Patent Publication Number: US-9842522-B2

Title: Stretchable display apparatus with compensating screen shape

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Korean Patent Application No. 10-2015-0006782, filed on Jan. 14, 2015, in the Korean Intellectual Property Office, and entitled: “Head Mounted Display Apparatus,” is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     Embodiments relate to a head mounted display device. More particularly, the embodiments relate to a head mounted display for correcting a distortion aberration in an optical unit. 
     2. Description of the Related Art 
     In general, a head mounted display (HMD) refers to a small-sized image display that is mounted on a head or around eyes to provide virtual reality or an immersive experience. Recently, with an increasing interest in wearable devices, HMDs with a micro display on glasses or the front of a helmet have been developed. 
     Implementing the HMD may include a method of enlarging and projecting a micro display to an optical unit so that it is projected directly to eyes, a method of enlarging and projecting a micro display to an optical unit so that it is projected to eyes through a connective optical unit, and a method of enlarging and exhibiting a mobile display through an optical unit. 
       FIG. 1  illustrates a distortion aberration due to an optical unit of a head mounted display of the related art. Referring to  FIG. 1 , the head mounted display of the related art uses a flat rectangular display panel. An optical unit composed of at least one lens is used to form an image displayed on a display panel. However, in image formation using an optical unit, there is a problem in that the formed image is distorted by the lens aberration. 
     That is, the iris of an eye functions as an aperture stop and is positioned behind the optical unit, an image A displayed on the flat rectangular display panel, as illustrated in  FIG. 1 , is illustrated as an image B with the outline distorted due to a distortion aberration of a pin cushion shape by the optical unit. 
     Due to this problem, a user wearing the HMDs of the related art feels dizzy or the definition is low, so there is a need to correct a distortion aberration. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     An exemplary embodiment provides a display that includes a stretchable display panel, an optical unit to transmit an image displayed on the display panel for image formation, a mechanical unit to change a physical shape of the display panel in order to compensate for a distortion aberration in the image output by the optical unit, and a control unit to drive the display panel in response to an image source signal. 
     The display panel may be deformed by the mechanical unit to display a correction image distorted in a barrel shape. 
     The mechanical unit may adjust sides of the display panel to compensate for the distortion aberration. 
     The mechanical unit may include a plurality of translation modules coupled to sides of the display panel to physically change the shape of the display panel to compensate for the distortion aberration, a driving module that includes an actuator and a motor coupled to the translation modules, the motor to physically move the translation modules to predetermined distances, a driving control module to adjust movement distances of the translation modules, and a distortion analyzing module to calculate individual movement distances of the translation modules in accordance with a size of the display panel and the distortion aberration, and transmits the movement distances to the driving control module. 
     The mechanical unit may pull the display panel differently at different positions of the sides to compensate for the distortion aberration. 
     The display may include a bezel unit to couple the translation module, the bezel unit covering a side of the display panel. 
     The bezel unit may be attached to the side of the display panel with an adhesive or a fastener. 
     The fastener may pass through the side of the display panel. 
     The display may include a controller to be operated by a user to adjust a degree of deformation of the display panel. 
     The image source may include at least one of an image taken by a camera, an image for exhibiting a user interface, an image kept in a memory, a 3D image, and a virtual image produced by an installed program. 
     The control unit may transmit image signals for a first image and a second image, which have different viewpoints, to display panels for a left eye and a right eye, respectively. 
     The mechanical unit may adjust corners of the display panel to compensate for the distortion aberration. 
     The mechanical unit may include a plurality of translation modules coupled to corners of the display panel to physically change the shape of the display panel to compensate for the distortion aberration, a driving module that includes an actuator and a motor coupled to the translation modules, the actuator to physically move the translation modules to predetermined distances by operating the motor, a driving control module that adjusts movement distances of the translation modules, and a distortion analyzing module that calculates individual movement distances of the translation modules which depend on a size of the display panel and the distortion aberration, and transmits the movement distances to the driving control module. 
