Patent Description:
Patent Literature <NUM> discloses a head-mounted display in which a beam splitter having a curved surface is used. The head-mounted display of Patent Literature <NUM> includes a nasal ridge piece that separates fields of view of both eyes. The nasal ridge piece is a vertical bar or wall that separates two surfaces.

Patent Literature <NUM> discloses a method of presenting the user with a picture from the screen of a smart phone or tablet at a wide angle of view, consisting in that fixing a smart phone or tablet on the head in front of user's eyes, mounting the smart phone screen in front of the user's eyes to the line of sight at a distance of <NUM>- <NUM> centimeters from the eyes to provide a wide angle of view at <NUM>-<NUM> degrees, providing an optical means for obtaining an image sharpness between the smart phone screen and at least one of user's eyes, displaying an image on the screen of smart phone or tablet, which is the one selected from the group consisting of individual images, videos, virtual space, or other applications, providing the user with a means for controlling the smart phone or tablet.

Patent Literature <NUM> discloses a head mounted display (HMD) device including a housing coupled to a frame, and a display device disposed in the housing. A divider may be positioned between the first lens and the second lens, with a front end portion of the divider positioned adjacent to the display device. The divider may include display capability so that images displayed on the display device may extend onto the divider. The divider may emit diffused light having chrominance and/or luminance levels corresponding to images displayed on the display device. The divider may reflect diffused light from images displayed on the display device. The divider may transmit diffused light from images displayed on the display device.

Patent Literature <NUM> discloses a display apparatus with an image generator that generates image-bearing light from a f surface and a lens spaced apart from the image generator and having an aspheric incident refractive surface concave to the image generator and having an aspheric reflective surface concave to the image generator, wherein a principal axis of the reflective surface is normal to the image generator. A beam splitter plate disposed in free space between the image generator and the lens has first and second parallel surfaces that are oblique to a line of sight of a viewer. The lens and the beam splitter plate define a viewer eye box for the image-bearing light along the line of sight of the viewer.

As described above, the head-mounted display is provided with an optical system for guiding display light from a display element to each of left and right eyes. For example, the head-mounted display includes a left-eye display element, a left-eye optical system, a right-eye display element, and a right-eye optical system.

However, the head-mounted display has a problem that a noise component called crosstalk light where display light from a right-eye display element enters the left eye, for example, occurs, which causes degradation of display quality. Particularly, the effect of crosstalk increases in a case where the optical system is enlarged in order to increase the viewing angle in the left-right direction. The crosstalk means that display light from the left or right display element each enters the eye different from the intended eye. This is described with reference to <FIG> is a top view schematically showing the structure of a display element and an optical system.

A beam splitter <NUM> and a combiner <NUM> are arranged in front of the left eye EL. Likewise, a beam splitter 122R and a combiner 121R are arranged in front of the right eye ER. Display light PL11 from a left-eye display element <NUM> arranged above the beam splitter <NUM> is reflected by the beam splitter <NUM> and enters the combiner <NUM>. The display light PL11 that has been reflected by the combiner <NUM> passes through the beam splitter <NUM> and enters the left eye EL.

However, part of the display light PL11 that has been reflected by the combiner <NUM> enters the right eye ER as crosstalk light PCT. Likewise, part of display light PR11 from a right-eye display element 101R enters the left eye EL as crosstalk light, though not shown in <FIG>. When part of the display light PL11 or PR11 from the left or right display element enters the eye on the opposite side as crosstalk light PCT, it acts as a noise component of a display image. This reduces contrast and produces a double image or the like, which may cause degradation of display quality. Patent Literature <NUM> reduces crosstalk, but has a problem that high display quality cannot be obtained as the vertical bar or wall that separates the two surfaces are emphasized.

The present disclosure has been accomplished to solve the above problems and an objective of the present disclosure is to provide a head-mounted display with high display quality.

A head-mounted display according to an embodiment includes a reflective member arranged in front of a user, and configured to reflect display light for forming a display image toward the user, and a divider part arranged between a space in front of a left eye of the user and a space in front of a right eye, and configured to diffusely reflect the display light.

According to the present disclosure, a head-mounted display with high display quality can be provided.

Specific embodiments of the present invention are described hereinafter in detail with reference to the drawings. The present disclosure, however, is not limited to the below-descried embodiments. The following description and the attached drawings are appropriately simplified to clarify the explanation.

A head-mounted display and a display method of the same according to an embodiment are described hereinafter with reference to the drawings. <FIG> is a perspective view schematically showing a part of a structure of a head-mounted display <NUM>. <FIG> is a view showing some of functional blocks of the head-mounted display <NUM>. <FIG> and <FIG> mainly show a structure related to image display of the head-mounted display <NUM>. <FIG> shows the internal structure of the head-mounted display <NUM>, and the elements shown in <FIG> may be covered with a cover or the like in practice.

