Patent Publication Number: US-2010128937-A1

Title: Multi-image acquisition apparatus

Description:
CROSS-REFERENCE(S) TO RELATED APPLICATION 
     The present invention claims priority of Korean Patent Application No. 10-2008-0116625, filed on Nov. 24, 2008, which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to an image acquisition apparatus for a multi-modal biometrics system, and, in particular, to the image acquisition apparatus for acquiring facial and iris images for use in a multi-modal biometrics system. 
     BACKGROUND OF THE INVENTION 
     Currently, the field of biometrics is diverging into multi-modal biometrics, long distance biometrics, and user-friendly image acquisition technologies. In particular, the fields of facial and iris recognition are evolving into a multi-modal facial and iris biometric technique because two pieces of biometric information can be acquired from a single facial image and fields of different biometrics can be complemented each other. In particular, an iris recognition technology shows best performance in biometrics. 
     However, a biometrics system has the disadvantage of a low utilization due to an inconvenient interfacing between a user and the system in iris image acquisition and limited compatibility with facial recognition. 
     In order to simultaneously acquire facial and iris images, a facial image acquisition apparatus and an iris image acquisition apparatus are separately required. The facial image acquisition apparatus and the iris image acquisition apparatus are provided with respective cameras, and adjust incident angles of their corresponding cameras arranged at upper and lower locations to capture facial and iris images, respectively. 
     Meanwhile, the technology using the facial image acquisition camera and the iris image acquisition camera may be susceptible to an error due to differences in incident angles and phases and in the photographing areas. 
     Furthermore, the conventional iris image acquisition camera uses a cold mirror positioned in front of a camera lens and imaging an incident image thereon to enable a user to directly check the location of the eye to be imaged from a short distance, e.g., about 40 cm. 
     However, although a cold mirror is useful to check an incident image over a short distance, appropriate training is requisite for the convenient use of the cold mirror. Accordingly, it is necessary to develop a user-friendly iris and facial image acquisition technique capable of simultaneously acquiring iris and facial images from a long distance with greater efficiency. 
     SUMMARY OF THE INVENTION 
     The present invention provides a multi-image acquisition apparatus capable of simultaneously acquiring facial and iris images from a relatively long distance while minimizing error attributable to a phase difference occurring when capturing facial and iris images along a same light path. 
     In accordance with an aspect of the present invention, there is provided a multi-image acquisition apparatus for use in a biometrics system including a light splitting filter for reflecting or transmitting multi-image lights representing an image of a target subject provided along an identical light path into different bands; a first image sensor for imaging an iris area by capturing a fraction of the multi-image light which has been transmitted through the light splitting filter; a second image sensor for imaging a facial area by capturing a fraction of the multi-image light which has been reflected from the light splitting filter; and a control module for controlling the first sensor and the second sensor and providing the images obtained by the first sensor and second sensor for image recognition. 
     According to the present invention, images of a facial region and an iris area can be simultaneously acquired using a single camera apparatus and an iris image can be acquired from a long distance (identical to the distance from which a facial image is captured) without requiring a cold mirror. Furthermore, the present invention allows an image of a subject to pass along the same one path of the camera apparatus, thereby minimizing the occurrence rate of error attributable to a phase difference which may occur when facial and iris images are captured using two existing facial recognition and iris recognition cameras. Furthermore, the present invention is configured such that a telescopic lens is added in front of the camera apparatus, so that facial track/recognition and iris recognition can be performed from a long distance and efforts to bring a user&#39;s eye to a location near a guidance area within the cold mirror of the camera apparatus to perform iris recognition can be reduced, with the result that it is expected that the usability of the facial and iris image acquisition/recognition system can be considerably increased. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic diagram showing the configuration of a multi-image acquisition apparatus capable of simultaneously acquiring facial and iris images from a single incident light; 
         FIG. 2  is a detailed block diagram showing the control module of the multi-image acquisition apparatus shown in  FIG. 1 ; 
         FIG. 3  is a diagram showing the connection between the multi-image acquisition apparatus and a multi-image recognition apparatus; 
         FIG. 4  is a block diagram showing an example of the internal construction of the multi-image recognition apparatus; 
         FIG. 5  is a diagram showing an example of facial and iris images acquired from a single input image using the multi-image acquisition apparatus; and 
         FIG. 6  is a flowchart showing an example of controlling the multi-image acquisition and recognition of the biometrics system according to the present embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, which form a part hereof. 
