Patent Publication Number: US-9905147-B2

Title: Display device

Description:
This is a continuation application of U.S. application Ser. No. 13/903,872, entitled “Display Device” which was filed on May 28, 2013 and is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Embodiments relate to a display device. Some embodiments relate to a portable device comprising a display device. Some embodiments relate to a method for operating a display device. Some embodiments relate to a method for determining a dioptre value of a long-sighted person. 
     BACKGROUND 
     Using smartphones for hyperopic or long-sighted eye persons is a problem. Due to insufficient accommodation of the eye it is not possible to see in reading distance in a sharp and reliable way. 
     Currently the only solution to compensate hyperopic-eyes is putting on reading glasses. One disadvantage is quite often reading glasses are not directly available or are not useful in the actual situation. On the other hand reading glasses may not be liked to be used due to aesthetic reasons. 
     SUMMARY OF THE INVENTION 
     A display device is provided. The display device comprises a display comprising a plurality of pixels arranged in a display plane. The display device is configured to determine a virtual plane at which a long-sighted user of the display device who is looking at the display sees sharp. Further, the display device is configured to determine a first contiguous group of pixels of the display which are located within a first optical path from a first virtual pixel of the virtual plane to an eye of the long-sighted user, and to determine a second contiguous group of pixels of the display which are located within a second optical path from a second virtual pixel of the virtual plane to the eye of the long-sighted user. Further, the display device is configured to adjust an intensity and a directivity (or emission angle) of at least a portion of the first group of pixels corresponding to the first virtual pixel in a first direction defined by the first optical path, and to adjust an intensity and directivity (or emission angle) of at least a portion of the second group of pixels corresponding to the second virtual pixel in a second direction, different from the first direction, defined by the second optical path. 
     A portable device comprising a display device is provided. The display device comprises a display comprising a plurality of pixels arranged in a display plane. The display device is configured to determine a virtual plane at which a long-sighted user of the display device who is looking at the display sees sharp. Further, the display device is configured to determine a first contiguous group of pixels of the display which are located within a first optical path from a first virtual pixel of the virtual plane to an eye of the long-sighted user, and to determine a second contiguous group of pixels of the display which are located within a second optical path from a second virtual pixel of the virtual plane to the eye of the long-sighted user. Further, the display device is configured to adjust an intensity and a directivity (or emission angle) of at least a portion of the first group of pixels corresponding to the first virtual pixel in a first direction defined by the first optical path, and to adjust an intensity and directivity (or emission angle) of at least a portion of the second group of pixels corresponding to the second virtual pixel in a second direction, different from the first direction, defined by the second optical path. 
     A method for operating a display device is provided. The display device comprises a display comprising a plurality of pixels arranged in a display plane. The method comprises determining a virtual plane at which a long-sighted user of the display device who is looking at the display sees sharp. Further, the method comprises determining a first contiguous group of pixels of the display which are located within a first optical path from a first virtual pixel of the virtual plane to an eye of the long-sighted user, and determining a second contiguous group of pixels of the display which are located within a second optical path from a second virtual pixel of the virtual plane to the eye of the long-sighted user. Further, the method comprises adjusting an intensity and a directivity (or emission angle) of at least a portion of the first group of pixels corresponding to the first virtual pixel in a first direction defined by the first optical path, and adjusting an intensity and a directivity (or emission angle) of at least a portion of the second group of pixels corresponding to the second virtual pixel in a second direction, different from the first direction, defined by the second optical path. 
