Patent Publication Number: US-2023148300-A1

Title: Electronic device, method of controlling the same, and storage medium

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a technique for changing a display area of a display provided in an electronic device. 
     Description of the Related Art 
     Some models of image capturing devices, such as a digital camera and a video camera, use an electronic viewfinder (EVF) for visually confirming a subject. The electronic viewfinder is configured so that a small display provided inside the camera can be viewed magnified through an ocular optical system configured by a plurality of lenses. A user can view a magnified display image by looking into this ocular optical system. 
     Recently, there has been a trend of desiring a higher display magnification for viewfinders of cameras. The higher the magnification, the bigger the image can be seen, so it has the merit that it is easier to confirm focus. In addition, the user feels more immersed with a viewfinder with a large field of view, which makes it more fun to capture images. 
     However, when a distance from the viewfinder to the eye increases (e.g., when the user looks into the viewfinder while wearing glasses, and the like), if the display area is too large, there will be a problem that a portion of the display area will be shielded, resulting in poorer visibility and making framing more difficult. 
     As one countermeasure for this problem, Japanese Patent Laid-Open No. 2010-016669 discloses a technique that allows a user to arbitrarily set the display area of the viewfinder. 
     However, in the prior art disclosed in Japanese Patent Laid-Open No. 2010-01666, when changing the display area of the viewfinder, it is necessary to operate from a hierarchical menu. Therefore, there is a problem that an operation for changing the display area is cumbersome for users who, at times, capture images while wearing glasses and, at other times, capture images without wearing glasses. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the problems described above and provides an electronic device capable of displaying an image in a display area of an appropriate size for a user. 
     According to a first aspect of the present invention, there is provided an electronic device comprising: a display configured to display an image; an ocular optical system configured to view the display; and at least one processor or circuit configured to function as a control unit configured to control the display so as to change a display area of the display based on a distance from the ocular optical system to an eye of a user looking into the ocular optical system. 
     According to a second aspect of the present invention, there is provided a method of controlling an electronic device including a display configured to display an image and an ocular optical system configured to view the display, the method comprising: controlling the display so as to change a display area of the display based on a distance from the ocular optical system to an eye of a user looking into the ocular optical system. 
     According to a third aspect of the present invention, there is provided a non-transitory computer-readable storage medium storing a program for causing a computer to execute the method of controlling an electronic device including a display configured to display an image and an ocular optical system configured to view the display, the method comprising: controlling the display so as to change a display area of the display based on a distance from the ocular optical system to an eye of a user looking into the ocular optical system. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1 A and  1 B  are diagrams illustrating an external appearance of a digital, interchangeable-lens camera, which is a first embodiment of an electronic device of the present invention. 
         FIG.  2    is a cross-sectional view of the camera of the first embodiment. 
         FIG.  3    is a cross-sectional view of an optical system that includes a line-of-sight detection mechanism. 
         FIGS.  4 A and  4 B  are perspective views of the optical system that includes the line-of-sight detection mechanism. 
         FIG.  5    is an optical path diagram for when detecting a line of sight using the line-of-sight detection mechanism. 
         FIG.  6    is a schematic diagram for explaining principles of a method of detecting a field of view. 
         FIGS.  7 A and  7 B  are schematic diagrams illustrating an image of an eye. 
         FIG.  8    is a flowchart for explaining an operation for detecting a line of sight. 
         FIG.  9    is a schematic diagram illustrating a distance from the final surface of an ocular optical system to an eye. 
         FIGS.  10 A and  10 B  are schematic diagrams illustrating how to change a display area of a display device. 
         FIGS.  11 A and  11 B  are schematic diagrams illustrating changing a display of targets used for calibration based on the distance from the final surface of the ocular optical system to an eye. 
         FIG.  12    is a flowchart for explaining an operation for changing the display area of the display device. 
         FIGS.  13 A and  13 B  are schematic diagrams illustrating how to change the display area of the display device in a second embodiment. 
         FIG.  14    is a flowchart for explaining an operation for changing the display area of the display device in a third embodiment. 
         FIG.  15    is a flowchart for explaining an operation for changing the display area of the display device in a fourth embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, embodiments will be described in detail with reference to the attached drawings. Note, the following embodiments are not intended to limit the scope of the claimed invention. Multiple features are described in the embodiments, but limitation is not made to an invention that requires all such features, and multiple such features may be combined as appropriate. Furthermore, in the attached drawings, the same reference numerals are given to the same or similar configurations, and redundant description thereof is omitted. 
