PATENT DOCUMENT

Publication Number: US-11314005-B2
Application Number: US-201916298992-A
Country: US
Kind Code: B2

Title: Electronic device with infrared transparent one-way mirror

Abstract:
An electronic device or other equipment may include an infrared-transparent one-way mirror. The infrared-transparent one-way mirror may be formed by a layer of material that is supported by a head-mounted support structure or other support structure. The support structure may support the layer of material so that the layer of material separates an exterior region from an interior region. Optical components in the interior region may be overlapped by the layer of material. The optical components may include visible light components such as a visible light camera and infrared components such as an infrared light-emitting device and an infrared light sensor. The optical components may operate through the layer of material while being hidden from view by the reflective appearance of the one way mirror from the exterior region.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a head-mountable support structure; 
 a layer supported by the head-mountable support structure that is configured to separate an exterior region from an interior region and that is partially transparent to visible light passing from the exterior region to eye boxes in the interior region; and 
 optical sensors configured to operate through the layer at a visible light wavelength and at an infrared light wavelength, wherein the layer includes a visible-light reflecting layer and a visible-light absorbing layer, wherein the visible-light reflecting layer reflects more visible light at the visible light wavelength than the visible-light absorbing layer, wherein the visible-light-absorbing layer absorbs more visible light than the visible-light reflecting layer at the visible light wavelength, and wherein the layer is more transparent at the infrared light wavelength than at the visible light wavelength. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the optical sensors comprise:
 a visible light camera configured to operate at the visible light wavelength; 
 an infrared light source configured to operate at the infrared light wavelength; and 
 an infrared light sensor configured to operate at the infrared light wavelength. 
 
     
     
       3. The electronic device defined in  claim 2  wherein the layer supported by the head-mountable support structure comprises a substrate layer that is transparent at the visible light wavelength. 
     
     
       4. The electronic device defined in  claim 3  wherein the visible-light reflecting layer comprises a thin-film interference filter structure formed from a stack of inorganic layers. 
     
     
       5. The electronic device defined in  claim 4  wherein the visible-light absorbing layer comprises a polymer coating on the thin-film interference filter structure. 
     
     
       6. The electronic device defined in  claim 5  wherein the thin-film interference filter structure is interposed between the substrate layer and the polymer coating. 
     
     
       7. The electronic device defined in  claim 5  wherein the polymer coating includes a dye configured to absorb more visible light at the visible light wavelength than infrared light at the infrared light wavelength. 
     
     
       8. The electronic device defined in  claim 3  wherein the visible-light reflecting layer and the visible-light absorbing layer are formed from first and second respective portions of a thin-film interference filter that includes a stack of inorganic layers with alternating refractive index values. 
     
     
       9. The electronic device defined in  claim 2  wherein the visible-light absorbing layer comprises a visible-light absorbing substrate and wherein the visible-light reflecting layer comprises a thin-film interference filter layer formed as a coating on the substrate. 
     
     
       10. The electronic device defined in  claim 9  wherein the visible-light absorbing layer comprises a molded polymer layer containing dye. 
     
     
       11. The electronic device defined in  claim 2  wherein the visible-light reflecting layer comprises a first stack of inorganic materials of alternating refractive index and wherein the visible-light absorbing layer comprises a second stack of inorganic materials. 
     
     
       12. The electronic device defined in  claim 11  wherein the second stack of inorganic materials includes alternating layers of first and second materials, wherein the first material is a dielectric and wherein the second material comprises a material that absorbs more light at the visible light wavelength than at the infrared light wavelength. 
     
