Búsqueda Imágenes Maps Play YouTube Noticias Gmail Drive Más »
Iniciar sesión
Usuarios de lectores de pantalla: deben hacer clic en este enlace para utilizar el modo de accesibilidad. Este modo tiene las mismas funciones esenciales pero funciona mejor con el lector.

Patentes

  1. Búsqueda avanzada de patentes
Número de publicaciónWO2000007058 A1
Tipo de publicaciónSolicitud
Número de solicitudPCT/US1999/017243
Fecha de publicación10 Feb 2000
Fecha de presentación29 Jul 1999
Fecha de prioridad29 Jul 1998
Número de publicaciónPCT/1999/17243, PCT/US/1999/017243, PCT/US/1999/17243, PCT/US/99/017243, PCT/US/99/17243, PCT/US1999/017243, PCT/US1999/17243, PCT/US1999017243, PCT/US199917243, PCT/US99/017243, PCT/US99/17243, PCT/US99017243, PCT/US9917243, WO 0007058 A1, WO 0007058A1, WO 2000/007058 A1, WO 2000007058 A1, WO 2000007058A1, WO-A1-0007058, WO-A1-2000007058, WO0007058 A1, WO0007058A1, WO2000/007058A1, WO2000007058 A1, WO2000007058A1
InventoresMilan M. Popovich, Jonathan D. Waldern, John J. Storey
SolicitanteDigilens, Inc.
Exportar citaBiBTeX, EndNote, RefMan
Enlaces externos:  Patentscope, Espacenet
Multi-mode visual display using reconfigurable holographic optics
WO 2000007058 A1
Resumen
Visual display apparatus can enable viewing of a display screen in multiple modes that provide different ranges of acceptable viewing angle and/or viewing distances. For example, the visual display apparatus can enable viewing of a display screen in a public mode intended to accommodate viewing of the screen by multiple people (i.e., a mode affording a relatively wide range of acceptable viewing angles) or a private mode intended to accommodate viewing of the display screen by a single person (i.e., a mode affording a relatively narrow range of acceptable viewing angles). In one embodiment reconfigurable holographic optical elements (HOEs) are used to form a virtual image (615) for the private mode and a real image (614) for the public mode. The visual display apparatus is implemented as part of a portable computer and the use of reconfigurable HOE(s) enables the display screen to be made thinner and lighter.
Reclamaciones  (El texto procesado por OCR puede contener errores)
We claim:
1. A display screen, comprising: first means for receiving light representing a visual image and selectively producing a display of the visual image in response to an applied voltage, the first light receiving means producing the display of the visual image in a plane within the display screen; and second means for receiving light representing a visual image and selectively producing a display of the visual image in response to an applied voltage, the second light receiving means producing the display of the visual image in a plane on a side of the display screen opposite that from which a viewer views the display of the visual image.
2. A display screen as in Claim 1, wherein the first and/or second light receiving means further comprises a reconfigurable holographic optical element.
3. A display screen as in Claim 2, wherein each of the first and second light receiving means further comprises a reconfigurable holographic optical element.
4. A display screen as in Claim 2, wherein the first and/or second light receiving means further comprises a plurality of reconfigurable holographic optical elements.
5. A display screen as in Claim 4, wherein each of the first and second light receiving means further comprises a plurality of reconfigurable holographic optical elements.
6. A display screen as in Claim 1, wherein the first light receiving means further comprises a reconfigurable holographic lens and a reflective diffuser.
7. A display screen as in Claim 1, wherein the first light receiving means further comprises a reconfigurable holographic diffuser.
8. A display screen as in Claim 1, wherein the second light receiving means further comprises a reconfigurable holographic mirror.
9. A display screen as in Claim 1, wherein the first light receiving means is adapted to produce a visual image display that results in a range of acceptable viewing angles less than or equal to about 60┬░.
10. A display screen as in Claim 1, wherein the first light receiving means is adapted to produce a visual image display that results in a range of acceptable viewing angles less than or equal to about 5┬░.
11. A display screen as in Claim 1, wherein the first light receiving means is adapted to produce a visual image display that results in a range of acceptable viewing angles less than or equal to about 25┬░.
12. A display screen as in Claim 1, wherein the second light receiving means is adapted to produce a viewing region that is entirely within a range of viewing angles less than or equal to about 5┬░.
13. A display screen as in Claim 1, wherein the second light receiving means is adapted to produce a viewing region that is entirely within a range of viewing angles less than or equal to about 25┬░.
14. A display screen as in Claim 1, wherein the display screen has a viewing area having a diagonal of less than or equal to about 12 inches.
15. A display screen as in Claim 1, wherein the display screen has a viewing area having a diagonal of less than or equal to about 25 inches.
16. A portable computer, comprising a display screen as in Claim 1.
17. A display screen, comprising: first means for receiving light representing a visual image and selectively producing a display of the visual image in response to an applied voltage, the first light receiving means producing a visual image display having a first range of acceptable viewing angles; and second means for receiving light representing a visual image and selectively producing a display of the visual image in response to an applied voltage, the second light receiving means producing a visual image display having a second range of acceptable viewing angles that is different than the first range of acceptable viewing angles .
18. A display screen as in Claim 17, wherein the first light receiving means is adapted to produce a visual image display that results in a range of acceptable viewing angles less than or equal to about 60┬░.
19. A display screen as in Claim 17, wherein the first light receiving means is adapted to produce a visual image display that results in a range of acceptable viewing angles less than or equal to about 5┬░.
20. A display screen as in Claim 17, wherein the first light receiving means is adapted to produce a visual image display that results in a range of acceptable viewing angles less than or equal to about 25┬░.
21. A display screen as in Claim 17, wherein: the first light receiving means is adapted to produce a visual image display that results in a range of acceptable viewing angles less than or equal to about 60┬░; and the second light receiving means is adapted to produce a visual image display that results in a range of acceptable viewing angles less than or equal to about 5┬░.
22. A display screen as in Claim 17, wherein: the first light receiving means is adapted to produce a visual image display that results in a range of acceptable viewing angles less than or equal to about 60┬░; and the second light receiving means is adapted to produce a visual image display that results in a range of acceptable viewing angles less than or equal to about 25┬░.
23. A method for producing a display of a visual image on a display screen, comprising the steps of: receiving light representing a visual image and selectively producing a display of the visual image in response to an applied voltage, wherein the display of the visual image is produced in a plane within the display screen; and receiving light representing a visual image and selectively producing a display of the visual image in response to an applied voltage, wherein the display of the visual image is produced in a plane on a side of the display screen opposite that from which a viewer views the visual image.
24. A method for producing a display of a visual image on a display screen, comprising the steps of: receiving light representing a visual image and selectively producing a display of the visual image in response to an applied voltage, wherein the display of the visual image has a first range of acceptable viewing angles ; and receiving light representing a visual image and selectively producing a display of the visual image in response to an applied voltage, wherein the display of the visual image has a second range of acceptable viewing angles that is different than the first range of acceptable viewing angles .
Descripción  (El texto procesado por OCR puede contener errores)

MULTI-MODE VISUAL DISPLAY USING RECONFIGURABLE HOLOGRAPHIC OPTICS

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon, and claims priority of, the commonly-owned, co-pending U.S. Provisional Patent Application Serial No. 60/094,508, entitled "Dual Purpose Laptop Computer Displays Based on Reconfigurable Holographic Optics," by Milan M. Popovich et al. , filed on July 29, 1998, the disclosure of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention This invention relates to visual display apparatus and, in particular, to visual display apparatus that enables a display screen (which can be implemented using reconfigurable holographic optical elements) to be viewed in multiple modes providing different ranges of acceptable viewing angles and/or different viewing distances.