     A method for determining a dioptre value of a long-sighted person using a display device is provided. The display device comprises a display comprising a plurality of pixels arranged in a display plane. The method comprises determining a virtual plane at which the long-sighted person who is looking at the display is expected to see sharp. Further, the method comprises determining a first contiguous group of pixels of the display which are located within a first optical path from a first virtual pixel of the virtual plane to an eye of the long-sighted person, and determining a second contiguous group of pixels of the display which are located within a second optical path from a second virtual pixel of the virtual plane to the eye of the long-sighted person. Further, the method comprises adjusting an intensity and a directivity (or emission angle) of at least a portion of the first group of pixels corresponding to the first virtual pixel in a first direction defined by the first optical path, and adjusting an intensity and a directivity (or emission angle) of at least a portion of the second group of pixels corresponding to the second virtual pixel in a second direction, different from the first direction, defined by the second optical path. Further, the method comprises adjusting a position of the virtual plane until the long-sighted person sees sharp the first pixel and the second pixel. Further, the method comprises providing the dioptre value based on the adjusted position of the virtual plane. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention are described herein making reference to the appended drawings. 
         FIG. 1  shows an illustrative sight-view of a display device; 
         FIG. 2  shows an illustrative view of an eye of a long-sighted person and the plane at which the eye of the long-sighted person sees sharp; 
         FIG. 3  shows an illustrative view of the eye of the long-sighted user and the plane at which the eye of the longsighted user sees sharp; 
         FIG. 4  shows an illustrative view of the eye of the long-sighted user, the plane at which the eye of the long-sighted user sees sharp and the display plane of the display of the display device; 
         FIG. 5  shows an illustrative view of the eye of the long-sighted user, the plane at which the eye of the long-sighted user sees sharp and the display plane of the display of the display device; 
         FIG. 6  shows an illustrative view of the eye of the long-sighted user, the plane at which the eye of the long-sighted user sees sharp and the display plane of the display of the display device; 
         FIG. 7  shows an illustrative view of the eye of the long-sighted user, the plane at which the eye of the long-sighted user sees sharp and the display plane of the display of the display device; 
         FIG. 8  shows an illustrative view of the eye of the long-sighted user, the plane at which the eye of the long-sighted user sees sharp and the display plane of the display of the display device; 
         FIG. 9  shows an illustrative view of a portable device; 
         FIG. 10A  shows an exemplary image of a conventional smartphone from the view of a normal-sighted eye; 
         FIG. 10B  shows an exemplary image of the conventional smartphone from the view of a long-sighted eye; 
         FIG. 10C  shows an exemplary image of a smartphone implementation of the portable device shown in  FIG. 9 ; 
         FIG. 11  shows a flowchart of a method for operating a display device; and 
         FIG. 12  shows a flowchart of a method for determining a dioptre value of a long-sighted person using a display device. 
     
    
    
     Equal or equivalent elements or elements with equal or equivalent functionality are denoted in the following description by equal or equivalent reference numerals. 
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     In the following description, a plurality of details are set forth to provide a more thorough explanation of embodiments of the present invention. However, it will be apparent to those skilled in the art that embodiments of the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form rather than in detail in order to avoid obscuring embodiments of the present invention. In addition, features of the different embodiments described hereinafter may be combined with each other, unless specifically noted otherwise. 
       FIG. 1  shows an illustrative sight-view of a display device  100 . The display device  100  comprises a display  102  having a plurality of pixels  104  arranged in a display plane  106 . 
     The display device  100  is configured to determine a virtual plane  108  at which a long-sighted user of the display device  100  who is looking at the display  102  sees sharp, i.e., the image appears sharp to the user. The display device  100  is configured to determine a first contiguous group  110  of pixels  104  of the display  102  which are located within a first optical path  112  from a first virtual pixel  114  of the virtual plane  108  to an eye  116  of the long-sighted user, and to determine a second contiguous group  118  of pixels  104  of the display  102  which are located within a second optical path  120  from a second virtual pixel  122  of the virtual plane  108  to the eye  116  of the long-sighted user. 
     Further, the display device  100  is configured to adjust an intensity and a directivity (or emission angle) of at least a portion of the first group  110  of pixels  104  corresponding to the first virtual pixel  114  in a first direction defined by the first optical path  112 , and to adjust an intensity and a directivity (or emission angle) of at least a portion of the second group  118  of pixels  104  corresponding to the second virtual pixel  122  in a second direction, different from the first direction, defined by the second optical path  120 . 
