Abstract:
An object of the present invention is to provide a head-mounted display apparatus capable of radio communication with a computer unit at low cost and in compact structure, and a system therewith. For accomplishing the object, a computer unit and a head-mounted display of the present invention have first and second radio transceivers capable of communication with each other. Further, image data to be displayed on a display body is generated by a graphics processing unit of the computer unit and is supplied in the form of a radio signal to the head-mounted display. Since the graphics processing unit generates only the image data of a changed portion in the display area, it becomes feasible to reduce volumes of the image data to be transmitted and use inexpensive, compact radio transceivers.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a head-mounted display apparatus, an information processing apparatus using a head-mounted display as an external display device, and an information processing system comprised thereof.  
           [0003]    2. Related Background Art  
           [0004]    In recent years, the development of downsizing technology of personal computers facilitated carrying of computer units and leads to promotion of so-called mobile computing to use a computer unit at an objective place, e.g., outdoors. The downsizing of computer units is also expected to be further developed from now on with progress in the LSI technology and packaging technology.  
           [0005]    There are, however, demands for large and high-definition monitors (displays) used in the computer units because of the necessity to present volumes of information processed inside the computer efficiently to users. Such demands do not except the compact and lightweight computer units designed with emphasis on portability. Research has been conducted to utilize a compact head-mounted display as a monitor of the computer unit in order to give a solution to such tradeoff demands.  
           [0006]    An example of appearance of a head-mounted display is presented in FIG. 4. The head-mounted display is composed of a display unit  201  for the right eye, a display unit  202  for the left eye, and a head mounting mechanism  203  for mounting these display units in front of the user&#39;s eyes, and thus has the structure similar to spectacles. This head-mounted display is mounted on the user&#39;s head and images supplied from an external device (not illustrated) are displayed on the right-eye display unit  201  and on the left-eye display unit  202 , so as to permit the user to visually recognize an image.  
           [0007]    Inside each of the right-eye display unit  201  and the left-eye display unit  202 , there are a transmissive or reflective, compact liquid-crystal display panel of about 1 to 3 centimeters diagonal and an optical system such as a prism or the like, in such arrangement that an image on the compact liquid-crystal display panel is guided to the user&#39;s eye. The user&#39;s eyes see an optically enlarged virtual image as if to view a large screen in front of the eyes. Therefore, the large display area with high resolution can be realized in the form of the compact and lightweight head-mounted display.  
           [0008]    [0008]FIG. 5 is a cross-sectional view to show an example of structure of a reflective liquid-crystal display panel.  
           [0009]    In FIG. 5, reference numeral  304  designates a silicon substrate,  303  a reflective sheet formed on the silicon substrate,  302  a liquid crystal forming each pixel, and  301  a glass sheet.  
           [0010]    Polarization of light (direction of polarization) passing through the liquid crystal is controlled by applying a voltage to the liquid crystal forming the pixel  302 .  
           [0011]    Illuminating light  305 ,  306  is linearly polarized light having been transmitted by an unrepresented polarizer. In a light-transmitting mode of the liquid crystal no voltage is applied to the liquid-crystal pixel and the beam  307  rotates the direction of its polarization 90° during transmission and reflection in the liquid-crystal layer and then travels through a second polarizer not illustrated, to appear bright to the user.  
           [0012]    In a light-blocking mode of the liquid crystal on the other hand, the voltage is applied to the liquid-crystal pixel and the beam  308  does not rotate the direction of its polarization during transmission and reflection in the liquid-crystal layer and thus is blocked by the second polarizer not illustrated, to appear dark to the user.  
           [0013]    [0013]FIG. 6 shows an example of structure of a head-mounted display using the reflective liquid-crystal display panel. The structure illustrated in FIG. 6 can be applied to the internal configuration of the right-eye display unit  201  and the left-eye display unit  202  in FIG. 4.  
           [0014]    Numeral  402  denotes a light source for illumination, which is comprised of light-emitting diodes of three colors, Red, Green, and Blue. Numeral  403  represents a first prism,  404  a reflective liquid-crystal display panel, and  405  a second prism.  
