Patent Description:
In various fields, a method is adopted in which the identity of a user is proved by using an image acquired by capturing an image of an identity certificate of the user. As an example, when a contract for a mobile phone subscription is made online, a method is adopted in which a subscriber is requested to transmit an image of an identity certificate of the subscriber, and the identity of the subscriber is proved by using the identity certificate appearing in the transmitted image.

<CIT> discloses the authentication of documents based on shadow information. To avoid that a photo on an ID card is replaced an image of the document is taken. If a shadow is found in the image it is assumed that the documents is a counterfeit.

To appropriately prove the identity of a user, it is desired to appropriately determine whether or not an identity certificate appearing in an image is authentic. In other words, it is desired to appropriately determine whether an image used to prove the identity of a user is an image generated by capturing an image of a real identity certificate, or an image generated by capturing an image of a fake identity certificate (for example, a document created by copying the identity certificate). In the current situation, however, a human determines, by visually checking an image, whether or not an identity certificate appearing in the image is authentic. Accordingly, a technical problem arises that costs are relatively high for determining whether or not an identity certificate appearing in an image is authentic.

An example object of the present disclosure is to provide a certificate determination apparatus, a certificate determination method, and a recording medium by which the above-described technical problem can be solved. As an example, an example object of the present disclosure is to provide a certificate determination apparatus, a certificate determination method, and a recording medium that are able to determine whether or not an identity certificate appearing in an image is authentic, at relatively low costs.

One example aspect of a certificate determination apparatus in the present disclosure includes: a generation unit configured to generate, based on an image in which an identity certificate appears, shadow information related a shadow of the identity certificate appearing in the image; and a determination unit configured to determine, based on the shadow information, whether or not the identity certificate appearing in the image is authentic.

One example aspect of a certificate determination method in the present disclosure includes: One example aspect of a certificate determination apparatus in the present disclosure includes: a generation unit configured to generate, based on an image in which an identity certificate appears, shadow information related a shadow of the identity certificate appearing in the image; and a determination unit configured to determine, based on the shadow information, whether or not the identity certificate appearing in the image is authentic.

One example aspect of a recording medium in the present disclosure is a recording medium storing a computer program that causes a computer to execute a certificate determination method, the certificate determination method includes: a generation step of generating, based on an image in which an identity certificate appears, shadow information related a shadow of the identity certificate appearing in the image; and a determination step of determining, based on the shadow information, whether or not the identity certificate appearing in the image is authentic.

Hereinafter, example embodiments of a certificate determination apparatus, a certificate determination method, and a recording medium are described with reference to the drawings. In the following, a description is given of certificate determination systems SYS to which the example embodiments of the certificate determination apparatus, the certificate determination method, and the recording medium are applied.

First, a certificate determination system SYS according to a first example embodiment is described. In the following description, the certificate determination system SYS according to the first example embodiment is referred to as "certificate determination system SYSa".

First, a configuration of the certificate determination system SYSa according to the first example embodiment is described with reference to <FIG> is a block diagram illustrating the configuration of the certificate determination system SYSa according to the first example embodiment.

As illustrated in <FIG>, the certificate determination system SYSa includes a light source <NUM>, a camera <NUM>, which is one specific example of "imaging apparatus", and a determination server <NUM>, which is one specific example of "certificate determination apparatus". At least one of the light source <NUM> and the camera <NUM> is capable of communicating with the determination server <NUM> through a communication network (or an arbitrary control line) <NUM>. The communication network <NUM> may include a wired communication network, or may include a wireless communication network.

The light source <NUM> and the camera <NUM> are used to capture an image of an identity certificate <NUM> of a user (see <FIG>). In the first example embodiment, the identity certificate <NUM> may refer to a physical document that can be used to prove who the user is (in other words, identity or authenticity). Examples of the identity certificate <NUM> include at least one of a driver's license, a passport (travel document), an insurance certificate, an individual number card, and an ID card.

An example of the light source <NUM> and the camera <NUM> capturing an image of the identity certificate <NUM> is illustrated in <FIG>. As illustrated in <FIG>, the light source <NUM> illuminates the identity certificate <NUM> with illumination light IL. The camera <NUM> captures an image of the identity certificate <NUM> illuminated with the illumination light II, from the light source <NUM>. As a result, the camera <NUM> generates an image (hereinafter, referred to as "certificate image <NUM>" as appropriate) in which the identity certificate <NUM> appears. The camera <NUM> transmits the generated certificate image <NUM> to the determination server <NUM> through the communication network <NUM>.

It is preferable that a positional relationship between the light source <NUM> and the camera <NUM> be fixed. In other words, it is preferable that the positional relationship between the light source <NUM> and the camera <NUM> not be changed. In such a case, it is preferable that the positional relationship between the light source <NUM> and the camera <NUM> be information known to the determination server <NUM>. When the positional relationship between the light source <NUM> and the camera <NUM> is fixed, a single apparatus may include the light source <NUM> and the camera <NUM>. In other words, a light source and a camera included in a single apparatus may be used for the light source <NUM> and the camera <NUM>. As an example, a light source and a camera included in a smartphone or a tablet terminal may be used for the light source <NUM> and the camera <NUM>.

However, the positional relationship between the light source <NUM> and the camera <NUM> does not need to be fixed. In other words, the positional relationship between the light source <NUM> and the camera <NUM> may be changed. In such a case, it is also preferable that the positional relationship between the light source <NUM> and the camera <NUM> be information known to the determination server <NUM>. In other words, when the positional relationship between the light source <NUM> and the camera <NUM> is changed, it is preferable that the determination server <NUM> be able to identify the changed positional relationship between the light source <NUM> and the camera <NUM>.

The determination server <NUM> performs certificate determination operation for determining, based on the certificate image <NUM>, whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic. Specifically, based on the certificate image <NUM>, the determination server <NUM> determines whether the certificate image <NUM> is an image generated by capturing an image of the real identity certificate <NUM> (hereinafter, referred to as "identity certificate 5_real" as appropriate), or is an image generated by capturing an image of a fake identity certificate <NUM> (hereinafter, referred to as "identity certificate 5_fake" as appropriate). Note that the real identity certificate 5_real in the first example embodiment may refer to the identity certificate <NUM> itself (in other words, the original identity certificate <NUM>). In contrast, the fake identity certificate 5_fake in the first example embodiment may refer to an imitated identity certificate <NUM> that is not the identity certificate <NUM> itself. Examples of the identity certificate 5_fake include at least one of a document created by copying the identity certificate 5_real, and a display on which an image of the identity certificate 5_real appears.

