PATENT DOCUMENT

Publication Number: US-10705358-B2
Application Number: US-201615199620-A
Country: US
Kind Code: B2

Title: Display apparatus with adjustable angles-of-view comprising backlight structures having an electrically adjustable lens array that adjusts backlight illumination

Abstract:
A display may have a backlight unit that provides backlight illumination. The backlight unit may include a light guide that distributes light throughout the display and an electrically adjustable lens array. The lens array may have lenses such as liquid lenses or liquid crystal lenses. By adjusting the lenses in the lens array, the angles of rays of backlight from the backlight unit may be adjusted to adjust the angle-of-view of the display. The angle-of-view of the display may also be adjusted using an electrically controllable filter layer. The electrically controllable filter layer may have a liquid crystal layer or a polymer dispersed liquid crystal layer that can be controlled using electrodes. When the electrodes apply signals to the electrically controllable filter layer, portions of the filter layer change to a dark or translucent state and restrict the angle-of-view of the display.

Claims:
What is claimed is: 
     
       1. Apparatus, comprising:
 display layers for a display that include an array of pixels with an angle of view for displaying images, wherein the angle of view has a width with respect to a surface normal of the display; and 
 backlight structures for the display that provide backlight illumination that passes through the display layers, wherein the backlight structures include an electrically adjustable lens array that adjusts the backlight illumination and thereby adjusts the width of the angle of view for the display, wherein the electrically adjustable lens array includes liquid lenses each of which has immiscible first and second liquid layers, wherein the electrically adjustable lens array comprises transparent electrodes that apply signals to the liquid lenses, and wherein the liquid lenses are configured to change between a concave shape and a convex shape based on the signals applied by the transparent electrodes. 
 
     
     
       2. The apparatus defined in  claim 1  further comprising control circuitry that operates the backlight structures in:
 a first mode in which the liquid lenses of the lens array have a first configuration in which the backlight illumination provides the display with a first angle of view with respect to a surface normal of the display; and 
 a second mode in which the liquid lenses of the lens array have a second configuration in which the backlight illumination provides the display with a second angle of view that is different than the first angle of view. 
 
     
     
       3. The apparatus defined in  claim 2  wherein the display layers include a liquid crystal layer. 
     
     
       4. The apparatus defined in  claim 1  wherein the electrically adjustable lens array comprises transparent electrodes that apply signals to the liquid lenses. 
     
     
       5. The apparatus defined in  claim 4  wherein the transparent electrodes are patterned to form individually addressable regions each including a different respective set of the liquid lenses. 
     
     
       6. Apparatus, comprising:
 display layers for a display that include an array of pixels with an angle of view for displaying images, wherein the display layers include:
 first, second, and third polarizers; 
 a first liquid crystal layer between the first and second polarizers that forms the array of pixels; and 
 a second liquid crystal layer between the second and third polarizers; 
 
 backlight structures for the display that provide backlight illumination that passes through the display layers, wherein the backlight structures include an electrically adjustable lens array that adjusts the backlight illumination; and 
 electrode fingers that apply electric fields to the second liquid crystal layer and thereby adjust the angle of view for the display, wherein each of the electrode fingers completely extends across at least two pixels of the array of pixels. 
 
     
     
       7. Apparatus, comprising:
 display layers for a display that include an array of pixels for displaying images, wherein the display layers include:
 first and second polarizers; 
 a liquid crystal layer between the first and second polarizers that forms the array of pixels; and 
 a polymer dispersed liquid crystal layer; 
 
 backlight structures for the display that provide backlight illumination that passes through the display layers, wherein the backlight structures include an electrically adjustable lens array that adjusts the backlight illumination and thereby adjusts an angle of view for a first region of the display to be different from an angle of view for a second region of the display; and 
 electrode fingers that apply electric fields to the polymer dispersed liquid crystal layer, wherein the electrode fingers extend across at least two pixels of the array of pixels. 
 
     
     
       8. The apparatus defined in  claim 7  wherein the electrically adjustable lens array includes electrically adjustable liquid crystal lenses each of which includes liquid crystal material and lens electrodes. 
     
     
       9. The apparatus defined in  claim 8  wherein the lens electrodes apply signals to the liquid crystal lenses to adjust the liquid crystal material. 
     
     
       10. The apparatus defined in  claim 9  wherein the lens electrodes are patterned to form individually addressable regions each having a different respective set of the liquid crystal lenses. 
     
     
       11. The apparatus defined in  claim 7  wherein the electrode fingers extend across at least a quarter of the display. 
     
     
       12. The apparatus defined in  claim 11  wherein the electrode fingers extend across at least half of the display. 
     
     
       13. The apparatus defined in  claim 12  wherein the electrode fingers extend across the entire display. 
     
     
       14. The apparatus defined in  claim 1  wherein the electrically adjustable lens array includes first and second electrodes, wherein the first electrode contacts the first liquid layer, and wherein the second electrode contacts the second liquid layer. 
     
