Sony Patent | Image Display Apparatus

Patent: Image Display Apparatus

Publication Number: 20200183183

Publication Date: 20200611

Applicants: Sony

Abstract

An image display apparatus according to an embodiment of the present technology includes an emitter, an image-forming element, a first reflector element, and a second image-forming element. The emitter emits an image light beam. The image-forming element forms an image of the entering image light beam as a mid-air image. The first reflector element includes a first surface and a second surface and that causes at least part of the image light beam, which is emitted from the emitter and enters the first surface, to pass therethrough and reflects at least part of the image light beam, which enters the second surface, to the image-forming element. The second reflector element reflects at least part of the image light beam, which enters the first surface and passes through the first reflector element, to the second surface of the first reflector element.

TECHNICAL FIELD

[0001] The present technology relates to an image display apparatus that displays a mid-air image.

BACKGROUND ART

[0002] In recent years, a technology of displaying an image floating in the air has been developed. For example, an image of an operation screen, video content, or the like is formed and displayed as a mid-air image in a space viewed by a user. With this configuration, a mid-air display in which a display is floating in a space where nothing exists and the like can be realized.

[0003] Patent Literature 1 has described an image-forming element that displays an image of an object in a space. Inside this image-forming element, a large number of flat light reflectors orthogonal to one another are arranged at constant pitches. Part of light entering the image-forming element is reflected by the flat light reflectors orthogonal to one another twice. Then, the reflected light is emitted from a surface opposite to an incident surface plane-symmetrically with respect to the image-forming element. With this configuration, a real image of the object is formed at a position plane-symmetric to the object across the image-forming element. As a result, the user can view a mid-air image of the object (e.g., paragraphs [0034] to [0038] of specification and FIG. 5 of Patent Literature 1).

CITATION LIST

Patent Literature

[0004] Patent Literature 1: Japanese Patent Application Laid-open No. 2011-175297

DISCLOSURE OF INVENTION

Technical Problem

[0005] The display technology using the mid-air image is expected to be applied in various fields such as amusement, advertisement, and medical fields. It is desirable to provide a technology capable of downsizing the apparatus.

[0006] In view of the above-mentioned circumstances, it is an object of the present technology to provide a compact image display apparatus capable of displaying a mid-air image.

Solution to Problem

[0007] In order to accomplish the above-mentioned object, an image display apparatus according to an embodiment of the present technology includes an emitter, an image-forming element, a first reflector element, and a second image-forming element.

[0008] The emitter emits an image light beam.

[0009] The image-forming element forms an image of the entering image light beam as a mid-air image.

[0010] The first reflector element includes a first surface and a second surface and that causes at least part of the image light beam, which is emitted from the emitter and enters the first surface, to pass therethrough and reflects at least part of the image light beam, which enters the second surface, to the image-forming element.

[0011] The second reflector element reflects at least part of the image light beam, which enters the first surface and passes through the first reflector element, to the second surface of the first reflector element.

[0012] In this image display apparatus, the image light beam entering the first surface of the first reflector element and passing through the first reflector element are reflected by the second reflector element to the second surface of the first reflector element. The image light beam reflected to the second surface of the first reflector element is reflected by the second surface to the image-forming element. By configuring the optical path of the image light beam in this manner, downsizing of the apparatus can be achieved. As a result, a compact image display apparatus capable of displaying a mid-air image can be realized.

[0013] The second reflector element may reflect at least part of the image light beam, which enters the first surface of the first reflector element, passes through the first reflector element, and is emitted in a predetermined direction, in the predetermined direction.

[0014] In this image display apparatus, the image light beam emitted from the first reflector element is turned back and reflected by the second reflector element in the same direction. With this configuration, downsizing of the apparatus can be achieved.

[0015] The emitter may emit the image light beam to the first surface of the first reflector element in the predetermined direction.

[0016] With this configuration, the optical path of the image light beam from the emitter to the second surface of the first reflector element, which it enters, can be configured in a substantially straight line. As a result, downsizing of the apparatus can be achieved.

[0017] The emitter, the first reflector element, and the second reflector element may be arranged in the stated order in the predetermined direction.

[0018] The emitter, the first reflector element, and the second reflector element are arranged in line along the predetermined direction. Therefore, simplification of the apparatus configuration and downsizing of the apparatus can be sufficiently achieved.

[0019] The image-forming element may include an incident surface, which the image light beam enters. In this case, the predetermined direction may be a direction parallel to the incident surface.

[0020] With this configuration, the emitter, the first reflector element, and the second reflector element are arranged in line along the incident surface. Therefore, the thickness and the like of the apparatus can be sufficiently reduced.

[0021] The image display apparatus may further include one or more other emitters that each emit another image light beam.

[0022] With this configuration, images of a plurality of image light beams can be formed, and superimposition of the mid-air images and the like can be performed.

[0023] The one or more other emitters may include the other emitter that is arranged on a side opposite to the first reflector element of the second reflector element and emits the other image light beam to the second reflector element in the predetermined direction. In this case, the second reflector element may cause at least part of the other image light beam emitted by the other emitter to pass therethrough and emit the at least part of the other image light beam to the second surface of the first reflector element.

[0024] With this configuration, the mid-air image of the other image light beam can be displayed by using a part of the optical path of the image light beam. As a result, the mid-air images can be displayed to be superimposed on each other while the apparatus size is reduced.