     
       13. The electronic device defined in  claim 12  wherein the second material comprises silicon. 
     
     
       14. Apparatus, comprising:
 a support structure; 
 a layer supported by the support structure that is configured to separate a first region from a second region and that is partially transparent to visible light passing from the first region to the second region; and 
 optical sensors in the second region that are configured to operate through the layer at a visible light wavelength and at an infrared light wavelength, wherein the layer includes a visible-light reflecting layer and a visible-light absorbing layer, wherein the visible-light reflecting layer is between the first region and the visible-light absorbing layer, wherein the visible-light absorbing layer is between the visible-light reflecting layer and the second region, wherein the visible-light reflecting layer reflects more visible light at the visible light wavelength than the visible-light absorbing layer, wherein the visible-light-absorbing layer absorbs more visible light than the visible-light reflecting layer at the visible light wavelength, and wherein the layer supported by the support structure is more transparent at the infrared light wavelength than at the visible light wavelength. 
 
     
     
       15. The apparatus defined in  claim 14  wherein the visible-light reflecting layer comprises a thin-film interference filter layer having a stack of inorganic layers. 
     
     
       16. The apparatus defined in  claim 15  wherein the visible-light absorbing layer comprises a molded polymer layer containing material that absorbs visible light more than infrared light and wherein the stack of inorganic layers forms a coating on the molded polymer layer. 
     
     
       17. The apparatus defined in  claim 15  wherein the layer comprises a substrate, wherein the visible-light absorbing layer comprises a polymer layer that absorbs visible light, wherein the polymer layer includes perforations, and wherein the visible-light reflecting layer is interposed between the visible-light absorbing layer and the substrate. 
     
     
       18. The apparatus defined in  claim 14  wherein the layer comprises a substrate and wherein the visible-light reflecting layer and the visible-light absorbing layer are formed from a thin-film interference layer coating on the substrate. 
     
     
       19. An electronic device, comprising:
 a head-mountable support structure; 
 an infrared-transparent one-way mirror coupled to the head-mountable support structure; 
 a visible light camera configured to receive visible light through the infrared-transparent one-way mirror; 
 an infrared light-emitting device configured to emit infrared light through the infrared-transparent one-way mirror; and 
 an infrared light camera configured to receive infrared light through the infrared-transparent one-way mirror. 
 
     
     
       20. The electronic device defined in  claim 19  wherein the infrared-transparent one-way mirror comprises a visible-light reflecting layer configured to partially reflect visible light and comprises a visible-light absorbing layer that is configured to absorb visible light and that is interposed between the visible-light reflecting layer and the visible light camera. 
     
     
       21. The electronic device defined in  claim 19  wherein the infrared-transparent one-way mirror has a non-neutral color cast. 
     
     
       22. The electronic device defined in  claim 19  wherein the infrared-transparent one-way mirror comprises a thin-film interference filter. 
     
     
       23. An electronic device, comprising:
 an infrared-transparent one-way mirror; 
 a visible light camera configured to receive visible light through the infrared-transparent one-way mirror, wherein the infrared-transparent one-way mirror comprises:
 a substrate having a textured surface; 
 a thin-film interference filter on the textured surface; and 
 a visible-light absorbing layer, wherein the thin-film interference filter is between the textured surface and the visible-light absorbing layer; 
 
 an infrared light-emitting device configured to emit infrared light through the infrared-transparent one-way mirror; and 
 an infrared light camera configured to receive infrared light through the infrared-transparent one-way mirror. 
 
     
     
       24. The electronic device defined in  claim 23  further comprising an adhesive layer between the visible-light absorbing layer and the thin-film interference filter.