The head-mounted display <NUM> is applicable to various purposes, such as game, entertainment, industrial, medical, and flight simulation purposes. The head-mounted display <NUM> may be a VR (Virtual Reality) head-mounted display, an AR (Augmented Reality) head-mounted display, or an MR (Mixed Reality) head-mounted display, for example. Note that the head-mounted display <NUM> is an optical see-through head-mounted display used for AR or MR in this embodiment, but may be a non-transmissive head-mounted display.

To clarify the explanation, an XYZ three-dimensional Cartesian coordinate system is used in the following description. As seen from a user, the front-back direction (depth direction) is Z direction, the left-right direction (horizontal direction) is X direction, and the up-down direction (vertical direction) is Y direction. The front direction is +Z direction, the back direction is -Z direction, the right direction is +X direction, the left direction is -X direction, the up direction is +Y direction, and the down direction is -Y direction.

The user, which is not shown, is wearing the head-mounted display <NUM>. The head-mounted display <NUM> includes a display element unit <NUM>, a frame <NUM>, a left-eye optical system <NUM>, a right-eye optical system 103R, and a control unit <NUM>. The control unit <NUM> includes a control unit <NUM> and a control unit 105R.

The frame <NUM> has goggles or glasses shape, and it is worn on the head of the user by a head band, which is not shown, or the like. The display element unit <NUM>, the left-eye optical system <NUM>, the right-eye optical system 103R, the control unit <NUM>, and the control unit 105R are mounted on the frame <NUM>. Note that, although the binocular head-mounted display <NUM> is shown in <FIG>, the head-mounted display may be a glasses-shaped non-immersive head-mounted display.

The display element unit <NUM> includes a left-eye display element <NUM> and a right-eye display element 101R. The left-eye display element <NUM> generates a display image for a left eye. The right-eye display element 101R generates a display image for a right eye. Each of the left-eye display element <NUM> and the right-eye display element 101R includes a flat-panel display such as a liquid crystal monitor or an organic EL (Electro-Luminescence) monitor. The left-eye display element <NUM> and the right-eye display element 101R may be curve-shaped displays. Each of the left-eye display element <NUM> and the right-eye display element 101R includes a plurality of pixels arranged in an array. The array arrangement is not limited to two-dimensional matrix arrangement, and it may be PenTile arrangement or the like. The left-eye display element <NUM> is arranged on the left side (-X side) of the right-eye display element 101R.

The control unit <NUM> is provided above (on the +Y side) the display element unit <NUM>. A video signal, a control signal, and power from the outside are supplied to the control unit <NUM>. For example, a video signal and the like are input to the control unit <NUM> by wired connection such as HDMI (registered trademark) or wireless connection such as WiFi (registered trademark) or BlueTooth (registered trademark). The head-mounted display <NUM> may include a video generation unit (not shown) that generates a video signal, and a video signal or the like generated by the video generation unit may be input to the control unit <NUM>.

The control unit <NUM> and the control unit 105R include hardware resources such as a CPU (Central Processing Unit), a memory and the like, and operates according to a computer program stored in the memory. Further, each of the control unit <NUM> and the control unit 105R includes a display driving circuit or the like. The control unit <NUM> generates a display signal of a left-eye image on the basis of a video signal, a control signal and the like and outputs it to the left-eye display element <NUM>. The left-eye display element <NUM> thereby outputs display light for displaying the left-eye image. The control unit 105R generates a display signal of a right-eye image on the basis of a video signal, a control signal and the like and outputs it to the right-eye display element 101R. The right-eye display element 101R thereby outputs display light for displaying the right-eye image. In this manner, the control unit <NUM> outputs display signals to the display element unit <NUM>.

Note that the display element unit <NUM> does not necessarily have the structure in which the left-eye display element <NUM> and the right-eye display element 101R are separate display elements, and it may have a single display element. The single display element may generate a display image for a left eye and a display image for a right eye. In this case, the display element unit <NUM> generates a left-eye image by using a part on one side of the display area of the display and generates a right-eye image by using a part on the other side of the display area of the display.

Some or all of the display element unit <NUM>, the control unit <NUM> and the like are not necessarily fixed to the frame <NUM>, and they may be mounted detachable from the frame <NUM>. For example, the display element unit <NUM>, the control unit <NUM> and the like may be implemented by mounting a smartphone or a tablet computer on the frame <NUM>. In this case, an application program (app) that generates display images for the head-mounted display is previously installed into the smartphone or the like.