     Thereby, the display device  100  may compensate the hyperopic (long-sighted) eye of the user of the display device  100  by reproducing the first virtual pixel  114 , which is located at the plane  108  at which the long-sighted user sees sharp, by adjusting the intensity and the directivity of at least a portion of the first contiguous group  110  of pixels  104  corresponding to the first virtual pixel  114 , and by reproducing the second virtual pixel  122 , which is located at the plane  108  at which the long-sighted user sees sharp, by adjusting the intensity and the directivity of at least a portion of the second contiguous group  118  of pixels  104  corresponding to the second virtual pixel  122 . In other words, a human hyperopic (long-sighted) eye can be compensated by utilizing angular dependent light emission at the display  102 . 
     As shown in  FIG. 1 , the first optical path  112  may comprise the form (or shape) of a conus which extends from the first virtual pixel  114  to a lens  117  of the eye  116  of the long-sighted user of the display device  100 . Just as well the second optical path  120  may comprise the form (or shape) of a conus which extends from the second virtual pixel  120  to the lens  117  of the eye  116  of the long-sighted user of the display device  100 . 
     Thereby, the first optical path  112  may intercept the display plane  106  in a first area (or region) of the display plane  106 , wherein the second optical path  120  may intercept the display plane  106  in a second area (or region) of the display plane  106 . The first contiguous group  110  of pixels may be the pixels  104  of the display  102  which are located within the first area of the display plane  106 , wherein the second contiguous group  118  of pixels  104  may be the pixels  104  of the display  102  which are located within the second area of the display plane. 
     Note that the first area of the display plane  106  at which the first optical path  112  intercepts the display plane  106 , and the second area of the display plane  106  at which the second optical path  120  intercepts the display plane  106  may overlap in an overlap area. 
     Thus, pixels  104  of the display  102  which are located within this overlap area may be used to reproduce both, the first virtual pixel  114  and the second virtual pixel  122 . 
     Therefore, the display device  100  may be configured to select a first number of the pixels which are located within this overlap area to reproduce the first virtual pixel (i.e., to adjust the intensity and the directivity of the first number of the pixels in the first direction to reproduce the first virtual pixel, or in other words, to adjust the intensity and the emission angle of the first number of the pixels in order to reproduce the first virtual pixel), and to select a second number of the pixels, different from the first number of the pixels, which are located within this overlap area to reproduce the second virtual pixel  122  (i.e., to adjust the intensity and directivity of the second number of the pixels in the second direction to reproduce the second virtual pixel  122 , or in other words, to adjust the intensity and the emission angle of the second number of the pixels in order to reproduce the second virtual pixel  122 ). 
     In other words, the display device  100  may be configured to adjust the intensity and the directivity of only a portion of the first contiguous group  110  of pixels  104  corresponding to the first virtual pixel  114  in order to reproduce the first virtual pixel  114  via the first contiguous group  110  of pixels  104 , and to adjust the intensity and directivity of only a portion of the second contiguous group of pixels  118 , different from the portion of the first contiguous group  110  of pixels  104 , corresponding to the second virtual pixel  122  in order to reproduce the second virtual pixel  122  via the second contiguous group  118  of pixels  104 . 
     Moreover, the device  100  can be configured to adjust the intensity and the directivity of at least a portion of the first contiguous group  110  of pixels  104  during a first time period, and to adjust the intensity and the directivity of at least the portion of the second contiguous group  110  of pixels  104  during a second time period, different from the first time period. 
     For example, the display device  100  can be configured to reproduce the first virtual pixel  114  in (or during) the first time period by adjusting, in (or during) the first time period, the intensity and the directivity of at least the portion of the first contiguous group  110  of pixels  104  corresponding to the first virtual pixel  114  in order to reproduce the first virtual pixel  114 , and to reproduce the second virtual pixel  122  in (or during) the second time period, different from the first time period, by adjusting, in (or during) the second time period, the intensity and the directivity of at least the portion of the second contiguous group  118  of pixels  104  corresponding to the second virtual pixel  122  in order to reproduce the second virtual pixel  122 . 
