PATENT DOCUMENT

Publication Number: US-9304338-B2
Application Number: US-201313791707-A
Country: US
Kind Code: B2

Title: Methods for assembling display structures

Abstract:
Electronic devices may include displays. A display may include a display unit that includes an array of display pixels and a backlight unit that provides backlight illumination for the display pixels. An automated alignment system may be used to align the display unit to the backlight unit. The alignment system may include a camera, a control unit, and computer-controlled positioners. The control unit may gather alignment feature location information from the display unit and the backlight unit using the camera. The control unit may determine a centroid of the backlight unit based on the alignment feature location information. The alignment feature location information may include the respective locations of openings in the backlight unit. The control unit may operate computer-controlled positioners to align the display unit with respect to the backlight unit using the centroid and to subsequently attach the display unit to the backlight unit.

Claims:
What is claimed is: 
     
       1. A method for attaching a display unit of an electronic device to a backlight unit of the electronic device, wherein the display unit has an array of display pixels, the backlight unit produces backlight for the display unit and has a chassis, and the electronic device has a housing, the method comprising:
 with a control unit, gathering alignment feature location information from alignment features on the display unit and the backlight unit using a camera, wherein the alignment features comprise screw holes on the chassis that receive screws that secure the chassis to the housing; 
 with computer-controlled positioners, aligning the display unit with the backlight unit using the alignment feature location information; and 
 while the display unit is aligned with respect to the backlight unit, attaching the display unit to the backlight unit using the computer-controlled positioners. 
 
     
     
       2. The method defined in  claim 1  further comprising:
 with the control unit, determining the locations of at least one backlight datum and at least display unit datum based on the alignment feature location information. 
 
     
     
       3. The method defined in  claim 2  wherein aligning the display unit with the backlight unit comprises:
 with the computer-controlled positioners, aligning the display unit with the backlight unit by aligning the at least one backlight datum with the at least one display unit datum. 
 
     
     
       4. The method defined in  claim 3  wherein attaching the display unit to the backlight unit comprises:
 while the at least one backlight datum is aligned with the at least one display unit datum, attaching the display unit to the backlight unit. 
 
     
     
       5. The method defined in  claim 2  wherein determining the location of the at least one backlight datum comprises determining a centroid of the backlight unit. 
     
     
       6. The method defined in  claim 5  wherein gathering the alignment feature location information comprises determining respective locations of a plurality of openings in the backlight unit and wherein determining the centroid of the backlight unit comprises computing an average based on the respective locations. 
     
     
       7. The method defined in  claim 1  wherein gathering the alignment feature location information comprises:
 determining respective locations of a plurality of openings in the backlight unit. 
 
     
     
       8. The method defined in  claim 7  wherein the plurality of openings are formed in a plastic display chassis in the backlight unit. 
     
     
       9. The method defined in  claim 1  wherein gathering the alignment feature location information comprises:
 determining a location of a fiducial on the display unit. 
 
     
     
       10. The method defined in  claim 1  wherein the display unit comprises an active area configured to display images and wherein gathering the alignment feature location information comprises:
 determining a location of an edge of the active area. 
 
     
     
       11. Apparatus, comprising:
 a display unit; 
 a backlight unit, wherein the backlight unit comprises a chassis having a plurality of mounting structures that protrude laterally from the edges of the backlight unit; 
 a camera configured to capture images of the display unit and the backlight unit; and 
 a control unit coupled to the camera, the display unit, and the backlight unit, wherein the control unit is configured to align the display unit with the backlight unit based on the captured images using at least one computer-controlled positioner. 
 
     
     
       12. The apparatus defined in  claim 11  further comprising an adhesive on a surface of the backlight unit, wherein the adhesive is configured to attach the display unit to the backlight unit. 
     
     
       13. The apparatus defined in  claim 11  wherein the mounting structures of the chassis comprise a plurality of openings and wherein the control unit is configured to determine the respective locations of the plurality of openings in the chassis based on the captured images. 
     
     
       14. The apparatus defined in  claim 13  wherein each of the openings in the chassis is formed from an upper opening portion with walls that taper inwardly from an upper surface of the chassis and a lower opening portion with walls that taper inwardly from an opposing lower surface of the chassis. 
     
     
       15. The apparatus defined in  claim 13  wherein the chassis comprises an injection molded plastic chassis. 
     
     
       16. The apparatus defined in  claim 11  wherein the display unit comprises at least one fiducial and wherein the control unit is configured to determine a location of the at least one fiducial based on the captured images. 
     
     
       17. The apparatus defined in  claim 16  wherein the display unit comprises at least one glass substrate and wherein the at least one fiducial is formed on the at least one glass substrate. 
     
     
       18. The apparatus defined in  claim 11  wherein the display unit comprises an active area that includes an array of display pixels and wherein the control unit is configured to determine a location of an edge of the active area based on the captured images. 
     
     
       19. The apparatus defined in  claim 11  wherein the display unit comprises liquid crystal display pixels and wherein the backlight unit comprises a light source and a light guide plate. 
     
     
       20. A method for attaching a display unit having an array of display pixels to a backlight unit that produces backlight for the display unit, comprising:
 with a control unit, gathering alignment feature location information from the backlight unit using a camera by determining the respective locations of a plurality of openings in the backlight unit; 
 with the control unit, determining a centroid of the backlight unit from the alignment feature location information by computing an average based on the respective locations of the plurality of openings in the backlight unit; 
 with computer-controlled positioners, aligning the backlight unit to the display unit using the centroid; and 
 while the backlight unit is aligned with respect to the display unit, attaching the display unit and the backlight unit using the computer-controlled positioners. 
 