2. Related Art

It is an ongoing challenge to improve the characteristics of visual display apparatus. Moreover, the device with which visual display apparatus is to be used can place particular constraints on the visual display apparatus, such as limitations regarding the size and/or weight of the display screen or other components of the visual display apparatus, or limitations related to the expected distance from the display screen or the viewing angle with respect to the display screen at which a viewer will typically be position.

For example, the construction and intended use of a portable computer can place significant constraints (e.g., limitations regarding size, weight, expected typical viewer distance from the display screen) on the visual display apparatus. Portable computers include, for example, notebook computers, sub-notebook computers and personal digital assistants. Many portable computers include two relatively thin rectangular sections that are attached to each other with one or more hinges so that the two sections can be rotated between open and closed positions. One section ("user input section") typically includes a keyboard (and, in some cases, other user input apparatus) and houses various computational devices. The other section ("display section") houses electronics for producing a visual display that is perceived to be in a plane within the display section and includes a display screen that is used to present the visual display to a user. As those in the art realize, the provision of visual display apparatus for use with a portable computer can be particularly challenging.

The range of acceptable viewing angles (i.e., viewing angles at which adequate light intensity exists over a full field of view from that viewing angle) of a visual display can be affected by the polar diagram produced by the visual display apparatus and the distance of the viewer from the display screen. In a portable computer, the expected typical viewing distance is typically determined by the intended application (s) of the portable computer and the quality (e.g., resolution) of the display produced by the display electronics. For example, for a laptop computer (which typically has a viewing area with a diagonal of about 12 inches) , the expected typical distance of the viewer from the display screen is between 18 and 24 inches. For a handheld computer (which typically has a viewing area with a diagonal of about 5 inches) , the expected typical distance of the viewer from the display screen is shorter than that for a laptop computer. Thus, as can be appreciated, the range of acceptable viewing angles for the display screen of a portable computer may be limited more than desired.

Current portable computer visual display apparatus do not enable the range of acceptable viewing angles or the viewing distance (for a fixed viewer position) to be changed. (As indicated above, the visual display is produced so that the visual display is perceived to be in a plane within the display section of the portable computer.) Such capability can be desirable to facilitate use of the portable computer for different purposes and/or in different situations. It is generally desirable to make the components of a portable computer small and lightweight. The visual display apparatus (i.e., display screen and associated drive electronics) of a portable computer typically comprises a significant portion of the overall weight of the portable computer. Therefore, for visual display apparatus used with a portable computer, it is of particular importance to reduce the size and weight of the visual display apparatus. Current portable computers typically include an LCD or an electroluminescent display screen. The thickness, weight and power consumption of such display screens and their associated drive electronics is greater than desired.

SUMMARY OF THE INVENTION

Visual display apparatus according to the invention can enable viewing of a display screen in multiple modes that provide different ranges of acceptable viewing angles and/or different viewing distances. The provision of multiple viewing modes facilitates use of the display screen for different purposes and/or in different situations. For example, visual display apparatus according to the invention can enable viewing of a display screen in a public mode intended to accommodate viewing of the display screen by multiple people (i.e., a mode affording a relatively wide range of acceptable viewing angles) or a private mode intended to accommodate viewing of the display screen by a single person (i.e., a mode affording a relatively narrow range of acceptable viewing angles) . Visual display apparatus according to the invention can also enable viewing in different modes that enable viewing of an image at different viewing distances.

The functions of a visual display apparatus according to the invention can be accomplished using one or more reconfigurable holographic optical elements (HOEs) that can be switched between an operative (active) and an inoperative (passive) state. (In some embodiments of the invention, the reconfigurable HOE(s) may be switched among an inoperative state, an operative state, and one or more partially operative states.) In particular, reconfigurable HOE(s) can be used in the display screen. The use of reconfigurable HOE(s) in a display screen makes the invention particularly useful when implemented as part of a portable computer, since the use of reconfigurable HOE(s) in the display screen enables the display screen to be made thinner and lighter than would otherwise be the case. Additionally, the use of reconfigurable HOE(s) improves viewability by producing a bright, high contrast image.

In one embodiment of the invention, a display screen includes first and second means for receiving light representing a visual image and selectively producing a display of the visual image in response to an applied voltage. The first light receiving means produces a visual image in a plane within the display screen, while the second light receiving means produces a visual image in a plane on a side of the display screen opposite that from which a viewer views the image.

In another embodiment of the invention, a display screen includes first and second means for receiving light representing a visual image and selectively producing a display of the visual image in response to an applied voltage. The first and second light receiving means produce visual image displays having a different ranges of acceptable viewing angles .

Either or both of the first and second light receiving means can include one or more reconfigurable HOEs. In a particular embodiment, the first light receiving means includes a reconfigurable holographic lens and a reflective diffuser. In another particular embodiment, the first light receiving means includes a reconfigurable holographic diffuser. In still another particular embodiment, the second light receiving means includes a reconfigurable holographic mirror.

In a particular embodiment of a display screen according to the embodiments of the invention described above, one of the light receiving means produces a visual image display that results in a range of acceptable viewing angles less than or equal to about 60°. In another particular embodiment, one of the light receiving means produces a visual image display that results in a range of acceptable viewing angles less than or equal to about 5°. In still another particular embodiment, one of the light receiving means produces a visual image display that results in a range of acceptable viewing angles less than or equal to about 25°. In yet another particular embodiment, one of the light receiving means produces a visual image display that results in a range of acceptable viewing angles less than or equal to about 60°, while the other of the light receiving means produces a visual image display that results in a range of acceptable viewing angles less than or equal to about 5°. In still another particular embodiment, one of the light receiving means produces a visual image display that results in a range of acceptable viewing angles less than or equal to about 60°, while the other of the light receiving means produces a visual image display that results in a range of acceptable viewing angles less than or equal to about 25°. Visual display apparatus according to the invention can be used in a variety of devices, such as computers. Visual display apparatus according to the invention can be particularly advantageously used with any device in which it is important to minimize the size and/or weight of visual display apparatus that is part of the device, such as a portable computer. Visual display apparatus according to the invention is generally intended for applications in which the display screen is relatively small (e.g., display screens having a viewing area with a diagonal less than about 25 inches, such as are commonly found in desktop computers, display screens having a viewing area with a diagonal of about 12 inches or less, such as are commonly found in laptop computers, or display screens having a viewing area with a diagonal of about 5 inches or less, such as are commonly found in laptop computers.

In still another embodiment of the invention, a method for producing a display of a visual image on a display screen includes the two different steps of receiving light representing a visual image and selectively producing a display of the visual image in response to an applied voltage. In one of the steps of receiving, the display of the visual image is produced in a plane within the display screen, while in the other of the steps of receiving the display of the visual image is produced in a plane on a side of the display screen opposite that from which a viewer views the visual image .

In yet another embodiment of the invention, a method for producing a display of a visual image on a display screen includes two steps of receiving light representing a visual image and selectively producing a display of the visual image in response to an applied voltage. The two steps of receiving produce visual image displays having different ranges of acceptable viewing angles. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram illustrating the formation of a real image.

