Abstract:
A wearable display system having at least one display panel to display a signal processed in a predetermined way. The system includes a waveguide to transmit a signal that is incident thereon from the display panel and at least one magnifying lens attached to an end of the waveguide to magnify the signal transmitted via the waveguide, wherein at least one end of the waveguide is diagonally cut at a predetermined angle so that the signal output from the display panel is totally reflected inside the waveguide. The wearable display system is easy to make with a minimum number of optical devices, and therefore it is possible to reduce manufacturing cost and time.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims the benefit of Korean Application Nos. 2001-23342 filed on Apr. 30, 2001 and 2001-51585 filed on Aug. 25, 2001 in the Korean Industrial Property Office, the disclosures of which are incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a personal display system, and more particularly, to a wearable display system to display a display signal which is transmitted through a magnifying optical device such as an eyeglass-type or goggle-type optical device, at a location near an eye of a user, and a process thereof.  
           [0004]    2. Description of the Related Art  
           [0005]    Conventional optical display systems used in the military, medicine or for personal entertainment, which are generally known as head (helmet) mounted display (HMD) systems, have been designed for users to see video signals magnified via an eyeglass-type, goggle-type or helmet-type wearable device. This personal display system allows users to receive video information while moving from place to place.  
           [0006]    [0006]FIG. 1 shows an example of an HMD. Referring to FIG. 1, the HMD is made of eyeglasses  100  and an image-driving unit  110  that is attached at the center of the eyeglasses  100 . Because of the image-driving unit  110 , the HMD is bulky, heavy and not elegant. The image-driving unit  110  includes many optical elements and is therefore heavy and large.  
           [0007]    [0007]FIG. 2 shows the structure of a general HMD. In FIG. 2, the HMD includes an image-driving unit  200 , a display panel  210  and an optical system  220 . The image-driving unit  200  stores an image signal received from exterior sources such as a personal computer (PC) or video device (not shown), processes the received signal and displays the signal on the display panel  210 , which may be a liquid crystal display (LCD) panel. The optical system  220  makes the image signal displayed on the display panel  210  appear as an appropriate virtual image in the eye of a user via an enlargement optical system. The HMD can further include any wearable devices or cables to receive image signals from an external source.  
           [0008]    [0008]FIG. 3 shows the general structure of the optical system  220  of the general HMD of FIG. 2. A conventional optical system includes a collimating lens  300 , an X prism  310 , focusing lenses  320 , fold mirrors  330  and ocular lenses (or magnifying lenses)  340 . The collimating lens  300  collimates and propagates light (an image signal) emitted from the display panel  210 . The X prism  310  redirects the light received from the collimating lens  300  in both the right and left directions. The focusing lenses  320  are separately placed on the right and left of the X prism  310  so that collimated light passing through the X prism  310  is focused. The fold mirrors  330  change the direction of incident light so that the light focused by the focusing lenses  320  travels toward the eyes of a user. The ocular lenses (or magnifying lenses)  340  allow small image signals passing through the above-described optical elements to appear in the eyes of the user. At this time, if an image signal transmitted through the ocular lenses  340  has color, lenses to remove chromatic aberration must be used as the ocular lenses  340 .  
           [0009]    In a general HMD, an optical system employs several optical elements to meet precise design specifications, such as a collimating lens, an X prism, focusing lenses, fold mirrors, ocular lenses and the like, as described above. For this reason, it is difficult to manufacture the general wearable display system because much time and effort are required . Even if the lenses and elements are designed precisely, additional difficulties in aligning the lenses and devices together may occur. In addition, the conventional optical system is bulky and heavy due to the use of a plurality of optical devices, so that it is inconvenient for a person to wear the HMD and it is expensive to manufacture the HMD.  
         SUMMARY OF THE INVENTION  
         [0010]    Accordingly, it is an object of the present invention to provide a wearable display system that is simple to manufacture using a minimum number of optical devices.  
           [0011]    Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.  
           [0012]    The foregoing and other objects of the present invention are achieved by providing a wearable display system including at least one display panel to display a signal processed in a predetermined way; a waveguide to transmit a signal that is incident thereon from the display panel, the waveguide having first and second ends; and at least one magnifying lens attached to one of the ends of the waveguide to magnify the signal transmitted via the waveguide, wherein at least one of the ends of the waveguide is diagonally cut at a predetermined angle so that the signal displayed by the display panel is totally reflected inside the waveguide.  
