WO2013093953A1

WO2013093953A1 - Biometric authentication device, blood vessel image photography device, and method

Info

Publication number: WO2013093953A1
Application number: PCT/JP2011/007061
Authority: WO
Inventors: 友輔松田; 晃朗長坂; 直人三浦; 春美清水; 孝文宮武
Original assignee: 日立オムロンターミナルソリューションズ株式会社
Priority date: 2011-12-19
Filing date: 2011-12-19
Publication date: 2013-06-27
Also published as: JP5923524B2; JPWO2013093953A1

Abstract

When photographing blood vessels with a plurality of image capture units with respect to one light source, it is difficult to establish the degree of light of the light source with which it is possible for the plurality of image capture units to clearly photograph the blood vessels simultaneously. Additionally, with a plurality of images which are photographed with different quantities of light, the positional relations of the blood vessels which are included in each image is uncertain, and information of the blood vessels overall configured by the plurality of images is uncertain. Provided is a blood vessel image photography device, with which a light quantity is controlled such that, with a first image capture unit which is positioned below a finger presentation unit and captures an image of blood vessels of the finger on the basis of light from a first light source which is transmitted through the finger, and on the basis of light which is transmitted through the finger from the first light source which is positioned to the side of the first image capture unit, a brightness value of an image of a portion of blood vessels which is captured with the first image capture unit and a brightness value of an image of a portion of blood vessels which is captured with a second image capture unit are brightness values within a first range, and the first image capture unit and the second image capture unit respectively capture images on the basis of the light from the first light source, the light quantity for which is controlled.

Description

Biometric authentication device, blood vessel imaging device, and method

The present invention relates to an apparatus and a method for identifying an individual using human biological information, particularly finger blood vessels.

With the growing interest in security technology for safely managing personal information and property, biometric authentication using human biometric information is attracting attention. As a conventional biometric authentication technique, an authentication method using a fingerprint, an iris, a voice, a face, a vein on the back of a hand, or a finger vein is known. In particular, vein authentication technology that uses absorption of hemoglobin in the blood of infrared light irradiated to the living body has low psychological resistance because authentication can be performed simply by illuminating the living body, and internal information of the living body is used. Therefore, it has the feature of being excellent in forgery resistance.

Biometric authentication is expected to be applied in various fields, and it is necessary to accurately identify tens of thousands to millions of users, and high authentication accuracy is required.

Therefore, it is required to increase the amount of information such as blood vessels that can be used for authentication for higher accuracy.

Patent Document 1 discloses a method of imaging a vein with imaging units arranged at a plurality of different positions with light from one light source.

Patent Document 2 describes a method of taking an image with a plurality of imaging units so as to include the same blood vessel.

Japanese Patent No. 434476 JP-A-11-203452

However, when a blood vessel is imaged with a plurality of imaging units with different arrangements for one light source, the device configuration such as the distance between each imaging unit and the light source, the influence of external light, the area of the living body imaged for each imaging unit Since the amount of light received by each imaging unit varies depending on the difference in the amount of light, the ratio of the contribution of the light amount differs in each imaging unit, and it is difficult to determine the light amount of a light source that can simultaneously capture a clear blood vessel by a plurality of imaging units. There was a problem.

Furthermore, in a plurality of images taken with different amounts of light, the positional relationship of the blood vessels included in each of the images becomes unclear, and it is impossible to accurately acquire information on the entire blood vessel constituted by the plurality of images. There has been a problem that the authentication accuracy may not be improved even if the amount of information is increased.

When a finger presenting unit on which a finger is presented, a first light source that irradiates light to the finger, and a side on which the finger is presented on the finger presenting unit are defined as upper, the finger is presented below the finger presenting unit, Based on the light from the first light source that has passed through the finger, the first imaging unit that images the blood vessel of the finger, and the first imaging unit that is disposed on the side of the first imaging unit and that has passed through the finger A second imaging unit that captures a part of a blood vessel imaged by the first imaging unit based on light from the light source, the first imaging unit, and the second imaging unit And a light amount control unit for controlling the light amount of the first light source, and the calculation unit picks up the image with the first image pickup unit. The luminance value of the partial image of the blood vessel and the luminance value of the partial image of the blood vessel imaged by the second imaging unit are The light quantity control means controls the light quantity so as to obtain a brightness value within the range, and the first imaging unit and the second imaging part are controlled by the first light source whose light quantity is controlled by the light quantity control means. The blood vessel imaging device is characterized in that the first image and the second image are respectively picked up based on the light.

According to the present invention, when a blood vessel is imaged with a plurality of imaging units with different arrangements with respect to one light source, the amount of light contributing to each imaging unit can be controlled so that a clear blood vessel can be imaged. The amount of information can be increased.

An example of the authentication apparatus which implements this invention. The system configuration example of the authentication apparatus which implements this invention. An example of the flowchart of light quantity control and exposure control which implement | achieves this invention. The relationship figure of the light quantity value of a light source, and a luminance value. The relationship figure of the light quantity value of a light source, and a luminance value. An example of the flowchart of light quantity control and exposure control which implement | achieves this invention. FIG. 5 is a relationship diagram of the light quantity value of an light source and exposure time and the degree of coincidence. An example when an abnormal posture of a finger is photographed from the side. An example of the authentication apparatus which implements this invention. An example of the authentication apparatus which implements this invention. An example of the authentication apparatus which implements this invention. An example of the flowchart of light quantity control and exposure control which implement | achieves this invention. An example of the authentication apparatus which implements this invention. An example of extracting the outline of a finger using whiteout. An example of the input interface which implement | achieves this invention. An example of the input interface which implement | achieves this invention. An example of the authentication apparatus which implement | achieves this invention. An example of arrangement | positioning of the light source and imaging part for image | photographing a clear blood vessel. Explanatory drawing regarding the tolerance | permissible_range of a luminance value. Explanatory drawing regarding a target luminance value. The flowchart regarding the synthesis | combination of two images after luminance value adjustment.

In the present embodiment, an example of the authentication apparatus 2 that simultaneously captures clear blood vessel images in two image capturing units by controlling exposure of two image capturing units and light amount control of a single light source will be described.

