Patent Description:
Patent Literature <NUM> discloses an individual authentication method using an iris image. In such an individual authentication method, a mask region is set under an upper eyelid, an image of an iris region excluding the mask region is used for authentication, and thereby eyelashes less affect the authentication accuracy.

Non Patent Literature <NUM> (NPL <NUM>) discloses a fake iris detection system in the framework of iris recognition, where iris normalization is performed on the input eye image and a ROI excluding a portion of the iris next to the outer circumference of the iris is used for classifying the image as a real or fake iris.

Non Patent Literature <NUM> (NPL <NUM>)discloses an iris authentication method where it is detected whether or not an iris is classified as being fake, where a fake iris is an iris wearing a patterned (i.e. colored) contact lens, wherein the detection is performed by applying a Daubechies wavelet filter on only <NUM> out of <NUM> tracks of the iris region adjacent to the pupil boundary.

In recent years, colored contact lenses in which a colored region is provided to a part of the contact lens have been commercially available. A colored contact lens on an eye provides a decorative effect that changes the color of an iris or makes an iris appear larger, and thus colored contact lenses have spread through the market.

In recognition of an iris as disclosed in Patent Literature <NUM>, when the recognition subject wears colored contact lenses, appearance of a part of an iris changes, and this may reduce the matching accuracy of the iris.

The present invention has been made in view of the above problem and intends to provide an iris recognition system, an iris recognition method, and a computer program that can reduce influence on matching accuracy when a recognition subject wears colored contact lenses.

According to the present invention, an iris recognition system, an iris recognition method, and a computer program that can reduce influence on matching accuracy when a recognition subject wears colored contact lenses can be provided.

Example embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same elements or corresponding elements are labeled with the same reference numerals, and the description thereof may be omitted or simplified.

<FIG> is a block diagram illustrating a hardware configuration example of an iris recognition system <NUM> that performs matching of an iris according to a first example embodiment of the present invention. The iris recognition system <NUM> may be a computer or an information communication terminal such as a mobile phone, a smartphone, a tablet personal computer (PC) , a laptop PC, a desktop PC, or the like, for example. The iris recognition system <NUM> has a function of iris matching that is a sort of biometric matching. The iris recognition system <NUM> performs iris matching by capturing an image of an iris of a user that is a recognition subject and matching it against a registered iris image. The pattern of an iris that adjust an aperture of a pupil is unique and permanent. Thus, identity verification is possible by matching the iris pattern acquired at matching against an iris image that has been registered in advance. In the following description, it is assumed that the iris recognition system <NUM> is mounted on a smartphone as an example and iris matching is performed for identity verification in a situation of user login, however, the iris recognition system <NUM> is not limited thereto.

The iris recognition system <NUM> has a central processing unit (CPU) <NUM>, a random access memory (RAM) <NUM>, a read only memory (ROM) <NUM>, and a flash memory <NUM> in order to implement a function as a computer performing calculation and storage. Further, the iris recognition system <NUM> has a communication interface (I/F) <NUM>, a display device <NUM>, an input device <NUM>, a visible light irradiation device <NUM>, a visible light camera <NUM>, an infrared irradiation device <NUM>, and an infrared camera <NUM>. The CPU <NUM>, the RAM <NUM>, the ROM <NUM>, the flash memory <NUM>, the communication I/F <NUM>, the display device <NUM>, the input device <NUM>, the visible light irradiation device <NUM>, the visible light camera <NUM>, the infrared irradiation device <NUM>, and the infrared camera <NUM> are connected to each other via a bus <NUM>. Note that the display device <NUM>, the input device <NUM>, the visible light irradiation device <NUM>, the visible light camera <NUM>, the infrared irradiation device <NUM>, and the infrared camera <NUM> may be connected to the bus <NUM> via a drive device (not illustrated) used for driving these devices.

While these components forming the iris recognition system <NUM> are illustrated as an integrated device in <FIG>, some of these functions may be formed by an externally attached device. For example, the visible light irradiation device <NUM>, the visible light camera <NUM>, the infrared irradiation device <NUM>, or the infrared camera <NUM> may be an externally attached device which is different from a part forming the function of the computer including the CPU <NUM> and the like.

The CPU <NUM> has a function of performing a predetermined operation according to a program stored in the ROM <NUM>, the flash memory <NUM>, or the like and controlling respective components of the iris recognition system <NUM>. The RAM <NUM> is formed of a volatile storage medium and provides a temporary memory area required for the operation of the CPU <NUM>. The ROM <NUM> is formed of a non-volatile storage medium and stores necessary information such as a program used for the operation of the iris recognition system <NUM>. The flash memory <NUM> is a storage device that is formed of a non-volatile storage medium and stores an image captured by the infrared camera <NUM> or the like, an image of a recognition subject, feature amount data, or the like.

