J. Biomedical Science and Engineering, 2009, 2, 261-272
doi: 10.4236/jbise.2009.24040 Published Online August 2009 (http://www.SciRP.org/journal/jbise/
JBiSE
).
Published Online August 2009 in SciRes. http://www.scirp.org/journal/jbise
Finger-vein image recognition combining modified
hausdorff distance with minutiae feature matching
Cheng-Bo Yu, Hua-Feng Qin, Lian Zhang, Yan-Zhe Cui
Chongqing Institute of Technology, Chongqing 400050, China
Email: yuchengbo@cqit.edu.cn
Received 6 January 2009; revised 22 February 2009; accepted 26 February 2009.
ABSTRACT
In this paper, we propose a novel method for
finger-vein recognition. We extract the features
of the vein patterns for recognition. Then, the
minutiae features included bifurcation points
and ending points are extracted from these vein
patterns. These feature points are used as a
geometric representation of the vein patterns
shape. Finally, the modified Hausdorff distance
algorithm is provided to evaluate the identifica-
tion ability among all possible relative positions
of the vein patterns shape. This algorithm has
been widely used for comparing point sets or
edge maps since it does not require point cor-
respondence. Experimental results show these
minutiae feature points can be used to perform
personal verification tasks as a geometric rep-
resentation of the vein patterns shape. Fur-
thermore, in this developed method. we can
achieve robust image matching under different
lighting conditions.
Keywords: Biometrics; Finger-Vein Verification;
Gabor Enhancement; Minutiae Matching; Modified
Hausdorff Distance
1. INTRODUCTION
Biometrics is the science of identifying a person using
their physiological or behavioral features. Recently, vein
pattern biometrics has attracted increasing interest from
many research communities. Finger-vein recognition is a
new biometrica identification technology using the fact
that different person has a different finger-vein pattern
[2,3,4,5]. Compared with fingerprint recognition, the
advantages of the finger-vein recognition are [1]: 1) Do
not need to consider the condition of the skin surface and
can prevent the artificial finger; 2) Increase the forgery
difficulty by using the invisible features inside the hu-
man body which only appears under the infrared light; 3)
Non-contact recognition has no bad effect on public
health. The properties of uniqueness, stability and strong
immunity to forgery of the vein pattern make it become
a potentially good biometric which offers secure and
reliable for person identification. A typical vein pattern
biometric system consists of five processing stages [5]:
image acquisition, image enhancement, vein pattern
segmentation, feature extraction and matching. During
the image acquisition stage, vein patterns are usually
obtained using infrared imaging technologies. One
method is using a far-infrared camera to acquire the vein
pattern images of finger-vein [1,2,6]. In order to get the
shape representation of the pattern, after obtaining the
images, vein pattern is separated and extracted from the
background. Finally, a robust image similarity measure-
ment is imperative for matching images under different
conditions. There are a number of previous methods
based on Hausdorff distance function for image match-
ing [7,8,9,10,11]. One of the most distinguished benefits
of Hausdorff distance is that it does not require point
correspondences between two objects or two images.
Dubuisson and Jain [12] developed several modified
Hausdorff distances (MHD) for comparing the edge
maps computed from the gray-scale images. Paumard
proposed a censored Hausdorff distance (CHD) for com-
paring binary images [13]. Takacs introduced the
neighborhood function and associated penalties to ex-
tend the MHD for face recognition [14,24,25]. Guo et al.
proposed a new modified Hausdorff distance which is
weighted by a function derived from the spatial informa-
tion of human face [15]. Furthermore, Lin et al. pro-
posed modified Hausdorff distances with spatial
weighting determined by eigenface features [16]. The
eigenface-based weighting function provides more
weighting on important facial features, such as eyes,
mouth, and face contour. Zhu et al. employed an im-
proved Gabor filter for computing edge maps and ap-
plied a weighted modified Hausdorff distance (WMHD)
in a circular Gabor feature space for comparing images
[17]. LingyuWanga applied the modified Hausdorff dis-
tance based matching scheme to the interesting points
for comparing images [6].
This research is motivated by P. L. Hawkes et al [6].
262 R. Wirestam et al. / J. Biomedical Science and Engineering 2 (2009) 261-272
SciRes Copyright © 2009 JBiSE
In this paper, we utilize the modified Hausdorff distance
(MHD) to analyze the spatial similarity between the mi-
nutiae feature sets. Experimental results indicate that
these minutiae feature points can be used to perform
personal verification tasks as a geometric representation
of the vein patterns shape. Furthermore we are able to
achieve robust image matching under different lighting
conditions.
2. PREPROCESSING OF INFRARED VEIN
PATTERN IMAGES
2.1. Finger-Vein Pattern Database
Our finger-vein image capture device mainly consists of
near-infrared light source, lens, cavum, light filter, im-
age ingesting equipment. Vein patterns cannot be ob-
served using normal, visible rays of light since they are
beneath the skin’s surface. However, vein patterns can
be viewed through an image sensor which is sensitive to
near-infrared light (wavelengths between 700 and 1000
nanometers), because near-infrared light passes through
human body tissues and are blocked by pigments such as
hemoglobin or melanin. As hemoglobin exists densely in
blood vessels, near-infrared light shining through causes
the veins to appear as dark shadow lines in the near-
infrared image. To obtain a stable finger-vein pattern ,our
light source adopts near-infrared light source with
wavelength of 890 m, the image ingesting part adopts
near-infrared CCD camera with wavelength of 900 m.
our finger-vein database comprises of 50 distinct sub-
jects, each subject having ten different images, taken at
different times and obtained from middle finger in the
right hand. The images are subject to variations such as
lighting. All the images are taken at a dark homogeneous
background and the finger is in upright, frontal position
(with a tolerance for some side movement). The images
are 256 grey levels per pixel and normalized to
376328
pixels. In our analysis, no pre-processing of
the images was conducted. Example image of five sub-
jects are shown in Figure 1(a).
2.2. The Lmage Normalization
The proportion of the vein area varies mostly at different
time. And for the convenience in further study, the di-
mension size normalization is done in this paper. The
vein image is defined as . That is to say the im-
age zooming will be done. For the difference of acquisi-
tion time, light intensity and the personal palm thickness,
the image gray scale distribution is different highly. If
the image difference is great, the difficulty of image
processing and matching will be increased. So the image
must be normalized. All of the images must be converted
to the standard image of the same mean and variance.
9664
(a) Inpuage t im
(b) Normalized image
Figure 1. The vein image.
R. Wirestam et al. / J. Biomedical Science and Engineering 2 (2009) 261-272 263
SciRes Copyright © 2009 JBiSE
For dispelling the illumination effect, a method of
gray scale normalization is adopted.
 
