Patent Publication Number: US-2021161376-A1

Title: Ophthalmic device, control method therefor, and recording medium

Description:
TECHNICAL FIELD 
     The present invention relates to an ophthalmic apparatus, a method of controlling the same, a program, and a recording medium. 
     BACKGROUND ART 
     Various kinds of imaging apparatuses and measuring apparatuses are utilized in ophthalmic medical care. In recent years, ophthalmic apparatuses to which optical coherence tomography (OCT) technology is applied are widely used. OCT is typically applied to eye fundus imaging, anterior eye segment imaging, tissue thickness measurement, ocular axial length measurement, and the like. 
     In order to apply OCT to a living eye, various preparatory operations are required to be carried out in an accurate and appropriate manner. Such preparatory operations include the followings: position adjustment (alignment) of the optical system with respect to a target site; adjustment of the depiction position of the target site in the image frame; adjustment of image quality (signal to noise ratio), and the like. In addition, it is necessary to conduct imaging and/or measurement at an appropriate timing after checking whether or not these conditions have been satisfied. 
     A person skilled in handling ophthalmic apparatuses may be able to conduct such a series of preparatory operations accurately, appropriately and promptly by performing operations on the ophthalmic apparatus according to eye movements, and/or by sending instructions to the subject. However, in the cases where an ophthalmic apparatus is used in a situation in which no expert is present at that examination place, it may impose an excessive burden on the subject and the examiner. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     [PATENT DOCUMENT 1] Japanese Unexamined Patent Application Publication No. 2018-023675 
     BRIEF SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     An object of the present invention is to reduce the burden on the subject and the examiner by automating a preparatory operation for applying OCT to a living eye, particularly the anterior segment thereof. 
     Means for Solving the Problem 
     The first aspect of some embodiment examples is an ophthalmic apparatus comprising: an optical coherence tomography (OCT) optical system configured to apply an OCT scan to an anterior segment of an eye; an image constructing unit configured to construct an image based on data acquired by the OCT scan; a scan area setting unit configured to set a scan area in a region passing through an iris outer edge of the anterior segment; a first scan controller configured to perform control of the OCT optical system to apply an OCT scan to the scan area set by the scan area setting unit; an image quality evaluating unit configured to calculate an image quality evaluation value of an image constructed by the image constructing unit based on data acquired by the OCT scan applied to the scan area; a corner angle image detecting unit configured to analyze the image constructed by the image constructing unit based on the data acquired by the OCT scan applied to the scan area, to detect a corner angle image; a position judging unit configured to judge whether the corner angle image detected by the corner angle image detecting unit is located within a first area in an image frame; and a second scan controller configured to perform control of the OCT optical system to apply an OCT scan of a predetermined pattern to the anterior segment, if the image quality evaluation value calculated by the image quality evaluating unit is equal to or greater than a predetermined threshold and the position judging unit judges that the corner angle image is located within the first area. 
     The second aspect of some embodiment examples is the ophthalmic apparatus of the first aspect, further comprising: an anterior segment photographing system configured to photograph the anterior segment; a movement mechanism configured to move the OCT optical system; a destination determining unit configured to analyze an anterior segment image acquired by the anterior segment photographing system to determine a destination of the OCT optical system; and a movement controller configured to perform control of the movement mechanism based on the destination determined by the destination determining unit, wherein the scan area setting unit performs scan area setting after the movement controller performs the control of the movement mechanism. 
     The third aspect of some embodiment examples is the ophthalmic apparatus of the second aspect, wherein the destination determining unit analyzes the anterior segment image to detect a pupil center and the iris outer edge, and determines the destination based on the pupil center and the iris outer edge. 
     The fourth aspect of some embodiment examples is the ophthalmic apparatus of the third aspect, wherein the destination determining unit determines a straight line that passes through the pupil center and extends along a predetermined direction, and determines an intersection point of the straight line and the iris outer edge as the destination. 
     The fifth aspect of some embodiment examples is the ophthalmic apparatus of the fourth aspect, wherein the scan area setting unit sets the scan area that passes through the intersection point. 
     The sixth aspect of some embodiment examples is the ophthalmic apparatus of the fifth aspect, wherein the scan area setting unit sets a scan line along the straight line wherein a center of the scan line is located at the intersection point. 
     The seventh aspect of some embodiment examples is the ophthalmic apparatus of any of the second to sixth aspects, wherein the scan area setting unit sets the scan area that passes through the destination determined by the destination determining unit. 
     The eighth aspect of some embodiment examples is the ophthalmic apparatus of any of the second to seventh aspects, wherein the OCT optical system applies a repetitive OCT scan to the scan area set after the control of the movement mechanism, and the image constructing unit constructs a plurality of images based respectively on a plurality of data sets successively acquired by the repetitive OCT scan. 
     The ninth aspect of some embodiment examples is the ophthalmic apparatus of the eighth aspect, wherein the repetitive OCT scan is a repetitive B-scan. 
     The tenth aspect of some embodiment examples is the ophthalmic apparatus of the eighth or ninth aspect, wherein the corner angle image detecting unit performs corner angle image detection after the image quality evaluating unit obtains an image quality evaluation value equal to or greater than the predetermined threshold. 
     The eleventh aspect of some embodiment examples is the ophthalmic apparatus of any of the first to tenth aspects, further comprising an iris image detecting unit configured to analyze the image constructed by the image constructing unit based on the data acquired by the OCT scan applied to the scan area, to detect an iris image, wherein the position judging unit judges whether the corner angle image detected by the corner angle image detecting unit is located within the first area in the image frame and judges whether the iris image detected by the iris image detecting unit is located within a second area, and the second scan controller performs the control of the OCT optical system to apply the OCT scan of the predetermined pattern to the anterior segment, if the image quality evaluation value calculated by the image quality evaluating unit is equal to or greater than the predetermined threshold and the position judging unit judges that the corner angle image is located within the first area and the iris image is located within the second area. 
     The twelfth aspect of some embodiment examples is the ophthalmic apparatus of any of the first to eleventh aspects, wherein the corner angle image detecting unit analyzes the image constructed by the image constructing unit based on the data acquired by the OCT scan applied to the scan area to detect a posterior corneal surface and an anterior iris surface, and detects an intersection position of the posterior corneal surface and the anterior iris surface as a corner angle of the eye. 
     The thirteenth aspect of some embodiment examples is the ophthalmic apparatus of any of the first to twelfth aspects, wherein the image quality evaluating unit calculates, as the image quality evaluation value, a ratio of a signal of an anterior segment region to a noise of a background region in the image constructed by the image constructing unit. 
     The fourteenth aspect of some embodiment examples is the ophthalmic apparatus of the thirteenth aspect, wherein the image quality evaluating unit calculates, as the image quality evaluation value, a ratio of a signal of a corneal region to a noise of a first background region adjacent to the corneal region in the image constructed by the image constructing unit. 
     The fifteenth aspect of some embodiment examples is the ophthalmic apparatus of the thirteenth or fourteenth aspect, wherein the image quality evaluating unit calculates, as the image quality evaluation value, a ratio of a signal of an iris region to a noise of a second background region adjacent to the iris region in the image constructed by the image constructing unit. 
     The sixteenth aspect of some embodiment examples is the ophthalmic apparatus of any of the thirteenth to fifteenth aspects, wherein the OCT optical system includes a measurement arm configured to guide measurement light to the anterior segment and a reference arm configured to guide reference light that is superposed on return light of the measurement light returned from the anterior segment, wherein at least one of the measurement arm and the reference arm includes a polarization device that changes a polarization state of light guided thereby, and the ophthalmic apparatus further comprising a polarization controller configured to perform control of the polarization device to increase the ratio calculated by the image quality evaluating unit. 
     The seventeenth aspect of some embodiment examples is a method of controlling an ophthalmic apparatus including an optical coherence tomography (OCT) optical system that applies an OCT scan to an anterior segment of an eye and an image constructing unit that constructs an image based on data acquired by the OCT scan, the method comprising: setting a scan area in a region passing through an iris outer edge of the anterior segment; performing control of the OCT optical system to apply an OCT scan to the scan area; calculating an image quality evaluation value of an image constructed by the image constructing unit based on data acquired by the OCT scan applied to the scan area; detecting a corner angle image by analyzing the image constructed by the image constructing unit based on the data acquired by the OCT scan applied to the scan area; performing a judgement of whether the corner angle image is located within a first area in an image frame; and performing control of the OCT optical system to apply an OCT scan of a predetermined pattern to the anterior segment, if the image quality evaluation value is equal to or greater than a predetermined threshold and the corner angle image is judged to be located within the first area. 
     The eighteenth aspect of some embodiment examples is a program causing a computer to execute the method of the seventeenth aspect. 
     The nineteenth aspect of some embodiment examples is a computer-readable non-transitory recording medium storing the program of the eighteenth aspect. 
     Effect of the Invention 
     According to the embodiment example, a preparatory operation for applying OCT to an anterior segment of a living eye can be automated, and the burden on the subject and the examiner can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating an example of the configuration of the ophthalmic apparatus according to the embodiment example. 
         FIG. 2  is a schematic diagram illustrating an example of the configuration of the ophthalmic apparatus according to the embodiment example. 
         FIG. 3A  is a schematic diagram illustrating an example of the configuration of the ophthalmic apparatus according to the embodiment example. 
         FIG. 3B  is a schematic diagram illustrating an example of the configuration of the ophthalmic apparatus according to the embodiment example. 
         FIG. 4A  is a schematic diagram for describing an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 4B  is a schematic diagram for describing an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 4C  is a schematic diagram for describing an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 5  is an OCT image for describing an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 6  is a schematic diagram for describing an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 7A  is a flowchart illustrating an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 7B  is a flowchart illustrating an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 8  is a schematic diagram illustrating an example of the configuration of the ophthalmic apparatus according to the embodiment example. 
         FIG. 9A  is a schematic diagram for describing an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 9B  is a schematic diagram for describing an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 9C  is a schematic diagram for describing an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 9D  is a schematic diagram for describing an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 10  is an OCT image for describing an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 11  is a schematic diagram for describing an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 12  is a schematic diagram for describing an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 13  is a schematic diagram for describing an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 14A  is a flowchart illustrating an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
         FIG. 14B  is a flowchart illustrating an operation that can be performed by the ophthalmic apparatus according to the embodiment example. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     An ophthalmic apparatus, a method of controlling the same, a program, and a recording medium according to some embodiment examples and aspects thereof will be described in detail with referring to the drawings. The ophthalmic apparatus according to the embodiment examples is used to acquire data of a subject&#39;s eye in an optical manner (i.e., using light, in other words, using optical technology and technique). In particular, the ophthalmic apparatus according to the embodiment examples is capable of imaging the anterior eye segment using OCT techniques. 
     The ophthalmic apparatus according to the embodiment examples may have other functions in addition to the OCT function (optical coherence tomography apparatus). Examples of such additional functions include an anterior segment imaging function, a fundus imaging function, an ocular axial length measurement function, an ocular refractive power measurement function, an ocular aberration measurement function, a corneal shape measurement function, and a visual field measurement function. It should be noted that the additional functions are not limited to these examples and may be any kind of ophthalmic examination functions, or may be any examination functions usable in any medical departments other than ophthalmology. 
     While the following embodiment examples describe an ophthalmic apparatus (an ophthalmic imaging apparatus) of a combination of swept source OCT and a fundus camera, embodiment examples are not limited thereto. The type of OCT applicable to embodiment examples is not limited to swept source OCT, and may be spectral domain OCT, for example. 
     Swept source OCT is an imaging technique performed by: splitting light emitted from a wavelength tunable light source into measurement light and reference light; superposing return light of the measurement light returning from the object with the reference light to generate interference light; detecting the interference light by a photodetector such as a balanced photodiode; and applying Fourier transform and other processes to the detection data acquired according to the wavelength sweeping and the measurement light scanning. 
     Spectral domain OCT is an imaging technique performed by: splitting light from a low coherence light source into measurement light and reference light; superposing return light of the measurement light returning from the object with the reference light to generate interference light; detecting the spectral distribution of the interference light using a spectrometer; and applying Fourier transform and other processes to the spectral distribution detected. 
     As described above, swept source OCT is an OCT technique for acquiring a spectral distribution by time division, and spectral domain OCT is an OCT technique for acquiring a spectral distribution by space division. In addition, OCT techniques applicable to embodiment examples are not limited to these two, and may be any other morphological (structural) imaging OCT techniques such as time domain OCT or any functional imaging OCT techniques such as polarization OCT or blood flow measurement OCT. 
     In addition to such an ophthalmic apparatus, the following embodiment examples include descriptions of a method of controlling an ophthalmic apparatus, a program that causes an ophthalmic apparatus including a computer or a computer connected to an ophthalmic apparatus to execute such a control method, and a recording medium that stores such a program. 
     Further, the following embodiment examples include descriptions of an exemplary embodiment of a series of preparatory operations applicable to corneal OCT and an exemplary embodiment of a series of preparatory operations applicable to corner angle OCT. Furthermore, the following embodiment examples include descriptions of control for switching the preparatory operations depending on sites of an eye to which OCT is applied. The sites to which OCT is applied may typically be any two or more of the cornea, the corner angle, and the eye fundus; however, the sites to which OCT is applied may include other sites. 
     In the present disclosure, “image data” and an “image” displayed based thereon may not be distinguished from one another unless otherwise mentioned. Likewise, a site or tissue of the subject&#39;s eye and an image representing the site or the tissue may not be distinguished from one another unless otherwise mentioned. 
     &lt;Embodiment Example Applicable to Corneal OCT&gt; 
       FIG. 1  shows an embodiment example applicable to corneal OCT. The ophthalmic apparatus  1  includes the fundus camera unit  2 , the OCT unit  100 , and the arithmetic and control unit  200 . The fundus camera unit  2  includes optical systems and mechanisms for acquiring front images of the subject&#39;s eye E, and optical systems and mechanisms for performing an OCT scan. The OCT unit  100  includes optical systems and mechanisms for performing an OCT scan. The arithmetic and control unit  200  includes a storage, and one or more processors configured to execute various kinds of processes (e.g., calculations, operations, and controls). 
     The ophthalmic apparatus  1  includes a lens unit for switching sites of the subject&#39;s eye to which an OCT scan is applied. More specifically, the ophthalmic apparatus  1  of the present embodiment example includes the anterior segment OCT attachment  400  for applying an OCT scan to an anterior segment. For example, the anterior segment OCT attachment  400  may have the same configuration as that of the optical unit disclosed in Japanese Unexamined Patent Application Publication No. 2015-160103. 
     As shown in  FIG. 1 , the anterior segment OCT attachment  400  can be disposed between the objective lens  22  and the subject&#39;s eye E. When the anterior segment OCT attachment  400  is placed in the optical path, the ophthalmic apparatus  1  can apply an OCT scan to the anterior eye segment. On the other hand, when the anterior segment OCT attachment  400  is retracted from the optical path, the ophthalmic apparatus  1  can apply an OCT scan to the posterior eye segment. The insertion and removal of the anterior segment OCT attachment  400  is carried out manually or automatically. 
     Another embodiment example may be configured to apply an OCT scan to a posterior eye segment when an attachment is placed in the optical path, and apply an OCT scan to an anterior eye segment when the attachment is retracted from the optical path. Further, the sites switched by the attachment are not limited to the posterior eye segment and the anterior eye segment, and may be any sites of an eye. The configurations for switching the sites to which an OCT scan is applied are not limited to the attachments described above, and the following options may be adopted: a configuration including a lens movable along an optical path; or a configuration including a lens insertable into and removable from an optical path. 
     The “processor” as used in the present disclosure is hardware for executing a set of commands described in a software program. Such a processor typically includes an arithmetic unit, a resistor, a peripheral circuit, and the like. For example, the processor refers to a circuit or an electrical circuit configuration (or circuitry) such as a central processing unit (CPU), a graphics processing unit (GPU), a micro-processing unit (MPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), or a field programmable gate array (FPGA)), or the like. For example, the processor loads a program stored in storage hardware (e.g., a memory circuit or a storage), and executes the program, thereby implementing the functions according to a corresponding embodiment example. The processor may include at least part of the storage hardware. 
     &lt;Fundus Camera Unit  2 &gt; 
     The fundus camera unit  2  is provided with optical systems for photographing the fundus Ef of the subject&#39;s eye E. Digital images of the fundus Ef (referred to as fundus images, fundus photographs, or the like) obtained by the fundus camera unit  2  are, in general, front images such as observation images and photographed images. An observation image is obtained by capturing a moving image using near-infrared light. A photographed image is a still image obtained by using flash light in the visible range. 
     The fundus camera unit  2  includes the illumination optical system  10  and the photography optical system  30 . The illumination optical system  10  projects illumination light onto the subject&#39;s eye E. The photography optical system  30  detects the return light of the illumination light projected onto the subject&#39;s eye E. The measurement light incident from the OCT unit  100  is directed to the subject&#39;s eye E through the optical path in the fundus camera unit  2 . The return light of the measurement light projected onto the subject&#39;s eye E (e.g., the fundus Ef) is directed to the OCT unit  100  through the same optical path in the fundus camera unit  2 . 
     The light output from the observation light source  11  of the illumination optical system  10  (referred to as observation illumination light) is reflected by the concave mirror  12 , passes through the condenser lens  13 , and becomes near-infrared light after passing through the visible cut filter  14 . Further, the observation illumination light is once converged at a location near the photographing light source  15 , reflected by the mirror  16 , passes through the relay lens system  17 , the relay lens  18 , the diaphragm  19 , and the relay lens system  20 , and is directed to the aperture mirror  21 . Then, the observation illumination light is reflected on the peripheral part (i.e., the surrounding area of the aperture part) of the aperture mirror  21 , penetrates the dichroic mirror  46 , and is refracted by the objective lens  22 , thereby illuminating the subject&#39;s eye E (the fundus Ef thereof). The return light of the observation illumination light from the subject&#39;s eye E is refracted by the objective lens  22 , penetrates the dichroic mirror  46 , passes through the aperture part formed in the center area of the aperture mirror  21 , passes through the dichroic mirror  55 , travels through the photography focusing lens  31 , and is reflected by the mirror  32 . Further, the return light passes through the half mirror  33 A, is reflected by the dichroic mirror  33 , and forms an image on the light receiving surface of the image sensor  35  by the imaging lens  34 . The image sensor  35  detects the return light at a predetermined frame rate (capture rate). Note that the focus of the photography optical system  30  is adjusted to match the fundus Ef or the anterior segment. 