FIG. IB is a schematic diagram illustrating the production of a visual image display having a relatively narrow polar diagram.

FIG. 1C is a schematic diagram illustrating the production of a visual image display having a relatively broad polar diagram. FIGS. 2A and 2B are schematic diagrams illustrating, respectively, the formation of a virtual visual image behind a display screen and in front of a display screen.

FIG. 3 is a perspective view of a portable computer including display apparatus according to the invention. FIG. 4A is a cross-sectional view of a display screen according to an embodiment of the invention.

FIG. 4B is a detailed view of a region of the display screen shown in FIG. 4A, illustrating the private mode of operation of the display screen. FIG. 4C is a detailed view of a region of the display screen shown in FIG. 4A, illustrating the public mode of operation of the display screen.

FIG. 5A is a cross-sectional view of a display screen according to another embodiment of the invention. FIG. 5B is a detailed view of a region of the display screen shown in FIG. 5A, illustrating the public mode of operation of the display screen.

FIG. 6A is a schematic diagram of part of a display apparatus according to an embodiment of the invention, illustrating the regions in both the private mode and the public mode of operation of the display apparatus within which a full field of view can always be adequately viewed.

FIG. 6B is a schematic diagram of the entire display apparatus of FIG. 6A. FIG. 7 is a schematic diagram of a display apparatus according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

According to the invention, a visual display apparatus can enable viewing of a display screen in multiple modes that provide different ranges of acceptable viewing angles and/or different viewing distances. In particular, a visual display apparatus according to the invention can enable viewing of a display screen in a public mode intended to accommodate viewing of the display screen by multiple people (i.e., a mode affording a relatively wide range of acceptable viewing angles) or a private mode intended to accommodate viewing of the display screen by a single person (i.e., a mode affording a relatively narrow range of acceptable viewing angles) . A visual display apparatus according to the invention can also enable viewing in different modes that enable viewing of an image at different viewing distances. (Herein, "viewing distance" refers to the distance from a viewer to a plane in which the viewer perceives a visual display to be produced. ) A visual display apparatus according to the invention can be implemented using one or more reconfigurable holographic optical elements (HOEs) that can be placed in an operative (active) state, a partially operative state, or an inoperative (passive) state. In particular, reconfigurable HOE(s) can be used in the display screen, thus enabling the display screen to be made thinner and lighter than would otherwise be the case. Thus, the invention can be particularly useful when implemented in devices in which the size and/or weight of the visual display apparatus is of particular concern, such as a portable computer.

Additionally, the use of reconfigurable HOE(s) in the display screen improves viewability by producing a bright, high contrast image.

As used herein, "public mode" refers to operation of a visual display apparatus to produce a visual image display that can be viewed by multiple viewers and, in particular, to produce a visual image display that results in a larger range of acceptable viewing angles than that associated with a visual image display produced during a private mode (discussed below) of operation of the visual display apparatus. In one embodiment of the invention, public mode operation of visual display apparatus according to the invention produces a visual image display that results in a range of acceptable viewing angles less than or equal to about 60°. In other embodiments of the invention, public mode operation of visual display apparatus according to the invention produces a visual image display that results in a range of acceptable viewing angles less than or equal to an angular value greater than about 60°. The particular range of acceptable viewing angles that defines a public mode of operation can be established in view of the desired viewing capabilities during the private mode of operation (e.g. , to enable an anticipated number of viewers to view the visual image) , as discussed further below. Typically, in a public mode of operation of a visual display apparatus, a "real" visual image display (i.e., a display of a visual image that is perceived by a viewer as located within a display screen of the display apparatus) is produced. (Herein, for convenience, a "real visual image display" is sometimes referred to simply as a "real image.")

Herein, "viewing angle" is the angle between a line passing through the center of, and perpendicular to, a viewing surface of a display screen and a line representing a viewer's line of sight through the center of the viewing surface of the display screen. Additionally, herein, an "acceptable viewing angle" is a viewing angle at which adequate light intensity exists over a full field of view from that viewing angle. (Herein, "light intensity" is used to indicate the amount of light transmitted to a viewer's eye.) Herein, adequate light intensity over a full field of view can be said to exist if the viewer can readily discern the entire visual image display. Typically, when adequate light intensity exists over a full field of view, the maximum light intensity within the full field of view is no more than about 50% greater than the minimum light intensity within the field of view.

FIG. 1A is a schematic diagram illustrating the formation of a real image. The image is formed at a location (in accordance with the particular implementation of the visual display apparatus) within a display screen 101. Edges of the image are displayed on the display screen at the locations 101a and 101b, i.e., in the plane of FIG. 1A, the entire image lies between the locations 101a and 101b. The center of the display screen 101 is designated by the numeral 101c. A viewer 102 views the image along a viewing angle of 0°, i.e., along the line passing through the center of, and perpendicular to, the viewing surface of the display screen 101. The angle 105 indicates a full field of view of the viewer 102 (i.e., the viewer can see the entire image). A viewer 103 views the image along a non-zero viewing angle 104. The angle 106 indicates a full field of view of the viewer 103.

FIG. IB is a schematic diagram illustrating the production of a visual image display having a relatively narrow polar diagram. The polar diagram is represented by the ovals encircling the light rays (designated generally by the numeral 107) emanating from the display screen 101. The intensity of each light ray 107 corresponds to the length of the arrow representing the light ray (a shorter arrow represents less light intensity) . For the relatively large viewing angle 104, the intensity of light emanating from the display screen 101 near the edge 101b of the image may be insufficient to adequately convey the image to the viewer 103. FIG. 1C is a schematic diagram illustrating the production of a visual image display having a relatively broad polar diagram. The polar diagram is represented by the ovals encircling the light rays (designated generally by the numeral 108) emanating from the display screen 101. As can be appreciated, for the relatively large viewing angle 104, the intensity of light emanating from the display screen 101 near the edge 101b of the image is greater than that in FIG. IB. Thus, production of a real image visual display with a broad polar diagram can enable the visual display to be adequately viewed from larger viewing angles . The invention can make use of such effect (i.e., variation in the polar diagram to produce visual image displays that can be adequately viewed within different ranges of viewing angles) to enable viewing of a visual image display in different modes that accommodate viewing over different ranges of acceptable viewing angles.

As used herein, "private mode" refers to operation of a visual display apparatus to produce a visual image display that can only be comfortably viewed in its entirety by a single viewer and, in particular, to produce a visual image display that results in a smaller range of acceptable viewing angles than that associated with a visual image display produced during a public mode (discussed above) of operation of the visual display apparatus. In one embodiment of the invention, private mode operation of visual display apparatus according to the invention produces a visual image display that results in a range of acceptable viewing angles less than or equal to about 5°. In another embodiment of the invention, private mode operation of visual display apparatus according to the invention produces a visual image display that results in a range of acceptable viewing angles less than or equal to about 25°. In other embodiments of the invention, private mode operation of visual display apparatus according to the invention produces a visual image display that results in a range of acceptable viewing angles less than or equal to angular values between about 5° and about 25° (e.g., 10°, 15°, 20°). The particular range of acceptable viewing angles that defines a private mode of operation can be established in view of the desired constraints on viewing of the visual image during the private mode of operation (e.g., to minimize the possibility that unauthorized viewers can view the visual image) , as discussed further below. In some embodiments of the invention, in a private mode of operation of a visual display apparatus, a "real" visual image display is produced. In other embodiments of the invention, in a private mode of operation of a visual display apparatus, a "virtual" visual image display (i.e., a display of a visual image that is perceived by a viewer as located in a plane outside of a display screen of the display apparatus) is produced behind a display screen of the visual display apparatus (i.e., in a plane on a side of the display screen opposite that from which a viewer views the visual image display) . (Herein, for convenience, a "virtual visual image display" is sometimes referred to simply as a "virtual image.")