In the first example embodiment, in particular, the determination server <NUM> generates shadow information related to a shadow <NUM> of the identity certificate <NUM> appearing the certificate image <NUM> and, based on the generated shadow information, determines whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic. Specifically, when the light source <NUM> illuminates the identity certificate 5_real with the illumination light IL as illustrated in <FIG> described above, a shadow <NUM> of the identity certificate 5_real is normally created. As a result, in the certificate image <NUM> in which the identity certificate 5_real appears, the shadow <NUM> of the identity certificate 5_real also appears, as illustrated in <FIG> that is an example of the certificate image <NUM>. In contrast, the thickness of the identity certificate 5_fake, generally, differs from that of the identity certificate 5_real in many cases. For example, when a document created by copying the identity certificate 5_real as described above is used as the identity certificate 5_fake, the thickness of the identity certificate 5_fake is thinner than the thickness of the identity certificate 5_real. As a result, it is highly probable that a state of a shadow <NUM> of the identity certificate 5_fake created when the light source <NUM> illuminates the identity certificate 5_fake with the illumination light IL is different from a state of the shadow <NUM> of the identity certificate 5_fake created when the light source <NUM> illuminates the identity certificate 5_real with the illumination light IL. Accordingly, the determination server <NUM> can determine, based on the shadow information, whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic.

An example of a configuration of the determination server <NUM> performing such certificate determination operation is illustrated in <FIG>. As illustrated in <FIG>, the determination server <NUM> includes a computation apparatus <NUM>, a storage apparatus <NUM>, and a communication apparatus <NUM>. The computation apparatus <NUM>, the storage apparatus <NUM>, and the communication apparatus <NUM> are connected through a data bus <NUM>.

The computation apparatus <NUM> includes, for example, a CPU (Central Processing Unit). The computation apparatus <NUM> reads a computer program. For example, the computation apparatus <NUM> may read the computer program stored in the storage apparatus <NUM>. For example, the computation apparatus <NUM> may read the computer program stored in a computer-readable non-transitory recording medium, by using an undepicted recording medium reading apparatus. The computation apparatus <NUM> may acquire (that is, may download or may read) the computer program, via the communication apparatus <NUM>, from an undepicted apparatus placed outside of the determination server <NUM>. The computation apparatus <NUM> executes the read computer program. As a result, in the computation apparatus <NUM>, a logical functional block is implemented for performing an operation (for example, the above-described certificate determination operation) to be performed by the determination server <NUM>. In other words, the computation apparatus <NUM> can function as a controller for implementing the logical functional block for performing the operation to be performed by the determination server <NUM>.

<FIG> illustrates examples of the logical functional block implemented in the computation apparatus <NUM> to perform the certificate determination operation. As illustrated in <FIG>, an image analysis unit <NUM> and a determination unit <NUM>, which is one specific example of "determination unit", are implemented in the computation apparatus <NUM>. Further in the image analysis unit <NUM>, a shadow detection unit <NUM>, which is one specific example of "generation unit", is implemented as a logical functional block. Operations of the image analysis unit <NUM> and the determination unit <NUM> will be described in detail later with reference to <FIG> and others.

The storage apparatus <NUM> can store desired data. For example, the storage apparatus <NUM> may temporarily store the computer program that is executed by the computation apparatus <NUM>. The storage apparatus <NUM> may temporarily store data that is temporarily used by the computation apparatus <NUM> when the computation apparatus <NUM> executes the computer program. The storage apparatus <NUM> may store data that the determination server <NUM> retains on a long-term basis. Note that the storage apparatus <NUM> may include at least one of a RAM (Random Access Memory), a ROM (Read Only Memory), a hard disk apparatus, a magneto-optical disk apparatus, an SSD (Solid State Drive), and a disk array apparatus.

The communication apparatus <NUM> is capable of communicating with at least one of the light source <NUM> and the camera <NUM> through the communication network <NUM>. For example, the communication apparatus <NUM> may receive a certificate image <NUM> transmitted from the camera <NUM> through the communication network <NUM>.

Next, the certificate determination operation performed by the determination server <NUM> in the first example embodiment is described with reference to <FIG> is a flowchart illustrating a flow of the certificate determination operation performed by the determination server <NUM> in the first example embodiment.

As illustrated in <FIG>, the image analysis unit <NUM> acquires, by using the communication apparatus <NUM>, a certificate image <NUM> transmitted from the camera <NUM> through the communication network <NUM> (step S <NUM>).

Thereafter, based on the certificate image <NUM> acquired in step S11, the shadow detection unit <NUM> in the image analysis unit <NUM> detects a shadow <NUM> of an identity certificate <NUM> appearing in the certificate image <NUM> (step S12). Specifically, the shadow detection unit <NUM>, by analyzing the certificate image <NUM>, identifies an image region (hereinafter, referred to as "certificate region <NUM>", see <FIG>) where the identity certificate <NUM> appears in the certificate image <NUM>. Thereafter, the shadow detection unit <NUM>, by analyzing the certificate image <NUM>, determines whether or not there exists an image region (hereinafter, referred to as "shadow region <NUM>", see <FIG>) that extends outward from the certificate region <NUM> and in which the shadow <NUM> of the identity certificate <NUM> appears. When the shadow region <NUM> exists, the shadow detection unit <NUM> determines that the shadow <NUM> of the identity certificate <NUM> appears in the certificate image <NUM>. When the shadow region <NUM> does not exist, the shadow detection unit <NUM> determines that the shadow <NUM> of the identity certificate <NUM> does not appear in the certificate image <NUM>. A result of the detection of the shadow <NUM> by the shadow detection unit <NUM> in step S12 is outputted, as shadow information, from the shadow detection unit <NUM> to the determination unit <NUM>. In other words, in the first example embodiment, the shadow information including information related to presence or absence of the shadow <NUM> in the certificate image <NUM> is outputted from the shadow detection unit <NUM> to the determination unit <NUM>.

Thereafter, based on the shadow information, the determination unit <NUM> determines whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic (step S13). Specifically, as described above, the probability is relatively high that the thickness of an identity certificate 5_fake is thinner (particularly, much thinner) than the thickness of an identity certificate 5_real. Accordingly, as illustrated in <FIG> that is a side view illustrating the identity certificate 5_fake illuminated by the light source <NUM>, it is highly probable that a shadow <NUM> of the identity certificate 5_fake is hardly created when the light source <NUM> illuminates the identity certificate <NUM>_fake with the illumination light IL. As a result, it is highly probable that the shadow <NUM> of the identity certificate 5_fake does not appear in the certificate image <NUM> in which the identity certificate 5_fake appears. In contrast, as illustrated in <FIG> that is a side view illustrating the identity certificate 5_real illuminated by the light source <NUM>, it is highly probable that a shadow <NUM> of the identity certificate 5_fake is created when the light source <NUM> illuminates the identity certificate 5_real with the illumination light IL. The reason is that the identity certificate 5_real has a certain thickness. As a result, it is highly probable that the shadow <NUM> of the identity certificate 5_real appears in the certificate image <NUM> in which the identity certificate 5_real appears. Accordingly, based on the shadow information, the determination unit <NUM> may determine that the identity certificate <NUM> appearing in the certificate image <NUM> is fake when the shadow <NUM> does not appear in the certificate image <NUM>. In other words, the determination unit <NUM> may determine that the identity certificate 5_fake appears in the certificate image <NUM>. In contrast, based on the shadow information, the determination unit <NUM> may determine that the identity certificate <NUM> appearing in the certificate image <NUM> is authentic when the shadow <NUM> appears in the certificate image <NUM>. In other words, the determination unit <NUM> may determine that the identity certificate 5_real appears in the certificate image <NUM>.