     The light output from the photographing light source  15  (referred to as photographing illumination light) passes through the same route as that of the observation illumination light and is projected onto the fundus Ef. The return light of the photographing illumination light from the subject&#39;s eye E passes through the same route as that of the return light of the observation illumination light, is guided to and passes through the dichroic mirror  33 , is reflected by the mirror  36 , and forms an image on the light receiving surface of the image sensor  38  by the imaging lens  37 . 
     The liquid crystal display (LCD)  39  displays a fixation target (i.e., a fixation target image). Part of the light beam output from the LCD  39  is reflected by the half mirror  33 A, reflected by the mirror  32 , travels through the photography focusing lens  31  and the dichroic mirror  55 , and passes through the aperture part of the aperture mirror  21 . The light beam having passed through the aperture part of the aperture mirror  21  penetrates the dichroic mirror  46 , and is refracted by the objective lens  22 , thereby being projected onto the fundus Ef. Fixation targets are typically used for guidance and fixation of the line of sight. The direction in which the line of sight of the subject&#39;s eye E is guided (and fixed), that is, the direction in which the fixation of the subject&#39;s eye E is urged is referred to as a fixation position. 
     The fixation position can be changed by changing the display position of the fixation target image on the screen of the LCD  39 . Examples of fixation positions include a fixation position for acquiring an image centered on the macula, a fixation position for acquiring an image centered on the optic nerve head, a fixation position for acquiring an image centered on a position between the macula and the optic nerve head (i.e., the fundus center position), and a fixation position for acquiring an image of a site far away from the macula (i.e., a peripheral position of the fundus). 
     A user interface such as a graphical user interface (GUI) for designating at least one of such typical fixation positions can be provided. Further, a user interface such as a GUI for manually changing the fixation position (i.e., the display position of the fixation target) can be provided. In addition, it is also possible to apply a configuration in which the fixation position is automatically set. 
     The configuration of presenting fixation targets to the subject&#39;s eye E for changing fixation positions is not limited to display devices such as LCD. For example, a device that has light emitting elements (e.g., light emitting diodes) disposed in a matrix-like arrangement (referred to as a fixation matrix) can be adopted in place of a display device. In this case, fixation positions of the subject&#39;s eye E by the fixation target can be changed by lighting one (or more) of the light emitting elements in a selective manner. As another example, a device provided with one or more movable light emitting elements can generate the fixation target capable of changing fixation positions. 
     The alignment optical system  50  generates an alignment indicator used for the alignment of the optical system with respect to the subject&#39;s eye E. The alignment light output from the light emitting diode (LED)  51  travels through the diaphragm  52 , the diaphragm  53 , and the relay lens  54 , is reflected by the dichroic mirror  55 , passes through the aperture part of the aperture mirror  21 , penetrates the dichroic mirror  46 , and is projected onto the subject&#39;s eye E via the objective lens  22 . The return light of the alignment light from the subject&#39;s eye E passes through the same route as that of the return light of the observation illumination light and is guided to the image sensor  35 . Based on the received image (referred to as the alignment indicator image), manual alignment and/or automatic alignment can be performed. 
     Alignment methods applicable to embodiment examples are not limited to the above method using an alignment indicator. For example, an alignment method may be applied using trigonometry and an anterior segment camera capable of photographing the anterior segment from two or more positions that are different from each other (see, for example, Japanese Unexamined Patent Application Publication No. 2013-248376 and Japanese Unexamined Patent Application Publication No. 2016-047094). This method is referred to as stereo alignment or the like. Alternatively, a method using an optical lever configured to project light onto the cornea from an oblique direction and detect the cornea reflection light in the opposite oblique direction can be applied (see, for example, Japanese Unexamined Patent Application Publication No. 2016-047094). Further, alignment may be performed by detecting a feature point (e.g., the center of the pupil) from an infrared observation image of the anterior segment. This method will be described later. 
     The focus optical system  60  generates a split indicator used for the focus adjustment with respect to subject&#39;s eye E. The focus optical system  60  is moved along the optical path of the illumination optical system  10  (referred to as the illumination optical path) in conjunction with the movement of the photography focusing lens  31  along the optical path of the photography optical system  30  (referred to as the photographing optical path). The reflection rod  67  is inserted into and removed from the illumination optical path. Before performing focus adjustment, the reflective surface of the reflection rod  67  is arranged in the slanted state in the illumination optical path. The focus light output from the LED  61  passes through the relay lens  62 , is split into two light beams by the split indicator plate  63 , passes through the two-hole diaphragm  64 . Then, the focus light is reflected by the mirror  65 , is converged on the reflective surface of the reflection rod  67  by the condenser lens  66 , and is reflected by the reflective surface. Further, the focus light travels through the relay lens  20 , is reflected by the aperture mirror  21 , and penetrates the dichroic mirror  46 , thereby being projected onto the subject&#39;s eye E via the objective lens  22 . The return light of the focus light from the subject&#39;s eye E (e.g., the fundus reflection light) passes through the same route as that of the return light of the alignment light and is guided to the image sensor  35 . Based on the received image (referred to as the split indicator image), manual focusing and/or automatic focusing can be performed. 
     The diopter correction lenses  70  and  71  can be selectively inserted into the photographing optical path between the aperture mirror  21  and the dichroic mirror  55 . The diopter correction lens  70  is a positive lens (convex lens) for correcting high hyperopia. The diopter correction lens  71  is a negative lens (concave lens) for correcting high myopia. 
     The dichroic mirror  46  couples the optical path for photography and the optical path for OCT scanning (measurement arm). The dichroic mirror  46  reflects the light of wavelength bands used for OCT scanning and transmits the light of wavelength bands used for photography. The measurement arm is formed by, listed from the OCT unit  100  side, the collimator lens unit  40 , the retroreflector  41 , the dispersion compensation member  42 , the OCT focusing lens  43 , the optical scanner  44 , and the relay lens  45 . 
     The retroreflector  41  is movable along the optical path of the measurement light LS incident on the retroreflector  41 , whereby the length of the measurement arm is changed. The change in the length of the measurement arm can be utilized for operations such as optical path length correction according to axial length and interference condition adjustment. 
     The dispersion compensation member  42  acts to eliminate the difference between the dispersion characteristics of the measurement light LS and that of the reference light LR, together with the dispersion compensation member  113  (described later) arranged in the reference arm. 
     The OCT focusing lens  43  is moved along the measurement arm in order to perform the focus adjustment of the measurement arm. Note that the movements of the photography focusing lens  31 , the focus optical system  60 , and the OCT focusing lens  43  may be controlled in an interlocking manner. 
     The optical scanner  44  is placed at a position substantially optically conjugate with respect to the pupil of the subject&#39;s eye E when the anterior segment OCT attachment  400  is removed from the optical path. On the other hand, the optical scanner  44  is placed at a position substantially optically conjugate with respect to the anterior segment of the subject&#39;s eye E (e.g., the cornea, the anterior chamber, the pupil, or the crystalline lens) when the anterior segment OCT attachment  400  is placed in the optical path. The optical scanner  44  is configured to deflect the measurement light LS guided through the measurement arm. An example of the optical scanner  44  is provided by a galvano scanner configured to be capable of two dimensional scanning. Typically, the optical scanner  44  includes a one dimensional scanner for deflecting the measurement light in the +x and −x directions (x-scanner), and another one dimensional scanner for deflecting the measurement light in the +y and −y directions (y-scanner). When such a configuration is employed, for example, either one of the x-scanner and the y-scanner may be placed at the optically conjugate position described above. Alternatively, the optically conjugate positions may be placed between the x-scanner and the y-scanner. 
     &lt;OCT Unit  100 &gt; 
     The exemplary OCT unit  100  shown in  FIG. 2  is provided with the optical system for performing swept source OCT. The optical system includes an interference optical system. The interference optical system is configured to split light emitted from a wavelength tunable light source into measurement light and reference light, superpose the return light of the measurement light projected onto the subject&#39;s eye E with the reference light having traveled through the reference optical path, thereby yielding interference light. Then, the interference optical system detects the interference light. The data (i.e., a detection signal, an interference signal) obtained by detecting the interference light is a signal representing the spectrum of the interference light and is sent to the arithmetic and control unit  200 . 
     The light source unit  101  includes, for example, a near-infrared wavelength tunable laser configured to vary wavelengths of emitted light at high speed. The low coherence light L 0  output from the light source unit  101  is guided to the polarization device  103  through the optical fiber  102 , and the polarization state (polarization condition) of the light L 0  is regulated. Further, the light L 0  with regulated polarization state is guided to the fiber coupler  105  through the optical fiber  104  and is split into the measurement light LS and the reference light LR. The optical path of the measurement light LS is referred to as a measurement arm, and the optical path of the reference light LR is referred to as a reference arm. 
     The reference light LR generated by the fiber coupler  105  is guided through the optical fiber  110  to the collimator  111 , is converted into a parallel light beam, travels through the optical path length correction member  112  and the dispersion compensation member  113 , and is guided to the retroreflector  114 . The optical path length correction member  112  acts to match the optical path length of the reference light LR and that of the measurement light LS with each other. The dispersion compensation member  113  acts to eliminate the difference between the dispersion characteristics of the reference light LR and that of the measurement light LS with each other, together with the dispersion compensation member  42  arranged in the measurement arm. The retroreflector  114  is movable along the optical path of the reference light LR incident on the retroreflector  114 . With this, the length of the reference arm is changed. The change in the length of the reference arm may be utilized for operations such as optical path length correction according to axial length and interference condition adjustment. 
     After passing through the retroreflector  114 , the reference light LR travels through the dispersion compensation member  113  and the optical path length correction member  112 , is converted from a parallel light beam to a convergent light beam by the collimator  116 , and is incident on the optical fiber  117 . The reference light LR having entered the optical fiber  117  is guided to the polarization device  118 , and the polarization state of the reference light LR is regulated. Then, the reference light LR is guided to the attenuator  120  through the optical fiber  119 , and the light amount of the reference light LR is regulated. Subsequently, the reference light LR is guided to the fiber coupler  122  through the optical fiber  121 . 
     The polarization device  118  may be any type of polarization controlling device such as a bulk type, a paddle type, or an in-line type. A bulk type polarization controlling device is, typically, configured to change the polarization state with a series of optical element groups such as a half-wave plate, a quarter-wave plate, a lens, or the like. A paddle type polarization controlling device is, typically, configured to change the polarization state by utilizing birefringence induced by rotating a plurality of paddles, each of which forms an optical fiber into a coil-like shape. An in-line polarization controlling device is, typically, configured to change the polarization state by utilizing birefringence induced by applying an external force to an optical fiber or rotating an optical fiber. Likewise, the polarization device  103  may be any type of polarization controlling device. 
     Meanwhile, the measurement light LS generated by the fiber coupler  105  is guided to the collimator lens unit  40  through the optical fiber  127  and is converted to a parallel light beam. Then, the measurement light LS passes through the retroreflector  41 , the dispersion compensation member  42 , the OCT focusing lens  43 , the optical scanner  44 , and the relay lens  45 , and then reaches the dichroic mirror  46 . The measurement light LS is reflected by the dichroic mirror  46 , is refracted by the objective lens  22 , and is projected onto the subject&#39;s eye E. The measurement light LS is reflected and scattered at various depths of the subject&#39;s eye E. The return light of the measurement light LS returning from the subject&#39;s eye E travels along the measurement arm in the opposite direction to the measurement light LS traveling toward the subject&#39;s eye E, is directed to the fiber coupler  105 , and then reaches the fiber coupler  122  via the optical fiber  128 . 
     The fiber coupler  122  superposes the measurement light LS incident through the optical fiber  128  with the reference light LR incident through the optical fiber  121 , to generate interference light. The fiber coupler  122  splits the generated interference light at a predetermined splitting ratio (e.g., 1 to 1) to generate a pair of interference light LC. The pair of interference light LC is guided to the detector  125  through the optical fibers  123  and  124 , respectively. 
     The detector  125  includes, for example, a balanced photo diode. The balanced photodiode includes a pair of photodetectors for respectively detecting the pair of the interference light LC. The balanced photodiode outputs a difference between a pair of detection signals corresponding to the pair of the interference light LC respectively obtained by the pair of photodetectors. The detector  125  sends the output (difference signal) to the data acquisition system (DAQ)  130 . 
     The clock KC is supplied from the light source unit  101  to the data acquisition system  130 . The clock KC is generated in the light source unit  101  in synchronization with the output timings of wavelengths varied over a predetermined wavelength range by the wavelength tunable type light source. For example, the light source unit  101  is configured to split the light L 0  of each output wavelength to generate two pieces of split light, apply an optical delay to one of the two pieces of split light, combine the resulting two pieces of split light, detect the combined light, and generate the clock KC based on the detection signal of the combined light. The data acquisition system  130  performs sampling of the signal (difference signal) input from the detector  125  based on the clock KC. The data acquisition system  130  sends the data obtained by the sampling to the arithmetic and control unit  200 . 
     While both an element for changing the measurement arm length (e.g., the retroreflector  41 ) and an element for changing the reference arm length (e.g., the retroreflector  114  or a reference mirror) are provided in the present embodiment example, only one of these two elements may be provided in some other embodiment examples. Further, elements for changing the difference between the measurement arm length and the reference arm length (i.e., optical path length difference) are not limited to the elements in the present embodiment example, and any type of element (e.g., any type of optical member, any type of mechanism) may be employed. 
     &lt;Arithmetic and Control Unit  200 &gt; 
     The arithmetic and control unit  200  controls each part (each element) of the ophthalmic apparatus  1 . Further, the arithmetic and control unit  200  executes various kinds of arithmetic processes. For example, the arithmetic and control unit  200  applies signal processing such as Fourier transform on the spectral distribution based on a sampling data group collected by the data acquisition system  130  for each series of wavelength scanning (for each A-line), to create reflection intensity profiles respectively for A-lines. Furthermore, the arithmetic and control unit  200  applies imaging processing to the reflection intensity profiles for the A-lines to construct image data. Arithmetic processes for the image data construction are the same as those of conventional swept source OCT. 
     The arithmetic and control unit  200  includes, for example, a processor, random access memory (RAM), read only memory (ROM), hard disk drive, and communication interface. A storage such the hard disk drive stores various kinds of computer programs. The computer programs are executed by the processor of the arithmetic and control unit  200 . The arithmetic and control unit  200  may include an operation device, an input device, a display device, etc. 
     &lt;User Interface  240 &gt; 
     The user interface  240  includes the display device  241  and the operation device  242 . The display device  241  includes the display  3 . The operation device  242  includes various kinds of operation devices and input devices. The user interface  240  may include a device having both the display function and the operation function, such as a touch panel display. Some embodiment examples may be configured not to include at least part of the user interface  240 . For example, the display device may be a peripheral device connected to the ophthalmic apparatus. Further, at least part of the operation device and/or at least a part of the input device may be a peripheral device connected to the ophthalmic apparatus. 
     &lt;Processing System&gt; 
       FIG. 3A  and  FIG. 3B  show a configuration example of the processing system of the ophthalmic apparatus  1 . The controller  210 , the image constructing unit  220 , and the data processor  230  may be provided in the arithmetic and control unit  200 , for example. 
     &lt;Controller  210 &gt; 
     The controller  210  includes a processor and controls each part (each element) of the ophthalmic apparatus  1 . The controller  210  includes the main controller  211  and the memory  212 . 
     &lt;Main Controller  211 &gt; 
     The main controller  211  controls each element of the ophthalmic apparatus  1  (including the elements shown in  FIG. 1  to  FIG. 3B ). The function of the main controller  211  may typically be implemented by the cooperation of hardware including a processor and software including a control program. At least part of the functions of the main controller  211  may be implemented by means of hardware including a control circuit. 
     The photography focusing lens  31  disposed in the photography optical path and the focus optical system  60  disposed in the illumination optical path are moved in an integral or interlocking manner by a photography focus driver (not shown in the drawings) under control of the main controller  211 . The retroreflector  41  disposed in the measurement arm is moved by the retroreflector driver (RR driver)  41 A under control of the main controller  211 . The OCT focusing lens  43  disposed in the measurement arm is moved by the OCT focus driver  43 A under control of the main controller  211 . The optical scanner  44  provided in the measurement arm operates under control of the main controller  211 . The retroreflector  114  disposed in the reference arm is moved by the retroreflector driver (RR driver)  114 A under control of the main controller  211 . The polarization device  118  disposed in the reference arm operates under control of the main controller  211 . Similarly, the polarization device  103  disposed in the optical path of the light L 0  operates under control of the main controller  211 . Each of the mechanisms described as examples here typically includes an actuator that operates under control of the main controller  211 . The same applies to any mechanisms and any elements not described here. 
     The movement mechanism  150  is configured to move, for example, the fundus camera unit  2  in a three dimensional manner. In a typical example, the movement mechanism  150  includes the followings: an x-stage movable in the +x and −x directions (i.e., left and right directions); an x-movement mechanism that moves the x-stage; a y-stage movable in the +y and −y directions (i.e., up and down directions); a y-movement mechanism that moves the y-stage; a z-stage movable in the +z and −z directions (i.e., depth direction); and a z-movement mechanism that moves the z-stage. Each of the movement mechanisms described here includes an actuator such as a pulse motor that operates under control of the main controller  211 . At least part of the measurement arm (including at least the objective lens  22 ) is directly or indirectly placed on the stages. Typically, the fundus camera unit is placed directly or indirectly on the stages. 