Description:
This application claims priority to U.S. provisional patent application No. 62/673,062, filed on May 17, 2018 which is incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to electronic devices, and, more particularly, to electronic devices with transparent layers. 
     BACKGROUND 
     Items such as sunglasses and ski googles are sometimes provided with coatings that create a one-way mirror effect. When the sunglasses or ski goggles are being worn by a user, these coatings may obscure the user&#39;s eyes from view. 
     Coatings for hiding internal components from view may be formed in electronic devices such as cellular telephones and computers. As an example, the underside of a cover glass layer in a cellular telephone may have coatings that hide internal components such as optical components from view while allowing these components to transmit or receive light through the coatings. 
     Challenges can arise when forming coatings to hide electronic device components. If care is not taken, coatings may not be sufficiently transparent to allow components to operate effectively or may not have a desired appearance. 
     SUMMARY 
     An electronic device or other equipment may include an infrared-transparent one-way mirror. The infrared-transparent one-way mirror may be formed by a layer of material that is supported by head-mounted support structure or other support structure. 
     The support structure in the electronic device may support the layer of material so that the layer of material separates an exterior region from an interior region. Optical components may be overlapped by the layer of material. The optical components may include visible light components such as a visible light camera and infrared components such as an infrared light-emitting device and an infrared light sensor. The optical components may operate through the layer of material while being hidden from view by the reflective appearance of the infrared-transparent one way mirror. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a top view of an illustrative electronic device in accordance with an embodiment. 
         FIG. 3  is a side view of an illustrative coating formed from a dielectric stack in accordance with an embodiment. 
         FIGS. 4, 5, 6, and 7  are cross-sectional side views of illustrative layers configured to form infrared transparent one-way mirrors in accordance with embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device may have a layer of one or more materials or other structure to separate interior and exterior regions. Light-based components may be located on an interior side of the layer. The layer of material may be transparent to infrared light so that infrared components such as infrared-light-emitting components and infrared-light-receiving components on the interior side of the layer can operate through the layer. At visible wavelengths, the layer may serve as a one-way mirror. 
     Due to the one-way mirror, the layer may reflect ambient light and appear shiny from the exterior. This blocks visible light components on the interior side of the layer from view. From the interior, the layer is sufficiently transparent to visible light to allow a user on the interior side of the layer to view objects through the layer and/or to allow visible-light components such as visible-light-emitting and visible-light-receiving components to operate through the layer. 
     The layer of material may be formed from one or more layers of dielectric, semiconductor, and/or conductor. Because the layer is configured to exhibit one-way mirror properties while being transparent to infrared light, the layer may sometimes be referred to as an infrared-transparent one-way mirror, an infrared-transparent one-way mirror layer or structure, etc. 
     An illustrative electronic device of the type that may include an infrared-transparent one-way mirror is shown in  FIG. 1 . As shown in  FIG. 1 , device  10  may include control circuitry  12 , communications circuitry  14 , and input-output devices  16 . Device  10  may be a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a desktop computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wristwatch device, a pendant device, a headphone or earpiece device, a head-mounted device such as glasses, goggles, a helmet, or other equipment worn on a user&#39;s head, 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 equipment is mounted in a kiosk, in an automobile, airplane, or other vehicle, a removable external case for electronic equipment, an accessory such as a remote control, computer mouse, track pad, wireless or wired keyboard, or other accessory, and/or equipment that implements the functionality of two or more of these devices. 
