Patent Publication Number: US-2022221727-A1

Title: Head-mounted display system

Description:
RELATED APPLICATION 
     This application claims the benefit of priority of Europe Patent Application No. 21150964.1 filed on Jan. 11, 2021, the contents of which are incorporated herein by reference in their entirety. 
     FIELD AND BACKGROUND OF THE INVENTION 
     The present invention relates to a head-mounted display system. 
     Head-mounted display systems are used for different applications like displaying images of a medical imaging device to medical personal during a medical procedure. However, an operator wearing a head-mounted display system may have to change views, for example, between microscopic images displayed by the head-mounted display and the real environment for macroscopic procedures. Simply taking off the head-mounted display system for a view on the real scene is disadvantageous in the medical field with respect to a required sterile environment. Therefore, known head-mounted display systems are equipped with semi-transparent displays to display images in parallel to providing a view on the real environment. Due to the semitransparent display, the view on the real environment is shaded, which results in less visibility of details and respective risks. Accordingly, head-mounted display systems have been proposed that provide a display configured to be manually pivotable out of an operator&#39;s viewing field. However, due to the electronic control elements of the display, the weight of such display requires a comparably rigid support structure capable of securely holding the display in each pivoted position. Further, the weight of the display may cause inconveniences for an operator in at least some of the pivot positions. 
     Accordingly, it is an object of the present invention to provide an improved head-mounted display system. 
     SUMMARY OF THE INVENTION 
     The object is solved by a head-mounted display system according to claim  1 . Further aspects of the present invention are subject to the dependent claims. 
     According to the present invention, the head-mounted display system comprises at least one head-mounted display comprising at least one display portion, a carrier member to be worn by an operator to movably support the at least one head-mounted display, and at least one control device configured to control the at least one head-mounted display, wherein the at least one control device is spatially separated from the head-mounted display. 
     Due to the spatial separation of the control device, such as a display driver board, from the head-mounted display, the weight of the head-mounted display is decreased accordingly. Therefore, requirements with respect to a support structure of a movable head-mounted are reduced. Furthermore, the weight distribution of a respective head-mounted display system can be improved. The control device may be attached to the carrier member or may be otherwise attached to the head-mounted display system. The control device may also be configured to be connected to the head-mounted display system by a wired or wireless connection instead of being attached to the head-mounted display system as such. 
     In some embodiments, the at least one head-mounted display is pivotably supported by the carrier member, and the at least one control device is connected to the at least one head-mounted display by at least one flexible conductive element. 
     For example, the control device is attached to the carrier member, wherein the flexible conductive element transmits control signals from the control device to the head-mounted display. Due to the flexibility of the flexible conductive element, the head-mounted display can be pivoted with respect to the carrier member without affecting the connection to the control device. Alternatively or in addition, the control device may be configured to transmit control signals wirelessly, as already indicated above. 
     In particular, the at least one flexible conductive element is a coaxial cable, preferably a micro coaxial cable. 
     A coaxial cable is mechanically robust with respect to the pivoting of the head-mounted display. Alternatively, rigid-flex circuit boards or a flat ribbon cable may be used to connect with the head-mounted display. However, a coaxial cable also provides more flexibility when the head-mounted display is configured to provide a lateral movement with respect to the carrier member in addition or alternatively to a pivot movement. A lateral movement may be implemented to move the head-mounted display out of an operator&#39;s view alternatively or in addition to a respective pivot movement and/or to adapt the head-mounted display to an individual interocular distance of an operator and/or for an individual diopter compensation. 
     According to some embodiments, the inner core of the coaxial cable provides data transfer line surrounded by a first isolating layer, followed by a shielding layer and a subsequent second isolating layer. 
     The above layer structure shields the inner core as high-frequency data-line from electromagnetic disturbances. Similarly, a rigid-flex circuit board or a flat ribbon cable as alternatives to the coaxial cable preferably provide a data line sandwiched between two isolating layers, each of which followed by a shielding layer and a subsequent further isolating layer. 
     Advantageously, the head-mounted display system comprises at least two head-mounted displays each of which comprises at least one display portion, and wherein the at least one control device is configured to control both of the at least two head-mounted displays based on a control input. 
     Accordingly, when the head-mounted display system comprises more than one head-mounted display, the head-mounted displays can be controlled by one control device. 
     In some embodiments with more than one head-mounted display, each of the head-mounted displays is connected to the control device by at least one flexible conductive element, and wherein the at least one control device is configured to control both of the at least two head-mounted displays by a respective one of the flexible conductive elements. 
