Patent Publication Number: US-2023161406-A1

Title: Image display system

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-189133 filed on Nov. 22, 2021, which is incorporated herein by reference in its entirety including the specification, claims, drawings, and abstract. 
     TECHNICAL FIELD 
     The present disclosure relates to an image display system for providing an occupant of a vehicle with an augmented landscape which is displayed by superimposing an image on an actual landscape viewed by the occupant. 
     BACKGROUND 
     A technique for providing an augmented landscape to an occupant of a vehicle has been known; the technique in which a display unit of a wearable device, which is worn like a pair of glasses or goggles by the occupant, displays an image superimposed on an actual landscape viewed through the display unit by the occupant. The image may include, for example, a captured image of an outside area which is located outside a view of the occupant, such as an image captured from an area located behind the vehicle or on a lateral outside thereof, or a virtual image. 
     Patent publication No. JP 2017-129406 A discloses a technique of virtually displaying a preceding vehicle (AR pacesetter  140 ) at a position in front of driver&#39;s own vehicle. A driver is guided to the destination by operating his/her own vehicle following the preceding vehicle ( 140 ). A wearable device (smart glasses  500 ) worn by the driver incorporates a camera ( 515 ), detects a stationary object, such as a front window ( 100 ) based on an image captured by the camera ( 515 ), and determines a display position of the preceding vehicle ( 140 ) and other parameters based on a position of the preceding vehicle ( 140 ). It should be noted that component names and reference numerals within parentheses are of the above-described patent publication, and are not associated with component names and reference numerals used in the description about embodiments of this application. 
     When an image is superimposed on a landscape outside a vehicle, it is desirable to acquire information on a position and an attitude of a wearable device relative to an object existing outside the vehicle. However, because a wide variety of objects are present outside the vehicle, a load of computation for recognizing the objects located outside the vehicle is great. Further, in some cases, images of the objects located outside the vehicle may not be obtained, depending on external environments. For example, undesirable factors, such as deficiency of an amount of light or halation created by severe back-light, may render the objects unrecognizable. 
     The present disclosure relates to acquisition of a feature point associated with an object located outside a vehicle that is used as a reference against which a position and an attitude of a wearable device are defined, and is directed to providing at least one of advantageous effects of reducing a load of arithmetic operation to recognize the outside object and being impervious to influence of external environments. 
     SUMMARY 
     An image display system according to this disclosure includes a wearable device which is worn by an occupant of a vehicle and is equipped with a display unit configured to display an image within a view of the occupant and a wearable camera, a marker projector which is mounted on the vehicle and configured to project a marker on a forward road surface to form a marker image on the forward road surface, a wearable device position and attitude sensor configured to detect a position and an attitude of the wearable device based on the marker image captured by the wearable camera, and an image processor configured to determine a position of the image placed within the view of the occupant on the display unit using the detected position and attitude of the wearable device and operate the display unit to display the image at the determined position. 
     The image display system according to this disclosure can acquire the marker image even under an adverse environment in which a feature point located outside the vehicle cannot be properly acquired due to deficiency of an amount of light or halation, for example, and accordingly detect a relative position of the wearable device and the forward road surface and the attitude of the wearable device relative to the forward road surface. 
     Further, a shape of the marker may be a predetermined two-dimensional figure. When the shape of the marker is predetermined, a load of computation to extract the marker image from an image of forward view is reduced. 
     In addition, the image display system may further include a road surface shape detector configured to detect, based on the position and shape of the marker image, at least either an inclination or unevenness of the road surface. In this case, the predetermined image which is displayed on the road surface can be displayed so as to conform to the road surface. 
     Moreover, the image display system may further include a pupil position sensor configured to detect a position of a pupil of the occupant relative to the display unit, and the image processor may be further configured to determine the position of the image placed within the view of the occupant on the display unit using, in addition to the detected position and attitude of the wearable device, the detected position of the pupil. This allows the position of the image displayed on the display unit to be fitted to an actual landscape with high accuracy. 
