HEAD MOUNTED DISPLAY DEVICE

Abstract

In an aircraft HMD, a visor has toroidally-shaped portions respectively corresponding to left and right eyes of a user, and the toroidally-shaped portions are connected at a substantially central part between the user's eyes. The toroidally-shaped portions are aspherical shapes having a smaller curvature in a vertical direction than in a horizontal direction. Two sets of an image display section and a projection optical system are provided independently corresponding to the left and right toroidally-shaped portions. Due to the difference in curvature, a difference in optical power caused, for example, by a difference in incident angle on the reflecting surface is eliminated. This lessens astigmatism and allows display of an image with a wider visual field. An intermediate image is formed in both the vertical and horizontal directions within the projection optical system or in the middle of an optical path from the projection optical system to the reflecting surface.

Claims

1. A head mounted display device comprising: a support section mounted on a head of a user; a visor supported by the support section so as to be disposed in front of eyes of the user; a display section that forms a display image; and a projection optical system that projects display light containing information of the display image formed by the display section onto reflecting surfaces of the visor, wherein a virtual image based on the display image is created so as to be superposed on a view of an external scene visible through the visor, the reflecting surfaces of the visor are aspherical surfaces that bulge outward independently corresponding to the left and right eyes of the user and are connected to each other between the left and right eyes of the user, and two sets of the display section and the projection optical system are respectively provided corresponding to the left and right reflecting surfaces of the visor.

2. The head mounted display device according to claim 1, wherein an intermediate image is formed within the projection optical systems corresponding to the left and right reflecting surfaces or on optical paths from the projection optical systems to the corresponding reflecting surfaces; and the left and right reflecting surfaces each has an aspherical shape such that curvature in a Y-Z plane is smaller than curvature in a X-Z plane, where a central position between the left and right eyes of the user facing forward horizontally is defined as an origin O, an axis extending from the origin O toward a front side as viewed from the user is defined as a Z axis, an axis orthogonal to the Z axis and directed upward as viewed from the user is defined as a V axis, an axis orthogonal to both the Z axis and the Y axis is defined as an X axis, and where a point at which an optical axis of an incident light beam intersects with a corresponding one of the left and right reflecting surfaces of the visor is defined as an intersection point O, a normal to the left and right reflecting surfaces at the intersection point O is defined as a Z axis, an axis which is orthogonal to the Z axis and forms a plane with the Z axis on which plane both the optical axis of the incident light beam and an optical axis of an outgoing light beam reflected on the corresponding one of the left and right reflecting surfaces and is directed toward a corresponding eye of the user are present is defined as a Y axis, and an axis which is orthogonal to both the Y and Z axes is defined as an X axis.

3. The head mounted display device according to claim 2, wherein: the left and right reflecting surfaces each have an aspherical shape whose curvature in the Y-Z plane is smaller than the curvature in the X-Z plane by an amount corresponding to a difference in optical power due to a difference in the incident angle of the display light to the reflecting surface.

4. The head mounted display device according to claim 1, wherein: the visor has a surface layer formed on an inner surface or outer surface, the surface layer being made of a material different from a base material of the visor.

5. The head mounted display device according to claim 1, wherein: the projection optical systems respectively corresponding to the left and right reflecting surfaces each include at least one reflection mirror, and a reflecting surface of the reflection mirror has an aspherical shape.

6. The head mounted display device according to claim 5, wherein: the reflecting surface of the reflection mirror is a concave surface.

7. The head mounted display device according to claim 6, wherein: the reflection mirror is a back-surface reflection mirror having a refracting effect in addition to a reflecting effect.

8. The head mounted display device according to claim 7, wherein: the surface having the refracting effect has an aspherical shape.

9. The head mounted display device according to claim 1, wherein: the projection optical systems respectively corresponding to the left and right reflecting surfaces each include at least one lens having a refracting effect on both surfaces, and at least one surface of the lens has an aspherical shape.

10. The head mounted display device according to claim 9, wherein: the lens has a refractive index nd equal to or higher than 1.58.

11. The head mounted display device according to claim 1, wherein: the display section is configured to display information in two or more colors.

12. The head mounted display device according to claim 1, wherein: the display section and the projection optical system are arranged so that a principal ray corresponding to a center of a visual field of the display light emitted from the display section is emitted at an angle which is not orthogonal to the display surface of the display section.

13. The head mounted display device according to claim 1, wherein: the display section and the projection optical system are arranged so that a principal ray corresponding to a center of a visual field of the display light emitted from the display section is emitted from a position displaced from a center of the display surface of the display section.

14. The head mounted display device according to claim 1, wherein: the display section includes a transmission-type display element and a backlight illumination unit for illuminating the display element with light from behind.

