Patent Publication Number: US-2022222026-A1

Title: Head-Mounted Display Device and Display Method Thereof

Description:
This application claims priority to Chinese Patent Application No. 201910478280.X, filed with the China National Intellectual Property Administration on Jun. 3, 2019 and entitled “HEAD-MOUNTED DISPLAY DEVICE AND DISPLAY METHOD THEREOF”, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     This application relates to the field of head-mounted display device technologies, and in particular, to a head-mounted display device and a display method thereof. 
     BACKGROUND 
     A head-mounted display device (Head Mount Display, HMD for short hereinafter) is also called a head display. The HMD magnifies, by using a group of optical systems (mainly precision optical lenses), an image that is displayed on an ultra-micro display, projects the image on a retina, and then presents a large-screen image to a user&#39;s eyes. By sending an optical signal to the user&#39;s eyes through various head displays, virtual reality (virtual reality, VR for short hereinafter) and augmented reality (augmented reality, AR for short hereinafter) can be implemented. 
     Currently, the head-mounted display device is basically a binocular display device. Because display power consumption accounts for more than half of power consumption of the entire device, the power consumption causes the entire device to heat up and working time to decrease, and high power consumption affects a lifespan and safety of a battery. In a case of a given working time requirement, reduction of the power consumption can effectively reduce a battery power requirement, thereby reducing weights and volumes of the battery and the entire device. On the other hand, a lifespan of a display component is limited, and continuous working for a long time accelerates aging of the display component. In addition, compared with a lifespan of another component of the entire device, the lifespan of the display component is shorter and is a short board that determines a lifespan of the entire device. 
     Power consumption of an entire display system mainly includes power consumption of a display source (that is, a light source) and that of a display driver. Existing methods for reducing display power consumption mainly include: method (1): directly reducing display brightness of the AR or VR; and method (2): indirectly reducing display brightness of the AR through auxiliary shading. 
     However, the two methods both have drawbacks. The method (1) is not applicable to all scenarios, for example, cases in which the AR is used in an outdoor environment and in a bright environment. In addition, reducing the display brightness may affect user experience of using the AR and VR. Use of the method (2) may affect determining of a real environment, which incurs safety risks. On the other hand, only the power consumption of the display source can be reduced by reducing the display brightness, but the power consumption of the display driver is not reduced. However, the power consumption of the display driver accounts for more than half of the power consumption of the entire display system. 
     SUMMARY 
     This application provides a head-mounted display device and a display method thereof, to reduce power consumption of a display system of the head-mounted display device. 
     According to a first aspect, this application provides a display method of a head-mounted display method that is applied to a display control unit of the head-mounted display device and that includes: determining a current display mode in response to that the head-mounted display device enables a low power consumption display mode; determining a switching time interval based on the current display mode; controlling a left-eye display system to display an image and controlling a right-eye display system to be turned off; in response to that display duration of the left-eye display system reaches first preset duration, turning off the left-eye display system and maintaining an off state of the right-eye display system; and in response to that an off state of the left-eye display system lasts for the switching time interval, controlling the right-eye display system to display the image and maintaining the off state of the left-eye display system. 
     The display method further includes: in response to that display duration of the right-eye display system reaches second preset duration, turning off the right-eye display system and maintaining the off state of the left-eye display system; and in response to that the off state of the right-eye display system lasts for the switching time interval, controlling the left-eye display system to display the image and maintaining the off state of the right-eye display system. 
     According to the solution provided in this embodiment, when the head-mounted display device enables the low power consumption display mode, the left-eye display system and the right-eye display system of the head-mounted display device alternately display a image (to be specific, the left-eye display system and the right-eye display system are switched in turn to display the image) instead of displaying the image. The switching time interval for the left-eye display system and the right-eye display system to alternately display the image is determined based on the current display mode. Different current display modes may be corresponding to different switching time intervals, or may be corresponding to a same switching time interval. Therefore, in the low power consumption display mode, only one display system (the left-eye or right-eye display system) displays the image within a same time period, and thus power consumption of the display systems of the head-mounted display device is reduced. Further, both the left-eye display system and the right-eye display system are in the off state within the switching time interval between the two display systems, so that human eyes can adapt to switching between both eyes more comfortably. 
     If the current display mode is a two-dimensional display mode, the switching time interval is a first switching time interval, or if the current display mode is a three-dimensional display mode, the switching time interval is a second switching time interval, where the second switching time interval is less than the first switching time interval. 
     According to the solution provided in this embodiment, when being the two-dimensional display mode or the three-dimensional display mode, the current display mode is corresponding to a different switching time interval (the two-dimensional display mode is corresponding to the first switching time interval, and the three-dimensional display mode is corresponding to the second switching time interval). Compared with the two-dimensional display mode, the three-dimensional display mode requires a user to perceive a image of a three-dimensional display effect through both eyes. Therefore, the second switching time interval is less than the first switching time interval. 
     Optionally, if the current display mode is the two-dimensional display mode, when the left-eye display system displays the image, a brightness grayscale of the image displayed by the left-eye display system is adjusted, or when the right-eye display system displays the image, a brightness grayscale of the image displayed by the right-eye display system is adjusted. 
     According to the solution provided in this embodiment, in the two-dimensional display mode, only one display system displays a image within a same time period, but the user can still perceive the image through both eyes by adjustment of a position of the image (for example, when the left-eye display system displays the image, the image is positioned more rightward than that simultaneously displayed by the left-eye and right-eye display systems). However, the user may perceive a brightness grayscale difference on the whole (for example, when only the left-eye display system displays the image, the user may perceive, on the whole, that a brightness grayscale of the image is adjusted, and brightness of the image gradually decreases from left to right). In view of that, the brightness grayscale of the image is adjusted by using a software policy in this embodiment. For example, in each image frame, a region perceived to be dark by the brain is brightened in advance, and a region perceived to be bright by the brain is darkened in advance, to ensure consistency in overall imaging perception for an image output for display. 
     Optionally, the head-mounted display method further includes: determining, based on an environmental parameter or a user-input instruction, that the head-mounted display device enables the low power consumption display mode. The environmental parameter includes a temperature of the head-mounted display device or a battery level of the head-mounted display device. 
     According to the solution provided in this embodiment, a manner of display switching between each eye is used only when the head-mounted display device enables the low power consumption display mode, to reduce the power consumption of the display systems. Therefore, by adding a function of display switching between each eye on a basis of an existing function of simultaneous display to both eyes, a function of normal display to both eyes is not affected in the head-mounted display device. In addition, when the temperature or power of the head-mounted display device is lower than a critical value (that is, the current environmental parameter is less than the critical value), or an instruction that is sent by the user and that is for switching to the low power consumption display mode is received, the low power consumption display mode is enabled, which can reduce the power consumption of the display systems. In this way, lifespans of a component and a battery that are of the head-mounted display device are prolonged, thereby prolonging a lifespan of the entire device. 