[0025] The one or more other emitters may include the other emitter that is arranged between the first reflector element and the second reflector element, emits the other image light beam to the second reflector element in the predetermined direction, and causes the image light beam passing through the first reflector element and the other image light beam reflected by the second reflector element to pass therethrough.

[0026] With this configuration, the other emitter that emits the other image light beam on the optical path of the image light beam can arranged. As a result, the mid-air images can be displayed to be superimposed on each other while the apparatus size is reduced.

[0027] The one or more other emitters may include the other emitter that is arranged on a side opposite to the image-forming element with respect to the first reflector element and emits the other image light beam to the first surface of the first reflector element in an emission direction of the image light beam reflected by the second surface of the first reflector element.

[0028] With this configuration, the mid-air image of the other image light beam can be displayed by using a part of the optical path of the image light beam. As a result, the mid-air images can be displayed to be superimposed on each other while the apparatus size is reduced.

[0029] The image display apparatus may further include a changer that changes an image-forming position of the mid-air image which is formed by the image-forming element.

[0030] With this configuration, the image-forming position of the mid-air image can be changed, and the position of the mid-air image and the like can be controlled with high precision.

[0031] The image-forming element may form the mid-air image at a position depending on an incident position of the image light beam which enters the image-forming element and an optical path length of the image light beam from the emitter to the image-forming element. In this case, the changer may be capable of changing at least one of the incident position of the image light beam or the optical path length of the image light beam.

[0032] By changing the incident position of the image light beam and the optical path length of the image light beam, the position, the protruding distance, and the like of the mid-air image can be controlled with high precision.

[0033] The changer may be capable of changing a position of at least one of the emitter, the first reflector element, or the second reflector element.

[0034] With this configuration, the incident position and the optical path length of the image light beam can be easily changed, and the position, the protruding distance, and the like of the mid-air image can be controlled with high precision.

[0035] The changer may move at least one of the emitter, the first reflector element, or the second reflector element in the predetermined direction.

[0036] With this configuration, the protruding distance of the mid-air image and the like can be easily controlled by changing the distance and the like of the emitter, the first reflector element, and the second reflector element which are arranged in line, for example.

[0037] The changer may be capable of changing at least one of an emission direction of the image light beam of the emitter, an angle of reflection of the image light beam of the first reflector element, or an angle of reflection of the image light beam of the second reflector element.

[0038] With this configuration, the incident position and the like of the image light beam can be easily changed, and the image-forming position of the mid-air image can be controlled with high precision.

[0039] The image display apparatus may further include another reflector element that is arranged between the first reflector element and the second reflector element, reflect part of the image light beam, which passes through the first reflector element, to the image-forming element, and cause other part of light the image light beam, which passes through the first reflector element, to pass therethrough.

[0040] With this configuration, it is possible to cause a plurality of mid-air images to be formed from a single image light beam.

[0041] The image display apparatus may further include a plurality of image display units, each of which is a unit including the emitter and the first reflector element and the second reflector element for guiding the image light beam emitted by the emitter to the image-forming element, the plurality of image display units being arranged using a position of the image-forming element as a reference.

[0042] With this configuration, downsizing of the apparatus can be achieved in such a manner that the plurality of image display units are arranged using the position of the image-forming element as a reference. As a result, a compact apparatus capable of displaying a plurality of mid-air images can be realized.

[0043] The plurality of image display units may each include the image-forming element for forming an image of the image light beam emitted by the emitter as the mid-air image. In this case, the plurality of image display units may be arranged in such a manner that the mid-air images respectively formed by the plurality of image display units are superimposed on each other at a predetermined angle, using a predetermined reference point as a center.

[0044] With this configuration, the range of angle in which the mid-air image can be visually recognized can be extended by superimposing the plurality of mid-air images on each other at the predetermined angle, for example.

[0045] The image display apparatus may further include a sensor unit that detects a touch operation on the mid-air image.

[0046] With this configuration, a touch operation on the mid-air image can be performed, and an operation screen to be displayed in the air and the like can be realized.

[0047] The changer may include an external optical unit which is arranged on an optical path of the image light beam which is emitted from the image-forming element.

[0048] With this configuration, the image-forming position, the size, and the like of the mid-air image can be controlled with high precision.

[0049] The changer may include an internal optical unit which is arranged on an optical path of the image light beam from the emitter to the image-forming element.

[0050] With this configuration, the image-forming position, the size, and the like of the mid-air image can be controlled with high precision.

Advantageous Effects of Invention

[0051] As described above, in accordance with the present technology, a compact image display apparatus capable of displaying a mid-air image can be provided. It should be noted that the effects described here are not necessarily limitative and any effect described in the present disclosure may be provided.

BRIEF DESCRIPTION OF DRAWINGS

[0052] FIG. 1 A schematic diagram showing a configuration example of a mid-air image display apparatus according to a first embodiment.

[0053] FIG. 2 A schematic diagram showing arrangement of a first display and first and second transmissive mirrors.

[0054] FIG. 3 A schematic diagram showing a configuration inside an apparatus which is shown as a comparative example.

[0055] FIG. 4 A schematic diagram for describing arrangement of a plurality of displays.

[0056] FIG. 5 A schematic diagram showing an example of an operation of an actuator.

[0057] FIG. 6 A schematic diagram showing an example of the operation of the actuator.

[0058] FIG. 7 A schematic diagram showing an example of the operation of the actuator.

[0059] FIG. 8 A schematic diagram showing an example of the operation of the actuator.

[0060] FIG. 9 A schematic diagram showing an example of a mid-air image displayed in accordance with the operation of the actuator.