FIG. 1 is an example of an authentication device that implements the present invention, and FIG. 2 is a schematic diagram of the configuration of the authentication device of FIG. In the present apparatus configuration, by positioning the light source 3 on the upper side surface of the finger presentation unit 6, a configuration in which the finger presentation unit 6 is opened directly can be realized, so that the user can easily place the finger. In addition, an imaging unit 4-2 on the side facing the light source 3 and an imaging unit 4-1 arranged just below the finger presentation unit 6 are arranged.

User presents finger 1 to authentication device 2 during authentication. At this time, the finger 1 is placed on the finger placement guide 5. When the finger 1 is presented to the apparatus, the finger is detected using a detection unit such as a touch sensor (not shown), and authentication processing is started. Other sensors such as a distance sensor and a temperature sensor may be used for finger detection. In addition, an auxiliary light source can be used to detect finger presentation in a non-contact manner. The auxiliary light source 19 is disposed so as to irradiate upward from the position of the imaging unit 4-1, so that when the finger is presented above the finger placement guide unit 5, the finger is not touched by the finger. The light of the auxiliary light source 19 hits the light. Therefore, by imaging the finger illuminated brightly by the auxiliary light source 19, it is possible to detect the finger presentation in a non-contact manner.

Authentication is performed according to the following procedure. Infrared light is irradiated from the side surface of the finger 1 from the light source 3. The light amount of the light source is controlled by the light amount control unit 17, and the light passes through the finger 1, passes through the finger presentation unit 6 on which the authentication target area of the finger is presented, and passes through the optical filter 7 that transmits only infrared wavelength light. As a result, the imaging units 4-1 and 4-2 are reached. The exposure time of the imaging unit 4-1 and the imaging unit 4-2 is controlled by the exposure control unit 18. The light is converted into an electrical signal by the imaging units 4-1 and 4-2, and is taken into the computer 9 as an image via the image input unit 8. The captured image is once stored in the memory 11. Then, the blood vessel image (registration data) of the finger registered in advance is stored in the memory 11 from the storage device 12, and the CPU 13 collates the registered image with the input image by the program stored in the memory 11.

In the collation process, a correlation value between images to be compared is calculated, and it is determined whether or not it matches the registered image according to the value. An individual is authenticated in accordance with the result, and when the authentication is correctly performed, a process at the time of authentication is performed on the control target of the authentication system. As the authentication mode, 1-N authentication is performed to check all registered images, and an ID number is entered to identify the user in advance, or an IC card is presented to the card reader. In the 1-N authentication mode, authentication is started immediately after the finger is presented to the apparatus, but the authentication is 1-1. Then, after inputting the ID number using the input means 16, the finger is presented and authentication is performed.

Needless to say, the CPU, the memory, the storage device, the display unit, the light amount control unit, the exposure control unit, and the like can be stored in a terminal other than the authentication device 2.

The finger blood vessel image photographed by the imaging unit 4-1 is an image obtained by capturing blood vessels (finger blood vessels) existing under the skin on the palm side of the finger as a dark shadow pattern. A blood vessel pattern existing under the skin is imaged.

For the blood vessel image, the brightness of the blood vessel image to be imaged is determined by the amount of light transmitted from the light source 3 through the finger 1. When the amount of light is small, the entire image becomes dark, resulting in a low-contrast and unclear blood vessel image with a small difference in luminance value between the blood vessel pattern and other regions. If the amount of light is too large, the luminance value is saturated at the maximum value, resulting in a white blood vessel image. In order to prevent such a decrease in the image quality of the blood vessel image due to insufficient or excessive light amount and to capture a clear blood vessel image, the light amount of the light source 3 and the exposure time of the image capturing unit 4-1 and the image capturing unit 4-2 are determined. The light quantity control unit 17 and the exposure control unit 18 are controlled.

Hereinafter, an example of a flow from when the finger in the authentication device 2 is presented until a blood vessel image is captured is shown in FIG. First, in step S100, it is detected using the above-described detection means that a finger is presented to the apparatus, and in step S110, the light source is turned on with an initial light amount, and the luminance value in the image captured by each imaging unit in step S120 is calculated. calculate. Since the calculated luminance value includes the influence of different external light for each imaging unit, the exposure control of the imaging unit is performed so that the luminance values of all the images are close to each other in step S130. Next, light quantity control is performed. In the light amount control process, feedback control is performed so that the luminance value of the captured image becomes a constant value. Basically, the brightness value of the image when irradiated with a certain amount of light set in step S140 is calculated in step S150, and if the brightness values of all the images are within the allowable range in step S160, shooting is terminated. (S200). If the luminance value of one image is not within the allowable range, it is determined in step S170 whether or not the luminance value of all the images is likely to be within the allowable range only by adjusting the light amount of the light source. Return to S140 light control. If there is no expectation, the exposure control of each imaging unit is performed in step S180 while keeping the light amount of the light source as it is. Next, the exposure time is set for each imaging unit, the luminance value of the image captured in step S190 is calculated, and if the luminance value of all the images is within the allowable range in step S160, the imaging is terminated (S200). If not within the allowable range, the process returns to step S180, and exposure control of each imaging unit is performed again.

Here, the method of controlling the light amount will be described in detail. In this embodiment, as shown in FIG. 2, a plurality of imaging units shoot the blood vessel of the same finger from different viewpoints by irradiation of one light source. Since the imaging unit 4-2 is farther from the light source 3 than the imaging unit 4-1, the amount of light irradiated to the imaging unit 4-2 is smaller than that of the imaging unit 4-1, and the image becomes dark. is there. Further, the amount of light received by the imaging unit 4-1 and the imaging unit 4-2 varies depending on the shape and size of the finger. Under such circumstances, it is necessary to simultaneously bring the luminance values of the images captured by the imaging unit 4-1 and the imaging unit 4-2 close to the target value by controlling the light amount of one light source.

FIG. 4 shows a graph image in which the horizontal axis represents the light amount of the light source, and the vertical axis represents the luminance value of the image of the imaging unit 4-1 and the image of the imaging unit 4-2. Although FIG. 4 shows a linear graph for explanation, the actual luminance value varies nonlinearly depending on the distance between the light source and the imaging unit, the influence of external light, the movement of the presented finger, and the like. there is a possibility.