The left-eye optical system <NUM> guides the display light that is output from the left-eye display element <NUM> to the left eye EL of the user as a left-eye image. The right-eye optical system 103R guides the display light that is output from the right-eye display element 101R to the right eye ER of the user as a right-eye image. The left-eye optical system <NUM> is arranged on the left side (-X side) of the right-eye optical system 103R. The left-eye optical system <NUM> is arranged in front (+Z direction) of the left eye EL of the user. The right-eye optical system 103R is arranged in front (+Z direction) of the right eye ER of the user. The user is able to see a virtual image of a display image generated by the display element unit <NUM> in the front (in the +Z direction).

As described above, the head-mounted display <NUM> according to this embodiment may either be a semitransparent or non-transmissive head-mounted display. Note that the description herein is provided assuming that the head-mounted display <NUM> is a semitransparent head-mounted display. Thus, the left-eye optical system <NUM> and the right-eye optical system 103R include a combiner, which is described later. In the semitransparent head-mounted display <NUM>, display light from the display element unit <NUM> and outside light enter the left eye EL and the right eye ER. Thus, the user is able to see a superimposed image on which a display image is superimposed on a view in the front (in the +Z direction).

An example of the left-eye optical system <NUM> and the right-eye optical system 103R (which are collectively referred to simply as an optical system below) is described hereinafter. <FIG> is a side view schematically showing the optical system. Note that the left-eye optical system <NUM> and the right-eye optical system 103R have the same structure, and therefore only the left-eye optical system <NUM> is described with reference to <FIG>.

The left-eye optical system <NUM> includes a combiner <NUM>, a beam splitter <NUM>, and a light shielding part <NUM>. The combiner <NUM>, the beam splitter <NUM>, and the light shielding part <NUM> are fixed to the frame <NUM> shown in <FIG>.

The combiner <NUM> is a concave mirror, and the beam splitter <NUM> is a plane mirror. The combiner <NUM> and the beam splitter <NUM> are beam splitters such as half-mirrors, and reflect part of incident light and transmit part of incident light. When it is assumed that the percentage of reflection and the percentage of transmission in the combiner <NUM> are equal, the combiner <NUM> transmits approximately half of the amount of incident light, and reflects the remaining half. Likewise, when it is assumed that the percentage of reflection and the percentage of transmission in the beam splitter <NUM> are equal, the beam splitter <NUM> transmits approximately half of the amount of incident light, and reflects the remaining half. The combiner <NUM> and the beam splitter <NUM> may increase the percentage of reflection and decrease the percentage of transmission, or may decrease the percentage of reflection and increase the percentage of transmission.

The combiner <NUM> and the beam splitter <NUM> are arranged in front (+Z direction) of the user's left eye EL. Further, the combiner <NUM> is arranged in front (+Z direction) of the beam splitter <NUM>.

The left-eye display element <NUM> is arranged above (in the +Y direction) the beam splitter <NUM>. The left-eye display element <NUM> outputs the display light PL11 for forming a display image. Thus, the left-eye display element <NUM> is arranged diagonally above in front of the left eye EL.

The light shielding part <NUM> is arranged below (in the -Y direction) the beam splitter <NUM>. Thus, the light shielding part <NUM> is arranged diagonally below in front of the left eye EL. The light shielding part <NUM> is provided to shield a field of vision in the diagonally lower front. The light shielding part <NUM> is formed of a black material or the like that absorbs light. A lower window for viewing the diagonally lower front may be provided instead of the light shielding part <NUM>.

The display light PL11 from the left-eye display element <NUM> is described hereinafter. The display surface of the left-eye display element <NUM> faces downward (in the -Y direction). Thus, the display light PL11 from the left-eye display element <NUM> is output downward (in the -Y direction). The beam splitter <NUM> is arranged at an angle below (in the -Y direction) the left-eye display element <NUM>. The display light PL11 from the left-eye display element <NUM> enters the beam splitter <NUM>. The beam splitter <NUM> reflects part of the display light PL11. The remaining part of the display light PL11 that has passed through the beam splitter <NUM> is absorbed by the light shielding part <NUM>.

The display light PL11 that has been reflected by the beam splitter <NUM> is reflected forward (in the +Z direction). Then, the display light PL11 enters the combiner <NUM>. The combiner <NUM> reflects part of the display light PL11 backward (in the -Z direction). The display light PL11 that has been reflected by the combiner <NUM> is referred to as display light PL12. Further, the combiner <NUM> is a concave mirror, and reflects the display light PL11 so as to focus the display light PL12 toward the left eye EL. The display light PL12 that has been reflected by the combiner <NUM> enters the beam splitter <NUM>. The beam splitter <NUM> transmits part of the display light PL12.

The display light PL12 that has passed through the beam splitter <NUM> enters the left eye EL. In this manner, the left-eye optical system <NUM> guides the display light PL11 from the left-eye display element <NUM> to the user's left eye EL. The optical system can display the virtual image in front (in the +Z direction) of the user. Further, since a concave mirror is used as the combiner <NUM>, the display image is displayed in a larger scale.