FIGS. 2A and 2B are schematic diagrams illustrating, respectively, the formation of a virtual image by a mirror or a lens. In FIG. 2A, the light rays 201a, 201b, 201c and 20Id, emanating from the extremities of an input image 202, are projected toward a mirror 203. As appreciated by those skilled in the art of optics, the light rays 201a, 201b, 201c and 201d are reflected from the mirror 203 in accordance with the optical characteristics (in particular, focal length) of the mirror 203, as determined by the particular construction of the mirror 203. If the input image 202 is located at a distance from the mirror 203 that is less than the focal length of the mirror 203, then reflection of the light rays 201a, 201b, 201c and 201d from the mirror 203 produces a virtual image 204 that appears to a viewer (not shown, but positioned to the left of the mirror 203 in FIG. 2A) to be located behind the mirror 203 (i.e., to the right of the mirror 203 in FIG. 2A) . The size of the input image 202, the location of the input image 202 with respect to the mirror 203, and the optical characteristics of the mirror 203 establish the size of the virtual image 204 and the distance of the virtual image 204 behind the mirror 203, as well as the size and shape of a region (indicated in FIG. 2A by the shaded region to the left of the mirror 203) within which a viewer can perceive the entire virtual image 204 (i.e., a full field of view). (Outside of the shaded region, a viewer can perceive part or none of the virtual image 204, i.e., a partial field of view or no field of view, depending on the location of the viewer. )

In FIG. 2B, the light rays 211a, 211b, 211c and 211d, representing an input image 212, are projected toward a lens 213. As appreciated by those skilled in the art of optics, the light rays 211a, 211b, 211c and 211d are refracted by the lens 213 in accordance with the optical characteristics of the lens 213, as determined by the particular construction of the lens 213. If the input image 212 is located at a distance from the lens 213 that is less than the focal length of the lens 213, then refraction of the light rays 211a, 211b, 211c and 211d from the lens 213 produces a virtual image 214 that appears to a viewer (not shown, but positioned to the right of the lens 213 in FIG. 2B) to be located behind the lens 213 (i.e., to the left of the lens 213 in FIG. 2A) . The size of the input image 212, the location of the input image 212 with respect to the lens 213, and the optical characteristics of the lens 213 establish the size of the virtual image 214 and the distance of the virtual image 214 behind the lens 213, as well as the size and shape of a region (indicated in FIG. 2A by the shaded region to the right of the lens 213) within which a viewer can perceive the entire virtual image 214 (i.e, a full field of view). (Again, outside of the shaded region, a viewer can perceive part or none of the virtual image 214, depending on the location of the viewer.) Illustratively, in a particular embodiment of the invention, a virtual image (private mode) can be produced so that the viewer perceives the image to be about 10 feet behind the display screen. This distance has been found to provide a relatively high level of viewing comfort, e.g., does not necessitate an undesirable amount of eye adjustment, such as re-focusing and eye convergence adjustment, on the part of the viewer to enable the image to be viewed.

Visual display apparatus according to the invention is generally intended for use in situations in which the distance from a viewer to the display screen is relatively small, i.e., several inches (e.g., about 6 inches) to several feet (e.g., about 5 feet). The particular embodiments of the invention discussed herein contemplate use in such situations. Further, visual display apparatus according to the invention is generally intended for applications in which the display screen is relatively small (e.g., display screens having a viewing area with a diagonal less than about 25 inches). In particular, as discussed elsewhere herein, visual display apparatus according to the invention can be advantageously used in a portable computer, including, for example, laptop computers (current versions of which typically include a display screen having a viewing area with a diagonal of about 12 inches or less) and handheld computers (current versions of which typically include a display screen having a viewing area with a diagonal of about 5 inches or less) .

When a virtual image is produced behind the display screen (private mode) , the range of acceptable viewing angles that completely contain the viewing region is small (see, e.g., FIGS. 2A and 2B, described above), as a consequence of the geometry of the optics associated with the production of the virtual image, which result in a display exit pupil that is significantly smaller than the dimensions of the display screen, as known to those skilled in the art. In particular, the range of acceptable viewing angles is significantly smaller than that when a real image is produced in the display screen (public mode, some embodiments of private mode) . Further, the polar diagram of a real image display in public mode can be controlled to produce a relatively large range of acceptable viewing angles (and, in particular, a range of acceptable viewing angles that is larger than that associated with a real image to be used in private mode operation). Thus, public mode operation is appropriate for viewing of an image by multiple viewers, while the relatively more restricted range of acceptable viewing angles in private mode makes that mode appropriate for viewing of an image by a single viewer. Similarly, the larger range of acceptable viewing angles in public mode makes that mode appropriate for viewing of an image in situations where the concern with viewing of the image by unauthorized viewers is relatively small, while the more restricted range of acceptable viewing angles in private mode makes that mode appropriate for viewing of an image in situations where the need to ensure that the image is not viewed by unauthorized viewers is relatively great.

When a real image is produced in the display screen (public mode, some embodiments of private mode) , the display apparatus cannot be used to change the distance of a viewer from the image (aside from moving the display screen) . In contrast, when a virtual image is produced (private mode), the construction and/or operation of the display apparatus can be controlled to establish any desired distance of a viewer from the image (up to, and including, an infinite distance) . The flexibility in establishing viewing distance in private mode operation can be desirable, for example, to enable matching of the viewing distance with the distance to an object (e.g., when the invention is implemented with a computer, a document from which the viewer is obtaining information to enter into the computer) with which it is anticipated the viewer will also visually interact during viewing of the image on the display screen.