           [0015]    The light from the light-emitting diodes  402 , which is illuminating light to illuminate the reflective liquid-crystal panel  404 , is reflected in the first prism  403  to impinge on the surface of the reflective liquid-crystal panel. The illuminating light travels through the liquid-crystal surface controlled in quantity of passing light according to image data and is reflected by the reflective surface. This reflected light travels through the first prism  403  and then is reflected by a surface of the second prism  405  to reach the user&#39;s eyes  401 . The user observes the image as an enlarged virtual image  406  as illustrated.  
           [0016]    Next described is RGB frame-time-division color display utilized in the compact reflective color liquid-crystal displays.  
           [0017]    In order to obtain high-definition images on the compact liquid-crystal surface, the compact reflective liquid-crystal displays employ the time-division color display in which display periods of Red, Green, and Blue are provided in time division in one field display period, instead of the color display with an RGB color filter normally used in the large liquid-crystal displays. Since the liquid-crystal pixels are common to Red, Green, and Blue in the time-division method, the number of pixels is one third of that in the color filter method and the time-division method is thus more advantageous in downsizing.  
           [0018]    [0018]FIG. 7 shows a timing chart of the frame-time-division color display. The combination of three light-emitting diodes of Red, Green, and Blue is used for illumination of the reflective liquid-crystal display and the light-emitting diodes are activated at their respective times indicated as LED Red, LED Green, and LED Blue in the figure. Each of Red, Green, and Blue emits light once in one frame period and the time of emission thereof is not more than one third of one frame period. Therefore, there exist three emission times of Red, Green, and Blue in one frame period.  
           [0019]    In synchronism with the emission times, data of Red, Green, and Blue is written into a memory of a control circuit in the liquid-crystal display, and an image of Red, an image of Green, and an image of Blue are successively displayed. The images separated into Red, Green, and Blue are projected to the user&#39;s eyes in one frame as described, but the user&#39;s eyes can recognize them as an ordinary color image of mixture of Red, Green, and Blue, because the display times of the respective color images are short.  
           [0020]    [0020]FIG. 8 is a block diagram to show the structure of a frame-time-division color liquid-crystal display device. Numeral  601  designates an image memory for storing a component of Red among the image data,  602  an image memory for storing a component of Green among the image data,  603  an image memory for storing a component of Blue among the image data,  604  an LED control for controlling on/off of each of the light-emitting diodes of Red, Green, and Blue,  605  a light-emitting diode module consisting of the light-emitting diodes of Red, Green, and Blue,  606  a display for presenting color display in the RGB frame-time-division method, and  607  a display driver functioning to accept the image data, decompose the data into the components of Red, Green, and Blue, write the components into the respective image memories  601  to  603 , and control the liquid-crystal display  606  and the LED control  604 .  
           [0021]    The image data is decomposed into the components of Red, Green, and Blue in the display driver section and the components thus decomposed are written into the corresponding image memories  601  to  603 . The image data of Red, Green, and Blue thus written is read out of the corresponding image memories of the respective colors in synchronism with the on timing of the respective light-emitting diodes of Red, Green, and Blue used for illumination and then is written into the liquid-crystal display  606 . For example, the image data for Red is written into the liquid-crystal display  606  immediately before the on timing of the LED of Red and then the Red LED forming the LED module is lit up, thereby presenting the image of the Red component to the user&#39;s eyes.  
           [0022]    [0022]FIG. 9 shows the structure of a combination of the display with an ordinary computer unit to generate the display image data. The structure of the computer unit is illustrated as to only portions associated with the generation and display of the image data and the other structure is omitted.  
           [0023]    The image data prepared on a main memory (not illustrated) by CPU  701  is transferred through an internal bus of the computer such as PCI or AGP, to a graphics processing unit  703 . The graphics processing unit  703  performs an operation on the image data to expand the data to a display image corresponding to the resolution of the display  704 , and writes the result in an image memory  702 .  