     
       15. The apparatus defined in  claim 14  wherein the first and second electrodes are formed from transparent conductive material. 
     
     
       16. The apparatus defined in  claim 2  wherein the first mode collimates the backlight illumination and wherein the second mode spreads out the backlight illumination. 
     
     
       17. The apparatus defined in  claim 6  wherein the electrically adjustable lens array includes electrically adjustable liquid crystal lenses each of which includes liquid crystal material. 
     
     
       18. The apparatus defined in  claim 17  wherein the electrode fingers apply signals to the second liquid crystal layer so that portions of the second liquid crystal layer become dark and adjust a width of the angle of view with respect to a surface normal of the display. 
     
     
       19. The apparatus defined in  claim 18  wherein the electrode fingers are patterned to form individually addressable regions each having a different respective set of the liquid crystal lenses. 
     
     
       20. The apparatus defined in  claim 6  wherein the electrode fingers extend across the entire display.

Description:
This application claims the benefit of provisional patent application No. 62/290,081 filed on Feb. 2, 2016, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to electronic devices and, more particularly, to electronic devices with displays. 
     BACKGROUND 
     Electronic devices often include displays. For example, laptop computers have displays. Displays are typically designed to display images over a relatively wide angle of view to accommodate movements in the position of a viewer relative to the display. In some situations, such as when a user of a laptop or other device with a display is using the device in public, the wide viewing angle is undesirable as it compromises privacy. 
     SUMMARY 
     A display may have a backlight unit that provides backlight illumination. The display may have display layers that form an array of pixels. The backlight unit may supply the backlight unit to the display layers. 
     The display layers may include substrate layers, a layer of liquid crystal material sandwiched between the substrate layers, and upper and lower polarizer layers. The substrate layers may include a color filter layer and a thin-film transistor layer and may be interposed between the upper and lower polarizers. 
     The backlight unit may include a light guide layer that distributes light from a light source and may include an electrically adjustable lens array through which backlight illumination passes that has scattered out of the light guide layer. 
     The lens array may have lenses such as liquid lenses or liquid crystal lenses. By adjusting the lenses in the lens array, the angles of rays of backlight illumination from the backlight unit may be adjusted to adjust the angle-of-view of the display. 
     The angle-of-view of the display may also be adjusted using an electrically controllable filter layer. The electrically controllable filter layer may have a liquid crystal layer or a polymer dispersed liquid crystal layer that can be controlled using electrodes. When the electrodes apply signals to the electrically controllable filter layer, portions of the filter layer change to a dark or translucent state and restrict the angle-of-view of the display. The electrically controllable lens array of the backlight structures can be used in conjunction with the electrically controllable filter layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device having a display in accordance with an embodiment. 
         FIG. 2  is a schematic diagram of an illustrative electronic device having a display in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of an illustrative display in accordance with an embodiment. 
         FIG. 4  is a cross-sectional side view of an illustrative display being used in a wide viewing angle mode in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of an illustrative display of the type shown in  FIG. 4  being used in a reduced-viewing-angle mode in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of an illustrative display having a liquid crystal angle-of-view adjustment structure for placing the display in a wide angle or reduced-viewing-angle viewing mode in accordance with an embodiment. 
         FIG. 7  is a cross-sectional side view of a portion of the liquid crystal viewing angle restriction device of  FIG. 6  in accordance with an embodiment. 
         FIGS. 8 and 9  are top views of illustrative electrode patterns that may be used for the liquid crystal viewing angle restriction device of  FIGS. 6 and 7  in accordance with an embodiment. 
         FIG. 10  is a cross-sectional side view of an illustrative backlight having an array of adjustable optical elements such as an array of liquid lenses for adjusting backlight illumination properties in accordance with an embodiment. 
         FIGS. 11, 12, 13, and 14  show how an array of adjustable optical elements may be used in adjusting backlight structures to produce diffuse or collimated backlight illumination in accordance with embodiments. 
         FIG. 15  is a top view of an adjustable liquid crystal lens having concentric electrodes for forming an adjustable lens in accordance with an embodiment. 
         FIG. 16  is a cross-sectional side view of the illustrative adjustable optical element of  FIG. 15  and an associated graph in which liquid crystal layer index-of-refraction values have been plotted as a function of distance across the element in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device of the type that may be provided with a display is shown in  FIG. 1 . Electronic device  10  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a computer display that does not contain an embedded computer, a computer display that includes an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. In the illustrative configuration of  FIG. 1 , device  10  is a portable device such as a laptop computer. Other configurations may be used for device  10  if desired. The example of  FIG. 1  is merely illustrative. 