When a real image is produced in the display screen (public mode, some embodiments of private mode) , the size of the image cannot be larger than allowed by the size of the display screen. In contrast, when a virtual image is produced outside of the display screen (private mode) , the size of the visual image is not limited by the size of the display screen (theoretically, any size visual image can be produced) . The flexibility in establishing image size in private mode operation can be desirable, like the flexibility in establishing viewing distance, to match the image size with the size of an object with which it is anticipated the viewer will also visually interact during viewing of the image on the display screen. The production of a real or virtual image by visual display apparatus according to the invention can be accomplished in a variety of ways. In particular, one or more reconfigurable HOEs can be used for such purpose. More particularly, one or more reconfigurable HOEs can be used to implement a display screen of visual display apparatus according to the invention. As indicated above, the use of reconfigurable HOE(s) in a display screen enables the display screen to be made thinner and lighter than would otherwise be the case, and improves viewability by producing a bright, high contrast image. Particular implementations of display apparatus according to the invention in which one or more reconfigurable HOEs are used to produce a real and/or virtual image are described below. Following is a general description of the construction and operation of a reconfigurable HOE. Each reconfigurable HOE includes a hologram coupled to electrical elements (e.g., positioned between electrode layers) that enable a voltage to be applied across the hologram. The hologram is constructed (as can be accomplished by those skilled in the art) to produce desired optical characteristics (e.g., reflection, refraction, diffusion) and, in general, can replicate the functional behavior of one or more conventional optical devices (e.g., mirror, lens, diffuser). It is desirable that the hologram be a Bragg-type hologram in order to achieve a high diffraction efficiency. The hologram can be constructed using any appropriate materials and processes, as known to those skilled in the art. For example, a hologram for use with the invention can be made by recording a holographic image (using a conventional optical or laser process) on a polymer-dispersed liquid crystal (PDLC) material. Materials and methods that can be used in constructing a hologram for use with the invention are described in more detail in PCT Application No. PCT/US97/12577 , entitled "Switchable Volume Hologram Materials and Devices," by Richard L. Sutherland et al., filed on July 11, 1997, the disclosure of which is incorporated by reference herein. If electrode layers are used to apply the voltage across the hologram, the electrode layers are made of a transparent conductive material, such as indium tin oxide. Methods that can be used to construct a reconfigurable HOE for use with the invention are also described in more detail in the commonly-owned, co-pending U.S. Patent Application Serial No. 09/351,412, entitled "Projection Systems Based on Reconfigurable Holographic Optics," by Milan M. Popovich et al., filed on July 9, 1999, the disclosure of which is incorporated by reference herein.

When no voltage is applied across the hologram, the reconfigurable HOE is said to be in an active state and light passing through the hologram is affected (e.g., reflected, refracted, diffused) in accordance with the optical characteristics of the hologram. When a voltage of adequate magnitude is applied across the hologram, the reconfigurable HOE is said to be in a passive state and light passing through the hologram is not affected by the optical characteristics of the hologram. If the reconfigurable HOE is made of PDLC, it is also possible to apply a voltage across the hologram having a magnitude between zero and the passive state voltage, which puts the reconfigurable HOE in a partially active state in which light passing through the hologram is affected to an intermediate degree (depending on the magnitude of the voltage) in accordance with the optical characteristics of the hologram.

The holograms in a reconfigurable HOE for use with the invention are designed and constructed to have optical characteristics that, alone or in combination with other optical devices, produce a desired real image and/or virtual image in view of the structure of other display apparatus. As indicated above, the holograms in a reconfigurable HOE for use with the invention can be designed and constructed to produce characteristics that replicate any type of optical device that may be useful in enabling the production of a real and/or virtual image in display apparatus according to the invention.

As indicated above, a visual display apparatus according to the invention (and, in particular, a display screen of a visual display apparatus according to the invention) can be implemented using reconfigurable HOEs. However, other optical apparatus, such as non-reconfigurable HOEs (i.e., HOEs that are always in the active state) , can also be used. The use of reconfigurable HOEs, rather than non- reconfigurable HOEs, may be preferable because the capacity to switch a reconfigurable HOE between an active and passive state enables HOEs that are proximate to each other (e.g., adjacent) to be appropriately controlled to reduce (and, perhaps, eliminate) optical interference and/or crosstalk between the proximate HOEs. For example, in visual display apparatus for producing a color display, it can be advantageous to construct an optical element using a stack of HOEs, each HOE being designed to propagate a particular wavelength (i.e., color) of light. Optical interference and/or crosstalk among the HOEs of such a stack can be reduced (and, perhaps, eliminated) by using reconfigurable HOEs and sequentially placing the HOEs in the active state (as opposed to using non-reconfigurable HOEs which are always simultaneously in the active state) to propagate the corresponding wavelengths of light. (Other components of the optical system would be synchronously operated to propagate the appropriate wavelength of light at the appropriate times . ) FIG. 3 is a perspective view of a portable computer 300 including display apparatus according to the invention. The portable computer 300 includes two sections 301 and 302. The sections 301 and 302 are attached to each other with one or more hinges so that the two sections can be rotated between open and closed positions. The section 301 includes input mechanisms (e.g., a keyboard) that a user of the portable computer 300 can use to effect operation of the portable computer 300. The section 302 includes a display screen 303 that is used to present a visual display to the user. A projection system 304 is positioned within the section 301 and projects light rays 305 toward the display screen 303. The projection system 304 and display screen 303 are implemented in accordance with the invention, as explained elsewhere herein, to enable viewing of the display screen 303 in multiple modes (e.g. public mode and private mode as described above) .

FIG. 4A is a cross-sectional view of a display screen 400 according to an embodiment of the invention. The display screen 400 can be used, for example, to embody the display screen 303 of the portable computer 300 of FIG. 3. The display screen 400 includes a reconfigurable holographic mirror 401, a reconfigurable holographic lens 402 and a reflective diffuser 403. The reconfigurable holographic mirror 401 and reconfigurable holographic lens 402 are constructed (using, for example, methods and materials as described above) to produce the optical characteristics discussed below. The reflective diffuser 403 can be embodied by a conventional such optical device, which can be constructed, for example, by applying a reflective coating (such as, for example, a coating of aluminum, silver or a combination of a dielectric and metallic material, as known to those skilled in the art) to a diffusing material (such as, for example, ground glass, an optical acrylic material, or a light-shaping diffusing material such as is made by Physical Optics Corporation of Torrance, California), as known to those skilled in the art.

A projection system (not shown) is positioned to the left (as illustrated in FIG. 4A) of the display screen 400. The projection system projects light rays toward the display screen 400. The light rays are reflected to (as described further below) - and an image formed in - a viewing region (described further below) , which is also located to the left of the display screen, in accordance with a selected mode of operation of the display screen 400. FIG. 4B is a detailed view of the region 4A of the display screen 400 shown in FIG. 4A, illustrating a private mode of operation of the display screen 400. In private mode, the reconfigurable holographic mirror 401 is in an active state. (Since the holographic mirror 401 reflects the incident light, the reconfigurable holographic lens 402 can be in either an active or passive state.) A light ray 410 projected toward the display screen 400 strikes the reconfigurable holographic mirror 401 and is reflected to a viewing region in accordance with the characteristics of the reconfigurable holographic mirror 401. In particular, light rays are reflected so that a virtual image is formed behind the display screen 400 (i.e., to the right of the display screen, as illustrated in FIG. 4B) . The reconfigurable holographic mirror 401 is designed, as understood by those skilled in the art, in view of the incident angle of light rays striking the reconfigurable holographic mirror 401 (i.e., in view of the position of the projection system relative to the reconfigurable holographic mirror 401) , to produce the virtual image at a specified distance behind the display screen 400 and to produce a viewing region of desired shape .