     The mechanical unit may move corners of the display panel towards the optical unit. 
     The display may be a head mounted display. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features will become apparent to those of skill in the art by describing in detail exemplary embodiments with reference to the attached drawings in which: 
         FIG. 1  illustrates a distortion aberration due to an optical unit of a head mounted display of the related art. 
         FIG. 2  illustrates a head mounted display according to an exemplary embodiment relative to a viewer. 
         FIG. 3  illustrates a modification method according to a characteristic of extension of a display panel according to an exemplary embodiment. 
         FIG. 4  illustrates a conceptual diagram of correcting a distortion aberration due to an optical unit according to an exemplary embodiment. 
         FIG. 5  illustrates a block diagram of a mechanical unit according to an exemplary embodiment. 
         FIG. 6  illustrates a cross-sectional view taken along line A-A of a combination structure of a translation module according to an exemplary embodiment. 
         FIGS. 7 to 9  illustrate cross-sectional views taken along line A-A which illustrates a combination structure of another type of translation module according to an exemplary embodiment. 
         FIG. 10  illustrates an exemplary use of the head mounted display according to an exemplary embodiment. 
         FIG. 11  illustrates a curved flexible display panel according to another exemplary embodiment. 
         FIG. 12  illustrates an image formation surface corrected by a curved display panel according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, only certain exemplary embodiments have been illustrated and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. 
     Throughout the specification, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. In addition, the terms “-er”, “-or” and “module” described in the specification mean units for processing at least one function and operation and can be implemented by hardware components or software components and combinations thereof. 
     Hereinafter, a head mounted display according to an exemplary embodiment will be described in detail with reference to the drawings. 
       FIG. 2  illustrates a head mounted display according to an exemplary embodiment relative to a viewer. Referring to  FIG. 2 , a head mounted display  100  according to an exemplary embodiment includes an optical unit  110 , a display panel  120 , a mechanical unit  130 , and a control unit  140 . The mechanical unit may be controlled by a user to a controller  135  to further optimize the display. Though not illustrated in the drawings, the display may further include a body for receiving or fixing and supporting the components. 
     The optical unit  110  may include a lens that transmits an image displayed on the display panel  120  for image formation on the user&#39;s eyes. In the following description, although the optical unit  110  is assumed to be one lens, embodiments are not limited thereto, e.g., may include a plurality of lenses as well as additional optical components that do not have optical power, e.g., such as a prism or a filter. 
     The display panel  120  is positioned close to the optical unit  110  at a distance smaller than the focal distance of the optical lens  110  (S1&lt;f), and an enlarged erected virtual image is formed on an eye by a lens formula 
     
       
         
           
             
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     The display panel  120  is a stretchable display panel that displays a distorted image due to intensive physical deformation in order to compensate a distortion aberration generated by the optical unit. The display panel  120  may be deformed due to being on a substrate material (for example, polyvinylidene fluoride (PVDF)) that can extend, restore, compress, etc. The mechanical unit  130  adjusts the degree of distortion of the image by changing the physical shape of the display panel  120 . 
       FIG. 3  illustrates a diagram a modification method of a display panel according to an exemplary embodiment. While the display unit in  FIG. 3  is illustrated as being rectangular, the display unit may have any shape. 
     Referring to  FIG. 3 , a plurality of translation modules  131 , e.g., extension modules, is coupled to the sides of the display panel  120 , e.g., around an entire periphery, to physically change the shape of the display panel  120  to compensate for the of the distortion aberration. 
     The mechanical unit  130  pulls the sides of the display panel  120  to compensate for a distortion aberration of an optical unit. The translation modules  131  pull the display panel  120  into a curved panel with the sides convex in a barrel shape, using a predetermined motor or actuator, described below. 
