Patent Publication Number: US-2023162491-A1

Title: Processing apparatus, information processing method and recording medium

Description:
TECHNICAL FIELD 
     The present disclosure relates to a technical field of an information processing apparatus, an information processing method and a recording medium that are configured to extract a key point (namely, a feature point) of a target object from an image, for example. 
     BACKGROUND ART 
     A Patent Literature 1 discloses one example of an information processing apparatus that is configured to extract a key point (namely, a feature point) of a target object from an image. 
     Specifically, the Patent Literature 1 discloses a face three dimensional shape estimation apparatus that obtains, from an image in which a target person is included, a face information indicating a position of a feature point of a face of the target person. 
     Additionally, there are Patent Literatures 2 to 6 as a background art document related to the present disclosure. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: WO2020/149001A1 
     Patent Literature 2: WO2019/078310A1 
     Patent Literature 3: JP2017-503276A 
     Patent Literature 4: JP2017-151556A 
     Patent Literature 5: JP2009-529200A 
     Patent Literature 6: JP2005-004781A 
     SUMMARY 
     Technical Problem 
     It is an example object of the present disclosure to provide an information processing system, an information processing method and a recording medium that aims to an improvement of a technique disclosed in the background art document. 
     Solution to Problem 
     One example aspect of an information processing apparatus includes: an extracting unit that extracts a key point of a target object as a target key point from an input image; and a calculating unit that calculates, as a score of the input image from which the target key point is extracted, an index value related to a reliability of the target key point based on the target key point. 
     One example aspect of an information processing method includes: extracting a key point of a target object as a target key point from an input image; and calculating, as a score of the input image from which the target key point is extracted, an index value related to a reliability of the target key point based on the target key point. 
     One example aspect of a recording medium is a recording medium on which a computer program that allows a computer to execute an information processing method is recorded, the information processing method includes: extracting a key point of a target object as a target key point from an input image; and calculating, as a score of the input image from which the target key point is extracted, an index value related to a reliability of the target key point based on the target key point. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a block diagram that illustrates an entire configuration of a key point extraction system in a first example embodiment. 
         FIG.  2    is a block diagram that illustrates a configuration of a key point extraction apparatus in the first example embodiment. 
         FIG.  3    is a flow chart that illustrates a flow of a key point extraction operation that is performed by the key point extraction apparatus in the first example embodiment. 
         FIG.  4    is a planar view that illustrates one example of a key point of an iris that is extracted from a person image. 
         FIG.  5    is a block diagram that illustrates a configuration of a key point extraction apparatus in a second example embodiment. 
         FIG.  6    is a block diagram that illustrates a configuration of a key point extraction apparatus in a third example embodiment. 
         FIG.  7    is a graph that illustrates a relationship between the sampled number of a training image and an image score SC of the training image. 
         FIG.  8    is a block diagram that illustrates a configuration of a key point extraction apparatus in a fourth example embodiment. 
         FIG.  9    illustrates one example of training data. 
         FIG.  10    is a block diagram that illustrates a configuration of a key point extraction apparatus in a fifth example embodiment. 
         FIG.  11    is a block diagram that illustrates a configuration of a key point extraction apparatus in a sixth example embodiment. 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Next, an example embodiment of an information processing apparatus, an information processing method and a recording medium will be described with reference to the drawings. In the below described description, the example embodiment of the information processing apparatus, the information processing method and the recording medium will be described by using a key point extraction system SYS. 
     The key point extraction system SYS is configured to extract a key point KP of a target object from an image. The below described description explains an example in which the key point extraction system SYS is configured to extract the key point KP of a person that is included in a person image IMG 1  from the person image IMG 1  that is generated by capturing an image of the person (namely, a living body) that is one example of the target object. However, the key point extraction system SYS may be configured to extract the key point KP of any target object that is included in an image from the image in which any target object that is different from the person is included. A living body other than a human (for example, at least one of a mammal such as a dog, a cat and so on, a bird such as a sparrow and so on, a reptile such as a snake and so on, an amphibia such as a frog and so on and a fish such as a goldfish and so on) is one example of the target object. An object that is not the living body is another example of the target object. A robot that imitates the human or an animal is one example of the object that is not the living body. 
     Moreover, the below described description explains an example in which the key point extraction system SYS is configured to extract the key point KR of an iris of the person that is included in the person image IMG 1  from the person image IMG 1 . This key point extraction system SYS may be used as an iris authentication system. The iris authentication system is a system that is configured to authenticate the person by using the iris. For example, the iris authentication system extracts a feature amount of the iris of the person that is included in the person image IMG 1  based on the key point KP of the iris. For example, the iris authentication system may determine a loop-shaped iris area in which the iris is included in the person image IMG 1  based on the key point KP of the iris. Specifically, the iris authentication system may determine the iris area based on the key point KP from which an inner outline of the iris is determinable and the key point KP from which an outer outline of the iris is determinable. Furthermore, the iris authentication system may delete an area part that overlaps with an eyelid from the loop-shaped iris area based on the key point KP from which an edge of the eyelid is determinable. Then, the iris authentication system may divide the iris area into a plurality of ring-shaped blocks, divide each block into a plurality of sectors, and extract a feature amount of each sector (for example, a feature amount related to a pattern of the iris included in the plurality of sectors, and a brightness value for example). Then, the iris authentication system may authenticate the person that is included in the person image IMG 1  based on the extracted feature amount of the iris. Incidentally, as can be understandable from the description of the iris authentication system, the present disclosure clearly distinguishes a feature point (namely, the key point KP) from the feature amount of the iris. 
     However, the key point extraction system SYS may be configured to extract the key point KR of any part of the person that is included in the person image IMG 1  from the person image IMG 1 . Apart that is usable for authenticating the person is one example of any part of the person. A face that is usable for a face authentication is another one example of the part that is usable for authenticating the person. A finger on which a fingerprint is formed that is usable for a fingerprint authentication is another one example of the part that is usable for authenticating the person. A hand on which a palm print is formed that is usable for a palm print authentication is another one example of the part that is usable for authenticating the person. A finger in which a pattern of a vein is formed that is usable for a vein authentication is another one example of the part that is usable for authenticating the person. 
     Next, the key point extraction system SYS will be described in more detail with reference to the drawings. 
     (1) Key Point Extraction System SYS in First Example Embodiment 
     Firstly, the key point extraction system SYS in a first example embodiment will be described. Note that the key point extraction system SYS in the first example embodiment is referred to as a “key point extraction system SYSa” in the below described description. 
     (1-1) Entire Configuration of Key Point Extraction System SYSa 
     Firstly, with reference to  FIG.  1   , an entire configuration of the key point extraction system SYSa in the first example embodiment will be described.  FIG.  1    is a block diagram that illustrates the entire configuration of the key point extraction system SYSa in the first example embodiment. 
     As illustrated in  FIG.  1   , the key point extraction system SYSa includes a camera  1  and a key point extraction apparatus  2  that is one specific example of an “information processing apparatus”. The key point extraction system SYSa may include single camera  1  or may include a plurality of cameras  2 . The camera  1  and the key point extraction apparatus  2  are configured to communicate with each other through a communication network  3 . The communication network  3  may include a wired communication network. The communication network  3  may include a wireless communication network. 
     The camera  1  is an imaging apparatus that is configured to capture an image of an imaging target range. The camera  1  includes a processing for generating an image in which the imaging target range is included by capturing the imaging target range. Since the key point extraction system SYSa extracts the key point KP of the iris of the person as described above, the person usually exists in the imaging target range. In this case, the camera  1  generates the person image IMG 1  in which the person is included by capturing the image of the person. Especially, the camera  1  generates the person image IMG 1  in which a face (especially, at least a part of the face including the iris and a part around the iris) of the person is included by capturing the image of the face (especially, at least a part of the face including the iris and a part around the iris) of the person. The camera  1  outputs the generated person image IMG 1  to the key point extraction apparatus  2 . Specifically, the camera  1  transmits the generated person image IMG 1  to the key point extraction apparatus  2  through the communication network  3 . 
     The key point extraction apparatus  2  receives the person image IMG 1  transmitted from the camera  1  through the communication network  3 . The key point extraction apparatus  2  performs a key point extraction operation for extracting the key point KP of the iris of the person that is included in the person image IMG 1  from the received person image IMG 1 . 
     The key point extraction SYSa may include an illumination apparatus  4 . The illumination apparatus  4  is configured to illuminate the imaging target area the image of which is capturable by the camera  1  with an illumination light. When the person exists in the imaging target range, the illumination apparatus  4  may configured to illuminate the person that exists in the imaging target range with the illumination light. In this case, the camera  1  may capture the image of the person that is illuminated by the illumination apparatus  4 . However, the e key point extraction SYSa may not include the illumination apparatus  4 . 
     (1-2) Configuration of Key Point Extraction Apparatus  2   
     Next, with reference to  FIG.  2   , a configuration of the key point extraction apparatus  2  in the first example embodiment will be described.  FIG.  2    is a block diagram that illustrates the configuration of the key point extraction apparatus  2  in the first example embodiment. 
     As illustrated in  FIG.  2   , the key point extraction apparatus  2  includes an arithmetic apparatus  21 , a storage apparatus  22  and a communication apparatus  23 . Furthermore, the key point extraction apparatus  2  may include an input apparatus  24  and an output apparatus  25 . However, the key point extraction apparatus  2  may not include at least one of the input apparatus  24  and the output apparatus  25 . The arithmetic apparatus  21 , the storage apparatus  22 , the communication apparatus  23 , the input apparatus  24  and the output apparatus  25  may be interconnected through a data bus  26 . 
     The arithmetic apparatus  21  includes at least one of a CPU (Central Processing Unit), a GPU (Graphic Processing Unit) and a FPGA (Field Programmable Gate Array), for example. The arithmetic apparatus  21  reads a computer program. For example, the arithmetic apparatus  21  may read a computer program that is stored in the storage apparatus  22 . For example, the arithmetic apparatus  21  may read a computer program that is stored in a non-transitory computer-readable recording medium by using a non-illustrated recording medium reading apparatus of the key point extraction apparatus  2 . The arithmetic apparatus  21  may obtain (namely, download or read) a computer program from a non-illustrated apparatus that is placed outside the key point extraction apparatus  2  through the communication apparatus  23  (alternatively, other communication apparatus) The arithmetic apparatus  21  executes the read computer program. As a result, a logical functional block for performing an operation (for example, the above described key point extraction operation) that should be performed by the key point extraction apparatus  2  is implemented in the arithmetic apparatus  21 . Namely, the arithmetic apparatus  21  is configured to serve as a controller for implementing the logical functional block for performing the operation (in other words, a processing) that should be performed by the key point extraction apparatus  2 . 
