Methods of manufacturing fiber optic plates for electronic devices

An electronic device may have a housing with a display. A protective display cover layer for the display may have an image transport layer such as a fiber optic plate. The fiber optic plate may be formed from a bundle of fibers. The fibers may be formed using fiber extruding equipment. Each fiber may have a core covered with a cladding, a stray light absorbing layer, and binder material. The fibers may be deformed in a heated chamber by pressing inwardly with a die that has a recess, causing the fibers to bulge into the recess. A cutter can be used to cut off a layer of the deformed fibers. This layer may be machined and polished to form the fiber optic plate.

FIELD

This relates generally to electronic devices, and, more particularly, to display cover layers for electronic devices.

BACKGROUND

Electronic devices may have displays. Displays have arrays of pixels for displaying images for a user. To prevent damage to the pixels, the pixels can be covered with a transparent display cover layer. If care is not taken, however, the inclusion of a display cover layer into an electronic device may cause the device to have larger inactive border regions than desired or may introduce undesired image distortion.

SUMMARY

An electronic device may have a housing. A display may be mounted in the housing. A protective display cover layer may be formed over the display. During operation, images on the display may be viewed through the protective display cover layer.

The protective display cover layer may have an image transport layer such as a fiber optic plate. The fiber optic plate may guide and expand image light from the display and thereby expand the effective size of images on the display. The expanded image size helps cover peripheral housing structures and minimizes the size of display borders.

The fiber optic plate may be formed from a bundle of fibers. The fibers may be formed using an extruder. Each fiber may have a core covered with a cladding, a stray light absorbing layer, and binder material. A loose bundle of the fibers may be processed in a heated chamber.

The fibers may be deformed in the heated chamber by pressing inwardly with a die that has a recess. This causes the fibers to bulge into the recess. The binder holds the fibers together. A cutter can be used to cut off a layer of the deformed fibers. This layer may be machined into a desired shape such as a shape with rounded edge profiles. A polishing tool may polish the fibers to form a fiber optic plate for the protective display cover layer. The protective display cover layer, a display, and other components may be assembled into a housing to form an electronic device.

DETAILED DESCRIPTION

An electronic device may have a display. The display may have an array of pixels for creating an image. The image may pass through a protective display cover layer that overlaps the array of pixels. To minimize display borders, the display cover layer may include an image transport layer formed from a coherent fiber bundle or Anderson localization material. The image transport layer helps expand the effective size of the image without imparting undesired distortion to the image. In an illustrative configuration, which may sometimes be described herein as an example, a display cover layer for the display in an electronic device is formed from a fiber optic plate that contains a deformed coherent fiber bundle.

A cross-sectional side view of a portion of an illustrative electronic device with a display cover layer that includes a fiber optic plate is shown inFIG. 1. In the example ofFIG. 1, device10is a portable device such as a cellular telephone, wristwatch, or tablet computer. Other types of devices may have display cover layers with fiber optic plates, if desired.

Device10includes a housing such as housing12. Housing12may be formed from polymer, metal, glass, crystalline material such as sapphire, ceramic, fabric, fibers, fiber composite material, natural materials such as wood and cotton, other materials, and/or combinations of such materials. Housing12may be configured to form housing walls. The housing walls may enclose one or more interior regions such as interior region24and may separate interior region24from exterior region22.

Electrical components18may be mounted in interior region24. Electrical components18may include integrated circuits, discrete components, light-emitting components, sensors, and/or other circuits and may, if desired, be interconnected using signal paths in one or more printed circuits such as printed circuit20. If desired, one or more portions of the housing walls may be transparent (e.g., so that light associated with an image on a display or other light-emitting or light-detecting component can pass between interior region24and exterior region22).