     The mechanical unit  130  can adjust the translation length of the display panel for each side independently with the translation modules  131  to fit to a distortion aberration of an optical unit. For example, is, the mechanical unit  130  deforms the sides of the display panel  120  in convex curves by pulling the sides such that the centers of the sides are extended greater than the corners, i.e., with the extension length decreasing from the center to the corners. 
     The mechanical unit  130  can change the shape of the display panel  120  to fit distortion aberrations of various types of optical units according to the design of HMDs. 
     The control unit  140  generates an image signal by processing an image source signal and generates a control signal for displaying an image signal on the display panel  120 . The image source includes an image taken by a camera (not illustrated), an image for exhibiting a user interface (UI), an image stored in a memory, a three-dimensional (3D) image, and a virtual image produced by an installed program. 
     The image source signal can exhibit at least two images based on at least two view points for displaying a 3D image. The control unit  140  transmits an image signal based on an image source signal at a view point on a display panel, which corresponds to the image source signal at the view point, of display panels  120 - 1  and  120 - 2 . 
       FIG. 4  is a conceptual diagram of correcting a distortion aberration due to an optical unit according to an exemplary embodiment. 
     Referring to  FIG. 4 , as described above, in the HMDs of the related art, a pin cushion distortion aberration is generated while a square display image according to the shape of a display panel passes through an optical unit, so the image seen to an eye exhibits a pin cushion shape. 
     On the other hand, in the shape of the display panel  120  according to an exemplary embodiment, the sides are intentionally deformed to compensate for the distortion aberration, e.g., to correct for a pin cushion distortion aberration, the display panel is distorted to be barrel-shaped. 
     In an exemplary embodiment, the barrel-shaped display panel image obtained by deforming the display panel  120  can be defined as a correction image for compensating a distortion aberration due to the optical unit  110 . The barrel-shaped display panel image (i.e. correction image) compensates the pin cushion distortion aberration while passing through the optical unit  110 , so the image actually seen to an eye can be viewed as a normal square image. 
     As described above, correcting a distortion aberration due to an optical unit according to an exemplary embodiment can be simply achieved by physically deforming the display panel  120  with the mechanical unit  130 . 
     Hereafter, the mechanical unit  130  according to an exemplary embodiment will be described in more detail.  FIG. 5  illustrates a configuration of a mechanical unit according to an exemplary embodiment.  FIG. 6  illustrates a cross-sectional view taken along line A-A of a combination structure of an translation module according to an exemplary embodiment. 
     Referring to  FIGS. 5 and 6 , the mechanical unit  130  according to an exemplary embodiment includes translation modules  131 , a driving module  132 , a driving control module  133 , and a distortion analyzing module  134 . 
     The translation modules  131 , as described above, are coupled to the sides of the display panel  120 . The translation modules  131  may be coupled by a bezel unit  121  covering the side of the display panel  120  and a fastener  1311 . The bezel unit  121  may be an elastic member and may receive a side of the display panel  120  in a groove formed at a side and may be integrally fixed to the display panel by an adhesive  122 . 
     The driving module  132  includes an actuator  1321  and a motor  1322  coupled to the translation module  131 . The motor  1322  physically pulls (or pushes) and moves the translation module  131  to a predetermined distance. The predetermined distance means the individual movement distance of translation modules  131  such that the sides are curved or otherwise compensate for distortion. 
     The driving control module  133  adjusts the movement distances of the translation modules  131  such that correction images of the translation modules  131  separated in accordance with a distortion aberration of the screen that a user looks at offset the distortion aberration. The driving control module  133  can adjust the degree of deformation of the display panel  120  on the basis of selection by a user by controlling the driving module  132  through a controller, because the users of an HMD may have different physical characteristics, e.g., different body sizes, different face sizes, different eye spacing, different nose shapes, different nose heights, and so forth. 
     The distortion analyzing module  134  calculates the movement distances of the translation modules  131 , which depend on the size of the display panel  120  and the characteristics of the optical unit  110 , and transmits them to the driving control module  133  so that the positions of the translation modules  131  can be adjusted. 