     The display device  100  may comprise a sensor  124  for detecting a position of the eye  116  of the long-sighted user of the display device  100 . Thereby, the display device  100  can be configured to determine the first optical path  112  and the second optical path  120  based on the detected position of the eye  116  of the long-sighted user. 
     Naturally, the sensor  124  of the display device  100  may also be configured to detect a position of a first eye and a position of a second eye of the of the long-sighted user of the display device  100 , and to detect first optical paths from the first virtual pixel of the virtual plane to the first and second eyes of the long-sighted user, and to detect second optical paths from the second virtual pixel of the virtual plane to the first and second eyes of the long-sighted user. 
     For example, the sensor  124  may be a camera of the display device  100  or an external camera that is connected to the display device  100 . Further, the position of the eye  116  of the long-sighted user may be a relative position of the eye  116  of the long-sighted user with respect to the display plane  106  of the display  102  of the display device  100  or the virtual plane  108 . Further, the position of the eye  116  of the long-sighted user may be described by a vector between the eye  116  of the long-sighted user and a reference point of the display device  100 , such as a center or edge of the display  102 , or of the sensor  124 . 
     Moreover, the display device  100  may be configured to determine the virtual plane  108  such that the display plane  106  and the virtual plane  108  are parallel to each other. 
     In the following it is described in detail how a human hyperopic eye can be compensated by utilizing an angular dependent light emission at the display  102  as it is implemented by the above described display device  100 . 
       FIG. 2  shows an illustrative view of the eye  116  of the long-sighted user and the plane  108  at which the eye  116  of the longsighted user sees sharp. Further, in  FIG. 2  a first spot  114  having a first intensity and/or color is shown. The first spot  114  is located at a first position at the plane  108  at which the eye  116  of the longsighted user sees sharp. In other words, in  FIG. 2  focusing on a first spot  114  is shown. 
     For example, the first spot  114  can be a light spot. First rays (e.g., light rays) which come from the first spot  114  (e.g., light spot) travel through the eyeball lens  117  and reach the eyeball backplane. Thereby, it is assumed that the plane  108  with the first spot  114  is far enough in its distance to be seen sharply, even for a long-sighted (hyperopic) person. 
       FIG. 3  shows an illustrative view of the eye  116  of the long-sighted user, the plane  108  at which the eye of the long-sighted user sees sharp. If a plane  106  is introduced more closely, e.g., the display plane  106  of the display  102  of the display device  100  (e.g., a smartphone), the eye  116  of the long-sighted user is not able to accommodate this, and any picture is not sharp anymore. 
       FIG. 4  shows an illustrative view of the eye  116  of the long-sighted user, the plane  108  at which the eye of the long-sighted user sees sharp and the display plane  106  of the display  102  of the display device  100 . To get a first spot  114 ′ (e.g., a light spot) on the eyeball backplane, the display  102  of the display device  100  may emit first information (e.g., light information or white information) from a first larger region  110 , as indicated in  FIG. 4 . 
       FIG. 5  shows an illustrative view of the eye  116  of the long-sighted user, the plane  108  at which the eye of the long-sighted user sees sharp and the display plane  106  of the display  102  of the display device  100 . In contrast to  FIGS. 3 and 4 , in  FIG. 5  a second spot  122  having a second intensity and/or color, different from the first intensity and/or color of the first spot  114 , is shown. The second spot  122  is located at a second position, different from the first position, at the plane  108  at which the eye  116  of the longsighted user sees sharp. In other words,  FIG. 5  shows focusing on a second spot  122 . 
     For example, the second spot  122  can be a dark spot or another colored spot. Second rays (e.g., dark or colored rays) which come from the second spot  122  (e.g., dark or colored spot) travel through the eyeball lens  117 , wherein a different location  122 ′ of the eyeball backplane will be reached by the second rays (e.g., dark or colored rays). 