     According to a second aspect, this application provides a head-mounted display apparatus, including a display control unit, a left-eye display system, and a right-eye display system. The left-eye display system is configured to display an image. The right-eye display system is configured to display an image. The display control unit is configured to: determine a current display mode in response to that the head-mounted display device enables a low power consumption display mode; determine a switching time interval based on the current display mode; control the left-eye display system to display an image and control the right-eye display system to be turned off; in response to that display duration of the left-eye display system reaches first preset duration, turn off the left-eye display system and maintain an off state of the right-eye display system; and in response to that an off state of the left-eye display system lasts for the switching time interval, control the right-eye display system to display the image and maintain the off state of the left-eye display system. 
     The display control unit is further configured to: in response to that display duration of the right-eye display system reaches second preset duration, turn off the right-eye display system and maintain the off state of the left-eye display system; and in response to that the off state of the right-eye display system lasts for the switching time interval, control the left-eye display system to display the image and maintain the off state of the right-eye display system. 
     The first preset duration is equal to the second preset duration. 
     The display control unit is further configured to: if the current display mode is a two-dimensional display mode, determine that the switching time interval is a first switching time interval, or if the current display mode is a three-dimensional display mode, determine that the switching time interval is a second switching time interval, where the second switching time interval is less than the first switching time interval. 
     The display control unit is further configured to: if the current display mode is the two-dimensional display mode, when the left-eye display system displays the image, adjust a brightness grayscale of the image displayed by the left-eye display system, or when the right-eye display system displays the image, adjust a brightness grayscale of the image displayed by the right-eye display system. 
     The display control unit is further configured to: determine the first preset duration based on a preset quantity of frames of left-eye display; and determine the second preset duration based on a preset quantity of frames of right-eye display. 
     The quantity of frames of left-eye display is equal to the quantity of frames of right-eye display. 
     The display control unit is further configured to: based on an environmental parameter or a user-input instruction, determine that the head-mounted display device enables the low power consumption display mode. 
     The environmental parameter includes a temperature of the head-mounted display device or a battery level of the head-mounted display device. 
     According to the solution provided in this embodiment, the head-mounted display device may be a virtual reality head-mounted display device. Because this type of display is configured to display an image, the two-dimensional display mode or the three-dimensional display mode may be used based on an application requirement. The head-mounted display device may alternatively be an augmented reality head-mounted display device. Because in this type of display, a generated image is superimposed on a basis of a real environment, the three-dimensional display mode is mainly used. 
     It can be learned that, in the foregoing aspects, the low power consumption display mode is set in the head-mounted display device; and when the head-mounted display device enables and enters the low power consumption display mode, the display control unit determines corresponding switching time intervals based on different current display modes, and separately controls the left-eye display system and the right-eye display system to alternately display the image based on the determined switching time intervals. In this way, power consumption of the display systems may be reduced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       To describe the technical solutions in the embodiments of this application more clearly, the following briefly describes the accompanying drawings used in the embodiments. Apparently, the accompanying drawings in the following description show merely some embodiments of this application, and a person of ordinary skill in the art may still derive other drawings from these accompanying drawings without creative efforts. 
         FIG. 1  is a schematic flowchart of a first display method of a head-mounted display device according to an embodiment of this application; 
         FIG. 2A  is a schematic diagram of an image position perceived by a user when a left-eye display system and a right-eye display system display an image in the conventional technology; 
         FIG. 2B  is a schematic diagram of an image position perceived by a user when only a left-eye display system displays an image (compared with two display systems simultaneously displaying an image), and a position of the displayed image is not adjusted; 
         FIG. 3  is a schematic diagram of an image position perceived by a user when only a left-eye display system displays an image, and a position of the displayed image is adjusted; 
         FIG. 4  is a schematic flowchart of a second display method of a head-mounted display device according to an embodiment of this application; 
         FIG. 5A  is a schematic diagram of controlling a left-eye display system and a right-eye display system to alternately display an image in a two-dimensional display mode according to the embodiment shown in  FIG. 4 ; 
         FIG. 5B  is a schematic diagram of controlling a left-eye display system and a right-eye display system to alternately display an image in a three-dimensional display mode according to the embodiment shown in  FIG. 4 ; 
         FIG. 6  is a schematic flowchart of a third display method of a head-mounted display device according to an embodiment of this application; 
         FIG. 7  is a schematic diagram of performing brightness grayscale adjustment on an image displayed by a left-eye display system in the embodiment shown in  FIG. 6 ; 
         FIG. 8  is a schematic flowchart of a fourth display method of a head-mounted display device according to an embodiment of this application; 
         FIG. 9  is a schematic structural diagram of a first head-mounted display device according to an embodiment of this application; 
         FIG. 10  is a schematic structural diagram of a second head-mounted display device according to an embodiment of this application; 
         FIG. 11A  is a schematic structural diagram of a third head-mounted display device according to an embodiment of this application; 
         FIG. 11B  is a schematic structural diagram of a fourth head-mounted display device according to an embodiment of this application; 
         FIG. 12  is a schematic flowchart of a fifth display method of a head-mounted display device according to an embodiment of this application; and 
         FIG. 13  is a schematic structural diagram of an embodiment of a head-mounted display device according to an embodiment of this application. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     To better understand the technical solutions of this application, the following describes the embodiments of this application in detail with reference to the accompanying drawings. 
     It should be clear that the described embodiments are merely a part rather than all of the embodiments of this application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of this application without creative efforts shall fall within the protection scope of this application. 
     A head-mounted display device provided in the embodiments of this application is a display device that magnifies, by using a group of optical systems, an image that is displayed on an ultra-micro display, projects the image (that is, a image) on a retina, and then presents a large-screen image to a user&#39;s eyes. The head-mounted display device may be a VR head-mounted display device, an AR head-mounted display device, or a display that may appear in the future and that presents another display effect. However, this does not affect implementation of the technical solutions described in the embodiments of this application. 
       FIG. 1  is a schematic flowchart of a first display method of a head-mounted display device according to an embodiment of this application. 
     Refer to  FIG. 1 . The display method includes the following steps. 
     Step  11 : Determine a current display mode in response to that the head-mounted display device enables a low power consumption display mode. 
     Step  12 : Determine a switching time interval based on the current display mode. 
     Step  13 : Control a left-eye display system to display an image and control a right-eye display system to be turned off. 
     Step  14 : In response to that display duration of the left-eye display system reaches first preset duration, turn off the left-eye display system and maintain an off state of the right-eye display system. 
     Step  15 : In response to that an off state of the left-eye display system lasts for the switching time interval, control the right-eye display system to display the image and maintain the off state of the left-eye display system. 
     Each step in the display method in this embodiment is performed by a display control unit of the head-mounted display device, where the head-mounted display device includes the display control unit, the left-eye display system, and the right-eye display system. It should be noted that, in actual application, the display control unit, the left-eye display system, and the right-eye display system in the head-mounted display device may be named by using other names. The naming in this embodiment is merely intended to reflect a function of each component of the head-mounted display device, but is not a limitation on the technical solutions of this application. 
     In the technical solutions of this application, the low power consumption display mode is added on a basis of a display mode that is of an existing head-mounted display device and in which a left-eye display system and a right-eye display system display an image (that is, a normal display mode). A method used by the display control unit to control the left-eye display system and the right-eye display system when the head-mounted display device enables the low power consumption display mode is described in this embodiment. 
     As described in step  11 , the current display mode is determined in response to that the head-mounted display device enables the low power consumption display mode. 