The communication I/F <NUM> is a communication interface in accordance with a standard such as Wi-Fi (registered trademark), <NUM>, or the like and also is a module for communicating with other devices. The display device <NUM> is a liquid crystal display, an organic light emitting diode (OLED) display, or the like and used for displaying a moving image, a static image, a text, or the like. The input device <NUM> is a button, a touch panel, or the like and is used for user operation of the iris recognition system <NUM>. The display device <NUM> and the input device <NUM> may be integrally formed as a touchscreen.

The visible light irradiation device <NUM> and the visible light camera <NUM> are provided on a display surface or the like of the display device <NUM>, for example. The visible light irradiation device <NUM> is used as a light source used for capturing by the visible light camera <NUM>, for example. Further, in a part of the process, the visible light irradiation device <NUM> may be used as a visible light irradiation unit which performs a process of irradiating the user's eye with a visible light to induce a pupillary light reflex and thereby causing the pupil to contract. The visible light camera <NUM> can capture a landscape, a user's face, a user's eye, or the like by using a visible light to acquire an image. A digital camera with a Complementary Metal Oxide Semiconductor (CMOS) image sensor, a Charge Coupled Device (CCD) image sensor, or the like may be used for the visible light camera <NUM> so as to be suitable for image processing after capturing.

The infrared irradiation device <NUM> is a light emitting element such as an infrared LED that emits an infrared light. A digital camera with a CMOS image sensor, a CCD image sensor, or the like having a light receiving element configured to have a sensitivity to an infrared ray may be used for the infrared camera <NUM>. By irradiating the user's eye with an infrared light from the infrared irradiation device <NUM> and capturing an infrared ray reflected from an iris by using the infrared camera <NUM>, it is possible to capture an iris image used for iris matching. By acquiring an iris image by using an infrared ray, it is possible to obtain a high contrast image regardless of the color of the iris and reduce influence of reflection at a cornea. When such influence does not matter, however, the visible light camera <NUM> may be used to capture an iris image. In this case, the infrared irradiation device <NUM> and the infrared camera <NUM> may be omitted. Further, when the visible light camera is a camera capable of acquiring an image by using an infrared ray in addition to a visible light, the infrared camera <NUM> may be omitted. Note that the wavelength of the infrared ray emitted from the infrared irradiation device <NUM> may be a near infrared region around <NUM>, for example.

Note that the hardware configuration illustrated in <FIG> is an example, and other devices than the above may be added or some of the above devices may not be provided. Further, some of the above devices may be replaced with another device having the same function. Furthermore, some of the functions may be provided by another device via a network or may be implemented by the function forming the present example embodiment being distributed to a plurality of devices. For example, the flash memory <NUM> may be replaced with a hard disk drive (HDD) or may be replaced with cloud storage.

<FIG> is a function block diagram of the iris recognition system <NUM> according to the first example embodiment. The iris recognition system <NUM> has an image acquisition unit <NUM>, a pupil detection unit <NUM>, an iris detection unit <NUM>, a determination object image extraction unit <NUM>, a size change unit <NUM>, an evaluation value calculation unit <NUM>, a determination unit <NUM>, a processing unit <NUM>, a display unit <NUM>, an extraction range setting unit <NUM>, a feature amount calculation unit <NUM>, a matching unit <NUM>, and a storage unit <NUM>.

The CPU <NUM> implements the function of the image acquisition unit <NUM> that acquires an infrared image of a user's eye by controlling the infrared irradiation device <NUM> and the infrared camera <NUM>. The CPU <NUM> implements the function of the pupil detection unit <NUM>, the iris detection unit <NUM>, the determination object image extraction unit <NUM>, the size change unit <NUM>, the evaluation value calculation unit <NUM>, the determination unit <NUM>, the processing unit <NUM>, the extraction range setting unit <NUM>, the feature amount calculation unit <NUM>, and the matching unit <NUM> by loading a program stored in the ROM <NUM> or the like to the RAM <NUM> and executing it. The process performed by each of these units will be described later. The display unit <NUM> displays the acquired image, a message to the user, or the like. The CPU <NUM> implements the function of the display unit <NUM> by controlling the display device <NUM>. The storage unit <NUM> stores data of an iris image acquired by the image acquisition unit <NUM>, iris images registered in advance, feature amounts calculated from these iris images, or the like. The CPU <NUM> implements the function of the storage unit <NUM> by controlling the flash memory <NUM>.

<FIG> is a flowchart illustrating summary of the process performed by the iris recognition system <NUM> according to the first example embodiment. In step S100, based on the image including the user's eye, the iris recognition system <NUM> determines whether or not the user' s eye wears a colored contact lens.

A colored contact lens is a contact lens in which a colored part is provided to a part of a lens. A colored contact lens may be referred to as a color contact lens, a circle contact lens, or a cosmetic contact lens. A colored contact lens worn on an eye can provide a decorative effect that changes the color of an iris or makes an iris appear larger. In many cases, a colored region of a colored contact lens is mainly provided to a portion corresponding to a part near the outer circumference of the iris, and a portion corresponding to the pupil is colorless. This is for not losing a field of view while obtaining a decorative effect that makes an iris appear larger.