15. The head mounted display device according to claim 1, wherein: the display section includes a reflection-type display element, an illumination section for emitting illumination light, and a reflection-type optical system configured to illuminate the display surface of the display element with the illumination light and to guide the light reflected by the display surface.

16. The head mounted display device according to claim 1, wherein: the display section includes a light-emitting display element.

17. The head mounted display device according to claim 1, wherein: the display section includes a small projector and a small screen.

18. The head mounted display device according to claim 17, wherein: the display section includes a transmission-type display element and a backlight illumination unit for illuminating the display element with light from behind, where at least a portion of the backlight illumination unit is a small projector.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0044] FIG. 1 is a schematic external view of an HMD according to an embodiment of the present invention.

[0045] FIGS. 2A and 2B are schematic configuration diagrams of an optical system in the HMD according to the present embodiment, where FIG. 2A is a schematic vertical-sectional view, and FIG. 2B is a schematic horizontal-sectional view.

[0046] FIG. 3 is a detailed configuration diagram of an optical path in the HMD according to the present embodiment.

[0047] FIG. 4 is a diagram showing a configuration example of a display section in the HMD according to the present embodiment.

[0048] FIG. 5 is a diagram showing another configuration example of the display section in the HMD according to the present embodiment.

[0049] FIG. 6 is a diagram showing another configuration example of the display section in the HMD according to the present embodiment.

[0050] FIGS. 7A and 7B are schematic configuration diagrams of an optical system including a visor in a conventional HMD, here FIG. 7A is a schematic vertical-sectional view, and FIG. 7B is a schematic horizontal-sectional view.

DESCRIPTION OF EMBODIMENTS

[0051] An HMD as one embodiment of the head mounted display device according to the present invention is hereinafter described with reference to the attached drawings.

[0052] FIG. 1 is a schematic external view of the HMD according to the present embodiment. FIGS. 2A and 2B are schematic configuration diagrams of an optical system in the HMD according to the present embodiment, where FIG. 2A is a schematic vertical-sectional view, and FIG. 2B is a schematic horizontal-sectional view. FIG. 3 is a more detailed configuration diagram of an optical path in FIG. 2A.

[0053] The HMD 1 according to the present embodiment is typically mounted on the head of a pilot operating an aircraft and is configured such that a visor 10 is attached to a helmet 2 that covers the head of a user H, leaving an open area in front of the face of the user H. The visor 10 is rotatable about an axis parallel to an X axis, which will be described later, and is attached to the helmet 2 so as to be slidable up and down. In addition to the helmet 2 and the visor 10, the HMD 1 according to the present embodiment includes an image display section 11 that forms a display image based on image data input from an image processing unit (not show) and a projection optical system 12 that projects display light including the display image as information onto a predetermined region of the visor 10.

[0054] As will be described later, the visor 10 has toroidally-shaped portions 10R and 10L respectively corresponding to left and right eyes ER and EL of the user, and the toroidally-shaped portions 10R and 10L are connected to each other at a substantially central part between the left and right eyes ER and EL so as to be integral with each other. Surfaces of the toroidally-shaped portions 10R and 10L that face the user H are a reflecting surface 10a. The reflecting surface 10a has a coating layer that reflects part of display light and allows part of light from an external world to pass through. This coating layer is made of a material different from the base material of the visor 10. For example, the base material of the visor 10 is polycarbonate, while the coating layer forming the reflecting surface 10a is made of a material selected from SiO, SiO.sub.2, Al.sub.2O.sub.3, MgO, Ta.sub.2O.sub.5, TiO.sub.2 and other compounds, or a combination of two or more of those compounds. The thickness of the visor 10, which varies depending on the kind of base material, normally falls within a range from 0.1 to 10 mm.

[0055] As shown in FIG. 2B, two sets of the image display section 11 and the projection optical system 12 are respectively provided on the left and right sides corresponding to the left and right toroidally-shaped portions 10R and 10L of the visor 10. The display section and the projection optical system for the right eye ER are respectively denoted by reference signs 11R and 12R, while the display section and the projection optical system for the left eye EL are respectively denoted by reference signs 11L and 12L.

[0056] Display light containing a display image formed by the image display section 11L exits from the projection optical system 12L, and is projected onto the reflecting surface 10a of the toroidally-shaped portion 10L of the visor 10. The thereby reflected light reaches the left eye EL of the user H. Meanwhile, display light containing a display image formed by the image display section 11R exits from the projection optical system 12R, and is projected onto the reflecting surface 10a of the toroidally-shaped portion 10R of the visor 10. The thereby reflected light reaches the left eye ER of the user H. A portion of the light coming from the external world and passing through the visor 10 also reaches the eyes EL and ER of the user H. Consequently, a virtual image of the display image is created in front of the eyes of the user H, being superposed on a view of the external scene.