For example, when the light amount of the light source is doubled, the light amounts received by the imaging unit 4-1 and the imaging unit 4-2 are not doubled, but are a times and b times, respectively (in the example of FIG. 4A). a> b). Accordingly, the luminance value of the two images cannot be set to the target value at the same time regardless of the light amount value of the light source. Therefore, it is assumed that a target luminance value range (allowable range) is set and the luminance value is within the allowable range. In the example of FIG. 4B, the average light amount L3 of the light amount L1 of the light source where the image of the imaging unit 4-1 reaches the target luminance value and the light amount value L2 of the light source where the image of the imaging unit 4-2 reaches the target luminance value. If the luminance values of the two images are both within the allowable range when irradiating with, photographing is terminated. If any one of the two image luminance values is not within the allowable range, if there is a possibility that the luminance value of the two images will be within the allowable range only by adjusting the light amount value, then again When the light amount control is performed and there is no possibility that the light amount control only falls within the allowable range, the exposure control of the imaging unit 4-1 and the imaging unit 4-2 is performed.

As a method for quantitatively determining the allowable range of the luminance value, for example, when the luminance value of the image is expressed by 255 bits of 8 bits, the entire image becomes dark when the luminance value is a small value near 0, and the influence of noise is reduced. The blood vessel cannot be clearly photographed, and if the luminance value is large near 255, the luminance value is saturated and the entire image is overexposed, so that the blood vessel information is lost. In order to acquire more, it is desirable to set an allowable range of luminance values in a range that is not easily affected by noise and that does not saturate the luminance values. For example, the allowable range of the luminance value can be set in the range of 50 to 200.

Even within the allowable range, by setting a target luminance value that is particularly suitable for capturing a clear image and controlling the luminance value to be as close as possible to this target luminance value, more accurate light intensity control is possible. . As a method for setting the target luminance value, it is desirable to set the luminance value so that the influence of noise is small in the blood vessel image and the contrast between the blood vessel and the background is large in the image. That is, it is desirable that the S / N ratio, which is the ratio of the signal and noise when the blood vessel information in the image is a desired signal and the other is noise, is increased. Specifically, when the region in the captured image is divided into a blood vessel region and a background region, the luminance value at which the calculated SN ratio is maximized or the minimum luminance value at which the SN ratio is saturated is set as the target luminance value. be able to. This will be specifically described with reference to FIG. As the luminance value of the image increases, the blood vessel becomes clearer and the influence of noise becomes smaller, so the SN ratio also increases. However, when the luminance value a is reached, the SN ratio becomes almost constant. At this time, although the influence of noise can be suppressed to the maximum when the luminance value is larger than the luminance value a, as the luminance value approaches the saturated value, the overexposed area increases in the image and the blood vessel area is lost. It shows that it will be filmed. Therefore, if the vicinity of the luminance value a is set as the target luminance value, it is possible to acquire a clear blood vessel image with no loss of blood vessel information while suppressing the influence of noise to the maximum. Quantitatively, it is desirable to set the target luminance value near 128.

Further, among the two images, the light amount may be controlled so that the luminance value of the blood vessel image in a particularly wide range preferentially approaches the reference value within the allowable range. As a result, a larger amount of information can be acquired for the two images as a whole.

For example, assuming that the cross-sectional shape of the finger is an ellipse, the largest amount of information can be obtained because the finger width is maximized when the ventral side of the finger is photographed. Therefore, even when the finger rotates around the long axis of the finger, the amount of light so that the difference between the luminance value of the image of the imaging unit with a large finger area to be imaged and the target luminance value is smaller than that of the other image. Take control.

In this way, the CPU 13 measures the widths of the fingers captured by the imaging unit 4-1 and the imaging unit 4-2, determines that the ventral side of the finger is facing the larger imaging unit, and determines the finger width. By preferentially bringing a large image close to the target luminance value, it is possible to more reliably acquire blood vessel information with a large amount of information and achieve stable authentication accuracy.

Also, determine the finger area. The outline of the finger or the like may be extracted, and the inside of the outline may be determined as the finger area. Alternatively, blood vessel information may be extracted from an image taken before controlling the light quantity, and the light quantity may be controlled with priority given to an image with more feature information.

Next, an exposure control method will be described. Even if the light quantity of the light source is set to any value as shown in FIG. 5A, there are cases where the luminance values of the two images are not within the allowable range. In such a case, a clear blood vessel image cannot be simultaneously captured by the imaging unit 4-1 and the imaging unit 4-2 only by the light amount control. Therefore, as shown in FIG. 5B, the exposure of the imaging unit 4-1 and the imaging unit 4-2 is controlled, and the luminance values of the images of the two imaging units are obtained when the light amount value of the light source is a certain value. The exposure time is set so that both values become target values. As shown in FIG. 5C, the exposure is controlled by fixing the exposure of the imaging unit 4-2 with a small amount of received light, and the light intensity value of the light source at which the luminance value of the image of the imaging unit 4-2 becomes a target value. The brightness value of the two images may be set as the target value by adjusting the exposure time of the imaging unit 4-1. Further, as shown in FIG. 5D, the exposure of the imaging unit 4-1 having a large amount of received light may be fixed and the exposure of the imaging unit 4-2 may be adjusted longer.

With the above light amount control and exposure control, when a blood vessel is imaged with a plurality of imaging units with different arrangements with respect to one light source, the ratio of the amount of light contributed by each imaging unit differs. The difficulty of determining the amount of light can be eliminated, and a clear blood vessel can be photographed.

In the first embodiment, the method for controlling the light amount and the exposure amount so that the luminance value of the entire image is within the allowable range has been described. However, in this embodiment, as another determination criterion when performing the light amount control and the exposure control. A method of controlling the light amount / exposure amount of the common area of the images captured by the image capturing units 4-1, 4-2 will be described.

For example, when the image capturing units 4-1 and 4-2 are arranged close to each other as shown in FIG. 2, there is a region where the two image capturing units capture images in common. Since the common area in the image captures the same target, for example, if the light intensity is controlled based on the average luminance value of the common area of each image to set the luminance value within the allowable range, the contrast of the target image is It becomes almost the same.