When a user wears a colored contact lens, a change in the pattern or the like of an iris may affect the accuracy of iris matching. Usually, registration of an iris image is performed without a colored contact lens being worn. This is because, when matching is performed with a colored contact lens being worn, the pattern of the iris at registration and the pattern of the iris at the matching are not matched. Thus, in step <NUM>, prior to the iris matching, determination as to whether or not a colored contact lens is worn is performed based on an image including the user' s eye. The content of the subsequent process can be made more suitable based on whether or not a colored contact lens is worn.

In step S200, the iris recognition system <NUM> performs a process for improving matching accuracy. This process is performed for reducing deterioration in accuracy of iris matching due to the colored contact lens if it is determined that a colored contact lens is worn mainly in step S100.

In step S300, the iris recognition system <NUM> matches an image including the user' s iris captured at the matching against an image including a user's iris registered in advance. In the matching process in this step, the content of the process can be changed in accordance with the result of determination in step S100 as to whether or not a colored contact lens is worn. If a colored contact lens is worn, the iris recognition system <NUM> performs matching of the iris by using a feature amount extracted from a region which excludes a predetermined range including the outer circumference of the iris out of the region of the iris included in the image.

It is not essential to perform all the processes from step S100 to step S300 illustrated in <FIG>, and an example embodiment in which a part of the above processes is omitted is included in the scope of the present invention. For example, the matching accuracy improvement process of step S200 may be omitted to simplify the process. Further, the process of step S100 may be omitted to simplify the process by determining in advance whether or not a colored contact lens is worn by using another device or instructing the user to input whether or not wearing a colored contact lens. Further, an image processing system that alone performs a process of determining whether or not a colored contact lens is worn in step S100 is also included in the scope of the present invention. Further, the process from step S100 to step S300 may be performed in cooperation of a plurality of devices.

With reference to <FIG>, a specific example of a colored contact lens-wearing determination process in step S100 of <FIG> will be described. <FIG> is a flowchart illustrating a colored contact lens-wearing determination process according to the first example embodiment. The process of <FIG> is to more specifically represent the process in step S100 of <FIG>.

In step S101, the image acquisition unit <NUM> acquires an image including the user's eye. The acquired image is stored in the storage unit <NUM>. Typically, because this image is acquired by an infrared ray, it is an image in grayscale. Further, the size of an image is <NUM> pixels in the horizontal direction by <NUM> pixels in the vertical direction, for example. However, since the size may be changed by a process described later, other sizes may be employed. Note that, in the present specification, terms expressing size such as the size of an image, the length of a subject, or the like may be defined in a standardized non-dimensional amount such as the number of pixels and are not limited to those defined in a unit having the length dimension such as mile-meter. Further, the image including the user' s eye is not limited to that acquired by using an infrared ray and may be acquired by using a visible light.

In step S102, the pupil detection unit <NUM> detects a pupil from an image including the eye acquired in step S101 and determines the position of the pupil. The determined position of the pupil is stored in the storage unit <NUM>. The shape of the pupil can be approximated as a circle. Thus, the position of the pupil can be expressed by the center coordinates and the radius of the pupil, for example. Note that the region of the pupil can be detected by extracting pixels having lower brightness than a predetermined value, for example.

In step S103, the iris detection unit <NUM> detects an iris from the image including the eye acquired in step S101 and determines the position of the iris. The position of the determined iris is stored in the storage unit <NUM>. The pupil detection unit <NUM> and the iris detection unit <NUM> may be more generally referred to as a detection unit. The shape of an iris can be approximated as an annular shape including the pupil, and thus the position of the iris can be expressed by the center coordinates, the outer circumference radius, and the inner circumference radius of the iris, for example. Since the inner circumference radius of an iris corresponds to the radius of the pupil, it can be omitted from the information indicating the position of the iris. Note that it is possible to detect an iris by extracting a change in brightness at a boundary between the outer circumference of the iris and a sclera (so called white of eye), for example. The iris detected here includes not only the user' s iris itself but also a pattern that is provided on a colored contact lens and represents an iris. Thus, in the present specification, the entire region appearing as an iris that includes an iris and a pattern provided on a colored contact lens may be referred to as an iris. Note that the order of step S102 and step S103 may be opposite. Alternatively, step S102 and step S103 may be performed in parallel or may be performed as a single process.

In step S104, the determination object image extraction unit <NUM> extracts two determination object images including side parts of an iris from an image including the eye acquired in step S101. The side parts of an iris here refer to portions on the outer circumference of the iris that are on the boundary to the white of eye, which are mainly the left and right parts excluding the upper and lower parts hidden behind the eyelids. The extracted determination object images are stored in the storage unit <NUM>. These two determination object images are used for the colored contact lens-wearing determination. Extraction of determination images will be described in detail with reference to <FIG>.