     Specifically, the display control unit of the head-mounted display device may determine the current display mode based on current display content. In actual application, the head-mounted display device stores a plurality of different pieces of display content, and each piece of display content is corresponding to one display mode. For example, different pieces of display content and their corresponding display modes may be distinguished by using different label information, where the label information may be included in a header file of a display source. By using the header file of the display source, whether display content is two-dimensional display content or three-dimensional display content is identified, and then the current display mode is determined. In actual application, the display control unit may alternatively determine the current display content and the current display mode in other manners, which are not listed herein one by one. 
     In this embodiment, the current display mode includes a two-dimensional display mode and a three-dimensional display mode. In the two-dimensional display mode, the left-eye display, system and the right-eye display system display a same image without parallax, for example, a high-definition image, a piece of text information, or an icon. In the three-dimensional display mode, the left-eye display system and the right-eye display system display two different images with parallax, so that a user can form a three-dimensional image in the brain. For example, a street view or a building is displayed. In another embodiment, the current display mode may alternatively be another display mode, for example, a four-dimensional display mode. 
     As described in step  12 , the switching time interval is determined based on the current display mode. 
     Specifically, in the low power consumption display mode, the display control unit controls the left-eye display system and the right-eye display system to alternately display the image. In this embodiment, “alternately” indicates that within a same time period, only one display system of the left-eye display system and the right-eye display system is in a working state, the other display system is in the off state, and the states of the two display systems are switched in turn. 
     In an ideal state, the left-eye display system and the right-eye display system can alternately display the image seamlessly. To be specific, when one display system is turned off, the other display system is turned on, in this case, the switching time interval is zero (that is, no switching time interval). However, in actual application, it is almost difficult to implement seamless alternation of the two display systems. In other words, in a process of switching between the left-eye display system and the right-eye display system to alternately display the image, when one display system is turned off, the other display system cannot be turned on. There is always a switching time interval. 
     To avoid affecting perception of the user as much as possible when the left-eye display system and the right-eye display system alternately display the image, the display control unit needs to determine corresponding switching time intervals based on different current display modes. Different current display modes are corresponding to different switching time intervals, and certainly may alternatively be corresponding to a same switching time interval. 
     In this embodiment, if the current display mode is the two-dimensional display mode, the switching time interval is a first switching time interval, or if the current display mode is the three-dimensional display mode, the switching time interval is a second switching time interval, where the second switching time interval is less than the first switching time interval. In the two-dimensional display mode, although only one display system displays the image within a same time period, the user can still perceive the image through both eyes by adjusting a position of the image. For example, when the left-eye display system and the right-eye display system display an image, that is, when there is the image in both a left-eye display field of view and a right-eye display field of view, an image perceived by the user may be a center position.  FIG. 2A  shows an image position perceived by a user when a left-eye display system and a right-eye display system display an image in the conventional technology. 
     However, due to parallax of binocular imaging, when only the left-eye display system displays the image, the user perceives that the displayed image is to the left compared with the image displayed by the two display systems.  FIG. 2B  shows an image position perceived by a user when only a left-eye display system displays an image. 
     When only the left-eye display system displays the image, the position of the image displayed by the left-eye display system may be adjusted to the right, to achieve a user perception effect the same as that achieved in binocular display, that is, the displayed image is in the center position. As shown in  FIG. 3 , an image  301  is an image output by the left-eye display system when both the left-eye display system and the right-eye display system display the image. When the left-eye display system displays the image, and the right-eye display system is turned off, if the left-eye display system still outputs the image  301 , an effect of the image perceived by the user is an image  302  due to the parallax of binocular imaging. That is, the user perceives that the displayed image is to the left compared with the image displayed by the left-eye display system and the right-eye display system. When the left-eye display system displays the image, and the right-eye display system is turned off, a position of the image displayed by the left-eye display system is adjusted to the right, for example, an image  303  output by the left-eye display system, to achieve a user perception effect the same as that achieved in binocular display, that is, the displayed image is in the center position. In this way, the position of the image perceived by the user is the center position, as shown by an image  304 . 
     Likewise, due to the parallax of binocular imaging, when only the right-eye display system displays the image, the user perceives that the displayed image is to the right compared with the image displayed by the left-eye display system and the right-eye display system. When the right-eye display system displays the image, and the left-eye display system is turned off, a position of the image displayed by the right-eye display system is adjusted to the left, to achieve a user perception effect the same as that achieved in binocular display, that is, the displayed image is in the center position. 
     However, in the three-dimensional display mode, human eyes need to perceive, through both eyes, two images with parallax to form a three-dimensional image. Therefore, the second switching time interval is less than the switching time interval in the two-dimensional display mode (that is, the first switching time interval); and a display effect in the three-dimensional display mode is not affected due to persistence of vision of the human eyes. 
     As described in step  13 , the left-eye display system is controlled to display the image, and the right-eye display system is controlled to be turned off. To be specific, when the left-eye display system displays the image, the right-eye display system does not display the image. 
     As described in step  14 , in response to that the display duration of the left-eye display system reaches the first preset duration, the left-eye display system is turned off, and the off state of the right-eye display system is maintained. 
     As described in step  15 , in response to that the off state of the left-eye display system lasts for the switching time interval, the right-eye display system is controlled to display the image, and the off state of the left-eye display system is maintained. To be specific, when the right-eye display system displays the image, the left-eye display system does not display the image. 
     In the descriptions of step  13  to step  15 , the display control unit first controls the left-eye display system to display the image (and controls the right-eye display system to be turned off), and turns off the left-eye display system after the left-eye display system displays the image for the first preset duration. Then, after the switching time interval, the display control unit controls the right-eye display system to display the image (and maintains turnoff of the left-eye display system). In this way, only one display system is in the working state within a same time period. 
     According to the solution provided in this embodiment, when the head-mounted display device enables the low power consumption display mode, the left-eye display system and the right-eye display system of the head-mounted display device alternately display a image (to be specific, the left-eye display system and the right-eye display system are switched in turn to display the image) instead of displaying the image. The switching time interval for the left-eye display system and the right-eye display system to alternately display the image is determined based on the current display mode. Different current display modes may be corresponding to different switching time intervals, or may be corresponding to a same switching time interval. Therefore, in the low power consumption display mode, only one display system (the left-eye display system or right-eye display system) displays the image within a same time period, and thus power consumption of the display systems of the head-mounted display device is reduced. 
       FIG. 4  is a schematic flowchart of a second display method of a head-mounted display device according to an embodiment of this application. On a basis of the embodiment shown in  FIG. 1 , this embodiment further includes the following steps. 
     Step  41 : In response to that display duration of the right-eye display system reaches second preset duration, turn off the right-eye display system and maintain the off state of the left-eye display system. 
     Step  42 : In response to that the off state of the right-eye display system lasts for the switching time interval, control the left-eye display system to display the image and maintain the off state of the right-eye display system. 
     A process in which the display control unit alternately controls the left-eye display system and the right-eye display system is described with reference to step  13  to step  15 , and step  41  and step  42 . The following describes the process in detail with reference to specific embodiments. 