       FIG.  2    illustrates one example of the logical functional block that is implemented in the arithmetic apparatus  21  for performing the key point extraction operation. As illustrated in  FIG.  2   , in the arithmetic apparatus  21 , an image conversion unit  211  that is one specific example of “an image converting unit”, a key point extraction unit  212  that is one specific example of “an extracting unit” and a score calculation unit  213  that is one specific example of “a calculating unit” are implemented. Note that a detail of an operation of each of the image conversion unit  211 , the key point extraction unit  212  and the score calculation unit  213  will be described later in detail, however, a summary thereof will be described briefly here. The image conversion unit  211  is configured to generate a conversion image IMG 2  by performing an image conversion processing that converts the person image IMG 1 . The key point extracting unit  212  is configured to extract the key point KP of the target object (the iris in the first example embodiment) that is included in the person image IMG 1  from the person image IMG 1 . Furthermore, the key point extracting unit  212  is configured to extract the key point KP of the target object (the iris in the first example embodiment) that is included in the conversion image IMG 2  from the conversion image IMG 2 . 
     Note that the key point KP that is extracted from the person image IMG 1  is referred to as the “key point KP 1 ” and the key point KP that is extracted from the conversion image IMG 2  is referred to as the “key point KP 2 ” to distinguish both in the below described description. The key point KP 1  is one specific example of a “target key point” and the key point KP 2  is one specific example of a “conversion key point”. The score calculation unit  213  is configured to calculate, as a score of the person image IMG 1  (hereinafter, it is referred to as an “image score SC”), an index value related to a reliability of the key point KP 1  extracted from the person image IMG 1  based on the key point KP 1  and the key point KP 2 . Note that the “reliability” in the present example embodiment is an index value for evaluating an error (a difference) between the key point KP 1  that is actually extracted from the person image IMG 1  by the key point extraction unit  212  and the key point KP 1  that should be extracted from the person image IMG 1  by the key point extraction unit  212  (namely, a ground truth value of the key point KP 1 ). Typically, the key point KP 1  that is actually extracted from the person image IMG 1  by the key point extraction unit  212  is more reliable (namely, it is usable without problem as the key point KP 1  that should be extracted from the person image IMG 1  by the key point extraction unit  212 ) as the error becomes smaller. Thus, typically, the reliability becomes higher as the error becomes smaller. 
     The storage apparatus  22  is configured to store a desired data. For example, the storage apparatus  22  may temporarily store the computer program that is executed by the arithmetic apparatus  21 . The storage apparatus  22  may temporarily store a data that is temporarily used by the arithmetic apparatus  21  when the arithmetic apparatus  21  executes the computer program. The storage apparatus  22  may store a data that is stored for a long term by the key point extraction apparatus  2 . Note that the storage apparatus  22  may include at least one of a RAM (Random Access Memory), a ROM (Read Only Memory), a hard disk apparatus, a magneto-optical disc, a SSD (Solid State Drive) and a disk array apparatus. Namely, the storage apparatus  22  may include a non-transitory recording medium. 
     The communication apparatus  23  is configured to communicate with the camera  1  through the communication network  3 . In the first example embodiment, the communication apparatus  23  receives the person image IMG 1  from the camera  1  through the communication network  3 . 
     The input apparatus  24  is an apparatus that receives an input of an information from an outside of the key point extraction apparatus  2  to the key point extraction apparatus  2 . For example, the input apparatus  24  may include an operational apparatus (for example, at least one of a keyboard, a mouse and a touch panel) that is operable by an operator of the key point extraction apparatus  2 . For example, the input apparatus  24  may include a reading apparatus that is configured to read an information recorded as a data in a recording medium that is attachable to the key point extraction apparatus  2 . 
     The output apparatus  25  is an apparatus that outputs an information to an outside of the key point extraction apparatus  2 . For example, the output apparatus  25  may output the information as an image. Namely, the output apparatus  25  may include a display apparatus (what we call a display) that is configured to display the image representing the information to be outputted. For example, the output apparatus  25  may output the information as a sound. Namely, the output apparatus  25  may include an audio apparatus (what we call a speaker) that is configured to output the sound. For example, the output apparatus  25  may output the information on a paper. Namely, the output apparatus  25  may include a print apparatus (what we call a printer) that is configured to print a desired information on the paper. 
     (1-3) Flow of Key Point Extraction Operation Performed by Key Point Extraction Apparatus  2   
     Next, with reference to  FIG.  3   , a flow of the key point extraction operation that is performed by the key point extraction apparatus  2  in the first example embodiment will be described.  FIG.  3    is a flowchart that illustrates the flow of the key point extraction operation that is performed by the key point extraction apparatus  2  in the first example embodiment. 
     As illustrated in  FIG.  3   , the key point extraction apparatus  2  obtains the person image IMG 1  from the camera  1  (a step S 11 ). Specifically, the key point extraction apparatus  2  receives the person image IMG 1 , which is transmitted to the key point extraction apparatus  2  by the camera  1 , by using the communication apparatus  23  through the communication network  3 . 
     Then, the key point extraction unit  212  extracts the key point KP (namely, the key point KP 1 ) of the iris that is included in the person image IMG 1  from the person image IMG 1  obtained at the step S 11  (a step S 12 ). 
     The key point KP may include a key point KP that corresponds to a point from which a characteristic part of the target object is determinable. Thus, the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP that corresponds to a point from which a characteristic part of the iris is determinable. For example, as illustrated in  FIG.  4    that illustrates one example of the key point KP of the iris extracted from the person image IMG 1 , the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP# 1  that corresponds to a point from which an inner outline of the iris (namely, substantially, an outline of a pupil) is determinable. The key point KP# 1  may be a point that is located on the inner outline of the iris. For example, as illustrated in  FIG.  4   , the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP# 2  that corresponds to a point from which an outer outline of the iris is determinable. The key point KP# 2  may be a point that is located on the outer outline of the iris. For example, as illustrated in  FIG.  4   , the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP# 3  that corresponds to a point from which a center of the iris is determinable. The key point KP# 3  may be a point that is located on the center of the iris. Note that the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP that corresponds to a point from which a center of the pupil, which is located on the center of the iris, is determinable, in addition to or instead of the key point KP# 3  that corresponds to the point from which the center of the iris is determinable. For example, as illustrated in  FIG.  4   , the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP# 4  that corresponds to a point from which an edge of an eyelid that is likely to hide the iris partially is determinable. The key point KP# 4  may be a point that is located on the edge of the eyelid. For example, as illustrated in  FIG.  4   , the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP# 5  that corresponds to a point from which an eye including the iris is determinable. As one example, the key point extraction unit  212  may extract, as the key point KP# 5 , at least one of a key point KP# 5 - 1  that corresponds to a point from which an inner corner of the eye is determinable and a key point KP# 5 - 2  that corresponds to a point from which an outer corner of the eye is determinable. 
     The key point KP may include a key point KP that corresponds to a line from which the characteristic part of the target object is determinable in addition to or instead of the key point KP that corresponds to the point from which the characteristic part of the target object is determinable. 
     Thus, the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP that corresponds to a line from which the characteristic part of the iris is determinable. For example, the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP that corresponds to a line from which the inner outline of the iris is determinable (for example, a line that extends along the inner outline of the iris). For example, the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP that corresponds to a line from which the outer outline of the iris is determinable (for example, a line that extends along the outer outline of the iris). For example, the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP that corresponds to a line from which the edge of the eyelid is determinable (for example, a line that extends along the edge of the eyelid). For example, the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP that corresponds to a line that connects the outer corner of the eye and the inner corner of the eye. 
     At least one of the point and the line that is extracted as the key point KP may be usable to quantitatively determine the target object. Thus, the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP that corresponds to at least one of the point and the line that is usable to quantitatively determine the iris. For example, the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP that corresponds to a line that is usable to determine a size of the iris. As one example, when a shape of the iris is a circular shape, the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP that corresponds to a line that is usable to determine a radius (for example, a diameter) of the iris that is one example of the size of the iris (for example, a line that passes through the center of the iris and both edges of which exist on the outer outline of the iris). As another example, when the shape of the iris is an oval shape, the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP that corresponds to a line that is usable to determine at least one of a major diameter and a minor diameter of the iris that are examples of the size of the iris. The line that is usable to determine the major diameter of the iris may include a line that indicates a major axis of the iris, for example. The line that is usable to determine the minor diameter of the iris may include a line that indicates a minor axis of the iris, for example. For example, the key point extraction unit  212  may extract, as the key point KP of the iris, a key point KP that corresponds to a line that is usable to determine a size (for example, a diameter) of the pupil that is located on the center of the iris. 
     The key point extraction unit  212  may extract the key point KP by using a neural network. Specifically, the key point extraction unit  212  may extract the key point KP by using a neural network that is configured to output the key point KP of the iris included in the person image IMG 1  (alternatively, any image including the conversion image IMG 2 ) when the person image IMG 1  (alternatively, any image including the conversion image IMG 2 ) is inputted thereto. It is preferable that a parameter of the neural network be learned (trained) by using a training data that includes a training image for learning the parameter of the neural network and a ground truth label of the key point KP of the iris included in the training image (namely, a ground truth key point that is the key point KP that should be extracted from the training image). Note that the neural network is one example of a trainable learning model. Thus, the key point extraction unit  212  may extract the key point KP by using any learning model that is different from the neural network. 
     An operation for extracting the key point KP may mean an operation for determining a position of the key point KP in the person image IMG 1  (for example, a position of the key point KP in the person image IMG 1  along each of a height direction and a width direction). In this case, the key point extraction unit  212  may determine the position of the key point KP in the person image IMG 1 . When the key point KP is extracted by using the neural network as described above, the neural network may output the position of the key point KP in the person image IMG 1 . 
     Note that the person (especially, the iris thereof) is not always included properly in the person image IMG 1  that is generated by the camera  1 . In this case, the key point extraction unit  212  may not extract at least one of a plurality of types of key points KP the examples of which are described by using  FIG.  4   . Namely, the key point extraction unit  212  may not necessarily extract all of a plurality of types of key points KP. The key point extraction unit  212  may extract at least one key point KP that is extractable from the person image IMG 1 . The key point extraction unit  212  may not extract at least one key point KP that is not extractable from the person image IMG 1 . Thus, there is a possibility that the key point extraction unit  212  extracts no key point KP. Furthermore, when the person (especially, the iris thereof) is not included in the person image IMG 1 , the key point extraction unit  212  may extract no key point KP. Namely, the person (especially, the iris thereof) may not be necessarily included in the person image IMG 1  that is inputted to the key point extraction unit  212 . 