     According to the present disclosure, the marker image can be acquired under an adverse external environment, such as being in the nighttime or having severe back-light, and the image can be accordingly displayed at an appropriate position on the display. Further, because the shape of the marker is predetermined, the load of computation associated with extraction of the marker image can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Embodiments of the present disclosure will be described based on the following figures, wherein: 
         FIG.  1    is a block diagram showing a configuration of an image display system according to an embodiment; 
         FIG.  2    is an external view of a wearable device worn by a driver; 
         FIG.  3    is a diagram showing a shape of a marker; 
         FIG.  4    shows a view seen by the driver wearing the wearable device on which no image is displayed; 
         FIG.  5    shows a view seen by the driver wearing the wearable device on which images are additionally displayed; 
         FIG.  6    is a conceptual diagram representing a change in a marker image due to an inclination of a roadway; and 
         FIG.  7    shows an example of a change in a shape of the marker image due to the inclination of the roadway. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments will be described with reference to the drawings. In the following description, specific embodiments are explained for better understanding. The embodiments are presented by way of illustration, and the present disclosure may be embodied in various other ways. 
       FIG.  1    is a block diagram showing a functional configuration of an image display system  10  according to an embodiment. The image display system  10  includes a wearable device  20  and an on-board system  40 . 
     The wearable device  20  is a device which is worn in a manner similar to spectacles or goggles by an occupant, such as a driver, of a vehicle. The wearable device  20  includes a device position and attitude sensor  30 , a pupil position sensor  32 , an image controller  34 , and an organic electroluminescence (EL) display  36 . 
     The wearable device  20  is schematically illustrated in  FIG.  2   . In  FIG.  2   , the wearable device  20  is shown in a state where it is worn by a driver  200 . The wearable device  20  is a device formed in the shape of spectacles, and may be referred to as smart glasses in some cases. The wearable device  20  includes temples  22  which are linear frame members designed to be put on the ears of a user, and a rim  24  joined to the temples  22 , the rim  24  being a frame member designed to surround the eyes of the user and to be put on the nose of the user. 
     A display unit, in particular, an organic EL (Electro Luminescence) display  36  is arranged within the rim  24 . The organic EL display  36 , which is positioned so as to cover a region in front of the eyes of the driver  200 , has a high degree of transparency (high light transmittance) for allowing the driver  200  to view forward through the organic EL display  36  when no image is displayed thereon. An image may be formed on a part or the whole part of the organic EL display  36  under the control of the image controller  34 . When the image is formed on a partial region of the organic EL display  36 , an augmented landscape can be presented to the driver  200  by displaying a generated image so as to be overlaid on a landscape which is actually viewed by the driver  200 . 
     The device position and attitude sensor  30  is disposed in the vicinity of a coupling area between the rim  24  and the temple  22  of the wearable device  20 . The device position and attitude sensor  30  detects a position and an attitude of the wearable device  20  within the vehicle. Specifically, the device position and attitude sensor  30  detects the position of the wearable device  20  in a rectangular coordinate system which is fixed to the vehicle, and the attitude of the wearable device  20  (i.e., inclinations of the wearable device  20  relative to coordinate axes of the rectangular coordinate system). The device position and attitude sensor  30  can be implemented, for example, using a camera (such as a wearable camera) which is fixed to the wearable device  20  and configured to capture an image of a forward area. Here, a position and an attitude of the camera can be identified by comparing the image captured by the camera with data of a layout of objects, such as parts and devices, existing inside the vehicle. Then, the position and the attitude of the wearable device  20  can be detected through the camera which is fixedly installed on the rim  24  and thus the organic EL display  36  integrated into the rim  24 . 
     The pupil position sensor  32  is disposed on an upper part of the rim  24  in the vicinity of the center of the upper part. The pupil position sensor  32  is configured to detect positions of the pupils in the left and right eyes of the driver  200  relative to the rim  24 . The pupil position sensor  32  may be implemented using a camera as in the case of the device position and attitude sensor  30 . 