     
     
       21. The method defined in  claim 20  further comprising:
 gathering display unit alignment information from the display unit, wherein aligning the backlight unit to the display unit using the centroid comprises aligning the backlight unit to the display unit using the centroid and the display unit alignment information. 
 
     
     
       22. The method defined in  claim 21  wherein gathering the display unit alignment information comprises gathering active area location information from the display unit using the camera. 
     
     
       23. The method defined in  claim 21  wherein gathering the display unit alignment information comprises gathering alignment feature location information from the display unit using the camera.

Description:
This application claims priority to U.S. provisional patent application No. 61/721,426 filed Nov. 1, 2012, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices, and more particularly, to electronic devices with displays. 
     Electronic devices often include displays. For example, cellular telephones and portable computers often include displays for presenting information to a user. An electronic device may have a housing such as a housing formed from plastic or metal. Components for the electronic device such as display components may be mounted in the housing. 
     It can be challenging to incorporate a display into the housing of an electronic device. Size, weight, electrical grounding, robustness, ease of assembly, and light-tightness are often important considerations in designing electronic devices. If care is not taken, displays may be bulky, may exhibit undesired light reflections, or may be prone to damage during a drop event. The housing of an electronic device can be adjusted to accommodate a bulky display with large borders, but this can lead to undesirable enlargement of the size and weight of the housing and unappealing device aesthetics. 
     It would therefore be desirable to be able to provide improved ways to provide displays for electronic devices. 
     SUMMARY 
     An electronic device may be provided with a display. The display may include a display unit having an array of display pixels and a backlight unit for providing backlight illumination to the display pixels. 
     The backlight unit may include a chassis having a rectangular opening in which backlight structures are mounted. Adhesive on the upper surface of the chassis may be used in attaching the display unit to the backlight unit. 
     An automated alignment system may be used to align and attach the display unit to the backlight unit. The alignment system may include a camera, a control unit, and computer-controlled positioners. The control unit may operate the camera to gather alignment feature location information from the display unit and the backlight unit. The alignment feature location information may include the location of one or more fiducials on the display unit, the location of an active area in the display unit, and/or the location of one or more openings in the backlight unit. 
     The alignment feature location information may be used to determine alignment parameters such as one or more display unit datums and one or more backlight unit datums. 
     The backlight unit datums may include a centroid of the backlight. The centroid may be determined from the respective locations of a set of openings in the backlight unit. For example, the chassis may include an opening at each of its four corners. The locations of these openings relative to each other may be determined based on images captured from the camera in the alignment system. 
     The control unit may operate the computer-controlled positioners to align the display unit to the backlight unit using the centroid and/or using other alignment parameters. Once aligned the computer-controlled positioners may attach the display unit to the backlight unit. 
     Further features, their nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device such as a laptop computer with a display in accordance with an embodiment. 
         FIG. 2  is a perspective view of an illustrative electronic device such as a handheld electronic device with a display in accordance with an embodiment. 
         FIG. 3  is a perspective view of an illustrative electronic device such as a tablet computer with a display in accordance with an embodiment. 
         FIG. 4  is a schematic diagram of an illustrative electronic device with a display in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of illustrative display layers and backlight structures in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of illustrative display layers and backlight structures showing how display layers may be attached to a chassis with adhesive in accordance with an embodiment. 
         FIG. 7  is a perspective view of a chassis that includes metal chassis structures and plastic chassis structures in accordance with an embodiment. 
         FIG. 8  is a perspective view of an illustrative display unit having an array of display pixels and a backlight unit having openings in accordance with an embodiment. 
         FIG. 9  is a diagram of an illustrative system that may be used to align and attach a display unit to a backlight unit in accordance with an embodiment. 
         FIG. 10  is a top view of an illustrative backlight unit showing how openings in the backlight unit may be used to determine a centroid of the backlight unit in accordance with an embodiment. 
         FIG. 11  is a top view of an illustrative display unit showing how alignment features such as fiducials or active area edges on the display unit may be used to determine a backlight unit datum in accordance with an embodiment. 
         FIG. 12  is a diagram of an illustrative injection molding system that may be used to form a plastic chassis having openings in accordance with an embodiment. 
         FIG. 13  is a cross-sectional side view of a portion of a plastic chassis having openings in accordance with an embodiment. 
         FIG. 14  is a flow chart of illustrative steps involved in assembling display structures using an automated alignment system in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may include displays. The displays may be used to display images to a user. Illustrative electronic devices that may be provided with displays are shown in  FIGS. 1, 2, and 3 . 
       FIG. 1  shows how electronic device  10  may have the shape of a laptop computer having upper housing  12 A and lower housing  12 B with components such as keyboard  16  and touchpad  18 . Device  10  may have hinge structures  20  that allow upper housing  12 A to rotate in directions  22  about rotational axis  24  relative to lower housing  12 B. Display  14  may be mounted in upper housing  12 A. Upper housing  12 A, which may sometimes referred to as a display housing or lid, may be placed in a closed position by rotating upper housing  12 A towards lower housing  12 B about rotational axis  24 . 