     Again in  FIG.  3   , in parallel with, after or before the operation at the step S 12 , the image conversion unit  211  performs the image conversion processing that convers the person image IMG 1  obtained at the step S 11  (a step S 13 ). As a result, the image conversion unit  211  generates the conversion image IMG 2  that is the person image IMG 1  on which the image conversion processing has been performed (the step S 13 ). 
     The image conversion processing at the step S 13  may include a processing for performing a geometric transformation (in other words, a linear transformation) on the person image IMG 1 . Namely, the image conversion unit  211  may performs the geometric transformation on the person image IMG 1 . 
     An affine transformation is one example of the geometric transformation. Namely, the image conversion processing at the step S 13  may include a processing for performing the affine transformation on the person image IMG 1 . The affine transformation may include a translation. Namely, the image conversion processing at the step S 13  may include a translation processing for translating the person image IMG 1  along at least one of the height direction and the width direction. The affine transformation may include a rotation. Namely, the image conversion processing at the step S 13  may include a rotation processing for rotating the person image IMG 1 . The affine transformation may include a scaling. Namely, the image conversion processing at the step S 13  may include a scaling processing for scaling the person image IMG 1 . The affine transformation may include a shear. Namely, the image conversion processing at the step S 13  may include a shear processing for shearing the person image IMG 1 . 
     A flip transform is another example of the geometric transformation. Namely, the image conversion processing at the step S 13  may include a processing for performing the flipping transformation on the person image IMG 1 . For example, the image conversion processing at the step S 13  may include a processing for flipping the person image IMG 1  horizontally (in other words, flipping it along the width direction (a horizontal direction). Namely, the image conversion processing at the step S 13  may include a processing for generating, as the conversion image IMG 2 , an image that is linearly symmetric with the person image IMG 1  with respect to an axis of symmetry that is along the height direction (a vertical direction). For example, the image conversion processing at the step S 13  may include a processing for flipping the person image IMG 1  vertically (in other words, flipping it along the height direction (the vertical direction). Namely, the image conversion processing at the step S 13  may include a processing for generating, as the conversion image IMG 2 , an image that is linearly symmetric with the person image IMG 1  with respect to an axis of symmetry that is along the width direction (the horizontal direction). 
     The image conversion processing at the step S 13  may include a processing for changing a characteristic of at least a part of the person image IMG 1 . The characteristic of the person image IMG 1  may include a brightness (namely, a brightness) of the person image IMG 1 . In this case, the image conversion processing at the step S 13  may include a processing for changing the brightness of at least a part of the person image IMG 1 . Especially, the image conversion processing at the step S 13  may include a processing for changing the brightness of at least one of an image part of the person image IMG 1  that corresponds to the iris and an image part of the person image IMG 1  that corresponds to a part around the iris. The characteristic of the person image IMG 1  may include a contrast (namely, a ratio of the brightness) of the person image IMG 1  in addition to or instead of the brightness of the person image IMG 1 . In this case, the image conversion processing at the step S 13  may include a processing for changing the contrast of at least a part of the person image IMG 1 . Especially, the image conversion processing at the step S 13  may include a processing for changing the contrast of at least one of the image part of the person image IMG 1  that corresponds to the iris and the image part of the person image IMG 1  that corresponds to a part around the iris. 
     At the step S 13 , the image conversion unit  211  may generate a single conversion image IMG 2 . Alternatively, at the step S 13 , the image conversion unit  211  may generate a plurality of conversion images IMG 2 . The plurality of conversion images IMG 2  may be generated by a plurality of different image conversion processing. For example, the image conversion unit  211  may generate a first conversion image IMG 2  by translating the person image IMG 1 , generate a second conversion image IMG 2  by rotating the person image IMG 1 , generate a third conversion image IMG 2  by scaling the person image IMG 1 , generate a fourth conversion image IMG 2  by inverting the person image IMG 1 , generate a fifth conversion image IMG 2  by changing the brightness of the person image IMG 1 , and generate a sixth conversion image IMG 2  by changing the contrast of the person image IMG 1 . 
     Then, the key point extraction unit  212  extracts the key point KP (namely, the key point KP 2 ) of the iris that is included in the conversion image IMG 2  from the conversion image IMG 2  generated at the step S 13  (a step S 14 ). Note that an operation for extracting the key point KP 2  at the step S 14  may be same as the operation for extracting the key point KP 1  at the step S 12 . Thus, a detailed description of the operation for extracting the key point KP 2  at the step S 14  is omitted. 
     When the plurality of conversion images IMG 2  are generated at the step S 13 , the key point extraction unit  212  may extract the key point KP 2  from each of the plurality of conversion images IMG 2 . For example, when the mage conversion unit  211  generates the first conversion image IMG 2  to the sixth conversion image IMG 2  as described above, the key point extracting unit  212  may extract a first key point KP 2  from the first conversion image IMG 2 , extract a second key point KP 2  from the second conversion image IMG 2 , extract a third key point KP 2  from the third conversion image IMG 2 , extract a fourth key point KP 2  from the fourth conversion image IMG 2 , extract a fifth key point KP 2  from the fifth conversion image IMG 2 , and extract a sixth key point KP 2  from the sixth conversion image IMG 2 . 
     Then, the score calculation unit  213  calculates the image score SC of the person image IMG 1  (a step S 15 ). Note that the image score SC of the person image IMG 1  is the index value related to the reliability of the key point KP 1  extracted from the person image IMG 1  as described above. Next, the image score SC will be described. 
     A quality of the person image IMG 1  from which the key point extraction unit  212  extracts the key point KP 1  is not always constant. For example, there is a possibility that the quality of the person image IMG 1  that is inputted to the key point extraction unit  212  at one timing is relatively high and the quality of the person image IMG 1  that is inputted to the key point extraction unit  212  at another timing that is different from one timing is relatively low. The higher the quality of the person image IMG 1  is, the higher the possibility that the key point extraction unit  212  is capable of reliably extracting the key point KP 1  that should be extracted is. Moreover, the higher the quality of the person image IMG 1  is, the higher the possibility that the key point extraction unit  212  is capable of extracting the key point KP 1  that should be extracted is with high accuracy. Note that an accuracy of the key point KP 1  here is an index value for quantitatively evaluating a difference between the position of the key point KP 1  extracted by the key point extraction unit  212  and an actual position of the key point KP 1 . The smaller the difference between the position of the key point KP 1  extracted by the key point extraction unit  212  and the actual position of the key point KP 1  is, the higher the key point KP 1  extracted by the key point extraction unit  212  is. Thus, there is a high possibility that the accuracy of the key point KP 1  extracted by the key point extraction unit  212  becomes lower as the quality of the person image IMG 1  inputted to the key point extracting unit  212  is lower. Namely, there is a high possibility that the position of the key point KP 1  extracted by the key point extraction unit  212  is farther from the real position of the key point KP 1  as the quality of the person image IMG 1  inputted to the key point extracting unit  212  is lower. Furthermore, in some cases, the lower the quality of the person image IMG 1  inputted to the key point extracting unit  212  is, the higher the possibility that the key point extraction unit  212  is not capable of extracting the key point KP 1  that should be extracted. Thus, it is estimated that the reliability of the key point KP 1  extracted by the key point extraction unit  212  is lower as the quality of the person image IMG 1  inputted to the key point extracting unit  212  is lower. From this viewpoint, the score calculation unit  213  calculates, as the image score SC that allows the quality of the person image IMG 1  to be evaluated quantitatively, the index value related to the reliability of the key point KP 1  extracted from the person image IMG 1 . 
     It can be said that the person image IMG 1  from which the key point extracting unit  212  has difficulty extracting the key point KP 1  is the person image IMG 1  that is incompatible to the key point extraction unit  212 . Similarly, it can be said that the person image IMG 1  from which the key point extracting unit  212  is not capable of extracting the key point KP 1  with high accuracy is the person image IMG 1  that is incompatible to the key point extraction unit  212 . Thus, the image score SC may be regarded to be an index value for quantitatively evaluating a compatibility of the person image IMG 1  to the key point extracting unit  212 . Note that the compatibility of the person image IMG 1  to the key point extracting unit  212  may mean an easiness of the extraction of the key point KP 1  (especially, an easiness of the extraction of the accurate key point KP 1 ) from the person image IMG 1  by the key point extraction unit  212 . 
     When the key point extraction unit  212  extracts the key point KP 1  by using the trainable neural network (alternatively, any trainable learning model) as described above, it can be said that the person image IMG 1  from which the key point extracting unit  212  has difficulty extracting the key point KP 1  is the person image IMG 1  that is not sufficiently learned by the learning model. 
     Similarly, it can be said that the person image IMG 1  from which the key point extracting unit  212  is not capable of extracting the key point KP 1  with high accuracy is the person image IMG 1  that is not sufficiently learned by the learning model. Thus, the image score SC may be regarded to be an index value for quantitatively evaluating a degree of shortage of the learning of the person image IMG 1  by the learning model (namely, a degree of shortage of the learning of the person image IMG 1  by the key point extraction unit  212 ). 
     There is a possibility that the quality of the person image IMG 1  is affected by a state of an object (in this case, the person) included in the person image IMG 1 . Thus, the image score SC may be regarded to be an index value for quantitatively evaluating the state of the object (in this case, the person) included in the person image IMG 1 . For example, presence or absence of glasses is one example of the state of the person included in the person image IMG 1 . Specifically, when the person included in the person image IMG 1  does not wear the glasses, the illumination light from the illumination apparatus  4  is not reflected by the glasses. Thus, the camera  1  is capable of capturing the image of the eye (especially, the iris) of the person without being affected by a reflection light of the illumination light by the glasses. Namely, the eye (especially, the iris) of the person is included in the person image IMG 1  properly. In this case, there is a relatively high possibility that the key point extraction unit  212  is capable of extracting the key point KP 1  of the iris from the person image IMG 1  with relatively high accuracy. On the other hand, when the person included in the person image IMG 1  wears the glasses, there is a possibility that the illumination light from the illumination apparatus  4  is reflected by the glasses. Thus, there is a possibility that the camera  1  is affected by the reflection light of the illumination light by the glasses. Namely, there is a possibility that the eye (especially, the iris) of the person is not included in the person image IMG 1  properly. For example, there is a possibility that a part of the eye (especially, the iris) of the person that should exists in the rear of a lens of the glasses is hidden by an image of the reflection light on the lens of the glasses in the person image IMG 1 . In this case, there is a possibility that the key point extraction unit  212  is not capable of extracting the key point KP 1  of the iris from the person image IMG 1  with high accuracy. Thus, the score calculation unit  213  may calculate the image score SC so that the image score SC of the person image IMG 1  including the person that wears the glasses is worse than the image score SC of the person image IMG 1  including the person that does not wear the glasses. However, in the first example embodiment, the score calculation unit  213  calculates the image score SC based on the key point KP extracted by the key point extraction unit  212  without directly determining whether or not the person that wears the glasses is included in the person image IMG 1 , as described later. However, the score calculation unit  213  may calculate the image score SC by directly determining whether or not the person that wears the glasses is included in the person image IMG 1 . 