As described above, the certificate determination system SYSa (particularly, the determination server <NUM>) according to the first example embodiment can determine whether or not an identity certificate <NUM> appearing in a certificate image <NUM> is authentic, based on presence or absence of a shadow <NUM> of the identity certificate <NUM> appearing in the certificate image <NUM>. Accordingly, the certificate determination system SYSa (particularly, the determination server <NUM>) can determine whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic, at relatively low costs, compared to a case where a human determines, by visually checking the certificate image <NUM>, whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic.

Next, a certificate determination system SYS according to a second example embodiment is described. In the following description, the certificate determination system SYS according to the second example embodiment is referred to as "certificate determination system SYSb".

The certificate determination system SYSb according to the second example embodiment is different, compared to the certificate determination system SYSa according to the first example embodiment, in that the certificate determination system SYSb includes a determination server 3b in place of the determination server <NUM>. Other characteristics of the certificate determination system SYSb may be the same as the other characteristics of the certificate determination system SYSa.

The determination server 3b, similarly to the determination server <NUM>, generates shadow information related to a shadow <NUM> of an identity certificate <NUM> appearing in a certificate image <NUM>, and performs certificate determination operation for determining, based on the generated shadow information, whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic. However, the determination server 3b generates the shadow information including information related a length L of the shadow <NUM> of the identity certificate <NUM>. In such a respect, the determination server 3b is different from the determination server <NUM> that generates shadow information including information related to presence or absence of the shadow <NUM> of the identity certificate <NUM>. Other characteristics of the determination server 3b may be the same as the other characteristics of the determination server <NUM>. Accordingly, in the following, a description is given of the determination server 3b in the second example embodiment, focused mainly on differences between the determination server 3b and the determination server <NUM>, with reference to <FIG> is a block diagram illustrating a configuration of the determination server 3b in the second example embodiment.

As illustrated in <FIG>, the determination server 3b is different, compared to the determination server <NUM>, in that an image analysis unit 311b, in place of the image analysis unit <NUM>, is implemented in the computation apparatus <NUM>. Further, the determination server 3b is different, compared to the determination server <NUM>, in that the storage apparatus <NUM> stores a shadow length DB 321b, which is one specific example of "estimated length data". Other components of the determination server 3b may be the same as the other components of the determination server <NUM>.

The image analysis unit 311b is different, compared to the image analysis unit <NUM>, in that the image analysis unit 311b includes a certificate identification unit 314b, a camera angle calculation unit 315b, which is one specific example of "calculation unit", a light source angle calculation unit 316b, which is one specific example of "calculation unit", and a shadow length calculation unit 317b, which is one specific example of "generation unit", in place of the shadow detection unit <NUM>. Note that although operations of the certificate identification unit 314b, the camera angle calculation unit 315b, the light source angle calculation unit 316b, and the shadow length calculation unit 317b will be described in detail later with reference to <FIG> and others, an outline of the operations is described below. The certificate identification unit 314b identifies, based on a certificate image <NUM>, a type of an identity certificate <NUM> appearing in the certificate image <NUM>. The camera angle calculation unit 315b calculates, based on the certificate image <NUM>, an angle of the camera <NUM> (hereinafter, referred to as "camera angle θc") to the identity certificate <NUM>. The light source angle calculation unit 316b calculates, based on the certificate image <NUM>, an angle of the light source <NUM> (hereinafter, referred to as "light source angle θo") to the identity certificate <NUM>. The shadow length calculation unit 317b calculates, based on the certificate image <NUM>, a length L of a shadow <NUM> of the identity certificate <NUM> appearing in the certificate image <NUM>. The determination unit <NUM> determines, based on the camera angle θc calculated by the camera angle calculation unit 315b, the light source angle θo calculated by the light source angle calculation unit 316b, and the length L of the shadow <NUM> calculated by the shadow length calculation unit 317b, whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic.

The camera angle θc is a parameter (in other words, an indicator) indicating a relative positional relationship between the camera <NUM> and the identity certificate <NUM>. An example of the camera angle θc is illustrated in <FIG>. For example, as illustrated in <FIG>, the camera angle θc may indicate an angle that a camera axis AC extending from the camera <NUM> forms with a surface of the identity certificate <NUM>. For example, the camera angle θc may indicate at least one of an angle that the camera axis AC forms with an axis along the surface of the identity certificate <NUM> (for example, an axis along any one of a short side and a long side of the identity certificate <NUM>) in a vertical direction (see <FIG>), and an angle that the camera axis AC forms with the axis along the surface of the identity certificate <NUM> in a horizonal direction (not illustrated in <FIG>). The camera axis AC may be an axis extending from the camera <NUM> toward a predetermined position on the identity certificate <NUM> (in the example illustrated in <FIG>, an upper end of the identity certificate <NUM>). The camera axis AC may be an axis along an optical axis of an optical system (for example, a lens) included in the camera <NUM>.

The light source angle θo is a parameter (in other words, an indicator) indicating a relative positional relationship between the light source <NUM> and the identity certificate <NUM>. An example of the light source angle θo is illustrated in <FIG>. For example, as illustrated in <FIG>, the light source angle θo may indicate an angle that a light source axis OC extending from the light source <NUM> forms with the surface of the identity certificate <NUM>. For example, the light source angle θo may indicate at least one of an angle that the light source axis OC forms with an axis along the surface of the identity certificate <NUM> (for example, an axis along any one of the short side and the long side of the identity certificate <NUM>) in the vertical direction (see <FIG>), and an angle that the light source axis OC forms with the axis along the surface of the identity certificate <NUM> in the horizontal direction (not illustrated in <FIG>). The light source axis OC may be an axis extending from the light source <NUM> toward a predetermined position on the identity certificate <NUM> (in the example illustrated in <FIG>, the upper end of the identity certificate <NUM>). The light source axis OC may be an axis along an optical axis of an optical system (for example, a lens) included in the light source <NUM>. The light source axis OC may be an axis along a direction in which the illumination light IL emitted from the light source <NUM> travels.