The outside light PL21 from the front (+Z direction) of the user is described hereinafter. Part of the outside light PL21 passes through the combiner <NUM>. The outside light PL21 that has passed through the combiner <NUM> enters the beam splitter <NUM>. The beam splitter <NUM> transmits part of the outside light PL21. The outside light PL21 that has passed through the beam splitter <NUM> enters the left eye EL.

Since the head-mounted display <NUM> is semitransparent, the combiner <NUM> combines the outside light PL21 from the front (+Z direction) and the display light PL11 from the left-eye display element <NUM>. The right-eye optical system 103R is the same as the left-eye optical system <NUM>. The combiner 121R combines outside light PR21 from the front (in the +Z direction) and the display light PR11 from the right-eye display element 101R. By arranging the combiners <NUM> and 121R in front (in the +Z direction) of the user, the head-mounted display <NUM> functions as an optical see-through display. A display image is superimposed on a view in front (in the +Z direction) of the user. The user is thereby able to see a view on which the display image is superimposed.

The structure for reducing crosstalk is described hereinafter with reference to <FIG> and <FIG>. <FIG> is a top view schematically showing the optical system, and <FIG> is a side sectional view. As shown in <FIG> and <FIG>, a divider part <NUM> is provided between the left-eye optical system <NUM> and the right-eye optical system 103R.

The divider part <NUM> is arranged between a space in front (in the +Z direction) of the left eye EL (which is referred to as the left front space <NUM> below) and a space in front (in the +Z direction) of the right eye ER (which is referred to as the right front space 160R below). The left front space <NUM> and the right front space 160R are divided by the divider part <NUM>. The divider part <NUM> defines the boundary between the left front space <NUM> and the right front space 160R in the X direction.

Note that the left front space <NUM> is a space defined by the combiner <NUM>, the left-eye display element <NUM>, the light shielding part <NUM>, the divider part <NUM>, the frame <NUM> (see <FIG> together), and the user's face. Thus, the front side (in the +Z direction) of the left front space <NUM> faces the combiner <NUM>, and the rear side (in the -Z direction) faces the user's face. The upper side (in the +Y direction) of the left front space <NUM> faces the left-eye display element <NUM>, and the lower side (in the -Y direction) faces the light shielding part <NUM>. The right side (in the +X direction) of the left front space <NUM> faces the divider part <NUM>, and the left side (in the -X direction) faces the frame <NUM>.

Likewise, the right front space 160R is a space defined by the combiner 121R, the right-eye display element 101R, the light shielding part 150R, the divider part <NUM>, the frame <NUM> (see <FIG> together), and the user's face. Thus, the front side (in the +Z direction) of the right front space 160R faces the combiner 121R, and the rear side (in the -Z direction) faces the user's face. The upper side (in the +Y direction) of the right front space 160R faces the right-eye display element 101R, and the lower side (in the -Y direction) faces the light shielding part 150R. The right side (in the +X direction) of the right front space 160R faces the frame <NUM>, and the left side (in the -X direction) faces the divider part <NUM>.

The divider part <NUM> is arranged in front of and behind the beam splitters <NUM> and 122R. To be specific, the divider part <NUM> is arranged between the beam splitters <NUM> and 122R from in front (in the +Z direction) of the beam splitters <NUM> and 122R to behind (in the -Z direction) the beam splitters <NUM> and 122R. The divider part <NUM> is a diffuse reflection plate, which diffusely reflects visible light. Diffuse reflection means a diffuse reflection component of light reflection excluding specular reflection. The divider part <NUM> diffusely reflects incident outside light and display light in various directions. Note that the divider part <NUM> may not divide the left front space <NUM> and the right front space 160R completely. In other words, the left front space <NUM> and the right front space 160R may be connected partially.

The divider part <NUM> blocks the display light PL11 and PL12 from the left-eye display element <NUM> from entering the right eye ER. The divider part <NUM> also blocks the display light PR11 from the right-eye display element 101R and the display light PR12 which is the display light PR11 that has been reflected by the combiner 121R from entering the left eye EL. In other words, the divider part <NUM> blocks the crosstalk light PCT shown in <FIG>. This reduces crosstalk, and improves display quality.

Further, since the divider part <NUM> is a diffuse reflection plate, part of light that has entered the divider part <NUM> reaches the left eye EL or the right eye ER. For example, part of the outside light PL21 that has passed through the combiner <NUM> is diffusely reflected by the divider part <NUM> and enters the left eye EL. Further, part of the display light PL11 and PL12 from the left-eye display element <NUM> is diffusely reflected by the divider part <NUM> and enters the left eye EL. Part of the outside light PR21 that has passed through the combiner 121R is diffusely reflected by the divider part <NUM> and enters the right eye ER. Further, part of the display light PR11 and PR12 from the right-eye display element 101R is diffusely reflected by the divider part <NUM> and enters the right eye ER.