255
,'
,
12
1
GG
Gjip
jip (1)
where is the gray scale value of original image;
is the gray scale value after converted; is
the minimum gray scale of original image; is the
maximum gray scale of original image. Figure 1(b)
shows the vein pattern image after enhancement with
noise reduction and normalization.
jip ,'
jip ,1
G
2
G
2.3. Orientation Image
The orientation image represents an intrinsic property of
the finger-vein images and defines invariant coordinates
for ridges and valleys in a local neighborhood. A number
of methods have been proposed to estimate the orienta-
tion field of fingerprint images [1,10,11,17]. Similarly,
by viewing a finger-vein image as an oriented texture,
we have improved orientation estimation algorithm.
Given a normalized image , the main steps of the
algorithm are as follows:
f
1) Compute the gradients and
ji
x,
ji
y, at
each pixel . Depending on the computational re-
quirement, the gradient operator may vary from the sim-
ple Sobel operator to the more complex Marr-Hildreth
operator.
ji,
2) Estimate the local orientation of each pixel
ji,.
a) Use the window to slide in the original
image, pixel gray value in the center of the window is
.
WW

jif ,
b) Orientation of window is estimated and is
regarded as orientation of the pixel in the center
of the neighborhood (the size of the neighborhood is
decided by the actual conditions). The equations using to
estimate the local orientation is as follows:
WW
ji,
 




 2
2
2
2
,,2,
W
i
W
iu
W
j
W
jv
yxx vuvujiV (2)
  