     According to this configuration, the mechanical unit  130  keeps the display panel  120  extended in the optimal correction image that a user looks at. The translation modules  131  can pull (or push) the display panel  120  directly through the bezel units  121 , depending on how the translation modules  131  are fastened to the display panel  120 . 
       FIGS. 7 to 9  are cross-sectional views taken along line A-A which illustrates a combination structure of another type of translation module according to an exemplary embodiment. In the following description of various fastening manners for the translation modules  131 , description of components of the configuration similar to that described above are not repeated. 
     As illustrated in  FIG. 7 , the bezel unit  121  and the side of the display panel  120  may be fixed by a fastener  1312 , rather than by an adhesive  122 . 
     As illustrated in  FIG. 8 , the translation module  131 , the bezel unit  121 , and the display panel  120  are combined by one fastener  1312 , rather than a separate fastener  1131 . In this case, the translation module  131  can directly pull the display panel  110 . 
     As illustrated in  FIG. 9 , an actuator  1321  may be integrally formed on the bottom of the translation module  131 , reducing a size and/or weight of an HMD. 
       FIG. 10  illustrates an exemplary use of the head mounted display according to an exemplary embodiment. Referring to  FIG. 10 , the head mounted display  100  according to an exemplary embodiment includes a plurality of sets composed of the display panel  120  and the optical unit  110  for both eyes, i.e., each set is for one eye. 
     The control unit  140  of the head mounted display can display 3D images with different parallaxes on display panels  120 - 1  and  120 - 2  for the left and right eyes, respectively. That is, the control unit  140  displays different images for the left eye and the right eye in the HMD, so that a user can view a 3D image. 
       FIG. 11  illustrates a curved flexible display panel according to another exemplary embodiment. Referring to  FIG. 11 , according to another exemplary embodiment, the corners of a flexible display panel  120  may be pushed inward, e.g., towards the optical unit  110 , while not changing dimensions of the display panel, using a mechanical unit (not illustrated). Although the mechanical unit is not illustrated in the figure, as in the previous exemplary embodiment, a mechanical unit to deform the display panel  120  may be provided to push the corners of the display panel inward, so the detailed description is not provided. 
       FIG. 12  illustrates an image formation surface corrected by a curved display panel according to an exemplary embodiment. Referring to  FIG. 12 , the display panel according to an exemplary embodiment is concavely curved without changing dimensions of the display panel. 
     In the existing flat display panels, there was problem in that the image formation surface is bent by a distortion aberration due to an optical unit and becomes out of focus as it goes to the outside, thereby distorting an image. 
     The display panel is concavely curved such that the distance from the optical unit  110  decreases from the center to the periphery, e.g., at the corners, a distortion aberration maybe compensated such that the image is flat undistorted. In particular, the mechanical unit  130  may be push (or pull) corners of the display panel  120  towards the optical unit  110 . 
     As described above, according to an exemplary embodiment, a clear image may be displayed by correcting a distortion aberration due to an optical unit in a head mounted display. Further, since the display panel maybe deformed to compensate for distortion aberrations due to various optical units available for head mounted displays, an image may be simply corrected. Thus, by changing the shape, e.g., curve, stretch, contract, and so forth, of the display to offset distortions in the optical system, a corrected image may be displayed. 
     Further, since distortion aberrations may be corrected by changing the shape of a display panel, a head mounted display may use a simple optical unit rather the existing complicated optical units, decreasing size and/or cost. 
     Finally, while the above description has been directed to a head mount display, embodiments may be employed with other projection systems. 
     Exemplary embodiments are not implemented only by the apparatus and/or method described above, and may be implemented by programs that implement the function of the configurations in the exemplary embodiments or recording medium having the programs, and embodiments can be easily implemented by those skilled in the art from the exemplary embodiments described above. 
     Example embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. In some instances, as would be apparent to one of ordinary skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated. Accordingly, it will be understood by those of skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.