           [0024]    The CPU rewrites only necessary parts in the contents of the image memory  702  on necessary occasions.  
           [0025]    Regardless of this writing from the CPU  701  into the image memory  702 , the display image data written in the image memory  702  is repeatedly read in the fixed period by the raster scan method to be displayed on the display  704 . This scan period is set, for example, so that 60 read operations are carried out for one second and 60 frames per second are written in the display, whereby stable images can be displayed without flicker even on the CRT normally used as a display.  
           [0026]    The transmission of the image data to the display can be made by a digital method for transmitting the contents of the image memory  702  in the digital form as they are or by an analog method for transmitting the RGB data of the image memory  702  in the form of analog signals after it is converted by respective D/A converters. In the case of the digital method of VGA (640×480 pixels) as an example of the resolution of the display, supposing each of RGB has the resolution of eight bits, the transmission rate of data to the display necessitates the transmission band of 640×480× 60 Hz×3 colors×8 bits=442 Mbit/sec.  
           [0027]    [0027]FIG. 10 shows an example of structure where the head-mounted display of the frame-time-division color display method is used as a display of a computer unit. In FIG. 10, a chip set  801  for executing control of CPU and bus, a graphics processing section  804 , and an image memory  802  are the same as the CPU and chip set  701 , the graphics processing section  703 , and the image memory  702  illustrated in FIG. 9. Further, an image memory  803  represents the image memories  601  to  603  of FIG. 8 all together and a display control  806  corresponds to the display driver  607 .  
           [0028]    The RGB image data of the raster scan repeated in the fixed period, which is outputted from the graphics processing unit  804 , is decomposed into the respective components of Red, Green, and Blue in the display control  806  and stored in the image memory  803 . The display control  806  further outputs this stored image data of Red, Green, and Blue in synchronism with the timing of the RGB frame-time-division color display and controls the LED control built in the display main body  808  to light up the light-emitting diodes of the three colors of R, G, and B to emit the illuminating light at required times.  
           [0029]    Since the display body  808  is desirably compact and lightweight in terms of being mounted on the head, almost all components (the image memory  803 , the display control  806 , etc.) other than the mechanism for mounting the display on the head are constructed in a unit separate from the display body  808 . The display body  808  is connected through a cable to the other components. It is common practice to construct a connection  805  between the graphics processing unit  804  and the display control  806  of a cable or to construct a connection  807  between the display control  806  and the display body  808  of a cable.  
           [0030]    However, when the head-mounted display is used as the display, user&#39;s free motion is impeded by the connection of the cable between the computer unit and the head-mounted display and the connection cable clings to the user because of the user&#39;s action, which degrades convenience.  
           [0031]    In order to solve this problem, it is conceivable to change the cable-connected part into radio connection, but it poses another problem of increase in size and cost of the structural part for the radio connection, because the volumes of the image data to be transmitted to the display are normally very large as described above.  
         SUMMARY OF THE INVENTION  
         [0032]    An object of the present invention is to provide a head-mounted display being applicable as a display device of a computer unit and constructed in inexpensive and compact structure of radio connection with the computer unit, and a system incorporating this head-mounted display.  
           [0033]    A head-mounted display apparatus according to one aspect of the present invention is a head-mounted display apparatus comprising: display means; support means which supports the display means in front of user&#39;s eyes; and display control means which supplies display data to be displayed on the display means, to the display means, wherein the display control means comprises radio communication means and generates the display data, based on a signal received by use of the radio communication means.  
           [0034]    The display means in this case is preferably constructed to implement color display by switching display between a plurality of predetermined monochrome displays. Further, the received signal is preferably image data and position information indicating a position of the image data in a display area which the display means can display.  
           [0035]    An information processing apparatus according to another aspect of the present invention is an information processing apparatus comprising image data generating means which generates image data to be displayed on an external display device, and radio communication means which transmits the image data by a radio signal.  
           [0036]    The image data generating means in this case is preferably constructed to generate image data of an area for change of display contents in a display area of the external display device.  