Electrical components18may include control circuitry. The control circuitry may include storage and processing circuitry for supporting the operation of device10. 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 the control circuitry may be used to control the operation of device10. For example, the processing circuitry may use sensors and other input-output circuitry to gather input and to provide output and/or to transmit signals to external equipment. 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. The control circuitry may include wired and/or wireless communications circuitry (e.g., antennas and associated radio-frequency transceiver circuitry such as cellular telephone communications circuitry, wireless local area network communications circuitry, etc.). The communications circuitry of the control circuitry may allow device10to communicate with other electronic devices. For example, the control circuitry (e.g., communications circuitry in the control circuitry) may be used to allow wired and/or wireless control commands and other communications to be conveyed between devices such as cellular telephones, tablet computers, laptop computers, desktop computers, head-mounted devices, handheld controllers, wristwatch devices, other wearable devices, keyboards, computer mice, remote controls, speakers, accessory displays, accessory cameras, and/or other electronic devices. Wireless communications circuitry may, for example, wirelessly transmit control signals and other information to external equipment in response to receiving user input or other input from sensors or other devices in components18.

Input-output circuitry in components18of device10may be used to allow data to be supplied to device10and to allow data to be provided from device10to external devices. The input-output circuitry may include input devices that gather user input and other input and may include output devices that supply visual output, audible output, or other output.

Output may be provided using light-emitting diodes (e.g., crystalline semiconductor light-emitting diodes for status indicators and/or displays, organic light-emitting diodes in displays and other components), lasers, and other light-emitting devices, audio output devices (e.g., tone generators and/or speakers), haptic output devices (e.g., vibrators, electromagnetic actuators, piezoelectric actuators, and/or other equipment that supplies a user with haptic output), and other output devices.

The input-output circuitry of device10(e.g., the input-output circuitry of components18) may include sensors. Sensors for device10may include force sensors (e.g., strain gauges, capacitive force sensors, resistive force sensors, etc.), audio sensors such as microphones, touch and/or proximity sensors such as capacitive sensors (e.g., a two-dimensional capacitive touch sensor integrated into a display, a two-dimensional capacitive touch sensor and/or a two-dimensional force sensor overlapping a display, and/or a touch sensor or force sensor that forms a button, trackpad, or other input device not associated with a display), and other sensors. Touch sensors for a display or for other touch components may be based on an array of capacitive touch sensor electrodes, acoustic touch sensor structures, resistive touch components, force-based touch sensor structures, a light-based touch sensor, or other suitable touch sensor arrangements. If desired, a display may have a force sensor for gathering force input (e.g., a two-dimensional force sensor may be used in gathering force input on a display).

If desired, the sensors may include optical sensors such as optical sensors that emit and detect light, ultrasonic sensors, optical touch sensors, optical proximity sensors, and/or other touch sensors and/or proximity sensors, monochromatic and color ambient light sensors, image sensors, fingerprint sensors, temperature sensors, sensors for measuring three-dimensional non-contact gestures (“air gestures”), pressure sensors, sensors for detecting position, orientation, and/or motion (e.g., accelerometers, magnetic sensors such as compass sensors, gyroscopes, and/or inertial measurement units that contain some or all of these sensors), health sensors, radio-frequency sensors (e.g., sensors that gather position information, three-dimensional radio-frequency images, and/or other information using radar principals or other radio-frequency sensing), depth sensors (e.g., structured light sensors and/or depth sensors based on stereo imaging devices), optical sensors such as self-mixing sensors and light detection and ranging (lidar) sensors that gather time-of-flight measurements, humidity sensors, moisture sensors, gaze tracking sensors, three-dimensional sensors (e.g., time-of-flight image sensors, pairs of two-dimensional image sensors that gather three-dimensional images using binocular vision, three-dimensional structured light sensors that emit an array of infrared light beams or other structured light using arrays of lasers or other light emitters and associated optical components and that capture images of the spots created as the beams illuminate target objects, and/or other three-dimensional image sensors), facial recognition sensors based on three-dimensional image sensors, and/or other sensors.