     Control circuitry  12  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as 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  12  may be used to gather input from sensors and other input devices and may be used to control output devices. The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors and other wireless communications circuits, power management units, audio chips, application specific integrated circuits, etc. 
     To support communications between device  10  and external electronic equipment, control circuitry  12  may communicate using communications circuitry  14 . Communications circuitry  14  may include antennas, radio-frequency transceiver circuitry, and other wireless communications circuitry and/or wired communications circuitry. Circuitry  14 , which may sometimes be referred to as control circuitry and/or control and communications circuitry, may, for example, support wireless communications using wireless local area network links, near-field communications links, cellular telephone links, millimeter wave links, and/or other wireless communications paths. 
     Input-output devices  16  may be used in gathering user input, in gathering information on the environment surrounding the user, and/or in providing a user with output. Devices  16  may include sensors  18 . Sensors  18  may 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 and/or other touch sensors and/or proximity sensors, optical sensors such as optical sensors that emit and detect light, ultrasonic sensors, monochromatic and color ambient light sensors, image 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), muscle activity sensors (EMG), radio-frequency sensors (e.g., radar and other ranging and positioning sensors), 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 and/or other measurements to determine distance and/or relative velocity, optical sensors such as visual odometry sensors that gather position and/or orientation information using images gathered with digital image sensors in cameras, gaze tracking sensors, visible light and/or infrared cameras having digital image sensors, humidity sensors, moisture sensors, and/or other sensors. 
     Input-output devices  16  may also include displays such as display  20 . Displays  20  may be organic light-emitting diode displays, displays based on arrays of light-emitting diodes formed from crystalline semiconductor dies, liquid crystal displays, electrophoretic displays, microelectromechanical systems (MEMs) displays such as displays with arrays of moving mirrors, and/or other displays. 
     If desired, input-output devices  16  may include other devices  22 . Devices  22  may include components such as status indicator lights (e.g., light-emitting diodes in devices  10  that serves as power indicators, and other light-based output devices), speakers and other audio output devices, electromagnets, permanent magnets, structures formed from magnetic material (e.g., iron bars or other ferromagnetic members that are attracted to magnets such as electromagnets and/or permanent magnets), batteries, etc. Devices  22  may also include power transmitting and/or receiving circuits configured to transmit and/or receive wired and/or wireless power signals. Devices  22  may include buttons, rotating buttons, push buttons, joysticks, keys such as alphanumeric keys in a keyboard or keypad, microphones for gathering voice commands, touch sensor input devices, and/or other devices for gathering user input. Devices  22  may also include output components such as haptic output devices and other output components. 
     In an illustrative arrangement, which may sometimes be described herein as an example, device  10  may be a head-mounted device. Consider, as an example, the arrangement of  FIG. 2 . As shown in  FIG. 2 , device  10  may have housing structures such as housing  24 . Housing  24  may be formed form materials such as polymer, glass, metal, ceramic, fabric, wood, other materials, and/or combinations of these materials. Housing  24  may be used to support structures such as layer  30  that separate interior region (interior)  26  from exterior region (exterior)  28 . In some configurations, housing  24  may have portions such as portion  24 ′ that help enclose some or all of interior  26  and separate interior  26  from exterior  28  (e.g., when housing  24  forms portions of the body of a vehicle or forms an enclosure for a cellular telephone or computer. In these arrangements, printed circuits, integrated circuits, mechanical structures, and other components (see, e.g., control circuitry  12 , communications circuitry  14  and/or input-output devices  16 ) may be located within the enclosure formed by housing  24 . Components such as these may also be coupled to housing  24  via a cable (as an example). In some arrangements, components for device  10  may be embedded within hollow portions of housing  24 . 
