Fingerprint Identification Based on Fiber Optic Taper
Fingerprint Recognition Based on Fiber Optic Taper
Abstract
To extract the Fingerprint pattern more exactly,a new optoelectronic fingerprint collected method and system based on the optical fiber optic taper which coupled with CCD is researched and designed on the basis of the analysis of the fingerprint gathering technology.According to the light-admitting quality of a finger and the light transmission of fiber optic taper.A light-supply apparatus and the analysis of luminous intensity are designed,the principle of hardware devices are analysed and the experimental result is given,meanwhile the images of non-contact and contact type of optoelectronic fingerprint collect method are compared respectively.It has the advantages of small volume,high gathering speed,high-resolution and higher credibility.
Keywords: Fingerprint Collection; Optoelectronic; Fiber Optic Taper; CCD
Preface
Fingerprint patterns are unique,stable,and remain unchanged.Due to these features.Fingerprint recognition are widely used on Crime investigation,immigration control,access control etc.However,the image of fingerprint pattern could be processed and identified only after recorded into computer.So the digital collection technique of fingerprint is very important in the whole fingerprint recognition system.As the area of Fingerprint is relatively small,also fingerprint will gets some injury in daily life.In this case,to get a high quality image of Fingerprint details is a very complicate job.So,the requirement for Fingerprint Collection equipment is ever-growing.Currently,we can categorize the Fingerprint Recognition by following type : (1) Optical (2) electric capacity (3) Thermal (4) pressure sensing (5) Ultrasound.
In this article,the equipment we’re introducing is based on optical collecting method.There mainly 3 kinds of structure of Optical fingerprint sensor.
i.Lens & Prism Compounded system
ii.Waveguide & lens system
iii.Fiber Optic Taper system
In the lens system,there several disadvantages. 1)Relatively Big Size 2)Can’t identify the wet finger 3)Ghost image. Based on those disadvantages,people has developed the new FOT-CCD coupling type fingerprint sensor.
Structure of Fingerprint collection with Fiber Optic Taper
Following with a simplify structure of the collection system.
Following the whole working flow for collecting fingerprints. 1) Turn on the light 2) Turn on the image detection software and setup related parameter 3) Put finger on the big end of the Fiber Optic Taper.4)Meanwhile turn on the laser power,and we use the lighting control to get a suitable lighting power, then save the image. 4) Laser shot on the spherical mirror,get pass through the finger and imaging on the big end of fiber optic taper. 5) FOT has imaging transmission function,so that Fingerprint can be imaged on the CCD surface,then we use image acquisition card to collect the image into computing system for further fingerprint comparison.
Selection of Light Source
The first issue to make optical imaging is the selection of light source.As finger is not penetrated by light,normal light source will not get through finger and imaging on CCD,so we use laser as the light source in the experiment.Laser has features of High Energy,Monochromaticity,Coherent,Directional. Compared with normal light,biology organ has low absorb to it,low scattering,and high transmission ratio.All its wave are propagate in one direction,it has a very good sequence rule,and all com from one wavelength.So it’s very easy to control.
In this experiment,we use Watec camera’s CCD spectral response feature.(Show below)
At 600nm wavelength the sensitive will hit the high point,and also have a good sensitive around 0.62-0.76um. We will use light source with wavelength 650nm, Power 3~4mw red laser as the illumination source.
Analyse of Fingerprint density distribution
We usually collect fingerprint with the thumb,following (a) is the XRAY graphic of side cut of thumb.And (b) is the Grey level of XRAY along the thumb.
Fingerprint Density
According to light density principle,the light intensity of transmission light is decided by the grey level of finger.The higher grey level,the light transmission is lower.When incident light intensity is higher than the area of low grey level,we can then make transmission light pass through fiber optic taper and has a well-distributed on CCD.
Analyse of Light intensity
Light source and Finger is on the same surface of the equipment,in order to make light reflect on the upper surface of Finger,we will use a reflective mirror.And laser will get pass the lense and maintain the GAUSS distribution,so we use concave mirror here as the reflective mirror.Following the beam path.
Gauss Beampath
When incident light is parallel to the centering axis,its reflect light will finally focus at f.
According to experiment,a laser source around 3-4mw will be enough to transmit the finger and make CCD saturated.So we can use lighting control to control light intensity to fulfil the requirement. The light distribution and GAUSS beam distribution is decided by following equation.
Equation 1Equation 2
According to the analyse above,the light intensity on the center of finger will higher than the tip and side.
According the graph of light intensity and XRAY grey level distribution (Showed below)
Light Distribution
Experiment of Fingerprint Collecting
Optical fingerprint collecting system performs well in long-term use.It can endure a certain level of thermal changes and its also very stable.More important,the prime cost is lower than other methods,and can provide high resolution image.
Here we have 3 results that collected by different methods.
Fingerprint Sampling
Conclusion
The Fingerprint recognition based on fiber optic taper or plate is accessible.
Laser light source solve the problem that image couldn’t be imaged on CCD
Based on the Fiber and CCD pixel could be imaging at micron level,we can fulfil fingerprint collection with high resolution. And collection of larger area.
The contact surface between fiber and finger is smooth,which can remove ghost image easily.
In conclusion,this kind of method can collect fingerprint in larger area with a high resolution,and it has a relatively simple structure.Also the prime cost is lower than other methods.
HONSUN can provide fiber optic plate, fiber optic taper according to custmer’s requirement.
How to get a quote
Send an e-mail with your contact data and additional specific details (We need to know) to
info@honsun.cc or call +86-13925100917.