[0057] For convenience of explanation, the X, Y and Z axes as well as the X, Y and Z axes in the present embodiment are defined as follows:

[0058] As shown in FIGS. 2 and 3, a central position between the left eye EL and right eye ER of the user H is defined as an origin O. An axis extending from the origin O toward the front side as viewed from the user H is defined as the Z axis. An axis orthogonal to the Z axis and directed upward as viewed from the user H is defined as the Y axis. An axis orthogonal to both the Z axis and the Y axis as well as extending in the left-outward direction as viewed from the user H is defined as the X axis. A point at which the optical axis C1 of a light beam emitted from the projection optical system 12 (12L or 12R) and reaching the visor 10 intersects with the reflecting surface 10a of the toroidally-shaped portion 101 or 10R of the visor 10 is defined as an intersection point O. An axis extending in the direction normal to the visor 10 at the intersection point O and directed outward as viewed from the user H is defined as the Z axis. An axis which is orthogonal to the Z axis and directed so as to form a Y-Z plane on which both the optical axis C1 of the light beat before being reflected by the visor 10 and the optical axis C2 of the light beam after the reflection are present is defined as the Y axis. An axis which is orthogonal to both the Y and Z axes is defined as the X axis, The intersection point O is present for each of the left and right eyes EL and ER. Therefore, the system of X, Y and Z axes is also present for each of the left and right eyes.

[0059] In the HMD according to the present embodiment, the toroidally-shaped portions 10L and 10R of the visor 10 each have a toroidal surface shape defined by the following equation (1).

z={square root over ((RxRy+{square root over (Ry.sup.2y.sup.2)}).sup.2x.sup.2)}[Equation 1]

[0060] Since this surface is toroidal, the curvature in the Y-axis direction at the intersection point O is different from the curvature in the X-axis direction. As will be described later, the former curvature is set to be smaller than the latter (i.e. the radius of curvature in the Y-axis direction is larger than the radius of curvature in the X-axis direction).

[0061] Although the reflecting surface of the visor 10 is a toroidal surface in this example, the reflecting surface of the visor 10 may have any shape, provided that the radius of curvature in the Y-axis direction is larger than the radius of curvature in the X-axis direction. For example, the reflection surface of the visor 10 may be an off-axis rotationally symmetric aspheric surface or a free-form surface.

[0062] A detailed configuration of the optical system in the HMD according to the present embodiment is hereinafter described.

[0063] The visor 10 is attached to the helmet 2 in such a manner that it is rotatable about an axis parallel with the X axis. As shown in FIGS. 2A and 3, when the visor 10 is completely lowered (i.e. when in use), upper portions of the toroidally-shaped portions 10R and 10L are in an inclined position tilting frontward in front of the eyes of the user H. Its inclination angle at the intersection point O (the angle formed by the vertical plane and the tangential plane to the reflecting surface 10a at the intersection point O) is equal to or larger than 10 degrees.

[0064] Note that the left and right axes of the visor 10 may be inclined with respect to each other (that is, the left and right Z axes are not parallel), and a portion of a virtual image of a display image observed by the user H may be visible to only one eye.

[0065] As shown in FIG. 3. the image display section 11 includes a transmission-type display element 112, such as a transmission-type color liquid crystal display element, and a backlight illumination unit 111. The light emitted from the backlight illumination unit 111 passes through the display surface of the transmission-type display element 112, whereby an image formed on the display surface of the transmission-type display element 112 is emitted as display light. This image is completely symmetrical (i.e. plane-symmetrical with respect to the Y-Z plane). The projection optical system 12 includes a plurality of lenses 121, a back-surface reflection mirror 122 (122L or 122R) with a concave reflection surface, and a flat mirror 123. This is also completely symmetrical.

[0066] The display light emitted from the image display section 11 passes through the lenses 121 and reaches the back-surface reflection mirror 122. Then, the light is refracted at a refraction surface 122a on the incident side of the back-surface reflection mirror 122 and subsequently reaches a reflection surface 122b, to be reflected by the reflection surface 122b while being focused. The reflected light is once more reflected by the flat mirror 123 into the direction toward the reflecting surface 10a of the toroidally-shaped portion 10R or 10L of the visor 10. Due to the focusing effect of the reflection surface 122b of the back-surface reflection mirror 122, the reflected light temporarily forms an intermediate image on the optical path between the flat mirror 123 and the reflecting surface 10a. The imaging plane on which the intermediate image is formed is denoted by reference sign Q in FIG. 3. At this plane, the intermediate image is formed in both the vertical direction (i.e. in a plane parallel to the Y-Z plane) and the horizontal direction (i.e. in a plane parallel to the X-Z plane). It should be noted that the intermediate image may be formed within the projection optical system 12 including the flat mirror 123 instead of being formed on the optical path between the flat mirror 123 and the reflecting surface 10a.

