CN101561870B - Dorsal hand vein collection system and method thereof - Google Patents

Abstract

The invention relates to a novel biological characteristic identification method acquisition system and a method thereof. The system acquires texture images of blood vessels on the back of the hand using low-cost equipment. The system reasonably designs light paths, and three imaging modes are realized by adopting a method of combining two sets of transmission and reflection near-infrared light sources: a transmission mode, a reflection mode and a mixing mode, thereby obtaining a comprehensively considered hand back vein image. The triple filtering noise reduction processing is used for smoothing the hand back vein image, and the finally output hand back vein image can achieve the segmentation effect. The acquisition system adopts reasonable light source design and an effective noise reduction processing method, so that a low-price non-professional camera can be used, and the system cost is greatly reduced.

Description

Hand back vein acquisition system and method thereof

Technical field

The invention belongs to the data acquisition technology field of new bio feature identification technique, be specifically related to a kind of hand back vein acquisition system and method thereof.

Background technology

Living things feature recognition based on hand back vein is a kind of new method of living things feature recognition.Hand back vein is identified in aspects such as uniqueness, permanent, validity, robustness and has outstanding performance, can use in that bank and sports buildings etc. are local.Hand back vein identification carrying out sportsman and test personnel's registration management is just used in 2008 Beijing Olympic Games softball shop.This method is with traditional living things feature recognition, compare as people's face, fingerprint, identification based on the hand back vein texture structure has its special benefits: its imaging belongs to Active Imaging, can not be subjected to as the people's face under the natural lighting photodistributedly influences very greatly, not influenced by humidity, heavy physical labour; In addition, its feature is highly stable, unless suffer from vascular diseases such as rheumatoid disease, otherwise can not change all the life.

When the contrast of hand back vein image is a gray-scale value between hand back vein and the skin of dorsum of hand when differing maximum, can be easy to realize cutting apart of hand back vein texture, so the enough strong hand back vein image of contrast is a base of recognition; But under visible light, hand back vein is to be difficult for observing.Medically adopt the transmission imaging pattern to hand back vein X-ray and ultrasonic imaging, this image quality is very high, but the property invaded is very strong, does not possess versatility, can't be applied in the living things feature recognition.The catoptric imaging pattern is often adopted in the imaging of commercial hand back vein, near infrared light the back of the hand with 700nm～1100nm wavelength, blood is different to this waveband infrared ABSORPTION AND SCATTERING with the surrounding skin tissue, on special-purpose ccd video camera, just can present blood vessel darker image relatively, and gatherer process is friendly quick; But the picture contrast that obtains is low slightly.

At present, also there are some problems in reflective hand back vein collection, mainly comprises:

First: because the use of professional ccd video camera, the price of hand back vein acquisition system is not cheap.Probably need 1000 dollars～2000 dollars.And the acquisition system price of palmmprint and fingerprint roughly is respectively 1000 dollars and 50 dollars.

Second: for the catoptric imaging pattern that extensively adopts at present, the contrast of hand back vein imaging is not high, particularly can't obtain the image of high-contrast to the postcapillary blood vessel.

However, since 2004, hand back vein was identified in Japan and Korea S still comes into vogue; The country in the Middle East and Southeast Asia also begins to consider to adopt this technology.This is because in the living things feature recognition field, and it is necessary that different situations are used different biometrics identification technologies.If can effectively reduce the cost of hand back vein acquisition system, adopt new imaging pattern to obtain the image of high-contrast, hand back vein identification is because its convenience, ease for use, high safety and high precision have the potentiality that obtain widespread use.

Summary of the invention

The objective of the invention is to design a kind of low cost, simple and practical, the hand back vein acquisition system and the method thereof that are beneficial to popularization.In order to reach low-cost purpose of gathering the hand back vein image, the present invention proposes acquisition scheme based on transmission-type and reflective combination, this scheme has strengthened contrast by using transmitted light source, uses reflection source to improve picture quality.