     First Embodiment 
     &lt;Description of Configuration&gt; 
       FIGS.  1 A and  1 B  are diagrams illustrating an external appearance of a digital, interchangeable-lens camera  1  (hereinafter, the camera), which is a first embodiment of an electronic device of the present invention. The electronic device referred to in the present invention is not limited to a digital camera and encompasses devices for displaying information, such as images and text, and any electronic device capable of detecting a line-of-sight of a user viewing an optical image through an ocular optical system. These electronic devices may include, for example, mobile phones, game machines, tablet terminals, personal computers, watch and eyewear-type information terminals, head-mounted displays, binoculars, and the like. 
       FIG.  1 A  is a front perspective view of the camera  1 , and  FIG.  1 B  is a rear perspective view of the camera  1 . 
     As illustrated in  FIG.  1 A , the camera  1  includes an image capturing lens unit  1 A and a camera body  1 B. The camera body  1 B is provided with a release button  5 , which is an operation member for receiving an image capturing operation from a user (photographer). As illustrated in  FIG.  1 B , the back of the camera body  1 B is provided with an ocular window frame  121 , which the user looks through to view a display device  6 , which is included in the camera body  1 B and will be described later (see  FIG.  3   ). 
     A display unit in the present embodiment includes the display device  6 . The ocular window frame  121  forms a viewing port  13  and protrudes outward (from the back side) with respect to the camera body  1 B. The back of the camera body  1 B is also provided with operation members  41  to  43  for receiving various operations from the user. For example, the operation member  41  is a touch panel that accepts a touch operation of the user, the operation member  42  is an operation lever that can be pushed down in respective directions, and the operation member  43  is a four-direction key that can be pushed in each of the four directions. The operation member  41  (touch panel) is provided with a display panel  40 , such as a liquid crystal panel (see  FIG.  3   ), and includes a function of displaying an image. 
       FIG.  2    is a cross-sectional side view of the camera  1  of the present embodiment and is a diagram illustrating an electrical block configuration in the camera  1 . The camera body  1 B includes an image capturing element  2  for capturing a subject image. The image capturing element  2  is an image capturing element configured by, for example, a CCD or CMOS sensor or the like; an optical image formed on an image capturing plane of the image capturing element  2  by an optical system of the image capturing lens unit  1 A is photoelectrically converted, and an obtained analog image signal is A/D-converted and outputted as image data. 
     The image capturing lens unit  1 A is configured to include an optical system that includes a zoom lens, a focus lens, a diaphragm, and the like and, when mounted on the camera body  1 B, guides a light beam from a subject to the image capturing element  2 , thereby forming an image of the subject on an image capturing plane of the image capturing element  2 . A diaphragm control unit  118 , a focus adjustment unit  119 , and a zoom control unit  120  each receive an instruction signal from a CPU  3  through a mount contact unit  117  and drive and control the diaphragm, the focus lens, and the zoom lens, respectively, in accordance with the instruction signal. 
     The CPU  3  provided in the camera body  1 B reads control programs for the respective blocks provided in the camera body  1 B from a ROM included in a memory unit  4 , deploys these in a RAM included in the memory unit  4 , and executes these. Thus, the CPU  3  controls the operation of the respective blocks provided in the camera body  1 B. The CPU  3  is connected to a line-of-sight detection unit  201 , a photometry unit  202 , an autofocus detection unit  203 , a signal input unit  204 , an eye-approach detection unit  208 , a distance calculation unit  209 , a display device driving unit  210 , a light source driving unit  205 , and the like. Further, the CPU  3  transmits a signal to the diaphragm control unit  118 , the focus adjustment unit  119 , and the zoom control unit  120  provided in the image capturing lens unit  1 A through a mount contact point  117 . In the present embodiment, the memory unit  4  includes a function of storing image capturing signals from the image capturing element  2  and a line-of-sight detection sensor  30 . 
     In a state in which an image of an eyeball is formed on the line-of-sight detection sensor  30  (CCD-EYE), the line-of-sight detection unit  201  performs A/D conversion of an output (an image of an eye in which the eyeball is captured) of the line-of-sight detection sensor  30  and transmits that result to the CPU  3 . The CPU  3  extracts feature points necessary for detecting a line of sight from the image of the eye in accordance with a predetermined algorithm, which will be described later, and calculates a line of sight (a gaze point in an image for visual confirmation) of the user from positions of the feature points. 