In some configurations, components18may include mechanical devices for gathering input (e.g., buttons, joysticks, scrolling wheels, key pads with movable keys, keyboards with movable keys, and other devices for gathering user input). During operation, device10may use sensors and/or other input-output devices in components18to gather user input (e.g., buttons may be used to gather button press input, touch and/or force sensors overlapping displays can be used for gathering user touch screen input and/or force input, touch pads and/or force sensors may be used in gathering touch and/or force input, microphones may be used for gathering audio input, etc.). The control circuitry of device10can then take action based on this gathered information (e.g., by transmitting the information over a wired or wireless path to external equipment, by supplying a user with output using a haptic output device, visual output device, an audio component, or other input-output device in housing12, etc.).

If desired, electronic device10may include a battery or other energy storage device, connector ports for supporting wired communications with ancillary equipment and for receiving wired power, and other circuitry. In some configurations, device10may serve as an accessory and/or may include a wired and/or wireless accessory (e.g., a keyboard, computer mouse, remote control, trackpad, etc.).

Device10may include one or more displays. The displays may, for example, include an organic light-emitting diode display, a liquid crystal display, a display having an array of pixels formed from respective light-emitting diodes (e.g., a pixel array having pixels with crystalline light-emitting diodes formed from respective light-emitting diode dies such as micro-light-emitting diode dies), and/or other displays. The displays may include rigid display structures and/or may be flexible displays. For example, a light-emitting diode display may be sufficiently flexible to be bent. Displays for device10may have pixel arrays for displaying images for a user. Each pixel array (which may sometimes be referred to as a display panel, display substrate, or display) may be mounted under a transparent display cover layer that helps to protect the pixel array. In the example ofFIG. 1, pixel array (display)14is mounted under an image transport layer such as fiber optic plate16, which serves as a protective display cover layer (and which may sometimes be referred to as forming a transparent portion of the housing for device10). Additional protective layers (e.g., transparent layers of glass, crystalline material such as sapphire, etc.) may be stacked above and/or below fiber optic plate16. The configuration ofFIG. 1in which the display cover layer for device10is formed from fiber optic plate16is illustrative.

During operation, the pixels of display14produce image light that passes through optical fibers16F in fiber optic plate16for viewing by a user such as viewer28who is viewing device10in direction26. The fibers or other optical structures of image transport layer structures such as fiber optic plate16(which may sometimes be referred to as a coherent fiber bundle) transport light (e.g., image light and/or other light) from one surface (e.g., the surface of plate16facing display14) to another (e.g., the surface of plate16facing viewer28) while preserving the integrity of the image light or other light. This allows an image produced by an array of pixels in a flat or curved display to be transferred from an input surface of a first shape at a first location to an output surface with a curved cross-sectional profile, compound curvature, or other desired second shape at a second location. The fiber optic plate may therefore move the location of an image and may optionally change the shape of the surface on which the image is presented.

Device10may have four peripheral edges and a rectangular footprint when viewed in direction26or may have other suitable shapes. To help minimize the size of inactive display borders as a user is viewing front face F of device10as shown inFIG. 1, the shapes of fibers16F along the rectangular periphery of plate16may be deformed outwardly as shown inFIG. 1. The deformed shapes of fibers16F help distribute image light laterally outwards in the X-Y plane so that the effective size of display14is enlarged and the image produced by display14covers some or all of the sidewalls of housing12when the image on front face F is being viewed by viewer28. For example, the bent shapes of fibers16F may help shift portion of the displayed image laterally outward in the X-Y plane along the edges and corners of device10to block the sidewall portions of housing12from view. In some arrangements, the portions of fibers16F at the outermost surface of layer16are oriented parallel or nearly parallel with viewing direction26and the Z axis ofFIG. 1, which helps ensure that some or all of the light that has passed through plate16will travel in the Z direction and be viewable by viewer28.

Fibers16F for fiber optic plate16may have any suitable configuration. A cross-sectional view of fiber optic plate16in an illustrative arrangement in which fibers16F have multiple layers of material is shown inFIG. 2. As shown inFIG. 2, fibers16F may each have a core such as core16F-1. Cores16F-1and the other structures of fiber optic plate16may be formed from transparent materials such as polymer, glass, crystalline material such as sapphire, and/or other transparent materials. In an illustrative configuration, which may sometimes be described herein as an example, fiber optical plate16includes polymer fibers.