System of the present invention is made up of reflection source, common CCD camera, near infrared filter, scattering paper, handle and transmitted light source.Two cover combination of light sources are used, total transmission mode, reflective-mode or three kinds of imaging patterns of mixed mode.Two cover near-infrared light sources shine the back of the hand zone simultaneously, and wherein transmitted light source is placed on palm one side, and light transmission the back of the hand that it sends enters video camera, and purpose is to improve the contrast of image; Reflection source is placed on the video camera both sides, the rayed that they send on the back of the hand, the reflected back camera, purpose is to reduce noise, improves picture quality.Owing to use common CCD camera,, need to obtain and export final image through noise reduction process so the noise of gathering in the hand back vein image is bigger.

Hand back vein acquisition system of the present invention and method thereof contain following steps:

Step 1: the selection of imaging pattern in the hand back vein acquisition system;

Transmission, reflection are provided in hand back vein acquisition system of the present invention or have mixed three kinds of imaging patterns.

Step 2: the selection result according to step 1 enters transmission mode, reflective-mode or mixed mode;

Transmission mode only uses the transmitted light source of palm one side, and reflective-mode only uses the reflection source of the back of the hand top, and mixed mode uses transmitted light source and the reflection source above palm one side and the back of the hand simultaneously.

Step 3: the image acquisition of carrying out hand back vein according to the imaging pattern selection result of step 2;

According to the imaging pattern that step 2 is selected, utilize the collection of the video camera realization hand back vein image of common CCD.

Step 4: the noise reduction process of images acquired;

Because what use in the step 3 is the video camera of common CCD, the noise in the images acquired is bigger, need carry out noise reduction process.

Step 5: output final image.

Through after the noise reduction process of step 4, the hand back vein image that output meets the demands.

The invention has the advantages that:

(1), use cheap common CCD camera just can obtain the image of high-contrast, so system cost is low, is beneficial to industrialization owing to introduce transmitted light source;

(2) combination of transmitted light source and reflection source has not only improved picture contrast but also reduced picture noise, and the image that obtains is beneficial to and extracts vascular lake.

Description of drawings

Fig. 1 is the formation synoptic diagram of system of the present invention;

Fig. 2 is the process flow diagram of the method for the invention;

Fig. 3 is the distribution of light in biological tissue;

The image that Fig. 4 obtains for three kinds of imaging patterns of the present invention;

The histogram of the image that Fig. 5 obtains for three kinds of imaging patterns of the present invention;

Fig. 6 is the noise reduction process result of images acquired of the present invention;

Fig. 7 is the typical image in images acquired of the present invention storehouse.

Among the figure: 1. reflection source 2. video cameras

3. near infrared filter 4. scattering paper 5. the back of the hand

6. handle 7. transmitted light sources

Embodiment

Below in conjunction with accompanying drawing the specific embodiment of the present invention is described in further details.

Figure 1 shows that the formation synoptic diagram of system of the present invention.System of the present invention is made up of reflection source 1, common CCD camera 2, near infrared filter 3, scattering paper 4, handle 6 and transmitted light source 7.Two cover combination of light sources are used, total transmission mode, reflective-mode or three kinds of imaging patterns of mixed mode.Two cover near-infrared light sources shine the back of the hand 5 zones simultaneously, and wherein transmitted light source 7 is placed on palm one side, and light transmission the back of the hand 5 that transmitted light source 7 sends enters common CCD camera 2, and purpose is to improve the contrast of image; Reflection source 1 is placed on common CCD camera 2 both sides, and the rayed that reflection source 1 sends is on the back of the hand 5, and reflected back common CCD camera 2, purpose are to reduce noise, improve picture quality.Owing to use common CCD camera 2, the noise of gathering in the hand back vein image is bigger, needs to obtain and export final image through noise reduction process.