       FIG. 1  is a schematic diagram showing a configuration of a multi-image acquisition apparatus  10  for use in a multi-modal biometrics system for simultaneously acquiring both facial and iris images from a single incident light. The multi-image acquisition apparatus  10  includes a focusing lens  100 , an infrared illuminator array  102 , a light splitting filter  104 , an infrared filter  106 , a zoom lens group  108 , an iris image sensor  110 , a distance measurement sensor  112 , a UV filter  114 , an objective lens group  116 , a facial image sensor  120 , a control module  200 , and an external interface terminal  122 . 
     First, the focusing lens  100  is used to improve parallel light for incident light of a target subject for image acquisition along a single light path. In the drawing, the incident light includes infrared rays represented by a thin solid line, and visible rays represented by thick solid lines. In general, an image for facial recognition uses the visible ray band, while an image for iris recognition uses the infrared band. 
     The infrared illuminator array  102  is arranged in the front surface of the multi-image acquisition apparatus and used to capture an iris image along with the iris image camera  110 . The infrared illuminator array  102  emits infrared rays in a specific wavelength band ranging, e.g., from 750 nm to 850 nm. The infrared rays reach the target subject, and are then reflected to the multi-image acquisition apparatus  10  as multi-image light representing the target subject. Intensity of the infrared illuminator array  102  for iris image capture needs to be strengthened in proportion to a distance between the target subject and the multi-image acquisition apparatus. 
     The light splitting filter  104  is used for reflecting and transmitting the multi-image light to different bands. For example, a beam splitter or a dichroic mirror may be used as the light splitting filter  104 . For the application of the beam splitter, it is preferable to design the beam splitter to reflect the multi-image light in the entire visible ray band on the basis of a specific wavelength and to transmit infrared light over a specific band. For the application of the dichroic mirror, it is preferable to design the dichroic mirror to have an infrared filtering function. 
     The infrared filter  106  is provided for a case where a beam splitter is used as the light splitting filter  104 , and is requisite for the acquisition of a more desirable iris image in the iris image sensor  110  to which light in the infrared band is provided. Here, for the purpose of iris recognition from the light in the infrared band, the infrared filter  106  may include an infrared filter capable of passing infrared rays in a band ranging from 750 nm to 850 nm or a long pass infrared filter capable of passing infrared rays in a band above approximately 750 nm. 
     In order to recognize the iris, a diameter of an iris area needs to be wider than, e.g., 150 pixels and therefore, it is necessary to enlarge and capture an eye area in a facial region. The zoom lens group  108  is employed to guarantee such image quality of the enlarged and captured eye area, and the focusing control of the zoom lens group  108  under the control of the control module  200  allows to enlarge and capture an iris image. 
     The iris image sensor  110  serves to obtain an iris image from a fraction of the multi-image light. For example, a high-resolution image sensor, more preferably, a low-speed and high-resolution monochrome CCD/CMOS sensor may be used as the iris image sensor. 
     A lens with a low field of depth may be used to acquire the iris image. In this case, minute focusing adjustment using a distance measurement sensor  112  is required. 
     Meanwhile, the UV filter  114  may be provided to improve the facial image in a visible band reflected from the light splitting filter  104 . Further, the objective lens group  116  is provided to improve the facial image and acquire the facial image of a specific size. 
     The facial image sensor  120  is used for facial image acquisition from a fraction of the multi-image light. For example, a high-speed image sensor, more preferably, a high-speed and low-resolution CCD/CMOS sensor may be used as the facial image sensor  120 . 
     The control module  200  functions to control the zoom lens group  108 , the iris image sensor  110  and the facial image sensor  120  and provides facial and iris images acquired by the image sensor  110  and the facial image sensor  120  to an image recognition apparatus  300  (which will be described later) through the external interfacial terminal  122 . Additionally, the control module  200  enables power to be supplied to the multi-image acquisition apparatus  10  through the external interface terminal  122 . Further, In order to acquire an iris image through the enlargement of an iris area in a facial image, the control module  200  performs a synchronization process for the acquisition of an eye area from a facial region. 
     Hereinafter, the operation of the control module  200  is described in detail with reference to  FIG. 2 . 