     The temple  22  internally incorporates the image controller  34 . The image controller  34  is configured to display an image on the organic EL display  36  based on data received from the on-board system  40 . The wearable device  20  can operate the image controller  34  and the organic EL display  36  to perform image representation and provide the driver  200  with a visual environment that is different from an ordinary environment through the image representation. 
     Returning to  FIG.  1   , the on-board system  40  is explained below. The on-board system  40  is a system mounted on the vehicle. The on-board system  40  includes an operation input unit  42 , an image processor  44 , a front camera  52 , a right outer camera  54 , a left outer camera  56 , a rear camera  58 , an image data storage  62 , and a marker projector  64 . The operation input unit  42  is provided for allowing the driver  200  to operate the image display system  10 . The driver  200  can operate the operation input unit  42  to instruct whether or not an image is to be displayed on the wearable device  20 , and if displayed, which image is to be displayed on the wearable device  20 . Examples for displaying the image will be described further below. 
     The operation input unit  42  may be composed of buttons which are displayed on a touch panel disposed on an instrument panel, for example. Alternatively, the operation input unit  42  may be composed of mechanical buttons mounted on the instrument panel. Still alternatively, the operation input unit  42  may be provided to the wearable device  20 . 
     The image processor  44  is a device for generating an image which is displayed on the wearable device  20 . The image processor  44  may be implemented by controlling computer hardware incorporating a memory, a processor, and other components using software, such as an operating system (OS) and application programs. 
     The image processor  44  includes a three-dimensional map generator  45 , a device/pupil position calculator  46 , an image layout calculator  48 , and an image composition unit  50 . The three-dimensional map generator  45  acquires, from an image of a vehicle forward view obtained from the device position and attitude sensor  30  which is implemented by a camera, feature points of objects including road markings, such as white lines and arrows on a road surface, traffic signs, such as information signs and regulatory signs, and buildings standing along a roadway, and generates a three-dimensional map of the forward view. The device/pupil position calculator  46  calculates a relative position of the wearable device  20  within the vehicle and a relative position of the pupil of the driver  200  based on inputs from the device position and attitude sensor  30  and the pupil position sensor  32  (such as, for example, inputs of images captured by the camera as described above). 
     For image representation instructed from the operation input unit  42 , the image layout calculator  48  performs calculation to find which image is to be displayed at which position on the organic EL display  36 ; that is, calculation to determine a layout of images to be composed. To determine the layout, the image layout calculator  48  uses previously stored data of relative positions of interior components of the vehicle, and also uses data of the relative position and attitude of the wearable device  20  and the relative position of the pupil calculated in the device/pupil position calculator  46 . Using the data, the image layout calculator  48  is able to calculate which position on the organic EL display  36  is intersected by each of lines connecting the pupil of the driver  200  and points on a particular interior component of the vehicle. Then, the image layout calculator  48  calculates at which position a particular image should be displayed on the organic EL display  36  in order to allow the driver  200  to view the particular image overlaid on the particular interior component of the vehicle. In addition, the image layout calculator  48  also calculates a relative position of the wearable device  20  with respect to a position of an outside object existing ahead of the vehicle, the position being defined by the three-dimensional map generator  45 , and calculates a display position of the particular image on the organic EL display  36 . For example, in a case of a route guiding arrow displayed on the road surface, the image layout calculator  48  calculates at which position the route guiding arrow should be displayed on the organic EL display  36  in order to allow the driver  200  to view the route guiding arrow on the road surface. 
     The image composition unit  50  performs processing to compose images, for example, stored in the image data storage  62 , based on the layout calculated in the image layout calculator  48 . For the images to be composed, image data stored in the image data storage  62  are used as needed. Data of the composite images is transmitted to the image controller  34  and the composite images are displayed on the organic EL display  36 . Transmission of the composite image data may be performed through wired communication or wireless communication. When wireless communication is employed, short range wireless communication, such as, for example, Bluetooth (registered trademark) communication, Wi-Fi (registered trademark) communication, and infrared communication, may be utilized. 