     Further, the distance calculation unit  209  calculates a distance  32  from the final surface of an ocular optical system  16 , which is illustrated in  FIG.  9   , to the eye. The distance calculation unit  209  calculates the distance  32  from the final surface of the ocular optical system  16  to the eye based on coordinates of cornea-reflected images on the line-of-sight detection sensor  30  and transmits an output value to the CPU  3 . The distance calculation unit  209  may obtain the distance  32  from a table or the like in which the distance  32  from the final surface of the ocular optical system  16  to the eye has been calculated in advance based on the coordinates of the cornea-reflected images. 
     The display device driving unit  210  determines the display area of the display device  6  based on the distance calculated by the distance calculation unit  209  and performs display. The eye-approach detection unit  208  transmits an output of an eye-approach detection sensor  50  to the CPU  3 . The CPU  3  calculates whether or not the user&#39;s eye has approached in accordance with a predetermined algorithm, which will be described later. The light source driving unit  205  drives infrared LEDs  18  to  27 , which are light sources, to be at a predetermined emission intensity in accordance with commands from the CPU  3 . 
     The photometry unit  202  performs amplification, logarithmic compression, A/D conversion and the like of a signal (more specifically, a luminance signal, which corresponds to the brightness of a field of view) obtained from the image capturing element  2 , which also serves as a photometric sensor, and transmits that result to the CPU  3  as field-of-view luminance information. 
     The autofocus detection unit  203  A/D-converts signal voltages from a plurality of detection elements (a plurality of sub-pixels), which are included in the pixels in the image capturing element  2  and are used for detecting a phase difference, and transmits them to the CPU  3 . The CPU  3  calculates, from signals of the plurality of detection elements, a distance to a subject corresponding to each focus detection point. This is a known technique, which is known as image plane phase difference AF. In the present embodiment, as an example, it is assumed that an image of a field of view (image for visual confirmation) in the viewfinder is divided and that there is a focus detection point at each of  180  locations, which have been obtained by division, on the image capturing plane. 
     The image processing unit  206  performs various kinds of image processing on image data stored in the RAM in the memory unit  4 . Specifically, various image processes for developing, displaying, and recording digital image data are performed, such as defect correction processing of pixels caused by an optical system or an image capturing element, demosaicing processing, white balance correction processing, color interpolation processing, and gamma processing, for example. 
     A switch SW 1 , which turns ON at a first stroke of the release button  5  and is for starting the camera  1 &#39;s photometry, focus detection, and line-of-sight detection operations and the like, and a switch SW 2 , which turns ON at a second stroke of the release button  5  and is for starting an image capturing operation are connected to the signal input unit  204 . An ON signal is inputted from the switch SW 1  or SW 2  to the signal input unit  204  and is then transmitted to the CPU  3 . The signal input unit  204  also receives operation inputs from the operation members  41  (a touch panel),  42  (a button), and  43  (arrow keys) illustrated in  FIG.  1 B . 
     A recording/output unit  207  records data, which includes image data, on a storage medium, such as a removable memory card, or outputs the data to an external device via an external interface. 
       FIG.  3    is a cross-sectional view of an optical system that includes a line-of-sight detection mechanism of the present embodiment and is a diagram obtained by cutting the camera  1  across a YZ plane, which is formed by a Y-axis and a Z-axis illustrated in  FIG.  1 A . 
     A shutter  44  and the image capturing element  2  are arranged in order in an optical axis direction of the image capturing lens unit  1 A. The back of the camera body  1 B is provided with the display panel  40 , which is used for operating the camera  1 , displaying menus for viewing and editing images obtained with the camera  1 , and displaying images. The display panel  40  is configured by a liquid crystal panel with a backlight, an organic EL panel, or the like. 
     A panel holder  7  is a panel holder for holding the display device  6  configured by an organic EL panel or the like, is bonded and fixed to the display device  6 , and configures a display panel unit  8 . 
     A first optical path splitting prism  9  and a second optical path splitting prism  10  are bonded by adhesion to configure an optical path splitting prism unit  11  (optical path splitting member). The optical path splitting prism unit  11  guides a light beam from the display device  6  to an eyepiece window  17  provided in the user&#39;s viewing port  13  and, conversely, guides, to the line-of-sight detection sensor  30  illustrated in  FIGS.  4 A and  4 B , light reflected from an eye (pupil) and the like and guided from the eyepiece window  17 . The display panel unit  8  and the optical path splitting prism unit  11  are fixed with a mask  12  therebetween and are formed into a unit. 
     The ocular optical system  16  is configured by a G 1  lens  13 , a G 2  lens  14 , and a G 3  lens  15 . The electronic viewfinder is configured such that the display panel unit  8  is seen magnified through the ocular optical system  16  so that the user can view a magnified display image. 