2
2
2
2
22 ,,,
W
i
W
iu
W
j
W
jv
yxy vuvujiV (3)
 

 jiV
jiV
ji
y
x
,
,
arctan
2
1
, (4)
where is the least square estimate of the local
ridge orientation at the block centered at pixel
ji,
ji,.
Mathematically, it represents the direction which is or-
thogonal to the dominant direction of the Fourier spec-
trum of the WW
window.
c) If every point in the image is passed, namely orien-
tation of all pixels are estimated, that is end. Otherwise,
repeating above Step.
3) Due to the presence of noise, corrupted ridge and
valley structures, minutiae, etc. in the input image, the
estimated local ridge orientation,

ji ,
, may not al-
ways be correct. Since local ridge orientation varies
slowly in a local neighborhood where no singular points
appear, a low-pass filter can be used to modify the in-
correct local ridge orientation. In order to perform the
low-pass filtering, the orientation image needs to be
converted into a continuous vector field, which is de-
fined as follows:

jij ,2cos
i
x,
(5)
and

jij ,2cos
i
y,
(6)
where
j,i
x
and
ji
y, are the
x
and com-
ponents of the vector field respectively. In the resulting
vector field, the low-pass filtering can be performed as
follows:
y




2
2
',,,
W
j
W
jv
xx vjuivuhji

2
2
W
W
iu
(7)
and
 





2
2
2
2
',,,
W
W
iu
W
j
W
jv
yy vjuivuhji (8)
where is a two-dimensional low-pass filter with unit
integral and
h

WW
specifies the size of the filter.
4) Compute the local ridge orientation at using
ji,
 

ji
ji
jiO
y
x
,
,
arctan
2
1
,'
'
(9)
With this algorithm, a fairly smooth orientation field
estimate can be obtained. Figure 2 shows the first ex-
ample of the orientation image estimated with our algo-
rithm in Figure 1.
2.4. Gabor Filter
The configurations of parallel ridges and valleys with
well defined frequency and orientation in a Finger Vein
image provide useful information which helps in re-
moving undesired noise. The sinusoidal-shaped waves of
264 R. Wirestam et al. / J. Biomedical Science and Engineering 2 (2009) 261-272
SciRes Copyright © 2009 JBiSE
Figure 2. Orientation fields using and our method (20
W
and ).
10
W
ridges and valleys vary slowly in a local constant orien-
tation. Therefore, a band pass filter is used to tune the
corresponding frequency. Moreover, orientation can ef-
ficiently remove the undesired noise and preserve the
true ridge and valley structures. Gabor filters have both
frequency-selective and orientation-selective properties
and have optimal joint resolution in both spatial and
frequency domains. Therefore, it is appropriate to use
Gabor filters as band pass filters to remove the noise and
preserve true ridge/valley structures.
The circular Gabor filter is an effective tool for texture
analysis [20], and has the following general form:





sincos2exp
2
exp
2
1
,,,, 2
22
2
uyuxi
yx
x
uyxG

(10)
where 1i, u is the frequency of the sinusoidal
wave,
controls the orientation of the function, and
is the standard deviation of the Gaussian envelope.
To make it more robust against brightness, a discrete
Gabor filter,

,,,, uyxG, is turned to zero DC (direct
current) with the application of the following formula:


2
12
,,,,
,,,,,,,,
~
 

n
uyxG
uyxGuysG
n
ni
n
nj


(11)
Here is the size of the filter. In fact, the imagi-
nary part of the Gabor filter automatically has zero DC
because of odd symmetry. The adjusted Gabor filter is used
to filter the preprocessed images. In our system, we ap-
plied a tuning process to optimize the selection of these
three parameters
2
12n
O
, , 5179.1u1116.0
.
2.5. The Vein Extraction
The image segmentation is very important in the whole
process of finger vein recognition and it is very difficult.
There are several image segmentation methods. The
classic methods are threshold method [26], region grow-
ing method [27], relaxation method [28], edge detection
method [29], split-merge algorithm [31] and so on. The
modern methods are NN method [30], fuzzy clustering
method [32] and so on. The different methods are
adapted in the different application fields. There is no
segmentation method fitting all images. So selecting the
suitable segmentation method is very important. There-
fore, we proposed a completely new method to segregate
the vein image, the principle of the algorithm is as fol-
lowing:
Step 1: Convolution (i=1, 2, , 8) of each
pixel within the

iFgray
99
window in image were calcu-
lated by corresponding eight direction Operator (As
shown in Figure 3). Then get the largest convolution
in eight directions.
maxG

iFgrayMaxG
i
max (12)
Then, maximum is gray value of the point
maxG
max, GnmGray
(13)
Step 2 Threshold segmentation
Step 2.1 The first threshold segmentation