     The front camera  52  is a camera for capturing an image of a forward area present ahead of the vehicle. The right outer camera  54  is disposed on a right side of the vehicle to capture an image of a rear area present behind the vehicle on its right side. The left outer camera  56  is disposed on a left side of the vehicle to capture an image of a rear area present behind the vehicle on its left side. The images captured by the right outer camera  54  and the left outer camera  56  are used as images displayed on electronic outer mirrors which can function as substitutes for an optical right outer mirror and an optical left outer mirror. The rear camera  58  is disposed at the widthwise center of the vehicle to capture an image of an area present behind the vehicle. The image captured by the rear camera  58  is used as an image displayed on an electronic inner mirror which can function as a substitute for an optical inner mirror (also referred to as a compartment mirror). 
     The image data storage  62  is a device which is implemented by means of a semiconductor memory, for example, and is controlled by the image processor  44 . The image data storage  62  stores data of images to be displayed on the wearable device  20 . The image data stored in the image data storage  62  include image data indicative of outer appearances of vehicle interior components. Specifically, the data may include data indicative of outer appearances of interior components, such as a door trim panel, a seat, and a roof ceiling, data indicative of mirror components, such as the electronic outer mirror, and the electronic inner mirror, and data indicative of guidance signs to be displayed within a forward view of the driver  200 . 
     The marker projector  64  projects a marker  66  having a predetermined shape shown in  FIG.  3    onto an area located ahead of the vehicle, in particular, onto a forward road surface using white light or light having a predetermined wavelength. The marker projector  64  may be incorporated into a head lamp.  FIG.  3    shows an example of the shape of the marker  66 . In this embodiment, the marker  66  includes a marker  66 A composed of three circles arranged at apexes of a triangle and a marker  66 B composed of a combination of two lateral line segments and one vertical line segment disposed beside the two lateral line segments. The marker  66 A may be projected from one of right and left head lights, and the marker  66 B may be projected from the other of the right and left head lights. A marker image is formed on the road surface by projecting the marker  66 , and the marker image is employed as a feature point which is used in creation of a three-dimensional map of an outside area. The shape of the marker  66  is stored in the image data storage  62 , and is retrieved into the three-dimensional map generator  45  and used therein when the three-dimensional map is created. 
     The on-board system  40  performs real time processing. Specifically, the on-board system  40  acquires detection data from the device position and attitude sensor  30  and the pupil position sensor  32  in the wearable device  20  at extremely short time intervals. The device/pupil position calculator  46  swiftly calculates, based on the acquired detection data, the position and attitude of the wearable device  20  and the position of the pupils. Then, the image layout calculator  48  calculates the layout of images instructed from the operation input unit  42 . The image composition unit  50  combines the images received from the image data storage  62  based on the calculated layout to generate a composite image, and transmits the composite image to the wearable device  20 . 
     In the wearable device  20 , the received composite image is processed in the image controller  34 , and displayed on the organic EL display  36 . Because all processes to achieve image representation are performed at high speed, it is possible to perform processing to rapidly follow motions of the driver  200 , such as, for example, processing to follow the driver  200  when they shake their head. Therefore, the driver  200  who wears the wearable device  20  can feel as if a vehicle compartment is actually present, the vehicle compartment being viewed through the wearable device  20  displaying the composite image that is different from reality. Further, the driver  200  is able to feel that an image displayed in a forward view of the driver  200  is a part of an actual landscape in front of the vehicle. 
     It should be noted that the wearable device  20  has been described with reference to the example wearable device including the image controller  34  and the organic EL display  36 , while the wearable device  20  may be implemented based on another principle. For example, the wearable device  20  may be embodied in a form incorporating a projector which projects an image onto the retina of the eye. Meanwhile, the wearable device  20  may be of a type which does not involve visible rays of light, and displays images captured by a camera. 