           [0037]    An information processing system according to another aspect of the present invention is an information processing system comprising: a head-mounted display device comprising display means, support means which supports the display means in front of user&#39;s eyes, and display control means which supplies display data to be displayed on the display means, to the display means; and an information processing device which can use the head-mounted display device as an external display device, wherein the information processing device comprises image generating means which generates image data to be displayed on the head-mounted display device, and first radio communication means which transmits the image data by a radio signal, and wherein the display control means of the head-mounted display device comprises second radio communication means capable of communication with the first radio communication means, and the display control means generates the display data, based on the image data received from the first radio communication means.  
           [0038]    The image data generating means in this case is preferably constructed to generate image data of an area for change of display contents in a display area of the display means. Further, the image data is preferably one including position information indicating a position of the image data in the display area of the display means. At the same time, the display means is preferably constructed to implement color display by switching display between a plurality of predetermined monochrome displays.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0039]    [0039]FIG. 1 is a block diagram to show the structure of a head-mounted display system according to an embodiment of the present invention;  
         [0040]    [0040]FIG. 2 is a block diagram to show an example of structure of a radio transceiver in FIG. 1;  
         [0041]    [0041]FIGS. 3A and 3B are diagrams to illustrate packet forms in radio transmission;  
         [0042]    [0042]FIG. 4 is a diagram to illustrate an example of appearance of the head-mounted display;  
         [0043]    [0043]FIG. 5 is a diagram to illustrate an example of structure of a reflective liquid-crystal display panel;  
         [0044]    [0044]FIG. 6 is a diagram to illustrate an example of structure of a head-mounted display using the reflective liquid-crystal panel;  
         [0045]    [0045]FIG. 7 is a diagram to illustrate a timing chart of the frame-time-division color display;  
         [0046]    [0046]FIG. 8 is a diagram to illustrate a color liquid-crystal display device of the RGB frame-time-division method;  
         [0047]    [0047]FIG. 9 is a block diagram to illustrate an example of structure of a computer unit; and  
         [0048]    [0048]FIG. 10 is a block diagram to show an example of structure where the head-mounted display is used as a display device of a computer unit.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0049]    A preferred embodiment of the present invention will be described hereinafter with reference to the drawings.  
         [0050]    (System Configuration)  
         [0051]    [0051]FIG. 1 is a block diagram to show an example of structure of an information processing system, which is an embodiment of the information processing system according to the present invention.  
         [0052]    The computer system is comprised of a computer unit  100  and a head-mounted display  200  and radio connection is established between the computer unit  100  and the head-mounted display  200 .  
         [0053]    In the computer unit  100 , reference numeral  101  designates a CPU and attendant chip set (which will be referred to hereinafter simply as CPU  101 ),  102  a rewritten address memory which temporarily stores address information of newly rewritten display image data,  103  a first image memory which temporarily stores the image data to be displayed,  104  an internal bus which connects the CPU  101  to the graphics processing unit  105 ,  105  the graphics processing unit which accepts a graphics command from the CPU  101  and which converts it into image data,  106  a first radio transceiver which transmits the display image data outputted from the graphics processing unit  105  in the form of a predetermined radio signal and which receives a signal from a second radio transceiver through an antenna  107 , and  107  the first antenna through which the radio signal output from the first radio transceiver is sent into the space and through which the radio signal is received from the second radio transceiver  109 .  
         [0054]    In the head-mounted display  200 , numeral  108  denotes a second antenna through which the radio signal output from a second radio transceiver  109  is sent into the space and through which the radio signal from the first radio transceiver is received,  109  the second radio transceiver for two-way transmission of radio data through the antenna  108 ,  110  a second image memory which stores the display image data in the form suitable for display on a liquid-crystal display incorporated in a display body  112 ,  111  a display control which periodically reads data out of the second image memory  110  to display it on the liquid-crystal display incorporated in the head-mounted display body  112  and which also receives the image data from the second radio transceiver  109  to update the contents of the second image memory  110 , and  112  the head-mounted display body which presents the display image from the computer unit  100  to the user.  