     &lt;Memory  212 &gt; 
     The memory  212  stores various kinds of data. Examples of the data stored in the memory  212  include OCT image data, anterior segment image data, fundus image data, and subject&#39;s eye information. The subject&#39;s eye information may include subject information such as patient identifiers and patient&#39;s names, identifiers for the left eye and the right eye, and electronic medical record data, for example. Further, the memory  212  may store various kinds of templates, various kinds of parameter values, and various kinds of software for operating the ophthalmic apparatus  1 . 
     The memory  212  typically includes a storage having a relatively large capacity such as a hard disk. Note that various kinds of data may be stored in a storage or an information processing apparatus on a communication line. If this is the case, the memory  212  does not need to include the storage having a relatively large capacity. The same applies if a relatively large capacity storage is employed as a peripheral device of the ophthalmic apparatus  1 . 
     &lt;Image Constructing Unit  220 &gt; 
     The image constructing unit  220  constructs OCT image data based on data acquired by the data acquisition system  130 . The function of the image constructing unit  220  may typically be implemented by the cooperation of hardware including a processor and software including an image constructing program. At least part of the function of the image constructing unit  220  may be implemented by hardware including an image constructing circuit. 
     The image constructing unit  220  constructs cross sectional image data based on data acquired by the data acquisition system  130 . The image construction processing includes signal processing such as noise elimination (noise reduction), filtering, fast Fourier transform (FFT), and other processes as in conventional swept source OCT. 
     Image data constructed by the image constructing unit  220  is a data set including a group of a plurality of pieces of image data constructed by applying imaging processing to reflection intensity profiles at corresponding A-lines arranged in the area to which an OCT scan is applied. Each of the A-lines is a scan line lying along the z direction. 
     An OCT scan applied to an A-line is referred to as an A-scan. Image data obtained by an A-scan may be called A-scan image data. Further, the z direction may be referred to as the A-scan direction. 
     A collection of a plurality of A-scans arranged in a one dimensional direction (arbitrary direction in the xy-plane) orthogonal to the A-scan direction is referred to as a B-scan. The one dimensional direction orthogonal to the A-scan direction may be referred to as the B-scan direction. Image data obtained by a B-scan may be referred to as B-scan image data. 
     Image data constructed by the image constructing unit  220  is, for example, one or more pieces of A-scan image data, one or more pieces of B-scan image data, or three dimensional image data. Three dimensional image data is image data represented by a three dimensional coordinate system, and typical examples thereof include stack data and volume data. Stack data is constructed by embedding a plurality of pieces of B-scan image data in a single three dimensional coordinate system. Volume data, also referred to as voxel data, is constructed by applying voxelization processing to stack data. 
     The image constructing unit  220  may be configured to apply image processing to image data using any known image processing technique. For example, the image constructing unit  220  may construct new image data by applying rendering to three dimensional image data. Examples of the rendering method include volume rendering, maximum intensity projection (MIP), minimum intensity projection (MinIP), surface rendering, and multi planar reconstruction (MPR). Further, the image constructing unit  220  may be configured to construct projection data by projecting three dimensional image data in the z direction (i.e., the A-line direction, the depth direction). In addition, the image constructing unit  220  may be configured to construct a shadowgram by projecting part of three dimensional image data in the z direction. Here, the part of the three dimensional image data projected for the shadowgram construction is extracted by using segmentation, for example. 
     &lt;Data Processor  230 &gt; 
     The data processor  230  performs various kinds of data processing. For example, the data processor  230  may be configured to apply image processing and/or analysis processing to OCT image data, and/or, apply image processing and/or analysis processing to observation image data or photographed image data. The function of the data processor  230  may typically be implemented by the cooperation of hardware including a processor and software including a data processing program. At least part of the function of the data processor  230  may be implemented by hardware including a data processing circuit. 
     &lt;Details of Configuration Example of Processing System&gt; 
       FIG. 3B  shows an example of the configurations of the controller  210  and the data processor  230 . 
     &lt;Example of the Controller  210 &gt; 
     The controller  210  illustrated in  FIG. 3B  includes the movement controller  2101 , the scan controller  2102 , the polarization controller  2103 , and the display controller  2104 . 
     The movement controller  2101  executes control of the movement mechanism  150 . The scan controller  2102  executes control of elements for performing the OCT scan, such as the light source unit  101  and the optical scanner  44 . The polarization controller  2103  executes control of the polarization device  118 . Further, the polarization controller  2103  may be configured to execute control of the polarization device  103  in addition to or instead of the control of the polarization device  118 . The display controller  2104  executes control of the user interface  240  (the display device  241 ). 
     The function of the movement controller  2101 , the function of the scan controller  2102 , the function of the polarization controller  2103 , and the function of the display controller  2104  each may typically be implemented by the cooperation of hardware including a processor and software including a control program. At least part of the functions of any of the movement controller  2101 , the scan controller  2102 , the polarization controller  2103 , and the display controller  2104  may be implemented by hardware including a control circuit. 
     The main controller  211  includes the movement controller  2101 , the scan controller  2102 , the polarization controller  2103 , and the display controller  2104 . Any of the movement controller  2101 , the scan controller  2102 , the polarization controller  2103 , and the display controller  2104  may include storage hardware (i.e., the memory  212 ). Processing executed by the movement controller  2101 , processing executed by the scan controller  2102 , processing executed by the polarization controller  2103 , and processing executed by the display controller  2104  will be described later. 
     &lt;Example of the Data Processor  230 &gt; 
     The data processor  230  illustrated in  FIG. 3B  includes the destination determining processor  231 , the artifact detecting processor  232 , the corneal image detecting processor  233 , the position judging processor  234 , the image quality evaluating processor  235 , and the artifact eliminating processor  236 . 
     The function of the destination determining processor  231 , the function of the artifact detecting processor  232 , the function of the corneal image detecting processor  233 , the function of the position judging processor  234 , the function of the image quality evaluating processor  235 , and the function of the artifact eliminating processor  236  each may typically be implemented by the cooperation of hardware including a processor and software including a data processing program. At least part of the functions of any of the destination determining processor  231 , the artifact detecting processor  232 , the corneal image detecting processor  233 , the position judging processor  234 , the image quality evaluating processor  235 , and the artifact eliminating processor  236  may be implemented by hardware including a data processing circuit. Any of the destination determining processor  231 , the artifact detecting processor  232 , the corneal image detecting processor  233 , the position judging processor  234 , the image quality evaluating processor  235 , and the artifact eliminating processor  236  may include storage hardware. 
     The followings are descriptions of each of the elements included in the data processor  230 . 
     &lt;Destination Determining Processor  231 &gt; 
     The ophthalmic apparatus  1  of the present embodiment example is capable of performing anterior eye segment imaging using the fundus camera unit  2 . For example, the ophthalmic apparatus  1  is capable of capturing an infrared moving image of the anterior segment of an eye using the observation illumination light and the image sensor  35 . 
     The destination determining processor  231  analyzes an anterior segment image acquired by the fundus camera unit  2  to determine a destination (goal of movement) of an OCT optical system. The movement controller  2101  controls the movement mechanism  150  based on the destination determined by the destination determining processor  231 . 
     The destination in the present embodiment example may be, for example, coordinates (x, y, z) representing a position of the fundus camera unit  2  moved by the movement mechanism  150 , or a control parameter of the movement mechanism  150 . As an example of the latter, if the actuator of the movement mechanism  150  is a pulse motor, the control parameter may include the number of pulses supplied to the pulse motor. 
     The types of information determined as a destination by the destination determining processor  231  are not limited to the above examples. The type of information representing a destination is determined in advance, for example, according to the configuration of hardware such as a movement mechanism and/or the configuration of software for movement control. 
     The OCT optical system is an optical system for applying an OCT scan to the subject&#39;s eye E (and movement mechanisms and drive mechanisms for operating elements of the OCT optical system). The OCT optical system of the present embodiment example includes at least a series (set) of elements composing the measurement arm in the fundus camera unit  2 . Specifically, the series of elements includes the collimator lens unit  40 , the retroreflector  41 , the dispersion compensation member  42 , the OCT focusing lens  43 , the optical scanner  44 , the relay lens  45 , the dichroic mirror  46 , and the objective lens  22 . The present embodiment example is configured to move, by the movement mechanism  150 , the fundus camera unit  2  including the OCT optical system thus configured. 
     A description will be given of a typical example of destination determination. The ophthalmic apparatus  1  performs infrared moving image photography of the anterior segment of the subject&#39;s eye E using the fundus camera unit  2 . In parallel with the infrared moving image photography, the destination determining processor  231  sequentially analyzes a plurality of anterior segment images (a frame group (group of frames) of a moving image) acquired by the fundus camera unit  2  in a successive manner, thereby acquiring time series data of destinations of the OCT optical system. 
     The time series destination data reflects eye movement of the subject&#39;s eye E and changes in the relative position between the subject&#39;s eye E and the fundus camera unit  2 . Further, changes in the pupil diameter may affect the time series destination data. 
     Note that it is not necessary for the destination determining processor  231  to analyze all the anterior segment images acquired by the fundus camera unit  2 . For example, the number of anterior segment images to be analyzed by the destination determining processor  231  may be reduced by applying a thinning process or a selection process. 
     A plurality of destinations acquired by the destination determining processor  231  in parallel with the infrared moving image photography of the anterior segment is sequentially sent to the movement controller  2101 . The movement controller  2101  executes control of the movement mechanism  150  based on the destinations sequentially input from the destination determining processor  231 . The control of the movement mechanism  150  is carried out as real time processing. 
     Such an exemplary process allows the fundus camera unit  2  to be moved in accordance with the time series change in the destinations represented by the time series destination data. As a result of this, the position of the OCT optical system can be automatically regulated according to eye movement of the subject&#39;s eye E (tracking). 
     The OCT optical system may start application of an OCT scan to the anterior segment of the subject&#39;s eye E at an arbitrary timing after the control of the movement mechanism  150  performed by the movement controller  2101 . A specific example of the OCT scan application timing will be described later. 
     An example will be described of the destination determination processing performed by the destination determining processor  231 .  FIG. 4A  shows an example of an anterior segment image acquired by the fundus camera unit  2 . The anterior segment image  500  contains the pupil image  510  corresponding to the pupil of the subject&#39;s eye E and the iris image  520  corresponding to the iris. Here, the pupil image  510  is shown as an image region indicated by diagonal lines, and the iris image  520  is shown as an image region indicated by horizontal lines. 
     The destination determining processor  231  identifies at least one of the pupil image  510  and the iris image  520  by analyzing the anterior segment image  500 . The analysis may include, for example, pixel-value-based thresholding and/or pattern detection. 
     A description will be given of a specific example of the thresholding. Since the pixel values of an anterior segment image of the present embodiment example are represented by the brightness gradation, the destination determining processor  231  can detect the pupil image  510  by identifying pixels whose brightness values are smaller than a first threshold determined in advance. The detection of the iris image  520  may employ a second threshold predetermined to be larger than the first threshold. Note that at least one of the first threshold and the second threshold may be a default value, or a relative value determined according to an arbitrary attribute and/or an arbitrary condition such as an anterior segment image subjected to be processed. As an example, the relative value may be a threshold determined on the basis of the brightness distribution, such as a brightness histogram, of an anterior segment image. 
     A description will be given of a specific example of the pattern detection. Utilizing the fact that the shape of the contour (outer edge, edge) of the pupil is substantially circular or substantially elliptical, the destination determining processor  231  may detect the pupil image  510  by identifying a region whose edge is of a substantially circular shape or a substantially elliptical shape. The same applies to the detection of the iris image  520 . In the case of detecting both the pupil image  510  and the iris image  520 , the destination determining processor  231  may be configured to first detect two substantially circular or substantially elliptical edges that are arranged substantially concentrically, and then set the image region whose outer edge is the inner one of the two detected edges as the pupil image  510 , and set an image region of substantially annular shape surrounded by the inner edge and the outer edge as the iris image  520 . 
     Note that techniques applicable to the analysis of anterior segment images are not limited to the above examples. For example, the anterior segment image analysis may include arbitrary image processing such as edge detection or binarization, and/or, may include arbitrary artificial intelligence techniques and/or arbitrary cognitive computing techniques. 
     The reference character “ 510   a”  in  FIG. 4B  denotes the outer edge of the pupil image  510 , and the reference character “ 520   a”  denotes the outer edge of the iris image  520 . Here, at least one of the pupil outer edge  510   a  and the iris outer edge  520   a  may be an approximate circle or an approximate ellipse. 
     The destination determining processor  231  identifies the pupil center of the anterior segment based on at least one of the pupil image  510  and the iris image  520 , for example, based on at least one of the pupil outer edge  510   a  and the iris outer edge  520   a.  The pupil center identification process may include at least one of the following processes, for example: a process of determining the center or the center of gravity of the pupil image  510 ; a process of determining the center or the center of gravity of the pupil outer edge  510   a;  a process of determining the center or the center of gravity of the iris image  520 ; and a process of determining the center or the center of gravity of the iris outer edge  520   a.  In the case where the pupil center identification process includes two or more of the four example processes, a statistical process (e.g., averaging) may be performed on two or more pupil center candidates respectively obtained by the two or more processes. Note that usable processes for pupil center determination is not limited to the above examples. 
     In the way described above, the destination determining processor  231  can detect the pupil center of the anterior segment of the subject&#39;s eye E and set the detected pupil center as a destination. The scan controller  2102  may set an area to which an OCT scan is applied such that the area passes through the pupil center detected. 
     The pattern of the OCT scan may be set in an arbitrary manner. For example, a line scan (B-scan), a cross scan, a multi-cross scan, a radial scan, or a three dimensional scan may be employed as the OCT scan pattern. The orientation of a line scan is optional. A cross scan is composed of two line scans orthogonal to each other. A multi-cross scan is composed of two line scan groups orthogonal to each other. Here, two or more line scans included in each of the line scan groups are parallel to one another. A radial scan is composed of a plurality of line scans arranged at equal angular intervals. A three dimensional scan is also referred to as a volume scan, and is typically a raster scan in which a large number of line scans are arranged in parallel to one another. 
     The scan controller  2102  may set an area to which an OCT scan is applied so that the center of the area is located at the pupil center detected by the destination determining processor  231 . An example is given in  FIG. 4C  of the case where a line scan is employed. As shown in  FIG. 4C , the scan controller  2102  may set an area to which the line scan  530  is applied such that the center of the line scan  530  and the pupil center  510   b  coincide with each other. Similarly, in the case where another scan pattern is employed, the scan controller  2102  may set an area to which an OCT scan is applied such that the center of a scan and the pupil center  510   b  coincide with each other. 
     The processing described above allows an OCT scan to be executed to pass substantially through the pupil center. The relative deviation between the xy-coordinates of the pupil center and the xy-coordinates of the corneal apex is not large in standard eyes. Therefore, the corneal apex or the vicinity thereof can be scanned if an OCT scan is performed with the pupil center as a scan target like the present embodiment example. 
     While the destination is set by detecting a feature point from an infrared observation image of the anterior segment in the present embodiment example, other methods may also be employed. For example, any other technique or method such as an alignment indicator, a stereo alignment, or an optical lever may be used to detect a feature point of the anterior segment. In the case of employing a technique or method capable of detecting the pupil center, the destination may be set to the pupil center detected. In the case of employing a technique or method capable of detecting the corneal apex, the destination may be set to the corneal apex detected. It should be noted that the feature point is not limited to the pupil center and the corneal apex. 
     &lt;Artifact Detecting Processor  232 &gt; 
     The artifact detecting processor  232  analyzes the OCT image constructed by the image constructing unit  220  to detect an artifact along the A-scan direction. 
       FIG. 5  shows an OCT image actually obtained using a B-scan (line scan) passing through the corneal apex. In the B-scan image  600 , a high brightness image region with a shape similar to part of an annulus represents a corneal cross section. The shape of the upper edge of the corneal cross sectional image is a substantially circular arc shape that is convex upward, and the uppermost part thereof corresponds to the corneal apex. Note that the downward direction on  FIG. 5  is the z-direction, that is, the A-scan direction. The reference character “ 610 ” denotes an A-line passing through the corneal apex. A band shaped or linear shaped artifact appears along the A-scan direction in the area  620  near the A-line. The occurrence of the artifact is attributable to reflection at the corneal apex and other factors. Such an artifact will be referred to as a longitudinal artifact. 
     The artifact detecting processor  232  may detect a longitudinal artifact based on a predetermined feature (characteristic) such as brightness, a position, or a shape. When brightness is taken into consideration, the artifact detecting processor  232  may detect an image region having brightness higher than a predetermined threshold as (a candidate of) a longitudinal artifact. When a position is taken into consideration, the artifact detecting processor  232  may detect the uppermost part of the upper edge of the corneal cross sectional image as the corneal apex and detect (a candidate of) a longitudinal artifact based on the position of the corneal apex detected. When a shape is taken into consideration, the artifact detecting processor  232  may detect a band shaped or linear shaped image region along the A-scan direction as (a candidate of) a longitudinal artifact. 
     The fact that the corneal apex has the highest brightness (see  FIG. 5 ) may be utilized for detecting a longitudinal artifact. Any known segmentation technique may also be used to detect a longitudinal artifact. The technique or method for detecting a longitudinal artifact is not limited to the above examples. The corneal image detecting processor  233  may be configured to perform detection of a corneal image (e.g., corneal cross sectional image), or detection of part of a corneal image (e.g., corneal apex, edge). 
     The movement controller  2101  may perform control of the movement mechanism  150  based on the result of the longitudinal artifact detection performed by the artifact detecting processor  232 . In other words, movement control of the OCT optical system may be performed by referring to a longitudinal artifact that occurs in an OCT image. 