       FIG. 2  is a detailed block diagram showing the control module  200  of the multi-image acquisition apparatus  10  shown in  FIG. 1 . The control module  200  includes an iris image sensor driving unit  20  for driving the iris image sensor  110  to acquire the iris image, a facial image sensor driving unit  22  for driving the facial image sensor  120  to acquire the facial image, a zoom lens group driving unit  24  for controlling a focusing operation of the zoom lens group  108 , a control unit  26  for controlling the overall operations of iris image sensor driving unit  20 , the facial image sensor driving unit  22  and the zoom lens group driving unit  24 , and an external interface unit  28  for connecting the external interface terminal  122  and the control unit  26  to each other. 
     Here, when a facial region enlargement command (to enlarge an eye part for the purpose of iris image acquisition) is received from the multi-image recognition apparatus  300  through the external interface terminal  122 , the control unit  26  controls the zoom lens group driving unit  24  so that the zoom lens group  108  is focused. Furthermore, when an iris image and/or facial image acquisition command is received from the image recognition apparatus  300  through the external interface terminal  122 , the control unit  26  controls the iris image sensor driving unit  20  and/or the facial image sensor driving unit  22  to acquire the iris and/or facial image and to provide the acquired iris and facial image to the image recognition apparatus  300  through the external interface terminal  122 . 
       FIG. 3  is an example of diagram showing a connection between the image acquisition device  1  and the multi-image recognition device  300  in a multi-modal biometrics system. 
     As can be seen from  FIG. 3 , an indicator  34  is attached to the front of the multi-image acquisition apparatus  10  and is used to accurately locate a facial image  30  in order to efficiently acquire facial and iris images. The indicator  34  may be implemented with a liquid crystal display (LCD), an organic light emitting diode (OLED) or the like. If necessary, the indicator  34  may be configured to issue voices. 
     For example, in case where an LCD is used as the indicator  34 , a reference screen  32  having an area of interest  36  may be employed so that a facial region of the facial image  30  to be located on the LCD has been located in the area of interest. 
     A degree of freedom for a facial image is flexible. However, in order to accurate capture an eye area, a facial region needs to be accurately located when a resolution of a camera module is low or it is necessary to enlarge the eye area at high magnification. 
     The multi-image acquisition apparatus  10  are connected to the image recognition apparatus  300 . The image recognition apparatus  300  functions to control the indicator  34  and the multi-image acquisition apparatus  10  and, also, to recognize or authenticate the iris and facial images acquired by the multi-image acquisition apparatus  10  by using an appropriate iris and facial recognition software. 
       FIG. 4  is a block diagram of the image recognition apparatus  300 . The image recognition apparatus  300  includes a component extraction unit  30  for extracting components of the iris and face of the subject in captured images provided by the multi-image acquisition apparatus, a facial and iris recognition unit  32  for recognizing the iris and face using the extracted components, and a user input unit  34  for applying a user input signal in conjunction with the iris and facial recognition software. 
       FIG. 5  is a diagram showing an example of facial and iris images acquired from a single input image using the image acquisition apparatus. 
     From a face to be imaged  50 , a facial region  52  may be imaged by the facial recognition camera  120  and a single eye region  54  or an eye region of two eyes  56  may be imaged by the iris image sensor  110  depending on resolution.  FIG. 6  is a flowchart showing a method of the multi-image acquisition and recognition by the multi-image acquisition apparatus and in accordance with the present embodiment. 
     First, a target subject to be imaged is provided to the iris image sensor  110  and the facial image sensor  120  where facial and iris regions are captured to acquire a facial image and an iris image, respectively at step S 600 . 
     The facial and iris images are then provided to the image recognition apparatus  300  through the external interface terminal  122 , and the components of the face and iris of the subject are extracted from the facial and iris images by the component extraction unit  30  at step S 602 . The extracted components of the face and iris of the subject are then provided to the facial and iris recognition unit  32 . 
     At this time, if the correction of the iris image has been requested by the user input unit  34  in the image recognition apparatus  300  at step S 604 , the image recognition apparatus  300  provides a corresponding correction request signal to the control unit  26  in the multi-image acquisition apparatus, and the control unit  26  controls the zoom lens group driving unit  24  so that it focuses the zoom lens group  108 , thereby enlarging and capturing an iris area  54  or  56 , at step S 606 . 
     Further, if the user input unit  34  of the image recognition apparatus  300  requests the correction of the facial image at step S 608 , the image recognition apparatus  300  provides a corresponding correction request signal to the indicator  34  attached to the front of the image acquisition apparatus, and the indicator  34  displays the captured facial image  52  to rearrange the face region at step S 610 . 
     Finally, at step S 612  the facial and iris recognition unit  32  recognizes the facial and iris images having separate and corrected results. 
     While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.