[0061] FIG. 10 A schematic diagram for describing an optical path in an image-forming optical system.

[0062] FIG. 11 A diagram for describing a lens unit arranged on an optical path of a first image light beam emitted from an optical image-forming element.

[0063] FIG. 12 A schematic diagram for describing a configuration in which the image-forming optical system is movable.

[0064] FIG. 13 A schematic diagram showing another configuration example of the image-forming optical system.

[0065] FIG. 14 A schematic diagram showing another configuration example of the image-forming optical system.

[0066] FIG. 15 A schematic diagram showing a configuration example in a case where lenses are arranged inside the apparatus.

[0067] FIG. 16 A schematic diagram for describing a lens unit arranged inside the apparatus.

[0068] FIG. 17 A schematic diagram showing another configuration example of an emission optical system.

[0069] FIG. 18 A schematic diagram showing a configuration example of a mid-air image display apparatus according to a second embodiment.

[0070] FIG. 19 A schematic diagram showing a configuration example of the mid-air image display apparatus according to the second embodiment.

[0071] FIG. 20 A schematic diagram showing a configuration example of a mid-air image display apparatus according to a third embodiment.

[0072] FIG. 21 A schematic diagram for describing how the mid-air image displayed at a reference point is seen.

[0073] FIG. 22 A schematic diagram showing another configuration example of a mid-air image display unit.

[0074] FIG. 23 A schematic diagram showing another configuration example of the mid-air image display unit.

[0075] FIG. 24 A schematic diagram showing a configuration example of a mid-air image display apparatus according to another embodiment.

MODE(S)* FOR CARRYING OUT THE INVENTION*

[0076] Hereinafter, embodiments according to the present technology will be described with reference to the drawings.

First Embodiment

[0077] [Configuration of Mid-Air Image Display Apparatus] FIG. 1 is a schematic diagram showing a configuration example of a mid-air image display apparatus according to a first embodiment of the present technology. A mid-air image display apparatus 100 includes a plurality of displays 10, an emission optical system 20, an optical image-forming element 30, and an image-forming optical system 40. In this embodiment, the mid-air image display apparatus 100 corresponds to a mid-air image display apparatus.

[0078] The plurality of displays 10 each generate and display an original image on which an image to be displayed in the air is based. Light of respective pixels of the original image to be displayed on each of the displays 10 is emitted to a front side (display direction side) as an image light beam 50 that constitutes the image. It should be noted that in FIG. 1, the display 10 and the image light beam 50 are schematically expressed as the same icon and the arrow shape of the display 10 (image light beam 50) represents an image size and upper and lower directions. The way of illustrating the display 10 is applied also in other figures.

[0079] A specific configuration of the display 10 is not limited. For example, any display apparatus using liquid-crystal, electro-luminescence (EL), or the like may be used. It should be noted that any device or mechanism capable of emitting the image light beam 50 may be used instead of the display 10. For example, a projector or the like including a liquid-crystal panel, a digital micromirror device (DMD), or the like may be used. Otherwise, any image display apparatus (image projection apparatus) may be used.

[0080] As shown in FIG. 1, in this embodiment, first and second displays 11 and 12 are provided as the plurality of displays 10. The first display 11 emits the image light beam 50 (hereinafter, referred to as first image light beam 51) in a predetermined direction which is substantially parallel to an incident surface 31 of the optical image-forming element 30. In the example shown in FIG. 1, XYZ-coordinates are set such that a plane direction of the incident surface 31 of the optical image-forming element 30 is an XY-plane direction. Then, the first image light beam 51 is emitted along an optical axis 60 extending in the X direction.

[0081] The second display 12 is arranged facing the first display 11 across the emission optical system 20 in the X direction. The second display 12 emits a second image light beam 52 toward the first display 11 in the X direction. The second image light beam 52 is emitted in a direction opposite to that of the first image light beam 51 along the optical axis 60 of the first image light beam 51.

[0082] In this embodiment, the first display 11 and the first image light beam 51 correspond to an emitter and an image light beam. The second display 12 and the second image light beam 52 correspond to another emitter and another image light beam.

[0083] The emission optical system 20 is an optical system that guides each image light beam 50 emitted by each display 10 to the optical image-forming element 30. As shown in FIG. 1, the emission optical system 20 is arranged between the first and second displays 11 and 12. The emission optical system 20 includes a first transmissive mirror 21, a second transmissive mirror 22, and an actuator 23.

[0084] The first transmissive mirror 21 has a plate shape and is arranged on the optical axis 60 on a front side of the first display 11. The first transmissive mirror 21 includes a first surface 211 and a second surface 212 opposite thereto. The first transmissive mirror 21 causes part of light entering each surface to pass therethrough and reflects other part of light. Light transmittance (reflectance) in the first and second surfaces 211 and 212 is not limited. For example, a half mirror or the like having a transmittance (reflectance) of about 50% may be used.

[0085] As shown in FIG. 1, the first transmissive mirror 21 is arranged tilted at a predetermined angle using the Y direction as an axis from a state in which the first and second surfaces 211 and 212 are arranged to be orthogonal to the optical axis 60. That is, assuming that the Z direction corresponds to the upper and lower directions, the first surface 211 facing the first display 11 is tilted to be directed downward. The second surface 212 is tilted to be directed to the optical image-forming element 30 arranged above.