     The eyepiece window  17  is a transparent member that transmits visible light. An image displayed on the display panel unit  8  is viewed through the optical path splitting prism unit  11 , the ocular optical system  16 , and the eyepiece window  17 . 
     Illumination windows  20  and  21  are windows for hiding the infrared LEDs  18  and  19  so as not to be visible from the outside and are configured by resin that absorbs visible light and transmits infrared light. 
     In addition to being able to display menus and images similarly to the display panel  40  as a typical electronic viewfinder (EVF), the EVF provided in the camera body  1 B in the present embodiment is configured so as to be able to detect a line of sight of the user looking at the EVF and reflect a result of the detection in the control of the camera  1 . 
     Similarly to the display panel  40 , when the user is looking through the viewfinder, the display device  6  is used to display menus for operating the camera  1  and viewing and editing images obtained by the camera  1  and display images. The display device  6  is configured by a liquid crystal panel with a backlight, an organic EL panel, or the like. 
       FIGS.  4 A and  4 B  are a perspective view and a cross-sectional view of an optical system that includes a line-of-sight detection mechanism of the present embodiment.  FIG.  4 A  is a perspective view illustrating a configuration of the EVF in the present embodiment, and  FIG.  4 B  is a cross-sectional side view of an optical axis of the EVF. 
     The eyepiece window  17  is a transparent member that transmits visible light. An image displayed on the display panel  6  is viewed through the optical path splitting prism unit  11 , the ocular optical system  16 , and the eyepiece window  17 . 
     The infrared LEDs  18 ,  19 ,  22 ,  23 ,  24 ,  25 ,  26 , and  27  are arranged so as to irradiate infrared light toward the user&#39;s viewing port  13  from different positions and orientations. The illumination windows  20  and  21  are windows for hiding the infrared LEDs  18 ,  19 ,  22 ,  23 ,  24 ,  25 ,  26 , and  27  so as not to be visible from the outside and are configured by resin that absorbs visible light and transmits infrared light. 
     The infrared LED  18 ,  19 ,  23 , and  25  are infrared LEDs for close-range illumination. The infrared LED  22 ,  24 ,  26 , and  27  are infrared LEDs for long-range illumination. A line-of-sight detection optical system, which includes a diaphragm  28  and a line-of-sight image forming lens  29 , further guides reflected infrared light guided from the eyepiece window  17  by the optical path splitting prism unit  11  to the line-of-sight detection sensor  30 . The line-of-sight detection sensor  30  is configured by a solid-state image capturing element, such as a CCD or CMOS sensor. 
     The eye-approach detection sensor  50  is configured by a photodiode, which can be driven at a power that is lower than the line-of-sight detection sensor  30 , and the like. The infrared LED  22  for detecting a line of sight is also used as an infrared LED for detecting the approach of the eye. The infrared LED  22  illuminates the user&#39;s eye, and the eye-approach detection sensor  50  receives light diffusely reflected off the user. 
     In  FIG.  4 B , an image of an eyeball, which has been illuminated by infrared LEDs, of the user looking through the eyepiece window  17  enters the second optical path splitting prism  10  from a second surface  10   a  through the G3 lens  15 , the G2 lens  14 , and the G1 lens  13 . This optical path is indicated by  31   a . On a first surface  10   b  of the second optical path splitting prism is formed a dichroic film for reflecting infrared light. 
     An image of an eyeball illuminated by at least one of the infrared LEDs illustrated in  FIG.  4 A  is reflected by the first surface  10   b  toward the second surface  10   a . This reflected light path is indicated by  31   b . The infrared light that has passed the reflected light path  31   b  is totally reflected by the second surface  10   a , passes an image forming light path  31   c , and is formed into an image on the line-of-sight detection sensor  30  by the line-of-sight image forming lens  29  through the diaphragm  28 . 
     To detect a line of sight, a cornea-reflected image formed by a specular reflection of infrared LED by the cornea is used in conjunction with an eyeball image by illumination.  FIG.  5    illustrates an example of an optical path for light emitted from the infrared LEDs  18 ,  19 ,  23 , and  25  for close-range illumination from when it is specularly reflected by a cornea  611  of an eyeball until it is received by the line-of-sight detection sensor  30 . 
     &lt;Description of Operation for Detecting Line of Sight&gt; 
     A method of detecting a line of sight will be described with reference to  FIGS.  6 ,  7 A,  7 B, and  8   . 
       FIG.  6    is a diagram for explaining principles of a method of detecting a line of sight and is a schematic diagram of an optical system for performing line-of-sight detection. 