     If desired, housing  24  of  FIG. 2  may be configured to form head-mounted support structures that hold device  10  on a head of a user (with or without a rear strap or other rear portion  24 ′) and layer  30  may form a front portion for device  10  through which a user (e.g., user eyes in eye boxes  36 ) may view real-world objects such as illustrative real-world object  50  in exterior region  28 . Gaze tracking system  40  may track a user&#39;s eyes located in eye boxes  36 . A user&#39;s eyes in eye boxes  36  may view objects such as object  50  through layer  30  in direction  38 . While viewing real-world objects, display  20  may present images to the user&#39;s eyes in eye boxes  36 . For example, virtual content (images) may be displayed on display  20  and may be routed into a waveguide in layer  30  or adjacent to layer  30 . Optical couplers in regions  34  may direct the images out of layer  30  toward eye boxes  36  for viewing by the user. 
     In other arrangements, device  10  may form a pair of virtual reality googles (e.g., one or more displays and optical systems may be mounted on the inner surface of layer  30  in regions  34  and may block a user&#39;s view through layer  30 ). If desired, device  10  may also be a device such as a cellular telephone, a computer, or other portable electronic device. In this type of arrangement, layer  30  may, as an example, form part of a housing for device  10  (e.g., a rear wall of device  10 , etc.) or other portion of device  10  (e.g., an inactive portion of a display, etc.). Device  10  may also be a vehicle and may contain a motor, a vehicle body, steering equipment, and other vehicle components. In vehicles, layers such as layer  30  may form windows or parts of windows. 
     These configurations are illustrative. Other types of arrangements for device  10  may be used, if desired. Configurations in which device  10  is a head-mounted device, in which housing  24  forms a support structure(s) for layer  30  that is configured to allow device  10  to be worn on a head of the user, and in which layer  30  is a transparent layer through which a user may view real-world objects such as object  50  in exterior  28  while display  20  presents overlapped virtual content in eye boxes  36  in interior  26  are described herein as an example. 
     Layer  30  may include one or more sublayers such as layer  31 . These layers may include substrate layers, interior and/or exterior coatings, coatings that serve to reflect light, absorb light, and/or transmit light of different wavelengths by desired amounts, and/or other materials. During operation, a person in the vicinity of device  10  such as external viewer  62 , may view layer  30  and device  10  in direction  64 . Due to the one-way mirror effect produced by layer  30 , ambient light in exterior region  28  will illuminate layer  30  and will reflect off of layer  30 . Interior  26  is generally dimmer than exterior  28 , so bright ambient light in exterior  28  will overwhelm interior light that is transmitted through layer  30 . As a result, external viewer  62  will not be able to view interior  26  through layer  30 . This helps hide interior components such as light-based components  44  from view by external viewer  62 . 
     As shown in  FIG. 2 , light-based components  44  may be mounted in interior region  26  adjacent to the interior surface of layer  30 . Components  44  may include one or more visible light components such as visible-light component  46 . Component  46  may be a light producing component including one or more light-emitting diodes, lasers, displays, or other light generating circuitry and/or may be a light detecting component including one or more photodetectors (e.g., photodiodes or phototransistors), digital image sensors (visible digital image sensors, sometimes referred to as visible cameras or visible-light cameras), and/or other visible light sensor circuitry. For example, component  46  may be a visible light camera (digital image sensor) configured to capture real-world images that are presented to a user of device  10  using display  20  (e.g., component  46  may be a visual pass-through camera) and/or a component  46  may be a camera configured to perform object tracking on real-world objects. 
     Components  44  may also include infrared-light components such as infrared-light component  60 . Component  60  may include an infrared-light-emitting component such as component  58  (e.g., one or more infrared light-emitting diodes, infrared lasers, or other infrared light generating circuitry) and/or may include an infrared-light-detecting component such as component  52  (e.g., one or more infrared light detectors such as photodiodes, phototransistors, other photodetectors, infrared digital image sensors (infrared cameras), and/or other infrared components). Component  60  may form a proximity sensor, distance sensor, depth sensor, image sensor, and/or other suitable infrared sensor. As an example, component  60  may be an infrared depth sensor such as a structured light depth sensor that includes an array of lasers or other light-emitting device that emits beams of infrared light or other structured light and that includes an infrared digital image sensor for capturing images of objects illuminated with the emitted infrared light. 