     The system configuration in  FIG.  1    is illustrated by way of example, and may be modified as appropriate. For example, a part of the configuration of the on-board system  40 , such as, for example, the operation input unit  42 , the image processor  44 , and the image data storage  62  may be mounted on the wearable device  20 . In this case, as the image data stored in the image data storage  62 , data of images corresponding to the vehicle used by the occupant who wears the wearable device  20  (such as, for example, data of images of each vehicle model) may be acquired through the Internet and stored by the occupant. 
     Next, examples of image representation performed by the wearable device  20  will be explained with reference to  FIGS.  4  and  5   .  FIGS.  4  and  5    are schematic diagrams showing a view seen by the driver  200  wearing the wearable device  20 . 
       FIG.  4    shows a view seen by the driver  200  in a state where the wearable device  20  is not used. In this state, the view seen by the driver  200  is identical to that seen with the naked eyes of the driver  200 . In the view of the driver  200 , interior components of the vehicle located in front of the driver  200  and a forward landscape outside the vehicle are present. 
     As the interior components of the vehicle, a roof ceiling  70  in an upper region of the view, and a left A pillar  72  (which is also referred to as a left front pillar) and a right A pillar  73  on the left and right sides of the roof ceiling  70  are contained in the view. In the view, a front wind shield  74  (also referred to as a front glass) is present in a region surrounded by the roof ceiling  70 , the left A pillar  72 , and the right A pillar  73 . The forward landscape outside the vehicle that can be seen through the front wind shield  74  is also contained in the view, the forward landscape which includes, in  FIG.  4   , a roadway  75  extending forward on a plain. The view also includes, at a position close to a top part of the front wind shield  74 , an inner mirror  76  attached to the roof ceiling  70 , and the inner mirror  76  reflects a vehicle traveling behind. 
     In the view, as the interior components, a left front door trim  78  and a right front door trim  79  are present on the left and right sides of the driver  200 . Further, a left outer mirror  82  is visible through a left side window glass  80 , and a right outer mirror  83  is visible through a right side window glass  81 . The left and right outer mirrors  82  and  83  reflect a part of a side surface of the driver  200 &#39;s own vehicle and a vehicle traveling behind. 
     An instrument panel  86  of the interior component is present below the wind shield  74  in the view. A touch panel  88  and operation buttons  90  are disposed on the instrument panel  86 . The operation input unit  42  of the wearable device  20  worn by the driver  200  is arranged, for example, on the touch panel  88  or the operation buttons  90 . 
     A steering wheel  92  is located before the instrument panel  86  toward the driver  200 . In addition, meters  94 , such as a speedometer, disposed on the instrument panel  86  are visible within the steering wheel  92  in the view. 
     An image  98  of the marker  66  (hereinafter, referred to as a marker image  98 ) that is projected from the marker projector  64  is present on a road surface  96  of the roadway  75  extending ahead of the vehicle. Because the marker image  98  is almost not moved relative to the vehicle in contrast to objects, such as a white line on the road surface  96 , being actually located outside the vehicle, a load of computation to extract the marker image  98  is lower than a load of computation to extract feature points of the objects located outside the vehicle. Further, because the road surface  96  of the roadway  75  on which the vehicle is present is, in most cases, on the same plane as the road surface  96  on which the marker image  98  is formed, the position of the marker image  98  is substantially fixed to the vehicle. For this reason, the position and attitude of the wearable device  20  relative to the vehicle can be determined from the position of the marker image  98  as in the case of the position and attitude of the wearable device  20  determined from the position of the interior compartment. 