     As shown in  FIG. 1 , device  10  includes a display such as display  14  mounted in housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     Housings  12 A and  12 B may be connected to each other using hinge structures located along the upper edge of lower housing  12 B and the lower edge of upper housing  12 A. Hinges may allow upper housing  12 A to rotate about axis  22  in directions  24  relative to lower housing  12 B. 
     Display  14  may be mounted in upper housing  12 A. Display  14  may be a touch screen display that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a display that is not touch-sensitive. Capacitive touch screen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures. A touch sensor may be formed using electrodes or other structures on a display layer that contains a pixel array or on a separate touch panel layer that is attached to the pixel array (e.g., using adhesive). 
     Display  14  may include an array of pixels formed from liquid crystal display (LCD) components, an array of electrophoretic pixels, an array of electrowetting pixels, an array of organic light-emitting diode pixels, or pixels based on other display technologies. Configurations in which display  14  is a liquid crystal display with a backlight are sometimes described herein as an example. This use of liquid crystal display technology for forming display  14  is merely illustrative. Display  14  may, in general, be formed using any suitable type of pixels (e.g., display  14  may be an organic light-emitting diode display). 
     As shown in  FIG. 1 , device  10  may have input-output devices such as track pad  18  and keyboard  16 . Device  10  may also have components such as cameras, microphones, speakers, buttons, status indicator lights, buzzers, sensors, and other input-output devices. These devices may be used to gather input for device  10  and may be used to supply a user of device  10  with output. Connector ports in device  10  may receive mating connectors (e.g., an audio plug, a connector associated with a data cable such as a Universal Serial Bus cable, a data cable that handles video and audio data such as a cable that connects device  10  to a computer display, television, or other monitor, etc.). 
       FIG. 2  is a schematic diagram of device  10 . As shown in  FIG. 2 , electronic device  10  may have control circuitry  26 . Control circuitry  26  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  26  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. 
     Input-output circuitry in device  10  such as input-output devices  28  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  28  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors (e.g., ambient light sensors, proximity sensors, orientation sensors, magnetic sensors, force sensors, touch sensors, etc.), light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  28  and may receive status information and other output from device  10  using the output resources of input-output devices  28 . Input-output devices  18  may include one or more displays such as display  14 . 
     Control circuitry  26  may be used to run software on device  10  such as operating system code and applications. During operation of device  10 , the software running on control circuitry  26  may display images on display  14  using an array of pixels in display  14 . While displaying images, control circuitry  26  may control the transmission of each of the pixels in the array and can make adjustments to the amount of backlight illumination for the array that is being produced by backlight structures in display  14 . 
     Control circuitry  26  may direct display  14  to operate in different operating modes. For example, control circuitry  26  can direct display  14  to operate in a normal operating mode when privacy is not a concern. In the normal operating mode, the images on display  14  may be visible to people seated next to the user of device  10  due to the relatively wide angle of view of display  14  in normal operation. In situations in which privacy is a concern, a user may supply input to control circuitry  26  to place display  14  in a privacy mode in which the angle of view of display  14  is restricted. In response, control circuitry  26  may make adjustments to display  14  (e.g., backlight adjustments and/or adjustments to angle-of-view restriction structures elsewhere in display  14 ) that reduce the angle of view of display  14 . When the angle of view of display  14  is lowered, it will become difficult or impossible for viewers that are located at off-axis positions relative to display  14  to view images on display  14  (e.g., a viewer seated next to the user on an airplane will not be able to view images on display  14 ). At the same time, the user of device  10  who is seated in an on-axis position will be able to use display  14  to view images. 
     Changes in the operating mode of display  14  to implement angle-of-view restrictions (i.e., adjustments to display  14  to place display  14  in normal viewing mode or a reduced-angle-of-view privacy mode) may be made based on user input or may be made automatically by control circuitry  26 . Control circuitry  26  may, for example, use information such as content sensitivity information to determine whether or not content that is being display on display  14  should be displayed in normal mode or privacy mode. If, for example, a user is viewing a movie, the movie may be displayed in normal mode. In the event that a private message such as an incoming text message is detected, display  14  may be placed in privacy mode, thereby ensuring that the content of the text message will not be inadvertently revealed to unauthorized parties. If desired, only a part of display  14  may be placed in privacy mode (e.g., to ensure the privacy of a text message) while the remainder of display  14  is operated normally (e.g. to display a movie). 