     The following describes the steps in detail with reference to a schematic diagram, shown in  FIG. 5A , of controlling a left-eye display system and a right-eye display system to alternately display an image in a two-dimensional display mode. 
     Refer to  FIG. 5A . First, the display control unit controls the left-eye display system to be turned on, and at this point, the right-eye display system is in the off state. Then, the display control unit turns off the left-eye display system when the left-eye display system displays the image for the first preset duration. After the first switching time interval, the display control unit controls the right-eye display system to be turned on, and at this point, the left-eye display system is in the off state. In other words, within the first switching time interval (that is, a time period between turning off of the left-eye display system and turning on of the right-eye display system), both the left-eye display system and the right-eye display system are in the off state. Then, the display control unit turns off the right-eye display system when the right-eye display system displays the image for the second preset duration. After the first switching time interval, the display control unit further controls the left-eye display system to be turned on, and at this point, the right-eye display system is in the off state. In other words, within the first switching time interval (that is, a time period between turning off of the right-eye display system and turning on of the left-eye display system), both the left-eye display system and the right-eye display system are in the off state. 
     The display control unit controls the left-eye display system and the right-eye display system to alternately display the image according to the control method shown in  FIG. 5A , where the first preset duration and the second preset duration may be set in advance, for example, 30 seconds or one minute. In actual application, the first preset duration and the second preset duration that are set in advance may be the same or different. The first preset duration is set in advance to be equal to the second preset duration to make human eyes more adaptable to alternate switching between the left-eye display system and the right-eye display system for displaying a image. 
     It should be noted that, as shown in  FIG. 5A , the display control unit first controls the left-eye display system to be turned on and the right-eye display system to be in the off state, and then alternately switches between the left-eye display system and the right-eye display system based on the first switching time interval. In actual application, the display control unit may alternatively first control the right-eye display system to be turned on and the left-eye display system to be in the off state, and then perform cyclic and alternate switching between the left-eye display system and the right-eye display system based on the first switching time interval. 
     The following describes the steps in detail with reference to a schematic diagram, shown in  FIG. 5B , of controlling a left-eye display system and a right-eye display system to alternately display an image in a three-dimensional display mode. 
     Refer to  FIG. 5B . First, the display control unit controls the left-eye display system to be turned on, and at this point, the right-eye display system is in the off state. Then, the display control unit turns off the left-eye display system when the left-eye display system displays the image for the second preset duration. After the second switching time interval, the display control unit controls the right-eye display system to be turned on, and at this point, the left-eye display system is in the off state. In other words, within the second switching time interval (that is, a time period between turning off of the left-eye display system and turning on of the right-eye display system), both the left-eye display system and the right-eye display system are in the off state. Then, the display control unit turns off the right-eye display system when the right-eye display system displays a image for the second preset duration. After the second switching time interval, the display control unit further controls the left-eye display system to be turned on, and at this point, the right-eye display system is in the off state. In other words, within the second switching time interval (that is, a time period between turning off of the right-eye display system and turning on of the left-eye display system), both the left-eye display system and the right-eye display system are in the off state. 
     The display control unit controls the left-eye display system and the right-eye display system to alternately display the image according to the control method shown in  FIG. 5B . 
     In the three-dimensional display mode, on the one hand, human eyes need to perceive, through both eyes, two images with parallax to form a three-dimensional image. Therefore, the second switching time interval is less than the switching time interval in the two-dimensional display mode (that is, the first switching time interval); and a display effect in the three-dimensional display mode is not affected due to persistence of vision of the human eyes. On the other hand, the two images with parallax are two images with parallax based on a same piece of display content, and therefore display duration of a monocular display system (the left-eye display system or right-eye display system) is also less than display duration of a monocular display system (the left-eye display system or right-eye display system) in the two-dimensional display mode (that is, the second preset duration is less than the first preset duration). 
     In this embodiment, the first preset duration of the left-eye display system and the second preset duration of the right-eye display system are determined based on a preset quantity of frames of left-eye display and a preset quantity of frames of right-eye display respectively. Specifically, the quantity of frames of left-eye display and the quantity of frames of right-eye display may be set in advance, for example, one frame or two frames; and frame rates (that is, a quantity of frames displayed per second) at which the left-eye display system and the right-eye display system display an image may be set in advance. In this case, the first preset duration may be determined based on the quantity of flumes of left-eye display and the frame rate that are of the left-eye display system, and the second preset duration may be determined based on the quantity of frames of right-eye display and the frame rate that are of the right-eye display system. In actual application, the quantity of frames of left-eye display and the quantity of frames of right-eye display that are set in advance may be the same or different, and the frame rate at which the left-eye display system displays an image and the frame rate at which the right-eye display system displays an image may be the same or different. To enable the human eyes to perceive the image displayed by the left-eye display system and the image displayed by the right-eye display system, where the two images are displayed with parallax, so that a three-dimensional image is better formed in the brain, the quantity of frames of left-eye display is set in advance to be equal to the quantity of frames of right-eye display, and the frame rate at which the left-eye display system displays an image is the same as the frame rate at which the right-eye display system displays an image. In other words, the first preset duration is equal to the second preset duration. 
     It should be noted that, as shown in  FIG. 5B , the display control unit first controls the left-eye display system to be turned on and the right-eye display system to be in the off state, and then alternately switches between the left-eye display system and the right-eye display system based on the second switching time interval. In actual application, the display control unit may alternatively first control the right-eye display system to be turned on and the left-eye display system to be in the off state, and then alternately switch between the left-eye display system and the right-eye display system based on the second switching time interval. 
       FIG. 6  is a schematic flowchart of a third display method of a head-mounted display device according to an embodiment of this application. Refer to  FIG. 6 . On a basis of the embodiment shown in  FIG. 1 , this embodiment further includes the following step. 
     Step  61 : If the current display mode is the two-dimensional display mode, when the left-eye display system displays the image, adjust a brightness grayscale of the image displayed by the left-eye display system, or when the right-eye display system displays the image, adjust a brightness grayscale of the image displayed by the right-eye display system. 
     This embodiment is based on the embodiment shown in  FIG. 1 . Although only one display system displays the image within a same time period, by adjusting a position of the image (for example, when the left-eye display system displays the image, compared with the position of the image simultaneously displayed by the left-eye and right-eye display systems, the position of the image may be adjusted to the right), the user can still perceive the image through both eyes, and the image is centered. This is close to an effect of simultaneously displaying the image by the left-eye and right-eye display systems. When only one display system displays the image, in addition to the foregoing problem that the image perceived by the user is not in the center position, there is also a problem of uneven brightness. When only the left-eye display system displays the image, the user perceives that, compared with brightness of the image simultaneously displayed by the left-eye and right-eye display systems, brightness of a left side of the image is higher than brightness of a right side of the image, and the brightness of the right side of the image is comparatively low. To enable the user to perceive an image with uniform brightness, in this embodiment of this application, a brightness grayscale of the image displayed by a monocular display system is adjusted. For example, when a display system renders an image, a preset brightness grayscale compensation value is added to a brightness grayscale of a pixel in the original image, or a preset brightness grayscale compensation value is added to a brightness grayscale of a column pixel in the original image, so that the user perceives the image with uniform brightness. 