<FIG> is a diagram schematically illustrating extraction of determination object images according to the present example embodiment. <FIG> schematically illustrates an eye <NUM>, a pupil <NUM>, and an iris <NUM> included in the image acquired in step S101. The determination object image extraction unit <NUM> extracts two determination object images R1 and R2 from the image of the eye <NUM>. Note that the determination object image extraction unit <NUM> may be simply referred to as an extraction unit.

As illustrated in <FIG>, the determination object images R1 and R2 are extracted so as to include the left side part and the right side part of the iris <NUM>, respectively. Each of the determination object images R1 and R2 is a square whose side has a length of S (pixel). Further, one side in the vertical direction with respect to the eye <NUM> of the sides of the squares is a line segment passing through the center of the iris <NUM>. When the outer circumference radius of an iris is Ir1 (pixel), the length S of one side is set to meet S = Ir1 + m. Here, the value m is a predetermined value set so that the determination object images R1 and R2 include the side parts of an iris and include neither the upper end nor the lower end of the iris <NUM> and is set to <NUM> pixels, for example.

The reason why the positions of the determination object images R1 and R2 are set in such a way will be described. A pattern of a colored contact lens often has a notable feature near the outer circumference of an iris. For example, an eye wearing a colored contact lens often has a large change in brightness between the part of the iris and the part of white of eye. Thus, inclusion of the outer circumference of an iris in the determination object images R1 and R2 for determination improves the accuracy in detecting a colored contact lens by using a determination device. Further, the upper and lower parts of an iris may be hidden behind eyelids and eyelashes. When an eyelid or an eyelash is included in the determination object images R1 and R2, the determination accuracy may deteriorate. It is therefore desirable to set the positions of the determination object images R1 and R2 so as to include the side parts of an iris and include neither the upper end nor the lower end of the iris. Further, it is desirable that one of the sides in the vertical direction of each of the squares be a line segment passing through the center of the iris <NUM> because wide determination object images R1 and R2 can be ensured.

Note that it is not essential that each of the determination object images R1 and R2 is a square. For example, each of the determination object images R1 and R2 may be a rectangle. That is, each shape of the determination object images R1 and R2 may be any shape that is not limited to a square or a rectangle and may be a polygon, a sector, or a figure including a curve as an example of other shapes. When the determination object images R1 and R2 have shapes other than a square, it is desirable that the length in the horizontal direction of each of the determination object images R1 and R2 with respect to the eye <NUM> be longer than the outer circumference radius of the iris <NUM> so as to include the side parts of the iris and include the iris as widely as possible.

While the determination object images R1 and R2 are acquired from the left and right parts of the iris <NUM>, any one of them may be acquired. However, it is desirable to use the two determination object images R1 and R2 because this enables more accurate determination.

In step S105, the size change unit <NUM> changes the size of the determination object images R1 and R2. <FIG> is a diagram schematically illustrating a size change of the determination object image according to the first example embodiment. As illustrated in <FIG>, the size change unit <NUM> reduces the determination object images R1 and R2 having a length of the side of S pixels to determination object images R1a and R2a having a length of the side of <NUM> pixels and thereby generates the determination object images R1a and R2a. The reason for changing the size is to set images to have a certain number of pixels so as to be suitable for the subsequent determination process and thereby make a process performed by a determination device described later more efficient. The determination object images R1a and R2a after the size change are stored in the storage unit <NUM>. The length of one side being <NUM> pixels is an example, and the invention is not limited thereto in particular. Further, when it is not essential to limit the size in the process performed by a determination device, the process of step S105 may be omitted.

<FIG> is a diagram schematically illustrating the determination process in step S106 to step S109. The subsequent process will be described with cross reference to <FIG> and <FIG>. The evaluation value calculation unit <NUM> that performs this process includes a determination device formed of a convolution neural network (CNN), for example. Many images including images of an eye wearing a colored contact lens and images of an eye not wearing a colored contact lens are automatically learned in advance as teacher data in the determination device, and thereby the determination device is configured to be able to determine whether or not a colored contact lens is worn. Once an image including an eye is input to the determination device, it outputs an evaluation value indicating a likelihood of a colored contact lens being worn. An evaluation value takes continuous values from <NUM> to <NUM> as an example. In this case, a higher likelihood of no colored contact lens being worn results in an evaluation value closer to <NUM>, and a higher likelihood of a colored contact lens being worn results in an evaluation value closer to <NUM>.

In step S106, a determination device of the evaluation value calculation unit <NUM> calculates two evaluation values V1 and V2 based on the two determination object images R1a and R2a, respectively. The evaluation value is stored in the storage unit <NUM>.

From step S107 to step S109, the determination unit <NUM> determines whether or not a colored contact lens is worn based on the two evaluation values V1 and V2. More specifically, in step S107, the determination unit <NUM> determines whether or not both the evaluation value V1 and the evaluation value V2 are greater than or equal to <NUM>. If both the evaluation value V1 and the evaluation value V2 are greater than or equal to <NUM> (step S107, YES), the determination unit <NUM> determines that a colored contact lens is worn (step S108). If at least one of the evaluation value V1 and the evaluation value V2 is less than <NUM> (step S107, NO), the determination unit <NUM> determines that no colored contact lens is worn (step S109).