On the other hand, if the amount of light is controlled based on the average luminance value of the entire image, the target is different, so even if each image has a luminance value within the allowable range, there is a slight difference in the contrast of the target. This makes it difficult to associate images between wide-angle images, which will be described later.

Therefore, by setting the luminance value of the common area in the image within the allowable range as described above, the difference between the luminance values of the two images can be reduced, and blood vessel information can be extracted with high accuracy. Become.

Furthermore, blood vessel information can be extracted with higher accuracy by performing light quantity control using the luminance value near the blood vessel in the common region in the image. The CPU 13 extracts a blood vessel from each common area in the two images. The light amount control unit 17 controls the light amount so that the luminance value in the vicinity of the extracted blood vessel or the contrast of the luminance value is within the allowable range, and the luminance of the image is adjusted based on the blood vessel information used for collation. As described above, by performing luminance adjustment based on the same blood vessel, that is, the same object, in the common region of the images, it is possible to realize luminance adjustment in which the difference in contrast between the two images becomes smaller. As a result, the difference between the luminance values of the same blood vessels included in each of the two images can be further reduced, so that the two images can be associated with each other with high accuracy as well as high-precision matching.

The procedure for associating two images and creating a composite image will be described with reference to FIG. First, after completion of imaging (S200), blood vessel information included in the common area is extracted (S210). Furthermore, collation is performed using the blood vessel information of this common area. As matching means, pattern matching, feature point matching, or the like can be used. At this time, since the two images are misaligned due to the influence of the imaging angle, the distance between the finger and the imaging unit, etc., it is necessary to correct the position of the blood vessel in the common region in order to perform collation.

Therefore, the X-axis and Y-axis when the two-dimensional plane of the blood vessel image when the matching degree by the matching of the two blood vessel images is the maximum or the threshold TH2 or more is the X and Y coordinates and the depth direction is the Y coordinate. , For each of the Z-axis directions, the positional deviation in the common area is calculated with the position coordinates (S220). Finally, based on the position coordinates, the displacement of the entire two images is corrected to create one wide-angle image (S230).

As described above, by using the degree of coincidence of the blood vessel images in the common region acquired by the accurate light amount control, it is possible to create a wide-angle image in which the positional relationship of the blood vessels is more accurately associated.

Note that a specific method of light amount control, exposure control, and a method of setting a range of luminance values are the same as those in the first embodiment, and thus description thereof is omitted here.

As described above, blood vessel information can be acquired more accurately by adjusting the amount of light using the luminance value of the image included in the common area of the two images, so that highly accurate authentication is possible.

The adjustment of the luminance value based on the blood vessel image in the common region of the two images in the second embodiment focuses on equalizing the contrast of the two images and associating the two images for creating a wide-angle image. Therefore, it is desirable to perform more precise light amount control in order to acquire blood vessel information used for final authentication.

Therefore, in this embodiment, in order to further improve the final authentication accuracy, a method for preferentially controlling the luminance value of an image having a larger finger area and having more blood vessel information will be described with reference to FIG. Details will be described.

The CPU 13 first controls the light amount by the light amount control unit 17 so that the luminance value of the common area of the two images is within the first allowable range. Next, the light amount control is performed so that the luminance value of the image having the wider finger area within the two images falls within the second allowable range set within the first allowable range. As a result, it is possible to acquire a larger amount of blood vessel information used for authentication as two images as a whole.

The target image whose luminance value is adjusted to be in the second range can be the entire image with the wider finger area, but it is more accurate if the target finger area in the image is targeted. Blood vessel information can be acquired well. Furthermore, blood vessel information can be acquired with higher accuracy by extracting a blood vessel from the finger region in the image and adjusting the luminance value so that the blood vessel region is the second range.

The first range is a permissible range of luminance values to which the blood vessels in the common region can be associated with each other in order to create a wide-angle image by connecting two images, while the second range is a blood vessel used for authentication. This is an allowable range of the luminance value that requires a stricter setting for extracting information. Therefore, it is desirable that the second range is set in a narrower range within the first range.

Quantitatively indicating the first range with a luminance value of 255 gradations, a luminance value of 30 or more and 200 or less is desirable for associating two images. Furthermore, since it is desirable that the variation range of the luminance value be small as described above, the second range is desirably 80 or more and 150 or less.

The quantification of the light amount control method and 255 gradation model of this embodiment is merely an example. For example, the second range is set by the difference from the target luminance value as in the first embodiment, or the 255th floor is set depending on the imaging environment or the like. It is also possible to change the range setting by the tone model.

Further, in this embodiment, after controlling the luminance value of the image of the common area of the two images within the first allowable range, a method for controlling the image having the wider finger area to the second allowable range will be described. However, it is also possible to control the luminance value of the common area of the narrower image of the finger to the first allowable range after controlling the image of the wider finger area to the second allowable range. .

In this embodiment, as another embodiment using the light amount control method using the luminance value of the blood vessel image in the common area described in the second embodiment, the blood vessel images are collated with each other as a collation result. A method of performing light amount control and exposure control based on the degree of coincidence obtained will be described.

FIG. 6 shows an example of a processing flow of light amount control and exposure control using the degree of coincidence. First, in step S300, it is detected that a finger has been presented. Next, in step S310, the light source is turned on with the initial light amount, and in step S320, the common regions of the blood vessel images photographed by the imaging unit 4-1 and the imaging unit 4-2 are collated to calculate the degree of coincidence. As matching means at this time, pattern matching between common areas of the captured multi-value luminance grayscale image, matching between blood vessel patterns extracted from the luminance grayscale image, feature point matching, or the like can be used. In step S330, if the degree of coincidence is greater than the threshold value TH1, shooting is terminated (S370). If the degree of coincidence falls below the threshold value TH1, the light amount control is performed in step S340. In step S350, when it is expected that the degree of coincidence exceeds the threshold value TH1 only by the light amount control, the process returns to step S320. If there is no expectation, exposure control of each imaging unit is performed in step S360, and the process returns to step S320.