     As shown in  FIG. 7 , an image  701  is an image output by the left-eye display system when both the left-eye display system and the right-eye display system display the image. When the left-eye display system displays the image, and the right-eye display system is turned off, if the left-eye display system still outputs the image  701 , the user perceives that the displayed image is to the left compared with the image simultaneously displayed by the left-eye display system and the right-eye display system in addition, image brightness perceived by the user is uneven. As shown by an image  702 , the user perceives that brightness of a left side of the image is higher than brightness of a right side of the image. When the left-eye display system displays the image, and the right-eye display system is turned off, to achieve a user perception effect the same as that achieved in binocular display, a position of the image displayed by the left-eye display system is adjusted to the right, to enable the user to perceive that the image is in a center position; and in addition, a preset brightness grayscale compensation value is added to a brightness grayscale of a pixel in the original image, so that the user perceives the image with uniform brightness. An image  703  is an image obtained after the position of the image displayed by the left-eye display system is adjusted to the right, and brightness grayscale compensation is performed on the brightness grayscale of the pixel in the image. When the left-eye display system displays the image, and the right-eye display system is turned off, the left-eye display system outputs the image  703 , so that an image perceived by the user is an image  704 . To be specific, the image is in the center position, and image brightness is uniform. 
     Different from the embodiment shown in  FIG. 1 , in this embodiment, when it is determined that the current display mode is the two-dimensional display mode, before step  13  is performed (that is, control a left-eye display system to display an image and control a right-eye display system to be turned oft), step  61  is performed: When the left-eye display system displays the image, adjust a brightness grayscale of the image displayed by the left-eye display system, or when the right-eye display system displays the image, adjust a brightness grayscale of the image displayed by the right-eye display system. 
     As described above, when only one display system displays an image, the user may perceive, through both eyes, a brightness grayscale difference in the displayed image on the whole, and different users have different perception of the brightness grayscale difference in the image. The brightness grayscale indicates a brightness level. For each image frame, a display source (that is, a light source) behind the image frame may present different brightness levels. Grayscales represent different brightness levels from a darkest level to a brightest level. More levels indicate that a more detailed image can be presented. According to a common user&#39;s perception of image brightness, when only the left-eye display system displays an image, the user&#39;s both eyes perceive that brightness of the image gradually decreases from left to right on the whole; or when only the right-eye display system displays an image, the user&#39;s both eyes perceive that brightness of the image gradually decreases from right to left on the whole. 
     In this embodiment, for each image frame displayed by the left-eye display system, the adjusting a brightness grayscale of the image displayed by the left-eye display system includes: adding a preset brightness grayscale compensation value to a brightness grayscale of a pixel in each image frame displayed by the left-eye display system, or adding a preset brightness grayscale compensation value to a brightness grayscale of a column pixel in the original image, so that the user perceives the image with uniform brightness. In other words, a region perceived to be comparatively bright by the user is darkened in advance, and a region perceived to be comparatively dark by the user is brightened in advance. The user perceives, through both eyes, that brightness of each image frame displayed by the left-eye display system gradually decreases from left to right on the whole. Therefore, a trend of adjusting the brightness grayscale is a gradual change from darkening to brightening from left to right. 
     For each image frame displayed by the right-eye display system, the adjusting a brightness grayscale of the image displayed by the right-eye display system includes: adding a preset brightness grayscale compensation value to a brightness grayscale of a pixel in each image frame displayed by the right-eye display system, or adding a preset brightness grayscale compensation value to a brightness grayscale of a column pixel in the original image, so that the user perceives the image with uniform brightness. In other words, a region perceived to be comparatively bright by the user is darkened in advance, and a region perceived to be comparatively dark by the user is brightened in advance. The user perceives, through both eyes, that brightness of each image frame displayed by the right-eye display system gradually increases from left to right on the whole. Therefore, a trend of adjusting the brightness grayscale is a gradual change from brightening to darkening from left to right. 
     In actual application, brightness grayscale compensation is separately performed on a display source of the left-eye display system and a display source of the right-eye display system by using a software policy, to adjust the brightness grayscale of the image displayed by the left-eye display system or the right-eye display system. 
       FIG. 8  is a schematic flowchart of a fourth display method of a head-mounted display device according to an embodiment of this application. 
     Refer to  FIG. 8 . The display method includes the following steps. 
     Step  80 : Enable the head-mounted display device. 
     Step  81 : After the head-mounted display device is enabled, based on an environmental parameter or a user-input instruction, determine that the head-mounted display device enables a low power consumption display mode. 
     Step  82 : If the environmental parameter of the head-mounted display device meets a condition for triggering the low power consumption mode, or the received user-input instruction is to switch to the low power consumption display mode, determine that the head-mounted display device enables the low power consumption display mode. 
     Step  83 : If the environmental parameter of the head-mounted display device meets a condition for triggering a normal display mode, or the received user-input instruction is to switch to a normal display mode, determine that the head-mounted display device enables the normal display mode. 
     Step  84 : When the head-mounted display device enables the normal display mode, control a left-eye display system and a right-eye display system to simultaneously display an image. 
     As described above, in the technical solutions of this application, the low power consumption display mode is added on a basis of a display mode that is of an existing head-mounted display device and in which a image is simultaneously displayed to both eyes (that is, the normal display mode). Therefore, after the head-mounted display device is enabled, whether to enter the normal display mode or the low power consumption display mode needs to be determined. The solution provided in this embodiment is a specific implementation in which a display control unit determines a display mode that is used for entering. 
     In this embodiment, after the head-mounted display device is enabled, based on the environmental parameter or the user-input instruction, it is determined that the head-mounted display device enables the low power consumption display mode (that is, step  81 ). 
     As described in step  82 , if a current environmental parameter of the head-mounted display device meets the condition for triggering the low power consumption display mode, or the received user-input instruction is to switch to the low power consumption display mode, it is determined that the head-mounted display device enables the low power consumption display, mode. 
     Specifically, in this embodiment, the head-mounted display device may automatically determine to enter the normal display mode or the low power consumption display mode based on a result of comparing the environmental parameter with a critical value. The environmental parameter may be a temperature (to be specific, a current temperature of the head-mounted display device) or a battery level (to be specific, current remaining power of the head-mounted display device). If the current temperature of the head-mounted display device is higher than a critical temperature, or the current remaining power of the head-mounted display device is lower than critical power, the low power consumption display mode is automatically enabled, where the critical temperature and the critical power (that is, the critical value) may be set in advance. 
     The head-mounted display device may alternatively determine, based on the user-input instruction, a display mode that is used for entering. When the user-input instruction for switching to the low power consumption display mode is received, it is determined that the head-mounted display device enables the low power consumption display mode. 
     When the head-mounted display device enables the low power consumption mode, the display control unit controls the left-eye display system and the right-eye display system to alternately display the image according to the specific embodiments shown in  FIG. 1  to  FIG. 7 . 
     As shown in step  83 , if the environmental parameter of the head-mounted display device meets the condition for triggering the normal display mode, or the received user-input instruction is to switch to the normal display mode, it is determined that the head-mounted display device enables the normal display mode. Specifically, if the current temperature of the head-mounted display device is higher than the critical temperature or the current remaining power of the head-mounted display device is higher than the critical power, the normal display mode is automatically enabled. 