[0086] Assuming that an angle formed by the first transmissive mirror 21 and the X direction as viewed in the Y direction is an angle of inclination .theta., that angle of inclination .theta. is typically defined on the basis of mid-air image-forming efficiency of the optical image-forming element 30. The optical image-forming element 30 of this embodiment most efficiently forms an image of the image light beam 50 entering at an angle of about 45 degrees with respect to the incident surface 31 as a mid-air image 70. Therefore, the angle of inclination .theta. of the first transmissive mirror 21 is set to about 67.5 degrees such that the image light beam 50 enters the optical image-forming element 30 at the angle of about 45 degrees. As a matter of course, the present technology is not limited thereto.

[0087] The second transmissive mirror 22 has a plate shape and is arranged on the optical axis 60 of the first image light beam 51 passing through the first transmissive mirror 21. Therefore, in this embodiment, the display 10 (first display 11), the first transmissive mirror 21, and the second transmissive mirror 22 are arranged in the stated order in the X direction which is a direction of the optical axis 60. It should be noted that the second display 12 is also arranged on a rear side of the second transmissive mirror 22 (on a side opposite to the first display 11) in the X direction.

[0088] The second transmissive mirror 22 includes a first surface 221 directed to the first transmissive mirror 21 and a second surface 222 opposite thereto. The second transmissive mirror 22 causes part of light entering each surface to pass therethrough and reflects other part of light. Transmittance (reflectance) of the second transmissive mirror 22 is not limited. For example, a half mirror or the like may be used. As shown in FIG. 1, the second transmissive mirror 22 is arranged such that the first and second surfaces 221 and 222 are orthogonal to the optical axis 60.

[0089] In this embodiment, the first transmissive mirror 21 and the second transmissive mirror 22 respectively correspond to a first reflector element and a second reflector element. Specific material and the like of the first and second transmissive mirrors 21 and 22 are not limited. For example, a transparent member including plastic, glass, and the like on which a thin film including aluminum, silver, chromium, and the like is formed is used.

[0090] The actuator 23 is capable of changing respective positions of the display 10, the first transmissive mirror 21, and the second transmissive mirror 22. In this embodiment, the actuator 23 independently moves the display 10, the first transmissive mirror 21, and the second transmissive mirror 22 relative to one another in the direction (X direction) of the optical axis 60 of the first image light beam 51. Moreover, the actuator 23 is capable of changing the angle of inclination .theta. of the first transmissive mirror 21.

[0091] A specific configuration of the actuator 23 is not limited. For example, any moving mechanism such as a linear stage using a stepping motor or the like, any rotating mechanism using a gear mechanism or the like, or the like may be used. In this embodiment, the actuator 23 functions as an adjustment mechanism (changer) that changes an image-forming position of the mid-air image formed by the optical image-forming element 30.

[0092] The optical image-forming element 30 has a plate shape and is arranged such that the incident surface 31 and an emission surface 32 are substantially parallel to the direction (X direction) of the optical axis 60. The incident surface 31 of the optical image-forming element 30 is provided inside the apparatus in which the first and second displays 11 and 12 and the emission optical system 20 are housed. Then, the emission surface 32 is provided on a mid-air side to which a user’s viewpoint 1 (line of sight) is directed. The optical image-forming element 30 forms an image of the image light beam entering the incident surface 31 from the inside of the apparatus, as the mid-air image 70 in the air.

[0093] In this embodiment, the optical image-forming element 30 having a structure in which pairs of minute reflection surfaces perpendicular to the incident surface 31 (emission surface 32) and orthogonal to one another are arranged in a matrix form at predetermined intervals in an in-plane direction of the incident surface 31 is used. Such a structure is realized by arranging a large number of flat light reflectors orthogonal to one another at constant pitches as described in Patent Literature 1, for example. Alternatively, a structure of a dihedral corner reflector in which reflection surfaces are formed at side surfaces of rectangular holes or the like may be used.

[0094] Part of the image light beam 50 entering from the incident surface 31 is reflected by the pair of minute reflection surfaces orthogonal to one another twice. Then, the reflected image light beam 50 is emitted from the emission surface 32. In this case, an incident direction and an emission direction of the image light beam 50 are plane-symmetric with respect to the optical image-forming element 30. Moreover, a distance by which the mid-air image 70 protrudes from the optical image-forming element 30 is substantially equal to an optical path length of the image light beam 50 from the display 10 to the optical image-forming element 30. For example, if the image light beam 50 emitted from the display 10 directly enters the optical image-forming element 30, an inverted real image (mid-air image 70) of the image light beam 50 is formed at a position plane-symmetric to the position of the display 10 across the optical image-forming element 30 (see FIG. 3).

[0095] The image-forming optical system 40 is arranged on an optical path of the image light beam 50 emitted from the optical image-forming element 30, which is on the mid-air side. In this embodiment, the image-forming optical system 40 includes a prism 41 and a lens unit 42. The prism 41 has a triangular prism shape. Three surfaces of prism 41, which are side surfaces of the triangular prism, are used as an incident surface 43, a reflection surface 44, and an emission surface 45. As shown in FIG. 1, the prism 41 is arranged such that the incident surface 43 is proximate to the emission surface 32 of the optical image-forming element 30.

[0096] The lens unit 42 is provided on the emission surface 45 of the prism 41. The lens unit 42 may be formed integrally with the prism 41 or may be connected to the emission surface 45 after those are separately provided. Material and the like of the prism 41 and the lens unit 42 are not limited. For example, glass, crystal, and the like may be used as appropriate. The image-forming optical system 40 functions as an external optical unit included in an adjustment function (changer).