     As illustrated in  FIG.  6   , light sources  601   a  and  601   b  are arranged to be substantially symmetrical with respect to an optical axis of a light receiving lens  618  (corresponds to the line-of-sight image forming lens  29  in  FIG.  4 B ) and illuminates the user&#39;s eyeball  610 . Some of the light emitted from the light sources  601   a  and  601   b  and reflected by the eyeball  610  are focused on the line-of-sight detection sensor  620  (corresponds to the line-of-sight detection sensor  30  in  FIGS.  4 A,  4 B, and  5   ) by the light receiving lens  618 . 
       FIG.  7 A  is a schematic diagram of an eye image captured by the line-of-sight detection sensor  620  (an eyeball image projected on the line-of-sight detection sensor  620 ), and  FIG.  7 B  is a diagram illustrating an output intensity of the image capturing element in the line-of-sight detection sensor  620 .  FIG.  8    indicates a schematic flowchart of an operation for detecting a line of sight. 
     When an operation for detecting a line of sight is started, in step S 801  of  FIG.  8   , the CPU  3  causes the light sources  601   a  and  601   b  to emit light, irradiating infrared light of an emission intensity E 2  for line-of-sight detection toward the user&#39;s eyeball  610 . An image of the user&#39;s eyeball illuminated by the infrared light is formed on the line-of-sight detection sensor  620  through the light receiving lens  618  and is photoelectrically converted by the line-of-sight detection sensor  620 . By this, a processable electrical signal of an eye image is obtained. 
     In step S 802 , the CPU  3  obtains the eye image (an eye image signal; an electrical signal of the eye image) from the line-of-sight detection sensor  620  using the line-of-sight detection unit  201 . 
     In step S 803 , the CPU  3  obtains coordinates of points corresponding to cornea-reflected images Pd and Pe of the light sources  601   a  and  601   b  and a pupil center c from the eye image obtained in step S 802 . 
     The infrared light emitted from the light sources  601   a  and  601   b  illuminates the cornea  611  of the user&#39;s eyeball  610 . At this time, the cornea-reflected images Pd and Pe formed by some of the infrared light reflected on the surface of the cornea  611  is focused by the light receiving lens  618  and formed into an image on the line-of-sight detection sensor  620 , thereby becoming cornea-reflected images Pd′ and Pe′ in the eye image. Similarly, a light beam from edges a and b of a pupil  612  is also formed into an image on the line-of-sight detection sensor  620 , thereby becoming pupil edge images a′ and b′ in the eye image. 
       FIG.  7 B  is a diagram illustrating luminance information (a luminance distribution) of an area α′ in the eye image of  FIG.  7 A . In  FIG.  7 B , the horizontal direction of the eye image is an X-axis direction and the vertical direction is a Y-axis direction and the luminance distribution in the X-axis direction is illustrated. In the present embodiment, the X-axis direction (horizontal) coordinates of the cornea-reflected images Pd′ and Pe′ are Xd and Xe, and the X-axis direction coordinates of the pupil edge images a′ and b′ are Xa and Xb. 
     As illustrated in  FIG.  7 B , extremely high levels of luminance are obtained at the coordinates Xd and Xe of the cornea-reflected images Pd′ and Pe′. Except for the coordinates Xd and Xe, extremely low levels of luminance are obtained in an area from the coordinate Xa to the coordinate Xb, which corresponds to an area of the pupil  612  (an area of a pupil image obtained by a light beam from the pupil  612  being formed into an image on the line-of-sight detection sensor  620 ). Then, in an area of an iris  613 , which is outside the pupil  612 , (an area of an iris image, which is outside the pupil image and is obtained by a light beam from the iris  613  being formed into an image), a luminance that is in the middle of the above-mentioned two types of luminance is obtained. Specifically, in an area whose X-coordinate (coordinate in the X-axis direction) is smaller than the coordinate Xa and an area whose X-coordinate is larger than the coordinate Xb, a luminance that is in the middle of the above-described two types of luminance is obtained. 
     It is possible to obtain from a luminance distribution such as illustrated in  FIG.  7 B , the X-coordinates Xd and Xe of the cornea-reflected images Pd′ and Pe′ and the X-coordinates Xa and Xb of the pupil edge images a′ and b′. Specifically, coordinates with extremely high levels of luminance can be obtained as the coordinates of the cornea-reflected images Pd′ and Pe′, and coordinates with extremely low levels of luminance can be obtained as the coordinates of the pupil edge images a′ and b′. Further, when an angle of rotation θx of an optical axis of the eyeball  610  with respect to an optical axis of the light receiving lens  618  is small, the coordinate Xc of a pupil center image c′ (the center of the pupil image) obtained by a light beam from the pupil center c being formed into an image on the line-of-sight detection sensor  30  can be expressed as Xc≈(Xa+Xb)/2. That is, it is possible to calculate the coordinate Xc of the pupil center image c′ from the X-coordinates Xa and Xb of the pupil edge images a′ and b′. In this way, the coordinates of the cornea-reflected images Pd′ and Pe′ and the coordinate of the pupil center image c′ can be estimated. 
