1000. In 2004, KSI is still displaying the device on their web site, while there is no more information about an optical sweep sensor on the Cecrop website.