     As described in step  84 , when the head-mounted display device enables the normal display mode, the left-eye display system and the right-eye display system are controlled to simultaneously display the image. 
     Based on the foregoing method embodiments, an embodiment of the embodiment of the invention further provides a head-mounted display device, including a display control unit, a left-eye display system, and a right-eye display system. The display control unit is configured to: determine a current display mode in response to that the head-mounted display device enables a low power consumption display mode; determine a switching time interval based on the current display mode; control the left-eye display system to display an image and control the right-eye display system to be turned off; in response to that display duration of the left-eye display system reaches first preset duration, turn off the left-eye display system and maintain an off state of the right-eye display system; and in response to that an off state of the left-eye display system lasts for the switching time interval, control the right-eye display system to display the image and maintain the off state of the left-eye display system. 
     The display control unit is further configured to: in response to that display duration of the right-eye display system reaches second preset duration, turn off the right-eye display system and maintain the off state of the left-eye display system; and in response to that the off state of the right-eye display system lasts for the switching time interval, control the left-eye display system to display the image and maintain the off state of the right-eye display system. The first preset duration is equal to the second preset duration. 
     The display control unit is further configured to: if the current display mode is a two-dimensional display mode, determine that the switching time interval is a first switching time interval, or if the current display mode is a three-dimensional display mode, determine that the switching time interval is a second switching time interval, where the second switching time interval is less than the first switching time interval. 
     The display control unit is further configured to: if the current display mode is the two-dimensional display mode, when the left-eye display system displays the image, adjust a brightness grayscale of the image displayed by the left-eye display system, or when the right-eye display system displays the image; adjust a brightness grayscale of the image displayed by the right-eye display system. The display control unit is further configured to: determine the first preset duration based on a preset quantity of frames of left-eye display; and determine the second preset duration based on a preset quantity of frames of right-eye display, where the quantity of frames of left-eye display is equal to the quantity of frames of right-eye display. 
     The display control unit is further configured to: based on an environmental parameter or a user-input instruction, determine that the head-mounted display device enables the low power consumption display mode. The environmental parameter includes a temperature of the head-mounted display device or a battery level of the head-mounted display device. 
       FIG. 9  is a schematic structural diagram of a first head-mounted display device according to an embodiment of this application. 
     Refer to  FIG. 9 . The head-mounted display device  7  includes a display control unit  71 , a left-eye display system  72 , and a right-eye display system  73 . The display control unit  71  is configured to: determine a current display mode in response to that the head-mounted display device  7  enables a low power consumption display mode; determine a switching time interval based on the current display mode; control the left-eye display system  72  to display an image and control the right-eye display system  73  to be turned off; in response to that display duration of the left-eye display system  72  reaches first preset duration, turn off the left-eye display system  72  and maintain an off state of the right-eye display system  73 ; and in response to that an off state of the left-eye display system  72  lasts for the switching time interval, control the right-eye display system  73  to display the image and maintain the off state of the left-eye display system  72 . 
     The display control unit  71  is further configured to: in response to that display duration of the right-eye display system  73  reaches second preset duration, turn off the right-eye display system  73  and maintain the off state of the left-eye display system  72 ; and in response to that the off state of the right-eye display system  73  lasts for the switching time interval, control the left-eye display system  72  to display the image and maintain the off state of the right-eye display system  73 . 
     Specifically, the left-eye display system  72  includes a first optical system  721 , a first display source  722 , and a first display driver module  723 . The first optical system  721  is connected to the first display source  722 , and the first display driver module  723  is connected to the first display source  722 . The first display driver module  723  is configured to drive the left-eye display system  72 , the first optical system  721  is configured to generate the image, and the first display source  722  is configured to control a brightness grayscale of the image. 
     The right-eye display system  73  includes a second optical system  731 , a second display source  732 , and a second display driver module  733 . The second optical system  731  is connected to the second display source  732 , and the second display driver module  733  is connected to the second display source  732 . The second display driver module  733  is configured to drive the right-eye display system  73 , the second optical system  731  is configured to generate the image, and the second display source  732  is configured to control a brightness grayscale of the image. 
     The display control unit  71  controls turning on and turning off of the first display source  722  and the first display driver module  723  in the left-eye display system  72  by using a left-eye display enable signal. The display control unit  71  controls turning on and turning off of the second display source  732  and the second display driver module  733  in the right-eye display system  73  by using a right-eye display enable signal. The left-eye display enable signal and the right-eye display enable signal may be a high-level signal, a low-level signal, a specific coded signal, or the like. For example, a high-level signal and a low-level signal are used as an example. If the enable signal is the high-level signal, the display source and the display driver module in the display system are controlled to be turned on; or if the enable signal is the low-level signal, the display source and the display driver module in the display system are controlled to be turned off. 
       FIG. 10  is a schematic structural diagram of a second head-mounted display device according to an embodiment of this application. 
     Refer to  FIG. 10 . The head-mounted display device  8  includes a display control unit  81 , a left-eye display system  82 , and a right-eye display system  83 . The display control unit  81  is configured to: determine a current display mode in response to that the head-mounted display device  8  enables a low power consumption display mode; determine a switching time interval based on the current display mode; control the left-eye display system  82  to display an image and control the right-eye display system  83  to be turned off; in response to that display duration of the left-eye display system  82  reaches first preset duration, turn off the left-eye display system  82  and maintain an off state of the right-eye display system  83 ; and in response to that an off state of the left-eye display system  82  lasts for the switching time interval, control the right-eye display system  83  to display the image and maintain the off state of the left-eye display system  82 . 
     The display control unit  81  is further configured to: in response to that display duration of the right-eye display system  83  reaches second preset duration, turn off the right-eye display system  83  and maintain the off state of the left-eye display system  82 ; and in response to that the off state of the right-eye display system  83  lasts for the switching time interval, control the left-eye display system  82  to display the image and maintain the off state of the right-eye display system  83 . 
     Different from the embodiment shown in  FIG. 9 , in this embodiment, the head-mounted display device  8  further includes a first load switch  84  and a second load switch  85 . The first load switch  84  is disposed between the display control unit  81  and the left-eye display system  82 . The display control unit  81  controls a working state of the first load switch  84  by using a first power-on/power-off control signal, to control turning on and turning off of the left-eye display system  82 . The second load switch  85  is disposed between the display control unit  81  and the right-eye display system  83 . The display control unit  81  controls a working state of the second load switch  85  by using a second power-on/power-off control signal, to control turning on and turning off of the right-eye display system  83 . Similar to the left-eye display enable signal and the right-eye display enable signal in  FIG. 7 , the first power-on/power-off control signal and the second power-on/power-off control signal may also be a high-level signal, a low-level signal, a specific coded signal, or the like. Details are not described herein again. 