,,
,0
Graym nifGraym n
Graym notherwise
0
(14)
Step 2.2 The second threshold segmentation

NumGraysumGmean
 

,
,,
GmeanifGraym nGmean
Graym nGraym notherwise
(15)
Gmean is the average of non-zero elements in the
image.
Graysum and expresse the sum and
number of non-zero elements respectively.
Num
Step 2.3 Fuzzy enhancement
After the previous twice segmentation, then range of
the gray value is
Gmean,0, pseudo-vein characteris-
tics and noise are likely to exist in the region, cleared the
fuzzy part by using fuzzy enhancement operator. This
will further reduce the noise and removed pseudo-vein.
The algorithm are as following:
1) Calculate the degree of membership, namely:


1
,
,

K
nmGray
nmGrayGumn (16)
2) Calculate the means of all the elements
within
mn
T
1212
pp window
R. Wirestam et al. / J. Biomedical Science and Engineering 2 (2009) 261-272 265
SciRes Copyright © 2009 JBiSE
0 0 0 0 0 0 0 00
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 00
0 0 0 0 0 0 0 0 0
3 0 -1 0 -4 0 -1 0 3
0 0 0 0 0 0 0 00
0 0 0 0 0 0 0 00
0 0 0 0 0 0 0 00
0 0 0 0 0 0 0 00














0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
3 0 0 0 0 0 0 0 0
0 0 -1 0 0 0 0 0 0
0 0 0 0 -4 0 0 0 0
0 0 0 0 0 0 -1 0 0
0 0 0 0 0 0 0 0 3
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0














3 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 -1 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 -4 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0-1 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 3
(a) 0º (Horizontal) orientation (b) 157.5º orientation (c) 135º orientation
0 0 3 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 -1 0 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 -4 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0-1 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 3 0 0














0 0 0 0 3 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 -1 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 -4 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 -10 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 3 0 0 0 0














0 0 0 0 0 0 3 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0 -1 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 -4 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0-1 00 0 0 0
0 0 0 0 0 0 0 0 0
0 0 3 00 0 0 0 0
(d) 112.5º orientation (e) 90º orientation (f) 67.5º orientation
0 0 0 0 0 0 0 0 3
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 -1 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 -4 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0-10 00 0 0 0
0 0 0 0 0 0 0 0 0
3 0 0 0 0 0 0 0 0














0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 3
0 0 0 0 0 0 -1 0 0
0 0 0 0 -4 0 0 0 0
0 0-1 0 0 0 0 0 0
3 000 00 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0














(g) 45º orientation (h) 22.5º orientation
Figure 3. The direction of the operator.
3) Calculate pixel gray and gray degree
of membership adjusted within
', nmGray
'
mn
u

1212
pp
window, its mathematical expression is

2
'
2
1
11 1


 

 


r
r
mn
mnmn mn
mn
mn
mn
mnmn mn
mn
u
uifu
T
u
u
uifu
T
 
'
1', mn
uKnmGray
Step 2.4 The third threshold segmentation
T
T
(17)
Use
1212
pp window sliding in the original
image, pixel gray value in the window center is
', nmGray , then all the pixels within the window com-
pose of a set as the following:
pplklnkmfjiS ,,1,0,1,,,,,  
266 R. Wirestam et al. / J. Biomedical Science and Engineering 2 (2009) 261-272
SciRes Copyright © 2009
JBiSE
Obtained the average of all pixels
in the window.

nmSAverage ,
Formula as follows





p
pm
p
pn
nmGray
pp
nmSAverage ',
1212
1
,
(18)
 



p
pm
p
pn
nmSAveragenmGray
pp
nm 2
,',
1212
1
,
(19)
  
nmnmSAveragenmT ,,,
 (20)
So each pixel of images has a threshold value. The
binary images obtained by the each respective threshold
values are