     In step S 804 , the CPU  3  calculates an image forming magnification β of the eyeball image. The image forming magnification β is a magnification that is determined by the position of the eyeball  610  with respect to the light receiving lens  618  and can be obtained using a function of an interval (Xd-Xe) between the cornea-reflected images Pd′ and Pe′. 
     In step S 805 , the CPU  3  calculates the angles of rotation of the optical axis of the eyeball  610  with respect to the optical axis of the light receiving lens  618 . The X-coordinate of the middle point of the cornea-reflected image Pd and the cornea-reflected image Pe and the X-coordinate of a center of curvature ◯ of the cornea  611  almost coincide. Therefore, when a standard distance from the center of curvature ◯ of the cornea  611  to the center c of the pupil  612  is ◯c, the angle of rotation θX of the eyeball  610  in the Z-X plane (plane perpendicular to the Y-axis) can be calculated by the following (Equation  1 ). An angle of rotation θy of the eyeball  610  in the Z-Y plane (plane perpendicular to the X-axis) can also be calculated by a method that is the same as the method of calculating the angle of rotation θx. 
       β×◯ c×SINθX≈{ ( Xd+Xe )/2}− Xc    (Equation 1)
 
     In step S 806 , the CPU  3  uses the angles of rotation θx and θy calculated in step S 805  to obtain (estimate) the user&#39;s gaze point (a position at the end of the line of sight, the position at which the user is looking) in the image for visual confirmation displayed on the display device  6 . If coordinates (Hx, Hy) of the gaze point are the coordinates corresponding to the pupil center c, the coordinates (Hx, Hy) of the gaze point can be calculated by the following (Equation 2) and (Equation 3). 
         Hx=m ×( Ax×θx+Bx )   (Equation 2)
 
         Hy=m ×( Ay×θy+By )   (Equation 3)
 
     The parameter m of (Equation 2) and (Equation 3) is a constant determined by the configuration of the viewfinder optical system (such as the light receiving lens  618 ) of the camera  1 , is a conversion coefficient for converting the angles of rotation θx and θy to the coordinates corresponding to the pupil center c in the image for visual confirmation, and is assumed to be determined in advance and stored in the memory unit  4 . The parameters Ax, Bx, Ay, and By are line-of-sight correction parameters that correct for personal differences in the line of sight, are obtained by performing calibration and are assumed to be stored in the memory unit  4  prior to the operation for detecting a line of sight being started. 
     Calibration is the process of obtaining the user&#39;s eye features and is applied for when calculating the coordinates of a gaze point from the angles of rotation. Parameters for correcting sensitivity and a shift in the visual axis are calculated based on an eye image of when the user was made to focus on a plurality of targets. The sensitivity is corrected by the above parameters, Ax and Ay, and the shift in the visual axis is corrected by the above parameters, Bx and By. 
     In step S 807 , the CPU  3  stores the coordinates (Hx, Hy) of the gaze point in the memory unit  4  and terminates the operation for detecting a line of sight. 
       FIG.  9    is a diagram illustrating the distance  32  from the final surface of the ocular optical system to the eye. 
     The distance  32  from the final surface of the ocular optical system  16  to the eye can be obtained using a function of the coordinates of the cornea-reflected images Pd′ and Pe′ or an interval between two points. This function is created based on the results of simulations or actual measurements on a real machine. 
       FIGS.  10 A and  10 B  are diagrams illustrating a method of changing the display area of the display. 
     The display area in the present embodiment refers to an area in which Organic Light Emitting Diodes (OLEDs) are actually illuminated out of the entire displayable area in which OLEDs are arranged. The display area of the display is changed based on the distance  32  from the final surface of the ocular optical system  16  to the user&#39;s eye. 