       FIG. 11A  is a schematic structural diagram of a third head-mounted display device according to an embodiment of this application. Refer to  FIG. 11A . The head-mounted display device  9   a  includes a display control unit  91   a , a left-eye display system  92   a , and a right-eye display system  93   a . The display control unit  91   a  is configured to: determine a current display mode in response to that the head-mounted display device  9   a  enables a low power consumption display mode; determine a switching time interval based on the current display mode; control the left-eye display system  92   a  to display an image and control the right-eye display system  93   a  to be turned off; in response to that display duration of the left-eye display system  92   a  reaches first preset duration, turn off the left-eye display system  92   a  and maintain an off state of the right-eye display system  93   a : and in response to that an off state of the left-eye display system  92   a  lasts for the switching time interval, control the right-eye display system  93   a  to display the image and maintain the off state of the left-eye display system  92   a.    
     The display control unit  91   a  is further configured to: in response to that display duration of the right-eye display system  93   a  reaches second preset duration, turn off the right-eye display system  93   a  and maintain the off state of the left-eye display system  92   a , and in response to that the off state of the right-eye display system  93   a  lasts for the switching time interval, control the left-eye display system  92   a  to display the image and maintain the off state of the right-eye display system  93   a.    
     Different from the embodiments shown in  FIG. 9  and  FIG. 10 , in this embodiment, the head-mounted display device  9   a  further includes a first load switch  94   a , a second load switch  95   a , and a first inverter  96   a . The first load switch  94   a  is connected between the left-eye display system  92   a  and the first inverter  96   a . The second load switch  95   a  is connected between the right-eye display system  93   a  and the display control unit  91   a . The display control unit  91   a  controls the second load switch  95   a  by using a third power-on/power-off control signal, to control turning on and turning off of the right-eye display system  93   a , and the third power-on/power-off control signal controls the first load switch  94   a  by using the third power-on/power-off control signal that has passed through the first inverter  96   a , to control turning on and turning off of the left-eye display system  92   a . Similar to the first power-on/power-off control signal or the second power-on/power-off control signal in the embodiment shown in  FIG. 10 , the third power-on/power-off control signal may also be a high-level signal, a low-level signal, a specific coded signal, or the like. 
       FIG. 11B  is a schematic structural diagram of a fourth head-mounted display device according to an embodiment of this application. Refer to  FIG. 11B . The head-mounted display device  9   b  includes a display control unit  91   b , a left-eye display system  92   b , and a right-eye display system  93   b . The display control unit  91   b  is configured to: determine a current display mode in response to that the head-mounted display device  9   b  enables a low power consumption display mode; determine a switching time interval based on the current display mode; control the left-eye display system  92   b  to display an image and control the right-eye display system  93   b  to be turned off; in response to that display duration of the left-eye display system  92   b  reaches first preset duration, turn off the left-eye display system  92   b  and maintain an off state of the right-eye display system  93   b ; and in response to that an off state of the left-eye display system  92   b  lasts for the switching time interval, control the right-eye display system  93   b  to display the image and maintain the off state of the left-eye display system  92   b.    
     The display control unit  91   h  is further configured to: in response to that display duration of the right-eye display system  93   b  reaches second preset duration, turn off the right-eye display system  93   b  and maintain the off state of the left-eye display system  92   b ; and in response to that the off state of the right-eye display system  93   h  lasts for the switching time interval, control the left-eye display system  92   h  to display the image and maintain the off state of the right-eye display system  93   b.    
     In this embodiment, the head-mounted display device  9   b  further includes a first load switch  94   b , a second load switch  95   b , and a second inverter  96   b . Different from the embodiment shown in  FIG. 11A , in this embodiment, the second load switch  95   b  is connected between the right-eye display system  93   b  and the second inverter  96   h , and the first load switch  94   b  is connected between the left-eye display system  92   b  and the display control unit  91   b . The display control unit  91   b  controls the first load switch  94   b  by using a fourth power-on/power-off control signal, to control turning on and turning off of the left-eye display system  92   b , and the fourth power-on/power-off control signal controls the second load switch  95   b  after passing through the second inverter  96   b , to control turning on and turning off of the right-eye display system  93   b . Similar to the third power-on/power-off control signal in the embodiment shown in  FIG. 11A , the fourth power-on/power-off control signal may also be a high-level signal, a low-level signal, a specific coded signal, or the like. 
     In the embodiments shown in  FIG. 9 ,  FIG. 10 ,  FIG. 11A , and  FIG. 11B , the display control unit of the head-mounted display device controls the left-eye display system and the right-eye display system in different control manners. For example, the display control a nit directly controls turning on and turning off of the two display systems by using the enable signal (the embodiment shown in  FIG. 9 ). For another example, the display control unit controls the two load switches by using two power-on/power-off control signals, and further controls turning on and turning off of the two display systems separately (the embodiment shown in  FIG. 10 ). For still another example, the display control unit controls one load switch by using one power-on/power-off control signal, and then controls turning on and turning off of one of the display systems; and controls the other load switch by using the power-on/power off signal on which the inverter has performed reverse processing, and then controls turning on and turning off of the other display system. 
     It should be noted that, in the embodiments shown in  FIG. 11A  and  FIG. 11B , the display control unit outputs only one power-on/power-off control signal to control one load switch, and the inverter performs reverse processing on the power-on/power-off control signal to control the other load switch. Therefore, a time interval for alternate switching between the two display systems depends on a delay in reverse processing performed by the inverter on one power-on/power-off control signal. In actual application, it is difficult to achieve a zero delay in reverse processing performed by the inverter on a power-on/power-off control signal. 
       FIG. 12  is a schematic flowchart of a fifth display method of a head-mounted display device according to an embodiment of this application. Refer to  FIG. 12 . The display method includes the following steps. 
     Step  100 : Enable the head-mounted display device. 
     Step  101 : Determine whether to enable a low power consumption display mode. If a determining result is no, perform step  102  and step  103 ; or if a determining result is yes, perform step  104 . 
     Step  102 : Enable a normal display mode, to simultaneously display with the left-eye display system and a right-eye display system. 
     Step  103 : Determine whether to switch the display mode. If a determining result is no, perform step  111 ; or if a determining result is yes, perform step  101 . 
     Step  104 : Determine a current display mode. If the current display mode is a two-dimensional display mode, perform step  105 ; or if the current display mode is a three-dimensional display mode, perform step  106 . 
     Step  105 : Based on a first switching time interval, control a left-eye display system and a right-eye display system to alternately display an image. Perform step  107  or step  109  after step  105 . 
     Step  106 : Based on a second switching time interval, control a left-eye display system and a right-eye display system to alternately display an image. Perform step  108  and step  110  after step  106 . 
     Step  107 : If the current display mode is switched, perform step  104 . 
     Step  108 : If the current display mode is switched, perform step  104 . 
     Step  109 : Determine whether the display mode is switched. If a determining result is no, perform step  111 ; or if a determining result is yes, perform step  101 . 
     Step  110 : Determine whether the display mode is switched. If a determining result is no, perform step  111 ; or if a determining result is yes, perform step  101 . 
     Step  111 : Turn off the two display systems. 
       FIG. 13  is a schematic structural diagram of an embodiment of a head-mounted display device according to an embodiment of this application. 
     The head-mounted display device includes a display control unit  12 , a left-eye display system  11   a , and a right-eye display system  11   b . The display control unit  12  may include a memory, a processor, and a computer program that is stored in the memory and that can be run in the processor. When the processor executes the computer program, the display method provided in the embodiments of this application can be implemented. 