The light amount control in step S340 will be described. FIGS. 7A and 7B schematically show graphs representing the relationship between the light amount value of the light source and the degree of coincidence and the relationship between the exposure time of the imaging unit and the degree of coincidence. As shown in this graph, when the amount of light is gradually increased, many blood vessel images appear, and the amount of information used for matching increases, so the degree of matching increases. However, after the coincidence reaches the maximum value, that is, after the largest amount of blood vessel information appears, whiteout occurs in the image, and the amount of blood vessel information decreases, so the degree of coincidence gradually decreases. Accordingly, as shown in FIG. 7A, the degree of coincidence is small regardless of whether the light amount is larger or smaller than the light amount value at which the degree of coincidence is maximum.

Therefore, when the degree of coincidence calculated at a certain light amount value is below the threshold value TH1, it is difficult to determine whether to increase or decrease the next light amount value. Therefore, the relationship between the luminance value and the light amount value of the light source as shown in FIG. 4A can be used for the determination for determining the next light amount value. It is considered that the closer the luminance values of the images of the imaging unit 4-1 and the imaging unit 4-2 are to the target range, the clearer the blood vessels can be taken and the closer the brightness of the images, the higher the matching degree. Therefore, if the luminance value of the image of one imaging unit is too small, the light amount is increased, and conversely if the luminance value is too large, the light amount is decreased. Further, when the difference between the luminance values of the two imaging units is large, the light amount value can be controlled so that the degree of coincidence increases by increasing or decreasing the light amount value so that the difference between the luminance values becomes small. Further, as shown in FIG. 7 (c), the amount of coincidence with respect to the variation in the light amount value of the light source and the exposure time is estimated to determine the amount of light so that the coincidence is maximized, and the actually calculated coincidence is the threshold TH1. You may set the light quantity value and exposure time when exceeding. Further, as a light amount control method, it is possible to estimate the graph shape as shown in FIG. 7A from the coincidence degree calculated by irradiating with different light amount values, and to determine the light amount value when the coincidence degree is maximum. is there.

If the imaging unit 4-1 and the imaging unit 4-2 are arranged so as to capture the common area of the finger or set the imaging range, two images can be obtained by using the matching degree of the blood vessel images in the common area. Can be associated with each other. If the correct association is possible, one wide-angle image in which the periphery of the finger is photographed by combining the two images can be created. Even if the images are not combined, if the correspondence between the positions in the two images is known, the data can be acquired as a single piece of linked data, and matching between images can be efficiently performed. it can.

Here, an example of collation processing in the present invention will be described. The CPU 13 associates two blood vessel images photographed by the imaging unit 4-1 and the imaging unit 4-2, and performs synthesis. Features extracted from the combined image are registered, and collated with the features extracted from the combined image of the two blood vessel images input at the time of authentication. Alternatively, the input blood vessel image may be used as connection data without being synthesized, and a feature may be extracted from each of the two blood vessel images and collated with a registered feature. As the feature to be extracted, a blood vessel pattern, a feature point, or the like used for associating a region to be photographed in common by two adjacent imaging units can be used.

In this embodiment, there are two imaging units, and two blood vessel images can be used for both the registered image and the input image. However, not all images need to be used for collation. For example, two images can be used as registered images, and only one of the two images can be used as an input image. It is also possible to use a registered image as one image and use both two images as input images.

In this embodiment, the abnormal posture of the finger can be detected by using the blood vessel image taken by the imaging unit and the image taken from the side of the finger. Here, as an example, a method for detecting an abnormal posture of a finger using a blood vessel image on the ventral side of the finger imaged by the imaging unit 4-1 and a side image of the finger imaged by the imaging unit 4-2 will be described. Finger abnormal postures that are difficult to detect with only the imaging unit 4-1 that captures the ventral side of the finger include finger pressing, bending, and warping. In the pressing, the finger presentation position is not significantly different from the normal presentation position, the blood flow in the vicinity of the finger surface is inhibited near the position where the device contacts the finger, and blood vessels cannot be imaged. The pressing can be detected to some extent by the amount of blood vessels in the vicinity of the contact position between the finger and the device in the blood vessel image of the imaging unit 4-1, but it is difficult to distinguish from the case where no blood vessel originally exists. Therefore, the pressing can be detected more accurately by the combination of the finger posture known from the finger side surface image captured by the image capturing unit 4-2 and the blood vessel amount in the blood vessel image captured by the image capturing unit 4-1. When the finger is pressed against the device, the finger taken from the side is lower in the contour position of the lower side of the finger than the finger placement guide compared to the case of correctly presenting, and the fingertip from the finger base It tends to be a shape in which the lower contour is convex downward. Thus, pressing is detected when the amount of blood vessels at the contact position between the device and the finger is small and the contour position and contour shape of the finger are abnormal. In addition, when the finger is presented in a bent state or a warped state, it is difficult to detect an abnormality from the blood vessel image captured by the imaging unit 4-1. However, an abnormality can be detected relatively easily from an abnormality in the position and shape of the upper and lower contours of the finger as shown in FIG.

The authentication device 2 in FIG. 9 has a configuration in which a light source is arranged right above a finger to be presented, and two imaging units are arranged on both side surfaces of the finger presentation unit 5. At this time, since the two imaging units are in symmetrical positions when viewed from the finger when correctly presented directly under the light source 3, the received light amounts are equal. Therefore, if light intensity control and exposure control are performed and a clear blood vessel image can be captured in one imaging unit, a clear blood vessel image can be similarly captured in the other imaging unit. For this reason, a clear blood vessel image can be acquired simultaneously from two imaging units by simply performing light amount control and exposure control on one imaging unit.

In the present embodiment, an example of the authentication apparatus 2 that simultaneously captures three clear blood vessel images by exposure control of three imaging units and light amount control of a single light source will be described.

By using three imaging units as in the present embodiment, it is possible to acquire blood vessel images in a wider range.

The authentication apparatus 2 in FIG. 10 has a configuration in which one more imaging unit is added to the authentication apparatus 2 in FIG.

Even if the number of imaging units is three, the light amount control and exposure control methods are basically the same as those in the first embodiment. In order to photograph clear blood vessels simultaneously with the three imaging units, the light amount control of the light source and each The exposure control of the imaging unit is performed in combination.