[0067] As shown in FIG. 3, the optical axis of the display light emitted from the image display section 11 and incident on the lenses 121 of the projection optical system 12 is not orthogonal to the display surface of the transmission-type display element 112 of the image display section 11. In other words, the configuration of a non-coaxial optical system is adopted. Therefore, a display image which is asymmetrically blurred is formed. To address this problem, at least one of the refraction surface 122a and reflection surface 122b of the hack-surface reflection mirror 122, or the lenses 121, are given an aspherical shape so as to correct the aforementioned blurring of the display image.

[0068] The display light emitted from the projection optical system 12, or more exactly, the display light which travels from the imaging plane Q of the intermediate image while gradually expanding, hits the reflecting surface 10a of the visor 10 and is reflected by the concave surface while being focused. The incident angle of the optical axis of the incident light in the Y-Z plane is not the same as that of the optical axis of the incident light in the X-Z plane. Therefore, if the reflection surface were spherical, a difference in optical power would occur between these two planes and cause astigmatism. To avoid this problem, in the HMD according to the present embodiment, the curvature of the reflecting surface 10a in the Y-Z plane is made to be smaller than the curvature in the X-Z plane by an amount corresponding to the aforementioned difference in the incident angle of the optical axis of the incident light so that the optical power will be almost equal in both planes.

[0069] Since the optical power is made to be almost equal in both the Y-Z plane and the plane, the problem of astigmatism is practically eliminated when the beams of display light respectively reach the eyes EL and ER. Accordingly, the user H can observe a display image with a wide visual field in the form of a virtual image in both the vertical and horizontal directions.

[0070] The configuration of the image display section 11 or projection optical system 12 in the HMD according to the previously described embodiment can be appropriately changed.

[0071] FIGS. 4 through 6 are schematic diagrams each of which shows a different configuration example of the display section.

[0072] The image display section 11A shown in FIG. 4 includes an illumination section 11A1, a reflection-type display element 11A2 (e.g. reflection-type color liquid crystal display element), as well as a reflection-type optical element 11A3 including a beam splitter and other related components. The light emitted from the illumination section 11A1 is reflected by the reflection-type optical element 11A3 and directed toward the reflection-type display element 11A2. When reflected by the display surface of the reflection-type display element 11A2, the light receives image information formed on the display surface and is eventually emitted through the reflection-type optical element 11A3 to the outside as the display light.

[0073] The image display section 11B shown in FIG. 5 includes a light-emitting display element 11B1, such as an organic electroluminescent display. According to this configuration, it is unnecessary to provide a separate illumination section, since the light-emitting display element 11B1 itself emits light and produces display light.

[0074] The image display section 11C shown in FIG. 6 includes a small projector 11C1 and a small screen 11C2. The display light emitted from the small projector 11C1 is projected onto the small screen 11C2 and forms an enlarged version of the display image on the small screen 1102. The display image on this small screen 11C2 is directly emitted as the display light.

[0075] In the configuration of the previously described embodiment shown in FIG. 3, a display image which is effectively a colored image or an image with two or more colors can be created by using a monochromatic display element as the transmission-type display element 112 and a small projector emitting colored light or light with two or more colors as the backlight illumination unit 111.

[0076] The previously described embodiment is a mere example of the present invention. Its variations are not limited to the already described ones. Any change, modification or addition appropriately made within the spirit of the present invention will naturally fall within the scope of claims of the present application.

REFERENCE SIGNS LIST

[0077] 2 . . . Helmet [0078] 10 . . . Visor [0079] 10L, 10R . . . Toroidally-shaped portion [0080] 10a . . . Reflecting surface [0081] 11A1 . . . Illumination section [0082] 11A2, 11A3 . . . Reflection-type display element [0083] 11B1 . . . Light-emitting display element [0084] 11C1 . . . Small projector [0085] 11C2 . . . Small screen [0086] 111 . . . Backlight Illumination Unit [0087] 112 . . . Transmission-Type Display Element [0088] 11(11L, 11R), 11A, 11B, 11C . . . image Display Section [0089] 12L, 12R . . . Projection Optical System [0090] 121 . . . Lens [0091] 122 . . . Back-Reflection Mirror [0092] 122a . . . Refraction Surface [0093] 122b . . . Reflection Surface [0094] 123 . . . Flat Mirror [0095] H . . . User [0096] EL . . . Left Eye [0097] ER . . . Right Eye