     As a first example, the movement controller  2101  may be configured to execute control of the movement mechanism  150  so that the intensity of the longitudinal artifact occurring in the OCT image is maximized. The control performed by the present example may be implemented by repetitively performing a series of processes including OCT image acquisition, longitudinal artifact detection, and movement of the OCT optical system. 
     As a specific example thereof, the series of processes as follows may be executed while repetitively applying OCT scans of a predetermined pattern to the anterior segment to acquire time series OCT images. The artifact detecting processor  232  detects longitudinal artifacts in the OCT images sequentially acquired by the repetitive OCT scan application. The movement controller  2101  (or, another element of the controller  210 , another element of the artifact detecting processor  232 , or another element of the data processor  230 ; the same applies below) determines the intensities of the longitudinal artifacts detected. The movement controller  2101  controls the movement mechanism  150  to move the OCT optical system. 
     Further, the artifact detecting processor  232  detects a longitudinal artifact in an OCT image acquired after the movement of the OCT optical system. The movement controller  2101  determines the intensity of the newly detected longitudinal artifact, and compares the intensity of the newly detected longitudinal artifact with that of the previous longitudinal artifact. 
     The movement controller  2101  controls the movement mechanism  150  to move the OCT optical system in the same direction as the previous movement direction if the new intensity is higher than the previous intensity. On the other hand, the movement controller  2101  controls the movement mechanism  150  to move the OCT optical system in the opposite direction to the previous movement direction if the new intensity is lower than the previous intensity. The series of processes according to the present example may be terminated if there is no difference between the new intensity and the previous intensity (more generally, if the difference is smaller than a predetermined threshold). 
     Through repetitively performing such a series of processes, the position of the OCT optical system yielding a longitudinal artifact with a higher intensity may be searched for. The high intensity of the longitudinal artifact reflects the accuracy of the alignment of the OCT optical system with respect to the corneal apex. Therefore, the accuracy of the alignment of the OCT optical system with respect to the corneal apex may be enhanced by searching for the position of the OCT optical system at which a longitudinal artifact with a higher intensity can be acquired. 
     As a second example, the movement controller  2101  may be configured to execute control of the movement mechanism  150  so that a longitudinal artifact is located at the frame center of an OCT image. In other words, the movement controller  2101  may be configured to execute control of the movement mechanism  150  so that the artifact detected by the artifact detecting processor  232  passes through the center of the OCT image frame. Like the first example, the control of the present example may also be implemented by repetitively performing a series of processes including OCT image acquisition, longitudinal artifact detection, and movement of the OCT optical system. 
     As a specific example thereof, the series of processes as follows is executed in parallel with repetitive application of an OCT scan of a predetermined pattern to the anterior segment to acquire time series OCT images. The artifact detecting processor  232  detects longitudinal artifacts in the OCT images sequentially acquired through the repetitive application of the OCT scan. The movement controller  2101  (or, another element of the controller  210 , the artifact detecting processor  232 , or another element of the data processor  230 ; the same applies below) determines the positions of the detected longitudinal artifacts in the image frames of the OCT images. 
     The position of a longitudinal artifact in an image frame is, for example, the deviation of the longitudinal artifact with respect to a predetermined frame center. Here, considering that the longitudinal artifact has a shape along the A-scan direction (z direction), the frame center may be set to the center in at least one direction of at least the x direction and the y direction. For example, the center of the image frame in the x direction may be set to the frame center if the OCT image is a B-scan image along the x direction. The center of the image frame in the y direction may be set to the frame center if the OCT image is a B-scan image along they direction. The center of the xy-plane in the image frame may be set to the frame center if the OCT image is a three dimensional image. The position corresponding to both the center in the x direction and the center in the y direction in the image frame may be set to the frame center if the OCT image is a B-scan obtained using a line scan of which the vector component in the x direction and the vector component in the y direction are both non-zero. As described here as examples, the frame center may be set according to the pattern and/or the direction of an OCT scan. 
     The movement controller  2101  controls the movement mechanism  150  to move the OCT optical system after the movement controller  2101  has determined the position of a longitudinal artifact in an image frame. 
     Subsequently, the artifact detecting processor  232  detects a longitudinal artifact in an OCT image acquired after the movement of the OCT optical system. The movement controller  2101  then determines the position of a new longitudinal artifact in the image frame of the OCT image newly acquired. 
     The position of a longitudinal artifact in an image frame can be represented by a deviation vector (displacement vector) of the longitudinal artifact with respect to the center of the image frame. The movement controller  2101  calculates the inverse vector of the deviation vector, and controls the movement mechanism  150  to move the OCT optical system in the direction and by the distance both corresponding to the inverse vector calculated. 
     The series of such processes may be repeated so that the magnitude of the deviation vector becomes stable below a predetermined threshold. The series of processes is an example of tracking. This makes it possible to acquire an OCT image in which the corneal apex is located at the center of the frame. 
     The two examples described above (the first example and the second example) may be performed in parallel with one another. This configuration makes it possible to acquire an OCT image in which the corneal apex is located at the center of the frame while improving the alignment accuracy of the OCT optical system with respect to the corneal apex. 
     &lt;Corneal Image Detecting Processor  233 &gt; 
     The corneal image detecting processor  233  analyzes the OCT image constructed by the image constructing unit  220  to detect a corneal image. The corneal image detection may be executed based on a predetermined feature (characteristic) such as brightness, a position, and a shape, as in the case with the longitudinal artifact detection described above. The corneal image detection may include image processing such as segmentation. 
     The corneal image may be an entire image region corresponding to the cornea depicted in the OCT image, or only a part of this image region. For example, when the B-scan image  600  shown in  FIG. 5  is processed, the corneal image detecting processor  233  may detect any one or more of the followings: the entire corneal cross sectional image, which is a high brightness image region having a shape similar to part of an annulus; the upper edge (corneal front surface, anterior corneal surface) of the corneal cross sectional image; the apex of the anterior corneal surface (corneal apex); the lower edge (corneal back surface, posterior corneal surface); the apex of the posterior corneal surface; and a sub-tissue of the cornea (corneal epithelium, Bowman&#39;s membrane, corneal stroma, Dua&#39;s layer, Descemet&#39;s membrane, corneal endothelium). 
     In the case where the corneal image detecting processor  233  is capable of detecting the corneal apex, the corneal apex detection may be performed before the longitudinal artifact detection and the result of the corneal apex detection may be provided to the artifact detecting processor  232 . The artifact detecting processor  232  may execute the longitudinal artifact detection based on the result of the corneal apex detection carried out by the corneal image detecting processor  233 . 
     &lt;Position Judging Processor  234 &gt; 
     The position judging processor  234  judges whether a common region (an intersection) between the longitudinal artifact detected by the artifact detecting processor  232  and the corneal image detected by the corneal image detecting processor  233  is located within a predetermined area in an image frame. 
     The area (allowable area) in the image frame that serves as a reference (criterion) for the position judgement process may be set in advance, or may be set for each OCT image. As an example of the latter, the allowable area may be set based on the size of the corneal image depicted in the OCT image. 
     As described above, in the case of repetitively applying an OCT scan of a predetermined pattern to the anterior segment to acquire time series OCT images, the artifact detecting processor  232  and the corneal image detecting processor  233  perform their respective analyses on the same OCT image. These analyses are executed in parallel, for example. As a result of these analyses, both a longitudinal artifact and a corneal image are detected from a single OCT image. The allowable area described above is set in this OCT image. 
     The position judging processor  234  identifies the intersection between the detected longitudinal artifact and the detected corneal image. As described above, a longitudinal artifact is a band shaped image region along the A-scan direction (z direction), and a corneal image is typically an upwardly convex image region of an annular shape, and further a longitudinal artifact occurs in such a way that it passes through the corneal apex and its vicinity. According to these conditions, when the corneal apex and/or its vicinity are depicted in an OCT image, in other words, when a longitudinal artifact is depicted in the OCT image, the longitudinal artifact and the corneal image cross each other at the corneal apex and/or its vicinity. This intersecting region, more specifically, the region in which the longitudinal artifact and the corneal image overlap is set to the intersection. The position judging processor  234  may compare a pixel group representing the longitudinal artifact and a pixel group representing the corneal image with each other, thereby identifying one or more pixels included in both of these two pixel groups and setting the one or more pixels to the intersection. 
     Furthermore, the position judging processor  234  judges whether or not the intersection identified is included in the allowable area. This judgement process is, for example, carried out by making a judgement of whether at least part of the one or more pixels forming the intersection are included in the allowable area. Alternatively, the judgement process may be carried out by making a judgement of whether all of the one or more pixels forming the intersection are included in the allowable area. 
     In the case where the B-scan image  700  illustrated in  FIG. 6  is used for the position judgement process, the artifact detecting processor  232  analyzes the B-scan image  700  to detect the longitudinal artifact  710 , and the corneal image detecting processor  233  analyzes the B-scan image  700  to detect the corneal image  720  (or part of the corneal image  720 ). The allowable area  700   a  has been set in the B-scan image  700 . 
     The position judging processor  234  detects the corneal apex from the corneal image  720 , and identifies the intersection  730  between the detected corneal apex and the longitudinal artifact  710 . Further, the position judging processor  234  judges whether or not the identified intersection  730  is included in the allowable area  700   a.  In the example shown in  FIG. 6 , the intersection  730  is located inside the allowable area  700   a.  On the other hand, the intersection  730  may be located outside the allowable area  700   a  if the relative position between the subject&#39;s eye E and the OCT optical system at the moment when the B-scan image  700  is obtained is inappropriate. 
     Note that while such position judgement is executed after the movement control of the OCT optical system based on the longitudinal artifact in the OCT image (described above), the relative position between the subject&#39;s eye E and the OCT optical system constantly changes because of the eye movement of the subject&#39;s eye E even after the movement control has been executed. Therefore, making a judgement regarding whether or not the intersection of the longitudinal artifact and the corneal image is located within the allowable area is important in order to obtain an appropriate OCT image. 
     The condition of the intersection of the longitudinal artifact and the corneal image being included in the allowable area is a necessary condition in the present embodiment example for applying an OCT scan to the anterior segment to acquire data (e.g., an image, a measurement value) used for diagnosis. 
     &lt;Image Quality Evaluating Processor  235 &gt; 
     The image quality evaluating processor  235  calculates an image quality evaluation value of the OCT image constructed by the image constructing unit  220 . The image quality evaluation value is a numerical value indicating the degree of the image quality of the OCT image, and is used to evaluate whether or not the image quality is adequate. 
     An image quality evaluation value may be any type of numerical value that can be calculated by using any method or technique. A typical image quality evaluation value is a signal to noise ratio (SN ratio) regarding two types of image regions in an OCT image. A specific example of such an image quality evaluation value is an SN ratio regarding a signal in an image region representing a site of an eye (anterior segment) and a noise in an image region representing a background that is not a site of the eye. An image region representing a site of an anterior segment will be referred to as an anterior segment region, and an image region representing a background will be referred to as a background region. 
     Arbitrary method or technique may be employed to calculate an image quality evaluation value represented as an SN ratio for an anterior segment region and a background region. A specific example thereof will be described below. 
     First, the image quality evaluating processor  235  identifies a pixel with the maximum brightness and a pixel with the minimum brightness, for each of the plurality of A-scan images forming the OCT image. Next, the image quality evaluating processor  235  creates a histogram of brightness values (e.g., of 8-bit) based on the brightness values of a pixel group in a predetermined area that includes the pixel with the maximum brightness identified (e.g., based on the brightness values of 40 pixels around (before and after) the maximum brightness pixel). Similarly, the image quality evaluating processor  235  creates a histogram of the brightness values based on the brightness values of a pixel group in a predetermined area that includes the pixel with the minimum brightness identified. 
     Subsequently, the image quality evaluating processor  235  searches for the maximum position (brightness value) whose frequency of occurrence exceeds zero in the histogram corresponding to the pixel group that includes the pixel with the minimum brightness. Further, in the histogram corresponding to the pixel group that includes the pixel with the maximum brightness, the image quality evaluating processor  235  determines: a total number of pixels (N) included in the range equal to or less than the brightness values searched for in the above process; and a total number of pixels (S) included in the 255th brightness value from above the brightness value searched for. Then, the image quality evaluating processor  235  evaluates the percentage of the image that can be considered as a signal (i.e., the portion of the image that can be considered as not being a noise) using the following formula: 100×S÷(S+N). The image quality evaluating processor  235  applies the series of operations (calculations) described above to each A-scan image, thereby obtaining a plurality of numerical values corresponding to the plurality of A-scan images. The image quality evaluating processor  235  then calculates the average value of these numerical values and sets the average value to the image quality evaluation value. 
     The image quality evaluating processor  235  (or, another element of the data processor  230  or the controller  210 ) may judge whether the image quality evaluation value calculated is equal to or greater than a predetermined threshold. The threshold may be a default value or a value set according to an arbitrary attribute or an arbitrary condition. The image quality of the OCT image is judged to be adequate if the image quality evaluation value is equal to or greater than the threshold. On the other hand, the image quality of the OCT image is judged to be inadequate if the image quality evaluation value is less than the threshold. 
     The condition of the image quality evaluation value being equal to or greater than the threshold is a necessary condition in the present embodiment example for applying an OCT scan to the anterior segment to acquire data (e.g., an image, a measurement value) used for diagnosis. 
     The image quality evaluation value calculated by the image quality evaluating processor  235  and/or an evaluation result (judgement result) based thereon may be utilized for processing and/or control. Typically, the image quality evaluation value or the evaluation result may be utilized for processing and control for improving the image quality of an OCT image. 
     A specific example thereof will be described. The polarization controller  2103  may be configured to control the polarization device  118  (and/or the polarization device  103 ) to increase the image quality evaluation value calculated by the image quality evaluating processor  235 . The control of the present example may be implemented by repetitively performing a series of processes including the acquisition of an OCT image, the calculation of an image quality evaluation value, the evaluation of an image quality, and the control of the polarization device  118 , for example. 
     &lt;Artifact Eliminating Processor  236 &gt; 
     The artifact eliminating processor  236  eliminate the longitudinal artifact detected, by the artifact detecting processor  232 , from the OCT image constructed by the image constructing unit  220 . The display controller  2104  may control the display device  241  to display the OCT image obtained through the longitudinal artifact elimination performed by the artifact eliminating processor  236 . 
     In the artifact eliminating process, the values of the pixel group corresponding to the longitudinal artifact are replaced with other values. For example, the artifact eliminating processor  236  may obtain a new value of a target pixel based on the values of one or more pixels located around the target pixel. Such processing includes, for example, any known filtering. 
     The display controller  2104  may display, on the display device  241 , the OCT image in which the values of the pixel group corresponding to the longitudinal artifact have been converted. 
     &lt;Operation&gt; 
     An operation of the ophthalmic apparatus  1  according to the present embodiment example will be described.  FIG. 7A  and  FIG. 7B  show an example of the operation of the ophthalmic apparatus  1 . 
     (S 1 : Start Infrared Moving Image Photography of Anterior Segment) 
     To begin with, the fundus camera unit  2  of the ophthalmic apparatus  1  starts the infrared moving image photography of the anterior segment of the subject&#39;s eye E. Frames acquired by the infrared moving image photography (anterior segment images) are transferred to the data processor  230  via the controller  210 . The transfer is executed as real time processing. 
     (S 2 : Determine Destination) 
     The destination determining processor  231  analyzes the anterior segment image transferred from the fundus camera unit  2  to determine a destination of the OCT optical system. Typically, the destination determining processor  231  may detect the pupil center from the anterior segment image, and set the detected pupil center to the destination. Such processing is, for example, real time processing executed for each of the anterior segment images transferred from the fundus camera unit  2 . 
     (S 3 : Move OCT Optical System) 
     The movement controller  2101  moves the OCT optical system by controlling the movement mechanism  150  based on the destination determined in the step S 2 . Typically, the movement controller  2101  moves the OCT optical system such that the optical axis of the OCT optical system passes through the pupil center. This movement control is executed as real time processing. 
     (S 4 : Set OCT Scan Conditions) 
     The scan controller  2102  sets conditions to be applied to the repetitive OCT scan that will be started in the next step S 5 . Typically, the scan controller  2102  sets a pattern of the OCT scan and also sets an area to which the OCT scan is applied such that the center of the scan pattern (scan center) is located at the pupil center (for example, see  FIG. 4C ). 
     (S 5 : Start Repetitive OCT Scan) 
     The scan controller  2102  starts the repetitive OCT scan under the conditions set in the step S 4 . 
     A repetitive OCT scan is typically a scan mode in which an OCT scan of the same pattern is repetitively applied to the anterior segment, whereby time series OCT images are acquired. The time series OCT images are used for preparatory operations such as alignment and image quality tuning. 
     A repetitive OCT scan is typically a scan mode of repetitively performing the same B-scan whose scan center is located at the optical axis position of the OCT optical system. According to such a repetitive B-scan, it is possible to apply the B-scans passing through the pupil center or the vicinity thereof (and thus, passing through the corneal apex or the vicinity thereof) at a high repetition frequency. 
     Note that any scan pattern, such as a cross scan, a multi-cross scan, a radial scan, or a three dimensional scan, may be employed to facilitate the search for the corneal apex where longitudinal artifacts occur. 
     The selection of a scan pattern employed for a repetitive OCT scan may be made in consideration of various kinds of conditions such as a repetition frequency, the load and/or the time required for data processing, and/or the degree of easiness of corneal apex search. Further, a plurality of conditions may be met by changing or switching the pattern of the repetitive OCT scan and/or the size of the scan area during the process. 