     On the other hand, even when the person included in the person image IMG 1  wears the glasses, there is a possibility that the key point extraction unit  212  is capable of extracting the key point KP 1  of the iris from the person image IMG 1  with relatively high accuracy, depending on an illumination condition of the illumination light from the illumination apparatus  4 . Specifically, there is a possibility that the key point extraction unit  212  is capable of extracting the key point KP 1  of the iris from the person image IMG 1 , which is generated by capturing the image of the person in a situation where the illumination condition is a first condition, with relatively high accuracy and is not capable of extracting the key point KP 1  of the iris from the person image IMG 1 , which is generated by capturing the image of the person in a situation where the illumination condition is a second condition that is different from the first condition, with relatively high accuracy. Namely, there is a possibility that the quality of the person image IMG 1  is affected by the illumination condition that affects the state of the object (in this case, the person) included in the person image IMG 1 . Thus, the image score SC may be regarded to be an index value for quantitatively evaluating the illumination condition. Conversely, the score calculating unit  213  may calculate the image score SC that varies depending on the illumination condition. However, in the first example embodiment, the score calculation unit  213  calculates the image score SC based on the key point KP extracted by the key point extraction unit  212  without directly using the illumination condition, as described later. However, the score calculation unit  213  may calculate the image score SC based on the illumination condition. 
     At the step S 15 , the score calculation unit  123  calculates the image score SC of the person image IMG 1  based on the key point KP 1  extracted at the step S 12  and the key point KP 2  extracted at the step S 14 . Here, when the quality of the person image IMG 1  is relatively high, the key point extraction unit  212  is capable of extracting the key point KP 1  with relatively high accuracy as described above. Thus, a difference between the key point KP 1  extracted from the person image IMG 1  by the key point extraction unit  212  and the actual key point KP 1  is relatively small. Furthermore, a difference between the key point KP 2  extracted from the person image IMG 2 , which is generated by performing the image conversion processing on the person image IMG 1 , by the key point extraction unit  212  and an actual key point KP 2  is also relatively small. Therefore, when the quality of the person image IMG 1  is relatively high, it is estimated that a difference between the key point KP 1  and the key point KP 2  (namely, a difference between the position of the key point KP 1  and the position of the key point KP 2 ) is relatively small. On the other hand, when the quality of the person image IMG 1  is relatively low, there is a possibility that the key point extraction unit  212  is not capable of extracting the key point KP 1  with relatively high accuracy. Thus, it is estimated that the difference between the key point KP 1  and the key point KP 2  is relatively large. This is because there is a possibility that the difference between the key point KP 1  extracted by the key point extraction unit  212  and the actual key point KP 1  is different from the difference between the key point KP 2  extracted by the key point extraction unit  212  and the actual key point KP 2  because there is a possibility that the key point extraction unit  212  is not capable of extracting the key point KP 1  (furthermore, the key point KP 2 ) with relatively high accuracy. 
     Thus, it is estimated that the difference (namely, a margin) between the key point KP 1  and the key point KP 2  includes an information related to the quality of the person image IMG 1 . Therefore, the score calculation unit  213  may compare the key point KP 1  and the key point KP 2  and calculate the image score SC based on a comparison result of the key point KP 1  and the key point KP 2 . 
     When the key point extraction unit  212  extracts the plurality of types of key points KP as illustrated in  FIG.  4   , the score calculation unit  213  may compare the key point KP 1  and the key point KP 2  for each type of the key point KP. For example, the score calculation unit  213  may compare a first type of key point KP 1  and the same first type of key point KP 2 , compare a second type of key point KP 1  and the same second type of key point KP 2 , . . . , and compare a n-th (n is a variable number indicating an integer that is equal to or larger than 2) type of key point KP 1  and the same n-th type of key point KP 2 . As one example, the score calculation unit  213  may compare the key point KP 1  from which the inner outline of the iris is determinable and the key point KP 2  from which the inner outline of the same iris is determinable, compare the key point KP 1  from which the outer outline of the iris is determinable and the key point KP 2  from which the inner outline of the same iris is determinable, and compare the key point KP 1  from which the center of the iris is determinable and the key point KP 2  from which the center of the same iris is determinable. In this case, the when the key point extraction unit  212  extracts then types of key points KP, the score calculation unit  213  may compare the key point KP 1  and the key point KP 2  for all of the n types of key points KP. Alternatively, the score calculation unit  213  may compare the key point KP 1  and the key point KP 2  for a part of the n types of key points KP and may not compare the key point KP 1  and the key point KP 2  for another part of the n types of key points KP. Then, the score calculation unit  213  may calculate the image score SC based on a plurality of comparison results that correspond to the plurality of types of key points KP, respectively. For example, the score calculation unit  213  may calculate the image score SC based on a mean value (for example, a simple mean value or a square mean value) of the plurality of comparison results. The score calculation unit  213  may calculate the image score SC based on a total sum (for example, a simple total sum or a square total sum) of the plurality of comparison results. 
     When the plurality of conversion images IMG 2  are generated at the step S 13  and the plurality of key points KP 2  are extracted from the plurality of conversion images IMG 2 , respectively, at the step S 14 , the score calculation unit  213  may compare the key point KP 1  and the plurality of key points KP 2 . For example, when the key point extraction unit  212  extracts the first key point KP 2  to the sixth key point KP 2  from the first conversion image IMG 2  to the sixth conversion image IMG 2 , respectively, as described above, the score calculation unit  213  may compare the key point KP 1  and the first key point KP 2 , compare the key point KP 1  and the second key point KP 2 , compare the key point KP 1  and the third key point KP 2 , compare the key point KP 1  and the fourth key point KP 2 , compare the key point KP 1  and the fifth key point KP 2 , and compare the key point KP 1  and the sixth key point KP 2 . Then, the score calculation unit  213  may calculate the image score SC based on a plurality of comparison results that correspond to the plurality of key points KP 2 , respectively. For example, the score calculation unit  213  may calculate the image score SC based on a mean value (for example, a simple mean value or a square mean value) of the plurality of comparison results. The score calculation unit  213  may calculate the image score SC based on a total sum (for example, a simple total sum or a square total sum) of the plurality of comparison results. 
     The score calculation unit  213  may calculate the difference between the key point KP 1  and the key point KP 2  by comparing the key point KP 1  and the key point KP 2 . In this case, the score calculation unit  213  may calculate the image score SC based on the difference that corresponds to the comparison result. For example, the score calculation unit  213  may calculate the image score SC so that the image score SC becomes worse as the difference becomes larger. In other words, the score calculation unit  213  may calculate the image score SC so that the image score SC becomes better as the difference becomes smaller. As one example, the score calculation unit  213  may calculate the image score SC that becomes larger as the difference becomes larger. In this case, it can be said that the quality of the person image IMG 1  is worse (in other words, the reliability of the extracted key point KP 1  is lower) as the image score SC becomes larger. As another example, the score calculation unit  213  may calculate the image score SC that becomes smaller as the difference becomes larger. In this case, it can be said that the quality of the person image IMG 1  is better (in other words, the reliability of the extracted key point KP 1  is higher) as the image score SC becomes larger. 
     The key point extraction unit  212  determines the position of the key point KP when it extracts the key point KP as described above. since the position of the key point KP is determined, the score calculation unit  213  may calculate a distance between the key point KP 1  and the key point KP 2  as the difference between the key point KP 1  and the key point KP 2 . 
     However, the position of the key point KP 1  is determined as a position in the person image IMG 1  and the position of the key point KP 2  is determined as a position in the conversion image IMG 2 . Thus, a coordinate system for determining the position of the key point KP 1  (namely, a coordinate system in the person image IMG 1 ) is not always same as a coordinate system for determining the position of the key point KP 2  (namely, a coordinate system in the conversion image IMG 2 ). On the other hand, the key point extraction apparatus  2  is capable of converting a position of either one of the first coordinate system and the second coordinate system to a position of the other one of the first coordinate system and the second coordinate system, because the key point extraction  2  itself generates the conversion image IMG 2  by performing the image conversion processing on the person image IMG 1 . Thus, the score calculation unit  213  may convert the key point KP 2  in the second coordinate system extracted at the step S 14  to the key point KP 2  in the first coordinate system before calculating the image score SC. Namely, the score calculation unit  213  may convert the position of the key point KP 2  in the second coordinate system extracted at the step S 14  to the position of the key point KP 2  in the first coordinate system before calculating the image score SC. Then, the score calculation unit  213  may calculate the image score SC based on the key point KP 1  in the first coordinate system and the key point KP 2  in the first coordinate system. For example, the score calculation unit  213  may calculate the difference between the key point KP 1  and the key point KP 2  in the first coordinate system and calculate the image score SC based on the difference. 
     As described above, when there is a possibility that the key point extraction unit  212  is not capable of extracting the key point KP with relatively high accuracy, there is a possibility that a variation of the extracted key point KP becomes large depending on a situation where the key point KP is extracted. Thus, the score calculation unit  213  may calculate a standard deviation of the key point KP (in other words, a variation (in other words, a degree of dispersion) of the key point KP 1  and the key point KP 2 )) by comparing the key point KP 1  and the key point KP 2 , and calculate the image score SC based on the standard deviation that corresponds to the comparison result. In this case, the score calculation unit  213  may calculate the image score SC so that the image score SC becomes worse as the standard deviation becomes larger. In other words, the score calculation unit  213  may calculate the image score SC so that the image score SC becomes better as the standard deviation becomes smaller. As one example, the score calculation unit  213  may calculate the image score SC that becomes larger as the standard deviation becomes larger. In this case, it can be said that the quality of the person image IMG 1  is worse (in other words, the reliability of the extracted key point KP 1  is lower) as the image score SC becomes larger. As another example, the score calculation unit  213  may calculate the image score SC that becomes smaller as the standard deviation becomes larger. In this case, it can be said that the quality of the person image IMG 1  is better (in other words, the reliability of the extracted key point KP 1  is higher) as the image score SC becomes larger. 
     The score calculation unit  213  may calculate the standard deviation of the key point KP when the key point extraction unit  212  extracts the plurality of key points KP 2  from the plurality of conversion images IMG 2 , respectively. This is because a reliability of the standard deviation becomes lower when the number of sample in a general population (namely, a total number of the key point KP 1  and the key point KP 2  that are used to calculate the standard deviation) is excessively small. 