     A cross-sectional side view of display  14  is shown in  FIG. 3 . Display  14  may have a rectangular shape (i.e., display  14  may have a rectangular footprint and a rectangular peripheral edge that runs around the rectangular footprint) or may have other suitable shapes. Display  14  may be planar, as shown in  FIG. 3 , or may have a curved profile. 
     As shown in  FIG. 3 , display  14  may include backlight structures such as backlight unit  42  for producing backlight illumination such as backlight  44 . During operation, backlight  44  travels outwards (vertically upwards in dimension Z in the orientation of  FIG. 3 ) and passes through an array of pixels in display layers  46 . This illuminates any images that are being produced by the pixels for viewing by a user. For example, backlight  44  may illuminate images on display layers  46  that are being viewed by viewer  48  in direction  50 . 
     Display layers  46  may be mounted in chassis structures such as a plastic chassis structure and/or a metal chassis structure to form a display module for mounting in housing  12  or display layers  46  may be mounted directly in housing  12  (e.g., by stacking display layers  46  into a recessed portion in housing  12 ). Display layers  46  may form a liquid crystal display or may be used in forming displays of other types. 
     In a liquid crystal display, display layers  46  may include a liquid crystal layer such a liquid crystal layer  52 . Liquid crystal layer  52  may be sandwiched between display layers such as display layers  58  and  56 . Layers  56  and  58  may be interposed between lower polarizer layer  60  and upper polarizer layer  54 . 
     Layers  58  and  56  may be formed from transparent substrate layers such as clear layers of glass or plastic. Layers  58  and  56  may be layers such as a thin-film transistor layer and/or a color filter layer. Conductive traces, color filter elements, transistors, and other circuits and structures may be formed on the substrates of layers  58  and  56  (e.g., to form a thin-film transistor layer and/or a color filter layer). Touch sensor electrodes may also be incorporated into layers such as layers  58  and  56  and/or touch sensor electrodes may be formed on other substrates. 
     With one illustrative configuration, layer  58  may be a thin-film transistor layer that includes an array of pixel circuits based on thin-film transistors and associated electrodes (pixel electrodes) for applying electric fields to liquid crystal layer  52  and thereby displaying images on display  14 . Layer  56  may be a color filter layer that includes an array of color filter elements for providing display  14  with the ability to display color images. If desired, layer  58  may be a color filter layer and layer  56  may be a thin-film transistor layer. Configurations in which color filter elements are combined with thin-film transistor structures on a common substrate layer in the upper or lower portion of display  14  may also be used. 
     During operation of display  14  in device  10 , control circuitry (e.g., one or more integrated circuits on a printed circuit) may be used to generate information to be displayed on display  14  (e.g., display data). The information to be displayed may be conveyed to one or more display driver integrated circuits such as illustrative circuit  62 A or illustrative circuit  62 B using a signal path such as a signal path formed from conductive metal traces in a rigid or flexible printed circuit such as printed circuit  64  (as an example). 
     Backlight structures  42  may include a light guide layer such as light guide layer  78  (sometimes referred to as a light guide structure or light guide). Light guide layer  78  may be formed from one or more stacked layers of transparent material such as clear glass or plastic (e.g., molded plastic that forms a light guide plate, a thin flexible plastic film, etc.). During operation of backlight structures  42 , light sources such as light source  72  may generate light that creates backlight  44 . Light source  72  may be an array of light-emitting diodes that runs along one or more edges of light guide layer  78  such as edge  76  of light guide layer  78  (i.e., into the page along the X axis in the orientation of  FIG. 3 ). Light-source  72  may emit light  74  into edge  76  of light guide layer  78 . 
     Light  74  may be distributed throughout light guide layer  78  due to the principal of total internal reflection. Scattering features (protrusions, recesses, etc.) may be incorporated into light guide layer  78  (e.g., on the upper and/or lower surface of layer  78 ) to scatter light from layer  78 . Light that is scattered upwards in direction Z from light guide layer  78  may serve as backlight  44  for display  14 . Light that scatters downwards may be reflected back in the upwards direction by reflector  80 . Reflector  80  may be formed from a reflective material such as a layer of plastic covered with a dielectric mirror thin-film coating. To enhance backlight performance for backlight structures  42 , backlight structures  42  may include optical films  70 . Optical films  70  may include diffuser layers for helping to homogenize backlight  44  and thereby reduce hotspots and light collimating films such as prism films (sometimes referred to as brightness enhancement films) and turning films for directing backlight  44  towards direction Z. Optical films  70  may overlap the other structures in backlight unit  42  such as light guide layer  78  and reflector  80 . For example, if light guide layer  78  has a rectangular footprint in the X-Y plane of  FIG. 3 , optical films  70  and reflector  80  may have a matching rectangular footprint. If desired, films such as compensation films may be incorporated into other layers of display  14  (e.g., a reflective polarizer layer). 