Thus, this embodiment prevents the divider part <NUM> from being seen as a black shadow by the user, as compared with a case in which the divider part <NUM> is a non-diffuse reflection plate. In other words, the divider part <NUM> diffusely reflects light in such a way that the divider part <NUM> does not stand out. Note that the non-diffuse reflection plate refers to a resin plate colored black, for example.

Diffuse reflectance of the divider part <NUM> is adjusted in such a way that the divider part <NUM> does not become excessively bright or excessively dark to stand out. The diffuse reflectance refers to the percentage of the amount of diffusely reflected light in the amount of incident light, and represents color brightness. The diffuse reflectance is adjusted by a color that colors the divider part <NUM> and treatment to be performed on the surface of the divider part <NUM>. The diffuse reflectance of the divider part <NUM> preferably falls within a range that is not close to <NUM>% at which the divider part <NUM> becomes excessively bright and that is not close to <NUM>% at which the divider part <NUM> becomes excessively dark. This allows the user to naturally see the display image, which improves display quality.

In order that the divider part <NUM> has appropriate diffuse reflectance so as not to stand out, a resin plate colored gray or the like is used for the divider part <NUM>, for example. Gray refers to colors except white whose mixing ratio is <NUM>% white and black whose mixing ratio is <NUM>% black among achromatic colors which are mixed colors of white and black. Gray also includes a color whose mixing ratio is <NUM>% white and <NUM>% black, and a color whose mixing ratio is <NUM>% white and <NUM>% black. In other words, the divider part <NUM> is colored by a color which is neither white nor black.

Alternatively, by forming the divider part <NUM> with diffuse reflection treatment performed on its surface, the divider part <NUM> has appropriate diffuse reflectance so as not to stand out. The diffuse reflection treatment refers to rubbing a resin surface with sandpaper or the like to roughen the resin surface so as to have fine irregularities, for example. Herein, the surface of the divider part <NUM> refers to the surface that faces the left front space <NUM> and the surface that faces the right front space 160R.

Irrespective of brightness or darkness of the divider part <NUM>, the divider part <NUM> may have substantially the same color as the user's skin color such as the user's skin tone so as not to stand out. The user's skin color indicates all colors that may generally be recognized as skin tones, and can be changed as appropriate according to the skin tone of a race. The user's skin color may be a color that falls within a range in which <NUM> ≤ x ≤ <NUM> and <NUM> ≤ y ≤ <NUM> held on the CIE chromaticity diagram, for example. The skin color in a case where the user is the Caucasoid race may be a color that falls within a range in which <NUM> ≤ x ≤ <NUM> and <NUM> ≤ y ≤ <NUM> held on the CIE chromaticity diagram. The skin color in a case where the user is the Mongoloid or Negroid race may be a color that falls within a range in which <NUM> ≤ x ≤ <NUM> and <NUM> ≤ y ≤ <NUM> held on the CIE chromaticity diagram. When the divider part <NUM> has the same type of color as the skin color, the divider part <NUM> blends in with the nose and is seen like part of the nose, which improves display quality.

Since the divider part <NUM> is a diffuse reflection plate, the user is able to see a display image without the divider part <NUM> being emphasized. This increases display quality. Further, since display light that has entered the divider part <NUM> is also diffusely reflected, part of a display image is prevented from being formed by display light that has been reflected by the divider part <NUM>. This increases display quality.

Note that the divider part <NUM> is formed of a thin plate whose thickness direction is the left-right direction (the X direction). The shape of the divider part <NUM> on the Y-Z plane is determined in accordance with the shape of the left front space <NUM> and the right front space 160R. Note that the end sides of the diffuse reflection plate to be the divider part <NUM> are shaped along the display element unit <NUM>, the light shielding parts <NUM>, 150R, and the combiners <NUM>, 121R. As shown in <FIG>, an end side of the divider part <NUM> in the front (in the +Z direction) is formed along the curves of the combiners <NUM> and 121R. In other words, the end side of the divider part <NUM> in the front (in the +Z direction) is formed as an arc. This allows the left front space <NUM> and the right front space 160R to be divided properly, which allows crosstalk to be reduced effectively.

The head-mounted display <NUM> according to this embodiment is described with reference to <FIG> and <FIG>. In this embodiment, left and right beam splitters <NUM> are formed integrally. In other words, the beam splitter <NUM> and the beam splitter 122R are implemented by a single beam splitter <NUM>. The beam splitter <NUM> is arranged across the left front space <NUM> and the right front space 160R.