[0097] The outline of display operations of a first mid-air image 71 and a second mid-air image 72 shown in FIG. 1 will be briefly described. The first image light beam 51 emitted from the first display 11 passes through the first transmissive mirror 21 and enters the second transmissive mirror 22 in the X direction. The first image light beam 51 turned back and reflected by the second transmissive mirror 22 is reflected by the first transmissive mirror 21 and enters the optical image-forming element 30. The first image light beam 51 emitted by the optical image-forming element 30 to the mid-air side travels through the prism 41 and is emitted via the lens unit 42 on the emission surface 45. With this configuration, the first mid-air image 71 is displayed.

[0098] The second image light beam 52 emitted from the second display 12 passes through the second transmissive mirror 22 and enters the first transmissive mirror 21 in the X direction. The second image light beam 52 is reflected by the first transmissive mirror 21 and enters the optical image-forming element 30. The second image light beam 52 emitted by the optical image-forming element 30 to the mid-air side travels through the prism 41 and is emitted via the lens unit 42 on the emission surface 45. With this configuration, the second mid-air image 72 is displayed.

[0099] Hereinafter, features of the respective sections of the mid-air image display apparatus 100 shown in FIG. 1 will be described in detail.

[0100] FIG. 2 is a schematic diagram showing arrangement of the first display 11 and the first and second transmissive mirrors 21 and 22. FIG. 3 is a schematic diagram showing a configuration inside an apparatus shown as a comparative example. It should be noted that in the configurations shown in FIGS. 2 and 3, the image-forming optical system 40 shown in FIG. 1 is omitted for easy understanding of the image-forming position of the first mid-air image 71 according to the arrangement of the first display 11 and the first and second transmissive mirrors 21 and 22.

[0101] As described above, in this embodiment, the first display 11, the first transmissive mirror 21, and the second transmissive mirror 22 are arranged in the stated order in the X direction which is the direction of the optical axis 60. The first image light beam 51 emitted from the first display 11 along the optical axis 60 enters the first surface 211 of the first transmissive mirror 21. Part of the first image light beam 51 entering the first surface 211 passes through the first transmissive mirror 21 and is emitted in the X direction as it is (optical path 81).

[0102] The first image light beam 51 passing through the first transmissive mirror 21 and emitted in the X direction enters the first surface 221 of the second transmissive mirror 22. Part of the first image light beam 51 entering the first surface 221 of the second transmissive mirror 22 is reflected in the X direction. That is, the first image light beam 51 is turned back and emitted by the second transmissive mirror 22 in the same direction as the incident direction (optical path 82).

[0103] The first image light beam 51 reflected by the second transmissive mirror 22 enters the second surface 212 of the first transmissive mirror 21. Part of the first image light beam 51 entering the second surface 212 of the first transmissive mirror 21 is reflected toward the incident surface 31 of the optical image-forming element 30 (optical path 83).

[0104] Part of the first image light beam 51 emitted from the first display 11 in this manner is guided to the optical image-forming element 30 while passing through the optical paths 81 to 83. An optical path length of the optical paths 81 to 83 is a distance obtained by summing up a distance from the first display 11 to the second transmissive mirror 22 (optical path 81), a distance from the second transmissive mirror 22 to the first transmissive mirror 21 (optical path 82), and a distance between the first transmissive mirror 21 and the optical image-forming element 30 (optical path 83).

[0105] The first image light beam 51 entering the incident surface 31 of the optical image-forming element 30 is emitted in an emission direction which is plane-symmetric to an incident direction to the incident surface 31 across the optical image-forming element 30. In this embodiment, the first image light beam 51 enters at the angle of about 45 degrees with respect to the incident surface 31. Therefore, the first image light beam 51 is emitted toward the mid-air side also at the angle of about 45 degrees and an image of the first image light beam 51 is formed as the first mid-air image 71.

[0106] A position at which the first mid-air image 71 is formed is a position depending on an incident position P of the first image light beam 51 which enters the optical image-forming element 30 and on the optical path length (optical paths 81+82+83) of the first image light beam 51 from the first display 11 to the optical image-forming element 30. In the example shown in FIG. 2, the first mid-air image 71 is formed at a position spaced apart from the incident position P of the first image light beam 51 in a direction of the angle of about 45 degrees by a distance substantially equal to the optical path length of the first image light beam 51. Therefore, a protruding distance H from the optical image-forming element 30 to the first mid-air image 71 is substantially equal to the optical path length of the first image light beam 51.

[0107] The comparative example shown in FIG. 3 has a configuration in a case of displaying the first mid-air image 71 at the same position without the emission optical system 20. Without the emission optical system 20, it is necessary to arrange the first display 11 at a position spaced apart from the same incident position P by the same optical path length (=optical paths 81+82+83) at the angle of about 45 degrees. Therefore, for ensuring a space for forming the straight optical path inside the apparatus, the size of the mid-air image display apparatus 100 in a vertical direction (Z direction) and a horizontal direction (X direction) becomes very large.

[0108] In contrast, in the configuration according to this embodiment which is shown in FIG. 2, a turned-back optical path 90 on which the first image light beam 51 travels in a reciprocating manner is configured by the first display 11, the first transmissive mirror 21, and the second transmissive mirror 22 which are arranged in a straight line. Therefore, a distance twice as large as a distance by which the turned-back optical path 90 is configured (distance between the first and second transmissive mirrors 22 and 21) can be added as the optical path length. With this configuration, the space necessary for forming the optical path of the first image light beam 51 can be sufficiently reduced, and the size of the mid-air image display apparatus 100 can be sufficiently reduced. As a result, a compact mid-air image display apparatus 100 capable of displaying the mid-air image can be realized.