     Layer  30  may be transparent to infrared light (e.g., at wavelengths of 700 nm to 2500 nm, at wavelengths of 700 to 1000 nm, or other suitable infrared wavelengths such as near infrared wavelengths). As an example, layer  30  may exhibit a transmittance of at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 98%, and/or less than 99.9% at infrared wavelengths of at least 700 nm, 750 nm, 780 nm, at least 800 nm, 780-2500 nm, less than 2000 nm, or other suitable wavelengths. Due to the infrared transparency of layer  30 , infrared light  54  that is emitted by component  52  may be transmitted through layer  30  from interior  26  to exterior  28  and infrared light  56  (e.g., reflected portions of light  54 ) to be sensed by infrared-light-detecting component  58  may be transmitted through layer  30  from exterior  28  to interior  26 . 
     To form a one way mirror, an outwardly facing portion of layer  30  (e.g., one or more of the outermost layers  31  of  FIG. 2 ) may be a visible-light reflective layer and an inwardly facing portion of layer  31  (e.g., one or more of the innermost layers  31  of  FIG. 2  or other layer  31  that is interposed between the reflective layer and eye boxes  36 ) may be a visible light absorbing layer. In an illustrative configuration, the visible-light reflective layer may reflect more visible light than it absorbs and the visible-light absorbing layer may absorb more visible light than it reflects (e.g., at visible light wavelengths of 390 to 700 nm). The visible-light reflective layer may also reflect more visible light (e.g., at visible light wavelengths of 390 to 700 nm) than the visible-light absorbing layer and the visible light absorbing layer may absorb more visible light (e.g., at visible light wavelengths of 390 to 700 nm) than the visible light reflecting layer. The reflective layer in layer  30  may, as an example, exhibit a mirror reflectivity of about 20-80%, at least 30%, less than 70%, or other suitable reflectivity to visible light from exterior  28  and a light absorption of less than 30%, less than 10%, less than 5%, less than 2%, at least 1%, or other suitable amount. The visible light absorbing layer may exhibit a visible light absorption of at least 25%, 20-80%, at least 30%, at least 44%, less than 80%, less than 60%, or other suitable absorption for visible light (e.g., at visible light wavelengths of 390 to 700 nm) passing through layer  30  from exterior  28  to interior  26  and may exhibit a visible light reflection (e.g., at visible light wavelengths of 390 to 700 nm) of less than 30%, less than 10%, less than 5%, less than 2%, at least 1%, or other suitable amount. 
     With an outer visible light reflecting layer and an inner visible light absorbing layer, layer  30  will form a one-way mirror and will have a shiny appearance to external viewer  62 . The shiny appearance of the outer surface of layer  30  to external viewer  62  helps block components  44  in interior region  26  from view from the exterior of device  10 . The reflective layer and the light absorbing layer may be configured to exhibit sufficient visible-light transmittance (e.g., 80-20%, less than 70%, less than 30%, less than 15%, etc.) to allow visible light components  46  to operate through layer  30 . At the same time, the reflective portion and the visible-light absorbing portion of layer  30  are sufficiently transparent to infrared light to allow infrared components  60  to operate satisfactorily through layer  30  (e.g., the one-way mirror may be an infrared-transparent one-way mirror). 
     Visible light  48  may, as an example, correspond to image light from object  50  (e.g., light from the real-world environment surrounding device  10 ) and may be used to gather real-world images (e.g., to present to a user, to use in a visual odometry system, etc.). 
     Infrared light  54  that is emitted by component  52  may be a single light beam (e.g., for lidar), may be multiple light beams (e.g., for a structured light sensor that projects multiple parallel beams of light), may be infrared flood illumination, may be infrared light emitted for an infrared proximity sensor, and/or may be other infrared light). Infrared light  56  that is received by component  58  may be infrared image light (e.g., when component  58  is an infrared image sensor), may be light received as part of a structured light depth sensing arrangement (e.g., when component  52  emits multiple light beams or other structured light), may be a reflected or backscattered infrared light beam in a lidar system or proximity sensor system, and/or may be other infrared light. 