The shadow length DB 321b is a database that is referred to by the determination unit <NUM> in order to determine whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic. Specifically, the shadow length DB 321b is used to estimate a length L of a shadow <NUM> of the identity certificate <NUM> presumed to appear in the certificate image <NUM>, based on the camera angle θc calculated by the camera angle calculation unit 315b and the light source angle θo calculated by the light source angle calculation unit 316b. Accordingly, the shadow length DB 321b is a database indicating a relationship between the camera angle θc and the light source angle θο, and the length L of the shadow <NUM>. An example of a data structure of the shadow length DB 321b is illustrated in <FIG>. As illustrated in <FIG>, the shadow length DB 321b includes a plurality of data records 322b. In each data record 322b, the length L of the shadow <NUM> of the identity certificate 5_real is associated with the camera angle θc and the light source angle θo. The shadow <NUM> here is a shadow presumed to appear in a certificate image <NUM> when it is assumed that the camera <NUM> captures an image of the real identity certificate 5_real illuminated by the light source <NUM> in a situation where the camera angle θc is a predetermined first angle and the light source angle θo is a predetermined second angle. In other words, in each data record 322b, associated with the camera angle θc and the light source angle θo is the logical length L (in other words, the length L in design) of the shadow <NUM> of the identity certificate 5_real presumed to appear in the certificate image <NUM> when it is assumed that the camera <NUM> disposed in such a manner that the camera angle θc is the predetermined second angle captures an image of the identity certificate 5_real illuminated by the light source <NUM> disposed in such a manner that the light source angle θo is the predetermined second angle. In the example illustrated in <FIG>, the shadow length DB 321b includes, for example, (i) a data record 322b indicating that when it is assumed that the camera <NUM> disposed in such a manner that the camera angle θc is an angle a1 captures an image of the identity certificate 5_real illuminated by the light source <NUM> disposed in such a manner that the light source angle θo is an angle a2, the length L of the shadow <NUM> of the identity certificate 5_real presumed to then appear in the certificate image <NUM> is a4, and (ii) a data record 322b indicating that when it is assumed that the camera <NUM> disposed in such a manner that the camera angle θc is an angle b <NUM> captures an image of the identity certificate 5_real illuminated by the light source <NUM> disposed in such a manner that the light source angle θo is an angle b2, the length L of the shadow <NUM> of the identity certificate 5_real presumed to then appear in the certificate image <NUM> is b4.

The length L of the shadow <NUM> of the identity certificate 5_real may change also depending on a distance (that is, an interval) D between the light source <NUM> and the camera <NUM>, in addition to the light source angle θo and the camera angle θc. Accordingly, in each data record 322b, the length L of the shadow <NUM> of the identity certificate 5_real may be associated with the camera angle θc, the light source angle θο, and the distance D between the light source <NUM> and the camera <NUM>. The shadow <NUM> here is a shadow presumed to appear in a certificate image <NUM> when it is assumed that the camera <NUM> captures an image of the real identity certificate 5_real illuminated by the light source <NUM> in a situation where the camera angle θc is the predetermined first angle, the light source angle θo is the predetermined second angle, and the distance D between the light source <NUM> and the camera <NUM> is a predetermined distance. Note that the "distance" in the second example embodiment may include at least one of a distance along an X axis, a distance along a Y axis, and a distance along a Z axis in an XYZ coordinate system with the X, Y, and Z axes being mutually orthogonal. In the example illustrated in <FIG>, the shadow length DB 321b includes, for example, (i) the data record 322b indicating that when it is assumed that the camera <NUM> disposed in such a manner that the camera angle θc is the angle a1 and the camera <NUM> is a distance a3 away from the light source <NUM> captures an image of the identity certificate 5_real illuminated by the light source <NUM> disposed in such a manner that the light source angle θo is the angle a2, the length L of the shadow <NUM> of the identity certificate 5_real presumed to then appear in the certificate image <NUM> is a4, and (ii) the data record 322b indicating that when it is assumed that the camera <NUM> disposed in such a manner that the camera angle θc is the angle b1 and the camera <NUM> is a distance b3 away from the light source <NUM> captures an image of the identity certificate 5_real illuminated by the light source <NUM> disposed in such a manner that the light source angle θo is the angle b2, the length L of the shadow <NUM> of the identity certificate 5_real presumed to then appear in the certificate image <NUM> is b4.

The length L of the shadow <NUM> of the identity certificate 5_real may change also depending on the thickness of the identity certificate 5_real, in addition to the light source angle θo and the camera angle θc. The thickness of the identity certificate 5_real depends on a type of the identity certificate 5_real. For example, the thickness of a driver's license, which is an example of the identity certificate 5_real, differs from the thickness of a passport, which is an example of the identity certificate 5_real. Accordingly, the shadow length DB 321b may include a data record 322b, for each type of identity certificate 5_real. In other words, the shadow length DB 321b may include a data record 322b indicating the length of the shadow <NUM> of the identity certificate 5_real of a first type, and a data record 322b indicating the length of the shadow <NUM> of the identity certificate 5_real of a second type that is different from the first type. In the example illustrated in <FIG>, the shadow length DB 321b includes data records 322b each indicating the length L of the shadow <NUM> of a driver's license, which is an example of the identity certificate 5_real, and data records 322b each indicating the length L of the shadow <NUM> of a passport, which is an example of the identity certificate 5_real.

Based on such a shadow length DB 321b, and on the camera angle θc calculated by the camera angle calculation unit 315b and the light source angle θo calculated by the light source angle calculation unit 316b, the determination unit <NUM> estimates a length L of a shadow <NUM> of the identity certificate <NUM> (that is, an estimated value of the length L of the shadow <NUM>) presumed to appear in the certificate image <NUM>. In other words, the determination unit <NUM> estimates the length L of the shadow <NUM> (that is, an estimated value of the length L of the shadow <NUM>) appearing in the certificate image <NUM> when it is assumed that the real identity certificate 5_real appears in the certificate image <NUM>. Thereafter, based on the length L of the shadow <NUM> estimated by the determination unit <NUM> (that is, the estimated value of the length L of the shadow <NUM>), and the length L of the shadow <NUM> calculated by the shadow length calculation unit 317b (that is, a calculated value of the length L of the shadow <NUM>), the determination unit <NUM> determines whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic.

Next, the certificate determination operation performed by the determination server <NUM> in the second example embodiment is described with reference to <FIG> is a flowchart illustrating a flow of the certificate determination operation performed by the determination server <NUM> in the second example embodiment.

As illustrated in <FIG>, the image analysis unit <NUM>, by using the communication apparatus <NUM>, acquires a certificate image <NUM> transmitted from the camera <NUM> through the communication network <NUM> (step S21).

