Wearable display apparatus

Abstract

Provided are a wearable display device and a light guide element thereof, the display device including: a display element configured to project a first light forming a virtual image; and a light guide element configured to guide the first light from the display element and a second light input from outside of the wearable display device to a predetermined position. The light guide element includes: a first optical surface facing the display element; a second optical surface and a third optical surface configured to reflect the first light input through the first optical surface; and a fourth optical surface configured to reflect the reflected first light to the predetermined position. The first to third optical surfaces are flat surfaces, and the fourth optical surface is a rotationally asymmetric reflective surface.

What is claimed is: 
     
         1 . A wearable display device comprising:
 a display element configured to project a first light forming a virtual image; and   a light guide element configured to guide the first light from the display element and a second light input from outside of the wearable display device to a predetermined position,   wherein the light guide element comprises:
 a first optical surface through which the first light from the display element is input; 
 a second optical surface configured to reflect the first light input through the first optical surface; 
 a third optical surface configured to reflect the first light input through the first optical surface; and 
 a fourth optical surface configured to reflect the reflected first light, reflected by the second optical surface and the third optical surface, to the predetermined position, 
   wherein the first optical surface, the second optical surface, and the third optical surface are flat surfaces, and   wherein the fourth optical surface is a rotationally asymmetric reflective surface.   
     
     
         2 . The wearable display device of  claim 1 , wherein a distance between an apex of the fourth optical surface and the third optical surface is less than one half of a distance between the second optical surface and the third optical surface. 
     
     
         3 . The wearable display device of  claim 1 , wherein:
 the second optical surface and the third optical surface are parallel to each other; and   the fourth optical surface is inclined with respect to a direction perpendicular to the second optical surface and the third optical surface.   
     
     
         4 . The wearable display device of  claim 1 , wherein the fourth optical surface transmits some of the first light, and reflects a remainder of the first light to the predetermined position. 
     
     
         5 . The wearable display device of  claim 1 , wherein a chief ray of the first light is totally reflected 2n times, where n is a natural number, by the second optical surface and the third optical surface. 
     
     
         6 . The wearable display device of  claim 1 , further comprising a lens system between the first optical surface and the display element and configured to refract the first light projected from the display element. 
     
     
         7 . The wearable display device of  claim 1 , wherein an angle between the second optical surface and the first optical surface is not equal to an angle between the second optical surface and a surface of the display element. 
     
     
         8 . The wearable display device of  claim 1 , wherein:
 the light guide element further comprises:
 a light guide portion comprising the first optical surface, the second optical surface, the third optical surface, and the fourth optical surface, and 
 a compensation portion bonded to the fourth optical surface of the light guide portion, 
 wherein the light guide portion and the compensation portion have powers that have opposite signs and a same absolute value. 
   
     
     
         9 . The wearable display device of  claim 1 , wherein the light guide element further comprises:
 a body between the second optical surface and the third optical surface and having a constant thickness;   a first portion between the first optical surface and the second optical surface and having a thickness that gradually increases towards the display element; and   a second portion between the third optical surface and the fourth optical surface and having a thickness that gradually decreases in a direction away from the display element.   
     
     
         10 . The wearable display device of  claim 1 , wherein the light guide element further comprises:
 a body between the second optical surface and the third optical surface and having a constant thickness;   a first portion between the first optical surface and the second optical surface and having a thickness that gradually decreases towards the display element; and   a second portion between the third optical surface and the fourth optical surface and having a thickness that gradually decreases in a direction away from the display element.   
     
     
         11 . The wearable display device of  claim 1 , further comprising:
 a first window and a second window on a front side of the wearable display device; and   a controller that controls transmissivities of the first window and the second window.   
     
     
         12 . The wearable display device of  claim 11 , wherein the controller is configured to control the transmissivities of the first window and the second window by controlling a voltage applied to the first window and the second window. 
     
     
         13 . The wearable display device of  claim 11 , wherein the controller is configured to control the transmissivities of the first window and the second window according to a luminous intensity of a surrounding environment. 
     
     
         14 . The wearable display device of  claim 13 , further comprising a sensor configured to measure the luminous intensity of the surrounding environment. 
     
     
         15 . The wearable display device of  claim 1 , further comprising a touch sensor configured to sense at least one of a touch and a hovering gesture. 
     
     
         16 . The wearable display device of  claim 15 , wherein:
 the touch sensor is configured to recognize a fingerprint; and   the wearable display device further comprises a controller configured to, when first fingerprint data is input through the touch sensor, compare the first fingerprint data and second fingerprint data that is previously stored and to, when the first fingerprint data and the second fingerprint data correspond to each other according to the comparing, perform a function mapped to the second fingerprint data.   
     
     
         17 . The wearable display device of  claim 16 , wherein the mapped function is one of an unlock function, an application execution function, a user account change function, and a multimedia control function. 
     
     
         18 . The wearable display device of  claim 1 , further comprising:
 a communicator configured to receive touch information from an external electronic device; and   a controller configured to change, according to the received touch information, a virtual image displayed on the wearable display device to another virtual image.   
     