     The device may be a server, for example, a cloud server, or may be an electronic device, for example, a smart electronic device such as a smartphone, a smartwatch, or a tablet computer. A specific form of the computer device is not limited in this embodiment. 
       FIG. 13  is a block diagram of an example of the display control unit  12  suitable for implementing the embodiment of this application. The display control unit  12  shown in  FIG. 13  is merely an example, and should not impose any limitation on a function and a use scope of the embodiment of this application. 
     As shown in  FIG. 13 , the display control unit  12  is represented in a form of a general-purpose computing device. Components of the display control unit  12  may include but are not limited to: one or more processors or processing units  16 , a system memory  28 , and a bus  18  connecting different system components (including the system memory  28  and the processing unit  16 ). 
     The bus  18  represents one or more of several types of bus structures, including a memory bus or a memory controller, a peripheral bus, a graphics acceleration port, a processor, or a local bus using any bus structure of various bus structures. For example, these architectures include but are not limited to an industry standard architecture (Industry Standard Architecture, ISA for short hereinafter) bus, a micro channel architecture (Micro Channel Architecture, MAC for short hereinafter) bus, an enhanced ISA bus, a video electronics standards association (Video Electronics Standards Association, VESA for short hereinafter) local bus, and a peripheral component interconnection (Peripheral Component interconnection, PCI for short hereinafter) bus. 
     The display control unit  12  typically includes a variety of computer system readable media. These media may be any usable media that can be accessed by the display control unit  12 , including volatile and non-volatile media, and removable and non-removable media. 
     The system memory  28  may include a computer system readable medium in a form of a volatile memory, such as a random access memory (Random Access Memory, RAM for short hereinafter)  41  and/or a cache memory  42 . The display control unit  12  may further include other removable/non-removable, and volatile/non-volatile computer system storage media. For example only, a storage system  44  may be configured to read data from and write data to a non-removable and non-volatile magnetic medium (not shown in  FIG. 11  and commonly referred to as a “hard disk drive”). Although not shown in  FIG. 11 , a disk drive configured to read data from and write data to a removable and non-volatile disk (for example, a “floppy disk”) may be provided, and an optical disc drive configured to read data from and write data to a removable and non-volatile optical disc (for example, a compact disc read-only memory (Compact Disc Read Only Memory, CD-ROM for short hereinafter), a digital versatile disc read-only memory (Digital Versatile Disc Read Only Memory, DVD-ROM for short hereinafter), or another optical medium) may be provided. In these cases, each drive may be connected to the bus  18  through one or more data medium interfaces. The memory  28  may include at least one program product, the program product includes a se of (for example, at least one) program modules, and these program modules are configured to perform functions provided in the embodiments of this application. 
     A program/utility  40  that includes a set of (at least one) program modules  52  may be stored in, for example, the memory  28 . Such a program module  52  includes but is not limited to an operating system, one or more application programs, another program module, and program data. Each of or a specific combination of these examples may include implementation of a network environment. The program module  52  usually performs a function and/or a method in the embodiments described in this application. 
     The display control unit  12  may communicate with one or more external devices  14  (for example, a keyboard, a pointing device, and a display  24 ), and may further communicate with one or more devices that enable a user to interact with the display control unit  12 , and/or communicate with any device (for example, a network adapter or a modern) that enables the display control unit  12  to communicate with one or more other computing devices. Such communication may be performed through an input/output (I/O) interface  22 . In addition, the display control unit  12  may further communicate with one or more networks (for example, a local area network (Local Area Network. LAN for short hereinafter), a wide area network (Wide Area Network, WAN for short hereinafter), and/or a public network, for example, the internee) through a network adapter  20 . As shown in  FIG. 11 , the network adapter  20  communicates with another module of the display control unit  12  through the bus  18 . It should be understood that, although not shown in  FIG. 11 , other hardware and/or software modules may be used in combination with the display control unit  12 , including but not limited to microcode, a device drive, a redundant processing unit, an external disk drive array, a RAID system, a tape drive, and a data backup storage system. 
     The processing unit  16  runs a program stored in the system memory  28  to execute various functional applications and data processing, for example, implementing the head-mounted display method provided in the embodiments of this application. 
     An embodiment of this application further provides a non-temporary computer readable storage medium that stores a computer program. When the computer program is executed by a processor, the head-mounted display method provided in the embodiments of this application can be implemented. 
     Any combination of one or more computer readable media may be used as the non-temporary computer readable storage medium. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. For example, the computer readable storage medium may be but is not limited to an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof more specific examples (non-exhaustive list) of the computer readable storage medium include: an electrical connection including one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (Read Only Memory, ROM for short hereinafter), an erasable programmable read-only memory (Erasable Programmable Read Only Memory, EPROM for short hereinafter) or a flash memory, an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In this embodiment of this invention, the computer readable storage medium may be any tangible medium including or storing a program that may be used by an instruction execution system, apparatus, or device, or be used in combination with an instruction execution system, apparatus, or device. 
     A computer readable signal medium may include a data signal propagated in a baseband or propagated as part of a carrier, where the data signal carries computer readable program code. Such a propagated data signal may take a variety of forms, including but not limited to an electromagnetic signal, an optical signal, or any suitable combination thereof. The computer readable signal medium may alternatively be any computer readable medium other than the computer readable storage medium. The computer readable medium may send, propagate, or transmit the program used by the instruction execution system, apparatus, or device, or used in combination with the instruction execution system, apparatus, or device. 
     Program code included in the computer readable medium may be transmitted by using any suitable medium, including but not limited to wireless, a wire, an optical cable, and RF, or any suitable combination thereof. 
     Computer program code for performing the operations in this application may be written in one or more programming languages, or a combination thereof. The programming languages include an object-oriented programming language, such as Java, Smalltalk, and C++, and also include a conventional procedural programming language, such as a “C” language or a similar programming language. The program code may be executed entirely on the user&#39;s computer, partially on the user&#39;s computer; as a separate software package, partially on the user&#39;s computer, partially on the remote computer, or entirely on the remote computer or server. In a case in which a remote computer is used, the remote computer may be connected to a user computer through any type of network, including a local area network (Local Area Network, LAN for short hereinafter) or a wide area network (Wide Area Network, WAN for short hereinafter), or may be connected to an external computer (for example, connected to the external computer through the internet provided by an internet service provider). 
     In conclusion, by using the head-mounted display device and the display method thereof that are provided in the technical solutions of this application, when the head-mounted display device enables the low power consumption display mode, the left-eye and right-eye display systems of the head-mounted display device alternately display an image (to be specific, the left-eye display system and the right-eye display system are switched in turn to display the image) instead of simultaneously displaying the image. The switching time interval for the left-eye display system and the right-eye display system to alternately display the image is determined based on the current display mode. Different current display modes may be corresponding to different switching time intervals, or may be corresponding to a same switching time interval. Therefore, in the low power consumption display mode, only one display system (the left-eye display system or right-eye display system) displays the image within a same time period, and thus power consumption of the display systems of the head-mounted display device is reduced. 
     The foregoing descriptions are merely example embodiments of this application, but are not intended to limit this application. Any modification, equivalent replacement, or improvement made without departing from the principle of this application should fall within the protection scope of this application.