The authentication device 2 in FIG. 11 has a configuration in which an imaging unit just below the finger is added to the configuration of the authentication device 2 in FIG. In this configuration, when the finger is correctly presented on the presentation unit 5, the irradiation light from the light source 3 is the same amount of light in the imaging unit 4-2 and the imaging unit 4-3 arranged symmetrically when viewed from the light source 3 and the finger. It will receive light. Therefore, the imaging unit 4-2 and the imaging unit 4-3 can be regarded as one imaging unit, and the imaging unit 4-1 and the imaging unit 4-2 or the imaging unit 4-1 and the imaging unit 4-3 are two. Thus, if a clear blood vessel image can be captured simultaneously, clear blood vessel images can be captured simultaneously by the three imaging units.

FIG. 12 shows an example of a processing flow of light amount control and exposure control in the authentication apparatus of FIG. First, in step S400, it is detected that a finger has been presented. In step S410, the light source is turned on with an initial light amount, and in step S420, the luminance value in the image captured by each imaging unit is calculated. Since the calculated luminance value includes the influence of different external light for each imaging unit, the exposure of the imaging unit is controlled in step S430 so that the luminance values of all the images are close to each other. Next, the amount of light is controlled to capture a clear blood vessel in each imaging unit. First, the amount of light is controlled in step S440 in order to photograph a clear blood vessel by the imaging unit 4-1 alone, and the luminance value of the image of the imaging unit 4-1 is calculated in step S450. If the luminance value is within the allowable range in step S460, the imaging of the imaging unit 4-1 is terminated (S470). Next, in step S480, the imaging unit 4-2 and the imaging unit 4-3 perform light amount control for acquiring a clear blood vessel at the same time, and in step S490, the luminance values of the images of the imaging unit 4-2 and the imaging unit 4-3. Calculate If the luminance value is within the allowable range in step S500, the imaging of the imaging unit 4-2 and the imaging unit 4-3 is terminated (S510). Regarding the light amount control in step S480, as described above, since the light amounts received by the imaging unit 4-2 and the imaging unit 4-3 are substantially equal, the light amount is adjusted so that blood vessels can be clearly imaged by one imaging unit. All you need to do is control.

In this embodiment, an example of the authentication apparatus 2 that captures a clear blood vessel image with three image pickup units by exposure control of three image pickup units, light amount control of two light sources, and turning on / off control will be described.

By controlling the light amounts of the two light sources as in the present embodiment, it becomes possible to capture a clearer image over a wide range and to accurately associate each image.

FIG. 13 shows an authentication device 2 composed of two light sources and three imaging units. First, blood vessels are imaged by alternately illuminating two light sources 3 arranged on the left and right. When one of the light sources 3 is turned on, the other light source 3 is turned off or turned on with a light amount that is weaker than the light amount of the light source that is turned on.

In the configuration of the authentication apparatus 2 in FIG. 13, either the imaging unit 4-2 or the imaging unit 4-3 captures an image of a portion where the light emitted from the light source 3 directly hits the finger surface. The received light amount of the part becomes excessive, the luminance value is saturated, and overexposure occurs. In FIG. 13, when the light source 3 on the left side is turned on, the most part of the finger imaged by the image capturing unit 4-3 and the half surface of the finger region imaged by the image capturing unit 4-1 are overexposed to image a blood vessel. Can not do it. The remaining half of the finger region imaged by the image capturing unit 4-1 and most of the finger region imaged by the image capturing unit 4-2 can receive light transmitted through the inside of the finger and image the blood vessel. When the right light source 3 is turned on, blood vessels can be photographed on most of the finger region photographed by the image capturing unit 4-3 and on the half surface of the finger region photographed by the image capturing unit 4-1. Therefore, the image of the image capturing unit 4-2 when the left light source 3 is lit and the image of the image capturing unit 4-3 when the right light source 3 is lit are selected from the six images captured with the left and right light sources 3 turned on. Since the image of the imaging unit 4-1 is selected and blood vessels are photographed for each of the left and right half surfaces, the two images for each of the left and right half surfaces are combined to create one blood vessel image. Therefore, three images are selected as blood vessel images.

Regarding the light amount control of the light source, the light amount of the left light source 3 is controlled based on the blood vessel images photographed by the two imaging units 4-1 and 4-2 that can photograph the blood vessel, and the light amount of the right light source 3 is imaged. Control is performed by the unit 4-1 and the imaging unit 4-3. As a specific light amount control method, the method described in the first embodiment can be used.

Furthermore, it is possible to acquire blood vessel information with higher accuracy by extracting the outline of the finger using the overexposure in the imaging unit where the blood vessel cannot be imaged when the light source is turned on.

In the example of FIG. 13, when the light source 3 on the left side is turned on, the image capturing unit 4-3 captures reflected light from the surface of the finger, and whiteout occurs. At this time, by appropriately controlling the amount of light, the overexposure emphasizes the boundary between the outline of the finger and the background as shown in FIG. 14A. If the amount of light is too strong at this time, the overexposure occurs as shown in FIG. Since the area to be exceeded exceeds the actual finger area, the finger is irradiated with a light amount that emphasizes the outline of the finger in order to extract the outline, and the outline position of the finger is obtained.

With respect to the light amount control for photographing the outline of the finger, the brightness method contrasts between the finger and the background in the vicinity of the boundary between the finger and the background from the overexposed image by the control method described in the first embodiment. There is a method of adding to the control condition that the amount of light is controlled so as to be clearly distinguishable.

In addition to imaging with another imaging unit that captures an image of a blood vessel, it is also possible to control the amount of light so that the luminance value is within an allowable range for acquiring a contour.

Furthermore, as another image capturing method of the contour, when the light source arranged on the side is slightly above the finger to be presented as shown in FIG. 13, it is difficult to directly reach the lower side of the finger. There is a method of using an auxiliary light source 19 for finger detection arranged directly below the guide unit 5. By irradiating the abdominal side of the finger, when the side surface of the finger is photographed by the imaging unit 4-2 and the imaging unit 4-3 as shown in FIG. Since it is emphasized, accurate contour extraction becomes possible.

The contour image extracted using whiteout is photographed with a light amount suitable for contour enhancement, and thus has a sharper contour image than the contour of the image obtained by imaging the blood vessel. A method of acquiring a more accurate blood vessel image using this will be described below using an image captured by the imaging unit 4-3 as an example.