[0109] FIG. 4 is a schematic diagram for describing arrangement of the plurality of displays 10. In FIG. 4, the image-forming optical system 40 shown in FIG. 1 is omitted.

[0110] As shown in FIG. 1, in this embodiment, the first and second displays 11 and 12 are provided. The first and second displays 11 and 12 are arranged facing each other across the emission optical system 20 in the X direction.

[0111] The second display 12 is arranged on the rear side of the second transmissive mirror 22 (on a side opposite to the first transmissive mirror 21) such that the optical path of the second image light beam 52 is substantially equal to the optical path 82 of the first image light beam 51. The second image light beam 52 travelling on the optical path 82 is reflected by the first transmissive mirror 21 to the optical image-forming element 30. Then, the reflected second image light beam 52 enters the optical image-forming element 30 at substantially the same incident position P as the first image light beam 51. That is, the second image light beam 52 travels on the same optical paths (optical paths 82 and 83) as the first image light beam 51 and enters the optical image-forming element 30.

[0112] The second image light beam 52 entering the optical image-forming element 30 is emitted to the mid-air side in substantially the same emission direction as the first image light beam 51 and an image of second image light beam 52 is formed as the second mid-air image 72. A protruding distance of the second mid-air image 72 is substantially equal to an optical path length from the second display 12 to the optical image-forming element 30. Therefore, a distance obtained by summing up a distance (optical path 84) from the second display 12 to the second transmissive mirror 22, a distance (optical path 82) from the second transmissive mirror 22 to the first transmissive mirror 21, and a distance (optical path 83) from the first transmissive mirror 21 to the optical image-forming element 30 is the protruding distance of the second mid-air image 72.

[0113] In this embodiment, the optical path length of the second image light beam 52 is set to be shorter than the optical path length of the first image light beam 51. Therefore, as compared to the first mid-air image 71, the protruding distance of the second mid-air image 72 is shorter and the second mid-air image 72 is formed such that the second mid-air image 72 is closer to the optical image-forming element 30 than the first mid-air image 71 is. As viewed from the user, the second mid-air image 72 is displayed on the farther side (rear side) of the first mid-air image 71. With this configuration, it is possible to display an image in which the first mid-air image 71 and the second mid-air image 72 are superimposed on each other. For example, a high-level viewing experience can be provided.

[0114] By emitting another image light beam on the optical path, which has already been formed in the above-mentioned manner, it is possible to cause the other image light beam to enter the optical image-forming element 30 by using a part of that optical path. With this configuration, a member and the like for forming a new optical path become unnecessary, and other mid-air images can be easily displayed. Moreover, it is possible to easily cause an image in which a plurality of mid-air images are superimposed on one another to be displayed.

[0115] As shown in FIG. 4, it is also possible to arrange a third display 13 on a lower side of the first transmissive mirror 21 (on a side opposite to the optical image-forming element 30).

[0116] The third display 13 emits a third image light beam 53 to the first surface 211 of the first transmissive mirror 21 in an emission direction of the first image light beam 51 reflected by the second surface 212 of the first transmissive mirror 21 (incident direction to the optical image-forming element 30). That is, the third display 13 is arranged such that the third image light beam 53 passing through the first transmissive mirror 21 travels on the optical path 83 of the first image light beam 51.

[0117] With this configuration, the third image light beam 53 entering the optical image-forming element 30 is emitted to the mid-air side in an emission direction substantially similar to those of the first and second image light beams 51 and 52 and an image of the third image light beam 53 is formed as a third mid-air image 73. A protruding distance of the third mid-air image 73 is substantially equal to an optical path length from the third display 13 to the optical image-forming element 30. By adjusting a position of the third display 13 as appropriate, an image-forming position of the third mid-air image 73 can be adjusted and desired superimposed images can be displayed in the air. It should be noted that the third display 13 and the third image light beam 53 correspond to the other emitter and the other image light beam.

[0118] As shown in FIG. 4, it is also possible to arrange another display on the optical path of the image light beam 50, blocking the optical path.

[0119] For example, in the example shown in FIG. 4, a fourth display 14 is arranged on the optical paths 81 and 82 between the first and second transmissive mirrors 21 and 22. The fourth display 14 is a transmissive display and is capable of causing at least part of light entering it to pass therethrough.

[0120] The fourth display 14 emits a fourth image light beam 54 to the second transmissive mirror 22 in the X direction. The fourth image light beam 54 is emitted to travel on the optical path 81 of the first image light beam 51. Part of the fourth image light beam 54 is reflected by the second transmissive mirror 22 and passes through the fourth display 14. Then, it travels on the optical paths 82 and 83 and enters the optical image-forming element 30. The fourth image light beam 54 entering the optical image-forming element 30 is emitted to the mid-air side in an emission direction substantially similar to those of the first and second image light beams 51 and 52 and an image of the fourth image light beam 54 is formed as a fourth mid-air image 74.

[0121] By using the transmissive display, another display can be arranged on the optical path of the image light beam, which has already been formed. Then, using a part of that optical path, it is possible to cause the other image light beam to enter the optical image-forming element 30 at substantially the same incident position P. With this configuration, a member and the like for forming a new optical path become unnecessary, and other mid-air images can be easily displayed.