1,'
,' 0

ifGraymnTmn
Graym notherwise
,
(21)
Obtaining the final image only contain-
ing the vein characteristics.
', nmGray
It is obvious that the grain of the original image has
been got as Figure 4. The effect is comparatively ideal.
Median filtering method can eliminate burrs and make
the borderline smooth. In addition, because the result of
the new threshold dispose algorithm inducts massive
noises, these noises are wiped off according to the size
of them in this paper. The effect of filtering is as shown
in Figure 5.
2.6. Lmage Thinning
In this paper, we thin the vein image using the combina-
tion method of general conditional thinning and tem-
plates. Get rid of the special un-single pixel point after
the general conditional thinning.
a) The conditional thinning algorithm [22]
Region points are assumed to have value 1 and back-
ground points to have value 0. The method consists of
successive passes of two basic steps applied to the con-
tour points of the given region, where a contour point is
any pixel with value 1 and having at least one 8-
neighbor valued 0. With reference to 8-neighborhood
Figure 4. Segmentation. Figure 5. Filtering.
notation shown in Figure 6, Step 1 flags a contour point
for deletion if the following conditions are satisfied:
1
p


1
1
246
468
() 26
() 1
() 0
() 0
aNp
bTp
c ppp
dppp



(22)
where
1
pN is the number of nonzero neighbors of
, that is,
1
p
98321 pppppN 
(23)
And
1
pT is the number of 0-1 transitions in the
ordered sequence . For example,
23 892
,,,,,pp ppp
14
pN ,
13
pT in Figure 7.
In step 2, conditions (a) and (b) remain the same, but
conditions (c) and (d) are changed to
246
468
(') 0
(') 0