As discussed above, in the determination process from step S106 to step S109, only when both the determination results from the two determination object images R1a and R2a indicate that a colored contact lens is worn, it is determined that a colored contact lens is worn. There are various types of colored contact lenses, and there is an individual difference in the pattern of the iris or the like. Thus, even when a sufficient amount of teacher data is used to perform learning, the determination device may make erroneous determination. Accordingly, in order to improve determination accuracy, it is desirable to input both the two determination object images R1a and R2a as described above and aggregate determination results from them to make determination.

An example of a process when the determination process from step S106 to step S109 is performed by using a single determination object image will be described. The determination device of the evaluation value calculation unit <NUM> calculates a single evaluation value from the single determination object image. Then, the determination unit <NUM> determines that a colored contact lens is worn if the evaluation value is greater than or equal to <NUM> and determines that no colored contact lens is worn if the evaluation value is less than <NUM>, which enables determination as to whether or not a colored contact lens is worn. In this way, the number of determination object images may be one.

As discussed above, according to the colored contact lens-wearing determination process of the present example embodiment, by performing the determination based on a determination object image including the side part of the outer circumference of an iris, it is possible to accurately determine whether or not a colored contact lens is worn.

Note that, while the determination device with a convolution neural network is used in the determination process illustrated in <FIG>, without being limited thereto, determination as to whether or not a colored contact lens is worn may be performed based on a change in brightness at the boundary between the outer circumference of the iris and the white of eye, for example.

Further, the determination in step S107 may be a process of determining that a colored contact lens is worn if at least one of the evaluation value V1 and the evaluation value V2 is greater than or equal to <NUM> and determining that no colored contact lens is worn if both of the evaluation value V1 and the evaluation value V2 are less than <NUM>. Further, the determination in step S107 may be a process of selecting one or more evaluation values to be used in the determination out of a plurality of evaluation values such as the evaluation value V1, the evaluation value V2, and the like in accordance with the reliability or the like of the determination object image. For example, when insufficiently reliable one is included in a plurality of determination object images due to noise, it is possible to improve the determination accuracy by excluding an evaluation value of such a determination object image from the determination process. Note that, in the example described above, the threshold of <NUM> used for determination of the evaluation value V1 and the evaluation value V2 is a mere example and may be set to any value other than <NUM>.

Next, a specific example of the matching accuracy improvement process in step S200 of <FIG> will be described with reference to <FIG>.

<FIG> is a flowchart illustrating a first example of the matching accuracy improvement process according to the first example embodiment. In step S201, the processing unit <NUM> refers to the determination result of step S100. If it is determined that the user wears a colored contact lens (step S201, YES), the process transfers to step S202. If it is determined that the user does not wear a colored contact lens (step S201, NO), the process ends.

In step S202, the processing unit <NUM> controls the visible light irradiation device <NUM> to irradiate the user' eye with a visible light. Then, in step S203, the processing unit <NUM> causes the image acquisition unit <NUM> to again acquire an image including the eye.

When a retina of the eye is irradiated with a visible light, a pupillary light reflex occurs that causes a pupil to contract. This results in a wider iris region and a wider area in which the pattern of the iris can be acquired. Therefore, deterioration in accuracy of iris matching due to a colored contact lens can be reduced. Further, in the present example, since an unconscious reflex is utilized, the recognition subject is not required to take any action. For example, the present example can be applied to a case where it is difficult to make the recognition subject to take some action, such as when the recognition subject is not cooperative in iris matching or when the recognition subject does not understand the language, such as in a situation of identity verification in a government office.

Even when either one of the eyes is irradiated with a visible light, contraction of the pupil due to a pupillary light reflex occurs in both the eyes. Thus, the eye irradiated with a visible light and the eye used for again acquiring an image may be different. This can suppress the influence of a reflex caused by the irradiated visible light.

<FIG> is a flowchart illustrating a second example of the matching accuracy improvement process according to the first example embodiment. The description of the same process as that in <FIG> will be omitted as appropriate. In step S204, the processing unit <NUM> causes the display unit <NUM> to display a message that prompts the user to look at a bright object. An example of a specific message may be "To authenticate once more, please look at something bright and then look at camera again. " After the user looks at a bright object in response to this message, in step S203, the processing unit <NUM> causes the image acquisition unit <NUM> to again acquire an image including the eye.

Also in the present example, because the user looks at a bright object, a pupillary light reflex causes the pupil to contract and the region of the iris to be wider. It is therefore possible to reduce deterioration in accuracy of iris matching due to a colored contact lens. In the present example, unlike the first example described above, it is possible to perform the matching accuracy improvement process utilizing a pupillary light reflex even when the visible light irradiation device <NUM> is not provided. Note that the message may have a content that specifically indicates a thing to look at such as "To authenticate once more, please once look at lighting and then look at camera again.