     
         19 . The wearable display device of  claim 1 , further comprising:
 a first camera configured to capture an image of a front subject with reference to a position of the light guide element;   a second camera configured to capture an image of a lower subject with reference to the position of the light guide element; and   a controller configured to recognize a hand or a finger from the image captured through the second camera, and to change a virtual image displayed on the wearable display device to another virtual image according to a gesture of the recognized hand or the recognized finger.   
     
     
         20 . The wearable display device of  claim 1 , further comprising a light shielding member on the second optical surface or the third optical surface to absorb some of the first light or to extract some of the first light to an outside of the light guide element. 
     
     
         21 . The wearable display device of  claim 1 , further comprising an actuator configured to move the light guide element. 
     
     
         22 . The wearable display device of  claim 1 , further comprising:
 a light source configured to output a third light towards the predetermined position; and   an image sensor configured to receive a reflected portion of the third light through the light guide element.   
     
     
         23 . The wearable display device of  claim 22 , further comprising at least one actuator configured to move the light guide element and the image sensor together. 
     
     
         24 . The wearable display device of  claim 1 , further comprising a transparent cover glass on a surface of the display element facing the light guide element, to protect the surface of the display element. 
     
     
         25 . A light guide element for a display device, the light guide element comprising:
 a first optical surface configured to receive first light from a display element of the display device;   a second optical surface configured to reflect the first light received through the first optical surface;   a third optical surface configured to reflect the first light input received through the first optical surface; and   a fourth optical surface configured to reflect the reflected first light, reflected by the second optical surface and the third optical surface, toward a predetermined position to form a virtual image, and to transmit a second light input from an outside toward the predetermined position,   wherein the first optical surface, the second optical surface, and the third optical surface are flat surfaces, and   wherein the fourth optical surface is a rotationally asymmetric reflective surface.   
     
     
         26 . The light guide element of  claim 25 , wherein a distance between an apex of the fourth optical surface and the third optical surface is less than one half of a distance between the second optical surface and the third optical surface. 
     
     
         27 . The light guide element of  claim 25 , wherein:
 the second optical surface and the third optical surface are parallel to each other; and   the fourth optical surface is inclined with respect to a direction perpendicular to the second optical surface and the third optical surface.   
     
     
         28 . The light guide element of  claim 25 , wherein the fourth optical surface transmits some of the first light, and reflects a remainder of the first light toward the predetermined position. 
     
     
         29 . The light guide element of  claim 25 , wherein a chief ray of the first light is totally reflected 2n times, where n is a natural number, by the second optical surface and the third optical surface. 
     
     
         30 . The light guide element of  claim 25 , further comprising:
 a light guide portion comprising the first optical surface, the second optical surface, the third optical surface, and the fourth optical surface; and   a compensation portion connected to the fourth optical surface of the light guide portion,   wherein the light guide portion and the compensation portion have powers that have opposite signs and a same absolute value.   
     
     
         31 . The light guide element of  claim 25 , further comprising:
 a body between the second optical surface and the third optical surface and having a constant thickness;   a first portion between the first optical surface and the second optical surface and having a thickness that gradually increases towards the display element; and   a second portion between the third optical surface and the fourth optical surface and having a thickness that gradually decreases in a direction away from the display element.   
     
     
         32 . The light guide element of  claim 25 , further comprising:
 a body between the second optical surface and the third optical surface and having a constant thickness;   a first portion between the first optical surface and the second optical surface and having a thickness that gradually decreases towards the display element; and   a second portion between the third optical surface and the fourth optical surface and having a thickness that gradually decreases in a direction away from the display element.   
     
     
         33 . The light guide element of  claim 25 , further comprising a light shielding member on the second optical surface or the third optical surface to absorb some of the first light or to extract some of the first light to an outside of the light guide element. 
     
     
         34 . A display device comprising:
 a display element configured to output a first light forming a virtual image; and   a light guide element configured to guide the first light from the display element toward a predetermined position,   wherein the light guide element comprises:
 a first optical surface through which the first light from the display element is input; 
 a second optical surface configured to reflect the first light input through the first optical surface; 
 a third optical surface configured to reflect the first light input through the first optical surface; and 
 a fourth optical surface configured to reflect the reflected first light, reflected by the second optical surface and the third optical surface, to the predetermined position, 
   wherein the fourth optical surface is a rotationally asymmetric reflective surface.   
     
     
         35 . The display device of  claim 34 , wherein a distance between an apex of the fourth optical surface and the third optical surface is less than one half of a distance between the second optical surface and the third optical surface. 
     
     
         36 . The display device of  claim 34 , wherein:
 the second optical surface and the third optical surface are parallel to each other; and   the fourth optical surface is inclined with respect to a direction perpendicular to the second optical surface and the third optical surface.   
     
     
         37 . The display device of  claim 34 , wherein the fourth optical surface transmits some of the first light, and reflects a remainder of the first light to the predetermined position. 
     
     
         38 . The display device of  claim 34 , wherein a chief ray of the first light is reflected 2n times, where n is a natural number, by the second optical surface and the third optical surface.