Fiber cores16F-1may be formed from polymer of a first refractive index and may be surrounded by cladding16F-2(e.g., polymer) of a second, lower refractive index. This arrangement allows fibers16F to guide light in accordance with the principal of total internal reflection. In some configurations, a stray light absorbing layer such as layer16F-3may be applied as a coating on cladding16F-2to help absorb stray light. Core16F-1and cladding16F-2may be formed from clear polymers. Stray light absorbing layer16F-3may contain black pigment or other light absorbing material that renders layers16F-3opaque (e.g., layer16F-3may be formed from a material that absorbs and blocks light). Binder material16FB (e.g., clear polymer) may hold fibers16F together to form plate16. The fractional cross-sectional areas occupied by core16F-1, cladding16F-2, stray light absorbing layer16F-3, and binder16FB may respectively be 65%-85%, 2-10%, 1-5%, and 5-15%, and/or other suitable values.

The diameter of core16F-1may be 5-15 microns or other suitable size (e.g., at least 3 microns, at least 7 microns, 10 microns, at least 15 microns, less than 20 microns, less than 14 microns, etc.). The thickness of cladding16F-2may be 0.5 microns, at least 0.1 microns, at least 0.4 microns, less than 2 microns, less than 0.9 microns, or other suitable thickness. The thickness of stray light absorbing layer16F-3may be 0.1 microns, at least 0.01 microns, at least 0.05 microns, less than 2.5 microns, less than 0.4 microns, less than 0.15 microns, or other suitable thickness. If desired, fibers16F may contain more layers, fewer layers, layers arranged in different orders, and/or may have other configurations.

FIG. 3shows how a collection of fibers16F may be deformed under heat and pressure using heated molding structures (a heated mold) such as die30. Die30may have multiple portions that are joined inwardly to press against fibers16F. Die30may have a recessed portion (see, e.g., recess30R) located between protruding portions30P. Recess30R may have a rectangular cross-sectional profile or other suitable shape. When die30presses inwardly on fibers16F, protruding portions30P push against fibers16F and cause fibers16F to bow outwardly and bulge into recess30R. During deformation operations, fibers16F may be heated to a temperature sufficient to soften fibers16F without melting fibers16F (e.g., a temperature of 150° C. or other suitable temperature sufficient to soften fibers16F). After the deformed fibers are cooled, the deformed fibers will solidify and become rigid. Plates16may then be formed that have desired shapes such as the illustrative plate shapes shown by dashed lines16′ ofFIG. 3.

FIG. 4is a diagram of illustrative fabrication equipment that may be used in forming fiber optic plate16. As shown inFIG. 4, the fabrication equipment may include equipment for forming fibers16F (e.g., fiber forming equipment) such as extruder32. Extruder32may produce spools of fibers. The fibers on the spools may include single-strand fibers and/or bundles that contain hundreds of fibers (as an example).

Spooled fiber may be supplied to process chamber36using spool feeder34. Process chamber36may have a guide plate with hundreds or thousands of holes for fibers16F (single fibers and/or bundles of fibers16F) from spool feeder34. The guide plate may, as an example, have a first side that receives about 10 million fibers16F and may guide these fibers into a loose fiber bundle that exits an opposing second side for further processing using die30(FIG. 3). The loose fiber bundle that exits the second may laterally cover an area approximately equal to the desired area of the fiber optic plate being formed. Fibers16F may be deformed by a mold in process chamber36.

Following formation of fiber optic plate structures in process chamber36, post processing tools38may be used to form finished fiber optic plates16. Tools38may include, for example, equipment to create desired surface shapes for the surfaces of each fiber optic plate16(e.g., machining equipment such as a grinding tool for forming curved edge profiles in the plate, saws or other cutting tools, polishing equipment for polishing the surfaces of each fiber optic plate16, etc.).