An example in which the matching accuracy is significantly improved in the configuration utilizing contraction of the pupil in <FIG> and <FIG> will be described. If it is determined that a colored contact lens is worn in step S100, a process of excluding a part near the outer circumference of the iris from the extraction range of the feature amount may be performed in the iris matching in step S300. At this time, there may be a problem of decrease in the region contributing to extraction of a feature amount and thus a reduction in the accuracy of iris matching. In such a situation, by performing the process of <FIG> and <FIG> to cause the pupil to contract, it is possible to increase not the area near the outer circumference of the iris but the opposite side, namely, the area of the inner circumference side of the iris. This enables accurate iris matching even when a part near the outer circumference of the iris is excluded from the extraction range of a feature amount.

<FIG> is a flowchart illustrating a third example of the matching accuracy improvement process according to the first example embodiment. The description of same process as that in <FIG> will be omitted as appropriate. In step S205, the processing unit <NUM> causes the display unit <NUM> to display a message that prompts the user to blink. A specific example of the message may be "To authenticate once more, please blink and then look at camera again. " After the user blinks in response to this message, in step S206, the processing unit <NUM> causes the image acquisition unit <NUM> to additionally acquire an image including the eye.

In the present example, the user is caused to blink and thereby the colored contact lens rotates, and the position of the pattern of the colored contact lens changes before and after the blinking. On the other hand, the pattern of the iris itself of the user's eye does not change by a blinking. Therefore, by calculating a difference between two images acquired before and after a blinking, it is possible to separate the pattern of the colored contact lens from the pattern of the iris of the user' s eye and thus perform accurate matching by extracting the pattern of the iris of the user's eye. It is therefore possible to reduce deterioration in accuracy of iris matching due to a colored contact lens.

Also in the present example, the accuracy improvement process can be performed. In the present example, since a pupillary light reflex caused by a change in brightness is not utilized, there is an advantage of the effect being not lost even in a bright place.

Note that the process in the flowchart of <FIG> may be modified into a process of repeating the process of step S206 for multiple times to acquire images for multiple times. Furthermore, in this case, the process of step S205 may be omitted. Since a human blinks unconsciously, such an unconscious blinking may cause rotation of the colored contact lens even without display of a message that prompts the user to blink. Therefore, even without displaying a message, repeated acquisition of images may enable acquisition of images used for separating the pattern of the colored contact lens and the pattern of the iris of the user's eye from each other, and in this case, the same effect and advantage as that described above can be obtained.

<FIG> is a flowchart illustrating a modified example of the third example of the matching accuracy improvement process according to the first example embodiment. As illustrated in step S207 of <FIG>, the content of the message may be to prompt the user to move the eye such as an instruction of looking right and left. A specific example of the message may be "To authenticate once more, please look right and left and then look at camera again. " Since motion of the eyeball causes rotation of the colored contact lens, the same effect and advantage as that of the case of prompting a blinking as described above can be obtained also in the present modified example.

As discussed above, according to the matching accuracy improvement process of the present example embodiment, it is possible to reduce deterioration in accuracy of iris matching due to a colored contact lens being worn.

Note that, while the user is notified of various messages by display on the display unit <NUM> in the processes described above, a method of notification of the message is not limited thereto. For example, voice may be used for notification of the message.

A specific example of the iris matching process in step S300 of <FIG> will be described with reference to <FIG> is a flowchart illustrating the iris matching process according to the first example embodiment. The process of <FIG> is more specific version of the process of step S300 of <FIG>.

In step S301, the extraction range setting unit <NUM> refers to the determination result of step S100. If it is determined that the user wears a colored contact lens (step S301, YES), the process transfers to step S302. If it is determined that the user does not wear a colored contact lens (step S301, NO), the process transfers to step S303.

In step S302, the extraction range setting unit <NUM> excludes a part near the outer circumference of the iris to set an extraction range of a feature amount. <FIG> is a diagram schematically illustrating a setting of the extraction range of the feature amount according to the first example embodiment. As illustrated in <FIG>, the region of the iris in an image is divided into a mask region <NUM> and a feature amount extraction region <NUM>. The mask region <NUM> is a region defined in accordance with a position of the outer circumference and the inner circumference of the iris, which is, out of the region of the iris, a range from which no feature amount used for the subsequent matching process is extracted. The feature amount extraction region <NUM> is, out of the region of the iris, a region from which a feature amount is extracted and which is a range except the mask region <NUM>. The mask region <NUM> is arranged near the outer circumference of the iris. That is, the feature amount extraction region <NUM> is a range excluding a predetermined range including the outer circumference of the iris.

The range of the mask region <NUM> is defined as a ring including the outer circumference end of the iris and having a width of <NUM> percent or more from the outer circumference to the inner circumference of the iris. More specifically, the mask region <NUM> is a ring having an outer circumference radius is Ir1 and an inner circumference radius is {Ir2 + <NUM> × (Ir1 - Ir2)}, where the outer circumference radius of the iris is Ir1 and the inner circumference radius of the iris is Ir2.