[0122] The fourth display 14 can be arranged not only at the position illustrated in FIG. 4, but also at a position between the optical image-forming element 30 and the first transmissive mirror 21 or any other position on the optical path. It should be noted that the fourth display 14 and the fourth image light beam 54 correspond to the other emitter and the other image light beam.

[0123] As described above, the plurality of mid-air images can be easily superimposed on one another by utilizing a part of the optical path of the first image light beam 51 from the first display 11 to the optical image-forming element 30. An apparatus configuration having a very high extensibility can be thus realized. For example, the image in which the four mid-air images are superimposed on one another can be displayed by arranging the first display 11 to the fourth display 14. With this configuration, for example, the user can view a stereoscopic mid-air video like a 3D-TV with naked eyes, and a high-level viewing experience can be provided.

[0124] Moreover, an optical system and the like for guiding the other image light beam to the optical image-forming element 30 do not need to be newly added. Therefore, the apparatus size can be sufficiently reduced. As a result, a compact mid-air image display apparatus 100 capable of displaying the mid-air image can be realized.

[0125] In this embodiment, the turned-back optical path 90 includes the first display 11, the first transmissive mirror 21, and the second transmissive mirror 22 which are arranged in the straight line. Therefore, the plurality of displays 10 can be easily arranged in accordance with various arrangement manners while the apparatus size is reduced.

[0126] It should be noted that the present technology is not limited to the case where the other image light beam is guided to the same incident position on the optical image-forming element 30 by utilizing a part of the optical path, which has already been formed. For example, it is also possible to cause the other image light beam to enter the optical image-forming element 30 at a position slightly deviated from the incident position. With this configuration, the plurality of mid-air images whose image-forming positions are slightly deviated can be displayed, and various viewing effects can be provided. As a matter of course, a case where a new optical path is formed and the other image light beam is guided to a totally different incident position is also conceivable.

[0127] It should be noted that in a case where the second display 12 is not arranged on the rear side of the second transmissive mirror 22, a total reflection mirror or the like having a transmittance of about 0% may be used as the second transmissive mirror 22. With this configuration, an amount of light of the image light beam reflected on the second transmissive mirror 22 can be increased, and a brighter mid-air image (having a higher luminance) can be displayed.

[0128] FIGS. 5 to 8 are schematic diagrams showing an example of an operation of the actuator 23. FIG. 9 is a schematic diagram showing an example of the mid-air image 70 displayed in accordance with the operation of the actuator 23.

[0129] As described above, the actuator 23 is capable of individually moving the display 10 and the first and second transmissive mirrors 21 and 22 in the direction (X direction) of the optical axis 60 (FIGS. 5 to 7). Moreover, the actuator 23 is capable of changing the angle of inclination .theta. of the first transmissive mirror 21 (FIG. 8). The incident position P of the image light beam 50, which enters the optical image-forming element 30, and the optical path length of the image light beam 50 from the display 10 to the optical image-forming element 30 are changed by operation of the actuator 23.

[0130] In FIG. 5, the second transmissive mirror 22 is moved by the actuator 23 in the direction (X direction) of the optical axis 60. For example, using a reference position as a reference, the second transmissive mirror 22 is moved in each of a direction (left-hand direction) away from the first display 11 and a direction (right-hand direction) to the first display 11. It is assumed that a distance by which it is movable to the left or right is d/2 and an entire distance by which it is movable is d.

[0131] When the second transmissive mirror 22 moves in the direction (left-hand direction) away from the first display 11, each of a forward path of the turned-back optical path 90 (part of the optical path 81) and a backward path (optical path 82) is extended. Therefore, the optical path length of the turned-back optical path 90 is extended by a distance twice as long as the movement distance of the second transmissive mirror 22. When the second transmissive mirror 22 moves in the direction (right-hand direction) to the first display 11, each of the forward path and the backward path of the turned-back optical path 90 is shortened. Therefore, the optical path length of the turned-back optical path 90 is shortened by a distance twice as long as the movement distance of the second transmissive mirror 22.

[0132] Therefore, as shown in FIG. 5, when the second transmissive mirror 22 moves in the left-hand direction by the distance d/2, a protruding distance of the first mid-air image 71 is extended by the double distance d (first mid-air image 71a). When the second transmissive mirror 22 moves in the right-hand direction by the distance d/2, the protruding distance of the first mid-air image 71 is shorter by the double distance d (first mid-air image 71b).

[0133] In the example shown in FIG. 5, an alphabet character E is displayed as the first mid-air image 71. Moreover, a square including two large and small circles therein is displayed as the second mid-air image 72. It is assumed that outer frames of the first and second mid-air images 71 and 72, which are shown as the broken lines, correspond to pixels at outer edges of the first and second displays 11 and 12 and the image light beam 50 is not emitted from those pixels.

[0134] In FIG. 9, a change of superimposed images when the second transmissive mirror 22 is moved in the left-hand direction is shown. When the second transmissive mirror 22 is moved in the left-hand direction, the protruding distance of the first mid-air image 71 is extended, and thus the first mid-air image 71 is displayed closer to the user. Although the size of the first mid-air image 71 itself is not changed, the first mid-air image 71 is displayed at a closer position, and thus the alphabet character E appears to be enlarged.

[0135] Regarding the second mid-air image 72, the optical path length of the second image light beam 52 does not change even when the second transmissive mirror 22 is moved. Thus, its image-forming position does not change. Therefore, the size of the second mid-air image 72 is maintained and only the character E is enlarged. The display of the superimposed images can be easily controlled in this manner.