FIG. 5Ais a diagram of an illustrative extruder. As shown inFIG. 5A, extruder32may have hoppers40that contain material (e.g., polymers) for the different portions of plate16. A first of hoppers40may, for example, include a clear polymer of a first refractive index for forming core16F-1. A second of hoppers40may include a clear polymer of a second refractive index that is lower than the first refractive index. The polymer in the second hopper may be used in forming cladding16F-2. A third of hoppers40may include a polymer (e.g., a black light-absorbing polymer) for forming stray light absorbing layer16F-3. A fourth of hoppers40may include a polymer for forming binder16FB. The different polymers in hoppers40may be heated to soften and/or liquefy these polymers so that these different polymers may be extruded through extrusion head42(e.g., a spin-pack die) to form fibers16F. One or more spools such as spool44may collect the extruded fibers16F.

As shown inFIG. 5A, extruder32may have a series of parallel plates such as guide plates43to help prevent extruded fibers16F from becoming misaligned. Each of plates43may have a respective hole for each fiber16F being produced by the extruder, as shown by holes45in plates43ofFIG. 5B. Holes45may have any suitable shapes and sizes. As an example, holes45may be circular and each plate43may contain holes45of a common diameter. Appropriate hole size and appropriate separations between plates43may be determined by measuring the amount of travel fibers16F would experience in the absence of plates43. With an illustrative configuration, plate-to-plate separation DS and the separation between the uppermost of plates43and the bottom of head42may be about 1 cm, at least 0.1 cm, less than 10 cm, less than 1 cm, or other suitable distance and the diameter of holes45may decrease from plate to plate as a function of increasing distance from head42. There may be any suitable number of plates43(e.g., at least two, at least three, fewer than five, fewer than three, 2-4, 2-3, etc.). In an illustrative arrangement with two of plates43, the uppermost of plates43adjacent to head42may have holes45of a first diameter (e.g., 25 mm, at least 5 mm, less than 125 mm, etc.) and the lowermost of plates43may have holes of a second diameter that is smaller than the first diameter (e.g., 15 mm, at least 3 mm, less than 75 mm, etc.). Using fiber guide structures between head42and spool44may help maintain fiber order and alignment and may therefore help ensure fiber parallelism and coherence in plate16, ensuring that the image produced at the exit surface of plate16will be satisfactory for viewing by the user.

FIG. 6is a diagram of an illustrative process chamber for deforming fibers16F into a desired shape for fiber optic plates16. As shown inFIG. 6, computer-controlled spool feeder34may supply fibers16F at a desired feed rate to guide plate46. Guide plate46may be mounted in an opening in walls48of process chamber36. Guide plate46may have openings that receive fibers16F. In an illustrative configuration, guide plate46may have at least 100, at least 500, at least 2000, at least 5000, fewer than 100,000, fewer than 25,000, fewer than 10,000, or other suitable number of holes and may be configured to receive at least 1 million, at least 10 million, fewer than 100 million, or other suitable number of fibers. Fibers16F may be received from spools in spool feeder34at the upper side of guide plate46and may exit at the lower side of guide plate46as loose fiber bundle16F′.

Gases (e.g., nitrogen, oxygen, etc.) may be selectively introduced into interior62of chamber36from one or more computer-controlled gas sources52. Process chamber walls48and other portions of chamber36may be heated (e.g., using computer-controlled heaters50). For example, walls48and the gasses, fiber structures, and other structures in interior region62may be heated to about 150° C. or other suitable temperature sufficient to soften the fibers16F of fiber bundle16F′ without melting these fibers. Die30has computer-controlled positioners that position different die sections. A computer-controlled die arrangement allows die30to expand laterally outward to receive fiber bundle16F′ and to be moved laterally inward (towards fiber bundle16′) when it is desired to deform fiber bundle16F.