     Accordingly, the control device is configured to control the head-mounted displays based on a single control input. The single control input is not restricted to a single control command and may also comprise a set of control commands. Alternatively, the head-mounted displays are connected in series and the control command or control commands are transmitted from the control device to the first of the head-mounted displays and from the first of the head-mounted displays to the subsequent one and so on. 
     In particular, the control device is configured to control each of the at least two head-mounted displays independently. 
     Therefore, the control device may comprise a processor unit to process a received control input and to assign a control command or control commands to one and/or the other of the head-mounted display systems. Such assignment may depend on a preset configuration, e.g. to display images to both of the head-mounted displays while displaying text information only to one of the head-mounted displays. The control may also be configured to process images to be displayed, e.g. to provide 3D images by providing respectively processed images to a head-mounted display associated with a right eye of an operator and a head-mounted display associated with a right eye of a user. 
     According to some embodiments, the head-mounted display system comprises at least two head-mounted displays each of which comprises at least one display portion, and two control devices each of which is connected to one of the at least two head-mounted displays by a respective one of the flexible conductive elements. 
     In such configuration, the at least two head-mounted displays are not controlled by a common control device but each head-mounted display provides its own control device assigned thereto by the respective connection. As a result, the respective control devices may be less complex, e.g. may not require a processor unit capable of processing a control input with respect to an individual assignment of control commands. Further, more than one control device may be implemented for redundancy reasons since the risk of a simultaneous failure of all control devices is minor. Accordingly, the risk of a total display loss is reduced. 
     Advantageously, the control device comprises a SPS-connector. 
     Accordingly, the control device is configured to receive further signals and/or processed data without requiring a respective capability to provide such signals and/or process data by the control device itself. For example, respective signals and/or data may be provided by a IMU (inertial measurement unit) configured to detect a position and/or orientation of the head-mounted display system to adapt images to be displayed in accordance with such position and/or orientation of the head-mounted display system. Alternatively or in addition, a CAN bus may be connected to the SPS-connector to provide signals and/or data of other external devices. 
     In some embodiments, the head-mounted display system comprises a motor for pivoting the at least one head-mounted display with respect to the carrier member, and wherein the motor is preferably arranged offset from the pivot axis of the at least one head-mounted display. 
     In particular with respect to a required sterile handling, a manual pivoting of the head-mounted display can be avoided by the motor. A respective movement of the head-mounted display may be controlled by tracked gestures, tracked head and/or eye movements, a footswitch and/or other control mechanisms allowing a sterile operation. Preferably, the respective control mechanisms may not require a movement of an operator&#39;s hand associated with a current procedure of the operator. 
     The arrangement of the motor offset from the pivot axis of the head-mounted display may improve the weight distribution. Further, the center of gravity may be displaced from a leading position to a more rearward position of the head-mounted display. Accordingly, a tendency of the head-mounted display to fall down or to provide a pulling force when an operator&#39;s head is leant forward may be reduced. 
     Since the control device may provide a flexible connection to the head-mounted display, the offset of the motor does not interfere with such connection. In other words, since the control device may be held stationary with only the head-mounted display being pivoted, the motor may be offset from the pivot axis without further adaptions. 
     Preferably, the head-mounted display system is configured to display images of a medical imaging device. 
     As already indicated by examples with respect to medical procedures, the inventive head-mounted display system provides specific advantages with respect to a sterile handling and free-hands requirements in view of medical procedures. 
     In some embodiments, the medical imaging device is a microscope. 
     The use of the head-mounted system according to the invention for displaying images of a medical microscope, preferably a robotic medical microscope, allows an operator like a surgeon to change the view from microscopic to macroscopic and vice versa in a sterile manner and with a head-mounted display system with improved ergonomics with respect to weight and weight distribution. 
     In some embodiments, the medical imaging device is an endoscope. 
     Here, the same advantages as with respect to the microscope apply. 
     Further advantages, aspects and details of the disclosure are subject to the claims, the following description of preferred embodiments applying the principles of the disclosure and drawings. In the figures, identical reference signs denote identical features and functions. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view of a head-mounted display system with a control device according to a first exemplary embodiment; 
         FIG. 2  is a schematic perspective view of a head-mounted display system with a control device according to a second exemplary embodiment; 
         FIG. 3  is a schematic front view on the head-mounted display system according to the second embodiment; 
         FIG. 4  is a schematic view of the control device according to the second embodiment and flexible conductive elements; 
         FIG. 5  is a partial cross-sectional perspective view of a coaxial cable as exemplary embodiment of a flexible conductive element; 
         FIG. 6  is a cross-sectional view of a rigid-flex circuit board shielded on both sides as further exemplary embodiment of a flexible conductive element; and 
         FIG. 7  is a cross-sectional view of a rigid-flex circuit board shielded on one side as further exemplary embodiment of a flexible conductive element. 