         [0055]    In the head-mounted display  200 , the structure other than the display body  112  may be built in the display body or may be constructed, for example, to be hooked on a belt or the like, together with a secondary battery as a power supply, separately from the display body  112 .  
         [0056]    (Operation)  
         [0057]    The operation will be described below.  
         [0058]    The image data prepared in the CPU  101  is sent via the internal bus  104  such as the AGP or the PCI to the graphics processing unit  105 . The graphics processing unit  105  executes a predetermined operation on the image data thus received to convert it to the image data in the form suitable for display, and writes the data in the first image memory  103 .  
         [0059]    Then the processing unit  105  stores the address information corresponding to the image data written in the first image memory  103 , in the rewritten address memory  102 .  
         [0060]    Therefore, when the entire area in the display screen is rewritten, all the contents in the first image memory  103  are rewritten and addresses of rewritten data corresponding to the entire area of one screen are also stored in the rewritten address memory  102 .  
         [0061]    Particularly, when a part of the screen is rewritten as frequently carried out during use of the computer unit, e.g., during execution of software with GUI using windows, only a portion corresponding to the rewritten portion is rewritten out of the contents of the image memory  103  and addresses of the rewritten portion are stored in the rewritten address memory  102 .  
         [0062]    The address data indicating the rewritten portion can be any form of address data, e.g., data using a combination of a start address and an end address of rewriting, data using addresses corresponding to coordinates of the left upper corner and the right lower corner in the case of the rewritten area being a rectangle like the inside of a window, or the like. Of course, all the rewritten addresses may also be stored on an individual basis.  
         [0063]    Further, it is also possible to preliminarily divide the data of one screen into blocks of predetermined units, designate block numbers to the respective blocks, and use a block number or the like as the address data indicating the rewritten portion.  
         [0064]    Although FIG. 1 shows the separate blocks of the rewritten address memory  102  and the first image memory  103 , the memories may be separate memories or separate areas on a single memory in practice.  
         [0065]    The information for rewriting the display screen, stored in the rewritten address memory  102  and in the first image memory  103 , is transmitted in the form of a radio signal to the head-mounted display  200  by use of the first radio transceiver  106  and the first antenna  107 . Then the radio signal is received by the second antenna  108  and the second radio transceiver  109  in the head-mounted display  200 .  
         [0066]    This radio transmission operation will be described below. The first radio transceiver  106  and the second radio transceiver  109  have the same internal structure illustrated in FIG. 2. The image data received from the graphics processing unit  105  by the first radio transceiver  106  is converted into a data packet of a configuration as illustrated in FIG. 3A, in a protocol portion  902  and the data packet is sent to a modem  903 . The data packet is one packet formed by placing a preamble of communication control data necessary for the synchronizing operation on the receiver side or the like, as a header, and attaching changed address data of image and changed image data thereafter.  
         [0067]    This data packet is subjected to data modulation for radio transmission, e.g., the phase modulation in the modem  903  of the post stage. Then this modulated signal further undergoes frequency conversion from the base band signal to a radio-frequency signal in an RF portion  904  of the post stage and the converted signal radiates as a radio wave through the first antenna  905  into the space.  
         [0068]    On the other hand, the reverse operation is carried out on the occasion of reception by the second radio transceiver  109 . Namely, the second antenna  108  captures the radio wave radiating from the first antenna  905  and the RF portion  904  performs the frequency conversion from the radio-frequency signal to the base band signal. Then the base-band modulated signal is demodulated in the modem  903  into the same packet data, illustrated in FIG. 3A, as that when transmitted. Further, the protocol portion  902  takes the changed address data and changed image data out of the data packet and outputs the data to the display control  111 .  
         [0069]    In the data transmission using the radio wave, the radio transmission paths are instable because of change in the ambience, such as obstacles, reflection, or the like and data cannot be always transmitted at a constant data transmission rate. It is thus necessary to give consideration to such circumstances that the second radio transceiver fails to receive the radio packet transmitted from the first radio transceiver. For that reason, the system employs a method of preparing a packet for control (control packet) as illustrated in FIG. 3B and sending the control packet informing of normal reception from the second radio transceiver to the first radio transceiver when the second radio transceiver normally receives the packet.  