           [0013]    The foregoing and other objects of the present invention are also achieved by providing a wearable display system including a display panel to display a signal processed in a predetermined way; a waveguide to transmit the signal incident thereon from the display panel, the waveguide having first and second ends; and an optical device attached to a surface of the waveguide, the optical device to magnify the signal transmitted via the waveguide, wherein the first and second ends of the waveguide are diagonally cut at first and second angles, respectively.  
           [0014]    The foregoing and other objects of the present invention are also achieved by providing a wearable display system including a display panel to display a signal processed in a predetermined way; a waveguide to transmit the signal incident thereon from the display panel; a prism attached to a first end of the waveguide, the prism to transmit the signal displayed by the display panel into the waveguide at an angle such that the transmitted signal undergoes total internal reflection inside the waveguide; and an optical device to magnify the signal transmitted via the waveguide, wherein a second end of the waveguide, opposite the first end, is cut at a predetermined angle.  
           [0015]    The foregoing and other objects of the present invention are also achieved by providing a wearable display system including a display panel to display a signal processed in a predetermined way; a waveguide to transmit the signal incident thereon from the display panel; and a prism attached to a first end of the waveguide to emit the signal transmitted via the waveguide, wherein a second end of the waveguide, upon which the signal is incident from the display panel, is cut at a predetermined angle. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    These and other objects and advantages of the invention will become apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which:  
         [0017]    [0017]FIG. 1 is an exterior view of a head mounted display (HMD);  
         [0018]    [0018]FIG. 2 is a block diagram of a general HMD;  
         [0019]    [0019]FIG. 3 is a schematic diagram of the optical system of the general HMD of FIG. 2;  
         [0020]    [0020]FIGS. 4A and 4B are a front view and an upper side view, respectively, of a wearable display system according to the present invention;  
         [0021]    [0021]FIG. 5 is a schematic diagram of a wearable display system according to an embodiment of the present invention;  
         [0022]    [0022]FIG. 6 is a schematic diagram of a wearable display system according to another embodiment of the present invention;  
         [0023]    [0023]FIG. 7 is a schematic diagram for explaining parameters of a magnifying optical system which are needed in determining the size of a display panel, the size and position of a screen, an eye relief, a field of view (FOV) and the focus and size of a lens;  
         [0024]    [0024]FIGS. 8A and 8B are schematic diagrams for explaining specifications of a wearable display panel according to the present invention;  
         [0025]    [0025]FIG. 9 is a schematic diagram of a binocular wearable display system according to an embodiment of the present invention;  
         [0026]    [0026]FIG. 10 is a schematic diagram of a binocular wearable display system according to another embodiment of the present invention;  
         [0027]    [0027]FIG. 11 is a schematic diagram of a wearable display system according to another embodiment of the present invention;  
         [0028]    [0028]FIG. 12 is a schematic diagram of a wearable display system according to another embodiment of the present invention; and  
         [0029]    [0029]FIG. 13 is a schematic diagram of a wearable display system according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]    Reference will now be made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.  
         [0031]    [0031]FIGS. 4A and 4B are a front view and an upper side view of a wearable display system according to the present invention, respectively. In FIGS. 4A and 4B, the wearable display system has a simple structure in which a lens  400  and a display panel  410  are combined with each other. The wearable display system of FIGS. 4A and 4B is thinner, lighter and smaller than the conventional designs due to the use of a grating and a magnifying lens. Thus, the wearable display system according to the present invention is easy and convenient to wear, like eyeglasses, unlike existing bulky and heavy helmet-type HMDs. Furthermore, the present invention provides a module-type wearable display system in which a module is capable of being attached to and detached from conventional eyeglasses. The exterior of the wearable display system illustrated in FIGS. 4A and 4B is just an example and a variety of thin, light and small wearable display systems having different exteriors can be realized.  
         [0032]    A wearable display system according to the present invention can be manufactured both as a binocular type and a monocular type. A binocular type is designed for a user to look at a display image using both of his or her eyes, whereas a monocular type allows a user to look at a display image using only one of his or her eyes.  
         [0033]    First, a monocular-type wearable display system will be described below.  