The reason for defining the mask region <NUM> and the feature amount extraction region <NUM> will be described. In a colored contact lens, many colored portions (pattern) are arranged in a portion corresponding to a part near the outer circumference of an iris. Thus, when a feature amount is extracted from a region including a part near the outer circumference of the iris to perform iris authentication with a colored contact lens being worn, iris matching is performed with the pattern of the colored contact lens overlapping with the pattern of the iris, and therefore this causes a problem of a reduction in matching accuracy. For example, the same person may be determined as another person because the pattern of the iris not wearing a colored contact lens taken at registration does not match the pattern taken at the matching with the pattern of the colored contact lens overlapping with the pattern of the iris.

By defining the feature amount extraction region <NUM> as a range excluding a predetermined range including the outer circumference of the iris, a part near the outer circumference of the iris in which many patterns of the colored contact lens are arranged is excluded from the extraction of a feature amount. On the other hand, no pattern may be arranged in a region of the colored contact lens corresponding to a part near the inner circumference of the iris in many cases in order to ensure a field of view, which less affects iris matching. It is thus possible to reduce deterioration in accuracy of iris matching due to a colored contact lens being worn.

In step S303 when the user does not wear a colored contact lens, the mask region <NUM> is not provided, and the feature amount extraction region <NUM> is set for the entire iris. When no colored contact lens is worn, it is not necessary to exclude a part near the outer circumference from the feature amount extraction region, rather, no exclusion of a part near the outer circumference allows for a wider feature amount extraction region and thus enables higher matching accuracy. It is therefore desirable to perform different process depending on whether or not a colored contact lens is worn.

In step S304, the feature amount calculation unit <NUM> uses the patterns of the iris included in an image of the set feature amount extraction region <NUM> or the like to calculate a feature amount. The calculated feature amount is stored in the storage unit <NUM>.

In step S305, the matching unit <NUM> matches the feature amount acquired in step S304 against a feature amount of an iris of a user registered in advance in the storage unit <NUM>. When it is determined as the iris of the same person by matching, the iris recognition system <NUM> determines that the identity verification is completed and performs a process of login or the like.

As discussed above, according to the iris matching process of the present example embodiment, by defining a range excluding a predetermined range including the outer circumference of the iris as an extraction range of a feature amount, it is possible to reduce influence on matching accuracy when the recognition subject wears a colored contact lens.

When excluding a part near the outer circumference of the iris to set the feature amount extraction region <NUM> by using the scheme of step S302, it is more effective to combine any of the matching accuracy improvement processes illustrated by using <FIG> and <FIG>. In the scheme of step S302, the feature amount extraction region <NUM> is reduced by the area of the mask region <NUM>. Using the process of <FIG> or <FIG> together, it is possible to increase the range of the iris and therefore compensate the influence of the reduced feature amount extraction region <NUM>.

In the process described above, since the mask region <NUM> is determined independently of the pattern of a colored contact lens, there is no need to perform a process of detecting the pattern of the colored contact lens, which enables a high speed process. When the accuracy is more important than the processing speed, however, a process of determining a colored portion of a colored contact lens by determining the pattern of the colored contact lens and the pattern of an iris itself of the user may be added. In this case, the colored portion of the colored contact lens is set as the mask region <NUM>. In such a way, when the colored portion of a colored contact lens (the shape of the pattern or the region where the pattern is arranged) can be determined, the mask region <NUM> that is a region near the outer circumference of the iris when iris matching is performed can be set based on the colored portion of the colored contact lens.

As an example of the process of determining the pattern of a colored contact lens and the pattern of an iris itself of the user, there may be a scheme of searching for the contour of the pattern of the colored contact lens by using an adaptive contour model such as a snakes method or a Level Set method. Further, as another example, there may be a scheme of dividing an iris into a plurality of rectangular regions and using a convolutional neural network for each rectangular region to determine whether or not there is a pattern of a colored contact lens, a scheme of detecting whether or not there are regular figures on a concentric circle, a scheme of detecting whether or not there are radial straight lines, or the like.

The device described in the above example embodiment can be also configured as a second example embodiment to a fourth example embodiment illustrated below.

<FIG> is a function block diagram of an iris recognition system <NUM> according to the second example embodiment. The iris recognition system <NUM> has a determination unit <NUM> and a matching unit <NUM>. The determination unit <NUM> determines whether or not a colored contact lens is worn based on an image including an eye of a recognition subject. The matching unit <NUM> performs matching of the iris by using a feature amount extracted from a region excluding a predetermined range including the outer circumference of the iris out of the region of the iris included in the image when it is determined by the determination unit <NUM> that a colored contact lens is worn.

According to the present example embodiment, the iris recognition system <NUM> that can reduce influence on the matching accuracy when the recognition subject wears a colored contact lens can be provided.

<FIG> is a function block diagram of an image processing system <NUM> according to the third example embodiment. The image processing system <NUM> has an extraction unit <NUM> and the determination unit <NUM>. The extraction unit <NUM> extracts a determination object image including a side part of the outer circumference of an iris from an image including an eye. The determination unit <NUM> determine whether or not a colored contact lens is worn based on the determination object image.