       FIG. 2  shows how electronic device  10  may be a handheld device such as a cellular telephone, music player, gaming device, navigation unit, or other compact device. In this type of configuration for device  10 , housing  12  may have opposing front and rear surfaces. Display  14  may be mounted on a front face of housing  12 . Display  14  may, if desired, have a display cover layer or other exterior layer that includes openings for components such as button  26 . Openings may also be formed in a display cover layer or other display layer to accommodate a speaker port (see, e.g., speaker port  28  of  FIG. 2 ). 
       FIG. 3  shows how electronic device  10  may be a tablet computer. In electronic device  10  of  FIG. 3 , housing  12  may have opposing planar front and rear surfaces. Display  14  may be mounted on the front surface of housing  12 . As shown in  FIG. 3 , display  14  may have a cover layer or other external layer with an opening to accommodate button  26  (as an example). 
     The illustrative configurations for device  10  that are shown in  FIGS. 1, 2, and 3  are merely illustrative. In general, electronic device  10  may be 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, or other wearable or miniature device, a television, a computer display that does not contain 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. 
     Housing  12  of device  10 , which is sometimes referred to as a case, may be formed of materials such as plastic, glass, ceramics, carbon-fiber composites and other fiber-based composites, metal (e.g., machined or cast aluminum, stainless steel, or other metals), other materials, or a combination of these materials. Device  10  may be formed using a unibody construction in which most or all of housing  12  is formed from a single structural element (e.g., a piece of machined metal or a piece of molded plastic) or may be formed from multiple housing structures (e.g., outer housing structures that have been mounted to internal frame elements or other internal housing structures). 
     Display  14  may be a touch sensitive display that includes a touch sensor or may be insensitive to touch. Touch sensors for display  14  may be formed from an array of capacitive touch sensor electrodes, a resistive touch array, touch sensor structures based on acoustic touch, optical touch, or force-based touch technologies, or other suitable touch sensor components. 
     Displays for device  10  may, in general, include image pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electrowetting pixels, electrophoretic pixels, liquid crystal display (LCD) components, or other suitable image pixel structures. In some situations, it may be desirable to use LCD components to form display  14 , so configurations for display  14  in which display  14  is a liquid crystal display are sometimes described herein as an example. It may also be desirable to provide displays such as display  14  with backlight structures, so configurations for display  14  that include a backlight unit may sometimes be described herein as an example. Other types of display technology may be used in device  10  if desired. The use of liquid crystal display structures and backlight structures in device  10  is merely illustrative. 
     A display cover layer may cover the surface of display  14  or a display layer such as a color filter layer or other portion of a display may be used as the outermost (or nearly outermost) layer in display  14 . A display cover layer or other outer display layer may be formed from a transparent glass sheet, a clear plastic layer, or other transparent member. 
     Touch sensor components such as an array of capacitive touch sensor electrodes formed from transparent materials such as indium tin oxide may be formed on the underside of a display cover layer, may be formed on a separate display layer such as a glass or polymer touch sensor substrate, or may be integrated into other display layers (e.g., substrate layers such as a thin-film transistor layer). 
     A schematic diagram of an illustrative configuration that may be used for electronic device  10  is shown in  FIG. 4 . As shown in  FIG. 4 , electronic device  10  may include control circuitry  29 . Control circuitry  29  may include storage and processing circuitry for controlling the operation of device  10 . Control circuitry  29  may, for example, 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. Control circuitry  29  may include processing circuitry based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio codec chips, application specific integrated circuits, etc. 
     Control circuitry  29  may be used to run software on device  10 , such as operating system software and application software. Using this software, control circuitry  29  may present information to a user of electronic device  10  on display  14 . When presenting information to a user on display  14 , sensor signals and other information may be used by control circuitry  29  in making adjustments to the strength of backlight illumination that is used for display  14 . 
     Input-output circuitry  30  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 circuitry  30  may include communications circuitry  32 . Communications circuitry  32  may include wired communications circuitry for supporting communications using data ports in device  10 . Communications circuitry  32  may also include wireless communications circuits (e.g., circuitry for transmitting and receiving wireless radio-frequency signals using antennas). 
     Input-output circuitry  30  may also include input-output devices  34 . A user can control the operation of device  10  by supplying commands through input-output devices  34  and may receive status information and other output from device  10  using the output resources of input-output devices  34 . 
     Input-output devices  34  may include sensors and status indicators  36  such as an ambient light sensor, a proximity sensor, a temperature sensor, a pressure sensor, a magnetic sensor, an accelerometer, and light-emitting diodes and other components for gathering information about the environment in which device  10  is operating and providing information to a user of device  10  about the status of device  10 . 
     Audio components  38  may include speakers and tone generators for presenting sound to a user of device  10  and microphones for gathering user audio input. 
     Display  14  may be used to present images for a user such as text, video, and still images. Sensors  36  may include a touch sensor array that is formed as one of the layers in display  14 . 
     User input may be gathered using buttons and other input-output components  40  such as touch pad sensors, buttons, joysticks, click wheels, scrolling wheels, touch sensors such as sensors  36  in display  14 , key pads, keyboards, vibrators, cameras, and other input-output components. 