The left-eye optical system <NUM> and the right-eye optical system 103R share the beam splitter <NUM>. This prevents misalignment of virtual images between the left-eye optical system <NUM> and the right-eye optical system 103R. In other words, when the beam splitter <NUM> and the beam splitter 122R are arranged at an angle in the structure in which the beam splitter <NUM> and the beam splitter 122R are provided separately as in the first embodiment, left and right virtual images are displayed in a manner misaligned from each other in the up-down direction (the Y direction). Since this embodiment prevents virtual images from being misaligned in the up-down direction (the Y direction), high display quality is obtained.

The left-eye optical system <NUM> and the right-eye optical system 103R share the single beam splitter <NUM>. Thus, the divider part <NUM> cannot be arranged between the left and right beam splitters <NUM> and 122R as in the first embodiment. In this embodiment, the divider part <NUM> is implemented by two divider plates <NUM> and <NUM>. The divider part <NUM> is implemented by the single divider plate in the first embodiment, whereas in the second embodiment, the divider part <NUM> is implemented by the two divider plates <NUM> and <NUM>. The divider plate <NUM> is arranged in front (in the +Z direction) of the beam splitter <NUM>. The divider plate <NUM> is arranged behind (in the -Z direction) the beam splitter <NUM>.

The divider plates <NUM> and <NUM> are diffuse reflection plates, each of which diffusely reflects light. The divider plates <NUM> and <NUM> are formed of resin plates colored gray or colored by a skin color. Further, the divider plates <NUM> and <NUM> are formed with diffuse reflection treatment performed on their surfaces. Herein, the surfaces of the divider plate <NUM> and the divider plate <NUM> refer to the surface that faces the left front space <NUM> and the surface that faces the right front space 160R. Since the divider part <NUM> can divide the left front space <NUM> and the right front space 160R, crosstalk is reduced. Effects similar to those of the first embodiment are thereby obtained.

According to the invention the divider plate <NUM> and the divider plate <NUM> are different in values of diffuse reflectance. This is described with reference to <FIG> is a view for describing the amount of outside light diffusely reflected by the divider plates <NUM> and <NUM>. Note that the left-eye optical system <NUM> and the right-eye optical system 103R have the same structure, and therefore only the left-eye optical system <NUM> is described hereinafter.

Description is provided with reference to <FIG> assuming that approximately <NUM>% of outside light that has been diffusely reflected by the divider plates <NUM> and <NUM> travels to the left eye EL. In other words, it is supposed that approximately <NUM>/<NUM> of outside light that has entered the divider plates <NUM> and <NUM> is reflected toward the left eye EL at either a location C on the divider plate <NUM> or a location D on the divider plate <NUM>. It is also supposed that the transmittance of the combiner <NUM> and the beam splitter <NUM> is <NUM>% and the reflectance is <NUM>%.

The outside light PL211 to be diffusely reflected by the divider plate <NUM> before entering the beam splitter <NUM> is described first. The outside light PL211 that has passed through the combiner <NUM> enters the divider plate <NUM> at the location C. Herein, when it is assumed that the amount of the outside light PL211 before entering the combiner <NUM> is <NUM>, the amount of the outside light PL211 that has passed through the combiner <NUM> is <NUM> (= <NUM> × <NUM>).

Then, part of the outside light PL211 that has been diffused at the location C passes through the beam splitter <NUM> and enters the left eye EL. The amount of the outside light PL211 that has been diffused at the location C and travels toward the left eye EL is <NUM> (= <NUM> × <NUM>). Further, the amount of the outside light PL211 that passes through the beam splitter <NUM> and reaches the left eye EL is <NUM> (= <NUM> × <NUM>).

The outside light PL212 to be diffusely reflected after entering the beam splitter <NUM> is described hereinafter. The outside light PL212 enters the beam splitter <NUM> after passing through the combiner <NUM>. Thus, half of the outside light PL212 that has passed through the combiner <NUM> passes through the beam splitter <NUM>, and the remaining half is reflected by the beam splitter <NUM>. Of the outside light PL212, light that has been reflected by the beam splitter <NUM> is referred to as outside light PL213. Of the outside light PL212, light that has passed through the beam splitter <NUM> is referred to as outside light PL214.

When it is assumed that the amount of the outside light PL212 before entering the combiner <NUM> is <NUM>, the amount of the outside light PL212 immediately after passing through the combiner <NUM> is <NUM> (= <NUM> × <NUM>). Further, the amount of the outside light PL213 immediately after being reflected by the beam splitter <NUM> is <NUM> (= <NUM> × <NUM>). The amount of the outside light PL214 immediately after passing through the beam splitter <NUM> is <NUM> (= <NUM> × <NUM>).