     (1-4) Technical Effect of Key Point Extraction Apparatus  2   
     As described above, the key point extraction apparatus  2  in the first example embodiment is capable of calculating the image score SC. The image score SC is the index value related to the reliability of the key point KP 1  extracted from the person image IMG 1  and index value that is capable of quantitatively evaluating the quality of the person image IMG 1 . Thus, the key point extraction apparatus  2  is capable of taking various countermeasures by using the image score SC so that the key point extraction apparatus  2  is capable of extracting the key point KP 1  from the person image IMG 1  with high accuracy. 
     For example, there is a possibility that the person image IMG 1  from which the relatively bad image score SC is calculated is an image the quality of which is so bad that the key point extraction unit  212  is not capable of extracting the key point KP 1  with high accuracy therefrom (namely, it is evaluated that the reliability of the extracted key point KP 1  is relatively low). Thus, when the relatively bad image score SC is calculated, it is expected that a necessity for improving the quality of the person image IMG 1  is relatively high. Therefore, in this case, the key point extraction apparatus  2  may take a countermeasure for improving the quality of the person image IMG 1 . Note that changing the illumination condition of the illumination light by the illumination apparatus  4  is one example of the countermeasure for improving the quality of the person image IMG 1 , however, this countermeasure will be described in a second example embodiment described later. 
     For example, there is a possibility that the person image IMG 1  from which the relatively bad image score SC is calculated is an image that is not sufficiently learned by the key point extraction unit  212  to allow the key point extraction unit  212  not to be capable of extracting the key point KP 1  with high accuracy therefrom (namely, it is evaluated that the reliability of the extracted key point KP 1  is relatively low). Thus, when the relatively bad image score SC is calculated, it is expected that a necessity for performing the training of the key point extraction unit  212  (specifically, the training of the above described learning model) by using the person image IMG 1  having the relatively bad image score SC. Therefore, the key point extraction apparatus  2  is capable of performing the training of the key point extraction unit  212  by using the person image IMG 1  the image score SC of which is relatively bad. 
     Moreover, in the first example embodiment, the key point extraction apparatus  2  is configured to calculate the image score SC by comparing the key point KP 1  that is extracted from the person image IMG 1  and the key point KP 2  that is extracted from the conversion image IMG 2  that is generated by performing the image conversion processing on the person image IMG 1 . As described above, the difference between the key point KP 1  and the key point KP 2  is relatively small when the quality of the person image IMG 1  is relatively high, and the difference between the key point KP 1  and the key point KP 2  is relatively large when the quality of the person image IMG 1  is relatively low. Thus, the key point extraction apparatus  2  is capable of calculating the image score SC properly by comparing the key point KP 1  and the key point KP 2 . 
     (1-5) Modified Example of Key Point Extraction Apparatus  2   
     In the above described description, the key point extraction apparatus  2  includes the single key point extraction unit  212  that is configured to extract the key point KP from the person image IMG 1  and that is configured to extract the key point KP from the conversion image IMG 2 . However, the key point extraction apparatus  2  may include a key point extraction unit that is configured to extract the key point KP from the person image IMG 1  and a key point extraction unit that is configured to extract the key point KP from the conversion image IMG 2  separately. 
     (2) Key Point Extraction System SYS in Second Example Embodiment 
     Next, the key point extraction system SYS in a second example embodiment will be described. Note that the key point extraction system SYS in the second example embodiment is referred to as a “key point extraction system SYSb” in the below described description. 
     The key point extraction system SYSb in the second example embodiment is different from the above described key point extraction system SYSa in the first example embodiment in that it includes a key point extraction apparatus  2   b  instead of the key point extraction apparatus  2 . Another feature of the key point extraction system SYSb may be same as another feature of the key point extraction system SYSa. Thus, in the below describe description, with reference to  FIG.  5   , the key point extraction apparatus  2   b  in the second example embodiment will be described.  FIG.  5    is a block diagram that illustrates the configuration of the key point extraction apparatus  2   b  in the second example embodiment. Note that a detailed description of the component that is already described is omitted by assigning the same reference number thereto. Moreover, a detailed description of a process that is already described is omitted by assigning the same step number thereto. 
     As illustrated in  FIG.  5   , the key point extraction apparatus  2   b  in the second example embodiment is different from the key point extraction apparatus  2  in the first example embodiment in that an illumination control unit  214   b  that is one specific example of an “illumination controlling unit” is implemented in the arithmetic apparatus  21 . Another feature of the key point extraction apparatus  2   b  may be same as another feature of the key point extraction apparatus  2 . 
     The illumination control unit  214   b  is configured to control the illumination apparatus  4 . Specifically, the illumination control unit  214   b  is configured to control (specifically, configured to change) the illumination condition of the illumination light by the illumination apparatus  4  by controlling the illumination apparatus  4 . The illumination condition may include a condition of the illumination light itself (hereinafter, it is referred to as a “light condition”), for example. The light condition may include at least one of an intensity of the illumination light and a wavelength of the illumination light, for example. The illumination condition may include a condition of the illumination apparatus  4  itself (hereinafter, it is referred to as an “apparatus condition”), for example. The apparatus condition may include at least one of a position of the illumination apparatus  4  (namely, an emission position from which the illumination light is emitted from the illumination apparatus  4 ) and a direction of the illumination apparatus  4  (namely, an attitude of the illumination apparatus  4 , and an emission direction along which the illumination apparatus  4  emits the illumination light), for example. 
     Especially, the illumination control unit  214   b  may control the illumination apparatus  4  based on the image score SC calculated by the score calculation unit  213 . Specifically, the illumination control unit  214   b  may control the illumination apparatus  4  so that the image score SC is improved (namely, becomes better). As described above, when the image score SC becomes larger as the quality of the person image IMG 1  becomes better (in other words, the reliability of the extracted key point KP 1  becomes higher) as described above, the illumination control unit  214   b  may control the illumination apparatus  4  so that the image score SC increases (alternatively, becomes maximum). When the image score SC becomes smaller as the quality of the person image IMG 1  becomes better (in other words, the reliability of the extracted key point KP 1  becomes higher) as described above, the illumination control unit  214   b  may control the illumination apparatus  4  so that the image score SC decreases (alternatively, becomes minimum). 
     In order to control the illumination apparatus  4  so that the image score SC is improved, the camera  1  may capture the image of the person in each of a plurality of situations between which the illumination condition is different. Specifically, the illumination control unit  214   b  may control the illumination apparatus  4  so that the illumination condition is set to be a first condition, and the camera  1  may generate an person image IMG 1 # 21  by capturing the image of the person in a situation where the illumination condition is set to be the first condition. Then, the illumination control unit  214   b  may control the illumination apparatus  4  so that the illumination condition is set to be a second condition that is different from the first condition, and the camera  1  may generate an person image IMG 1 # 22  by capturing the image of the person in a situation where the illumination condition is set to be the second condition. Then, the score calculation unit  213  may calculate an image score SC# 21  of the person image IMG 1 # 21  and an image score SC# 22  of the person image IMG 1 # 22 . Then, the illumination control unit  214   b  may set the illumination condition so that the image score SC is improved by comparing the image score SC# 21  and the image score SC# 22 . For example, the image score SC# 21  is better than the image score SC# 22 , the illumination control unit  214   b  may control the illumination apparatus  4  so that the illumination condition that is used in the subsequent operation is set to be the second condition. Subsequently, the camera  1  captures the image of the person in a situation where the illumination condition is set to be the second condition. Note that the illumination control unit  214   b  may repeats an operation for changing the illumination condition and setting the illumination condition based on a comparison result of the image scores SC before and after the illumination condition is changed, if needed. As a result, the illumination condition is changed so that the image score SC is improved more. 
     A scene in which the camera  1  captures the person that wears the glasses is one example of a scene in which the image score SC is improved by an operation of the illumination control unit  214   b.  As described above, when the camera  1  captures the person that wears the glasses, the person that wears the glasses is included in the person image IMG 1 . In this case, there is a possibility that the illumination light from the illumination apparatus  4  is reflected by the glasses. Thus, there is a possibility that the eye (especially, the iris) of the person is not included in the person image IMG 1  properly. For example, there is a possibility that a part of the eye (especially, the iris) of the person that should be exists in the rear of the lens of the glasses is hidden by the image of the reflection light on the lens of the glasses in the person image IMG 1 . On the other hand, when the illumination condition is changed, there is a possibility that a reflection aspect of the illumination light by the lens of the glasses changes. As a result, there is a possibility that a part of the eye (especially, the iris) of the person, which has been hidden by the image of the reflection light on the lens of the glasses, is included in the person image IMG 1 . In this case, it is possible to evaluate, based on the image score SC, whether or not the eye (especially, the iris) of the person is included in the person image IMG 1  properly. This is because the image score SC become relatively bad when a part of the eye (especially, the iris) of the person is hidden by the image of the reflection light on the lens of the glasses and the image score SC become relatively better when a part of the eye (especially, the iris) of the person is not hidden by the image of the reflection light on the lens of the glasses. Thus, in this case, the illumination control unit  214   b  is capable of controlling the illumination apparatus  4  so that a part of the eye (especially, the iris) of the person is not hidden by the image of the reflection light on the lens of the glasses (as a result, the image score SC is improved). 
     In this manner, in the second example embodiment, the key point extraction apparatus  2   b  is capable of controlling the illumination apparatus  4  so that the key point extraction unit  212  is capable of extracting the key point KP 1  with high accuracy (namely, it is evaluated that the reliability of the extracted key point KP 1  is relatively high). Thus, the key point extraction apparatus  2   b  is capable of taking the countermeasure for improving the quality of the person image IMG 1  while achieving an effect that is same as an effect that is achievable by the key point extraction apparatus  2  in the first example embodiment. 
     Note that the illumination control unit  214   b  may control the illumination apparatus  4  so that the image score SC is improved in a period during which an operation using the key point KP extracted by the key point extraction unit  212  (for example, the above described operation for authenticating the person by using the iris) is performed. The illumination control unit  214   b  may control the illumination apparatus  4  so that the image score SC is improved before the operation using the key point KP extracted by the key point extraction unit  212  (for example, the above described operation for authenticating the person by using the iris) is started. 
     (3) Key Point Extraction System SYS in Third Example Embodiment 
     Next, the key point extraction system SYS in a third example embodiment will be described. Note that the key point extraction system SYS in the third example embodiment is referred to as a “key point extraction system SYSc” in the below described description. 