Thereafter, based on the certificate image <NUM> acquired in step S11, the certificate identification unit 314b in the image analysis unit <NUM> identifies a type of an identity certificate <NUM> appearing in the certificate image <NUM> (step S22). In other words, the certificate identification unit 314b, by analyzing the certificate image <NUM>, identifies the type of the identity certificate <NUM> appearing in the certificate image <NUM> (step S22). For example, the certificate identification unit 314b may identify the type of the identity certificate <NUM>, based on a characteristic (for example, at least one of size, color, and shape) of the identity certificate <NUM> appearing in the certificate image <NUM>. For example, the certificate identification unit 314b may identify the type of the identity certificate <NUM> by performing, on the certificate image <NUM>, a pattern matching process using a template in conformity with a format of the identity certificate <NUM>. At the time, the certificate identification unit 314b, similarly to the shadow detection unit <NUM> in the first example embodiment, may identify an image region (that is, a certificate region <NUM>) where the identity certificate <NUM> appears in the certificate image <NUM>. Note that when the type of the identity certificate <NUM> appearing in the certificate image <NUM> is already known to the determination server <NUM>, the image analysis unit <NUM> does not need to identify the type of the identity certificate <NUM>. In such a case, the image analysis unit <NUM> does not need to include the certificate identification unit 314b.

Thereafter, based on the certificate image <NUM> acquired in step S11, the shadow length calculation unit 317b calculates a length L of a shadow <NUM> of the identity certificate <NUM> appearing in the certificate image <NUM> (step S23). Specifically, the size of the identity certificate <NUM> is a unique value depending on the type of the identity certificate <NUM>. Accordingly, the size of the identity certificate <NUM> can be used for a reference length when the length L of the shadow <NUM> is calculated. Accordingly, first, the shadow length calculation unit 317b identifies a size (for example, a length of at least one of a long side and a short side) of the identity certificate <NUM>, based on the type of the identity certificate <NUM> identified by the certificate identification unit 314b. The size of the identity certificate <NUM> is equivalent to the size of the certificate region <NUM> in the certificate image <NUM>. Further, the shadow length calculation unit 317b, similarly to the shadow detection unit <NUM> described in the first example embodiment, detects an image region (that is, a shadow region <NUM>) where a shadow extending outward from the certificate region <NUM> appears. Thereafter, the shadow length calculation unit 317b calculates a size of the detected shadow region <NUM>, based on the size of the certificate region <NUM>. The size of the shadow region <NUM> may be, for example, a distance from one end portion of the shadow region <NUM> adjacent to the certificate region <NUM> to the other end portion of the shadow region <NUM> far from the certificate region <NUM>, along a direction in which the illumination light IL travels. The calculated size of the shadow region <NUM> is used for the length L of the shadow <NUM>. A result of the calculation of the length L of the shadow <NUM> by the shadow length calculation unit 317b in step S23 is outputted, as shadow information, from the shadow length calculation unit 317b to the determination unit <NUM>. In other words, in the second example embodiment, the shadow information including information related to the length L of the shadow <NUM> in the certificate image <NUM> is outputted from the shadow length calculation unit 317b to the determination unit <NUM>.

In parallel with, or immediately after, the operation in step S23, the camera angle calculation unit 315b, based on the certificate image <NUM> acquired in step S <NUM>, calculates an angle of the camera <NUM> (that is, a camera angle θc) to the identity certificate <NUM> (step S24). Specifically, when the camera angle θc is changed, a change occurs in the ratio between the lengths of two intersecting sides (for example, the long side and the short side) of the identity certificate <NUM> appearing in the certificate image <NUM>. For example, <FIG> illustrates a certificate image <NUM> generated in a situation where the camera angle θc between the camera axis AC and the surface of the identity certificate <NUM> is relatively large, and <FIG> illustrates a certificate image <NUM> generated in a situation where the camera angle θc between the camera axis AC and the surface of the identity certificate <NUM> is relatively small. As illustrated in <FIG>, the smaller the camera angle θc is, the smaller the ratio of the short side (in the examples illustrated in <FIG>, a side extending in up-down directions) of the identity certificate <NUM> to the long side (in the examples illustrated in <FIG>, a side extending in right-left directions) of the identity certificate <NUM> is. Accordingly, the camera angle calculation unit 315b may calculate the camera angle θc, based on the ratio between the lengths of the two intersecting sides of the identity certificate <NUM>. The camera angle θc calculated here corresponds to a camera angle θc at a time when the camera <NUM> captures the image of the identity certificate <NUM>. The camera angle θc calculated in step S24 is outputted from the camera angle calculation unit 315b to the determination unit <NUM>.

Thereafter, based on the camera angle θc identified in step S24, the light source angle calculation unit 316b calculates an angle of the light source <NUM> (that is, a light source angle θo) to the identity certificate <NUM> (step S25). Specifically, in a case where the positional relationship between the light source <NUM> and the camera <NUM> is fixed as described above, when the camera angle θc is determined, the light source angle θo is also uniquely determined. Alternatively, in a case where the positional relationship between the light source <NUM> and the camera <NUM> is information known to the determination server <NUM> even if the positional relationship between the light source <NUM> and the camera <NUM> is not fixed, when the camera angle θc is determined, the light source angle θo is also uniquely determined. Accordingly, the light source angle calculation unit 316b can calculate the light source angle θο, based on the camera angle θc (further, based also on the positional relationship between the light source <NUM> and the camera <NUM> as necessary). The light source angle θo calculated here corresponds to a light source angle θo at the time when the camera <NUM> captures the image of the identity certificate <NUM>. The light source angle θo calculated in step S25 is outputted from the light source angle calculation unit 316b to the determination unit <NUM>.

Thereafter, based on the camera angle θc calculated in step S24, the light source angle θo calculated in step S25, and the shadow length DB 321b, the determination unit <NUM> estimates a length L of a shadow <NUM> of the identity certificate <NUM> presumed to appear in the certificate image <NUM> (step S26). In other words, the determination unit <NUM> estimates the length L of the shadow <NUM> (that is, an estimated value of the length L of the shadow <NUM>) appearing in the certificate image <NUM> when it is assumed that the real identity certificate 5_real appears in the certificate image <NUM>. Specifically, the determination unit <NUM> estimates the logical length L (in other words, the length L in design) of the shadow <NUM> of the identity certificate 5_real presumed to appear in the certificate image <NUM> when it is assumed that the camera <NUM> disposed at a position based on the camera angle θc calculated in step S24 captures an image of the real identity certificate 5_real illuminated by the light source <NUM> disposed at a position based on the light source angle θo calculated in step S25. To estimate the length L of the shadow <NUM>, for example, the determination unit <NUM> extracts, from the shadow length DB 321b, a data record 322b corresponding to the camera angle θc calculated in step S24 and the light source angle θo calculated in step S25. Thereafter, the determination unit <NUM> uses a length L of the shadow <NUM> indicated in the extracted data record 322b for the estimated value of the length L of the shadow <NUM>.