         [0070]    When the second radio transceiver sends no response within a predetermined time after the first radio transceiver sends the control packet in succession after the image packet, the same image data packet is again sent, which solves the problem of temporary reception failure.  
         [0071]    Since the transmission of packet is changed according to the circumstances of the radio transmission paths in this way, transmission rates of data that can be transmitted through the radio transmitting means to the head-mounted display side are not constant.  
         [0072]    For this reason, the transmission rate of data sent from the first image memory  103  through the graphics processing unit  105  to the first radio transceiver  106  is determined through transmission of the control packet between the first radio transceiver  106  and the second radio transceiver  109 , and data to be transmitted is taken according thereto through the graphics processing unit  105  out of the rewritten address memory  102  and the first image memory  103 .  
         [0073]    In general, the radio data transmission is lower in speed than the cable transmission. However, since the system of the present embodiment is constructed to write the image data of the changed portion in the first image memory and thereafter transmit this data and address data together to the radio transceiver, the data received by the radio transceiver is the data of only the portion changed when the CPU changes the display image. When compared with the case wherein the image data is outputted in a fixed period (normally 60 to 85 Hz) of the raster image from the conventional graphics processing unit directly to the display, the data transmitted in the present embodiment is only data upon rewriting of a partial image, which is frequently utilized in use of a personal computer, and thus the structure is one suitable for relatively low-speed radio transmission. The protocol control portion  902  executes the generation of the control packet and the processing according to the contents thereof.  
         [0074]    In the present invention the rates of radio transmission required of the first and second radio transceivers  106  and  109  vary depending upon the display resolution, the number of display colors, the contents of display (still image/moving picture), and so on, but the rates of approximately several hundred Kbps to several Mbps suffice for practical use, because rewriting of the entire screen is rare in normal use. The output power can also be small, because the distance is not so large between the computer device and the display in works using the computer. Examples of the radio transmission methods satisfying such conditions can be Bluetooth, IEEE802.11, and so on.  
         [0075]    The changed address data and changed image data outputted from the second radio transceiver  109  is converted to a storage format of the second image memory  110  in the display control portion  111  to be saved.  
         [0076]    The second image memory  110  is constructed to have separate memories or separate memory areas to save three frame images of Red, Green, and Blue, because the data of Red, the data of Green, and the data of Blue is separately written at the respective times into the liquid-crystal panel of the liquid-crystal display of the color time-division method incorporated in the display body  112 .  
         [0077]    The display control portion  111  sends the data of Red, the data of Green, and the data of Blue at the respective times to the liquid-crystal display of the color time-division method, thereby implementing the color display in the display body  112 .  
         [0078]    As described above, the present embodiment utilizes the radio communication between the head-mounted display and the computer device for generating the display image data thereof, which increases degrees of freedom in a mounted state of the display. In addition, since transmitted data volumes are reduced by the transmission of only the image data corresponding to the changed portion in the display image data, it becomes feasible to downsize the circuitry necessary for the radio communication.  
         [0079]    (Modifications)  
         [0080]    In the above embodiment the image displayed on the display body  112  was an ordinary two-dimensional image, but in the case of the display body  112  consisting of the independent displays for the right eye and for the left eye, a stereoscopic image can also be displayed in such a manner that the image memory  110  stores the image data corresponding to the display for the right eye and the image data corresponding to the display for the left eye and that separate images with parallax are displayed on the two displays right and left.  
         [0081]    The radio communication was described only in the case of use of the radio wave, but the radio communication with light may also be employed if the sending and receiving operations can be carried out on a stable basis.  
         [0082]    As described above, according to the present invention, the head-mounted display usable as a display device of the computer unit is constructed to be able to receive the image data for display via the radio signal, whereby there is no need for use of a connection cable between the computer unit and the head-mounted display and whereby the user can freely move while wearing the display.