     The key point extraction system SYSc in the third example embodiment is different from the above described key point extraction system SYSa in the first example embodiment in that it includes a key point extraction apparatus  2   c  instead of the key point extraction apparatus  2 . Another feature of the key point extraction system SYSc may be same as another feature of the key point extraction system SYSa. Thus, in the below describe description, with reference to  FIG.  6   , the key point extraction apparatus  2   c  in the third example embodiment will be described.  FIG.  6    is a block diagram that illustrates the configuration of the key point extraction apparatus  2   c  in the second example embodiment. 
     As illustrated in  FIG.  6   , the key point extraction apparatus  2   c  in the third example embodiment is different from the key point extraction apparatus  2  in the first example embodiment in that an image selection unit  215   c  that is one specific example of an “image selecting unit” is implemented in the arithmetic apparatus  21 . Another feature of the key point extraction apparatus  2   c  may be same as another feature of the key point extraction apparatus  2 . 
     The image selection unit  215   c  selects the person image IMG 1  having the image score SC that is calculated by the score calculation unit  213  and that satisfies a predetermined selection standard. Specifically, the image calculation unit  213  typically calculates the image score SC of the newly generated person image IMG 1  every time the camera  1  newly captures the image of the person (namely, every time the person image IMG 1  is newly generated). Thus, the score calculation unit  213  typically calculates the image score SC of each of the plurality of person images IMG 1 . The image selection unit  215   c  selects the person image IMG 1  the image score SC of which satisfies the predetermined selection condition from the plurality of person images IMG 1 . 
     The selected person image IMG 1  may be used for a desire use. For example, the selected person image IMG 1  may be used for a use of the training of the key point extraction unit  212  (specifically, the training of the learning model used by the above described key point extraction unit  212 ). When the selected person image IMG 1  is used for the desire use, the selection standard that is used to select the person image IMG 1  may be set based on the desired use. For example, the selection standard may be set based on the use of the training of the learning model. 
     A first standard that the image score SC is worse than a predetermined selection threshold value is one example of the selection standard that is set based on the use of the training of the learning model. In this case, the image selection unit  215   c  selects the person image IMG 1  the image score SC of which is worse than the selection threshold value. For example, when the image score SC becomes larger as the quality of the person image IMG 1  becomes better (in other words, the reliability of the extracted key point KP 1  becomes higher) as described above, the image selection unit  215   c  selects the person image IMG 1  the image score SC of which is smaller than the selection threshold value. For example, when the image score SC becomes smaller as the quality of the person image IMG 1  becomes better (in other words, the reliability of the extracted key point KP 1  becomes higher) as described above, the image selection unit  215   c  selects the person image IMG 1  the image score SC of which is larger than the selection threshold value. 
     When the first standard is used as the selection standard, the image selection unit  215   c  selects the person image IMG 1  the image score SC of which is relatively bad. As described in the first example embodiment, there is a relatively high possibility that the person image IMG 1  the image score SC of which is relatively bad is the person image IMG 1  that is not sufficiently learned by the learning model. Thus, when the first standard is used as the selection standard, the image selection unit  215   c  is capable of selecting the person image IMG 1  that is not sufficiently learned by the learning model. As a result, the training of the learning model is performed by using the person image IMG 1  that is not sufficiently learned by the learning model. Thus, the training of the learning model is performed more efficiently, compared to a case where the training of the learning model is performed by using the person image IMG 1  that is sufficiently learned by the learning model. Namely, a training efficiency of the learning model improves. 
     Note that the selection threshold value that is used by the first standard may be set to be a desired value that allows the person image IMG 1  that is not sufficiently learned by the learning model (namely, that is incompatible to the learning model) to be distinguished from the person image IMG 1  that is sufficiently learned by the learning model (namely, that is compatible to the learning model) by the image score SC. 
     A second standard that the image score SC is included in a range of the image score SC into which a training image, the sampled number of which is smaller than a predetermined number, is classified when a plurality of training images that are already learned by the learning model are classified based on the image score SC in a situation where the learning model is already trained by using the plurality of training images the image scores of which are known. For example,  FIG.  7    illustrates a relationship between the sampled number of the training image and the image score SC of the training image. Namely,  FIG.  7    illustrates the sampled number of the training image having a certain image score SC for each image score SC. Here, in an example illustrated in  FIG.  7   , the predetermined number is set to be a threshold value TH. In this case, as illustrated in  FIG.  7   , the range of the image score SC in which the sampled number of the training image is smaller than the predetermined number (=threshold value TH) is a range of “a predetermined score SC 1 &lt;the image score SC &lt;a second predetermined score SC 2 ”. Therefore, in the example illustrated in  FIG.  7   , the image selection unit  215   c  selects the person image IMG 1  the image score SC of which is larger than the predetermined score SC 1  and is smaller than the predetermined score SC 2 . 
     When the second standard is used as the selection standard, the image selection unit  215   c  selects the person image IMG 1  the image score SC of which is different from that of the training image that is already learned by the learning model. There is a relatively high possibility that the person image IMG 1  the image score SC of which is different from that of the training image that is already learned by the learning model is the person image IMG 1  that is not sufficiently learned by the learning model. Thus, when the second standard is used as the selection standard, the image selection unit  215   c  is capable of selecting the person image IMG 1  that is not sufficiently learned by the learning model. As a result, the training of the learning model is performed by using the person image IMG 1  that is not sufficiently learned by the learning model. Thus, the training of the learning model is performed more efficiently, compared to a case where the training of the learning model is performed by using the person image IMG 1  that is sufficiently learned by the learning model. Namely, a training efficiency of the learning model improves. 
     Note that the predetermined number (for example, the threshold value TH in  FIG.  7   ) that is used by the second standard may be set to be a desired value that allows the person image IMG 1  that is not sufficiently learned by the learning model (namely, that is incompatible to the learning model) to be distinguished from the person image IMG 1  that is sufficiently learned by the learning model (namely, that is compatible to the learning model) by the sampled number thereof. 
     When a supervised learning is performed to perform the training of the learning model by using the person image IMG 1 , it is desired to generate training data including the person image IMG 1  and a ground truth label by assigning, to the person image IMG 1 , the ground truth label of the key point KP that should be extracted from the person image IMG 1  (namely, performing an annotation). However, it typically takes a lot of effort to assigning the ground truth label. However, when the first standard or the second standard is used as the selection condition, it is sufficient to assign the ground truth label to the person image IMG 1  that is selected based on the first standard or the second standard from the plurality of person images IMG 1 . It is not necessary to assigning the ground truth label to all of the plurality of person images IMG 1 . Thus, in the second example embodiment, the effort required for assigning the ground truth label is reduced. Namely, the effort required for generating the training data is reduced. 
     Note that the image selection unit  215   c  may select the person image IMG 1  that satisfies both of the first standard and the second standard. For example, the image selection unit  215   c  may select a plurality of person images IMG 1  the image scores SC of which satisfy the first standard from the plurality of person images IMG 1  and then select a plurality of person images IMG 1  that satisfy the second standard from the plurality of person images IMG 1  the image scores SC of which satisfy the first standard. 
     In this manner, in the third example embodiment, the key point extraction apparatus  2   c  is capable of selecting (for example, collecting) the person image IMG 1  the image score SC of which satisfies the selection condition. Thus, the key point extraction apparatus  2   c  is capable of performing a desired operation (for example, the training of the learning model used by the key point extraction unit  212 ) by using the selected person image IMG 1  while achieving an effect that is same as the effect that is achievable by the key point extraction apparatus  2  in the first example embodiment. 
     Note that the key point extraction apparatus  2   b  in the second example embodiment described above may include a feature that is unique to the key point extraction apparatus  2   c  in the third example embodiment. The feature that is unique to the key point extraction apparatus  2   c  in the third example embodiment may include the image selection unit  215   c.  The feature that is unique to the key point extraction apparatus  2   c  in the third example embodiment may include a feature related to a selection of the person image IMG 1  based on the image score SC. 
     (4) Key Point Extraction System SYS in Fourth Example Embodiment 
     Next, the key point extraction system SYS in a fourth example embodiment will be described. Note that the key point extraction system SYS in the fourth example embodiment is referred to as a “key point extraction system SYSd” in the below described description. 
     The key point extraction system SYSd in the fourth example embodiment is different from the above described key point extraction system SYSa in the first example embodiment in that it includes a key point extraction apparatus  2   d  instead of the key point extraction apparatus  2 . Another feature of the key point extraction system SYSd may be same as another feature of the key point extraction system SYSa. Thus, in the below describe description, with reference to  FIG.  8   , the key point extraction apparatus  2   d  in the fourth example embodiment will be described.  FIG.  8    is a block diagram that illustrates the configuration of the key point extraction apparatus  2   d  in the fourth example embodiment. 
     As illustrated in  FIG.  8   , the key point extraction apparatus  2   d  in the fourth example embodiment is different from the key point extraction apparatus  2  in the first example embodiment in that a training unit  216   d  that is one specific example of a “training unit” and a weight calculation unit  217   d  that is one specific example of the “training unit” are implemented in the arithmetic apparatus  21 . Furthermore, the key point extraction apparatus  2   d  is different from the key point extraction apparatus  2  in that the storage apparatus  22  stores training data  221   d  that is used for the training of the learning model used by the key point extraction unit  212 . Another feature of the key point extraction apparatus  2   d  may be same as another feature of the key point extraction apparatus  2 . 
     The training unit  216   d  performs the training of the learning model, which is used by the key point extraction unit  212 , by using the training data  221   d.  In the fourth example embodiment, the training unit  216   d  performs the training of the learning model by performing a semi-supervised learning using the training data  221   d.  Thus, the training unit  216   d  performs the training of the learning model by using the training data  221   d  for performing the semi-supervised learning. 
       FIG.  9    illustrates one example of the training data  221   d  for performing the semi-supervised learning. As illustrated in  FIG.  9   , the training data  221   d  includes training data  2211   d  with label and training data  2212   d  without label. The training data  2211   d  with label is a data set including a plurality of unit data  2213   d  with label each of which includes a training image IMG 3  and a ground truth label that indicates the key point KP that should be extracted from the training image IMG 3 . On the other hands, the training data  2212   d  without label is a data set including a plurality of unit data  2214   d  without label each of which includes the training image IMG 3  but does not include the ground truth label. In the below described description, the training image IMG 3  included in the training data  2211   d  with label is referred to as the “training image IMG 3 - 1 ” and the training image IMG 3  included in the training data  2212   d  without label is referred to as the “training image IMG 3 - 2 ”. The number of the training image IMG 3 - 1  included in the training data  2211   d  with label (namely, the number of the unit data  2213   d  with label) may be smaller than the number of the training image IMG 3 - 2  included in the training data  2212   d  without label (namely, the number of the unit data  2214   d  with label). 