       FIG.  5    shows a view seen by the driver  200 , in which images formed through operation of the operation input unit  42  by the driver  200  are displayed on the organic EL display  36  of the wearable device  20  so as to be overlaid on the interior components or the forward landscape. In the view of  FIG.  5   , outer appearances of interior components which are not directly connected to driving operation are modified. Specifically, colors and graphic patterns of the roof ceiling  70 , the left and right A pillars  72  and  73 , the left and right front door trim  78  and  79 , and the instrument panel  86  are modified. The wearable device  20  can modify at least one of properties consisting of colors, graphic patterns, and textures of the interior components using the image data stored in the image data storage  62 . Here, the texture denotes a property associated with a material and includes, for example, a metallic texture, a wooden texture, a leather texture, and a padding texture. 
     In  FIG.  5   , electronic mirrors are displayed on the organic EL display  36 . In the example of  FIG.  5   , an electronic left outer mirror  100 , an electronic inner mirror  102 , and an electronic right outer mirror  104  are displayed around an upper part of the steering wheel  92  in that order from the left of the driver  200 . 
     The electronic left outer mirror  100  is an image displayed on the organic EL display  36 , the image being obtained by capturing a landscape present behind the vehicle on its left side with the left outer camera  56 . On the electronic left outer mirror  100 , a part of the side surface of the driver  200 &#39;s own vehicle is displayed together with the vehicle traveling behind the driver  200 &#39;s own vehicle as in the case of the left outer mirror  82  which is an optical mirror. 
     The electronic inner mirror  102  is an image displayed on the organic EL display  36 , the image being obtained by capturing a landscape present behind the vehicle with the rear camera  58 . On the electronic inner mirror  102 , the vehicle traveling behind the driver  200 &#39;s own vehicle is displayed as in the case of the inner mirror  76 . 
     The electronic right outer mirror  104  is an image displayed on the organic EL display  36 , the image being obtained by capturing a landscape present behind the vehicle on its right side with the right outer camera  54 . On the electronic right outer mirror  104 , a part of the side surface of the driver  200 &#39;s own vehicle is displayed together with the vehicle traveling behind the driver  200 &#39;s own vehicle as in the case of the right outer mirror  83 . 
     The electronic left outer mirror  100 , the electronic inner mirror  102 , and the electronic right outer mirror  104  are displayed on the organic EL display  36  at positions which are viewed by the driver  200  around the upper part of the steering wheel  92  before the steering wheel  92 . When the electronic left outer mirror  100 , the electronic inner mirror  102 , and the electronic right outer mirror  104  are displayed so as to be seen in the upper part of the steering wheel  60 , the driver  200  can confirm the outside located behind the vehicle, almost without the need to shift a looking direction from a straight front direction. The electronic left outer mirror  100 , the electronic inner mirror  102 , and the electronic right outer mirror  104  are arranged at positions which are not overlaid on the forward view seen through the wind shield  74  or the meters  94 , to prevent impairment of forward visibility and viewability of the meters  94 . 
     Further, in  FIG.  5   , a guidance arrow  110  for guiding a route is displayed on the organic EL display  36  so as to be overlaid on the road surface  96  extending ahead of the vehicle. The guidance arrow  110  is displayed based on information from a route guidance device mounted on the vehicle. The guidance arrow  110  shown in  FIG.  5    indicates a direction of going straight ahead, while a turning left arrow or a turning right arrow is displayed at an appropriate position in an intersection where operation to turn left or right is required. 
     In a case where a sufficient amount of light is not obtained, for example, in the nighttime, or in a case where halation is created due to the presence of severe back-light, for example, positions of the interior components and equipment and positions of objects located outside the vehicle may not be properly identified from an image that is captured, for example, in the nighttime or against the sun by the wearable camera implemented as the device position and attitude sensor  30 . On the other hand, the marker image  98  which is formed by projecting light can be identified even in a dark environment, such as the nighttime. Because the position of the marker image  98  is substantially fixed to the vehicle as described above, when a relative position of the wearable device  20  with respect to the marker image  98  is found, a relative position of the wearable device  20  with respect to the interior component of the vehicle can be accordingly identified. Therefore, a display position of virtual representation applied to the interior component and the electronic mirror can be determined using the captured image of the marker mage  98 . As a result, the virtual representation can be displayed at an appropriate position on the organic EL display  36  even in a case where the amount of light is insufficient or halation is present. 