     A cross-sectional side view of an illustrative configuration that may be used for display  14  of device  10  (e.g., for display  14  of the devices of  FIG. 1 ,  FIG. 2 , or  FIG. 3  or other suitable electronic devices) is shown in  FIG. 5 . As shown in  FIG. 5 , display  14  may include backlight structures such as backlight unit  42  for producing backlight  44 . During operation, backlight  44  travels outwards (vertically upwards in dimension Z in the orientation of  FIG. 5 ) and passes through display pixel structures in display layers  46 . This illuminates any images that are being produced by the display 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 to 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 configuration in which display layers  46  are used in forming 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 . If desired, upper polarizer layer  54  may be attached to an outer cover layer such as cover layer  49  ( FIG. 5 ). 
     Layers  58  and  56  may be formed from transparent substrate layers such as clear layers of glass or plastic. Layers  56  and  58  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. Display layers  46  may sometimes collectively be referred to herein as a “display cell” or a “display unit.” 
     With one illustrative configuration, layer  58  may be a thin-film transistor layer that includes an array of thin-film transistors and associated electrodes (display 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. 
     During operation of display  14  in device  10 , control circuitry  29  (e.g., one or more integrated circuits such as components  68  on printed circuit  66  of  FIG. 5 ) may be used to generate information to be displayed on display  14  (e.g., display data). The information to be displayed may be conveyed from circuitry  68  to display driver integrated circuit  62  using a signal path such as a signal path formed from conductive metal traces in flexible printed circuit  64  (as an example). 
     Display driver integrated circuit  62  may be mounted on thin-film transistor layer driver ledge  82  or elsewhere in device  10 . A flexible printed circuit cable such as flexible printed circuit  64  may be used in routing signals between printed circuit  66  and thin-film transistor layer  58 . If desired, display driver integrated circuit  62  may be mounted on printed circuit  66  or flexible printed circuit  64 . 
     Printed circuit  66  may be formed from a rigid printed circuit board (e.g., a layer of fiberglass-filled epoxy) or a flexible printed circuit (e.g., a flexible sheet of polyimide or other flexible polymer layer). However, these examples are merely illustrative. If desired printed circuits  64  and  66  may be formed from a combination of rigid and flexible printed circuit layers (e.g., printed circuit  66  may be formed from a rigid printed circuit board with a layer of flexible printed circuitry that extends from an edge of printed circuit  66  to form flexible printed circuitry  64  that attaches to thin-film transistor layer  58 ). 
     Backlight structures  42  may include a backlight light guide plate such as light guide plate  78 . Light guide plate  78  may be formed from a transparent material such as clear glass or plastic. During operation of backlight structures  42 , a light source such as light source  72  may generate light  74 . Light source  72  may be, for example, an array of light-emitting diodes. 
     Light  74  from light source  72  may be coupled into edge surface  76  of light guide plate  78  and may be distributed laterally in dimensions X and Y throughout light guide plate  78  due to the principal of total internal reflection. Light guide plate  78  may include light-scattering features such as pits or bumps or other light-scattering structures. The light-scattering features may be located on an upper surface and/or on an opposing lower surface of light guide plate  78 . 
     Light  74  that scatters upwards in direction Z from light guide plate  78  may serve as backlight  44  for display  14 . Light  74  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 white plastic or other shiny materials. 
     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, compensation films for enhancing off-axis viewing, and brightness enhancement films (also sometimes referred to as turning films) for collimating backlight  44 . Optical films  70  may overlap the other structures in backlight unit  42  such as light guide plate  78  and reflector  80 . For example, if light guide plate  78  has a rectangular footprint in the X-Y plane of  FIG. 5 , optical films  70  and reflector  80  may have a matching rectangular footprint. 
     Display structures such as light guide plate  78  may be mounted in a support structure such as display chassis  90  of  FIG. 6 . Display chassis  90  may include plastic chassis structures and metal chassis structures. Display chassis  90  may serve as an interface between the structures of display  14  and surrounding portions of housing  12 . Display chassis  90  may, for example, have a rectangular shape that surrounds the peripheral edges of light guide plate  78 . 
     Display structures such as display layers  46  may be mounted on a planar portion such as portion  91  of chassis  90 . An adhesive such as adhesive  84  may be used in attaching an interior layer of display layers  46  such as display layer  58  to planar surface  91  of chassis  90 . Adhesive  84  may be liquid adhesive, light-cured adhesive, pressure-sensitive adhesive (PSA), or other suitable adhesive. If desired, adhesive  84  may be opaque adhesive such as black PSA or may be optically clear adhesive. 
     If desired, adhesive  84  may attach polarizer  60  to chassis  90 . The example of  FIG. 6  in which adhesive  84  is interposed between display layer  58  and chassis  90  is merely illustrative. 
     A perspective view of an illustrative display chassis such as chassis  90  is shown in  FIG. 7 . As shown in  FIG. 7 , chassis  90  may have a rectangular opening such as rectangular opening  99 . Rectangular display structures may be mounted within rectangular opening  99 . Examples of rectangular display structures that may be mounted within or above opening  99  include backlight structures  42  (e.g., a rectangular light guide plate, a rectangular reflector, and rectangular optical films such as diffuser layers and brightness enhancing films). If desired, additional display structures may be mounted within chassis  90  or attached to chassis  90  such as rectangular polarizers, a rectangular thin-film transistor layer, and a rectangular color filter layer. 
     Display chassis  90  may include plastic structures such as plastic structures  90 P (sometimes referred to as a plastic chassis or p-chassis) and metal structures such as metal structures  90 M (sometimes referred to as an m-chassis or metal chassis. Display chassis  90  may have a rectangular shape with four edges. Plastic structures  90 P may form three of the four edges while metal chassis  90 M forms one of the four edges (as an example). Light source  72  (e.g., an array of light-emitting diodes) may be mounted within metal structures  90 M (e.g., along the metal edge of chassis  90 M). If desired, chassis  90  may have different configurations (e.g., a configuration in which light-emitting diodes  72  are formed within metal chassis structures  90 M along two opposing edges of a rectangular chassis while plastic chassis structures  90 P form the remaining two edges of the rectangular chassis). 