     
    
    
     DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION 
       FIG. 1  shows a schematic perspective view of a head-mounted display system  1  with a control device  30  according to a first exemplary embodiment. The head-mounted display system  1  further comprises a carrier member  20  and two head-mounted displays  10   a  and  10   b  each of which comprising a display portion  11   a  and  11   b , respectively. The head-mounted displays are pivotably supported by the carrier member  20 . 
     The control device  30  is configured to provide images of a medical imaging device (not shown), like a microscope or endoscope, to the head-mounted displays  10   a ,  10   b  and the display portions  11   a ,  11   b , respectively. Further, the control device  30  is configured to control the displayed images, for example, by adjusting a contrast, brightness and/or magnification. Alternatively or in addition, the control device  30  may be configured to also provide other information, like text information or optical alert signal, to at least one of the head-mounted display systems  10   a ,  10   b  and/or to control further functions independent of displaying images and/or other information. The control device  30  may be also configured to receive signals from the head-mounted displays  10   a ,  10   b.    
     To provide the head-mounted displays  10   a ,  10   b  with respective control signals, each of the head-mounted displays  10   a ,  10   b  is connected to the control device  30  by a flexible conductive element, here, a coaxial cable  31 . The respective ends of the respective coaxial cable  31  to be connected with one of the head-mounted displays  10   a ,  10   b  are directly connected to the respective display portions  11   a ,  11   b . In an alternative embodiment, the ends of the respective coaxial cables  31  may also be connected to a processor of the respective head-mounted displays  10   a ,  10   b  to further process image signals or the provide signals to another component different from the display portion  11   a ,  11   b.    
     According to the first embodiment, the control device  30  is configured as mono-processing unit. i.e. both head-mounted displays  10   a  and  10   b  receive the same signals according to a control input to the control device  30 . 
       FIG. 2  shows a schematic perspective view of a head-mounted display system  1 ′ with a control device  30 ′ according to a second exemplary embodiment. The second embodiment differs from the first embodiment in that the control device  30 ′ is configured as stereo-processing unit, i.e. the head-mounted displays  10   a  and  10   b  can be controlled independently. Accordingly, the control device  30 ′ comprises two distinct processing units  30 ′ a ,  30 ′ b  ( FIG. 4 ). In an alternative embodiment, a common processor is portioned accordingly two provide such functionality. According to the second embodiment, the two processing units  30 ′ a ,  30 ′ b  are configured to process a control input differently with respect to the assignment of control signals to the respective head-mounted display  10   a ,  10   b  connected thereto. Neither all of the control signals derived from the control input to be assigned to the head-mounted displays  10   a ,  10   b  have to be different nor control signals have to be different in any event. Accordingly, the independent control of the head-mounted displays  10   a ,  10   b  may depend, for example, on a type of a control input, predetermined settings and/or defined trigger events. For example, in a two-dimensional displaying mode each of the processing units  30 ′ a ,  30 ′ b  of the control device  30 ′ provides the same image signals to each of the head-mounted displays  10   a ,  10   b  and display portions  11   a ,  11   b , respectively. However, when the control input or a user input as trigger event requests a three-dimensional displaying mode, at least one of the processing units  30 ′ a ,  30 ′ b  of the control device  30 ′ adapts the imaging data accordingly to provide different images to display portions  11   a ,  11   b  to reproduce a three-dimensional impression. In an alternative embodiment, the stereo-processing unit may receive separate control inputs for each of the head-mounted displays  10   a ,  10   b . In other words, the stereo-processing unit provides two separate signal channels. 
       FIG. 3  shows a schematic front view on the head-mounted display system  1 ′ according to the second embodiment. However, the following description may be also applicable analogously to the first embodiment. 
     As indicated by the pivot axis O, the head-mounted displays  10   a ,  10   b  are pivotably supported by the carrier member  20 . Here, the head-mounted displays  10   a .  10   b  can be pivoted independently from each other. However, in a variant, the head-mounted display system  1 ′ may be configured to pivot the head-mounted displays  10   a ,  10   b  simultaneously. 