Note that when each data record 322b includes information related to the distance D between the light source <NUM> and the camera <NUM> as described above, the determination unit <NUM> may identify a distance D between the light source <NUM> and the camera <NUM>, and may extract, from the shadow length DB 321b, a data record 322b corresponding to the identified distance D. The distance D between the light source <NUM> and the camera <NUM> is a fixed value when the positional relationship between the light source <NUM> and the camera <NUM> is fixed. When the positional relationship between the light source <NUM> and the camera <NUM> is not fixed, the distance D between the light source <NUM> and the camera <NUM> is a variable value. However, when the positional relationship between the light source <NUM> and the camera <NUM> is information known to the determination server <NUM> as described above, the determination server <NUM> can identify the distance D between the light source <NUM> and the camera <NUM>.

Thereafter, based on the calculated value of the length L of the shadow <NUM> calculated in step S23, and the estimated value of the length L of the shadow <NUM> estimated in step S26, the determination unit <NUM> determines whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic (step S27). Specifically, as illustrated in <FIG>, when the identity certificate <NUM> appearing in the certificate image <NUM> is authentic (that is, the identity certificate 5_real), the calculated value L1 of the length L of the shadow <NUM> is approximately the same value as the estimated value of the length L of the shadow <NUM> (that is, the logical length L). In contrast, as illustrated <FIG>, when the identity certificate <NUM> appearing in the certificate image <NUM> is not authentic (that is, an identity certificate 5_fake), the calculated value L2 of the length L of the shadow <NUM> is a different value from the estimated value of the length L (that is, the logical length L) of the shadow <NUM>. The reason is that when the identity certificate <NUM> appearing in the certificate image <NUM> is not authentic, the calculated value of the length L of the shadow <NUM> indicates the length L of the shadow <NUM> of the identity certificate 5_fake that has a different thickness from the thickness of the identity certificate 5_real. Accordingly, the calculated value L2 of the length L of the shadow <NUM> of the identity certificate 5_fake is a different value from the length L1 of the shadow <NUM> of the identity certificate 5_real (alternatively, the estimated value of the length L of the shadow <NUM> corresponding to the logical value of the length L1 of the shadow <NUM> of the identity certificate 5_real). Accordingly, the determination unit <NUM> can determine whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic, by comparing the calculated value of the length L of the shadow <NUM> calculated in step S23 and the estimated value of the length L of the shadow <NUM> estimated in step S26. For example, when a difference between the calculated value of the length L of the shadow <NUM> and the estimated value of the length L of the shadow <NUM> is more than a predetermined first allowance (that is, the calculated value of the length L of the shadow <NUM> is greatly different from the estimated value of the length L of the shadow <NUM>), the determination unit <NUM> may determine that the identity certificate <NUM> appearing in the certificate image <NUM> is not authentic. For example, when the difference between the calculated value of the length L of the shadow <NUM> and the estimated value of the length L of the shadow <NUM> is less than a predetermined second allowance that is equal to or less than the first allowance (that is, the calculated value of the length L of the shadow <NUM> is not greatly different from, or approximately the same as, the estimated value of the length L of the shadow <NUM>), the determination unit <NUM> may determine that the identity certificate <NUM> appearing in the certificate image <NUM> is authentic.

Note that the first and second allowances may be set to appropriate values that make it possible to distinguish, based on the length L of the shadow <NUM> of the identity certificate <NUM> appearing in the certificate image <NUM>, between a state where the identity certificate <NUM> appearing in the certificate image <NUM> is authentic and a state where the identity certificate <NUM> appearing in the certificate image <NUM> is not authentic. Such first and second allowances may be set by experiment or simulation. The first allowance may be the same as, or may be different from, the second allowance.

As described above, the certificate determination system SYSb (particularly, the determination server 3b) according to the second example embodiment can determine whether or not an identity certificate <NUM> appearing in a certificate image <NUM> is authentic, based on the length L of a shadow <NUM> of the identity certificate <NUM> appearing in the certificate image <NUM>. Accordingly, the certificate determination system SYSb (particularly, the determination server 3b) can determine whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic, at relatively low costs, compared to a case where a human determines, by visually checking the certificate image <NUM>, whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic.

Further in the second example embodiment, even if a shadow <NUM> of the identity certificate <NUM> appears in the certificate image <NUM>, the determination server 3b determines that the identity certificate <NUM> appearing in the certificate image <NUM> is not authentic when the length L of the shadow <NUM> appearing in the certificate image <NUM> is different from the length L of a shadow <NUM> of the real identity certificate 5_real. Accordingly, the certificate determination system SYSb (particularly, the determination server 3b) can determine whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic, with higher accuracy.

Next, modified examples of the certificate determination system SYSb according to the second example embodiment are described.

In a first modified example, the determination server 3b may generate shadow information including information related to a change (typically, time-series changes) in the length L of a shadow <NUM> of the identity certificate <NUM>. Specifically, the determination server 3b acquires a plurality of certificate images <NUM> transmitted from the camera <NUM>. The plurality of certificate images <NUM> are generated by repeating an operation, by the camera <NUM>, of capturing an image of the identity certificate <NUM>, and an operation of changing a positional relationship between the identity certificate <NUM> and at least one of the light source <NUM> and the camera <NUM>. In other words, in the first modified example, each time the positional relationship between the identity certificate <NUM> and at least one of the light source <NUM> and the camera <NUM> is changed, the camera <NUM> captures an image of the identity certificate <NUM>. Note that the plurality of certificate images <NUM> may be a plurality of images included in a video. Thereafter, the shadow length calculation unit 317b in the determination server 3b calculates a length L of a shadow <NUM> of the identity certificate <NUM> appearing in each of the plurality of certificate images <NUM>. As a result, the shadow length calculation unit 317b can calculate time-series changes in the length L of the shadow <NUM>. Results of the calculation of the length L of the shadow <NUM> by the shadow length calculation unit 317b are outputted, as shadow information, from the shadow length calculation unit 317b to the determination unit <NUM>.

Moreover, the camera angle calculation unit 315b calculates a camera angle θc, based on each of the plurality of certificate images <NUM>. As a result, the camera angle calculation unit 315b calculates time-series changes in the camera angle θc. Similarly, the light source angle calculation unit 316b calculates time-series changes in the light source angle θο, based on the time-series changes in the camera angle θc.

Thereafter, based on the time-series changes in the camera angle θc, the time-series changes in the light source angle θο, and the shadow length DB 321b, the determination unit <NUM> estimates time-series changes in the length L of a shadow <NUM> of the identity certificate <NUM> presumed to appear in the certificate images <NUM>. In other words, the determination unit <NUM> estimates time-series changes in the length L of the shadow <NUM> (that is, estimated values of time-series changes in the length L of the shadow <NUM>) appearing in the certificate images <NUM> when it is assumed that the real identity certificate 5_real appears in the certificate images <NUM>.