     An example of a plastic material that may be used in forming plastic structures  90 P is glass-filled nylon (e.g., nylon with impregnated glass fibers). Other types of materials such as other polymers, materials with other strengthening fibers, or combinations of two or more of these materials may be used in forming plastic structures  90 P, if desired. 
     Examples of metal materials that may be used in forming metal structures  90 M are aluminum, stainless steel, copper, and copper alloys (as examples). Metal generally has a significantly higher thermal conductivity than plastic, so forming structures  52  from metal may be helpful in conducting heat away from light source  72  during operation of light source  72  to provide backlight for display  14 . 
     Backlight structures may be assembled within chassis  90  to form backlight unit  42 . In one suitable embodiment, backlight unit  42  and display unit  46  may be assembled separately and may be subsequently attached together using adhesive  84 . For example, as shown in  FIG. 8 , display unit  46  may be aligned with backlight unit  42  by aligning the peripheral edges of display unit  46  with the peripheral edges of backlight unit  46 . Once aligned, backlight unit  42  and display unit  46  may be pressed together and adhesive  84  may adhere backlight unit  42  to display unit  46 . 
     As electronic devices are manufactured with increasingly small dimensions, the process of aligning a backlight unit to a display unit may become more difficult. For example, as the border of inactive display area around the active area of a display shrinks, the tolerance for misalignment may also be reduced. Conventional display alignment methods such as aligning the display unit with the backlight unit by hand often yield unsatisfactory results. For example, displays that have been aligned by hand often result in asymmetric inactive borders around the active area of the display. This type of variability is undesirable and can be aesthetically unappealing to a user. 
     To accommodate the narrow width W at the inactive border of a display, a computer-controlled alignment system may be used to precisely align a display unit such as display unit  46  to a backlight unit such as backlight unit  42 . The computer-controlled alignment system may include an optics system for inspecting display unit  42  and backlight unit  42  and for locating alignment features on display unit  42  and/or on backlight unit  42 . Alignment features that may be identified may include holes, edges, notches, fiducials, posts, drilled holes, inserts, structures having known shapes, corners, machined structures, laser engraved structures, cutouts, or other structures or surface features that may be recognized by an imaging system. 
     As shown in  FIG. 8 , backlight unit  42  may have mounting structures such as mounting structures  92  that protrude laterally from the edges of backlight unit  42 . Mounting structures  92  may, for example, be formed from protruding portions of plastic chassis  90 P ( FIG. 7 ) that surrounds the light guide plate  78 . Each mounting structure  92  may have an opening such as screw hole  94 . During assembly of device  10 , screws may pass through openings  94  and may screw into threaded portions of housing  12  (as an example), thereby securing display chassis  90  and display units  46  and  42  to housing  12  within device  10 . 
     Openings  94  may, for example, be used as alignment features for aligning display unit  46  and backlight unit  42 . For example, a camera in the alignment system may capture images of alignment features such as openings  94  and may determine the locations of openings  94  relative to each other. Based on this information, the alignment system may determine the location of additional datums such as the centroid of backlight unit  42 . 
     The alignment system&#39;s camera may also identify and locate alignment features on display unit  46 . Any suitable feature that may be recognized by a camera may be used as an alignment feature. For example, an edge such as edge  96  of active area AA of display unit  46  may be recognized by a camera and may be used as an alignment feature. The active area of display unit  46  may include an array of display pixels such as display pixels  33 . Display pixels  33  may be formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electrowetting pixels, electrophoretic pixels, liquid crystal display (LCD) components, or other suitable image pixel structures 
     As another example, one or more fiducials such as fiducials  98  may be formed on the surface of a display layer in display unit  46 . Fiducials  98  may be implemented by forming one or more metal alignment marks on the surface of layer  56  (as an example). 
     Alignment features such as fiducials  98  and/or edge  96  of active area AA may be used by the camera-based alignment system in determining the location of additional datums of display unit  46 . For example, the locations of the alignment features may be used to identify the point on active area AA of display unit  46  that should align with the centroid of backlight unit  46 . 
     Once the backlight datums and the corresponding display unit datums have been determined, the alignment system may attach display unit  46  to backlight unit  42  while aligning the backlight datums with the corresponding display unit datums. 
       FIG. 9  is a diagram of an illustrative computer-controlled alignment system that may be used to align and attach display unit  46  to backlight unit  42 . As shown in  FIG. 9 , computer-controlled alignment system  100  may include machine vision equipment such as camera  154  for capturing images of display unit  46  and backlight unit  42 . Camera  154  may include a digital image sensor that captures digital image data for processing by control unit  152 . Camera  154  may have sufficient resolution for capturing images of edges (e.g., edges of substrates, edges such as edge  96  of active display area on display unit  46 , etc.), images of openings (e.g., openings  94  in chassis  90  of backlight unit  42 ), image of fiducials (e.g., fiducials  98  on the surface of a glass substrate in display unit  46 ), and images of other structures and features. 
     If desired, a light source may be used to generate polarized and/or unpolarized backlight for illuminating display unit  46  and/or backlight unit  42 . The use of a light source to illuminate display unit  46  may help delineate the location of fiducials  98  and/or edge  96  of the active display area in display unit  46 . 
     Data from camera  154  may be analyzed by control unit  152  to determine the locations of alignment features on display unit  46  and backlight unit  42 . Control unit  152  may include one or more computers, embedded processors, networked computing equipment, online computing equipment, and/or other computing equipment for processing digital image data from camera  154  or other sensors to determine the location of alignment features on display unit  46  and backlight unit  42  and for issuing corresponding control signals on outputs  170 ,  172 ,  174 ,  176 , and  178 . 