     A repetitive OCT scan yields data sets acquired through respective OCT scans. The image constructing unit  220  constructs a plurality of OCT images based respectively on a plurality of data sets sequentially acquired by the repetitive OCT scan. When performing a repetitive B-scan, a plurality of data sets is sequentially acquired in accordance with the repetition of the B-scan. The image constructing unit  220  constructs a plurality of B-scan images based respectively on the plurality of data sets. 
     (S 6 : Start Detection of Longitudinal Artifact) 
     The artifact detecting processor  232  analyzes each of the plurality of OCT images (or, each of only part of the plurality of OCT images) sequentially acquired by the repetitive OCT scan started in the step S 5 , to detect a longitudinal artifact in each of the OCT images. This processing is executed as real time processing. 
     (S 7 : Start Display of Live OCT Image From Which Longitudinal Artifact is Eliminated) 
     The artifact eliminating processor  236  eliminates the detected longitudinal artifact from each (or part) of the plurality of OCT images sequentially acquired by the repetitive OCT scan started in the step S 5 . This artifact elimination is performed as real time processing. 
     The display controller  2104  controls the display device  241  to display the OCT image from which the longitudinal artifact has been eliminated. Typically, the display controller  2104  displays, as a moving image, the time series OCT images sequentially created by the artifact eliminating processor  236 . The display control is executed as real time processing. With this, a live OCT image, which is free of longitudinal artifacts, can be provided. 
     (S 8 : Move OCT Optical System Based on Longitudinal Artifact) 
     The movement controller  2101  moves the OCT optical system by controlling the movement mechanism  150  based on each of the plurality of longitudinal artifacts (or part of the plurality of longitudinal artifacts) sequentially detected in the step S 6 . 
     Typically, the movement controller  2101  adjust the position of the OCT optical system so that the intensity of the longitudinal artifact generated in the OCT image is maximized, and/or, so that the longitudinal artifact is located at the frame center of the OCT image. 
     (S 9 : Is OCT Optical System Position OK?) 
     The movement controller  2101  judges whether the position of the OCT optical system after the movement of the step S 8  meets a predetermined condition. A criterion or reference for judgement typically relates to the intensity of the longitudinal artifact and/or the deviation of the longitudinal artifact from the frame center of the OCT image. 
     The process proceeds to the step S 10  if the position of the OCT optical system meets the predetermined condition (S 9 : Yes). 
     The process returns to the step S 8  if the position of the OCT optical system does not meet the predetermined condition (S 9 : No), and then the steps S 8  and S 9  are repeated until the predetermined condition is met. Note that the ophthalmic apparatus  1  may be configured to issue an error if the steps S 8  and S 9  have been repeated a predetermined number of times or have been repeated for a predetermined duration of time. 
     (S 10 : Detect Corneal Image) 
     The corneal image detecting processor  233  analyzes each of the plurality of OCT images (or part of the plurality of OCT images) sequentially acquired by the repetitive OCT scan started in the step S 5 , to detect a corneal image (e.g., a corneal apex) from each of the plurality of OCT images. This processing is executed as real time processing. 
     (S 11 : Is Intersection Within Allowable Area?) 
     The position judging processor  234  identifies an intersection of the longitudinal artifact detected in the step S 6  and the corneal image detected in the step S 10 , and judges whether the intersection is located within the allowable area in the frame of that OCT image. 
     The process proceeds to the step S 12  if the position judging processor  234  judges that the intersection is located within the allowable area (S 11 : Yes). 
     The process returns to the step S 8  if the position judging processor  234  judges that the intersection is not located inside the allowable area (S 11 : No). Then, the steps S 8  to S 11  are repeated until “Yes” is issued as a judgement result in both the steps S 9  and S 11 . Note that the ophthalmic apparatus  1  may be configured to issue an error if part or all of the steps S 8  to S 11  have been repeated a predetermined number of times or have been repeated for a predetermined duration of time. 
     (S 12 : Calculate Image Quality Evaluation Value) 
     The image quality evaluating processor  235  analyzes each of the plurality of OCT images (or part of the plurality of OCT images) sequentially acquired by the repetitive OCT scan started in the step S 5 , to calculate an image quality evaluation value for each of the OCT images. This processing is executed as real time processing. 
     (S 13 : Is Image Quality Evaluation Value Equal to or Greater Than Threshold?) 
     The image quality evaluating processor  235  judges whether the image quality evaluation value calculated in the step S 12  is equal to or greater than a predetermined threshold. 
     The process proceeds to the step S 15  if the image quality evaluating processor  235  judges that the image quality evaluation value is equal to or greater than the predetermined threshold (S 13 : Yes). 
     The process proceeds to the step S 14  if the image quality evaluating processor  235  judges that the image quality evaluation value is less than the predetermined threshold (S 13 : No). 
     (S 14 : Control Polarization Device) 
     If the image quality evaluating processor  235  judges that the image quality evaluation value is less than the predetermined threshold (S 13 : No), the polarization controller  2103  controls the polarization device  118  (and/or the polarization device  103 ) to increase the image quality evaluation value to be calculated next in the step S 12 . 
     The steps S 12  to S 14  are repeated until “Yes” is issued as a judgement result in the step S 13 . Note that the ophthalmic apparatus  1  may be configured to issue an error if the steps S 12  to S 14  have been repeated a predetermined number of times or have been repeated for a predetermined duration of time. 
     (S 15 : Perform OCT Scan for Diagnosis) 
     As described above, if the image quality evaluating processor  235  judges that the image quality evaluation value is equal to or greater than the predetermined threshold (S 13 : Yes), then the step S 15  is started. At this stage, the alignment state of the OCT optical system with respect to the anterior segment (the corneal apex, the pupil center, etc.) and the image quality of the OCT image to be acquired are adequate. 
     The scan controller  2102  applies an OCT scan to the anterior segment at the timing when such adequate conditions are secured. The image constructing unit  220  then constructs an OCT image from the data acquired by the OCT scan applied. The data processor  230  may also process and/or analyze this OCT image. 
     The OCT image acquired in the step S 15  is typically used for diagnosis, and its scan condition is generally different from the condition for the repetitive OCT scan started in the step S 5 . Typically, the OCT image obtained in the step S 15  has higher definition. Further, arbitrary conditions of the OCT image obtained in the step S 15  such as the scan pattern and/or the size of the scan area may be different from those of the repetitive OCT scan started in the step S 5 . 
     With the above, the operation illustrated in  FIG. 7A  and  FIG. 7B  ends (End). 
     &lt;Effects&gt; 
     Some effects of the ophthalmic apparatus  1  according to the embodiment example will be described. 
     The ophthalmic apparatus  1  includes an OCT optical system, the image constructing unit  220 , the artifact detecting processor  232 , the movement mechanism  150 , the movement controller  2101 , the corneal image detecting processor  233 , the position judging processor  234 , the image quality evaluating processor  235 , and the scan controller  2102 . 
     The OCT optical system is an optical system configured for applying an OCT scan to the anterior segment of the subject&#39;s eye E. The OCT optical system in the embodiment example described above includes at least the series of elements forming the measurement arm in the fundus camera unit  2 . The image constructing unit  220  is configured to construct an OCT image based on data acquired by the OCT scan. 
     The artifact detecting processor  232  is configured to analyze the OCT image constructed by the image constructing unit  220  to detect a longitudinal artifact. The longitudinal artifact is an artifact along an A-scan direction. 
     The movement mechanism  150  is configure to move (only a part of or all of) the OCT optical system. The movement controller  2101  (a first movement controller) is configured to perform control of the movement mechanism  150  based on the longitudinal artifact detected by the artifact detecting processor  232 , to move the OCT optical system. 
     The corneal image detecting processor  233  is configured to analyze the OCT image constructed by the image constructing unit  220 , to detect a corneal image. 
     The position judging processor  234  is configured make a judgement of whether an intersection between the longitudinal artifact detected by the artifact detecting processor  232  and the corneal image detected by the corneal image detecting processor  233  is located within a predetermined area in a frame of the OCT image. 
     The image quality evaluating processor  235  is configured to calculate an image quality evaluation value of the OCT image constructed by the image constructing unit  220 . For example, the image quality evaluating processor  235  may calculate, as an image quality evaluation value, a ratio between a signal in the anterior segment region and a noise in the background region in the OCT image constructed by the image constructing unit  220 . 
     The scan controller  2102  is configured to perform control of the OCT optical system to apply an OCT scan of a predetermined pattern to the anterior segment, if the position judging processor  234  judges that the intersection is located within the predetermined area in the frame and also if the image quality evaluation value calculated by the image quality evaluating processor  235  is equal to or greater than a predetermined threshold. 
     According to the ophthalmic apparatus  1  configured in this way, preparatory operations can be carried out automatically while checking whether or not necessary conditions are met, and an OCT scan (imaging, measurement, etc.) can be executed at an appropriate timing at which the necessary conditions are met. The preparatory operations here include, for example, the alignment of the OCT optical system with respect to a target site, the adjustment of a depiction position of a target site in an image frame, and the control of the image quality. 
     Having automated the preparatory operations for applying an OCT scan to the anterior segment of a living eye in this way, even a person unfamiliar with the operation of the ophthalmic apparatus can easily conduct an OCT examination. This also makes it possible for a subject to have an OCT examination alone. As a result, the burdens on the subject and the examiner in the OCT examination is reduced. 
     In recent years, there is a movement to install an ophthalmic apparatus, to which an OCT technique and technology are applied, in an optician&#39;s store, a drug store, or a patient&#39;s home in order to use the apparatus for screening of eye diseases. The ophthalmic apparatus  1  in which the preparatory operations are automated is effective also as an ophthalmic apparatus to be installed in such places. 
     The ophthalmic apparatus  1  may be configured to execute the following series of processes after the movement controller  2101  (the first movement controller) has performed the control of the movement mechanism  150  based on the longitudinal artifact. First, the OCT optical system applies an OCT scan to the anterior segment. Next, the image constructing unit  220  constructs an OCT image based on data acquired by the OCT scan. Subsequently, the artifact detecting processor  232  analyzes the OCT image to detect a longitudinal artifact. Next, the corneal image detecting processor  233  analyzes the OCT image to detect a corneal image. Then, the position judging processor  234  judges whether an intersection of the longitudinal artifact and the corneal image is located within a predetermined area in a frame of the OCT image. 
     According to the ophthalmic apparatus  1  configured in this way, another OCT scan can be performed to construct an OCT image after alignment has been performed based on the longitudinal artifact, and then make a judgement on a depiction position of a target site based on the longitudinal artifact and the corneal image both detected from the OCT image. In other words, the ophthalmic apparatus  1  is capable of making a depiction position judgement under an adequate alignment condition achieved by the alignment on the basis of the longitudinal artifact. As a result, smooth linkage between the alignment and the depiction position judgement can be achieved. 
     The ophthalmic apparatus  1  may be configured in such a manner that the image quality evaluating processor  235  performs the calculation of an image quality evaluation value after the position judging processor  234  has judged that the intersection is located within the predetermined area. 
     According to the ophthalmic apparatus  1  configured in this way, the depiction position judgement can be made under an adequate alignment condition achieved by the alignment on the basis of the longitudinal artifact and the image quality evaluation can be performed after the adequate depiction position has been achieved. As a result, smooth linkage between the alignment, the depiction position judgement, and the image quality evaluation can be achieved. 
     The ophthalmic apparatus  1  includes the fundus camera unit  2  (an anterior segment photographing system) and the destination determining processor  231 . The fundus camera unit  2  is configured to perform photography of the anterior segment. The destination determining processor  231  is configured to analyze an anterior segment image acquired by the fundus camera unit  2  to determine a destination of the OCT optical system. The movement controller  2101  (a second movement controller) is configured to perform control of the movement mechanism  150  based on the destination determined by the destination determining processor  231 . The OCT optical system starts the application of an OCT scan to the anterior segment after the movement controller  2101  has performed the control of the movement mechanism  150 . 
     According to the ophthalmic apparatus  1  configured in this way, (rough) alignment can be performed based on an anterior segment image before the application of the OCT scan. This facilitates alignment on the basis of the longitudinal artifact performed after the commencement of the OCT scan. This also enables smooth linkage between the alignment based on the anterior segment image and the alignment based on the longitudinal artifact. 
     The destination determining processor  231  may set the destination at a pupil center of the anterior segment for the alignment on the basis of the anterior segment image. The OCT optical system may start the application of an OCT scan of a pattern with a scan center located at the pupil center. 
     According to the ophthalmic apparatus  1  thus configured, the OCT scan can be started with the pupil center, which is one of the landmarks of the anterior segment, as a reference. This makes it possible to facilitate and expedite the alignment on the basis of the longitudinal artifact performed after the commencement of the OCT scan. More specifically, starting the OCT scan with the pupil center as a reference makes it easier to detect a longitudinal artifact occurring at the corneal apex and its vicinity, and thus facilitates and speeds up the alignment on the basis of the longitudinal artifacts. 
     The OCT scan performed by the OCT optical system after the alignment based on the anterior segment image may be a repetitive OCT scan of a pattern with a scan center located at the pupil center. The image constructing unit  220  constructs a plurality of images based respectively on a plurality of data sets sequentially acquired by the repetitive OCT scan. Note that the repetitive OCT scan may be a repetitive B-scan. Further, the OCT optical system may continue the repetitive OCT scan at least until the image quality evaluating processor obtains an image quality evaluation value equal to or greater than the predetermined threshold. 
     According to the ophthalmic apparatus  1  configured in this way, a plurality of OCT images (time series OCT images) synchronized with the repetition of the OCT scan can be obtained. The time series OCT images may be employed and utilized for various purposes such as alignment operation, depiction position judgement processing, image quality evaluation processing, and moving image display operation. 
     In the alignment based on the longitudinal artifact, the movement controller  2101  (the first movement controller) can perform the control of the movement mechanism  150  to increase (enhance) the intensity of the longitudinal artifact detected by the artifact detecting processor  232 . 
     According to the ophthalmic apparatus  1  configured in this way, the accuracy of the alignment of the OCT optical system with respect to the corneal apex can be increased by searching for a position of the OCT optical system at which a longitudinal artifact with a higher intensity can be obtained. 
     In the alignment based on the longitudinal artifact, the movement controller  2101  (the first movement controller) can perform the control of the movement mechanism  150  such that the artifact detected by the artifact detecting processor  232  passes through the center of the image frame. 
     According to the ophthalmic apparatus  1  configured in this way, the alignment of the OCT optical system can be performed in such a manner that the corneal apex is depicted at an appropriate position in the image frame. 
     The OCT optical system includes the measurement arm and the reference arm. The measurement arm is configured to guide the measurement light LS to the anterior segment, and the reference arm is configured to guide the reference light LR that is to be superposed on return light of the measurement light LS returning from the anterior segment. At least one of the measurement arm and the reference arm may include a polarization device. The polarization device is configured to change a polarization state of the light guided thereby. The ophthalmic apparatus  1  includes the polarization device  118  that is provided in the reference arm. The ophthalmic apparatus  1  may further include the polarization controller  2103 . The polarization controller  2103  is configured to perform control of the polarization device to increase the image quality evaluation value calculated by the image quality evaluating processor  235  (e.g., the ratio between the signal in the anterior segment region and the noise in the background region). 
     According to the ophthalmic apparatus  1  configured as described above, an image quality of an OCT image can be improved if the image quality is low. 
     The ophthalmic apparatus  1  may include the display controller  2104  configured to display the OCT image constructed by the image constructing unit  220  on the display device  241  (a display device). The display device may be included in the ophthalmic apparatus  1  or may be a peripheral device connected to the ophthalmic apparatus  1 . 
     According to the ophthalmic apparatus  1  thus configured, it is possible to offer the user a visualization of the OCT image constructed by the image constructing unit  220 . 
     The ophthalmic apparatus  1  may include the artifact eliminating processor  236 . The artifact eliminating processor  236  is configured to eliminate the longitudinal artifact detected, by the artifact detecting processor  232 , from the OCT image constructed by the image constructing unit  220 . Note that the artifact eliminating processor  236  may also be capable of eliminating an artifact other than the longitudinal artifact. The display controller  2104  may display, on the display device  241 , the OCT image from which at least the longitudinal artifact is eliminated by the artifact eliminating processor  236 . Note that the artifact eliminating processor  236  and the display controller  2104  are included in the “display controller”. 
     According to the ophthalmic apparatus  1  configured in this way, a longitudinal artifact, which is useful for alignment but is an obstacle to observation, can be eliminated from a display image. 
     &lt;Control Method of Ophthalmic Apparatus, Program, Recording Medium&gt; 
     The embodiment examples described above also provide a method of controlling an ophthalmic apparatus. The ophthalmic apparatus to which this control method can be applied includes an OCT optical system that applies an OCT scan to an anterior segment of a subject&#39;s eye, an image constructing unit that constructs an image based on data acquired by the OCT scan, and a movement mechanism that moves the OCT optical system. 
     The control method of the present embodiment example includes an artifact detecting step, a movement control step, a corneal image detecting step, a position judging step, an image quality evaluating step, and a scan control step. 
     The artifact detecting step detects an artifact along an A-scan direction by analyzing the image constructed by the image constructing unit. The movement control step performs control of the movement mechanism based on the artifact detected. The corneal image detecting step detects a corneal image by analyzing the image constructed by the image constructing unit. The position judging step judges whether an intersection of the artifact detected and the corneal image detected is located within a predetermined area in an image frame. The image quality evaluating step calculates an image quality evaluation value of the image constructed by the image constructing unit. The scan control step performs control of the OCT optical system to apply an OCT scan of a predetermined pattern to the anterior segment, if it is judged that the intersection is located within the predetermined area and the image quality evaluation value calculated is equal to or greater than a predetermined threshold. 
     Any of the processes that can be executed by the ophthalmic apparatus  1  according to the above embodiment example, can be combined with the control method of the present embodiment example. 
     According to such a control method, the same effects are achieved as those of the ophthalmic apparatus  1  according to the embodiment example described above. 