     The control device  30 ′ is arranged stationary in the carrier member  20 , when the head-mounted displays  10   a ,  10   b  are or at least one of the head-mounted displays  10   a ,  10   b  is pivoted around the axis O. Accordingly, there is a relative movement between the control device  30  and the respective head-mounted display  10   a ,  10   b . However, due to the coaxial cable  31 , the relative movement is neither impeded in principle nor the connection is prone to broke. 
     Further, the pivoting of the head-mounted displays  10   a ,  10   b  is implemented by a motor  40 . An independent movement of the head-mounted displays  10   a ,  10   b  is implements by a respectively switchable transmission system (not shown). In an alternative embodiment, each of the head-mounted displays  10   a ,  10   b  may be driven by separate motors. In the exemplary embodiment, the motor  40  is arranged offset from the pivot axis O. Accordingly, the weight of the motor  40  is displaced to a position providing a better balance of the head-mounted display system  1 ′ and therefore an improved comfort for an operator wearing the head-mounted display system  1 ′ may be achieved. 
       FIG. 4  shows a schematic view of the control device  30 ′ according to the second embodiment and flexible conductive elements. More precisely, two coaxial cables  31  are each connected to the control device  30 ′ via connection interfaces  30 ′ c ,  30 ′ d . The connection interface  30 ′ c  is associated with the processing unit  30 ′ a  to provide control signals to the head-mounted display  10   a  and the connection interface  30 ′ d  is associated with the processing unit  30 ′ b  to provide control signals to the head-mounted display  10   b . Further, the control device  30 ′ comprises a SPS-connector  32  to allow the reception of further signals and commands without providing respective components for such signal generation on the control device  30 ′. 
       FIG. 5  illustrates a partial cross-sectional perspective view of a coaxial cable  31  as exemplary embodiment of a flexible conductive element and as shown  FIGS. 1 to 5 . A data transfer line  31   a  accomplishes the data transfer. To shield the data transfer line  31   a  from electromagnetic interferences, the data transfer line  31   a  is surrounded by a first isolating layer  31   b  followed by a shielding layer  31   c  and a subsequent second isolation layer  31   d.    
       FIG. 6  shows a cross-sectional view of a rigid-flex circuit board  31 ′ shielded on both sides as further exemplary embodiment of a flexible conductive element. The rigid-flex circuit board  31 ′ provides a similar configuration as the coaxial cable  31  but the data transfer line  31 ′ a  is not surrounded by respective layers but sandwiched by such layers. Specifically, the data transfer line  31 ′ a  is sandwiched between two first isolating layers  31 ′ b  followed by respective shielding layers  31 ′ c  and subsequent second isolating layers  31 ′ d . The layer configuration is covered by a cover layer  31 ′ e , for example, made of polyimide. 
     As a variant,  FIG. 7  shows a cross-sectional view of a rigid-flex circuit board  32 ′ shielded on one side as further exemplary embodiment of a flexible conductive element. Starting from the data transfer line  31 ′ a  to the outside in one direction, the rigid-flex circuit board  32 ′ provides a first isolating layer adjacent to the data transfer line  31 ′ a  followed by a shielding layer  31 ′ c , a subsequent second isolating layer  31 ′ d  and a cover layer  31 ′ e . On the opposite side of the data transfer line  31 ′ a , a first isolating layer  31 ′ b  is disposed adjacent to the data transfer lien  31 ′ a  followed by a cover layer  31 ′ e.    
     It is to be noted that the given examples are specific embodiments and not intended to restrict the scope of protection given in the claims. In particular, single features of one embodiment may be combined with another embodiment. Further, different components of the head-mounted display systems as described may be substituted by other components. For example, the rigid-flex circuit board may be substituted by a flat ribbon cable. 
     LIST OF REFERENCE SIGNS 
     
         
           1 ,  1 ′ head-mounted display system 
           10   a ,  10   b  head-mounted display 
           11   a ,  11   b  display portion 
           20  carrier member 
           30 ,  30 ′ control device 
           30 ′ a ,  30 ′ b  processing unit 
           30 ′ c ,  30 ′ d  connection interface 
           31  coaxial cable (flexible conductive element) 
           31 ′,  31 ′ rigid-flex circuit board (flexible conductive element) 
           31   a ,  31 ′ a  data transfer line 
           31   b ,  31 ′ b  first isolating layer 
           31   c ,  31 ′ c  shielding layer 
           31   d ,  31 ′ d  second isolating layer 
           31 ′ e  cover layer 
           32  SPS-connector 
           40  motor 
         O pivot axis