FIG. 4C is a detailed view of the region 4A of the display screen 400 shown in FIG. 4A, illustrating the public mode of operation of the display screen 400. In public mode, the reconfigurable holographic mirror 401 is in the passive state and the reconfigurable holographic lens 402 is in an active state. Since the reconfigurable holographic mirror 401 is in the passive state, a projected light ray 420 passes through the reconfigurable holographic mirror 401 without being affected. The reconfigurable holographic lens 402 is designed, as understood by those skilled in the art, so that when the light ray 420 strikes the reconfigurable holographic lens 402 the light ray 420 is diffracted toward the reflective diffuser 403 at angle that causes the light ray 420 to strike the reflective diffuser 403 at an angle that maximizes (or maximizes as much as possible in view of other criteria for constructing the display screen 400) the diffusion efficiency of the diffuser 400. Parts of the light ray 420 are reflected from the reflective diffuser 403 over a wide range of angles, as known to those skilled in the art, in accordance with the optical characteristics of the reflective diffuser 403. The reflection of light from the reflective diffuser 403 causes a real image to be formed at the location of the reflective diffuser 403 (i.e., within the display screen 400). In accordance with the optical characteristics of the reflective diffuser 403, the real image has a range of acceptable viewing angles associated therewith, as discussed in more detail elsewhere herein. FIG. 5A is a cross-sectional view of a display screen 500 according to another embodiment of the invention. The display screen 500 can also be used, for example, to embody the display screen 303 of the portable computer 300 of FIG. 3. The display screen 500 includes a reconfigurable holographic mirror 501 and a reconfigurable holographic diffuser 502. The reconfigurable holographic mirror 501 and reconfigurable holographic diffuser 502 are constructed (using, for example, methods and materials as described above) to produce the optical characteristics discussed below. A projection system (not shown) positioned to the left (as illustrated in FIG. 5A) of the display screen 500 projects light rays toward the display screen 500 that are reflected to a viewing region which is also located to the left of the display screen. In private mode, the reconfigurable holographic mirror 501 is in an active state and the reconfigurable holographic diffuser 502 is in the passive state, so that a light ray 510 projected toward the display screen 500 strikes the reconfigurable holographic mirror 501 and is reflected to a viewing region in accordance with the characteristics of the reconfigurable holographic mirror 501, as understood by those skilled in the art. The reconfigurable holographic mirror 501 is designed, as understood by those skilled in the art, to produce a virtual image at a specified distance behind the display screen 500 and to produce a viewing region of desired shape.

FIG. 5B is a detailed view of the region 5A of the display screen 500 shown in FIG. 5A, illustrating the public mode of operation of the display screen 500. In public mode, the reconfigurable holographic mirror 501 is in the passive state and the reconfigurable holographic diffuser 502 is in an active state. A projected light ray 510 passes through the reconfigurable holographic mirror 501 and is reflected from the reconfigurable holographic diffuser 502 over a wide range of angles, in accordance with the optical characteristics of the reconfigurable holographic diffuser 502, as understood by those skilled in the art, forming a real image at the location of the reconfigurable holographic diffuser 502 (i.e., within the display screen 500) . In accordance with the optical characteristics of the reconfigurable holographic diffuser 502, the real image has a range of acceptable viewing angles associated therewith, as discussed in more detail elsewhere herein. As can be appreciated by comparing FIGS. 4A-4C and the associated description to FIGS. 5A and 5B and the associated description, the display screen 500 is formed by replacing the reconfigurable holographic lens 402 and reflective diffuser 403 of the display screen 400 with the reconfigurable holographic diffuser 502. Use of the display screen 500 in lieu of the display screen 400 can be desirable for several reasons. For example, the display screen 500 can be made thinner than the display screen 400 (due to the substitution of the reconfigurable holographic diffuser 502 for the reconfigurable holographic lens 402 and reflective diffuser 403). This can be desirable because it enables reduction in the size and weight of the display screen (and, thus, the apparatus, such as a portable computer, with which the display screen is used) . Since no reflective diffuser 403 is present, the display screen 500 can be made transparent, if desired, by appropriately placing both the reconfigurable holographic mirror 501 and the reconfigurable holographic diffuser 502 in the passive state. (If multiple reconfigurable holographic mirrors and associated diffusers are used to implement a display screen similar to the display screen 500, such a display screen can be made partly transparent, if desired, by appropriately placing one or more pairs of reconfigurable holographic mirror and diffuser in the passive state.) This might be useful, for example, to enable a viewer to view a document with which the viewer is working that is positioned behind the display screen, or just to generally be aware of the viewer's surroundings located behind the display screen. The reconfigurable holographic diffuser 502 can be made thinner than the reconfigurable holographic lens 402, thus making it easier (i.e., require a lower switching voltage and, therefore, less power) to switch the reconfigurable holographic diffuser 502 between active and passive states than it is to switch the reconfigurable holographic lens 402. This is desirable because it reduces power consumption by the display screen. Since there are fewer optical components in the display screen 500 than in the display screen 400, the amount of stray light escaping from the display screen 500 is less than that in the display screen 400, in particular because no light is diffracted back from the display screen 500 through the projection optics, as is the case with the reconfigurable holographic lens 402 and reflective diffuser 403. Thus, the efficiency of the display screen 500 can be higher (producing better brightness and contrast) than that of the display screen 400. It is also possible to tailor the diffusion characteristics of the reconfigurable holographic diffuser 502 more precisely than it is with the reflective diffuser 403 (typically made of ground glass, which provides few properties that can be varied - and little capability of varying those that can - to change the diffusion characteristics) . This can be useful, for example, to produce a visual display having a polar diagram in which light intensity is maximized within the range of anticipated normal viewing angles (e.g., +/- 50°). On the other hand, the reconfigurable holographic diffuser 502 can be more complicated to design than the reconfigurable holographic lens 402 and the reflective diffuser 403. This can disadvantageously increase the cost of developing the display screen.

In the display screens 400 and 500 described above, a reconfigurable holographic mirror 401 or 501, respectively, is used to produce a virtual image in a private mode of operation of the display screen 400 or 500. Alternatively, the display screens 400 or 500 (or other display screens in accordance with the invention) can implemented so that a reconfigurable holographic diffuser is used to produce a real image in a private mode of operation of the display screen 400 or 500. The optical characteristics of the reconfigurable holographic diffuser are tailored, as understood by those skilled in the art, to produce a polar diagram resulting a relatively narrow range of acceptable viewing angles, in accordance with the description above of the private mode of operation of visual display apparatus according to the invention.

FIG. 6A is a schematic diagram of part of a display apparatus 600 according to an embodiment of the invention (the remainder of the display apparatus 600 is shown in FIG. 6B, discussed below), illustrating the regions in both the private mode and the public mode of operation of the display apparatus 600 within which a full field of view can always be adequately viewed (a "viewing region"). The display apparatus 600 includes a reconfigurable holographic mirror 601 and a reconfigurable holographic diffuser 602, which together form a display screen 609. The display apparatus 600 also includes a passive diffuser 603, public mode projection optics 604 and private mode projection optics 605.

The public mode projection optics 604 and private mode projection optics 605 can each be implemented using conventional optical apparatus, as known to those skilled in the art of optics. A "miniature" or "micro" projection system (e.g., a system including an input image display panel having a diagonal less than or equal to about 12 mm, such as can be manufactured using LCD on silicon technology) , as known to those skilled in the art, can advantageously be used. Additionally, the public mode projection optics 604 and private mode projection optics 605 can each be implemented using reconfigurable HOEs. In particular, the public mode projection optics 604 and private mode projection optics 605 can be implemented using methods and apparatus as described in the above-mentioned U.S. Patent Application Serial No. 09/351,412.