     To form the infrared-transparent one-way mirror structure of layer  30 , layer  30  may, if desired, include one or more thin-film interference filters. By using thin-film interference filter structures in forming the reflective layer portion of layer  30 , visible light reflection can be enhanced while maintaining high infrared light transmission. 
     A thin-film interference filter structure may have a stack of thin-film layers. The layers may include materials such as dielectric materials (e.g., inorganic materials such as silicon oxide, silicon nitride, niobium oxide, titanium oxide, tantalum oxide, aluminum oxide other metal oxides, and/or organic materials such as clear polymers), semiconductors (e.g., silicon layers such as amorphous silicon and polysilicon layers), and metals. 
     In the illustrative configuration of  FIG. 3 , layer  32  (e.g., a coating layer or other layer  31  in layer  30 ) has outer thin-film interference filter layer portion  32 A and inner thin-film interference filter layer portion  32 B. Portion  32 A may include thin-film layers  70 . Layers  70  may be alternating higher refractive index and lower refractive index layers that form a thin-film interference filter that exhibits good infrared transparency and partial mirror reflectivity at visible light wavelengths. With one illustrative configuration, there are about 20-80 layers  70 . The higher index material in layers  70  may be silicon nitride or niobium oxide (as examples). The lower index material in layers  70  may be silicon oxide (as an example). Portion  32 B may include thin-film layers  72 . Layers  72  may be alternating higher refractive index and lower refractive index layers that form a thin-film interference filter that exhibits good infrared transparency and may contribute to the mirror reflectivity of layer  32  at visible wavelengths. The lower index material in layers  72  may be, for example, silicon oxide. The higher index material in layers  72  may be, for example, silicon, or other material that absorbs visible light more strongly (by a factor of at least 2, at least 5, at least 10, less than 100, or other suitable factor) than infrared light. 
     With this type of thin-film filter arrangement, portion  32 A may exhibit mirror reflectivity at visible wavelengths while being transparent to infrared light (e.g., layers  70  and, if desired, some of layers  72 ) may be used in forming an outer visible light reflecting layer for layer  30 ) and portion  32 B may exhibits visible light absorption while being transparent to infrared light (e.g., layers  72  may be used in forming an inner visible light absorbing layer for layer  30 ). As a result, layer  32  is transparent at infrared wavelengths and forms a one-way mirror structure (outer reflective layer covering an inner light absorbing layer) at visible wavelengths, as described in connection with  FIG. 2 . During operation, incoming visible light  66  is partly reflected (see reflected light  68 ) so that the outer surface of layer  32  appears shiny to viewer  62  while transmitting sufficient visible light  48  to allow visible-light component  46  to operate satisfactorily. The infrared transparency of the reflective layer portion  32 A and the visible-light absorbing portion  32 B of layer  32  allows infrared component  60  to operate satisfactorily (e.g., by allowing incoming infrared light  56  to reach component  58  and by allowing component  52  to emit infrared light  54  that passes through layer  32 ). 
     One or more layers such as illustrative thin-film interference filter layer  32  and, if desired, other types of materials that exhibit infrared light transparency and desired visible light properties (absorption, transmission, and reflection of desired amounts) can be incorporated into layer  30  so that layer  30  forms an infrared-transparent one-way mirror. Illustrative configurations for layer  30  that form infrared-transparent one-way mirrors are shown in  FIGS. 4, 5, 6, and 7 . 
     In the example of  FIG. 4 , layer  30  includes layer  80  and layer  82 . Layer  80  may be a transparent substrate layer. Layer  80  may be formed from glass, polymer, ceramic, sapphire or other crystalline substrate material, and/or other substrate material. Layer  80  has a first (outwardly facing) surface that faces exterior region  28  and an opposing second (inwardly facing) surface that faces coating  82 . Coating  82  has a first (outwardly facing) surface facing layer  80  and an opposing second (inwardly facing) surface facing interior region  26 . Coating  82  has reflective and absorptive properties that configure layer  30  to form an infrared-transparent one-way mirror. Coating  82  may be, for example, a coating formed from inorganic layers (e.g., inorganic layers deposited using physical vapor deposition techniques and/or other deposition techniques). 