First, the imaging unit 4-3 captures an image based on the light emitted from the left light source 3. As described above, the image photographed at this time is an image that can generate an overexposed image, and at the same time, an image in which the contour of the finger is emphasized.

Next, the imaging unit 4-3 captures an image based on the light emitted from the right light source 3. As described above, the image taken at this time is an image including a blood vessel image.

The CPU 13 collates the two images or creates a composite image, and exists in the area inside the outline, that is, the finger area, of the image in which the outline is emphasized from the image including the blood vessel image. Extract blood vessel images.

As a result, blood vessels existing within the contour can be extracted more reliably, so that information that may be erroneously recognized as a blood vessel pattern existing outside the contour, for example, included in an image obtained by photographing the blood vessel pattern is excluded. This makes it possible to extract a more accurate blood vessel image.

Further, the CPU 13 uses the blood vessel image in the common region in the two images of the extracted blood vessel image in the contour and the blood vessel image captured by the imaging unit 4-1, in the second and third embodiments. Using the light amount control / exposure control method described above, the light amount is controlled so that the luminance value of the blood vessel image in the common region is within the allowable range, and an image used for authentication is captured.

As described above, by performing the light amount control using the blood vessel image in the outline, a clearer blood vessel image can be taken and the authentication accuracy can be improved.

Next, in Embodiments 1 to 3, using the luminance value of the blood vessel image in the extracted contour and the luminance value of the blood vessel included in the common area of the blood vessel image captured by the imaging unit 4-1. The described light quantity control is performed. In this embodiment, since the light amount control is performed on the blood vessel image in the contour, the probability of determining the luminance value by recognizing noise or the like as a blood vessel can be suppressed, and the accuracy of the light amount control is further improved. It is increasing.

Further, the same processing is performed on the image acquired by the imaging unit 4-2, and the images acquired by the imaging unit 4-1, the imaging unit 4-2, and the imaging unit 4-3 are used as described above. By creating a composite image of three composite images, it is possible to acquire a wide-angle image in which the association between the brightness value and each image is accurately controlled.

In this embodiment, an interface for further clarifying images picked up by a plurality of image pickup units in the first to sixth embodiments described above will be described.
FIGS. 15A and 15B show a configuration example of the input interface of the personal authentication device in which the light source 3 is arranged so that the imaging unit that captures the side surface of the finger captures a clear blood vessel image. FIG. 15 (b) is a view of the input interface (side view) of FIG. 15 (a) from above, and FIG. 15 (d) is a view of the input interface (side view) of FIG. 15 (c) from above. ). When a finger is photographed from the side, the finger thickness is smaller on the fingertip side than on the finger base side. Therefore, as shown in FIG. 15C, when a plurality of light sources 3 are arranged side by side in the major axis direction of the finger presentation unit 6, the irradiation light of the light source 3 directly hits the finger. ), The overexposed area may become larger at the fingertips and the image may be taken from the side. Therefore, considering that the thickness of the finger is reduced toward the fingertip, the light source is gradually arranged in the major axis direction of the finger presentation unit 6 from one end to the other end on the fingertip side as shown in FIG. Move down the position. This arrangement of the light sources makes it difficult for the imaging unit that captures the finger side surface to capture overexposure. Further, in order to obtain the same effect, the finger presentation unit 5 may be arranged to be inclined and the imaging unit may be arranged to be inclined without changing the position of the light source 3 as shown in FIG.

As described above, by appropriately irradiating the finger with the light from the light source, it is possible to suppress whiteout that occurs when light that has not been transmitted to the finger enters the imaging unit disposed on the side of the finger presentation unit. In addition, it is possible to increase the amount of light incident on the imaging unit disposed below the finger presentation unit and transmitted through the finger.

In the present embodiment, another embodiment of the embodiment 7 in consideration of the presented finger shake will be described. As an example, a case will be described in which the present invention is applied to an authentication apparatus 2 that captures a clear blood vessel image with three image pickup units by exposure control of three image pickup units, light amount control of two light sources, and turning on / off control.

As shown in FIG. 17, an example of the authentication device 2 is described in which the finger next to the finger to be authenticated contacts and is fixed to the device, and the finger to be authenticated is bent and presented in a non-contact manner. The apparatus is composed of three imaging units and two light sources, and the blood vessel imaging method can be performed in the same manner as in the other embodiments.

18A, 18B, and 18C are cross-sectional views of the authentication device of FIG. FIG. 18A is an example in which a plurality of light sources are arranged in the longitudinal direction of the finger presentation unit 6, and FIG. 18B is an example in which the light sources are inclined and arranged in accordance with the position of the finger that is bent and presented. is there. FIG. 18C shows an example in which a large number of light sources are arranged and a light source to be lit is selected in accordance with the presented finger position. 18 (d), (e), and (f) are presented by bending a finger, so that each imaging unit in FIGS. 18 (a), (b), and (c) is tilted according to the direction in which the finger is bent. This is an example of arrangement.

In this way, by changing the light source that emits light to the finger according to the presented finger position, it is possible to suppress the influence of overexposure and stably image the transmitted light from the finger. Highly accurate authentication is possible.

In the first to seventh embodiments, the blood vessel is described as the biological information. However, the device is not limited to the blood vessel as long as the device is intended to capture the biological information with a plurality of imaging units.

DESCRIPTION OF SYMBOLS 1 Finger 2 Authentication apparatus 3 Light source 4 Image pick-up part 5 Finger placement guide part 6 Finger presentation part 7 Shading filter 8 Image input part 9 Computer 10 Interface 11 Memory 12 Storage device 13 CPU
14 Display unit 15 Speaker 16 Input unit 17 Light amount control unit 18 Exposure control unit 19 Auxiliary light source