As shown in Figure 2, the method for the invention comprises following steps:

Step 1: the selection of imaging pattern in the hand back vein acquisition system;

Fig. 3 is the distribution of light in biological tissue, as shown in Figure 3, when near infrared light is organized, because the heterogeneity of tissue, will reflect, absorption and the multiple behavior of scattering.In biological tissue, blood has absorbed more near infrared light than surrounding tissue.Blood is a strong absorber in this zone, but its absorption peak just reaches cut off at 600nm, and will be more than big many of absorption in this regional scattering.Scattering is owing to different piece refractive index difference in the biological tissue causes, and it changes the direction that photon is advanced, and feasible should the generation along the photon that original direction is advanced departed from, thereby makes the light intensity decreasing on the former direction.

The ultimate principle of the inventive method is to have increased transmitted light source again on the basis of adopting reflection source, as the transmitted light source among Fig. 1.Table 1 has been listed biological tissue at wavelength 1, and absorption coefficient under the 064nm and 10,600nm and scattering coefficient, unit are cm ^-1

Absorption coefficient in table 1 biological tissue and scattering coefficient

	1, the absorption coefficient of 064nm	1, the scattering coefficient of 064nm	10, the absorption coefficient of 060nm	10, the scattering coefficient of 600nm
					Blood	9.77	508.6	860	860
Muscle	2	215	860	860

As can be seen from Table 1,1, under the irradiation of 064nm near infrared light, scattering coefficient is 50 times of absorption coefficient, so scattering process is the main cause of near infrared light imaging.Scattering process in the biological tissue has characteristics: most scatterings are forward scatterings, and light is the direction of propagation along trimmed book still, and seldom clubhauls.Though so repeatedly scattering has taken place, photon still can penetrate certain thickness tissue.According to the scattering major part of near infrared light in tissue is this character of forward scattering, and the present invention has increased transmitted light source, promptly light source and video camera is placed on the both sides of hand, and the light penetrate tissue enters video camera like this.This mode is enhancing contrast ratio greatly.

Step 2: the selection result according to step 1 enters transmission mode, reflective-mode or blend modes of operation;

Traditional near infrared hand back vein collecting device both sides polishing above the back of the hand, rayed back in one's hands has part light transdermal and enters tissue, and in tissue, reflect, absorb, reflect, there is small part light to pass from the skin surface back scattering again at last and gets back to camera.The shortcoming of tradition collecting device is that light is in the majority in the reflection of skin surface, and the light that enters skin is less; And the light that enters skin passes the light that enters camera from the back of the hand again through reflected refraction repeatedly in human body just fewer, is difficult to present hand back vein image clearly.The principle of tradition collecting device is to utilize the back scattering of near infrared light in tissue, in order to obtain the image of high-contrast, needs to use the dedicated video camera industry, thereby has increased the cost of hand back vein collecting device greatly.

The present invention has taked the two-way light source according to the forward scattering characteristics of light, reflection source and transmitted light source, as shown in Figure 1.The design reference of reflection source the design of traditional collecting device light source; And make the light that enters tissue more reach video camera according to the transmitted light source of forward scattering characteristics design, to carry more venous information.The two-way combination of light sources is used, and three kinds of imaging patterns are arranged: transmission mode, only adopt transmitted light source; Reflective-mode only adopts reflection source; Mixed mode, two kinds of light sources use simultaneously.

Step 3: the image acquisition of carrying out hand back vein according to the mode of operation selection result of step 2;

As shown in Figure 1, hand back vein acquisition system of the present invention is made up of reflection source 1, common CCD camera 2, near infrared filter 3, scattering paper 4, handle 6 and transmitted light source 7.The present invention adopts the B can respond near infrared light, and the common CCD camera 2 that this system adopts is video camera Logitech Pro4000 of a cheap USB interface., the image that obtains can directly be transferred on the desk-top computer; Near infrared filter 3 is selected near infrared all-pass optical filter for use, and it can effectively eliminate the influence of visible light; Transmitted light source 7 and reflection source 1 are selected all band near infrared diode for use, and the wavelength that this diode sends arrives 1100nm about 600nm greatly; Transmitted light source 7 is installed on the handle 6, holds on handle 6, and then transmitted light source can penetrate the back of the hand 5, places scattering paper 4 before reflection source 1, and effect is the hot spot of avoiding light emitting diode direct irradiation the back of the hand 5 to produce, the brightness of scalable reflection source simultaneously.