     The control signals on outputs  170 ,  172 ,  174 ,  176 , and  178  may control the operation of computer-controlled positioners  160 ,  162 ,  164 ,  166 , and  168 , respectively. For example, control signals on paths  170  and  172  may control the operation of positioners  160  and  162 , respectively, which are used in adjusting the position of backlight unit  42 . Control signals on paths  174  and  176  may control the operation of positioners  164  and  166 , respectively, which are used in adjusting the position of display unit  46 . Control signals on path  178  may control positioner  168 , which may be used in adjusting the position of camera  154 . 
     Computer-controlled positioners  160 ,  162 ,  164 , and  166  may adjust the positions of backlight unit  42  and display unit  46  using handling structures such as handling structures  102 . Handling structures  102  may be clamps, spatulas, pneumatic structures, finger-like members, or other structures that may be used to handle and manipulate display unit  46  and backlight unit  42 . Computer-controlled positioners  160 ,  162 ,  164 ,  166 , and  168  may be configured to move and/or rotate backlight unit  42 , display unit  46 , and camera  154  in any suitable direction. 
     If desired, different arrangements of positioners may be used. For example, display unit  46  and backlight unit  42  may each be controlled by a single positioner. As another example, display unit  46  or backlight unit  42  may be stationary. The example of  FIG. 9  is merely illustrative. 
     Camera  154  may be used to gather information such as alignment feature location information from display unit  46  and backlight unit  42 . The alignment feature location information may be analyzed by control unit  152  to obtain corresponding alignment parameters. The alignment parameters may include, for example, a display unit datum and a backlight datum. Once the alignment parameters have been determined, control unit  152  may issue corresponding control signals to positioners  160 ,  162 ,  164 , and  166  to maneuver backlight unit  42  and display unit  46  into alignment based on the alignment parameters. This may include, for example, aligning the display unit datum with the backlight datum. Once aligned, control unit  152  may issue control signals to positioners  160 ,  162 ,  164 , and  166  to move display unit  46  and backlight unit  42  towards each other until adhesive  84  on the surface of backlight unit  42  is in contact with display unit  46  (i.e., until backlight unit  42  and display unit  46  are attached to each other). 
     Although  FIG. 9  illustrates an arrangement in which display unit  46  is interposed between backlight unit  42  and camera  154 , it should be understood that the locations of camera  154 , display unit  46 , and backlight unit  42  may be changed depending on the images that camera  154  is capturing. For example, the locations of camera  154 , display unit  46 , and backlight unit  42  may be manipulated such that backlight unit  42  is interposed between display unit  46  and camera  154 . The arrangement of  FIG. 9  is merely illustrative. 
     If desired, the imaging system that includes camera  154  and control unit  152  may be separate from the computer-controlled positioning equipment that aligns and attaches display unit  46  and backlight unit  42 . With this type of configuration, camera  154  may be used to gather alignment feature location information from display unit  46  and backlight unit  42  in a first stage. The alignment feature location information may be analyzed by computing equipment to obtain corresponding alignment parameters. The alignment parameters may be fed to a separate computer-controlled positioning system such as a system that includes a control unit and a plurality of computer-controlled positioners that may be used to maneuver display unit  46  and backlight unit  42 . The control unit may instruct the computer-controlled positioners to align and attach display unit  46  and backlight unit  42  based on the previously determined alignment parameters. The example of  FIG. 9  in which system  100  includes an optics system for gathering alignment information from display unit  46  and backlight unit  42  and a computer-controlled positioning system for aligning and attaching display unit  46  and backlight unit  42  is merely illustrative. 
       FIG. 10  is a diagram of backlight unit  42  illustrating how the locations of alignment features may be used to determine a backlight datum. As shown in  FIG. 10 , backlight unit  42  may include mounting structures  92 . Each of the four corners of backlight unit  42  may have an associated mounting structure  92 . For example, a first corner may have an associated mounting structure  92 , labeled “TAB C1,” a second corner may have an associated mounting structure  92 , labeled “TAB C2,” a third corner may have an associated mounting structure  92 , labeled “TAB F1,” and a fourth corner may have an associated mounting structure  92 , labeled “TAB F2.” 
     Each mounting structure  92  may have an associated opening such as opening  94 . The locations of openings  94  may be used to determine a backlight datum associated with backlight unit  42 . For example, control unit  152  of  FIG. 9  may determine the centroid of backlight unit  42  based on the locations of openings  94 . 
     The following illustrative procedure may be performed in order to obtain a backlight datum such as the centroid of backlight unit  42 . First, control unit  152  may operate camera  154  to determine the locations of openings  94  relative to each other. For example, the center of opening  94  in TAB C1 may be defined as the origin (indicated as datum “C” in  FIG. 10 ) with (x,y) coordinates of (0,0); the center of opening  94  in TAB C2 may be defined with respect to the origin as having (x,y) coordinates of s(xc2,0); the center of opening  94  in TAB F1 may be defined with respect to the origin as having (x,y) coordinates of (xf1,yf1); and the center of opening  94  in TAB F2 may be defined with respect to the origin as having (x,y) coordinates of (xf2, yf2). 
     With these predetermined parameters, the x-axis may be defined by a line between opening  94  of TAB C1 and opening  94  of TAB C2. This line may be defined as datum “B,” as indicated in  FIG. 10 . The y-axis may be defined as the line that passes through (0,0) at TAB C1 perpendicular to the x-axis defined by datum B. 
     Control unit  152  may then determine the centroid of backlight unit  42  based on the (x,y) coordinates of each opening  94 . The centroid, indicated as datum “D” in  FIG. 10 , may have coordinates (xd,yd). The x-coordinate may be the numerical average (arithmetic mean) of the x-coordinates of each of the four openings  94 , and the y-coordinate of the centroid may be the numerical average (arithmetic mean) of the y-coordinates of each of the four openings  94 . In other words, the coordinates (xd,yd) of centroid D may be calculated using the following equations: 
     