     Layers  46  and/or backlight  42  may be provided with structures that allow display  14  to be operated in multiple viewing modes such as a normal angle-of-view mode and a reduced angle-of-view mode. When operated in the normal angle-of-view mode, viewer  48  can view images on display  14  over a relatively wide range of angles (see, e.g., display  14  of  FIG. 4 , which is displaying images over wide angle of view A). When privacy is desired, display  14  can be operated in the reduced angle-of-view mode. In this mode, viewer  48  can view images on display  14  over a more restricted range of angles (see, e.g., display  14  of  FIG. 5 , which is displaying images over reduced angle of view B, where B&lt;A). 
       FIG. 6  is a cross-sectional side view of display  14  showing illustrative angle-of-view adjustment structures that may be incorporated into display layers  46  to implement multiple viewing modes. In the example of  FIG. 6 , angle-of-view adjustment layers  90  have been incorporated into display  14  on top of upper polarizer  54 . Illustrative display  14  of  FIG. 6  is a liquid crystal display (i.e., the layers of display  14  under layers  90  form a liquid crystal display), but, in general, display  14  may be any suitable type of display (e.g., one or more layers of display  14  under layers  90  may form an electrophoretic display, an organic light-emitting diode display, or other display). Layers  90  serve as a liquid crystal filter that can be placed in a normal mode to allow display  14  to display images with a normal angle of view or that can be placed in an angle-of-view limiting mode in which portions of layers  90  are darkened or translucent so that display  14  displays images with a restricted angle of view. 
     As shown in  FIG. 6 , layers  90  may include lower substrate  92 , lower electrode structures such as lower electrode  94 , liquid crystal filter layer  96 , upper electrode structures such as upper electrode(s)  100 , upper substrate  98 , and polarizer  102 . Electrodes  94  and  100  may be formed from transparent conductive structures such as layers of indium tin oxide or metal that is sufficiently thin to be transparent to light. Electrode  94  may be a blanket conductive film and electrode  100  may be patterned, electrode  94  may be patterned and electrode  100  may be a blanket conductive film, or both electrodes  94  and  100  may be patterned. Configurations in which lower electrode  94  is a blanket film that covers display  14  and in which upper electrode  100  is patterned may sometimes be described herein as an example. 
     The patterned electrode of layers  90  (i.e., electrode  100  in the example of  FIG. 6 ) may have elongated finger (e.g., elongated strips of electrode material that extend into the page in the orientation of  FIG. 6 ), may have a grid shape, or may have other suitable shapes. Arrangements in which electrode  100  has multiple elongated parallel strips (fingers) that run along one of the dimensions of display  14  (e.g., vertically parallel to the left and right edges of display  14  of  FIG. 1 ) may sometimes be described herein as an example. 
     Substrates  92  and  98  may be formed from transparent planar structures such as layers of clear glass, ceramic, sapphire or other transparent crystalline materials, clear plastic, etc. Electrode  94  may be deposited on the surface of substrate  92  that faces filter layer  96 . Electrodes  100  may be formed on the surface of substrate  98  that faces filter layer  96 . 
     Filter layer  96  may be formed from any suitable structure that can be electrically modulated by application of electric fields through electrodes  94  and  100  to exhibit changes in light transmittance through layers  90 . As an example, filter layer  96  may be a layer of material that includes liquid crystals. 
     With one suitable arrangement, filter layer  96  is a liquid crystal layer (e.g., a liquid that is retained between layers  98  and  100 ). In this type of configuration, column spacers may be interposed between substrate layers  98  and  92  to help maintain a desired spacing between layers  98  and  92  (i.e., a desired thickness for the liquid crystal layer) and to prevent layers  98  and  92  from directly contacting each other. 
     The operation of layer  90  in this type of arrangement is shown in  FIG. 7 . Due to the presence of polarizer layer  54 , light that is exiting display  14  will be linearly polarized. Electrodes  100  can selectively apply electric fields to underlying portions  103  of layer  96 , without applying electric fields to non-overlapped portions  104  of layer  96 . Polarizer  102  is present on the top of layers  90  and works in conjunction with polarizer  54 . When no electric field is applied to portions  103 , portions  103  and portions  104  will not rotate the polarization of light travelling upwards through layer  96  and layers  90  will be transparent to light at all normal angles relative to surface normal n of display  14 . This allows light  44  to exit display  14  over angle-of-view A ( FIG. 4 ). When an electric field is applied to portions  103 , portions  103  will rotate the polarization of light that is traveling upwards through layer  96  so that this light is selectively blocked by polarizer  102  (i.e., portions  103  will become opaque). Portions  104  will remain transparent. In this configuration, darkened regions  103  will serve as electrically controlled microlouvers that restrict the angle-of-view of exiting display light. Display  14  will therefore emit images over reduced angle-of-view B ( FIG. 5 ). 