Then, the outside light PL213 is diffusely reflected by the divider plate <NUM> at the location C. Part of the outside light PL213 that has been diffusely reflected by the divider plate <NUM> travels toward the left eye EL. The amount of the outside light PL213 that has been diffusely reflected by the divider plate <NUM> and travels toward the left eye EL is <NUM> (= <NUM> × <NUM>). Further, the outside light PL213 enters the left eye EL after passing through the beam splitter <NUM>. Thus, the amount of the outside light PL213 that reaches the left eye EL is <NUM> (= <NUM> × <NUM>).

The outside light PL214 is diffusely reflected by the divider plate <NUM> at the location D. Part of the outside light PL214 that has been diffusely reflected by the divider plate <NUM> travels toward the left eye EL. The amount of the outside light PL214 that has been diffusely reflected by the divider plate <NUM> and travels toward the left eye EL is <NUM> (= <NUM> × <NUM>). Thus, the amount of the outside light PL214 that reaches the left eye EL is <NUM>.

Therefore, the total amount of the outside light PL211 and the outside light PL213 that have been diffusely reflected at the location C is <NUM> (= <NUM> + <NUM>). On the other hand, the amount of the outside light PL214 that has been diffusely reflected at the location D is <NUM>. A difference arises in brightness seen by the user between the location C and the location D. The location C is seen brighter than the location D by the user. In other words, the divider plate <NUM> is seen brighter than the divider plate <NUM> by the user.

According to the invention, the divider plate <NUM> and the divider plate <NUM> have different values of diffuse reflectance. To be specific, the diffuse reflectance of the divider plate <NUM> is made higher than the diffuse reflectance of the divider plate <NUM>. This reduces the difference in brightness between the divider plate <NUM> and the divider plate <NUM>, which allows higher display quality to be obtained. In other words, by adjusting the divider plate <NUM> and the divider plate <NUM> in diffuse reflectance, non-uniformity of brightness of the divider part <NUM> is corrected. This allows higher display quality to be obtained.

Note that the divider plate <NUM> is colored by a color darker than that of the divider plate <NUM>. This allows the light diffuse reflectance of the divider plate <NUM> to be higher than the light diffuse reflectance of the divider plate <NUM>. By setting the diffuse reflectance of the divider plate <NUM> at approximately <NUM> times the diffuse reflectance of the divider plate <NUM>, the user is able to see the divider plate <NUM> at a brightness of the same degree as the divider plate <NUM>. Obviously, the diffuse reflectance of the divider plate <NUM> may be more than or equal to, or less than or equal to <NUM> times the diffuse reflectance of the divider plate <NUM>.

The diffuse reflectance is made different by coloring the divider plate <NUM> and the divider plate <NUM> by colors of the same type that are different only in grayscale. In a case where the divider plate <NUM> and the divider plate <NUM> are gray, the mixing ratio of white and black is changed to change the grayscale, thereby making the diffuse reflectance different. In a case of obtaining dark gray having low diffuse reflectance, a color having an increased ratio of black is used, and in a case of obtaining light gray having high diffuse reflectance, a color having an increased ratio of white is used.

The diffuse reflectance may be made different by subjecting the surfaces of the divider plate <NUM> and the divider plate <NUM> to different diffuse reflection treatments between the front side (in the +Z direction) and back side (in the -Z direction) of the beam splitter <NUM>. One of the divider plate <NUM> and the divider plate <NUM> is subjected to diffuse reflection treatment for obtaining high diffuse reflectance, and the other is subjected to diffuse reflection treatment for obtaining low diffuse reflectance. In a case of increasing the diffuse reflectance, the pitch of irregularities is narrowed, and in a case of decreasing the diffuse reflectance, the pitch of irregularities is widened.

In a case where the divider plate <NUM> and the divider plate <NUM> have skin tones, the diffuse reflectance is made different by changing visual reflectance obtained by quantifying reflectance that a human being senses visually, thereby to change the grayscale of skin tones. Since the visual reflectance expresses brightness (luminance) that is not expressed by the CIE chromaticity diagram, only the visual reflectance is changed without changing the CIE chromaticity coordinates of the colors of the divider plate <NUM> and the divider plate <NUM>. In a case of obtaining a dark skin tone having low diffuse reflectance, a skin tone having low visual reflectance is used, and in a case of obtaining a light skin tone having high diffuse reflectance, a skin tone having high visual reflectance is used.

By changing the grayscale of colors of the divider plates <NUM> and <NUM> or visual reflectance, and changing the pitch of irregularities of the surfaces of the divider plates <NUM> and <NUM>, the diffuse reflectance of the divider part <NUM> is made different between the front side (in the +Z direction) and the back side (in the -Z direction) of the beam splitter <NUM>. This allows the user to naturally see the divider plate <NUM> and the divider plate <NUM>, which improves display quality.