         [0034]    [0034]FIG. 5 is a view of a monocular-type wearable display system according to an embodiment of the present invention. The wearable display system includes a display panel  500  which displays a signal processed in a predetermined way, a waveguide  510  and a magnifying lens  520 . A signal is incident on the waveguide  510  from the display panel  500 , and enters and propagates through the waveguide  510 . An end of the waveguide  510 , which is positioned in the direction of the transmitted signal, is diagonally cut at the same angle as the total internal reflection angle of the signal so that a signal received from the display panel  500  is perpendicularly incident on the cut end of the waveguide  510  and reflected at an angle of total internal reflection once inside the waveguide  510 . The signal which is transmitted from the cut end propagates through the waveguide  510  by being reflected at the total internal reflection angle. The magnifying lens  520  magnifies the signal propagating through the waveguide  510  to be formed as an image in an eye of a user.  
         [0035]    [0035]FIG. 6 is a view of a monocular-type wearable display system according to another embodiment of the present invention. Referring to FIG. 6, the wearable display system further includes a reflector  600 . With the reflector  600 , it is possible to easily control the position of a light source which emits light to be incident on the cut end of the waveguide  510 . In the wearable display system shown in FIG. 6, light output from the light source at a corner is reflected from the reflector  600  and is transmitted through the cut end of the waveguide  510  to be incident on the inner side of the waveguide  510  at the total internal reflection angle. If the light source is placed at a same side as a user, it is possible to realize an eyeglass type display system having a light source on the arms of the frame thereof.  
         [0036]    To realize the wearable display systems shown in FIGS. 5 and 6, the size of the magnifying lens  520 , the number of times a signal undergoes total reflection in the waveguide  510 , and the length and width of the waveguide  510  must be determined, according to basic principles of a magnifying optical system.  
         [0037]    [0037]FIG. 7 is a diagram for explaining parameters of a magnifying optical field which are needed in determining a size of a display panel, a size and location of a screen, an eye relief, a field of view (FOV), a focus and size of a lens, and so on. Referring to FIG. 7, F denotes a focal length of a lens  700  corresponding to the magnifying lens  520  shown in FIG. 5, and D denotes the diameter of the lens  700 . Yo denotes the size of an object  710  that corresponds to the display panel  500  shown in FIG. 5. So denotes a distance between the object  710  and the lens  700 , which corresponds to the distance between the display panel  500  and the magnifying lens  520 . Here, So must be shorter than the focal distance F of the lens  700  so that an image of the object  710  is magnified to the eye of a user. According to this optical principle, the path of a signal which is incident upon and propagates in the waveguide  510 , is designed to be shorter than the focal distance of the magnifying lens  520  in FIG. 5. Yi denotes the size of a virtual image of the object  710  to be seen at a position of a user&#39;s eye  720  and Ex is the size of an exit pupil of the user&#39;s eye  720 . Le denotes a distance between the eye of the user  720  and the lens  700 , i.e., eye relief, L′ denotes a distance between the user&#39;s eye  720  and the virtual image Yi, and θ/2 denotes half of a field of view (FOV) defined below. Si denotes a distance between the virtual image and the lens  700 .  
         [0038]    Hereinafter, we will explain a process of obtaining parameters of a magnifying lens using the above-described optical parameters. To determine the type of the lens  700  and the position of the object  710  in FIG. 7, the size Yo of the object  710 , the size Yi of the virtual image, the distance L′ between the virtual image and the eye of the user  720 , the eye relief Le and the exit pupil Ex of the eye of the user  720  must first be determined. Using these optical parameters, a magnification M is obtained by the following expression (1):  
             M   =         Y                 i       Y                 o       =       S                 i       S                 o                 (   1   )                               
 
         [0039]    The distance So between the lens  700  and the object  710  can be measured by applying the obtained M value to the following expression ( 2 ):  
               S                 o     =       S                 i     M             (   2   )                               
 
         [0040]    Next, the focal length F of the lens  700  is calculated using So and Si as follows:  
                 1     S                 o       -     1     S                 i         =     1   f             (   3   )                               
 
         [0041]    Then, the field of view (FOV) is calculated as follows:  
               F                 O                   V   θ       =     2        tan     -   1              Y                 i       2        L   ′                   (   4   )                               
 
         [0042]    The diameter D of the lens  700  is measured as follows:  
               tan        θ   2       =     D     2      L                 e               (   5   )                               
 
         [0043]    Expression (5) applies only to a light signal that is incident upon the center of the exit pupil Ex, and therefore, the real diameter D of the lens  700  must be measured as a function of the size of the exit pupil as follows:  
             D   =       2      L                 e                 tan        θ   2       +     E                 x               (   6   )                               
 
         [0044]    As described above, the particulars of a magnifying lens can be determined using the above expressions.  