       FIG. 6  shows an illustrative view of the eye  116  of the long-sighted user, the plane  108  at which the eye of the long-sighted user sees sharp and the display plane  106  of the display  102  of the display device  100 . Translating the second spot  122  to the display plane  106  means that the display  102  should give second information (e.g., dark or colored information) from a larger region  118  as indicated in  FIG. 6 . 
       FIG. 7  shows an illustrative view of the eye  116  of the long-sighted user, the plane  108  at which the eye of the long-sighted user sees sharp and the display plane  106  of the display  102  of the display device  100 . In  FIG. 7 , the first region  110  and the second region  118  overlap in an overlap region (or area). Pixels  104  of the display  102  which are located within this overlap region (or area) may be used to reproduce both, the first spot  114  and the second spot  122 . 
     Normally, this is a contradiction for the display  102 . From the same location on the display  102 , the display should give the first information (e.g., light information) and the second information (e.g., dark or colored information). Actually, this contradiction is only virtual, because this contradiction can be solved by the method of angular dependent light emission of the display. 
     Subsequently, the angle of emission at the display  102  is described for one spot of the display  102 . For that purpose in  FIG. 7  a spot  126  is indicated. The spot  126  is located within the overlap area (or region) in which the first region  110  and the second region  118  overlap. Thereby, the spot  126  may cover at least one pixel  104 . 
     Further,  FIG. 7  shows a first information direction  127  (e.g., light ray direction) which lands on the eyes backplane. As shown in  FIG. 7 , from the same spot  126  also the second information (e.g., dark or colored information) may come. Landing of the second information (e.g., dark or colored information) is on a different place at the eyes backplane. But this correlates to a different emission angle on display  102  of the display device  100 . So the solution is an angular dependent light emission from the display  102  of the display device  100 . 
       FIG. 8  shows an illustrative view of the eye  116  of the long-sighted user, the plane  108  at which the eye of the long-sighted user sees sharp and the display plane  106  of the display  102  of the display device  100 . Further in  FIG. 8 , the first direction  128 , in which the spot  126  at the display  102  is supposed to emit the first information (e.g., light information), and the second direction  130 , in which the spot  126  at the display  102  is supposed to emit the second information (e.g., dark or colored information), is shown. Moreover, an angle between the first direction  128  and the second direction  130  is indicated. 
     For example, a spatial-angular resolution of the display device emission in the range of the eye resolution on the display may be required, i.e., 0.05 mm at 100 cm (50-70 μm is hair thickness). This results at about 10 second of arc for the display  102  of the display device  100 . 
     Note that  FIG. 8  shows an example for two spots for illustration purposes. Naturally, the display device  100  can also be configured to display up n spots, wherein n is a natural number greater than or equal to two, i.e., n≧2, such as 10, 20, 30, 40, 50, 100, 200 or even more spots. For this purpose, the display device  100  can be configured to determine an i-th (1≦i≦n) contiguous group of pixels of the display which are located within an i-th optical path from an i-th virtual pixel of the virtual plane to an eye of the long-sighted user, and to adjust an intensity and a directivity of at least a portion of the i-th group of pixels corresponding to the i-th virtual pixel in an i-th direction defined by the i-th optical path. 
     In other words, the example shown in  FIG. 8  can be extended up to n spots on a full display, so that the full display can provide (of display) a full image by angular dependent light emission based on each contiguous group of pixels (of n contiguous groups of pixels). 
     As already mentioned, the display device  100  shown in  FIG. 1  utilizes the above described angular dependent light emission at the display  102  in order to compensate for human hyperopic (long-sighted) eye. 
     For that purpose, the display device  100  is configured to determine the virtual plane  108  at which the long-sighted user of the display device  100  who is looking at the display  102  sees sharp. The determined virtual plane  108  may correspond (or be equal) to the plane  108  at which the eye  116  of the long-sighted user sees sharp which is shown in  FIGS. 2 to 8 . 