Claims

A finger presentation unit where the finger is presented;
A first light source that illuminates the finger;
When the side on which the finger is presented to the finger presentation unit is defined as upper,
A first imaging unit that is disposed below the finger presentation unit and images a blood vessel of the finger based on light from the first light source that has passed through the finger;
Based on the light from the first light source disposed on the side of the first imaging unit and transmitted through the finger, the imaging is performed so as to include a part of the blood vessel imaged by the first imaging unit. A second imaging unit;
A calculation unit that calculates the luminance values of the images captured by the first imaging unit and the second imaging unit;
A light amount control means for controlling the light amount of the first light source;
Have
The computing unit is
The luminance value of the partial image of the blood vessel imaged by the first imaging unit and the luminance value of the partial image of the blood vessel imaged by the second imaging unit are the first value. Causing the light amount control means to control the light amount so that the luminance value is within a range;
The first imaging unit and the second imaging unit are:
A blood vessel image capturing apparatus that captures a first image and a second image based on light from the first light source, the light amount of which is controlled by the light amount control means.
The computing unit is
Collating an image of a portion of the blood vessel contained in each of the first image and the second image;
2. The blood vessel according to claim 1, wherein the position coordinates of the first image and the position coordinates of the second image when the degree of coincidence is a predetermined value or more as a result of the collation are calculated. Image shooting device.
The computing unit is
The blood vessel according to claim 2, wherein a composite image of the first image and the second image is created based on the position coordinates of the first image and the position coordinates of the second image. Image shooting device.
The computing unit is
The blood vessel image capturing apparatus according to claim 3, wherein collation between the synthesized image and an image registered in advance is executed.
The computing unit is
Of the image captured by the first imaging unit and the image captured by the second imaging unit,
The light quantity control unit controls the light quantity so that a luminance value of an image having a larger finger area falls within a second range set in the first range. Item 1. A blood vessel imaging device according to Item 1.
The computing unit is
Calculating a difference between a reference value in the first range and a luminance value of an image captured by the first imaging unit;
Calculating a difference between the reference value and a luminance value of an image captured by the second imaging unit;
Of the image captured by the first imaging unit and the image captured by the second imaging unit,
The amount of light is controlled by the light amount control means so that the difference between the luminance value of the image having the larger area of the finger region and the reference value is smaller than the difference between the luminance value of the other image and the reference value. 2. The blood vessel image photographing device according to claim 1, wherein the blood vessel image photographing device is controlled.
Exposure control means for controlling the exposure amount of the first imaging unit and the second imaging unit;
The computing unit is
A luminance value of a partial image of the blood vessel included in each of the images captured by the first imaging unit and the second imaging unit by the exposure control unit is a luminance within the first range. The blood vessel image capturing apparatus according to claim 1, wherein the exposure amount of the first imaging unit and the exposure amount of the second imaging unit are controlled so as to be values.
The first light source is disposed above and laterally with respect to the finger presentation unit,
The blood vessel image capturing apparatus according to claim 1, wherein the second imaging unit is disposed below the finger presentation unit and on a side opposite to the first light source.
A second light source disposed on the side opposite to the first light source with respect to the finger presentation unit;
The computing unit is
Let the light quantity control unit control the light quantity of the second light source,
The second imaging unit is
The blood vessel image photographing device according to claim 8, wherein a contour of a finger is imaged based on light from the second light source.
The computing unit is
Creating a composite image of the finger blood vessel image and the finger contour image captured by the image capturing unit of the second image capturing unit;
Extracting an image of a part of the blood vessel contained inside the outline of the finger from the composite image,
A luminance value of a partial image of the blood vessel included inside the extracted finger contour and a luminance value of the partial image of the blood vessel included in the image captured by the first imaging unit. 10. The blood vessel image capturing apparatus according to claim 9, wherein the light amount is controlled by the light amount control means so that the luminance value is within the first range.
A plurality of light sources including the first light source;
The plurality of light sources are
The blood vessel image capturing apparatus according to claim 1, wherein a distance from the finger presentation unit to the upper side increases from one end in the longitudinal direction to the other end of the finger presentation unit.
The distance between the second imaging unit and the first light source is arranged to be longer than the distance between the first imaging unit and the first light source. The blood vessel image photographing device according to claim 1.
A finger presentation unit where the finger is presented;
When the side on which the finger is presented to the finger presentation unit is defined as upper,
A first light source disposed above and laterally with respect to the finger presentation unit;
A second light source arranged to face the first light source via the finger presenting unit upward and laterally with respect to the finger presenting unit;
A first imaging unit that is disposed below the finger presentation unit and that images a blood vessel of the finger based on light from the first light source or the second light source transmitted through the finger;
First imaged by the first imaging unit based on the light from the second light source that is disposed on the side of the first imaging unit and below the first light source and transmitted through the finger. A second imaging unit for imaging so as to include the blood vessel portion of
The second imaged by the first imaging unit based on the light from the first light source that is disposed beside the second imaging unit and below the second light source. A third imaging unit for imaging so as to include a blood vessel part;
Arithmetic units for calculating the luminance values of the images captured by the first imaging unit, the second imaging unit, and the third imaging unit, respectively;
A light amount control means for controlling the light amount of the first light source and the light amount of the second light source;
Have
The computing unit is
The luminance value of the image of the first blood vessel part imaged by the first imaging unit and the luminance value of the image of the first blood vessel part imaged by the second imaging unit are within a predetermined range. The amount of light from the second light source is controlled by the amount of light control means so that the brightness value becomes,
The luminance value of the image of the second blood vessel part imaged by the first imaging unit and the luminance value of the image of the second blood vessel part imaged by the third imaging unit are within the predetermined range. The amount of light from the first light source is controlled by the light amount control means so that the luminance value is within,
The first imaging unit and the second imaging unit capture a first image and a second image, respectively, based on light from the second light source whose light amount is controlled by the light amount control unit,
The first imaging unit and the second imaging unit are:
A blood vessel image capturing apparatus, wherein a third image and a fourth image are respectively captured based on light from the first light source whose light amount is controlled by the light amount control means.
The computing unit is
Collating images of the first blood vessel portion included in each of the first image and the second image;
As a result of the collation, the position coordinates of the first image and the position coordinates of the second image when the degree of coincidence is a predetermined value or more are calculated,
Collating images of the second blood vessel portion included in each of the third image and the fourth image;
As a result of the collation, when the degree of coincidence is a predetermined value or more, the position coordinates of the third image and the position coordinates of the fourth image are respectively calculated,
The blood vessel image photographing device according to claim 13.
The computing unit is
Based on the position coordinates of the first image and the position coordinates of the second image, create a first composite image of the first image and the second image,
The second composite image of the third image and the fourth image is created based on the position coordinate of the third image and the position coordinate of the fourth image. The blood vessel imaging device described.