     As illustrated in  FIG.  10 A , the display area is increased when the user&#39;s eye is close to the ocular optical system.  FIG.  10 A  illustrates a state in which display is performed using the entire displayable area. In contrast, as illustrated in  FIG.  10 B , the display area is decreased when the user&#39;s eye is far from the ocular optical system. In the present embodiment, it is assumed that the shorter the distance between the user&#39;s eye and the ocular optical system, the larger the size of the display area is set to be, and the farther the distance, the narrower the size is set to be. However, it may be switched such that if the distance between the user&#39;s eye and the ocular optical system is equal to or less than a predetermined threshold, the display area will be increased (for example, to the entire displayable area), and if the distance is larger than the predetermined threshold, the display area will be made smaller than when the distance is equal to or less than the predetermined threshold. Further, a plurality of such thresholds may be provided so as to change the display area in a stepwise manner before and after the thresholds. 
     Further, in the present embodiment, when changing the display area of the display, both the OSD (On Screen Display) display and the live view display are changed. It is assumed that the OSD display displays information, such as camera settings at the time of image capturing, which include an aperture and a shutter speed, and the remaining amount of battery. 
       FIGS.  11 A and  11 B  are diagrams illustrating a change of a display of targets used for calibration (CAL) based on the distance  32  from the final surface of the ocular optical system  16  to the eye. 
     In the present embodiment, at the time of calibration for line-of-sight detection, the distance  32  from the final surface of the ocular optical system  16  to the eye is measured while the user is looking at a target at the center, and calibration contents are changed based on that distance. In the calibration for line-of-sight detection, the user needs look at a specified plurality of targets for a fixed period of time. 
     As illustrated in  FIG.  11 A , if the user&#39;s eye is close to the ocular optical system, the arrangement of peripheral targets is changed based on that distance. In the calibration, the larger the image height of the peripheral targets from the optical axis of the ocular optical system  16 , the higher the accuracy will be. If the distance  32  from the final surface of the ocular optical system  16  to the eye is short, since the display area that can be stably viewed by the user is broad, the peripheral targets can be arranged diagonally as illustrated in  FIG.  11 A , which makes it possible to secure the image height of the peripheral targets. 
     As illustrated in  FIG.  11 B , if the user&#39;s eye is far from the ocular optical system  16 , the image height of the peripheral targets is changed so as to be reduced based on that distance. The display area that the user can stably view changes depending on the measured distance  32  from the final surface of the ocular optical system  16  to the eye. For example, if the distance is shorter, the area that can be seen stably will be broader; if the distance is longer, the area that can be seen stably will be smaller. Therefore, placing the peripheral targets in that area makes it possible to ensure that the user looks at the peripheral targets. 
       FIG.  12    is a flowchart for explaining an operation for changing the display area of the display device. This operation is started by the user turning the power of the camera  1  on in step S 1201 . 
     In step S 1202 , the CPU  3  displays, for example, on the display panel  40 , a display asking the user whether to perform calibration. 
     If the user answers “perform calibration”, the CPU  3  advances the process to step S 1203  and performs calibration. At this time, the distance  32  from final surface of the ocular optical system  16  to the eye is calculated. 
     In step S 1204 , the CPU  3  determines the user-optimized display area of the display based on the distance  32  from the final surface of the ocular optical system  16  to the eye calculated in step S 1203 . 
     If the user answers “do not perform calibration” in step S 1202 , the CPU  3  advances the process to step S 1205 . In step S 1205 , the CPU  3  reads out the display area determined when the calibration was previously performed. At this time, the user needs to select user-specific calibration data. 
     In step S 1206 , the CPU  3  determines the display area based on the display area read out in step S 1205 . 
     In step S 1207 , the CPU  3  actually changes the display area of the display device  6  based on the determined display area. 
     As described above, in the present embodiment, in an electronic device, a display area of a display unit is changed based on a distance from the final surface of an ocular optical system to an eye. Specifically, the display area is larger when the distance is shorter, and the display area is smaller when the distance is longer. Thus, without troublesome setting or the like, it is possible to display an image in a display area that is optimal for the user. 
     Further, in the present embodiment, the distance from the final surface of the ocular optical system to the eye is calculated using cornea-reflected images. It is possible to calculate the distance from the final surface of the ocular optical system to the eye based on the coordinates of the cornea-reflected images of an image obtained by a line-of-sight detection sensor. Thus, as compared with a configuration in which a line-of-sight detection means and a distance calculation means are provided separately, since a means for calculating a distance is not specifically needed, it is possible to prevent the device from becoming complex and increasing in size, which makes it possible to have a more inexpensive configuration. 
     Further, in the present embodiment, at the time of calibration for line-of-sight detection, the display of targets used for calibration is changed according to the distance from the final surface of the ocular optical system to the eye. This allows for greater calibration certainty and effectiveness compared to a configuration that does not change the display of the targets used for calibration according to the distance from the final surface of the ocular optical system to the eye. Therefore, it is expected that stability and accuracy of line-of-sight detection will improve. 