     Further, the display device  100  is configured to determine the first contiguous group  110  of pixels  104  of the display  102  which are located within the first optical path  112  from the first virtual pixel  114  of the virtual plane  108  to the eye  116  of the long-sighted user. The first virtual pixel  114  may be an information to be displayed or reproduced via the display  102 , such as the first spot  114  shown in  FIGS. 2 to 8 . Thereby, the first contiguous group  110  of the pixels can be the pixels of the display  102  which are located within the first area or region  110  shown in  FIG. 4 . 
     Similarly, the display device  100  is configured to determine the second contiguous group  118  of pixels  104  of the display  102  which are located within the second optical path  120  from the second virtual pixel  122  of the virtual plane  108  to the eye  116  of the long-sighted user. The second virtual pixel  122  may be information to be displayed or reproduced via the display  102 , such as the second spot  114  shown in  FIGS. 5 to 8 . Thereby, the second contiguous group  118  of the pixels can be the pixels of the display  102  which are located within the second area or region  110  shown in  FIG. 6 . 
     Moreover, the display device  100  is configured to adjust an intensity and a directivity of at least a portion of the first contiguous group  110  of pixels  104  corresponding to the first virtual pixel  114  in a first direction defined by the first optical path  112  corresponding to the first virtual pixel  114  in the first direction defined by the first optical path  112 . Thereby, the display  102  may reproduce the first information mentioned above by adjusting the intensity and directivity of at least a portion of the first contiguous group  110  of pixels  104 . Moreover, the first direction may be the first direction  128  shown in  FIG. 8 . 
     Just as well, the display device  100  is configured to adjust an intensity and a directivity of at least a portion of the second contiguous group  118  of pixels  104  corresponding to the second virtual pixel  122  in a second direction defined by the second optical path  120  corresponding to the second virtual pixel  122  in the second direction defined by the second optical path  120 . Thereby, the display  102  may reproduce the second information mentioned above by adjusting the intensity and directivity of at least a portion of the second contiguous group  118  of pixels  104 . Moreover, the second direction may be the second direction  130  shown in  FIG. 8 . 
     The display device  100  can be is a monitor, a television, a smartphone, a tablet PC, a portable PC or a PC. 
     For example, the display device can be used for smartphones, tablet PCs and even standard PCs. Medical applications are also possible. For example, an eye specialist can determine the visual acuity by software defocusing on a tablet PC itself. So there is no need for a far distant wall anymore. 
     Further, the display device  100  can comprise a focus control element  125  (e.g., a button or slider) for adjusting a focus of the display device  100  (see  FIG. 1 ). Thereby, the display device  100  can be configured to adjust a position of the virtual plane  108  in response to an adjustment of the focus via the focus control element  125 . 
     Moreover, the display device  100  can comprise a dioptre control element  125  (e.g., a button or slider) for setting a dioptre value. Thereby, the display device  100  can be configured to determine the virtual plane  108  based on the set dioptre value. 
     In other words, additional to the angular dependent light emission a slider  125  on the display can be implemented. Such slider can allow continuously adapting different dioptrens, simply by sliding up/down. So the user can easily adjust to its individual visual acuity. 
       FIG. 9  shows an illustrative view of a portable device  180 . The portable device  180  comprises the above described display device  100  comprising the display  102  having the plurality of pixels  104 . The portable device  180  can be a smartphone, a tablet PC or notebook. As shown in  FIG. 9 , the plurality of pixels  104  can be arranged in a two-dimensional array. 
     Further, the portable device  180  can comprise the above described sensor  124 , the above described dioptre control element  125  and/or the above described focus control element  125 . 
       FIG. 10 a    shows an exemplary image of a conventional smartphone  170  from the view of a normal-sighted eye. 