During the private mode of operation of the display apparatus 600, the private mode projection optics 605 projects light representing an image on to the passive diffuser 603, such that a magnified version of the image

(indicated by the bi-directional arrow 615) is formed at the passive diffuser 603. The orientation of the private mode projection optics 605 with respect to the passive diffuser 603 and the optical characteristics of the passive diffuser 603 are established so that light is diffracted by the passive diffuser 603 toward the display screen 609. The reconfigurable holographic mirror 601 is in an active state, while the reconfigurable holographic diffuser 602 is in the passive state. The light impinging on the display screen 609 is reflected by the holographic mirror 601. The holographic mirror 601 is designed and constructed to have optical characteristics that result in the formation of a virtual image behind the display screen 609 (i.e., to the right of the display screen 609 in FIG. 6A) . The dashed lines 611a and 611b in FIG. 6A show the upper and lower limits of the light rays representing the image. In particular, the part of the dashed lines 611a and 611b representing light reflected by the holographic mirror 601 define the viewing region in the private mode of operation of the display apparatus 600. During the public mode of operation of the display apparatus 600, the public mode projection optics 604 projects light representing an image toward the display screen 609. The reconfigurable holographic mirror 601 is in the passive state, while the reconfigurable holographic diffuser 602 is in an active state . The light impinging on the display screen 609 passes through the reconfigurable holographic mirror and is reflected by the reconfigurable holographic diffuser 602. The solid lines 612a and 612b in FIG. 6A show the upper and lower limits of the light rays representing the image. (The image is represented in the reconfigurable holographic diffuser 602 by the bi-directional arrow 614.) In particular, the part of the solid lines 612a and 612b representing light reflected by the reconfigurable holographic diffuser 602 define the viewing region in the public mode of operation of the display apparatus 600.

As can be seen, the viewing region during the private mode of operation is smaller than the viewing region during the public mode of operation. As can be appreciated, the public mode of operation can be appropriate to enable viewing by multiple viewers, while the private mode of operation is appropriate to enable viewing by a single viewer.

FIG. 6B is a schematic diagram of the entire display apparatus 600. The display apparatus 600 further includes a light source 606, a display panel 607, a beam splitting cube 608, a beam condenser, a color filter (not shown) and a diffuser (not shown). The light source 606, display panel 607, beam splitting cube 608, beam condenser, color filter and diffuser can each be implemented using conventional optical apparatus, as known to those skilled in the art of optics. For example, the light source 606 can be a conventional incoherent light source. The display panel 607 can be a transmissive or, preferably, a reflective display panel (such as a reflective flat panel display chip) . Additionally, one or more of the beam splitting cube 608, beam condenser, color filter and diffuser can be implemented using reconfigurable HOEs. In particular, one or more of the beam splitting cube 608, beam condenser, color filter and diffuser can be implemented using methods and apparatus as described in the above-mentioned U.S. Patent Application Serial No. 09/351,412.

The light source 606, display panel 607, beam splitting cube 608, beam condenser, color filter and diffuser are combined in a movable assembly that can be moved (as shown by the bi-directional arrow in FIG. 6B) between a position

(illustrated in FIG. 6B) in which an input image is provided to the private mode projection optics 605 and a position (shown by the dashed lines in FIG. 6B) in which an input image is provided to the public mode projection optics 604. The movable assembly can be implemented using conventional apparatus, as known to those skilled in the art.

FIG. 7 is a schematic diagram of a display apparatus 700 according to another embodiment of the invention. The reconfigurable holographic mirror 701, reconfigurable holographic diffuser 702, public mode projection optics 704, private mode projection optics 705, reflective flat panel display chip 706, beam splitting cube 707 and incoherent light source 708 can all be implemented as described above for the corresponding apparatus in FIGS. 6A and 6B. However, instead of a passive diffuser 603 as in the display apparatus 600, the display apparatus 700 includes a reconfigurable holographic diffuser 703.

The public mode projection optics 704 and private mode projection optics 705 are positioned so that both the light rays 712a and 712b projected from the public mode projection optics 704 and the light rays 711a and 711b projected from the private mode projection optics 705 pass through the reconfigurable holographic diffuser 703. The reconfigurable holographic diffuser 703 can be switched between an active state in which light rays passing through the reconfigurable holographic diffuser 703 are diffracted in accordance with the optical characteristics of the reconfigurable holographic diffuser 703, and a passive state in which light rays passing through the reconfigurable holographic diffuser 703 are unaffected by the reconfigurable holographic diffuser 703. During public mode operation of the display apparatus 700, the reconfigurable holographic diffuser 703 is held in the passive state (so that the light rays 712a and 712b pass unaffected through the reconfigurable holographic diffuser 703 to the display screen 709) , while during private mode operation of the display apparatus 700, the reconfigurable holographic diffuser 703 is held in the active state (so that the light rays 711a and 711b are diffracted by the reconfigurable holographic diffuser 703 to impinge upon the display screen 709 at a desired angle that produces the desired virtual image.

When visual display apparatus according to the invention is used to produce a color display, it is necessary to provide multiple reconfigurable HOEs to produce the virtual image of private mode operation. For example, three reconfigurable HOEs can be provided, each reconfigurable HOE constructed to refract or reflect light of a particular color (e.g., red, green and blue) when in the active state. During operation of the visual display apparatus, the reconfigurable HOEs are sequentially placed in the active state, synchronously with the propagation of the corresponding color of light by other parts of the visual display apparatus, so that a full color image is produced. The construction and operation of such visual display apparatus is described in more detail in the above-mentioned U.S. Patent Application Serial No. 09/351,412.

It can be possible to construct a reflective diffuser or a reconfigurable holographic diffuser to diffuse light sufficiently well over the entire bandwidth of visible light so that a full color image is produced, thus enabling a single reconfigurable HOE (e.g., reconfigurable holographic lens or reconfigurable holographic diffuser) to be used to produce a color public mode image display. Alternatively, multiple reconfigurable HOEs - each propagating a particular color of light - can be provided to produce the public mode image display. (The use of multiple reconfigurable HOEs may be necessary to produce displays having very high image quality.) The former has the advantages of reducing the thickness of the display screen and the cost to produce the display screen, while the latter has the advantage of producing a higher quality color display.

In the embodiments described above, visual display apparatus according to the invention enables viewing of a display screen in one of two modes. However, the invention can be implemented so that viewing is enabled in more than two modes. Generally, display apparatus according to the invention can be implemented so that viewing is enabled in multiple private modes and/or multiple public modes. The provision of multiple private modes could be accomplished, for example, by adding an additional reconfigurable holographic mirror to the display screen 400 (FIGS. 4A-4C) , display screen 500 (FIGS. 5A and 5B) , display screen 600 (FIGS. 6A and 6B) or display screen 700 (FIG. 7), the additional reconfigurable holographic mirror enabling a second virtual image having a different polar diagram to be produced. The provision of multiple public modes could be accomplished, for example, by adding an additional reconfigurable holographic lens 402 to the display screen 400 (FIGS. 4A-4C) , an additional reconfigurable holographic diffuser 502 to the display screen 500 (FIGS. 5A and 5B) , an additional reconfigurable holographic diffuser 602 to the display screen 600 (FIGS. 6A and 6B) or an additional reconfigurable holographic diffuser 702 to the display screen 700 (FIG. 7) , the additional reconfigurable HOE in each case being formed to produce a different polar diagram than that produced by the existing reconfigurable HOE used to produce an image in public mode .