       
         
           
             xd 
             = 
             
               
                 0 
                 + 
                 
                   xc 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   2 
                 
                 + 
                 
                   xf 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
                 + 
                 
                   xf 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   2 
                 
               
               4 
             
           
         
       
       
         
           
             yd 
             = 
             
               
                 0 
                 + 
                 0 
                 + 
                 
                   yf 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
                 + 
                 
                   yf 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   2 
                 
               
               4 
             
           
         
       
     
     If desired, control unit  152  may use the alignment feature location information to verify that the dimensions of backlight unit  42  are acceptable (e.g., to verify whether the dimensions of backlight unit  42  fall within predetermined ranges of acceptable dimensions). If the dimensions of backlight unit  42  fall outside of the predetermined ranges, one or more structures in backlight unit  42  may be reworked, may be discarded, may be used for other purposes, or may be reanalyzed. If the dimensions of backlight unit  42  fall within the predetermined ranges, backlight unit  42  may proceed to subsequent processing operations. 
       FIG. 11  is a diagram of display unit  46  illustrating how the locations of alignment features may be used to determine a display unit datum. As shown in  FIG. 11 , display unit  46  may include alignment features such as fiducials  98 . If desired, edge  96  of the active portion of display unit  46  may be used as an alignment feature (e.g., in addition to or instead of fiducials  98 ). The use of fiducials  98  as alignment features is merely illustrative and is sometimes described herein as an example. However, it should be understood that similar alignment operations may be performed using active area border  96  as an alignment feature. 
     Control unit  152  may operate camera  154  to determine the locations of fiducials  98  relative to each other. As shown in  FIG. 11 , the line between the two fiducials  98  may be defined as datum “E.” 
     Control unit  152  may then determine the location of datum “P1” based on the locations of fiducials  98 . Datum P1 may be a point on the active area of display unit  46  with which the backlight datum D should be aligned. In other words, datum P1 may be a point on display unit  46  that nominally corresponds to the centroid of backlight unit  42 . The location of datum P1 may depend on the on the configurations (e.g., the dimensions) of display unit  46  and backlight unit  42 . Control unit  152  may determine the location of datum P1 relative to fiducials  98 . 
     Upon determining alignment parameters such as display unit datums P1 and E ( FIG. 11 ) and backlight datums D and B ( FIG. 10 ), control unit  152  may actuate positioners  160 ,  162 ,  164 , and  166  ( FIG. 9 ) to maneuver backlight unit  42  and display unit  46  into alignment based on the alignment parameters. For example, control unit  152  may issue control signals to the positioners to align display unit  46  and backlight unit  42  such that point P1 on display unit  46  is within a predetermined range of centroid D on backlight unit  42  (e.g., within 35 microns of point D, within 55 microns of point D, within 75 microns of point D, etc.). Control unit  152  may also issue control signals to the positioners to align display unit  46  and backlight unit  42  such that the angle between line E associated with display unit  46  and line B associated with backlight unit  42  is within a predetermined range (e.g., between 0° and ±0.1°, between 0° and ±0.3°, between 0° and ±0.5°, etc.). 
     When control unit  152  determines that the distance between point P1 of display unit  46  and point D of backlight unit  42  is within the predetermined range of distances and that the angle between line E of display unit  46  and line B of backlight unit  42  is within the predetermined range of angles, control unit  152  may issue control signals to positioners  160 ,  162 ,  164 , and  166  to move display unit  46  and backlight unit  42  into contact with each other and to thereby attach display unit  46  to backlight unit  42 . 
     The accuracy of automated alignment system  100  may depend on the accuracy of camera  154  in determining the locations of openings  94  in chassis  90 . Care must be taken to ensure that the precision involved in determining the locations of openings  94  is maximized. 
     Mounting structures  92  in which openings  94  are located may be molded (e.g., injection molded) as integral portions of plastic chassis  90 P. The accuracy of camera  154  in locating openings  94  may depend on the shape of opening  94  and on the quality of the mold. Conventional injection molding tools often result in molding defects such as flash (sometimes referred to as burrs). This type of molding defect would increase the margin of error involved in determining the location of openings  94  with camera  154 . Additionally, conventional molding arrangements typically mold openings having shapes that are not conducive to machine vision imaging. 
     An illustrative injection molding system that may be used to mold a chassis  90 P with mounting structures  92  having openings  94  that are suitable for imaging and inspection is shown in  FIG. 12 . As shown in  FIG. 12 , injection molding system  200  may include a mold such as mold  202 . Mold  202  may include a mold cavity  202 C. Mold cavity  202 C may have the negative shape of mounting structure  92  such that, when filled with plastic, the resulting part has the shape of mounting structure  92  having opening  94 . 
     As shown in  FIG. 12 , a shot of pelletized thermoplastic material (e.g., thermoplastic granules or “resin”) may be added to a hopper such as hopper  282 . The material may be gravity fed into a screw-type plunger such as plunger  284 . The heat generated by heating unit  286  and the rotation of the screw in plunger  284  may result in elevated temperatures and a shearing action on the thermoplastic pellets that causes the pellets to melt into molten plastic. Screw rotation in plunger  284  may push the molten plastic towards nozzle  288  and into mold cavity  202 C. 