     With another suitable arrangement, filter layer  96  is a polymer dispersed liquid crystal layer. In a polymer dispersed liquid crystal, pockets of liquid crystal material are dispersed within voids in a cured polymer matrix. The polymer dispersed liquid crystal material of layer  96  can then be placed in either a low-haze transparent state or a high-haze translucent state by applying signals with electrodes  94  and  100 . 
     The polymer matrix of the polymer dispersed liquid crystal layer has an index of refraction. When no electric field is applied to the liquid crystal regions with the electrodes, the liquid crystals are randomly aligned and scatter light due to index of refraction differences between the liquid crystal regions and the polymer matrix. In this situation, regions  103  of layer  96  will be translucent and will scatter light associated with larger angles with respect to surface normal n of display  14 . The application of no electric field to regions  102  therefore causes regions  102  to act as light diffusing louvers that scatter off-axis light and thereby reduce the angle of view of display  14  (i.e., display  14  is placed in privacy mode, as shown by reduced angle-of-view B in  FIG. 5 ). When electrodes  94  and  100  apply an electric field to regions  103 , the liquid crystal material within the voids of the polymer in regions  103  will align, thereby causing the index of refraction of the liquid crystal pockets to match that of the surrounding polymer. In this situation, regions  103  will be transparent (i.e., regions  103  will be clear and will exhibit low haze). The angle of view of display  14  is accordingly large and display  14  can operate in a normal mode (see, e.g., display  14  will exhibit normal angle of view A of  FIG. 4 ). 
     When filter layer  96  is formed from polymer dispersed liquid crystal, polarizer  102  can be omitted. 
     If desired, layer  96  may be formed from guest-host liquid crystal material (i.e., angle-of-view adjustment layers  90  may be based on a guest-host liquid crystal modulator). Polarizer  102  can be omitted when layers  90  form a guest-host liquid crystal device. 
     In a guest-host liquid crystal device, guest-host liquid crystal layer  96  may be interposed between substrate layers  92  and  98 . During operation, control signals may be applied to electrodes  94  and  100  from control circuitry  26 . The control signals may control the transmission of the portions of layers  90  that are overlapped by electrodes  100  (i.e., portions  103  of  FIG. 7 ). For example, the transmission of portions  103  of layer  96  may be adjusted from a high level when an applied alternating current voltage or other applied voltage from electrodes  100  and  94  across layer  96  is small to a low level when the applied voltage across these portions of layer  96  is high. 
     Liquid crystal layer  96  may include liquid crystal molecules (liquid crystals), which may be referred to as host molecules, and dye molecules, which may be referred to as guest molecules. The guest molecules may be rotated when the liquid crystal molecules are rotated by applied electric fields. Any suitable guest-host system may be used for liquid crystal layer  96  of layers  90 . With one suitable arrangement, which may sometimes be described herein as an example, layers  90  may contain a vertical alignment layer (e.g., a polyimide rubbing layer) on the surfaces of layers  90  that are adjacent to layer  96  to orient liquid crystal molecules in layer  96  vertically in the absence of applied electric field to electrodes  100  and  94 . The dye molecules in layer  96  may be associated with a dichroic dye having a concentration of about 1-2%, more than 0.5%, or less than 4%. When the applied voltage to layer  96  is low (e.g., 0 volts), all of layer  96  may be transparent and the angle of view of display  14  may be high. When the applied voltage to layer  96  between electrodes  100  and electrode  94  is high, regions  103  will become opaque and layers  90  will restrict the angle of view of display  14 . If desired, configurations in which the alignment layers are used to align the molecules of layer  96  in different orientations may also be used (e.g., to create a guest-host system in which regions  103  are transparent at high voltages and opaque at low voltages). 
     Some or all of display  14  may be covered with angle-of-view adjustment structures and the angle-of-view adjustment structures may all be controlled together or may have individually controlled portions. With one illustrative configuration, the entire surface of display  14  may be covered with an angle-of-view adjustment layer using an electrode pattern of the type shown by illustrative electrode pattern  100  of  FIG. 8 . With this arrangement, all of the fingers  100 F in electrode  100  may be controlled together using a single applied voltage V. If desired, different portions of display  14  may be covered with individually controlled sets of fingers  100 F. As shown in  FIG. 9 , for example, display  14  may be provided with angle-of-view adjustment structures that include first electrode  100 - 1 , which is controlled by voltage V 1 , second electrode  100 - 2  that is controlled by voltage V 2 , third electrode  100 - 3  that is controlled by voltage V 3 , and fourth electrode  100 - 4  that is controlled by voltage V 4 . Any suitable level of granularity may be used in forming electrode structures for angle-of-view adjustment structures  90 . For example, display  14  may be divided into 2-20, more than 2, more than 4, more than 10, or less than 100 individually controllable regions each of which can have a normal or restricted angle-of-view depending on the control signals supplied to the electrodes in those regions by control circuitry  26 . The use of four individually controlled sets of electrode fingers  100 F in the example of  FIG. 9  is merely illustrative. 