The image that Fig. 4 obtains for three kinds of imaging patterns of the present invention, the histogram of the image that Fig. 5 obtains for three kinds of imaging patterns of the present invention.By Fig. 4 and Fig. 5 as seen, because transmission mode selects the zone of histogram covering of hand back vein image down the wideest, so its contrast maximum; The contrast of hand back vein image good slightly than reflective-mode under the mixed mode, but they are all far short of what is expected than transmission mode.

Step 4: the noise reduction process of images acquired;

The ccd video camera that the present invention adopts is cheap non-professional camera Logitech Pro4000, so noise is bigger, tackles their noise level and estimates.For the image of actual acquisition, signal to noise ratio (S/N ratio) is very difficult calculating, and (i j), estimates the noise level of various imaging patterns with the total variation value J (u) of following formula calculating in piece image u.

$J\left(u\right)=\underset{i}{\mathrm{\Σ}}\underset{j}{\mathrm{\Σ}}{\left(\begin{array}{c}{(u(i,j)-u(i-1,j))}^2+{(u(i,j)-u(i+1,j))}^2\\ +{(u(i,j)-u(i,j-1))}^2+{(u(i,j)-u(i,j+1))}^2\end{array}\right)}^{\frac{1}{2}}$

Wherein, i, j are that (J (u) is the total variation value to image u for i, pixel coordinate j).

The image that the total variation value is big can contain more noise.Provided the total variation value of three width of cloth images among Fig. 5 result in the table 2, the visible light transmission pattern is than big many of other modal noises from table 2.This is because adopting the overriding noise of common CCD camera is dark current, and this is a kind of noise that is produced by semi-conductive thermal motion, and the brightness of it and light is inversely proportional to.The transmission mode light intensity is the most weak, so noise is than the high order of magnitude of other two kinds of patterns.When adopting reflective-mode and mixed mode, because the existence of reflection source, brightness of image is higher, and noise level is lower.

The total variation value of three kinds of imaging patterns of table 2

	Transmission mode	Reflective-mode	Mixed mode
				The total variation value	3.0580e+004	4.1234e+003	4.2771e+003

To sum up, table 3 has been listed the comparative result of above-mentioned three kinds of imaging patterns:

The comparison of three kinds of imaging patterns of table 3

	Transmission mode	Reflective-mode	Mixed mode
				Contrast	High	Low	Generally
Noise level	High	Low	Low

By table 3 as seen, transmission mode has the highest contrast, but noise level is the highest; And the image polishing that reflective-mode obtains is even, and picture noise is little, but contrast is very low, is unfavorable for cutting apart; Mixed mode has reflective noise little, the certain lifting of having got back of the uniform characteristics of polishing, contrast, but promote and not obvious.

According to the result of table 3,, need carry out noise reduction process to the hand back vein image in order to obtain high contrast.According to the vertical characteristics that distribute of hand back vein texture, and everyone vein width difference and little, be approximately 10～20 pixels.The present invention has adopted the method for three filtering:

The overall width of the matched filter of filtering for the first time is 300 pixels, and wherein pixel is a high level from the 150th to the 165th, and other are low level; If n is the pixel sequence number, n is a positive integer, and n ∈ [1,300], then can obtain a time series h[n].The hand back vein image of gathering, see Fig. 6 (a),, each row vector carried out one dimension process of convolution h[n with first matched filter respectively by the capable vector x [n] that vertically is divided into one by one] * x[n], each row vector obtains the new image of a width of cloth through after the process of convolution, sees Fig. 6 (b); Resulting new image is input to second wave filter again and carries out further noise reduction process.