       FIG.  6    is a conceptual diagram showing a change in position and shape of a marker image caused by an inclined roadway. In  FIG.  6   , a flat roadway  75 H is indicated by a solid line, and an uphill roadway  75 R located ahead of the vehicle  120  is indicated by long and short dashed lines. An image of the marker  66 A (shown in  FIG.  3   ) that is projected onto a road surface  96 H of the flat roadway  75 H by the marker projector  64  is shown as a marker image  98 H, while an image of the marker  66 A projected onto a road surface  96 R of the uphill roadway  75 R is indicated as a marker image  98 R. The road surface  96 H is on the same plane as a road surface  96 V on which the vehicle  120  is presently located. 
       FIG.  7    shows captured images of the marker images  98 H and  98 R received from the wearable camera implemented as the device position and attitude sensor  30 . Because the wearable camera is located at a position higher than the marker projector  64 , the captured image of the marker image  98 R on the road surface  96 R of the uphill roadway  75 R is shrunk in the vertical direction and shifted to a position downward of the marker image  97 H on the road surface  96 H of the flat roadway  75 H. Such differences in shape and position between the marker images  98 R and  97 H in the captured image can be used for determining inclinations of the forward road surfaces  96 H and  96 R relative to the road surface  96 V on which the vehicle  120  is present. Meanwhile, on a downhill roadway, the captured image of the marker image is expanded in the vertical direction and shifted upward. 
     After the inclination of the forward road surface  96  is acquired, the guidance arrow  110  (see  FIG.  5   ) can be displayed so as to conform to the inclination of the road surface  96 . In this way, there can be prevented the situation that a tip end of the guidance arrow  110  is displayed in a manner that the tip end is viewed as sinking beneath the road surface  96  (in a case of the uphill roadway) or floating above the road surface  96  (in a case of the downhill roadway). 
     Projections and depressions on a road surface, such as speed bumps (a speed reducing zone) for urging drivers to decelerate the vehicle, can be detected based on deformation of the shape of the marker image  98 . In the speed bumps having a shape composed of alternating short uphill and downhill roadways, shrinking deformation due to the uphill roadway and expanding deformation due to the downhill roadway are alternatingly detected in succession at a short timer interval while the marker image  98  is moving through the speed reducing zone. In this case, the guidance arrow  110  may be displayed at positions conforming to the shape of the speed bumps, or an indication for urging the driver to decelerate may be displayed on the organic EL display  36 . 
     When the position and attitude of the wearable device  20  is acquired using the marker projected from the driver&#39;s own vehicle as described above, accuracy of the display position of the image on the wearable device  20  can be improved even when the external environment is deteriorated in terms of the amount of light, for example, in a dark environment or in an environment with severe back-light. 
     REFERENCE SIGNS LIST 
       10  image display system,  20  wearable device,  30  device position and attitude sensor (wearable camera),  32  pupil position sensor,  34  image controller,  36  organic EL display,  40  on-board system,  42  operation input unit,  44  image processor,  45  three-dimensional map generator,  46  device/pupil position calculator,  48  image layout calculator,  50  image composition unit,  62  image data storage,  64  marker projector,  66  marker,  70  roof ceiling,  72  left A pillar,  73  right A pillar,  74  wind shield,  75  roadway,  76  inner mirror,  82  left outer mirror,  83  right outer mirror,  86  instrument panel,  88  touch panel,  90  operation buttons,  92  steering wheel,  94  meters,  96  road surface,  98  marker image,  100  electronic left outer mirror,  102  electronic inner mirror,  105  electronic right outer mirror,  110  guidance arrow,  120  vehicle,  200  driver.