         [0045]    [0045]FIGS. 8A and 8B are diagrams for explaining the design specifications of a wearable display system according to an aspect of the present invention. FIG. 8A illustrates a waveguide  810 . Referring to FIG. 8B, an angle of incidence θ must be larger than a critical angle of total reflection θ c , and the length d/sinθ of an inclined end of a waveguide must be greater than the length of the display panel. These conditions are expressed as follows:  
               θ   &gt;     θ   c       =       sin     -   1            1     n        (     w                 a                 v                 e                 g                 u                 i                 d                 e     )                   (   7   )                               
 
         [0046]    wherein n (waveguide) denotes an index of refraction of the waveguide  810 . For instance, when the index of refraction of the waveguide  810  is 1.49, the critical angle of total reflection θ c  is 42.2 degrees and thus, the angle of incidence θ must be greater than 42.2 degrees.  
         [0047]    [0047]FIG. 9 is a view of a binocular wearable display system according to an embodiment of the present invention. The binocular wearable display system includes a waveguide  900 , a first display panel  910 , a second display panel  920 , a first magnifying lens  930  and a second magnifying lens  940 . The principles and specifications of the wearable monocular type display systems described above can be applied to the binocular wearable display system shown in FIG. 9. Furthermore, two monocular-type wearable display systems shown in FIG. 5 can be combined with each other to form a binocular wearable display system such as that shown in FIG. 9. The waveguide  900  receives signals from the first and second display panels  910  and  920 , and guides the propagation of the signals. Both ends of the waveguide  900  are diagonally cut to have the same angle as the angle of total internal reflection so that the signals which are transmitted through both ends are reflected at the angle of total internal reflection once inside the waveguide  900 . Display signals are perpendicularly incident on the inclined ends of the waveguide  900 , reflected at the angle of total internal reflection in the waveguide  900  and propagate towards the center of the waveguide  900 . The first display panel  910  is attached to the left inclined end of the waveguide  900  to be incident on the inner wall thereof, and transmits a signal into the waveguide  900  at the angle of total internal reflection. The first magnifying lens  930  magnifies a signal which is reflected more than one time in the waveguide  900  and reaches the first magnifying lens  930 , to be seen by the left eye of a user. The second display panel  920  is attached to the right inclined end of the waveguide  900  and transmits a signal into the waveguide  900  at the angle of total reflection. The second magnifying lens  940  magnifies a signal which is reflected more than one time in the waveguide  900 , to be seen by the right eye of the user. The first and second magnifying lenses  930  and  940  may be hologram lenses that transmit a signal incident thereon at a predetermined angle (which is the predetermined angle of total internal reflection in this embodiment) in a direction which is consistent with the direction of a pattern on the hologram lens.  
         [0048]    [0048]FIG. 10 is a view of a binocular wearable display system according to another embodiment of the present invention. The binocular wearable display system shown in FIG. 10 has the same structure and function as the binocular wearable display system shown in FIG. 9, but further includes first and second reflection plates  1010  and  1020 . The first and second reflection plates  1010  and  1020  extend from both ends of a waveguide  1000  and reflect light from light sources at predetermined right and left directions of a user toward the inclined ends of the waveguide  1000 . In other words, the first and second reflection plates  1010  and  1020  reflect light from light sources placed so that the light is to be incident on the inclined ends of the waveguide  1000  as collimating light. As shown in FIG. 10, since light sources can be placed at either side of the user with the first and second reflection plates  1010  and  1020 , it is possible to realize an eyeglass-type wearable display system having light sources at the frame arms.  
         [0049]    [0049]FIG. 11 is a view of a monocular-type wearable display system according to another embodiment of the present invention. The wearable display system includes a display panel  1100  to display a signal processed in a predetermined way, a waveguide  1110  and an optical device  1120 .  