       FIG. 10 b    shows an exemplary image of the conventional smartphone  170  from the view of a long-sighted eye. In other words,  FIG. 10 b    shows a standard not-sharp situation of hyperopic-eye. 
       FIG. 10 c    shows an exemplary image of a smartphone implementation of the portable device  180  shown in  FIG. 9 . The advantage is evident. Despite the fact that the background still is not sharp, everything on the display  102  of the portable device  180  is clearly readable. Everything on the display  102  can be seen with an increased (or even maximum) resolution. The display device  100  of the portable device  180  solves this by utilizing angular dependent light emission at the display  102 . 
       FIG. 11  shows a flowchart of a method  200  for operating a display device. The display device comprises a display comprising a plurality of pixels arranged in a display plane. The method comprises determining  202  a virtual plane at which a long-sighted user of the display device who is looking at the display sees sharp. Further, the method  200  comprises determining  204  a first contiguous group of pixels of the display which are located within a first optical path from a first virtual pixel of the virtual plane to an eye of the long-sighted user, and determining  206  a second contiguous group of pixels of the display which are located within a second optical path from a second virtual pixel of the virtual plane to the eye of the long-sighted user. Further, the method  200  comprises adjusting  208  an intensity and a directivity of at least a portion of the first group of pixels corresponding to the first virtual pixel in a first direction defined by the first optical path, and adjusting  210  an intensity and a directivity of at least a portion of the second group of pixels corresponding to the second virtual pixel in a second direction, different from the first direction, defined by the second optical path. 
       FIG. 12  shows a flowchart of a method  220  for determining a dioptre value of a long-sighted person using a display device. The display device comprises a display comprising a plurality of pixels arranged in a display plane. The method  220  comprises determining  222  a virtual plane at which the long-sighted person who is looking at the display is expected to see sharp. Further, the method  220  comprises determining  224  a first contiguous group of pixels of the display which are located within a first optical path from a first virtual pixel of the virtual plane to an eye of the long-sighted person, and determining  226  a second contiguous group of pixels of the display which are located within a second optical path from a second virtual pixel of the virtual plane to the eye of the long-sighted person. Further, the method  220  comprises adjusting  228  an intensity and a directivity of at least a portion of the first group of pixels corresponding to the first virtual pixel in a first direction defined by the first optical path, and adjusting  230  an intensity and a directivity of at least a portion of the second group of pixels corresponding to the second virtual pixel in a second direction, different from the first direction, defined by the second optical path. Further, the method  220  comprises adjusting  232  a position of the virtual plane until the long-sighted person sees sharp the first pixel and the second pixel. Further, the method  220  comprises providing  234  the dioptre value based on the adjusted position of the virtual plane. 
     Although some aspects have been described in the context of an apparatus, it is clear that these aspects also represent a description of the corresponding method, where a block or device corresponds to a method step or a feature of a method step. Analogously, aspects described in the context of a method step also represent a description of a corresponding block or item or feature of a corresponding apparatus. Some or all of the method steps may be executed by (or using) a hardware apparatus, like a microprocessor, a programmable computer or an electronic circuit. Some one or more of the most important method steps may be executed by such an apparatus. 
     The implementation may be in hardware or in software or may be performed using a digital storage medium, for example, a floppy disk, a DVD, a Blu-Ray, a CD, a ROM, a PROM, an EPROM, an EEPROM or a FLASH memory, having electronically readable control signals stored thereon, which cooperate (or are capable of cooperating) with a programmable computer system such that the respective method is performed. A data carrier may be provided which has electronically readable control signals, which are capable of cooperating with a programmable computer system, such that the method described herein is performed. 
     The implementation may also be in the form of a computer program product with a program code, the program code being operative for performing the method when the computer program product runs on a computer. The program code may be stored on a machine readable carrier. 
     The above described is merely illustrative, and it is understood that modifications and variations of the arrangements and the details described herein will be apparent to others skilled in the art. It is the intent, therefore, to be limited only by the scope of the impending claims and not by the specific details presented by way of description and explanation above.