     It is possible to configure a program that causes the ophthalmic apparatus to execute such a control method. The program may include, for example, any of the programs described regarding the ophthalmic apparatus  1  according to the embodiment example described above. 
     Also, it is possible to create a computer-readable non-transitory recording medium storing such a program. The non-transitory recording medium may be in any form, and examples thereof include a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, and the like. 
     &lt;Embodiment Example Applicable to Corner Angle OCT&gt; 
     Next, a description will be given of an embodiment example configured to be capable of performing OCT for depicting the corner angle of the subject&#39;s eye. The corner angle is a site of the intersection between the cornea and the iris. The aqueous humor is discharged through the corner angle. 
     The hardware configuration of the ophthalmic apparatus according to the present embodiment example may be the same as the hardware configuration of the ophthalmic apparatus  1  applicable to corneal OCT. Further, some parts of the software configuration of the ophthalmic apparatus according to the present embodiment example may be the same as corresponding parts of the software configuration of the ophthalmic apparatus  1 . Hereinafter,  FIG. 1 ,  FIG. 2 , and  FIG. 3A  relating to the ophthalmic apparatus  1  will be referred to as needed. Further, the description of the present embodiment example may use some of the reference characters used in the description of the ophthalmic apparatus  1  for the same or similar elements as or to those of the ophthalmic apparatus  1 . Needless to say, some embodiments applicable to corner angle OCT may employ a configuration different from that of the present embodiment example. 
       FIG. 8  shows a configuration example of the ophthalmic apparatus applicable to corner angle OCT. The ophthalmic apparatus  1 A includes the controller  210 A and the data processor  230 A in addition to the fundus camera unit  2 , the OCT unit  100 , the movement mechanism  150 , the image constructing unit  220 , and the user interface  240  similar to the ophthalmic apparatus  1  described above. The controller  210 A is provided in place of the controller  210  of the ophthalmic apparatus  1  described above. The data processor  230 A is provided in place of the data processor  230  of the ophthalmic apparatus  1  described above. 
     The fundus camera unit  2 , the OCT unit  100 , the movement mechanism  150 , the image constructing unit  220 , and the user interface  240  have the same configurations and functions as those of the ophthalmic apparatus  1  described above. The controller  210 A and the data processor  230 A will be described below. 
     &lt;Controller  210 A&gt; 
     The controller  210 A includes a processor and controls each part of the ophthalmic apparatus  1 A. The controller  210 A includes, for example, a main controller and a memory like the controller  210  of the ophthalmic apparatus  1  described above. 
     The main controller of the controller  210 A controls each element of the ophthalmic apparatus  1 A (including the elements shown in  FIG. 1  to  FIG. 3A  and  FIG. 8 ). The function of the main controller may typically be implemented by the cooperation of hardware including a processor and software including a control program. At least part of the functions of the main controller may be implemented by means of hardware including a control circuit. 
     The memory of the controller  210 A stores various kinds of data. The memory may store various kinds of templates, various kinds of parameter values, and various kinds of software for operating the ophthalmic apparatus  1 A. The memory typically includes a storage having a relatively large capacity such as a hard disk. Note that various kinds of data may be stored in a storage or an information processing apparatus on a communication line. If this is the case, the memory does not need to include the storage having a relatively large capacity. The same applies if a relatively large capacity storage is employed as a peripheral device of the ophthalmic apparatus  1 A. 
     &lt;Data Processor  230 A&gt; 
     The data processor  230 A performs various kinds of data processing like the data processor  230  of the above embodiment. The function of the data processor  230 A may typically be implemented by the cooperation of hardware including a processor and software including a data processing program. At least part of the function of the data processor  230 A may be implemented by hardware including a data processing circuit. 
     &lt;Details of Configuration Example of Processing System&gt; 
       FIG. 8  shows an example of the configurations of the controller  210 A and the data processor  230 A. 
     &lt;Example of the Controller  210 A&gt; 
     The controller  210 A illustrated in  FIG. 8  includes the movement controller  2101 A, the scan controller  2102 A, the polarization controller  2103 A, and the display controller  2104 A. 
     The movement controller  2101 A executes control of the movement mechanism  150 . The scan controller  2102 A executes control of elements for performing the OCT scan, such as the light source unit  101  and the optical scanner  44 . The polarization controller  2103 A executes control of the polarization device  118 . Further, the polarization controller  2103 A may be configured to execute control of the polarization device  103  in addition to or instead of the control of the polarization device  118 . The display controller  2104 A executes control of the user interface  240  (the display device  241 ). 
     The function of the movement controller  2101 A, the function of the scan controller  2102 A, the function of the polarization controller  2103 A, and the function of the display controller  2104 A each may typically be implemented by the cooperation of hardware including a processor and software including a control program. At least part of the functions of any of the movement controller  2101 A, the scan controller  2102 A, the polarization controller  2103 A, and the display controller  2104 A may be implemented by hardware including a control circuit. 
     The main controller of the controller  210 A includes the movement controller  2101 A, the scan controller  2102 A, the polarization controller  2103 A, and the display controller  2104 A. Any of the movement controller  2101 A, the scan controller  2102 A, the polarization controller  2103 A, and the display controller  2104 A may include storage hardware (i.e., the memory of the controller  210 A). Processing executed by the movement controller  2101 A, processing executed by the scan controller  2102 A, processing executed by the polarization controller  2103 A, and processing executed by the display controller  2104 A will be described later. 
     &lt;Example of the Data Processor  230 A&gt; 
     The data processor  230 A illustrated in  FIG. 8  includes the destination determining processor  231 A, the scan area setting processor  232 A, the image quality evaluating processor  233 A, the corner angle image detecting processor  234 A, the iris image detecting processor  235 A, and the position judging processor  236 A. 
     The function of the destination determining processor  231 A, the function of the scan area setting processor  232 A, the function of the image quality evaluating processor  233 A, the function of the corner angle image detecting processor  234 A, the function of the iris image detecting processor  235 A, and the function of the position determining processor  236 A each may typically be implemented by the cooperation of hardware including a processor and software including a data processing program. At least part of the functions of any of the destination determining processor  231 A, the scan area setting processor  232 A, the image quality evaluating processor  233 A, the corner angle image detecting processor  234 A, the iris image detecting processor  235 A, and the position judging processor  236 A may be implemented by hardware including a data processing circuit. Any of the destination determining processor  231 A, the scan area setting processor  232 A, the image quality evaluating processor  233 A, the corner angle image detecting processor  234 A, the iris image detecting processor  235 A, and the position judging processor  236 A may include storage hardware. 
     The followings are descriptions of each of the elements included in the data processor  230 A. 
     &lt;Destination Determining Processor  231 A&gt; 
     Similar to the ophthalmic apparatus  1  described above, the ophthalmic apparatus  1 A is capable of performing anterior eye segment imaging using the fundus camera unit  2 . The destination determining processor  231 A analyzes an anterior segment image acquired by the fundus camera unit  2  to determine a destination (goal of movement) of an OCT optical system. The movement controller  2101 A controls the movement mechanism  150  based on the destination determined by the destination determining processor  231 A. 
     The destination may be, for example, coordinates (x, y, z) representing a position of the fundus camera unit  2  moved by the movement mechanism  150 , or a control parameter of the movement mechanism  150 . The types of information determined as a destination by the destination determining processor  231 A are not limited to the above examples. The type of information representing a destination is determined in advance, for example, according to the configuration of hardware such as a movement mechanism and/or the configuration of software for movement control. 
     Similar to the ophthalmic apparatus  1  described above, the ophthalmic apparatus  1 A includes an OCT optical system for applying an OCT scan to the subject&#39;s eye E. The present embodiment example is configured to move, by the movement mechanism  150 , the fundus camera unit  2  including the OCT optical system. 
     The ophthalmic apparatus  1 A performs infrared moving image photography of the anterior segment of the subject&#39;s eye E using the fundus camera unit  2 . In parallel with the infrared moving image photography, the destination determining processor  231 A sequentially analyzes a plurality of anterior segment images (a frame group (group of frames) of a moving image) acquired by the fundus camera unit  2  in a successive manner, thereby being able to acquire time series data of destinations of the OCT optical system. A plurality of destinations acquired by the destination determining processor  231 A in parallel with the infrared moving image photography of the anterior segment is sequentially sent to the movement controller  2101 A. The movement controller  2101 A executes control of the movement mechanism  150  based on the destinations sequentially input from the destination determining processor  231 A. The control of the movement mechanism  150  is carried out as real time processing. This allows the fundus camera unit  2  to be moved in accordance with the time series change in the destinations represented by the time series destination data. As a result of this, the position of the OCT optical system can be automatically regulated according to eye movement of the subject&#39;s eye E (tracking). 
     The scan area setting processor  232 A may set a scan area at an arbitrary timing after the control of the movement mechanism  150  performed by the movement controller  2101 A. Contents of the scan area setting processing and execution timing thereof will be described later. 
     An example will be described of the destination determination processing performed by the destination determining processor  231 A.  FIG. 9A  shows an example of an anterior segment image acquired by the fundus camera unit  2 . The anterior segment image  800  contains the pupil image  810  corresponding to the pupil of the subject&#39;s eye E and the iris image  820  corresponding to the iris. Here, the pupil image  810  is shown as an image region indicated by diagonal lines, and the iris image  820  is shown as an image region indicated by horizontal lines. 
     The destination determining processor  231 A identifies the pupil image  810  and the iris image  820  by analyzing the anterior segment image  800 . The analysis may be performed in the same way as the analysis performed by the destination determining processor  231  described above. 
     The reference character “ 810   a”  in  FIG. 9B  denotes the outer edge of the pupil image  810 , and the reference character “ 820   a”  denotes the outer edge of the iris image  820 . Here, at least one of the pupil outer edge  810   a  and the iris outer edge  820   a  may be an approximate circle or an approximate ellipse. 
     The destination determining processor  231 A identifies the pupil center  810   b  of the anterior segment based on at least one of the pupil image  810  and the iris image  820 , for example, based on at least one of the pupil outer edge  810   a  and the iris outer edge  820   a.  This process is performed in the same manner as the process performed by the destination determining processor  231  described above. 
     Next, the destination determining processor  231 A determines a straight line that passes through the pupil center  810   b  and extends along a predetermined direction. For example, as shown in  FIG. 9C , the destination determining processor  231 A determines the straight line  830  that passes through the pupil center  810   b  and extends along the x direction. The orientation of the straight line is not limited to the x direction and may be arbitrary. This process is an operation (calculation) in the xy coordinate system in which the anterior segment image  800  is defined. 
     Next, the destination determining processor  231 A determines the intersection point  840  between the straight line  830  and the iris outer edge  820   a  as the destination. This process is an operation (calculation) in the xy coordinate system in which the anterior segment image  800  is defined. The intersection point  840  determined in this way is set to the destination. Note that the process of determining the destination is not limited to the present example. 
     The movement controller  2101 A controls the movement mechanism  150  such that the destination (the intersection point  840 ) determined by the destination determining processor  231 A is placed at the center of the image frame. As a result, the optical axis of the OCT optical system substantially coincides with the destination (the intersection point  840 ). 
     In the example shown in  FIG. 9C , the straight line  850  is located at the center of the frame in the x direction, and the straight line  830  is located at the center of the frame in the y direction. Further, the intersection point  840  is located at the center position of the frame that is the intersection point of these straight lines  830  and  850 . 
     More generally, the OCT optical system may be placed at a position corresponding to an arbitrary position in the image frame. For example, the OCT optical system may be moved such that the optical axis coincides with a default position in the image frame. In some examples, the destination may be set by referring to a one dimensional region or a two dimensional region in the anterior segment image. For example, the one dimensional area is, for example, any of a corneal outer edge image, an iris outer edge image, and the like, and the two dimensional area is, for example, any of a corneal image, an iris image, and the like. In some examples, any of an eyelash image, an eyelid image, a lesion image, and the like may be referred to in destination setting. 
     &lt;Scan Area Setting Processor  232 A&gt; 
     The scan area setting processor  232 A is configured to set a scan area in a region that passes through the iris outer edge of the anterior segment of the subject&#39;s eye E. The scan area is a region in the anterior segment to which an OCT scan is applied. As described above, the scan area setting processor  232 A of the present embodiment example sets the scan area at an arbitrary timing after the control of the movement mechanism  150  performed by the movement controller  2101 A. 
     As in the case of the ophthalmic apparatus  1  described above, the pattern of the OCT scan may be set in an arbitrary manner. For example, a line scan (B-scan), a cross scan, a multi-cross scan, a radial scan, or a three dimensional scan may be employed as the OCT scan pattern. 
     The scan controller  2102 A may set a scan area in such a way that the scan area passes through the destination determined by the destination determining processor  231 A. For example, in the case where the intersection point  840  illustrated in  FIG. 9C  is determined as the destination, the scan area setting processor  232 A may set a scan area that passes through the intersection point  840 . 
     For example, in the case where a line scan is employed, the scan area setting processor  232 A may set a scan line (B-scan) that lies along the straight line  830  and has its scan center located at the intersection point  840  (See the reference character  860  in  FIG. 9D ). 
     Such processing makes it possible to execute an OCT scan that includes at least a B-scan substantially orthogonal to the iris outer edge. The corner angle of a standard eye is located near a position on the back side (+z direction) of the iris outer edge. Therefore, an OCT image that represents the corner angle may be acquired by performing an OCT scan like the one carried out in the present example. 
     While the destination is set by detecting a feature point from an infrared observation image of the anterior segment in the present embodiment example, other methods may also be (additionally) employed. For example, any other technique or method such as an alignment indicator, a stereo alignment, or an optical lever may be used to detect a feature point of the anterior segment. In the case of employing a technique or method capable of detecting the pupil center, the destination and the scan area may be set by referring to the pupil center detected by the detection technique or method employed. 
     &lt;Image Quality Evaluating Processor  233 A&gt; 
     The image quality evaluating processor  233 A is configured to calculate an image quality evaluation value of the OCT image constructed by the image constructing unit  220 . The type of the image quality evaluation value and the calculation method or technique thereof may be arbitrary, and may be any type of the image quality evaluation value and any calculation method or technique applicable to the ophthalmic apparatus  1  described above, for example. 
     As an example, the image quality evaluating processor  233 A calculates, as an image quality evaluation value, the ratio of a signal in the anterior segment region to a noise in the background region in an OCT image constructed by the image constructing unit  220 . Here, as in the case of the ophthalmic apparatus  1 , an image region representing a site of an anterior segment will be referred to as an anterior segment region, and an image region representing a background will be referred to as a background region. Further, the method or technique employed to calculate an image quality evaluation value represented as a signal to noise ratio (SN ratio) for an anterior segment region and a background region may be arbitrary, and may be the same as in the case of the ophthalmic apparatus  1  described above. 
       FIG. 10  shows an OCT image actually obtained by a B-scan along the scan line  860  shown in  FIG. 9D . In the B-scan image  900 , a band shaped high brightness image extending from the upper right to the lower left of the image frame corresponds to a cross section of the cornea (the corneal region  910 ). Further, a high brightness image with an uneven upper surface extending in the lateral direction near the lower side of the image frame corresponds to a cross section of the iris (the iris region  920 ). The corneal region  910  and the iris region  920  are examples of the anterior segment region. 
     The background region  930  is located on the left side (upper left side) of the corneal region  910 , and also the background region  940  is located on the right side (lower right side) of the corneal region  910  and above the iris region  920 . The background region  930  is an image region corresponding to air, and the background region  940  is an image region corresponding to the anterior chamber (aqueous humor). 
     The boundary between the corneal region  910  and the background region  930  corresponds to the anterior corneal surface, the boundary between the corneal region  910  and the background region  940  corresponds to the posterior corneal surface, and the boundary between the iris region  920  and the background region  940  corresponds to the anterior iris surface. 
     The image quality evaluating processor  233 A may calculate, as an evaluation value for the B-scan image  900 , the ratio of a signal in the corneal region  910  to a noise in the background region  930  and/or the background region  940  adjacent to the corneal region  910 . Here, the signal in the corneal region  910  may be a signal in at least a part of the corneal region  910 . Similarly, the noise in the background region  930  may be a noise in at least a part of the background region  930 , and the noise in the background region  940  may be a noise in at least a part of the background region  940 . 
     Further, the image quality evaluating processor  233 A may calculate the ratio of a signal in the iris region  920  to a noise in the background region  940  adjacent to the iris region  920 , as an image quality evaluation value for the B-scan image  900 . Here, the signal in the iris region  920  may be a signal in at least a part of the iris region  920 . Similarly, the noise in the background region  940  may be a noise in at least a part of the background region  940 . 
     An example of such image quality evaluation will be described with reference to  FIG. 11 . The B-scan image  1000  contains the corneal region  1010 , the iris region  1020 , the background region  1030 , and the background region  1040 . In comparison with the B-scan image  900  shown in  FIG. 10 , the corneal region  1010  corresponds to the corneal region  910 , the iris region  1020  corresponds to the iris region  920 , the background region  1030  corresponds to the background region  930 , and the background region  1040  corresponds to the background region  940 . 
     To begin with the image quality evaluating processor  233 A sets a target area for image quality evaluation. The image quality evaluating processor  233 A in the present example may set the first target area  1050  and the second target area  1060 . Here, the first target area  1050  includes part of the corneal region  1010  and part of the background region  1030 , and the second target area  1060  includes part of the iris region  1020  and part of the background region  1040 . 
     While the shape of the target area in the present example is rectangular, the target area may be of any shape. Further, the target area may also be of any size. For example, the target area may be set to include the entire corneal region  1010  and the entire background region  1030 . Furthermore, at least one of the shape and the size of the target area may be set in advance in some examples. That is, the target area may have a default shape and/or a default size. 