     The training unit  216   d  may perform the training of the learning model by using an existing algorithm for performing the semi-supervised learning. For example, the training unit  216   d  may perform the training of the learning model by using an algorithm based on a bootstrap method. In this case, the training unit  216   d  may firstly perform the training of the learning model by using the training data  2211   d  with label. The training of the learning model by using the training data  2211   d  with label may be the supervised learning. Then, the training unit  216   d  may assign a pseudo label, which indicates the key point KP that is estimated to be extracted from each training image IMG 3 - 2 , to at least a part of the plurality of training image IMG 3 - 2  included in the training data  2212   d  without label based on a result of the training using the training data  2211   d  with label. For example, the training unit  216   d  assigns the pseudo label to at least one training image IMG 3 - 2  having a relatively high reliability of training image IMG 3 - 2  included in the training data  2212   d  without label. Here, the “training image IMG 3 - 2  having the relatively high reliability” here may mean the training image IMG 3 - 2  that a certainty of the key point KP that is estimated to be extracted therefrom is relatively high. Then, the training unit  216   d  may perform the training of the learning model by using the training data  2211   d  with label and the unit data  2214   d  without label to which the pseud label is assigned of the training data  2212   d  without label. The training of the learning model by using the training data  2211   d  with label and the unit data  2214   d  without label to which the pseud label is assigned of the training data  2212   d  without label may also be the supervised learning. The training unit  216   d  may repeat an operation that includes an assignation of the pseud label and the supervised learning (namely, the training of the learning model by using the training data  2211   d  with label and the unit data  2214   d  without label to which the pseud label is assigned of the training data  2212   d  without label) by necessary times. Thus, in the third example embodiment, the number of epoch is the number of times by which the operation that includes the assignation of the pseud label and the supervised learning is repeated. For example, the training unit  216   d  may repeat the supervised learning and the assignation of the pseud label alternately until a loss function satisfies a predetermined learning end condition. As a result, the semi-supervised learning is completed. 
     The weight calculation unit  217   d  calculates a weight w of the pseud label. In order to calculate the weight w of the pseud label, the weight calculation unit  217   d  may use the image scores SC of the plurality of training images IMG 3 - 2  included in the training data  2212   d  without label. 
     Thus, the key point extraction apparatus  2   d  may perform the key point extraction operation illustrated in  FIG.  3    for the plurality of training images IMG 3 - 2  included in the training data  2212   d  without label. Namely, the key point extraction apparatus  2   d  may obtain the training image IMG 3 - 2  (the step S 11  in  FIG.  3   ), the key point extraction unit  212  may extract the key point KP from the training image IMG 3 - 2  (the step S 12  in  FIG.  3   ), the image conversion unit  211  may calculate the conversion image IMG 2  by performing the image conversion processing that convers the training image IMG 3 - 2  (the step S 13 ), the key point extraction unit  212  may extract the key point KP from the conversion image IMG 2  (the step S 14  in  FIG.  3   ), and the score calculation unit  213  may calculate the image score SC of the training image IMG 3 - 2  based on the key point KP extracted from the training image IMG 3 - 2  and the key point KP extracted from the conversion image IMG 2  (the step S 15  in  FIG.  3   ). 
     Then, the weight calculation unit  217   d  calculates the weight w of the pseud label that is assigned to each training image IMG 3 - 2  based on the image score SC of each training image IMG 3 - 2 . For example, the weight calculation unit  217   d  may calculate the weight w so that the weight w of the pseud label that is assigned to one training image IMG 3 - 2  becomes larger as the image score SC of one training image IMG 3 - 2  becomes better. For example, the weight calculation unit  217   d  may calculate the weight w so that the weight w of the pseud label that is assigned to one training image IMG 3 - 2  becomes smaller as the image score SC of one training image IMG 3 - 2  becomes worse. As one example, the weight calculation unit  217   d  may calculates an inverse number of the image score SC as the weight w. note that the weight w may be a value that is equal to or larger than 0 and that is equal to or smaller than 1. 
     The calculated weight w may be used by the training unit  216   d  that performs the semi-supervised learning. For example, in order to perform the training of the learning model, the training unit  216   d  may use the unit data  2214   d  without label to which the pseud label having the relatively large weight w is assigned. For example, in order to perform the training of the learning model, the training unit  216   d  may use the unit data  2214   d  without label to which the pseud label having the weight w larger than a predetermined weight threshold value is assigned. On the other hand, for example, in order to perform the training of the learning model, the training unit  216   d  may not use the unit data  2214   d  without label to which the pseud label having the relatively small weight w is assigned. For example, in order to perform the training of the learning model, the training unit  216   d  may not use the unit data  2214   d  without label to which the pseud label having the weight w smaller than the predetermined weight threshold value is assigned. Namely, in order to perform the training of the learning model, the training unit  216   d  may use the training image IMG 3 - 2  to which the pseud label having the relatively large weight w is assigned preferentially. As a result, in order to perform the training of the learning model, the training unit  216   d  uses the leaning image IMG 3 - 2  the quality of which is relatively good (namely, the training image IMG 3 - 2  that the possibility of precisely extracting the key point KP 1  by the learning model therefrom is relatively high) preferentially. In this case, the number of the training image IMG 3 - 2  that the possibility of precisely extracting the key point KP 1  by the learning model therefrom is relatively high gradually increases as the semi-supervised learning is performed more. Namely, it is possible to reduce an opportunity for the training that uses the training image IMG 3 - 2  that the possibility of precisely extracting the key point KP 1  by the learning model therefrom is relatively low at an early phase of the training at which the semi-supervised learning is not sufficiently performed. 
     Note that the weight threshold value may be set to be a desired value that allows the training image IMG 3 - 2  that is not sufficiently learned by the learning model (namely, that is incompatible to the learning model) to be distinguished from the training image IMG 3 - 2  that is sufficiently learned by the learning model (namely, that is compatible to the learning model) by the image score SC. 
     The weight calculation unit  217   d  may calculate new weight w every time the training unit  216   d  performs the training of the learning model one time (namely, performs the operation including the assignation of the pseud label and the supervised learning one time). Namely, the weight calculation unit  217   d  may calculate the weight w for each epoch. This is because a behavior of the key point extraction unit  212  changes every time the training unit  216   d  performs the training of the learning model one time, and thus, there is a possibility that the image score SC that is calculated based on the key point KP extracted by the key point extraction unit  212  changes and the weight w that is calculated based on the image score SC changes. 
     In this manner, in the fourth example embodiment, the key point extraction apparatus  2   d  is capable of performing the training of the learning model by using the training data  221   d  and the weight w that is calculated based on the image score SC. Thus, thus, the key point extraction apparatus  2   d  is capable of performing the training of the learning model efficiently while achieving an effect that is same as the effect that is achievable by the key point extraction apparatus  2  in the first example embodiment. Furthermore, the key point extraction apparatus  2   d  is capable of performing the training of the learning model efficiently by reducing the effort for the annotation, because the training of the learning model is performed by using the semi-supervised learning. 
     Note that at least one of the key point extraction apparatus  2   b  in the second example embodiment to the key point extraction apparatus  2   c  in the third example embodiment described above may include a feature that is unique to the key point extraction apparatus  2   d  in the fourth example embodiment. The feature that is unique to the key point extraction apparatus  2   d  in the fourth example embodiment may include the training unit  216   d  and the weight calculation unit  217   d.  The feature that is unique to the key point extraction apparatus  2   d  in the fourth example embodiment may include a feature related to the semi-supervised leaning using the weight w. 
     (5) Key Point Extraction System SYS in Fifth Example Embodiment 
     Next, the key point extraction system SYS in a fifth example embodiment will be described. Note that the key point extraction system SYS in the fifth example embodiment is referred to as a “key point extraction system SYSe” in the below described description. 
     The key point extraction system SYSe in the fifth example embodiment is different from the above described key point extraction system SYSa in the first example embodiment in that it includes a key point extraction apparatus  2   e  instead of the key point extraction apparatus  2 . Another feature of the key point extraction system SYSe may be same as another feature of the key point extraction system SYSa. Thus, in the below describe description, with reference to  FIG.  10   , the key point extraction apparatus  2   e  in the fifth example embodiment will be mainly described.  FIG.  10    is a block diagram that illustrates the configuration of the key point extraction apparatus  2   e  in the fifth example embodiment. 
     As illustrated in  FIG.  10   , the key point extraction apparatus  2   e  in the fifth example embodiment is different from the key point extraction apparatus  2  in the first example embodiment in that an image determination unit  218   e  that is one specific example of a “determining unit” is implemented in the arithmetic apparatus  21 . Another feature of the key point extraction apparatus  2   e  may be same as another feature of the key point extraction apparatus  2 . 
     The image determination unit  218   e  may determine based on the image score SC whether or not the eye including the iris of the person is included in the person image IMG 1 . In order to determine whether or not the eye is included in the person image IMG 1 , the image determination unit  218   e  may determine whether or not the calculated image score SC is worse than a predetermined first determination threshold value TH 1 . For example, when the image score SC becomes larger as the quality of the person image IMG 1  becomes better, the image determination unit  218   e  may determine whether or not the calculated image score SC is smaller than the predetermined first determination threshold value TH 1 . For example, when the image score SC becomes larger as the quality of the person image IMG 1  becomes worse, the image determination unit  218   e  may determine whether or not the calculated image score SC is larger than the predetermined first determination threshold value TH 1 . As a result of the determination, when it is determined that the image score SC is worse than the predetermined first determination threshold value TH 1 , the image determination  218   e  may determine that the eye is not included in the person image IMG 1 . This is because the key point KP of the iris is not extracted when the eye is not included in the person image IMG 1  and thus the image score SC becomes worse. On the other hand, when it is determined that the image score SC is better than the predetermined first determination threshold value TH 1 , the image determination  218   e  may determine that the eye is included in the person image IMG 1 . 
     When the eye is not included in the person image IMG 1 , there is a possibility that a state where the image score SC is worse than the predetermined first determination threshold value TH 1  continues for a certain time or more. Thus, the image determination  218   e  may determine that the eye is not included in the person image IMG 1  when the state where the image score SC is worse than the predetermined first determination threshold value TH 1  continues for a second determination threshold value TH 2  or more. On the other hand, the image determination  218   e  may determine that the eye is included in the person image IMG 1  when the state where the image score SC is worse than the predetermined first determination threshold value TH 1  continues only for a time that is shorter than the second determination threshold value TH 2 . Namely, even when it is determined that the image score SC is worse than the predetermined first determination threshold value TH 1 , the image determination  218   e  may determine that the eye is included in the person image IMG 1  when the state where the image score SC is worse than the predetermined first determination threshold value TH 1  continues for the time that is shorter than the second determination threshold value TH 2 . This is because there is a possibility that the image score SC is determined to be worse than the predetermined first determination threshold value TH 1  when the person included in the person image IMG 1  blinks, even when the eye is included in the person image IMG 1 . 