In general, the invention can be implemented in any desired way to specify the time and manner in which a user can switch between or among visual display modes. Selection of the mode of operation can be effected using conventional apparatus (e.g., keyboard, mouse, touchscreen) and methods (e.g., GUI techniques). The invention can be implemented so that selection of the operable display mode is effected using input apparatus to appropriately communicate with the device with which the visual display apparatus according to the invention is used. Alternatively, the invention can be implemented so that selection of the operable display mode is effected in some other manner, such as by causing transfer over a network (e.g., the Internet, an intranet) from a remote site (e.g., a server computer or computers representing a site on the World Wide Web, another computer on an intranet network) of an appropriate control instruction to the device with which the visual display apparatus according to the invention is used. The invention can be implemented so that anyone can select the operable display mode or so that only authorized individuals can select the display mode.

In the embodiments described above, during operation of a visual display apparatus according to the invention, reconfigurable HOEs are held in either a passive state or an active state to enable viewing of a display screen in one of two modes. However, as also indicated above, it is also possible to apply a voltage across the hologram of a reconfigurable HOE so that the reconfigurable HOE is in a partially active state in which light passing through the hologram is partially affected by the optical characteristics of the hologram. This may be desirable to adjust the polar diagram of a display mode to, for example, produce maximum brightness for straight ahead viewing or improve brightness over a larger viewing angle . For example , the voltage applied across a reconfigurable holographic diffuser can be varied to vary the light scattering characteristics of the diffuser. The reconfigurable HOEs of the embodiments of the invention described above can be operated in this way (i.e., the reconfigurable HOE can be placed in a partially active state) , if desired.

As illustrated in FIG. 3, in some applications of the invention, the projection system is located with respect to the display screen so that light is projected by the projection system at a relatively steep angle (e.g., in FIG. 3, an angle of about 40°-50° with respect to the surface 301a of the section 301 of the portable computer 300) relative to the display screen. In such applications, if the projection system is implemented using conventional optical apparatus, it may be necessary or desirable, as known to those skilled in the art of optics, to implement relatively complex combinations of cylindrical, prismatic and/or off- axis aspheric optical components to correct for geometric aberrations. Alternatively, such geometric aberrations could be corrected by integrating one or more reconfigurable HOEs into the projection system. In particular, methods and apparatus for integrating reconfigurable HOEs into the projection system as described in the commonly-owned, co- pending U.S. Provisional Patent Application, entitled

"Apparatus for Viewing an Image," by Milan M. Popovich et al., filed on November 12, 1998, and having attorney docket no. RETDP024, the disclosure of which is incorporated by reference herein, can be used. Visual display apparatus according to the invention can also be implemented to achieve particular display effects in one or more of the display modes. In particular, methods and apparatus for implementing such display effects as described in the above-mentioned U.S. Patent Application Serial No. 09/351,412 can be used in a visual display apparatus according to the invention. For example, a visual display apparatus according to the invention can be implemented to produce a display including multiple images (e.g., a tiled image). This can be done, for example, by sequentially propagating light through multiple reconfigurable HOEs that each direct light to a different section of the display screen. Visual display apparatus according to the invention in which multiple complete or partial images are formed at different sections of the display screen can also be implemented so that the eye or head position of a viewer is monitored, and only the content of the image (s) at which it is determined the viewer is looking are updated. Visual display apparatus according to the invention can also be implemented to display an image separately in each of multiple viewing directions, the visual display apparatus being configured to optimize the image intensity for each viewing direction. For example, an image can be sequentially propagated through multiple reconfigurable HOEs, each reconfigurable HOE being designed to produce an optimum image intensity in a particular viewing direction. Visual display apparatus according to the invention can also be implemented to vary the intensity of an image displayed to a particular eye of a viewer, thus producing a stereoscopic effect. Again, this can be done using multiple reconfigurable HOEs that are sequentially activated to produce the image at a desired intensity along a viewing angle at which a corresponding one of the viewer's eyes is anticipated to be located. Visual display apparatus according to the invention can also be implemented to provide different images to the eyes of a viewer (e.g., left and right perspective views). This can be done, for example, by controlling the projection system to sequentially generate different images and sequentially placing one or more corresponding reconfigurable HOEs in the active state in a synchronous manner, each reconfigurable HOE designed to produce the corresponding image along a viewing angle at which a corresponding one of the viewer's eyes is anticipated to be located.

Visual display apparatus according to the invention can be used in a variety of devices. For example, visual display apparatus according to the invention can be used with any of a variety of computers or computational devices. Visual display apparatus according to the invention can be particularly advantageously used with any device in which it is important to minimize the size and/or weight of visual display apparatus that is part of the device. For example, the use of visual display apparatus according to the invention in a portable computer is particularly desirable. (However, visual display apparatus according to the invention can be also be used in desktop computers.) Herein, "portable computer" refers to any computational device that can be easily carried around or worn by a user. Portable computers include, for example, notebook computers, sub-notebook computers and personal digital assistants (such as the Palm Pilot™ made by 3COM of Santa Clara, California and comparable hand-held computing devices) .

Various embodiments of the invention have been described. The descriptions are intended to be illustrative, not limitative. Thus, it will be apparent to one skilled in the art that certain modifications may be made to the invention as described herein without departing from the scope of the claims set out below.

Citas de patentes
Patente citada Fecha de presentación Fecha de publicación Solicitante Título
WO1997036206A1 *5 Mar 19972 Oct 1997Motorola Inc.Liquid crystal display device including multiple ambient light illumination modes
EP0763763A1 *6 Sep 199619 Mar 1997Motorola, Inc.Magnifying image display with multi-mode screen
JPH096289A * Título no disponible
JPH09197405A * Título no disponible
US5644369 *24 Feb 19951 Jul 1997MotorolaSwitchable lens/diffuser
US5831698 *20 Ago 19963 Nov 1998International Business Machines CorporationElectrically variable diffuser
US5877829 *14 Nov 19962 Mar 1999Sharp Kabushiki KaishaLiquid crystal display apparatus having adjustable viewing angle characteristics
Otras citas
Referencia
1 *PATENT ABSTRACTS OF JAPAN vol. 1997, no. 05 30 May 1997 (1997-05-30)
Citada por
Patente citante Fecha de presentación Fecha de publicación Solicitante Título
US7110796 *2 Oct 200219 Sep 2006Samsung Electronics Co., Ltd.Portable terminal device having a display unit utilizing a holographic screen
Clasificaciones
Clasificación internacionalG06F1/16, G02B5/32
Clasificación cooperativaG02B5/32, G06F1/1616, G06F1/1639
Clasificación europeaG06F1/16P1F, G06F1/16P9D1, G02B5/32
Eventos legales
FechaCódigoEventoDescripción
10 Feb 2000AKDesignated states
Kind code of ref document: A1
Designated state(s): AE AL AM AT AU AZ BA BB BG BR BY CA CH CN CU CZ DE DK EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MD MG MK MN MW MX NO NZ PL PT RO RU SD SE SG SI SK SL TJ TM TR TT UA UG UZ VN YU ZA ZW
10 Feb 2000ALDesignated countries for regional patents
Kind code of ref document: A1
Designated state(s): GH GM KE LS MW SD SL SZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN GW ML MR NE SN TD TG
5 Abr 2000121Ep: the epo has been informed by wipo that ep was designated in this application
27 Abr 2000DFPERequest for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
31 May 2001REGReference to national code
Ref country code: DE
Ref legal event code: 8642
9 Ene 2002122Ep: pct application non-entry in european phase