According to the present example embodiment, the image processing system <NUM> that can accurately determine whether or not a colored contact lens is worn can be provided.

<FIG> is a function block diagram of an iris recognition system <NUM> according to the fourth example embodiment. The iris recognition system <NUM> has a determination unit <NUM> and the processing unit <NUM>. The determination unit <NUM> determines whether or not a colored contact lens is worn based on an image including an eye of a recognition subject. The processing unit <NUM> performs a process of improving accuracy of iris matching on the recognition subject when it is determined by the determination unit <NUM> that a colored contact lens is worn.

According to the present example embodiment, the iris recognition system <NUM> that can reduce deterioration in accuracy of iris matching due to a colored contact lens being worn can be provided.

The iris recognition systems of the example embodiments described above may be used not only for authentication at login illustrated as an example but also for various identity verification. For example, the iris recognition systems of the example embodiments described above may be applied to identity verification for immigration at an airport, a seaport, or a national border, identity verification at a government office, identity verification for access to a factory or an office, identity verification at entrance to an event hall, or the like.

In each example embodiment described above, acquisition of an image used for iris matching may be performed on one eye or may be performed on both eyes of an authentication subject. Acquisition of an image of only one eye has the advantage of improvement of the processing speed or reduction in the storage capacity, and acquisition of images of both eyes has the advantage of improvement of authentication accuracy.

In each example embodiment described above, a situation where a feature amount of an acquired image of an iris is matched against a feature amount of an iris which has been registered in advance, that is, a process of iris matching has been described as an example. However, each example embodiment described above can be applied to a situation of registration of an image of an iris or a feature amount of an iris with appropriate modification. Specifically, with the iris matching process of step S300 being replaced with the iris registration process, modification can be made for the situation of registration. In this case, the iris registration process may be a process of acquiring an image of an iris, calculating a feature amount, and storing the feature amount of the iris, for example.

While the process of step S202, S204, or S205 is performed when it is determined that the user wears a colored contact lens in the process of step S201 in each example embodiment described above, this process may be other process than is illustrated. For example, it may be a process that, when it is determined that the user wears a colored contact lens, displays a message instructing the user to put off the colored contact lens. Alternatively, when it is determined that the user wears a colored contact lens, a failure of matching or registration may be determined. In this case, the process may notify the user of a failure of the process by a message, an alarm, or the like to prompt another matching or registration or may notify the user of a failure of the process to end the process. Note that these processes may be performed instead of the process of step S202, S204, or S205 or may be performed in parallel with the process of step S202, <NUM>, or S205.

As described above, the advantage of instructing the user to put off the colored contact lens or performing the process as matching or registration being failed will be described with an example of a situation of iris registration. Since the importance of identity verification is high in a situation of iris registration, it is necessary to enhance reliability of a registered iris being the person in question. In particular, this requirement for reliability is more significant in a situation of important authentication such as immigration control or national identification (ID). Registration with a colored contact lens being worn will impair the function of identity verification. Thus, when registration is attempted with a colored contact lens being worn, the reliability of identity verification can be maintained by issuing some alert and disabling registration. This improves the accuracy of an iris recognition system. Further, multiple registration using a colored contact lens may be prevented.

The scope of each example embodiment also includes a processing method of storing, in a storage medium, a program that causes the configuration of the example embodiment to operate to implement the function of the example embodiment described above, reading out as a code the program stored in the storage medium, and executing the code in a computer. That is, a computer readable storage medium is included in the scope of each example embodiment. Further, not only the storage medium in which the program described above is stored but also the program itself is included in each example embodiment. Further, one or more components included in the example embodiments described above may be a circuit such as an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), or the like configured to implement the function of each component.

As the storage medium, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a Compact Disk (CD)-ROM, a magnetic tape, a non-volatile memory card, or a ROM, for example, may be used. The scope of each example embodiment includes not only those executing a process with a program itself stored in the storage medium but also those operating on an operating system (OS) in cooperation with the function of another software or an extension board to execute the process.

Services realized by the function of each example embodiment described above can be provided to the user in a form of Software as a Service (SaaS).

Note that all the example embodiments described above are mere examples of embodiment in implementing the present invention, and the technical scope of the present invention should not be limited to these example embodiments. That is, the present invention can be implemented in various forms without departing from the technical concept thereof or the primary feature thereof.

Claim 1:
An iris recognition system comprising:
a determination means for, based on an image including an eye of a recognition subject, determining whether or not a colored contact lens is worn; and
a matching means for, when it is determined by the determination means that the colored contact lens is worn, performing matching a feature amount of an iris of the recognition subject extracted from a region of the iris excluding a predetermined range including an outer circumference of the iris out of the region of the iris included in the image against a feature amount of an iris of a previously registered person, for authenticating the recognition subject,
wherein the predetermined range is a ring including the outer circumference end of the iris and having a width of <NUM> percent or more from the outer circumference to an inner circumference of the iris.