         [0050]    The waveguide  1110  guides the propagation of a signal incident from the display panel  1100  and has two ends that are diagonally cut at a predetermined angle that reflects an incident signal at the angle of total internal reflection from an inner wall of the waveguide  1110 . The signal is incident on one of the ends and is emitted through the other end . The signal is incident on the end which is inclined at the angle of total internal reflection, transmitted into the waveguide  1110  and repeatedly reflected at the angle of total reflection to propagate through the waveguide  1110 . The optical device  1120  is a diffractive optical element or a holographic optical element and magnifies the received signal after transmission through the waveguide  1110  to form a magnified image in the eye of the user, who is positioned within a predetermined focal distance. Here, the optical device  1120  is illustrated as a reflection type, but may also be a transmittance type that forms an image of a signal at the opposite side of the waveguide  1110  illustrated in FIG. 11.  
         [0051]    When signals emitted from the display panel  1100  propagate through the waveguide  1110  and are output through the optical device  1120 , propagation distances of the incident signals may be different from each other, thus generating an aberration. To prevent this aberration, the end of the waveguide  1110  on which the signal is incident must have the same inclination angle as the end of the waveguide  1110  from which the signal is emitted, so that the propagation distances of the incident signals are the same.  
         [0052]    The basic principles of the magnifying optical system explained with reference to FIG. 7 are applied in determining the specifications of the waveguide  1110 , i.e., the angle of the inclined ends, the number of times a signal propagating therethrough undergoes total internal reflection, the length and width of the waveguide  1110 , the diameter of the optical device  1120 , the focal length of the optical device  1120  and so on.  
         [0053]    [0053]FIG. 12 is a view of a monocular-type wearable display system according to another embodiment of the present invention. The wearable display system includes a display panel  1200  to emit a signal processed in a predetermined way, a prism  1210 , a waveguide  1220  and an optical device  1230 . The prism  1210  is attached to one side of the waveguide  1220  and has the display panel  1200  on a surface thereof. A signal output from the display panel  1200  is transmitted through the prism  1210  into the waveguide  1220  at a predetermined angle of total internal reflection.  
         [0054]    The signal enters the waveguide  1220  via the prism to be repeatedly reflected from the inner surface of the waveguide  1220  at the angle of total internal reflection and propagates through the waveguide  1220 . The surface of the waveguide  1220  from which the signal is output is cut at a predetermined angle so that the propagation distance of incident signals through the prism  1210  can be the same, thereby preventing an aberration due to a difference in propagation distance between signals. Here, the inclination angles of both ends of the waveguide  1220  are the same as the incident angle, i.e., the angle of total internal reflection.  
         [0055]    The optical device  1230  is a diffractive optical element or a holographic optical element and magnifies a signal that is transmitted via the waveguide  1220  to be formed as an image in the eye of the user. The optical device  1230  is illustrated as a reflection type in FIG. 12, but may be a transmission type that forms an image of a signal at the opposite side of the waveguide  1220 , as shown in FIG. 12.  
         [0056]    Here, the basic principles of the magnifying optical system are also applied in determining the specifications of the waveguide  1220 , i.e., the angle of the inclined ends of the waveguide  1220 , the number of times the signal undergoes total internal reflection therein, the length and width of the waveguide  1220 , the diameter of the optical device  1230  and the distance at which the signal is focused to form the image.  
         [0057]    [0057]FIG. 13 is a view of a monocular-type wearable display system according to another embodiment of the present invention. In the wearable display system shown in FIG. 13, a waveguide  1320  has the same structure and elements as the waveguide  1220  shown in FIG. 12. However, the location of a display panel  1300  and the propagation direction of a signal are opposite to those of the wearable display system shown in FIG. 12. The display panel  1300  is attached to the end of the waveguide where the optical device  1230  shown in FIG. 12 is positioned, and a magnifying lens  1330  is attached to the end where the display panel  1200  shown in FIG. 12 is positioned. In FIG. 13, a signal incident on the display panel  1300  is transmitted out of the waveguide  1320  via a prism  1310  and is magnified by the magnifying lens  1330  attached to the prism  1310  to be seen by the eye of the user.  
         [0058]    As described above, a wearable display system according to embodiments of the present invention includes a waveguide having an end or ends that are diagonally cut so that a signal can be reflected within the waveguide, thus not requiring any elements to reflect a signal at an angle of total internal reflection. Further, light sources can be freely positioned as desired using a reflection plate.  
         [0059]    Although a few preferred embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.