     Further, in the present embodiment, when changing the display area of the display, both the OSD display and the live view display are changed. Thus, visibility can be ensured not only in the live view display but also in the OSD display as compared with a configuration in which only the live view display is changed and the OSD display is kept constant. Therefore, it is easier for the user to ascertain information, such as camera settings and remaining amount of battery at the time of image capturing. 
     Further, in the present embodiment, the distance from the final surface of the ocular optical system to the eye is calculated at the time of calibration for line-of-sight detection. Thus, once a user-specific distance has been obtained and recorded, from the next and subsequent times, it is possible to easily read out the display area optimized for the user only by selecting the calibration data. Therefore, the user can quickly transition to image capturing. 
     Second Embodiment 
     Hereinafter, a second embodiment will be described with reference to  FIGS.  13 A and  13 B . 
     In the first embodiment, when changing the display area of the display, both the OSD display and the live view display are changed. In contrast, in the second embodiment, when changing the display area, only the live view display is changed and the OSD display is maintained at a constant. 
       FIG.  13 A  illustrates a case where the eye is close to the ocular optical system.  FIG.  13 B  illustrates a case where the eye is far from the ocular optical system. 
     In this embodiment, the OSD display is constant regardless of the distance of the eye from the camera and only the display area of the live view display is changed. Thus, compared with the configuration in which both the OSD display and the live view display are changed, it is possible to prevent the fonts of characters indicating information, such as camera settings and the remaining amount of battery, from becoming small and difficult to see, while ensuring visibility of the live view display. 
     Third Embodiment 
     Hereinafter, a third embodiment will be described with reference to  FIG.  14   . 
     In the first embodiment, the distance  32  from the final surface of the ocular optical system  16  to the eye is calculated at the time of calibration for line-of-sight detection. In contrast, in the third embodiment, the distance is calculated after the approach of the eye is detected. 
     In step S 1401  of  FIG.  14   , the CPU  3  detects the approach of the eye using the eye-approach detection unit  208 . 
     In step S 1402 , the CPU  3  determines whether or not the distance from the final surface of the ocular optical system  16  to the eye has stabilized. Here, the CPU  3  determines whether or not the amount of reflected light received by the eye-approach detection sensor  50  is stable exceeding an eye-approach determination threshold. If the amount of reflected light is stable exceeding the eye-approach determination threshold, it is determined that the distance has stabilized, and the CPU  3  advances the process to step S 1403 . On the other hand, if the amount of reflected light has not exceeded the eye-approach determination threshold or is not stable, the CPU  3  determines that the distance is not stable and repeats the process of step S 1402  until the distance stabilizes. 
     In step S 1403 , the CPU  3  calculates the distance from the final surface of the ocular optical system  16  to the eye. 
     In step S 1404 , the CPU  3  determines the display area of the display based on the distance calculated in step S 1403 . 
     In step S 1404 , the CPU  3  turns the display on based on the display area determined in step S 1405 . 
     In the present embodiment, the distance from the final surface of the ocular optical system to the eye is calculated after it is detected that the user&#39;s eye has approached the camera. Thus, since the distance is calculated for each instance of the approach of the eye and the display area is changed, display can be performed with the display area optimized for the way the user is looking into the viewfinder at each instance. 
     Fourth Embodiment 
     A fourth embodiment will be described below with reference to  FIG.  15   . 
     In the first embodiment, the distance  32  from the final surface of the ocular optical system  16  to the eye is calculated at the time of calibration for line-of-sight detection. In contrast, in the fourth embodiment, the distance is calculated when a press of a button for changing the display area of the display is detected. In the present embodiment, it is assumed that the front surface of the camera body  1 B is provided with the button for changing the display area of the display. 
     In step S 1501  of  FIG.  15   , the CPU  3  detects a press of the button for changing the display area of the display. 
     In step S 1502 , the CPU  3  calculates the distance  32  from the final surface of the ocular optical system  16  to the eye. 
     In step S 1503 , the CPU  3  determines the display area of the display based on the distance calculated in step S 1502 . 
     In step S 1504 , the CPU  3  changes the display area of the display based on the display area determined in step S 1503 . 
     In the present embodiment, when a press of the button for changing the display area of the display is detected, the distance from the final surface of the ocular optical system to the eye is calculated. Thus, it is possible to calculate the distance again and perform display with an appropriate display area when the user wishes to change the display area. 
     Other Embodiments 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)TM), a flash memory device, a memory card, and the like. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2021-181436, filed Nov. 5, 2021, which is hereby incorporated by reference herein in its entirety.