During deformation operations, the softened fibers of bundle16F pass into the area within die30. When it is desired to deform fibers16F of bundle16F′ to a desired shape, computer-controlled die gates54may be closed and the movable pieces of die30may be pushed inwardly against the sides of bundle16F′ by computer-controlled positioners. This indents fiber bundle16F′ where pressed by protruding portions30P and causes fiber bundle16F to bulge outwardly where aligned with recess30R. As a result, an outwardly protruding fiber bundle portion with deformed fibers is created (e.g., a bulge is created that runs around the periphery of the fiber bundle16F′). Gates54may then be opened.

Cutter56may have one or more parts with one or more sharp edges56T for cutting through fiber bundle16F′ within chamber interior62(e.g., while fibers16F are soft). The position of cutter56may be adjusted using a computer-controlled positioner. After the fiber bundle has been deformed by die30, cutter56may be moved laterally through the fiber bundle to cut off a layer of the fiber bundle that contains the deformed fibers. This cut off layer forms a rough plate of deformed fibers (e.g., a blank) that can later be machined, polished, and/or otherwise processed by tools38into a pair of finished fiber optic plates16(see, e.g., dashed lines16′ ofFIG. 3).

To ensure that the interior temperature of chamber36is maintained at a desired level, chamber36may be provided with a computer-controlled chamber gate such as gate58(e.g., one or more sliding doors or other structures for sealing chamber wall opening64). When it is desired to create a sealed chamber (e.g., so that a desired gaseous environment can be maintained in interior62and so that the temperature in interior62can be maintained as desired), gate58may be closed over opening64. When it is desired to remove a layer of deformed fibers that has been cut from bundle16F′ from interior62to the exterior of chamber36, gate58may be opened.

Illustrative steps involved in forming fiber optic plates for device10are shown inFIG. 7.

Following formation of fibers16F (e.g., using extruder32) and the loading of fiber sources into spool feeder34ofFIG. 6at step68, a loose bundle16F′ of fibers16F may be formed using guide plate46and moved (e.g., lowered) into chamber36for processing (e.g., using computer-controlled spools or other computer-controlled fiber bundle positioning equipment associated with spool feeder34).

During the operations of block70, chamber gate58for chamber32may be closed while a desired gaseous environment and temperature are created in interior62using gas sources52and heater50. Die gate54(which may sometimes be referred to as forming part of die30) may also be closed.

During the operations of block72, the computer-controlled mold formed from computer-controlled die30is pressed against fibers16F (e.g., the fibers in loose fiber bundle16F′) to deform fiber bundle16F′ into a desired shape, as shown inFIG. 3. The binder on fibers16F binds fibers16F together. The shape of die30(e.g., the presence of recess30R) causes the fiber bundle and its fibers to bulge outwardly into the recess, thereby deforming the fibers as desired. Die gate54may be opened after fiber deformation.

During the operations of block74, chamber gate58may be opened. This allows fiber bundle16F′ to be lowered by computer-controlled spool feeder34and allows computer-controlled cutter56to cut off a layer of fiber bundle16F′ and fiber bundle16F′ for removal from interior62. The cut-off piece of fiber bundle16F′ forms a plate with deformed fibers suitable for forming one or more (e.g., a pair) of fiber optic plates16. If desired, the cutter56may be used to cut two individual rough fiber plates from the deformed portion of fibers (e.g., cutter56may slice between the upper and lower portions of the deformed fibers aligned with recess30R in the example ofFIG. 3after these deformed fibers exit die30).

During the operations of block78, tools38may be used to form finished fiber optic plates from the layers of deformed fibers exiting processing chamber36. Tools38may include cutting tools (e.g., saws, etc.) for cutting, machining tools such as grinding tools for grinding the surfaces of a plate of deformed fibers to a desired rough shape (e.g., a shape with rounded peripheral edge profiles as shown inFIG. 1), and polishing tools for polishing the machined surfaces of the fiber optic plates into optically smooth surfaces for use in device10. After the finished fiber optic plates are produced in this way, additional structures (e.g., display layers, optional additional cover layers such as protective outer layers of glass or other materials, etc.) may be assembled with housings12and components18to form devices10).