cppp
dppp
(24)
Thus one iteration of the thinning algorithm consists
of: 1) applying step 1 to flag the remaining border points
for deletion; 2) deleting the flagged points; 3) applying
step 2 to flag the remaining border points for deletion; (4)
deleting the flagged points. This basic pro cedure is app-
9
p 2
p 3
p
8
p 1
p 4
p
7
p 6
p 5
p
Figure 6. Neighborhood Arrangement Used by the Thinning
lgorithm. A
Figure 7. Illustration of condition (a) and (b) in Eq.(22) (In
this case,
4
1
pN ,
3
1
pT ).
0 0 1
1 1
p
0
1 0 1
R. Wirestam et al. / J. Biomedical Science and Engineering 2 (2009) 261-272 267
SciRes Copyright © 2009 JBiSE
lied iteratively until no further points are deleted, at
which time the algorithm terminates, yielding the skele-
ton of the region.
b) The improved thinning algorithm
The improved thinning algorithm is on the base of the
conditional thinning. On the conditional thinning image,
the template algorithm is added to get rid of the un-sin-
gle pixel point in this paper.
For the case of Figure 8, the un-single pixel point is
pointed by the red line. We must think of one method
to get rid of the pixels point, because they are the su-
perabundance points in the image. There are two
methods to get rid of it. One is that the image can still
be assured the connectivity after getting out of these
points. These points can be deleted according to the
connection of 4- neighborhood and 8-neighborhood.
The other uses the method of templates. The templates
are as follow Figure 9. The center of template is the
reference point.
The center of template is the reference point *. “1” is
the point of target image, “0”is the point of background
image, the points of Figure 6 which satisfy conditions
will be dispelled by the templates Me, Mf, Mg, Mh. Do
iteration based on the conditional thinning image until
the un-single pixel points of the first class are dispelled
completely.
c) Burr cutting
The noise and shadow of original finger vein image
will produce “Burr” in the skeleton image, and it will
affect the following processing. "Burr" can be dispelled
by recording the amount of the un-single pixel points
from each endpoint to the bifurcation points, and then
select a threshold. The value of the un-single pixel points
whose amount is less than threshold amounts 0, contrar-
ily, the value keeps constant. Image thinning is shown in
Figure 10.
3. EXTRACTION OF MINUTIAE POINTS
The branching points and the ending points in the vein
pattern skeleton image are the two types of critical
points to be extracted. To obtain the junction points from
the skeleton of vein patterns, we run the following
pixel-wise operation commonly known as the cross
number concept [21]: For a region (as follow
Figure 11), If is 1, and the number of transition
33
0
p
Figure 8. The un-single pixel points of the first kind.
Figure 9. The un-single pixel point templates of the first kind.
(a) General conditional thinning (b) Improved thinning algorithm (c) Burr cutting
Figure 10. Image Thinning.
268 R. Wirestam et al. / J. Biomedical Science and Engineering 2 (2009) 261-272
SciRes Copyright © 2009 JBiSE
Figure 11. 33
region
trans
N
8
p
between 0 and 1 (and vice versa) from to
is greater than or equal to 6, then is a junction
1
p
0
p
point. Mathematically, this can be expressed with the
following equation:
 8
1
1
i
iitrans ppN , where
19 pp
A similar approach can be applied to find the ending
points. The difference is that the number of transition
for an ending point is now exactly 2. The flow-
chart of the fingerprint enhancement algorithm is shown
in Figure 12 and experimental process is shown in Fig-
ure 13.
trans
N
Figure 12. A Flowchart of the proposed finger-vein processing algorithm.
(a) (b) (c) (d) (e) (f) (g) (h) (i)
(a) Input image (b) Orientation image estimation (c) Gabor filtering (d) Image segmentation (e) Filtering (f) General conditional thinning (g) Im-
proved thinning algorithm (h) Burr cutting (i) Minutiae points extraction
F
igure 13. Outputs of different stages of the algorithm.
1
p 2
p 3
p
8
p 0
p 4
p
7
p 6
p 5
p
Minutiae of the vein patte
r
n
(The bigger square for bifurcation points; the
smaller square for ending points)
Orientation image
estimation
Gabor filtering
Image segmentation
Image thinning
Minutiae points ex-
traction
Normalization
In
p
ut ima
g
e
R. Wirestam et al. / J. Biomedical Science and Engineering 2 (2009) 261-272 269
SciRes Copyright © 2009 JBiSE
4. EXPERIMENT RESULT
Experiment on our finger-vein dataset: In this section,
three experiments conducted to demonstrate the per-
formance of the proposed method for object recognition.
Our finger-vein database comprises of 50 distinct sub-
jects, each subject having 10 different images, taken at
different times. The images are subject to variations such
as lighting. All the images are taken against a dark ho-
mogeneous background and the Finger are in upright,
frontal position (with a tolerance for some side move-
ment). The images are 256 grey levels per pixel and
normalized to pixels. These images are
pre-processed by our method before matching experi-
ment.
376328
4.1. Verification Using MHD
Many techniques can be applied to the analysis of minu-
tiae of vein pattern in a similar manner to those applied
to fingerprint minutiae. However, due to the fact that the
number of minutiae for the vein pattern is relatively
small compared to those for fingerprints, analysis based
on geometrical information is preferred to statistical
features. Since the vein pattern is represented as a set of
two-dimensional points, matching of a pair of such pat-
tern can be achieved by measuring the Hausdorff dis-
tance between the two minutiae sets.
The original Hausdorff distance was proposed for
comparing two binary images by Huttenlocher et al.[23].
The computation of Hausdorff distance does not require
point correspondences between the two point sets. They
proposed efficient computational algorithms for speed-
ing up the process of finding similar patterns in an image
by searching the regions with the smallest Hausdorff
distances in the image [6]. For two point sets
x
N
xxxxX ,,,, 321
and
y
N
yyyyY,,,, 321 , Eqs.
(25) and (26) give the definition for a Hausdorff distance,
where
H
D h and are the undirected and directed
Hausdorff distance for the two point sets, respectively.
The smaller the value of
H
D, the more similar the two
point sets are
 
XYdYXdYXHD ,,,max,
(25)
ji
Yy
Xx yxYXd
j
i

minmax, (26)
However, the original Hausdorff distance method is
sensitive to small perturbations in point locations for
shape alignment. To overcome the weakness of the
Hausdorff distance, the modified Hausdorff distance
(MHD) [12] for matching two objects is developed and
has the following desirable properties: 1) its value in-
creases monotonically as the amount of difference be-
tween the two sets of points increases, and 2) it is robust
to outlier points that might result from segmentation
errors. Unlike the original form, the undirected MHD is
defined as in Eq. (27)