Thereafter, the determination unit <NUM> determines whether or not the identity certificate <NUM> appearing in the certificate images <NUM> is authentic, by comparing the calculated values of the time-series changes in the length L of the shadow <NUM> calculated by the shadow length calculation unit 317b and the estimated values of the time-series changes in the length L of the shadow <NUM> estimated by the determination unit <NUM>. In other words, in the first modified example, the determination unit <NUM> determines whether or not the identity certificate <NUM> appearing in the certificate images <NUM> is authentic, by comparing a pattern of changes in the length L of the shadow <NUM> actually appearing in the certificate images <NUM> (hereinafter, referred to as "actual change pattern") and a pattern of changes in the length L of the shadow <NUM> presumed to appear in the certificate images <NUM> (hereinafter, referred to as "presumed change pattern"). For example, when a degree of similarity between the actual change pattern of the length L of the shadow <NUM> and the presumed change pattern of the length L of the shadow <NUM> is higher than a first threshold value, the determination unit <NUM> may determine that the identity certificate <NUM> appearing in the certificate images <NUM> is authentic. For example, when the degree of similarity between the actual change pattern of the length L of the shadow <NUM> and the presumed change pattern of the length L of the shadow <NUM> is lower than a second threshold value that is equal to or less than the first threshold value, the determination unit <NUM> may determine that the identity certificate <NUM> appearing in the certificate images <NUM> is not authentic.

Note that the first and second threshold values may be set to appropriate values that make it possible to distinguish, based on a pattern of changes (that is, time-series changes) in the length L of the shadow <NUM> of the identity certificate <NUM> appearing in the certificate images <NUM>, between a state where the identity certificate <NUM> appearing in the certificate images <NUM> is authentic and a state where the identity certificate <NUM> appearing in the certificate images <NUM> is not authentic. Such first and second threshold values may be set by experiment or simulation. The first threshold value may be the same as, or may be different from, the second threshold value.

Note that in the above description, the determination server 3b performs the certificate determination operation by using time-series changes in the length L of the shadow <NUM>. However, the determination server 3b may perform the certificate determination operation by using arbitrary time-series changes in the shadow <NUM>. In other words, the determination server 3b may perform the certificate determination operation by using time-series changes in an arbitrary parameter indicating a state of the shadow <NUM>. For example, when the positional relationship between the identity certificate <NUM> and at least one of the light source <NUM> and the camera <NUM> is changed, a change may occur in a direction in which the shadow <NUM> extends from the identity certificate <NUM> (that is, the direction of the shadow <NUM>). For example, <FIG> illustrates aspects of the direction in which the shadow <NUM> extends, the direction sequentially changing to a first direction in which the shadow <NUM> extends from the identity certificate <NUM> to the upper right, then to a second direction in which the shadow <NUM> extends upward from the identity certificate <NUM>, and then to a third direction in which the shadow <NUM> extends from the identity certificate <NUM> to the upper left. Accordingly, the determination server 3b may perform the certificate determination operation by using time-series changes in the direction in which the shadow <NUM> extends. For example, the shadow length calculation unit 317b in the determination server 3b may calculate a direction in which the shadow <NUM> of the identity certificate <NUM> appearing in each of the plurality of certificate images <NUM> extends. As a result, the shadow length calculation unit 317b can calculate time-series changes in the direction in which the shadow <NUM> extends. On the other hand, the determination unit <NUM> estimates time-series changes in the direction in which a shadow <NUM> of the identity certificate <NUM> presumed to appear in the certificate images <NUM> extends, based on the time-series changes in the camera angle θc, the time-series changes in the light source angle θο, and the shadow length DB 321b. However, in such a case, it is preferable that the direction in which the shadow <NUM> of the identity certificate 5_real presumed to appear in the certificate image <NUM> extends be associated with the camera angle θc and the light source angle θo in each data record 322b in the shadow length DB 321b, as illustrated in <FIG>, which illustrates another example of the shadow length DB 321b. Thereafter, the determination unit <NUM> may determine whether or not the identity certificate <NUM> appearing in the certificate images <NUM> is authentic, by comparing calculated values of the time-series changes in the direction in which the shadow <NUM> extends, calculated by the shadow length calculation unit 317b, and estimated values of the time-series changes in the direction in which the shadow <NUM> extends, estimated by the determination unit <NUM>. For example, when a degree of similarity between an actual change pattern of the direction in which the shadow <NUM> extends and a presumed change pattern of the direction in which the shadow <NUM> extends is higher than a third threshold value, the determination unit <NUM> may determine that the identity certificate <NUM> appearing in the certificate images <NUM> is authentic. For example, when the degree of similarity between the actual change pattern of the direction in which the shadow <NUM> extends and the presumed change pattern of the direction in which the shadow <NUM> extends is lower than a fourth threshold value that is equal to or less than the third threshold value, the determination unit <NUM> may determine that the identity certificate <NUM> appearing in the certificate images <NUM> is not authentic. Note that the third and fourth threshold values may be set to appropriate values that make it possible to distinguish, based on a pattern of changes in the direction in which the shadow <NUM> of the identity certificate <NUM> appearing in the certificate images <NUM> extends, between a state where the identity certificate <NUM> appearing in the certificate images <NUM> is authentic and a state where the identity certificate <NUM> appearing in the certificate images <NUM> is not authentic. Such third and fourth threshold values may be set by experiment or simulation. The third threshold value may be the same as, or may be different from, the fourth threshold value.

In the above description, in step S26 in <FIG>, the determination unit <NUM> estimates the length L of the shadow <NUM> of the identity certificate <NUM>, based on the camera angle θc, the light source angle θο, and the shadow length DB 321b. Thereafter, in step S27 in <FIG>, the determination unit <NUM> determines whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic, by comparing a calculated value of the length L of the shadow <NUM> calculated by the shadow length calculation unit 317b in step S23 and an estimated value of the length L of the shadow <NUM> estimated by the determination unit <NUM> in step S26.

However, in step S26, the determination unit <NUM> may estimates, based on the length L of the shadow <NUM> calculated by the shadow length calculation unit 317b in step S23 and the shadow length DB 321b, a light source angle θo that the light source <NUM> is presumed to form with the identity certificate 5_real when it is assumed that the shadow <NUM> having the length L calculated by the shadow length calculation unit 317b appears in the certificate image <NUM>. In other words, the determination unit <NUM> may estimate an estimated value of the light source angle θo.

Thereafter, in step S27, the determination unit <NUM> may determine whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic, based on the actual calculated value of the light source angle θo calculated in step S25, and the estimated value of the light source angle θo estimated in step S26.