     In the present example, each target area is set to include part of a single anterior segment region (the corneal region  1010  or the iris region  1020 ) and part of a single background region (the background region  1030  or the background region  1040 ). In some examples, the target area may be set to include at least one of two or more anterior segment regions (part thereof) and two or more background regions (part thereof). For example, the target area may be set to include at least part of the corneal region  1010 , at least part of the iris region  1020 , and at least part of the background region  1040 . 
     Next, the image quality evaluating processor  233 A identifies the anterior segment region and the background region in the target area. The image quality evaluating processor  233 A in the present example may identify part of the corneal region  1010  in the target area  1050  by identifying the intersection between the target area  1050  and the corneal region  1010 . Similarly, the image quality evaluating processor  233 A may identify part of the iris region  1020  in the target area  1060  by identifying the intersection between the target area  1060  and the iris region  1020 . 
     One or both of the identification of the anterior segment region and the identification of the background region may be performed using any known segmentation. The segmentation may be applied to the entire OCT image, or the segmentation may be applied only to the target area. Further, the distinction between the corneal region  1010  and the iris region  1020  may be performed based on an arbitrary type of parameter such as depiction position, shape, and brightness. 
     Subsequently, the image quality evaluating processor  233 A calculates the ratio of a signal in the identified anterior segment region to a noise in the identified background region. The image quality evaluating processor  233 A in the present example may calculate the ratio of a signal in part of the corneal region  1010  to a noise in part of the background region  1030  in the target area  1050 . Similarly, the image quality evaluating processor  233 A may calculate the ratio of a signal in part of the iris region  1020  to a noise in part of the background region  1040  in the target area  1060 . 
     The signal to noise ratio calculated in this way may be used as an image quality evaluation value. Note that in the case where an image quality evaluation value is obtained for each of the two or more target areas as in the present example, statistical processing may be applied to the two or more image quality evaluation values obtained. Examples of a statistical value obtained from such two or more image quality evaluation values include the mean value, the maximum value, the minimum value, the median, the mode, the variance, the standard deviation, and the like. a statistical value obtained in such a way may be used as an image quality evaluation value. 
     For example, the image quality evaluating processor  233 A may identify the tissue depicted with the lowest image quality among the tissues depicted in the OCT image, by determining the minimum value among the two or more image quality evaluation values. In addition, control of the polarization device  118  may be employed to maximize the minimum value to be obtained. The control of the polarization device  118  will be described later. 
     As in the case of the ophthalmic apparatus  1  described above, the image quality evaluating processor  233 A (or, another element of the data processor  230 A, or the controller  210 A) may perform a judgement of whether the image quality evaluation value calculated is equal to or greater than a predetermined threshold. 
     Similar to the case of the ophthalmic apparatus  1  described above, the image quality evaluation value calculated by the image quality evaluating processor  233 A and/or a result of the evaluation result (a result of the judgement) obtained based on the image quality evaluation value, may be utilized for processing and/or control. Typically, the image quality evaluation value or the evaluation result may be utilized for processing and control for improving the image quality of an OCT image. 
     In a specific example of the image quality improvement, the polarization controller  2103 A may be configured to control the polarization device  118  (and/or the polarization device  103 ) to increase an image quality evaluation value to be calculated by the image quality evaluating processor  233 A. The control of the present example may be implemented by repetitively (iteratively) performing a series of processes including the acquisition of an OCT image, the calculation of an image quality evaluation value, the evaluation of an image quality, and the control of the polarization device  118 , for example. 
     &lt;Corner Angle Image Detecting Processor  234 A&gt; 
     The corner angle image detecting processor  234 A is configured to detect a corner angle image by analyzing the OCT image constructed by the image constructing unit  220  based on the data obtained by the OCT scan for the scan area set by the scan area setting processor  232 A. The corner angle image detection may be executed on the basis of a predetermined feature (characteristic) such as brightness, a position, and a shape, as in the case with the corneal image detection performed by the ophthalmic apparatus  1  described above. In some examples, the corner angle image detection may include image processing such as segmentation. 
     The corner angle image may be a position (that is, a single pixel) corresponding to the corner angle depicted in the OCT image, or may include a corneal region and/or an iris region in the vicinity of the corner angle. 
     The timing to execute the corner angle image detection may be arbitrary. For example, the corner angle image detecting processor  234 A may perform the detection of a corner angle image after an image quality evaluation value equal to or greater than a predetermined threshold is obtained by the image quality evaluating processor  233 A. As a result of this, the corner angle may be detected with high accuracy and high precision from an OCT image with good image quality. 
     An example of the process of detecting a corner angle image will be described. The corner angle image detecting processor  234 A first analyzes an OCT image to detect a posterior corneal surface image and an anterior iris surface image. The posterior corneal surface image is an image region corresponding to the posterior corneal surface, and the anterior iris surface image is an image region corresponding to the anterior iris surface. Some examples of this process may include segmentation. 
     Next, the corner angle image detecting processor  234 A detects a position where the posterior corneal surface image and the anterior iris surface image intersect with each other. The intersection position detected corresponds to the corner angle. The intersection position of the posterior corneal surface image and the anterior iris surface image may be any of a point, a line, or a surface. 
     An example of the process of detecting a corner angle image will be described with reference to  FIG. 12 . In the present example, the corner angle image detecting processor  234 A first applies segmentation to the B-scan image  1100  to detect the corneal region  1110  and the iris region  1120 . Further, the corner angle image detecting processor  234 A identifies the image region  1110   a  corresponding to the posterior corneal surface in the corneal region  1110  as a posterior corneal surface image, and identifies the image region  1120   a  corresponding to the anterior iris surface in the iris region  1120  as an anterior iris surface image. 
     Next, the corner angle image detecting processor  234 A searches for a position where the posterior corneal surface image  1110   a  and the anterior iris surface image  1120   a  intersect with one another, and sets the searched position as a corner angle. In the present example, the intersection point  1130  between the posterior corneal surface image  1110   a  and the anterior iris surface image  1120   a  may be identified as a corner angle image, or the vicinity region (neighbourhood region)  1140  of the intersection point  1130  may be identified as a corner angle image. 
     &lt;Iris Image Detecting Processor  235 A&gt; 
     The iris image detecting processor  235 A is configured to detect an iris image by analyzing the OCT image constructed by the image constructing unit  220  based on the data obtained by the OCT scan for the scan area set by the scan area setting processor  232 A. The iris image detection may be executed based on a predetermined feature (characteristic) such as brightness, a position, and a shape, as in the case with the corneal image detection performed by the ophthalmic apparatus  1  described above. The iris image detection may include image processing such as segmentation. 
     &lt;Position Judging Processor  236 A&gt; 
     The position judging processor  236 A is configured to judge whether the corner angle image detected by the corner angle image detecting processor  234 A is located within a predetermined area in an image frame. The predetermined area in the image frame is referred to as the first area. 
     The area (first allowable area) in the image frame that serves as a reference (criterion) for the corner angle image position judgement may be set in advance, or may be set for individual OCT images. As an example of the latter, the first allowable area may be set based on the state or condition of the site (tissue) depicted in the OCT image. For example, the position judging processor  236 A may set the first allowable area based on the depiction position, the size, or the like of the cornea, and/or, the depiction position, the size, or the like of the iris. 
     In addition to the corner angle image detection, the present embodiment example may be capable of performing iris image detection. In the case where the iris image detection is executable, both a corner angle image and an iris image may be detected from a single OCT image. If both a corner angle image and an iris image are detected, the position judging processor  236 A may perform a judgement of whether the corner angle image is located within the first allowable area in the frame (imaged area) of the OCT image, and also perform a judgement of whether the iris image is located within the second allowable area in the frame of the OCT image. 
     As described above for the ophthalmic apparatus  1 , in the case of repetitively applying an OCT scan of a predetermined pattern to the anterior segment to acquire time series OCT images, the corner angle image detecting processor  234 A may detect a corner angle image from each of the OCT images acquired. For each of the OCT images from which a corner angle has been detected, the position judging processor  236 A may perform a judgement of whether the detected corner angle image is located within the first allowable area in the corresponding OCT image frame. 
     In the case of repetitively applying an OCT scan of a predetermined pattern to the anterior segment to acquire time series OCT images, detecting a corner angle image from each of the OCT images by the corner angle image detecting processor  234 A, and detecting an iris image from each of the OCT images by the iris image detecting processor  235 A, the position judging processor  236 A may perform, for each of the OCT images from which a corner angle image and an iris image has been detected, a judgement of whether the corner angle image is located within the first allowable area in the corresponding OCT image frame and also a judgement of whether the iris image is located within the second allowable area in the corresponding OCT image frame. 
     The morphology or aspect (e.g., position, shape, size) of the plurality of first allowable areas set respectively for the plurality of OCT images may be the same as each other, or may be at least partially different. The same applies to the plurality of second allowable areas. 
     The process of judging whether the corner angle image is located within the first allowable area may be, for example, carried out by making a judgement of whether at least part of the one or more pixels forming the corner angle image are included in the first allowable area. Alternatively, the judgement process may be carried out by making a judgement of whether all of the one or more pixels forming the corner angle image are included in the first allowable area. 
     Likewise, the process of judging whether the iris image is located within the second allowable area may be, for example, carried out by making a judgement of whether at least part of the one or more pixels forming the iris image are included in the second allowable area. Alternatively, the judgement process may be carried out by making a judgement of whether all of the one or more pixels forming the iris image are included in the second allowable area. 
     The case where the B-scan image  1200  illustrated in  FIG. 13  is used for the position judgement process will be described. The B-scan image  1200  contains the corneal region (corneal image)  1210  and the iris region (iris image)  1220 . The reference character  1230  denotes a corner angle image detected from the B-scan image  1200  by the corner angle image detecting processor  234 A. 
     The first allowable area  1200   a  and the second allowable area  1200   b  are set in the B-scan image  1200 . In the present example, the first allowable area  1200   a  is set as a rectangular region, and the second allowable area  1200   b  is set as a range (interval) in the z direction. The morphology or aspect of an allowable area is not limited to these. 
     The position judging processor  236 A performs a judgement of whether the corner angle image  1230  is located within the first allowable area  1200   a,  and performs a judgement of whether the iris image  1220  is located within the second allowable area  1200   b.  As such, in the case where two or more position judgements are to be made, the position judging processor  236 A typically outputs a judgement result indicating “position OK (position is appropriate (adequate, proper))” if satisfying results have been obtained in all the position judgements. 
     The position judging processor  236 A may be configured to output a judgement result indicating “position OK” if satisfying results have been obtained in the arbitrary number (one or more) of position judgements in the case where a plurality of position judgements is to be made. Alternatively, the position judging processor  236 A may be configured to prioritize a judgement result issued by any one or more position judgements from among a plurality of position judgements. 
     &lt;Operation&gt; 
     An operation of the ophthalmic apparatus  1 A according to the present embodiment example will be described.  FIG. 14A  and  FIG. 14B  show an example of the operation of the ophthalmic apparatus  1 A according to the present embodiment example. 
     (S 21 : Start Infrared Moving Image Photography of Anterior Segment) 
     To begin with, the fundus camera unit  2  of the ophthalmic apparatus  1 A starts the infrared moving image photography of the anterior segment of the subject&#39;s eye E. Frames acquired by the infrared moving image photography (anterior segment images) are transferred to the data processor  230  via the controller  210 . The transfer is executed as real time processing. 
     (S 22 : Determine Destination) 
     The destination determining processor  231 A analyzes the anterior segment image transferred from the fundus camera unit  2  to determine a destination of the OCT optical system. The destination is a position suitable for applying an OCT scan to a region containing the corner angle of subject&#39;s eye E. For example, the destination determining processor  231 A may analyze the anterior segment image to detect the pupil center and the iris outer edge, and determine a straight line that passes through the pupil center and extends along the x direction. Then, the destination determining processor  231 A may determine an intersection point between the straight line and the iris outer edge, and set the position of the intersection point to the destination. The series of processes is, for example, real time processing executed for each of the anterior segment images transferred from the fundus camera unit  2 . 
     (S 23 : Move OCT Optical System) 
     The movement controller  2101 A moves the OCT optical system by controlling the movement mechanism  150  based on the destination determined in the step S 22 . Typically, the movement controller  2101 A moves the OCT optical system such that the optical axis of the OCT optical system passes through the intersection point between the straight line and the iris outer edge. This movement control is executed as real time processing. 
     (S 24 : Set Conditions Such as OCT Scan Area) 
     The ophthalmic apparatus  1 A of the present embodiment example sets conditions to be applied to the repetitive OCT scan that will be started in the next step S 25 . 
     One of the OCT scan conditions set in the present step is a scan area. The scan area setting processor  232 A sets a scan area in a region that passes through the iris outer edge of the anterior segment of the subject&#39;s eye E. For example, the scan area setting processor  232 A may set a scan area to pass through the intersection point between the straight line and the iris outer edge. Further, the scan area setting processor  232 A may set a scan line (B-scan) that is located along the straight line and whose scan center is located at the intersection point. More generally, the scan area setting processor  232 A may set a scan area to pass through the destination determined in the step S 22 . 
     Note that the scan area setting process may include setting of a OCT scan pattern and setting of a location to which an OCT scan is applied. 
     (S 25 : Start Repetitive OCT Scan) 
     The scan controller  2102 A starts the repetitive OCT scan under the conditions set in the step S 24 . 
     A repetitive OCT scan is typically a scan mode in which an OCT scan of the same pattern is repetitively applied to the anterior segment, whereby time series OCT images are acquired. A typical example of a repetitive OCT scan is a scan mode of repetitively performing a B-scan centered on the optical axis position of the OCT optical system. According to such a repetitive B-scan, the B-scan that passes through the aforementioned intersection point or the vicinity thereof (and thus, passing through the corner angle or the vicinity thereof) may be applied at a high repetition frequency. 
     A repetitive OCT scan yields data sets acquired through respective OCT scans. The image constructing unit  220  constructs a plurality of OCT images based respectively on a plurality of data sets sequentially acquired by the repetitive OCT scan. When performing a repetitive B-scan, a plurality of data sets is sequentially acquired in accordance with the repetition of the B-scan. The image constructing unit  220  constructs a plurality of B-scan images based respectively on the plurality of data sets. 
     (S 26 : Calculate Image Quality Evaluation Value) 
     The image quality evaluating processor  233 A analyzes each of the plurality of OCT images (or part of the plurality of OCT images) sequentially acquired by the repetitive OCT scan started in the step S 25 , to calculate an image quality evaluation value for each of the OCT images. This processing is executed as real time processing. 
     (S 27 : Is Image Quality Evaluation Value Equal to or Greater than Threshold?) 
     The image quality evaluating processor  233 A judges whether the image quality evaluation value calculated in the step S 26  is equal to or greater than a predetermined threshold. 
     The process proceeds to the step S 29  if the image quality evaluating processor  233 A judges that the image quality evaluation value is equal to or greater than the predetermined threshold (S 27 : Yes). 
     The process proceeds to the step S 28  if the image quality evaluating processor  233 A judges that the image quality evaluation value is less than the predetermined threshold (S 27 : No). 
     (S 28 : Control Polarization Device) 
     If the image quality evaluating processor  233 A judges that the image quality evaluation value is less than the predetermined threshold (S 27 : No), the polarization controller  2103 A controls the polarization device  118  (and/or the polarization device  103 ) to obtain a larger image quality evaluation value to be calculated next in the step S 26 . 
     The steps S 26  to S 28  are repeated until “Yes” is issued as a judgement result in the step S 27 . Note that the ophthalmic apparatus  1 A may be configured to issue an error if the steps S 26  to S 28  have been repeated a predetermined number of times or have been repeated for a predetermined duration of time. 
     (S 29 : Detect Corner Angle Image and Iris Image) 
     The corner angle image detecting processor  234 A analyzes each of the plurality of OCT images (or part of the plurality of OCT images) sequentially acquired by the repetitive OCT scan started in the step S 25 , to detect a corner angle image from each of the plurality of OCT images. In addition, the iris image detecting processor  235 A analyzes each of the plurality of OCT images (or part of the plurality of OCT images) to detect an iris image from each of the plurality of OCT images. These processes are executed as real time processing. 
     (S 30 : Judge Positions of Corner Angle Image and Iris Image) 
     For the corner angle image and the iris image detected from the same OCT image in the step S 29 , the position judging processor  236 A judges whether the corner angle image is included in the first allowable area in the image frame, and also judges whether the iris image is included in the second allowable area. 
     (S 31 : Are Both Positions Located Within Allowable Areas?) 
     The process proceeds to the step S 32  if the position judging processor  236 A judges not only that the corner angle image is located within the first allowable area and but also that the iris image is located within the second allowable area (S 31 : Yes) as the result of the position judgements made in the step S 30 . 
     The process returns to the step S 29  if the position judging processor  236 A judges that the corner angle image is not located inside the first allowable area, or judges that the iris image is not located inside the second allowable area (S 31 : No). Then, the steps S 29  to S 31  are repeated until “Yes” is issued as a judgement result in the step S 31 . Note that the ophthalmic apparatus  1 A may be configured to issue an error if the steps S 29  to S 31  have been repeated a predetermined number of times or have been repeated for a predetermined duration of time. 
     In another example, the ophthalmic apparatus  1 A may be configured to return the process to the step S 26  if the position judging processor  236 A judges that the corner angle image is not located inside the first allowable area, or judges that the iris image is not located inside the second allowable area (S 31 : No). If this is the case, the steps S 26  to S 31  are repeated until “Yes” is issued as a judgement result in both the steps S 27  and S 31 . Note that the ophthalmic apparatus  1 A may be configured to issue an error if part or all of the steps S 26  to S 31  have been repeated a predetermined number of times or have been repeated for a predetermined duration of time. 
     Note that the conditions for the process to proceed to the step S 32  are not limited to the examples described above. For example, a condition of the transition to the step S 32  may be a judgement made by the position judging processor  236 A that the corner angle image is located within the first allowable area, or that the iris image is located within the second allowable area. Alternatively, a condition of the transition may be a judgement made by the position judging processor  236 A that the corner angle image is located within the first allowable area. If this is the case, the iris image need not be considered. 