Further, a spatial distribution of diffuse reflectance may be provided in the divider plate <NUM>. As shown in <FIG>, for example, the diffuse reflectance of the divider plate <NUM> may be decreased forward (in the +Z direction). <FIG> shows that a portion of a darker color has lower diffuse reflectance and a portion of a lighter color has higher diffuse reflectance. Alternatively, the diffuse reflectance of the divider plate <NUM> may be increased forward (in the +Z direction). Further, a spatial distribution of diffuse reflectance may be provided in the divider plate <NUM> in the up-down direction (the Y direction). Likewise, a spatial distribution of diffuse reflectance may be provided in the divider plate <NUM>. In other words, spatial distributions are provided for the diffuse reflectances of the divider plates <NUM> and <NUM> in such a way that the divider part <NUM> is not displayed with emphasis.

Note that also in the structure of the first embodiment, the divider part <NUM> may be separated into a plurality of regions, and the respective regions may be different in diffuse reflectance. For example, the diffuse reflectance of the diffuse reflection plate to be the divider part <NUM> may be changed between a region in front (in +Z direction) of the beam splitters <NUM> and 122R and a region behind (in the -Z direction) the beam splitters <NUM> and 122R. The region behind (in the -Z direction) the beam splitters <NUM> and 122R of the divider part <NUM> may have diffuse reflectance lower than the diffuse reflectance of the region in front (in +Z direction) of the beam splitters <NUM> and 122R of the divider part <NUM>. For example, by changing the grayscale of the divider part <NUM> per region, diffuse reflectance has a desired distribution.

The head-mounted display <NUM> according to a third example is described with reference to <FIG> is a side view schematically showing the structure of the head-mounted display <NUM>. In this example, the head-mounted display <NUM> is of the single mirror type unlike the first and second embodiments. In other words, neither the beam splitter <NUM> nor the beam splitter <NUM> is provided between the left eye EL and the combiner <NUM>.

The angle at which the left-eye display element <NUM> is located is different from that in the first and second embodiments. The left-eye display element <NUM> is arranged diagonally. In other words, the display surface of the left-eye display element <NUM> faces downward (in the -Y direction) and forward (in the +Z direction). The display light PL11 from the left-eye display element <NUM> is output in the -Y direction and the +Z direction. The combiner <NUM> is arranged below (in the -Y direction) the left-eye display element <NUM>. The combiner <NUM> transmits half of light, and reflects the remaining half.

The combiner <NUM> reflects the display light PL11 from the left-eye display element <NUM> toward the left eye EL. The combiner <NUM> is a concave half mirror, and reflects the display light PL11 so as to focus the display light PL11 toward the left eye EL. The left-eye optical system <NUM> guides the display light from the left-eye display element <NUM> to the left eye EL. The optical system allows a virtual image to be displayed in front (in the +Z direction) of the user.

Further, the outside light PL21 passes through the combiner <NUM> and enters the left eye EL. The transmittance of the combiner <NUM> is <NUM>%. Thus, the outside light PL21 is attenuated to <NUM>% by passing through the combiner <NUM>. Then, the outside light PL21 that has been attenuated to <NUM>% enters the left eye EL. This allows a display image to be superimposed on a view in the front (in the +Z direction). Further, since the combiner <NUM> extends to a place immediately below the left-eye display element <NUM> in this example, the light shielding part <NUM> is not provided.

The divider part <NUM> is arranged between the left front space <NUM> and the right front space 160R. This improves display quality similarly to the first and second embodiments. Further, since the beam splitter <NUM> is not provided in <FIG>, a single diffuse reflection plate can be used as the divider part <NUM> similarly to the first embodiment.

Note that although the head-mounted display <NUM> is described as an optical see-through head-mounted display, the head-mounted display <NUM> may be a non-transmissive head-mounted display. In the case of a non-transmissive head-mounted display, reflective mirrors are provided instead of the combiners <NUM> and 121R. In other words, a reflective member arranged in front of the beam splitter <NUM> may be a beam splitter such as a half mirror, or may be a reflective mirror. The reflective member reflects display light toward the user.

This application is based upon and claims the benefit of priority from <CIT>.

Claim 1:
A head-mounted display (<NUM>) comprising:
a reflective member (<NUM>, 121R) arranged in front of a user, and configured to reflect display light (PL11, PR11) for forming a display image toward the user;
a beam splitter (<NUM>, 122R, <NUM>) arranged between the reflective member and the eyes of the user, and configured to reflect the display light toward the reflective member and transmit the display light that has been reflected by the reflective member, and
a divider part (<NUM>) arranged between a space (<NUM>) in front of a left eye (EL) of the user and a space (160R) in front of a right eye (ER), and configured to diffusely reflect the display light,
wherein the divider part (<NUM>) is different in diffuse reflectance in front of and behind the beam splitter.