     When mold  202  has been completely filled, the molten plastic may be cooled. The plastic that solidifies within cavity  202 C may form mounting structure  92  having opening  94 . When the plastic has solidified, mold  202  may be removed (e.g., mold  202  may be opened by separating upper portion  202 U from lower portion  202 L along line  244 ). 
     To form opening  94  in mounting structure  92 , mold  202  may have pins such as pins  240  and  242  that prevent a middle portion of mounting structure  92  from being filled with plastic during the injection molding process. 
     The use of an upper pin and a lower pin may minimize molding defects such as flash. For example, the clamping force of pin  240  against pin  242  may be sufficient to prevent molten plastic from seeping into interface  246  between upper mold  202 U and lower mold  202 L. 
     Additionally, the use of an upper and a lower pin having different diameters at interface  246  may create an opening having a shape that lends itself to more accurate imaging. For example, as shown in  FIG. 13 , opening  94  may have an upper opening portion with walls that taper inwardly from upper surface  254  of structure  92  and a lower opening portion with walls that taper inwardly from opposing lower surface  256  of structure  92 . 
     Opening  94  in structure  92  may have ledges such as ledges  150  as a result of the difference in diameters of pins  240  and  242  at interface  246 . Due to ledges  150  and the sloped side walls of opening  94 , camera  154  may pick up edge  250  or  252  when inspecting opening  94 . The difference in location of edge  250  and edge  252  is proportional to the difference between width W1 of opening  94  at edge  252  and width W2 of opening  94  at edge  250 . 
     In conventionally formed openings in molded parts, ledges  250  would not be present and the sloped side walls of opening  94  would extend smoothly from surface  256  to surface  254 . The difference in locations of the edges that may be picked up by a camera would then be greater than that of the configuration shown in  FIG. 13 . The presence of ledges  150  may therefore allow for a more accurate inspection of opening  94  by camera  154 . 
     A flow chart of illustrative steps involved in assembling electronic devices and displays by aligning a display unit with a backlight unit using an automated alignment system is shown in  FIG. 14 . 
     At step  300 , control unit  152  may gather alignment feature location information from backlight unit  42 . This may include operating camera  154  to inspect backlight unit  42  and to identify and determine the location of backlight alignment features. For example, control unit  152  may use camera  154  to determine the locations of openings  94  in chassis  90  relative to each other. 
     At step  302 , control unit  152  may determine one or more backlight datums based on the alignment feature location information. This may include, for example, calculating the centroid of backlight unit  42  based on the locations of openings  94 . 
     At step  304 , control unit  152  may gather alignment featured location information from display unit  46 . This may include operating camera  154  to inspect display unit  46  and to identify and determine the location of display unit alignment features. For example, control unit  152  may use camera  154  to determine the locations of one or more fiducials  98  on the surface of a display layer such as a color filter substrate or to determine the location of edge  96  of the active display area in display unit  46 . 
     At step  306 , control unit  152  may determine one or more display unit datums based on the alignment feature location information. This may include, for example, determining the location of a point on the active display area that nominally corresponds to the centroid of the backlight unit. The location of the display unit datum may be defined relative to the display unit alignment features. 
     If desired, steps  300  and  304  may both be performed prior to steps  302  and  306  (e.g., alignment feature location information may be gathered from both display unit  46  and backlight unit  42  in a first stage and subsequently analyzed in a second stage to determine backlight and display unit datums). 
     At step  308 , control unit  152  may issue commands to computer-controlled positioners (e.g., positioners  160 ,  162 ,  164 , and  166  of  FIG. 9 ) to align the backlight datums with the display unit datums. This may include, for example, positioning display unit  46  and backlight unit  42  such that the offset between a display unit datum and a backlight datum is within a predetermined range. When display unit  46  and backlight unit  42  have been satisfactorily aligned, control unit  152  may instruct the computer-controlled positioners to bring display unit  46  and backlight unit  42  into contact with each other (while maintaining alignment) to thereby attach display unit  46  to backlight unit  42 . 
     At step  308 , other display structures may be assembled to form display  14  and display  14  may be installed in device housing  12  of electronic device  10  with other device components. 
     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: 20130308
Publication Date: 20160405
Grant Date: 20160405
Priority Date: 20121101
Inventors: FRANKLIN JEREMY C.
RAPPOPORT BENJAMIN M.
AI JIANG
QIAN AMY
BERG BRUCE E.
DIXON EVA J.
PIPLANI ATEET
Assignee: APPLE INC
CPC Classifications: [{"code": "Y10T29/49117", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2001/133354", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/1303", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F2001/133322", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/49117", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133354", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133322", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/49117", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133322", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/1303", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133354", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/1303", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 50546740