Filter filtering is a S filter for the second time, and S filter is the optimal linear filtering device according to the minimum mean square error criterion design.For this 2D signal of image, it be calculated as follows:

$b(i,j)=\mathrm{\&mu;}+\frac{{\mathrm{\&sigma;}}^2-{\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="DEST\_PATH\_H200910081792901E00011.png"\; state="\{\{state\}\}">v</figure-callout>}}^2}{{\mathrm{\&sigma;}}^2}(a(i,j)-\mathrm{\&mu;})$

Wherein, i, j are the pixel coordinate of image, and i and j are positive integer, and 0＜i＜479,0＜j＜639, a (i, j) and b (i j) is the pixel value of image after the pixel value of input picture on this coordinate and the filtering respectively.For every bit, at first in its neighborhood, get the subregion of image, in each zone, calculate its average μ and variances sigma ², in the present invention, area size is set at 5 * 5 pixel windows.v ²The variance of expression noise is used the variances sigma of All Ranges here ²Average as noise variance.S filter can further be removed noise, shown in Fig. 6 (c).

Last filtering is to use the mean filter of 12 * 12 pixel windows to make image further level and smooth, and this is because the smoothness of the split image of hand back vein is had relatively high expectations.Have for 2D signal:

$d(i,j)=\frac{1}{12\&times;12}\underset{k=i-6}{\overset{i+6}{\mathrm{\&Sigma;}}}\underset{l=j-6}{\overset{j+6}{\mathrm{\&Sigma;}}}b(k,l)$

Wherein, i, j are the pixel coordinate of image, and i and j are positive integer, and 6≤i≤473,6≤j≤633, k, l are and i, the pixel coordinate of the image that j is relevant, b (k, l) and d (i j) is the pixel value of image after the pixel value of input picture on this coordinate and the filtering respectively; (i is at 12 * 12 pixel windows all input pixel b (k, mean values l) j) to the pixel value d of each output image.

Final output image is presented among Fig. 6 (d).Filtering method from Fig. 6 (d) among visible the present invention does not almost reduce the contrast of hand back vein image when removing noise.

Step 5: output final image;

Utilize designed hand back vein image capture device, the present invention has gathered the hand back vein image library.This storehouse comprises 16 people, everyone 10 width of cloth images, and typical image is as shown in Figure 7.

In actual applications, the every index of reflective-mode obviously not as mixed mode, will not adopt; Though and the transmission mode noise level is the highest, contrast is most important index, and noise can be suppressed by noise reduction process, so transmission mode is first-selected imaging pattern.But, because the unevenness of transmissible optical source descend in the position contrast near wrist, and the middle part light source position of palm is brighter; In addition, the design of transmitted light source is difficult to be applicable to the somebody of institute: if the volume of transmitted light source design is very big, light intensity is very strong, can cause the less thin woman's handball palm of palm to be exposed to light accidentally too much on every side, and central authorities forms speck, and contrast descends; If a little less than the mistake small offence of transmitted light source design, then for the big thicker male subject of palm, light is difficult to penetrate, and forms the dark space in volar edge; Even the light intensity of transmitted light source is adjustable, still be difficult to be applicable to various situations, need reflection source to be cooperated.Therefore, light source package of the present invention preferentially adopts transmitted light source; When transmission mode can not be satisfied the demand, open reflection source, use mixed mode.Little in application, the intensity of two kinds of light sources can just be controlled the adjusting of carrying out light intensity according to image quality by voltage; Improve voltage and can increase light intensity, otherwise can reduce light intensity.