     Using an arrangement of the type shown in  FIG. 9 , selected regions of display  14  can be placed in privacy mode (e.g., to hide text messages, sensitive documents, or other sensitive content in those regions) at the same time that the remainder of display  14  is being operated in normal angle-of-view mode. 
     If desired, backlight structures  42  may be used to place display  14  in different angle-of-view modes. For example, backlight structures  42  may be used in conjunction with layers  90  or may be used separately to place all or selected parts of display  14  in a normal angle-of-view mode or a restricted angle-of-view mode. Backlight structures  42  may have an array of electrically adjustable lenses that allow selected portions of display  14  to be placed in different angle-of-view modes using backlight structures  42  or that may be adjusted in unison when the angle of view of all of display  14  is being adjusted. 
     The lenses of backlight structures  42  may be controlled differently in different regions (e.g., left and right halves, quadrants, etc.). As described in connection with the electrode segmenting scheme of  FIG. 9 , this allows control circuitry  26  to selectively place particular region(s) of display  14  in a restricted angle-of-view mode while other portions of display  14  present a viewer with content having a normal angle-of-view. Configurations for backlight structures  42  in which all of the adjustable lenses are adjusted in tandem may also be used. 
     An illustrative adjustable backlight unit is shown in  FIG. 10 . As shown in  FIG. 10 , backlight structures  42  may include a light guide layer such as light guide layer  78 . Light guide layer  78  may receive light  74  from light sources such as light source  72  of  FIG. 3 . Light scattering features  110  such as protrusions and/or recesses in the upper and/or lower surfaces of light guide layer  78  may help scatter backlight upwards through the layers of adjustable lens array  134 . Reflector  80  may help to recycle light that is scattered downwards. 
     The illustrative lens array of  FIG. 10  contains an array of liquid lenses  118 . Liquid lenses  118  may be formed from multiple layers of liquid materials such as liquid layer  122  and liquid layer  120 . Layers  120  and  122  may be laterally separated by support structures  116  (e.g., a patterned polymer layer with openings for respective lenses  118 ). Support structures  116  and the liquid layers of lenses  118  may be sandwiched between upper substrate layer  132  and lower substrate layer  112 . Layers  112  and  132  may be formed from transparent glass, clear plastic, or other transparent substrate material. 
     Lens array  134  may have electrodes such as transparent electrodes  114  and  130  on substrates  112  and  132 . Electrodes  114  and  130  may be formed from transparent conductive material such as indium tin oxide, metal that is sufficiently thin to be transparent, or other conductive transparent material. Electrode  114  may be a blanket conductive film and electrode  130  may be patterned to address individual lenses  118  or groups of lenses  118 , electrode  130  may be a blanket film and electrode  114  may be patterned to form individually controllable electrode structures for corresponding lenses  118  or groups of lenses  118 , or both electrodes  114  and  130  may be patterned to address lenses individually or in groups. As shown by dashed lines  130 ′, all of lenses  118  may, if desired, be addressed at the same time (i.e., lower electrode  114  may be a blanket film that covers display  14  and upper electrode  30  may be a blanket film that covers display  14 ). 
     Using the electrodes of lens array  134 , the optical properties of liquid lenses  118  may be adjusted for all of backlight unit  42  or for one or more selected portions of backlight unit  42 . The layers of lenses  118  (i.e., layers  120  and  122 ) are immiscible. For example, layer  122  may be water and layer  120  may be oil. In the absence of applied electrical signals with electrodes  130  and  114 , layers  120  and  122  may be separated by a planar interface such as planar interface  124 . When it is desired to change the optical properties of lenses  118 , electric fields may be applied, thereby forming convex lenses or concave lenses, as illustrated by illustrative curved interfaces  126  and  128  of  FIG. 10 . By changing the curvature of the interface between layers  120  and  122  and thereby adjusting the focal lengths of lenses  118 , backlight  114  from light guide layer  78  may be collimated (to create a privacy mode) or spread out (to support normal angle-of-view operation). 
     The way in which lenses  118  are adjusted may depend on the configuration of light guide layer  78  and the desired operating mode of display  14 . 
     In the examples of  FIGS. 11 and 12 , light scattering features  110  on light guide layer  78  have been configured to produce diffuse backlight illumination  44 . In the configuration of  FIG. 11 , lenses  118  of lens array  134  have been configured to allow the diffuse backlight to spread out through display  14  with a normal angle-of-view A (e.g., by placing lenses  118  in a state in which the interface between layers  120  and  122  is flat as shown by interface  124  of  FIG. 1 ). In the configuration of  FIG. 11 , lenses  118  of lens array  134  have been configured to collimate light  44  so that display  14  has a restricted angle-of-view B (e.g., by placing lenses  118  in a state in which the interface between layers  120  and  122  produces convex lenses or other lenses that collimate backlight  44 ). 