[0136] In this embodiment, due to the configuration of the turned-back optical path 90, the protruding distance of the first mid-air image 71 becomes twice as long as the movement distance of the second transmissive mirror 22. Therefore, the protruding distance can be greatly changed by using a small amount of movement, and the size of the actuator 23 can be reduced. As a result, downsizing of the mid-air image display apparatus 100 is realized.

[0137] In FIG. 6, the first and second displays 11 and 12 are individually moved by the actuator 23 in the direction (X direction) of the optical axis 60. When the first display 11 moves in the direction (right-hand direction) away from the first transmissive mirror 21, the optical path length of the first image light beam 51 is extended by that movement distance. Therefore, the protruding distance of the first mid-air image 71 is also extended by the same movement distance (first mid-air image 71a).

[0138] When the first display 11 moves in the direction (left-hand direction) to the first transmissive mirror 21, the optical path length of the first image light beam 51 is shortened by that movement distance. Therefore, the protruding distance of the first mid-air image 71 is also shortened by the same movement distance (first mid-air image 71b).

[0139] When the second display 12 moves in the direction (left-hand direction) away from the second transmissive mirror 22, the optical path length of the second image light beam 52 is extended by that movement distance. Therefore, the protruding distance of the second mid-air image 72 is also extended by the same movement distance (second mid-air image 72a).

[0140] When the second display 12 moves in the direction (right-hand direction) to the second transmissive mirror 22, the optical path length of the second image light beam 52 is shortened by that movement distance. Therefore, the protruding distance of the second mid-air image 72 is also shortened by the same movement distance (second mid-air image 72b).

[0141] When the respective positions of the first and second displays 11 and 12 are changed in the X direction in this manner, the start point of the optical path of each of the first and second image light beams 51 and 52 is changed. With this configuration, the optical path length of each of the first and second image light beams 51 and 52 is changed, and the protruding distance of each of the first and second mid-air images 71 and 72 is changed by a distance corresponding to the amount of movement.

[0142] By independently moving the first display 11 and the second display 12, the superimposed images of the first mid-air image 71 and the second mid-air image 72 as viewed in the direction of the user’s line of sight can be controlled and displayed with high precision, for example. For example, first of all, the second transmissive mirror 22 is moved and the position of the first mid-air image 71 is greatly changed. After that, the first and second displays 11 and 12 are moved and the respective positions of the first and second mid-air images 71 and 72 are finely adjusted. Such an operation can also be performed.

[0143] Moreover, the respective positions of the third and fourth displays 13 and 14 shown in FIG. 4 may be variable. With this configuration, the image-forming positions of the third and fourth mid-air images 73 and 74 can be controlled as appropriate. As a result, the display of the superimposed images can be controlled with high precision, and a high-level viewing experience can be provided.

[0144] In FIG. 7, the first transmissive mirror 21 is moved by the actuator 23 in the direction (X direction) of the optical axis 60. The first transmissive mirror 21 is moved in the direction (left-hand direction) away from the first display 11 or in the direction (right-hand direction) to the first display 11, for example.

[0145] It should be noted that the angle of inclination .theta. of the first transmissive mirror 21 is not changed.

[0146] When the first transmissive mirror 21 moves in the direction to the first display 11, the distance from the first transmissive mirror 21 to the second transmissive mirror 22 is extended. On the other hand, the distance from the first display 11 to the second transmissive mirror 22 and the distance from the first transmissive mirror 21 to the optical image-forming element 30 are not changed. Therefore, the optical path length (optical paths 81+82+83) of the first image light beam 53 from the first display 11 to the optical image-forming element 30 is extended by a distance equivalent to the amount of movement of the first transmissive mirror 21.

[0147] Moreover, when the first transmissive mirror 21 is moved toward the first display 11, the optical path 83 of the first image light beam 51 from the first transmissive mirror 21 toward the optical image-forming element 30 is translated toward the first display 11. Therefore, an incident position Pa of the first image light beam 51 on the optical image-forming element 30 is moved toward the first display 11. The amount of movement of that incident position Pa is equal to the amount of movement of the first transmissive mirror 21. As a result, as shown in FIG. 8, the first mid-air image 71a is formed at a position protruding from the moved incident position Pa by the optical path length (optical paths 81+82a+83) of the first image light beam 51.

[0148] When the first transmissive mirror 21 moves in the direction away from the first display 11 (direction to the second transmissive mirror 22), the distance from the first transmissive mirror 21 to the second transmissive mirror 22 is shortened. Therefore, the optical path length (optical paths 81+82+83) of the first image light beam 51 from the first display 11 to the optical image-forming element 30 is shortened by a distance equivalent to the amount of movement of the first transmissive mirror 21.

[0149] Moreover, an incident position Pb of the first image light beam 51 moves toward the second transmissive mirror 22 by a distance corresponding to the amount of movement of the first transmissive mirror 21. As a result, as shown in FIG. 8, the first mid-air image 71b is formed at a position protruding from the moved incident position Pb by the optical path length (optical paths 81+82b+83) of the first image light beam 51.

[0150] By moving the first transmissive mirror 21 in the X direction in this manner, the incident position of the first image light beam 51, which enters the optical image-forming element 30, and the optical path length of the first image light beam 51 from the first display 11 to the optical image-forming element 30 can be changed. With this configuration, the image-forming position of the first mid-air image 72 can be adjusted in the X direction, and the mid-air image can be displayed in a manner desired by the user.

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