Claims (6)

1. The vein collection system on the back of the hand. The system is composed of a reflected light source, a common CCD camera, a near-infrared filter, scattering paper, a handle and a transmitted light source. It is characterized in that: In this system, two sets of near-infrared light sources are used in combination, that is, the reflection light source (1) and the transmission light source (7) are used in combination, and there are three imaging modes: transmission mode, reflection mode or mixed mode; Among them, the transmission mode means that only the transmission light source is used, the reflection mode means that only the reflection light source is used; the mixed mode means that the transmission light source and the reflection light source are used at the same time; Two sets of near-infrared light sources, that is, the reflected light source (1) and the transmitted light source (7), irradiate the back of the hand (5) and the palm area respectively; wherein, the transmitted light source (7) is placed on the side of the palm, and the transmitted light source (7) emits The light enters the ordinary CCD camera (2) through the back of the hand (5); the reflected light source (1) is placed on both sides of the ordinary CCD camera (2), and the light emitted by the reflected light source (1) shines on the back of the hand (5) and is reflected back to the ordinary CCD camera (2). CCD camera (2); the dorsal hand vein image collected by the common CCD camera (2) is directly transmitted to the desktop computer, and the final image is obtained and output through noise reduction processing; Wherein, the transmitted light source (7) is installed on the handle (6), and the hand is held on the handle (6); the scattering paper (4) is placed in front of the reflected light source (1). 2. The dorsum of hand vein collection system according to claim 1, characterized in that, said common CCD camera (2) refers to a black-and-white camera capable of sensing near-infrared light. 3. The dorsum of hand vein collection system according to claim 1, characterized in that, said near-infrared filter (3) is a near-infrared all-pass filter. 4. The dorsum of hand vein collection system according to claim 1, characterized in that, said transmitted light source (7) and reflected light source (1) select full-band near-infrared diodes for use, and the wavelength that this diode sends is 600nm to 1100nm. 5. The method for collecting the dorsal hand vein by adopting the dorsal hand vein collection system described in any one of claims 1-4, is characterized in that the method comprises the steps of: Step 1: Selection of imaging mode in the dorsal hand vein collection system; The dorsal hand vein collection system provides three imaging modes: transmission mode, reflection mode or mixed mode; Step 2: Enter the transmission mode, reflection mode or mixed mode according to the selection result of step 1; Transmissive mode uses only the transmitted light source (7) on the palm side, reflective mode only uses the reflected light source (1) above the back of the hand (5), and mixed mode uses both the transmitted light source (7) on the palm side and the top of the back of the hand (5) Reflected light source(1); Step 3: Acquisition of the image of the dorsal hand vein according to the imaging mode selection result of step 2; According to the imaging mode that step 2 selects, utilize the video camera (2) of common CCD to realize the collection of the vein image of back of hand (5); Step 4: noise reduction processing of the collected image; Carry out denoising processing to the image gathered by common CCD camera (2) in step 3; Step five: output the final image; After the noise reduction processing in step 4, output the dorsal hand vein image that meets the requirements. 6. The method according to claim 5 that adopts the dorsal hand vein collection system described in any one of claims 1-4 to carry out the method for collecting veins on the back of the hand, wherein the noise reduction process adopts a three-time filtering method, The third filtering adopts matched filter, Wiener filter and mean filter respectively; The total width of the matched filter for the first filtering is 300 pixels, of which the pixels from the 150th to the 165th are high level, and the others are low level; let n be the pixel number, n is a positive integer, and n ∈[1,300], then a time series h[n] is obtained; the collected hand vein images are divided vertically into row vectors x[n] one by one, and each row vector is compared with the first matched filter. Dimensional convolution processing h[n]*x[n], each row vector is convolved to obtain a new image; then input the obtained new image to the second filter for further noise reduction processing; The filter for the second filtering is a Wiener filter, and the Wiener filter is an optimal linear filter designed according to the minimum mean square error criterion; The last filtering is a mean filter using a 12×12 pixel window to further smooth the image.

Images