Specifically, when the identity certificate <NUM> appearing in the certificate image <NUM> is authentic (that is, the identity certificate 5_real), the estimated value of the light source angle θo estimated in step S26 is approximately the same value as the actual calculated value of the light source angle θo. In contrast, when the identity certificate <NUM> appearing in the certificate image <NUM> is not authentic (that is, an identity certificate 5_fake), the estimated value of the light source angle θo estimated in step S26 is a different value from the actual calculated value of the light source angle θo. The reason is that since a state of the shadow <NUM> of the identity certificate 5_fake and a state of the shadow <NUM> of the identity certificate 5_fake are different, a light source angle θo back-calculated from the length L of the shadow <NUM> of the fake identity certificate 5_fake is naturally different from a light source angle θo back-calculated from the length L of the shadow <NUM> of the real identity certificate 5_real. Accordingly, the determination unit <NUM> can determine whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic, by comparing the calculated value of the light source angle θo calculated in step S24 and the estimated value of the light source angle θo estimated in step S26. In other words, the determination unit <NUM> can determine whether or not the identity certificate <NUM> appearing in the certificate image <NUM> is authentic, by determining whether or not the actual light source angle θo calculated in step S24 seems to be authentic, on the basis of an ideal light source angle θo (in other words, a light source angle θo in design) at which a shadow <NUM> having the length L calculated in step S23 is created. For example, when a difference between the calculated value of the light source angle θo and the estimated value of the light source angle θo is more than a predetermined third allowance (that is, the calculated value of the light source angle θo is greatly different from the estimated value of the light source angle θo), the determination unit <NUM> may determine that the identity certificate <NUM> appearing in the certificate image <NUM> is not authentic. For example, when the difference between the calculated value of the light source angle θo and the estimated value of the light source angle θo is less than a predetermined fourth allowance that is equal to or less than the third allowance (that is, the calculated value of the light source angle θo is not greatly different from, or approximately the same as, the estimated value of the light source angle θo), the determination unit <NUM> may determine that the identity certificate <NUM> appearing in the certificate image <NUM> is authentic.

Note that the third and the fourth allowances may be set to appropriate values that make it possible to distinguish, based on the light source angle θο, between a state where the identity certificate <NUM> appearing in the certificate image <NUM> is authentic and a state where the identity certificate <NUM> appearing in the certificate image <NUM> is not authentic. Such third and fourth allowances may be set by experiment or simulation. The third allowance may be the same as, or may be different from, the fourth allowance.

In the second modified example, the camera angle calculation unit 315b does not need to calculate a camera angle θc. In such a case, the image analysis unit <NUM> does not need to include the camera angle calculation unit 315b.

In the above description, the determination server 3b performs the certificate determination operation by using the camera angle θc. On the other hand, as described above, the camera angle θc is one specific example of a parameter indicating the relative positional relationship between the camera <NUM> and the identity certificate <NUM>. Accordingly, the determination server 3b may perform the certificate determination operation by using an arbitrary parameter indicating the relative positional relationship between the camera <NUM> and the identity certificate <NUM>, in addition to, or in place of, the camera angle θc. Examples of the arbitrary parameter indicating the relative positional relationship between the camera <NUM> and the identity certificate <NUM> include at least one of a distance from the identity certificate <NUM> to the camera <NUM>, and an azimuth direction in which the camera <NUM> is positioned relative to the identity certificate <NUM>.

Moreover, in the above description, the determination server 3b performs the certificate determination operation by using the light source angle θo. On the other hand, as described above, the light source angle θo is one specific example of a parameter indicating the relative positional relationship between the light source <NUM> and the identity certificate <NUM>. Accordingly, the determination server 3b may perform the certificate determination operation by using an arbitrary parameter indicating the relative positional relationship between the light source <NUM> and the identity certificate <NUM>, in addition to, or in place of, the light source angle θo. Examples of the arbitrary parameter indicating the relative positional relationship between the light source <NUM> and the identity certificate <NUM> include at least one of a distance from the identity certificate <NUM> to the light source <NUM>, and an azimuth direction in which the light source <NUM> is positioned relative to the identity certificate <NUM>.

Next, a certificate determination system SYS according to a third example embodiment is described. In the following description, the certificate determination system SYS according to the third example embodiment is referred to as "certificate determination system SYSc". The certificate determination system SYSc according to the third example embodiment is different, compared to the certificate determination system SYSa according to the first example embodiment, in that the certificate determination system SYSc includes a determination server 3c in place of the determination server <NUM>. Other characteristics of the certificate determination system SYSc may be the same as the other characteristics of the certificate determination system SYSa. Accordingly, in the following, a description is given of the determination server 3c in the third example embodiment, focused mainly on differences between the determination server 3c and the determination server <NUM>, with reference to <FIG> is a block diagram illustrating a configuration of the determination server 3c in the third example embodiment.

As illustrated in <FIG>, the determination server 3c is different, compared to the determination server <NUM>, in that a light source control unit 318c, which is one specific example of "control unit", is implemented as a logical processing block in the computation apparatus <NUM>. Other components of the determination server 3c may be the same as the other components of the determination server <NUM>.

The light source control unit 318c is capable of controlling the light source <NUM> through the communication network <NUM>. In the third example embodiment, the light source control unit 318c may control a characteristic (for example, intensity) of the illumination light IL, by controlling the light source <NUM>. For example, the light source control unit 318c may control the characteristic of the illumination light II, in such a manner that a shadow <NUM> appropriately appears in a certificate image <NUM>, compared to the shadow <NUM> before the characteristic of the illumination light II, is controlled. Note that a state where "a shadow <NUM> appropriately appears in a certificate image <NUM>" may refer to, for example, a state where a shadow <NUM> appears in a certificate image <NUM> to such an extent that the image analysis unit <NUM> can appropriately detect the shadow <NUM>. Typically, the state where "a shadow <NUM> appropriately appears in a certificate image <NUM>" may refer to a state where a shadow <NUM> clearly appears in a certificate image <NUM> to such an extent that a contrast between a shadow region <NUM> where the shadow <NUM> appears and an image region other than the shadow region <NUM> is equal to or more than a certain amount.

Such a certificate determination system SYSc according to the third example embodiment can appropriately detect the shadow <NUM> appearing in the certificate image <NUM>, while achieving advantageous effects similar to the above-described advantageous effects that can be achieved by the certificate determination system SYSa according to the first example embodiment.

Claim 1:
A certificate determination apparatus comprising:
a generation unit configured to generate, based on an image in which an identity certificate appears, shadow information related to a shadow of the identity certificate appearing in the image; and
a determination unit configured to determine, based on the shadow information, whether or not the identity certificate appearing in the image is authentic,
wherein the shadow information includes information related to presence or absence of the shadow, characterised in that
the determination unit is configured to determine that the identity certificate is not authentic when the shadow does not appear in the image.