     Conversely, when the state where the image score SC is worse than the predetermined first determination threshold value TH 1  continues for the time that is shorter than the second determination threshold value TH 2 , the image determination unit  218   e  may determine that the eye is included in the person image IMG 1  but the eye included in the person image IMG 1  blinks. Namely, when the state where the image score SC is worse than the predetermined first determination threshold value TH 1  continues for the time that is shorter than the second determination threshold value TH 2  in a situation where it is determined that the eye is included in the person image IMG 1 , the image determination unit  218   e  may determine that the eye included in the person image IMG 1  blinks during that time. 
     In order to determine whether or not the state where the image score SC is worse than the predetermined first determination threshold value TH 1  continues for the second determination threshold value TH 2  or more, the camera  1  may generate the plurality of person images IMG 1  that corresponds to time-series data by continuously capturing the image of the same person. Furthermore, the key point extraction apparatus  2  may calculate the plurality of image scores SC that correspond to the plurality of person images IMG 1 , respectively. The plurality of calculated image scores SC indicate a temporal variation of the image score SC. Thus, the image determination unit  218  is capable of determining based on the temporal variation of the image score SC whether or not the state where the image score SC is worse than the predetermined first determination threshold value TH 1  continues for the second determination threshold value TH 2  or more 
     Note that the first determination threshold value TH 1  may be set to be a desired value that allows the person image IMG 1  in which the eye is included to be distinguished from the person imagen IMG 1  in which the eye is not included by the image score SC. The second determination threshold value TH 2  may be set to be a desired value that allows the person image IMG 1  in which a blinking (namely, closed) eye is included to be distinguished from the person imagen IMG 1  in which the eye is not included by the image score SC. 
     In this manner, in the fifth example embodiment, the key point extraction apparatus  2   e  is capable of determining whether or not the eye is included in the person image IMG 1 . In this case, the key point extraction apparatus  2   e  may exclude the person image IMG 1  in which the eye is not included from a target for the operation performed by using the key point KP (for example, the above described operation for authenticating the person by using the iris). As a result, a time required for the operation performed by using the key point KP is reducible. 
     Moreover, in the fifth example embodiment, the key point extraction apparatus  2   e  is capable of determining whether or not the eye included in the person image IMG 1  blinks. In this case, the key point extraction apparatus  2   e  may exclude the person image IMG 1  in which the blinking (namely, closed) eye is included from the target for the operation performed by using the key point KP. As a result, the time required for the operation performed by using the key point KP is reducible. 
     Therefore, the key point extraction apparatus  2   e  is capable of reducing the time required for the operation performed by using the key point KP while achieving an effect that is same as the effect that is achievable by the key point extraction apparatus  2  in the first example embodiment. 
     Note that at least one of the key point extraction apparatus  2   b  in the second example embodiment to the key point extraction apparatus  2   d  in the fourth example embodiment described above may include a feature that is unique to the key point extraction apparatus  2   e  in the fifth example embodiment. The feature that is unique to the key point extraction apparatus  2   e  in the fifth example embodiment may include the image determination unit  218   e.  The feature that is unique to the key point extraction apparatus  2   e  in the fifth example embodiment may include a feature related to at least one of the determination whether or not the eye is included in the person image IMG 1  and the determination whether or not the eye included in the person image IMG 1  blinks. 
     (6) Key Point Extraction System SYS in Sixth Example Embodiment 
     Next, the key point extraction system SYS in a sixth example embodiment will be described. Note that the key point extraction system SYS in the sixth example embodiment is referred to as a “key point extraction system SYSf” in the below described description. 
     The key point extraction system SYSf in the sixth example embodiment is different from the above described key point extraction system SYSa in the first example embodiment in that it includes a key point extraction apparatus  2   f  instead of the key point extraction apparatus  2 . Another feature of the key point extraction system SYSf may be same as another feature of the key point extraction system SYSa. Thus, in the below describe description, with reference to  FIG.  11   , the key point extraction apparatus  2   f  in the sixth example embodiment will be mainly described.  FIG.  11    is a block diagram that illustrates the configuration of the key point extraction apparatus  2   f  in the sixth example embodiment. 
     As illustrated in  FIG.  11   , the key point extraction apparatus  2   f  in the sixth example embodiment is different from the key point extraction apparatus  2  in the first example embodiment in that the arithmetic apparatus  21  may not include the image conversion unit  211 . Another feature of the key point extraction apparatus  2   f  may be same as another feature of the key point extraction apparatus  2 . Note that the key point extraction apparatus  2   f  may not include the storage apparatus  22 , the communication apparatus  23 , the input apparatus  24  and the output apparatus  25 . However, the key point extraction apparatus  2   f  may include at least one of the storage apparatus  22 , the communication apparatus  23 , the input apparatus  24  and the output apparatus  25 . 
     In the above described description about the first example embodiment to the fifth example embodiment, the key point extraction apparatus  2  calculates the image score SC by comparing the key point KP 1  extracted from the person image IMG 1  and the key point KP 2  extracted from the conversion image IMG 2  that is generated by performing the image conversion processing on the person image IMG 1 . However, the key point extraction apparatus  2   f  in the sixth example embodiment may calculate the image score SC without generating the conversion image IMG 2 . The key point extraction apparatus  2   f  may calculate the image score SC by using the key point KP 1  and without using the key point KP 2 . 
     Note that at least one of the key point extraction apparatus  2   b  in the second example embodiment to the key point extraction apparatus  2   e  in the fifth example embodiment described above may not include the image conversion unit  211  either. 
     (7) Supplementary Note 
     With respect to the example embodiments described above, the following Supplementary Notes will be further disclosed. 
     Supplementary Note 1 
     An information processing apparatus including: 
     an extracting unit that extracts a key point of a target object as a target key point from an input image; and 
     a calculating unit that calculates, as a score of the input image from which the target key point is extracted, an index value related to a reliability of the target key point based on the target key point. 
     Supplementary Note 2 
     The information processing apparatus according to Supplementary Note 1 further including an image converting unit that generates a conversion image by performing an image conversion processing that converts the input image, 
     the extracting unit extracting a key point of the target object as a conversion key point from the conversion image, 
     the calculating unit calculating the score based on a comparison result of the target key point and the conversion key point. 
     Supplementary Note 3 
     The information processing apparatus according to Supplementary Note 1 or 2, wherein 
     the input image is generated by an imaging apparatus capturing an image of an imaging target range that is illuminated by an illumination apparatus, 
     the information processing apparatus further includes an illumination control apparatus that controls the illumination apparatus based on the score so that the score is improved. 
     Supplementary Note 4 
     The information processing apparatus according to any one of Supplementary Notes 1 to 3, wherein 
     the extracting unit extracts the target key point from each of a plurality of input images, 
     the calculating unit calculates the score for each input image, 
     the information processing apparatus further includes a selecting unit that selects, from the plurality of input images, at least one input image the score of which satisfies a predetermined selection condition. 
     Supplementary Note 5 
     The information processing apparatus according to Supplementary Note 4, wherein 
     the selection condition includes a condition that the score is worse than a predetermined selection threshold value. 
     Supplementary Note 6 
     The information processing apparatus according to Supplementary Note 4 or 5, wherein 
     the extracting unit extracts the target key point by using a leaning model that is already trained by using a plurality of training images the score of each of which is known, 
     the selection condition includes a condition that the score is included in a range of the score in which the sampled number of the training image is smaller than a predetermined number. 
     Supplementary Note 7 
     The information processing apparatus according to any one of Supplementary Notes 1 to 6, wherein 
     the extracting unit extracts the target key point by using a leaning model that is trainable, 
     the information processing apparatus further includes a training unit that performs a training of the learning model by using training data that includes a first training image with which a ground truth key point, which is a key point to be extracted, is associated and a second training image with which the ground truth key point is not associated, 
     the extracting unit extracts a key point of the target object as a training key point from the second training image, 
     the calculating unit calculates, as a score of the second training image from which the training key point is extracted, an index value related to a reliability of the training key point based on the training key point, 
     the training unit calculates, based on the score of the second training image, a weight that indicates a degree of a contribution of the second training image to the training of the learning model, and performs the training of the learning model by performing a semi-supervised learning using the training data and the weight. 
     Supplementary Note 8 
     The information processing apparatus according to any one of Supplementary Notes 1 to 7, wherein 
     the target object includes an iris of a living body, 
     the information processing apparatus further includes a determining unit that determines that an eye including the iris is not included in the input image when the score is worse than a predetermined first determination threshold value. 
     Supplementary Note 9 
     The information processing apparatus according to Supplementary Note 8, wherein 
     the determining unit determines that a blinking eye is included in the input image when it is determined that the eye is included in the input image and a time during which the score keeps being worse than a predetermined second threshold value is shorter than a predetermined time. 
     Supplementary Note 10 
     An information processing method including: 
     extracting a key point of a target object as a target key point from an input image; and 
     calculating, as a score of the input image from which the target key point is extracted, an index value related to a reliability of the target key point based on the target key point. 
     Supplementary Note 11 
     A recording medium on which a computer program that allows a computer to execute an information processing method is recorded, 
     the information processing method comprising: 
     extracting a key point of a target object as a target key point from an input image; and 
     calculating, as a score of the input image from which the target key point is extracted, an index value related to a reliability of the target key point based on the target key point. 
     At least a part of the feature of each embodiment described above may be combined with at least other part of the feature of each embodiment described above. A part of the feature of each embodiment described above may not be used. Moreover, the disclosures of all documents (for example, publications) that are cited in the present disclosure described above are incorporated in the present disclosure by reference if it is legally permitted. 
     The present disclosure is allowed to be changed, if desired, without departing from the essence or spirit of the invention which can be read from the claims and the entire specification, and an information processing apparatus, an information processing method, a computer program and a recording medium, which involve such changes, are also intended to be within the technical scope of the present disclosure. 
     DESCRIPTION OF REFERENCE CODES 
       1  camera 
       2  key point extraction apparatus 
       21  arithmetic apparatus 
       211  image conversion unit 
       212  key point extraction unit 
       213  score calculation unit 
       214   b  illumination control unit 
       215   c  image selection unit 
       216   d  weight calculation unit 
       217   d  training unit 
       218   e  image determination unit 
       3  communication network 
       4  illumination apparatus 
     SYS key point extraction system 
     IMG 1  person image 
     IMG 2  conversion image 
     KP key point