     In the examples of  FIGS. 13 and 14 , light scattering features  110  on light guide layer  78  have been configured to supply lens array  134  with collimated light. In the configuration of  FIG. 13 , lenses  118  of lens array  134  have been configured to diffuse and thereby spread out the collimated light to form diffuse backlight illumination  44  (e.g., lenses  118  may be placed in a defocusing state in which lenses  118  are configured as concave lenses). This allows display  14  to exhibit a normal angle-of-view A. In the configuration of  FIG. 14 , lenses  118  of lens array  134  have been configured with planar interfaces (see planar interface  124 ) or other interface shapes that allow the collimated light from light guide layer  78  to exit display  44  as backlight illumination  44  with narrow angle-of-view B. 
     If desired, electrically controllable lenses may be formed by using electrodes such as ring-shaped electrodes  136  of  FIG. 15  to form circular lenses (or by using electrodes with other shapes to form cylindrical lenses or other suitable lenses). Electrodes  136  may apply signals that electrically modify the index of refraction of underlying liquid crystal material. In the example of  FIG. 15 , each set of ring-shaped electrodes forms a respective electrically adjustable lens  118  in lens array  134 . By varying the voltages on electrodes  136  (e.g., voltages Va, Vb, and Vc in the illustrative three-ring configuration of  FIG. 15 ), the optical properties of each lens  118  may be adjusted. Lenses  118  may be adjusted in tandem for part or all of backlight unit  42 . 
     As shown in the cross-sectional side view of lens array  134  of  FIG. 116 , each lens  118  may be formed from a layer of liquid crystal material  142  that is sandwiched between upper and lower transparent substrate layers such as substrates  138  and  144 . Lower electrode  140  may be formed on substrate  138 . Upper electrode(s)  136  may be formed on substrate  144 . Liquid crystal layer  142  may be interposed between layers  138  and  144 . Other configurations may be used for the electrodes of lens array  134  if desired. The configuration of  FIGS. 15 and 16  is merely illustrative. 
     Light guide layer  78  may supply lens array  134  of  FIG. 16  with backlight that passes through lens array  134  and the other layers of display  14 . During operation of device  10 , the voltages applied to the electrodes of lenses  118  may be adjusted by control circuitry  26  to locally change the index-of-refraction of liquid crystal layer  142  under each of the electrodes. This adjusts the optical properties of lens  118  and adjusts the angles of light rays  44  exiting backlight structures  42 . 
     In the graph of the illustrative arrangement of  FIG. 16 , the index of refraction n for liquid crystal layer  142  has been plotted as a function of distance X across lens  118  for two different electrode voltage scenarios. In the first scenario, voltages Va, Vb, and Vc are all zero, so the index n is constant across lens  118 , as shown by dashed line  150 . In this situation, layer lens  118  effectively has an infinite focal length (i.e., lens  118  does not focus light). In the second scenario, voltage Va, Vb, and Vc have increasing magnitudes, so n varies as show by line  152 . In this situation, lens  118  has a convex shape and focuses light passing through lens array  134 . Lens array  134  of  FIGS. 15 and 16  can therefore be operated in a first mode in which light passes through array  134  without being significantly changed (see, e.g., light  44  of  FIG. 11 , which provides display  14  with normal angle-of-view A) and in a second mode in which light that passes through array  134  is collimated to reduce the angle of view of display  14  (see, e.g., light  44  of  FIG. 12 , which is focused to restricted angle-of-view B due to the focusing properties of lens array  134 ). Other arrangements for backlight  42  (e.g., configurations in which electrically controllable liquid crystal lens structures form concave lenses, configurations in which lens array  134  has an array of cylindrical lenses rather than a two-dimensional array of circular lenses, configurations in which lens array  134  has electrically controllable lenses formed using other electrically adjustable optical structures, etc.) may also be used. 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20160630
Publication Date: 20200707
Grant Date: 20200707
Priority Date: 20160202
Inventors: CHRISTOPHY, MIGUEL C.
XU, MING
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F1/133626", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133626", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/294", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/50", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1334", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/1323", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/1334", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/1336", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1323", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/29", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1336", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1323", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/1334", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1336", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2001/294", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/29", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2001/133626", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 59386588