Xx
ii
Yx
Xii
yx
N
YXdmin
1
, (27)
Figure 13 shows the false acceptance rate (FAR)
and false rejection rate (FRR) curves, from which it
can be seen that when the threshold value for the dis-
tance measure HD is 0.52, the equal error rate (EER)
is approximately 14.51%. An experiment with the
MHD was carried out on the same data set, and the
algorithm achieves 0.761% EER (as shown in Figure
14).
Genuine
%percentage
Imposter
FAR%
EER
HD distance FRR%
(a) (b)
(a) Genuine and imposter distributions and (b) Error rate for minutiae recognition using the original form of Hausdorff distance (EER =
14.51% where the threshold is observed to be 0.52)
Figure 13. Verification test results.
270 R. Wirestam et al. / J. Biomedical Science and Engineering 2 (2009) 261-272
SciRes Copyright © 2009 JBiSE
Genuine
%percentage
FAR%
Imposter
EER
M
HD distance FRR%
(a) (b)
(a) Genuine and imposter distributions and (b)Error rate for minutiae recognition using MHD (EER = 0.761% where the threshold is observed to
be 0.43)
Figure 14. Verification test results.
4.2. Verification Using Shape of the Vein
Patterns
To verify that minutiae points can best represent the shape
of the vein patterns for vein recognition, in the following,
we show some experimental results of applying the pro-
posed robust image matching algorithm to the skeleton
representation of the vein pattern. The experiments utilize
the same MHD to measure the similarity. Figure 15 shows
FAR and FRR curves, from which it can be seen that when
the threshold value for the distance measure HD is 0.41,
the equal error rate (EER) is approximately 7%. Table 1
contains the results for the evaluation, which shows that
while the shape of the vein patterns can reach relatively
high recognition accuracy, the minutiae can further in-
crease the accuracy and require less time.
4.3. Two Types of Minutiae
To evaluate the usefulness of the two types of minutiae,
namely bifurcation and ending points, we carried out
three sets of personal verification experiments: firstly
with the bifurcation points only, and then with ending
points only, and finally the combination of the two
minutiae types. The three sets of experiments utilize
the same MHD to measure the similarity. Table 2 con-
tains the results for the evaluation, which shows that
while the bifurcation and ending points can reach rela-
tively high recognition accuracy, the combination of
the two minutiae can further increase the accuracy,
which is advantage especially when high feature dis-
criminating power is desired for a large population
group.
FAR%
%percentage
Imposter
Genuine
EER
MHD distance FRR%
(a) (b)
Figure 15. Error rate curves for minutiae recognition using MHD (EER = 7% where the threshold is observed to be 0.41).
R. Wirestam et al. / J. Biomedical Science and Engineering 2 (2009) 261-272 271
SciRes Copyright © 2009 JBiSE
Table 1. Minutiae and shape of the vein patterns evaluation
using MHD.
Equal error
rate (%)
Threshold
value Time(s)
Shape of the
vein patterns 7 0.41 6.5
Combination of
both minutiae 0.761 0.43 2.2
Table 2. Minutiae evaluation using MHD.
Equal error
rate (%)
Threshold
value
Bifurcation points only 9.20 0.48
Ending points only 8.89 0.46
Combination of both
minutiae 0.761 0.43
5. CONCLUSIONS
This paper proposes a novel method applicable to fin-
ger-vein recognition. Firstly, we extract the features of
the vein patterns for recognition. Secondly, the minu-
tiae features are extracted from the vein patterns for
recognition, which include bifurcation points and end-
ing points. These feature points are used as a geomet-
ric representation of the shape of vein patterns. Finally,
the modified Hausdorff distance algorithm is proposed
to evaluate the discriminating between all possible
relative positions of the shape of vein patterns. Ex-
perimental results show the equal error rate (EER)
reaches 0.761% where the threshold value for the dis-
tance measure HD is observed to be 0.43. This result
indicates the minutiae features in the vein patterns can
be used as a feature sets in the personal verification
applications efficiently.
Though the current database is relatively small and it
is not adequate to draw any firm conclusion on the dis-
criminating power of vein patterns for a large population
(in terms of millions of users) group, the experiments do
show the potential of the minutiae of the vein patterns as
a biometric feature for personal verification applications
in a reasonable sized user group. The results presented
here indicate, as a new identity authentication technol-
ogy, the vein recognition has a better long term potential,
need to be studied further, and can be applied to the lives
of people better.
6. ACKNOWLEDGMENTS
This article belongs to science and technology re-
search item of Chongqing education committee
(KJ070620). The authors are also most grateful for
the constructive advice and comments from the
anonymous reviewers.
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