     (S 32 : Perform OCT Scan for Diagnosis) 
     If the position judging processor  236 A has issued “Yes” as a judgement result in the step S 31 , then the step S 32  is started. At this stage, the alignment state of the OCT optical system with respect to the anterior segment (the corner angle) and the image quality of the OCT image acquired are both adequate. 
     The scan controller  2102 A applies an OCT scan to the anterior segment at the timing when such adequate conditions are secured. The image constructing unit  220  then constructs an OCT image from the data acquired by the OCT scan applied. The data processor  230 A may also process and/or analyze this OCT image. 
     The OCT image acquired in the step S 32  is typically used for diagnosis, and its scan condition is generally different from the condition for the repetitive OCT scan started in the step S 25 . Typically, the OCT image obtained in the step S 32  has higher definition. Further, arbitrary conditions of the OCT image obtained in the step S 32  such as the scan pattern and/or the size of the scan area may be different from those of the repetitive OCT scan started in the step S 25 . 
     With the above, the operation example illustrated in  FIG. 14A  and  FIG. 14B  is terminated (End). 
     &lt;Effects&gt; 
     Some effects of the ophthalmic apparatus  1 A according to the present embodiment example will be described. 
     The ophthalmic apparatus  1 A of the present embodiment example includes an OCT optical system, the image constructing unit  220 , the scan area setting processor  232 A, the scan controller  2102 A, the image quality evaluating processor  233 A, the corner angle image detecting processor  234 A, and the position judging processor  236 A. 
     The OCT optical system is an optical system configured for applying an OCT scan to the anterior segment of the subject&#39;s eye E. The OCT optical system in the present embodiment example includes at least the series of elements forming the measurement arm in the fundus camera unit  2 . The image constructing unit  220  is configured to construct an OCT image based on data acquired by the OCT scan. 
     The scan area setting processor  232 A is configured to set a scan area in a region passing through an iris outer edge of the anterior segment. The scan controller  2102 A (the first scan controller) is configured to perform control of the OCT optical system to apply an OCT scan to the scan area set by the scan area setting processor  232 A. The image constructing unit  220  is configured to construct an OCT image based on data acquired by the OCT scan. 
     The image quality evaluating processor  233 A is configured to calculate an image quality evaluation value of the OCT image based on the data acquired by the OCT scan applied to the scan area. 
     The corner angle image detecting processor  234 A is configured to analyze the OCT image constructed by the image constructing unit  220  based on the data acquired by the OCT scan applied to the scan area, to detect a corner angle image. Note that the OCT image processed by the image quality evaluating processor  233 A and the OCT image processed by the corner angle image detecting processor  234 A may be the same as each other, or may be different from each other. 
     The position judging processor  236 A is configured to judge whether the corner angle image detected by the corner angle image detecting processor  234 A is located within a first area in an image frame. 
     The second scan controller  2102 A (the second scan controller) is configured to perform control of the OCT optical system to apply an OCT scan of a predetermined pattern to the anterior segment, if the image quality evaluation value calculated by the image quality evaluating processor  233 A is equal to or greater than a predetermined threshold and the position judging processor  236 A judges that the corner angle image is located within the first area. 
     The conditions for applying the OCT scan of the predetermined pattern to the anterior segment in the present embodiment example include at least the following conditions: a condition that the image quality evaluation value is equal to or greater than the predetermined threshold; and a condition that the corner angle image is located within the first area. The conditions for applying the OCT scan of the predetermined pattern to the anterior segment may further include one or more of other conditions. The position judgement of the iris image is one example of the other conditions. 
     According to the ophthalmic apparatus  1 A configured in this way, preparatory operations can be carried out automatically while checking whether or not necessary conditions are met, and an OCT scan (imaging, measurement, etc.) can be executed at an appropriate timing at which the necessary conditions are met. The preparatory operations here include, for example, the alignment of the OCT optical system with respect to the corner angle, the adjustment of a depiction position of a target site in an image frame, and the control of the image quality. 
     Having automated the preparatory operations for applying an OCT scan to the corner angle of a living eye in this way, even a person unfamiliar with the operation of the ophthalmic apparatus can easily conduct an OCT corner angle examination. This also makes it possible for a subject to have an OCT corner angle examination alone. As a result, the burdens on the subject and the examiner in the OCT corner angle examination is reduced. 
     Further, the ophthalmic apparatus of the present embodiment example in which the preparatory operations are automated is advantageous if the ophthalmic apparatus, to which an OCT technique and technology are applied, is to be installed in an optician&#39;s store, a drug store, or a patient&#39;s home in order to use the apparatus for screening of eye diseases. 
     The ophthalmic apparatus  1 A of the present embodiment example includes the fundus camera unit  2  (anterior segment photographing system), the movement mechanism  150 , the destination determining processor  231 A, and the movement controller  2101 A. The fundus camera unit  2  is configured to photograph the anterior segment. The movement mechanism  150  is configured to move (part or all of) the OCT optical system. The destination determining processor  231 A is configured to analyze an anterior segment image acquired by the fundus camera unit  2  to determine a destination of the OCT optical system. The movement controller  2101 A is configured to perform control of the movement mechanism  150  based on the destination determined by the destination determining processor  231 A. The scan area setting processor  232 A performs scan area setting after the movement controller  2101 A performs the control of the movement mechanism  150 . 
     According to the ophthalmic apparatus  1 A configured in this way, (rough) alignment can be performed based on an anterior segment image before the setting of the OCT scan area, and thus, before the application of the OCT scan. This facilitates processing based on the OCT image performed after the start of the OCT scan. 
     The destination determining processor  231 A may be configured to analyze the anterior segment image acquired by the fundus camera unit  2  to detect a pupil center and an iris outer edge, and determine the destination based on the pupil center and the iris outer edge detected. 
     Further, the destination determining processor  231 A may be configured to determine a straight line that passes through the pupil center and extends along (lies along) a predetermined direction, and determine an intersection point between the straight line and the iris outer edge to be the destination. 
     If this is the case, the scan area setting processor  232 A may be configured to set the scan area that passes through the intersection point determined. 
     In addition, the scan area setting processor  232 A may be configured to set a scan line (B-scan) along the aforementioned straight line wherein the center of the scan line is located at the intersection point. 
     More generally, the scan area setting processor  232 A may be configured to set the scan area that passes through the destination determined by the destination determining processor  231 A. 
     According to some of the configurations illustrated here, a suitable and specific method or technique can be employed for determining the destination and setting the scan area. For example, alignment and OCT scan condition setting for OCT corner angle examination can be performed in an appropriate and automatic manner. 
     The OCT optical system may be configured to apply a repetitive OCT scan to the scan area set by the scan area setting processor  232 A after the control of the movement mechanism  150 . If this is the case, the image constructing unit  220  may construct a plurality of OCT images based respectively on a plurality of data sets successively acquired by the repetitive OCT scan. 
     The repetitive OCT scan may be a repetitive B-scan. Further, the OCT optical system may continue the repetitive OCT scan until at least an image quality evaluation value equal to or greater than the predetermined threshold is obtained by the image quality evaluating processor  233 A. 
     According to the ophthalmic apparatus  1 A configured in this way, a plurality of OCT images (time series OCT images) synchronized with the repetition of the OCT scan can be obtained. The time series OCT images may be employed and utilized for various purposes such as alignment operation, depiction position judgement processing, image quality evaluation processing, and moving image display operation. 
     The ophthalmic apparatus  1 A of the present embodiment example includes the iris image detecting processor  235 A. The iris image detecting processor  235 A is configured to analyze the OCT image constructed based on the data acquired by the OCT scan applied to the scan area set by the scan area setting processor  232 A, to detect an iris image. 
     The position judging processor  236 A may be configured to judge whether the corner angle image detected by the corner angle image detecting processor  234 A is located within the first area in the image frame and also judges whether the iris image detected by the iris image detecting processor  235 A is located within a second area. 
     The scan controller  2102 A (second scan controller) may be configured to perform the control of the OCT optical system to apply the OCT scan of the predetermined pattern to the anterior segment, if the image quality evaluation value calculated by the image quality evaluating processor  233 A is equal to or greater than the predetermined threshold and the position judging processor  236 A judges that the corner angle image is located within the first area and the iris image is located within the second area. 
     According to the ophthalmic apparatus  1 A configured in this way, the OCT scan can be performed at a more appropriate timing because the condition regarding the position of the iris image can be taken into consideration in addition to the condition regarding the image quality and the condition regarding the position of the corner angle image. 
     The corner angle image detecting processor  234 A may be configured: to analyze the OCT image constructed based on the data acquired by the OCT scan applied to the scan area set by the scan area setting processor  232 A to detect a posterior corneal surface image and an anterior iris surface image; and then to detect an intersection position of the posterior corneal surface image and the anterior iris surface image as the corner angle of the subject&#39;s eye E. 
     According to such a configuration, an appropriate and specific method or technique can be provided for detecting a corner angle image. 
     The image quality evaluating processor  233 A may be configured to calculate, as the image quality evaluation value, a ratio of a signal of an anterior segment region to a noise of a background region in the OCT image constructed by the image constructing unit  220 . Typically, the image quality evaluating processor  233 A may be configured to calculate, as the image quality evaluation value, a ratio of a signal of a corneal region to a noise of a first background region adjacent to the corneal region in the OCT image constructed by the image constructing unit  220 . 
     Further, the image quality evaluating processor  233 A may be configured to calculate, as the image quality evaluation value, a ratio of a signal of an iris region to a noise of a second background region adjacent to the iris region in the OCT image constructed by the image constructing unit  220 . 
     According to such a configuration, an appropriate and specific method or technique can be provided for evaluating the image quality of the OCT image in the corner angle OCT examination. 
     The OCT optical system includes a measurement arm and a reference arm. The measurement arm is configured to guide the measurement light LS to the anterior segment, and the reference arm is configured to guide the reference light LR that is superposed on return light of the measurement light LS returned from the anterior segment. At least one of the measurement arm and the reference arm includes a polarization device. The polarization device changes a polarization state of light guided. In the ophthalmic apparatus  1 A of the present embodiment example, the polarization device  118  is provided in the reference arm. Further, the ophthalmic apparatus  1 A of the present embodiment example includes the polarization controller  2103 A. The polarization controller  2103 A is configured to perform control of the polarization device to increase the image quality evaluation value (e.g., the ratio of the signal in the anterior segment region to the noise in the background region) calculated by the image quality evaluating processor  233 A. 
     According to the ophthalmic apparatus  1 A configured as described above, the image quality of an OCT image can be improved if the image quality is low. 
     &lt;Control Method of Ophthalmic Apparatus, Program, Recording Medium&gt; 
     The present embodiment example described above also provide a method of controlling an ophthalmic apparatus. The ophthalmic apparatus to which this control method can be applied includes an OCT optical system that applies an OCT scan to an anterior segment of a subject&#39;s eye, an image constructing unit that constructs an image based on data acquired by the OCT scan. 
     The control method of the present embodiment example includes a scan area setting step, a first scan control step, an image quality evaluating step, a corner angle image detecting step, a position judging step, and a second scan control step. 
     The scan area setting step sets a scan area in a region passing through an iris outer edge of the anterior segment of the subject&#39;s eye. The first scan control step performs control of the OCT optical system to apply an OCT scan to the scan area set. The image quality evaluating step calculates an image quality evaluation value of an OCT image constructed by the image constructing unit based on data acquired by the OCT scan applied to the scan area set. The corner angle image detecting step detects a corner angle image by analyzing the OCT image constructed by the image constructing unit based on the data acquired by the OCT scan applied to the scan area set. The position judging step performs a judgement of whether the corner angle image detected is located within a first area in an image frame. The second scan control step performs control of the OCT optical system to apply an OCT scan of a predetermined pattern to the anterior segment, if the image quality evaluation value is equal to or greater than a predetermined threshold and the corner angle image is judged to be located within the first area. 
     Any of the processes that can be executed by the ophthalmic apparatus  1 A of the present embodiment example, can be combined with the control method described above. 
     According to such a control method, the same effects are achieved as those of the ophthalmic apparatus  1 A of the present embodiment example. 
     It is possible to configure a program that causes the ophthalmic apparatus to execute such a control method. The program may include, for example, any of the programs for operating the ophthalmic apparatus  1 A of the present embodiment example. 
     Also, it is possible to create a computer-readable non-transitory recording medium storing such a program. The non-transitory recording medium may be in any form, and examples thereof include a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, and the like. 
     &lt;Some Embodiment Examples Capable of Selectively Perform a Plurality of Preparatory Operation Modes&gt; 
     Some embodiment examples applicable to the corneal OCT and some embodiment examples applicable to the corner angle OCT have been described above. These embodiment examples provide techniques or technologies for automating preparatory operations for applying OCT to the anterior segment of a living eye. 
     On the other hand, there also exists a technique or technology for automating operations for applying OCT to the fundus of a living eye. For example, the technique or technology disclosed in the following document is known: Japanese Unexamined Patent Application Publication No. 2014-039870. 
     In addition to the same OCT optical system and the same image constructing device (image constructing unit) as those of the ophthalmic apparatus  1  described above, the ophthalmic apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2014-039870 includes an alignment device, a focusing device, an image position judging device, a judging device, and a control device. 
     The alignment device is an element that performs alignment of the OCT optical system with respect to the fundus of the subject&#39;s eye, and includes, for example, the alignment optical system  50  of the ophthalmic apparatus  1  described above. The focusing device is an element that performs focusing of the OCT optical system with respect to the fundus of the subject&#39;s eye, and includes, for example, the OCT focusing lens  43  and the OCT focus driver  43 A of the ophthalmic apparatus  1  described above. 
     The image position judging device is an element that judges the position of an image of the fundus in an image frame based on data acquired by the OCT optical system. For example, the data processor  230  of the ophthalmic apparatus  1  described above makes the judgement. 
     The judging device judges the adequacy of the position of the OCT optical system and the adequacy of the in-focus state. Further, the judging device judges the adequacy of the position of the image of the fundus in the image frame. In addition, after all of the judgement for the adequacy of the position of the OCT optical system, the judgement for the adequacy of the in-focus state, and the judgement for the adequacy of the position of the image of the fundus have been completed, the judging device makes all the judgements again. The series of judgements is made, for example, by the controller  210  and the data processor  230  of the ophthalmic apparatus  1  described above. 
     The control device controls the OCT optical system and the image constructing device to perform a fundus OCT scan if the judging device has judged, in the re judgement for the adequacies, that the position of the OCT optical system, the in-focus state, and the position of the image of the fundus are all appropriate. The control is executed, for example, by the controller  210  of the ophthalmic apparatus  1  described above. 
     A description will be given below of some embodiment examples in which such a plurality of preparatory operation modes may be employed in a selective manner. The ophthalmic apparatus stores in advance, for example, a plurality of programs respectively corresponding to the plurality of preparatory operation modes. Alternatively, the ophthalmic apparatus may access a storage that stores a plurality of programs respectively corresponding to the plurality of preparatory operation modes. 
     The ophthalmic apparatus (selecting device) first performs selection of a preparatory operation mode. The preparatory operation mode selection is performed manually or automatically. 
     If manual selection is employed, for example, the ophthalmic apparatus (display control device) displays a GUI for selecting a preparatory operation mode (or a mode equivalent thereto) on a display device. The user selects a desired preparatory operation mode by operating an operation device. 
     If automatic selection is employed, for example, the ophthalmic apparatus (data acquiring device) acquires a disease name and/or an examination order from the electronic medical record data. In addition, the ophthalmic apparatus (selecting device) selects a preparatory operation mode according to the data acquired from the electronic medical record data. Here, correspondence information (e.g., table information) in which various kinds of information is associated with each of the plurality of preparatory operation modes may be prepared. Automatic selection may be implemented by referring to the correspondence information. 
     The ophthalmic apparatus (control device, data processing device) executes a series of preparatory operations according to the program(s) corresponding to the preparatory operation mode(s) selected. 
     According to such an ophthalmic apparatus, an appropriate preparatory operation(s) may be performed in a selective manner according to the type of examination to be conducted for the subject&#39;s eye. As a result of this, operability can be improved and time required for the examination can be shortened. 
     In addition, even a person unfamiliar with the operation of the ophthalmic apparatus can easily conduct an OCT examination. This also makes it possible for a subject to have an OCT examination alone. As a result, the burdens on the subject and the examiner in the OCT examination is reduced. 
     Further, the ophthalmic apparatus of the present embodiment example is advantageous if an ophthalmic apparatus to which an OCT technique and technology are applied is to be installed in an optician&#39;s store, a drug store, or a patient&#39;s home in order to use the apparatus for screening of eye diseases. 
     The aspects described above are merely illustrative of the implementation of the present invention. A person who intends to implement the present invention may apply any modification (omission, substitution, replacement, addition, etc.) to the above aspects. 
     EXPLANATION OF REFERENCE CHARACTERS 
     
         
           1  Ophthalmic apparatus 
           150  Movement mechanism 
           210  Controller 
           2101  Movement controller 
           2102  Scan controller 
           2103  Polarization controller 
           2104  Display controller 
           220  Image constructing unit 
           230  Data processor 
           231  Destination determining processor 
           232  Artifact detecting processor 
           233  Corneal image detecting processor 
           234  Position judging processor 
           235  Image quality evaluating processor 
           236  Artifact eliminating processor 
           241  Display device 
           1 A Ophthalmic apparatus 
           210 A Controller 
           2101 A Movement controller 
           2102 A Scan controller 
           2103 A Polarization controller 
           2104 A Display controller 
           230 A Data processor 
           231 A Destination determining processor 
           232 A Scan area setting processor 
           233 A Image quality evaluating processor 
           234 A Corner angle image detecting processor 
           235 A Iris image detecting processor 
           236 A Position judging processor