     In an illustrative arrangement, coating  82  is formed from a stack of inorganic layers forming thin-film interference filter structures, as described in connection with layer  32  of  FIG. 3 . For example, layer  82  may include a first portion that is reflective at visible light wavelengths while being transparent at infrared light wavelengths (e.g., a thin-film filter mirror portion) such as portion  32 A of  FIG. 3  on the inwardly facing surface of layer  80  and may include a second portion (e.g., a thin-film filter structure) that absorbs visible light and transmits infrared light such as portion  32 B of  FIG. 3  on the inwardly facing side of portion  32 A (e.g., portion  32 A may be between portion  32 B and layer  80 ). 
     In the example of  FIG. 5 , coating layer  86  is formed on an outwardly facing side of layer  30  and substrate  80  is formed on an inwardly facing side of layer  30 . Layer  80  may be formed from glass, polymer (e.g., molded plastic), ceramic, sapphire or other crystalline substrate material, and/or other substrate material. The material that forms layer  80  may incorporate dye  84  or other light-absorbing material (e.g., pigment) that provides layer  80  with a desired amount of light absorption at visible wavelengths (e.g., layer  80  may be a light-absorbing substrate such as a layer of glass or polymer with a tint and may serve both as a substrate and as the inner visible light absorbing layer for layer  30 ). Layer  80  may be transparent at infrared wavelengths (e.g., more transparent than at visible light wavelengths). Coating layer  86  may be a reflective coating at visible light wavelengths and may be transparent at infrared wavelengths (e.g., more transparent than at visible wavelengths). Layer  86  may be a thin-film interference filter (see, e.g., portion  32 A of layer  32  of  FIG. 3 ) and/or may include a thin layer of metal or other layer that exhibits partial reflection and partial transmission at visible light wavelengths while being transparent at infrared wavelengths. 
     Another illustrative configuration for layer  30  is shown in  FIG. 6 . In the example of  FIG. 6 , layer  30  has a transparent outer substrate layer such as substrate layer  80 . Coating layer  88  may be formed on the side of substrate layer  80  facing interior  26 . Coating layer  88  may be a reflective coating (e.g., a thin-film interference filter such as portion  32 A of  FIG. 3  or a thin metal layer). Layer  90  may form a coating on the inner surface of layer  88 . Layer  90  may be a visible-light-absorbing layer formed from a polymer or other material that includes visible-light absorbing material (e.g., material  84  such as dye or pigment). Layers  88  and  90  may be transparent at infrared wavelengths (e.g., more transparent than at visible wavelengths). 
     If desired, different areas of layer  90  may have different configurations. For example, perforations P may be selectively formed in an area of layer  90  such as area A 2  to enhance light transmission. Components  44  may be overlapped by area A 2  (as an example). Other areas of layer  90  such as area A 1  may be free of perforations P. In other configurations, layer  90  has different thicknesses in areas A 1  and A 2  (e.g., area A 2  may be thinner to enhance visible and/or infrared light transmission for components  44 ). 
     One or more of layers  31  in layer  30  may be configured to impart a desired color cast to layer  30 . For example, a thin-film interference layer structure in layer  30  may be configured to exhibit a desired color cast (reddish, bluish, other non-neutral color casts, etc.) and/or a polymer layer or substrate layer in layer  30  may be provided with a desired colorant (e.g., a tint such as reddish or bluish dye or pigment, etc.). In this way, layer  30  may be provided with a desired color. All or part of the area covered by layer  30  may be provided with a desired color. Graded shading effects and other appearances that vary across the surface of layer  30  may also be provided by configuration of the interference filter structures and/or colorant patterns in layers  31 . 
     Another illustrative configuration for layer  30  is shown in  FIG. 7 . As shown in  FIG. 7 , layer  30  may include a substrate such as substrate  80  with a textured inner surface  96 . Layer  98  may be formed from a layer such as layer  32  or a layer such as portion  32 A of layer  32 . For example, layer  98  may be a stack of inorganic layers of alternating refractive index configured to form a thin-film interference filter structure that is partially reflective at visible light wavelengths while being transparent at infrared light wavelengths (e.g., a visible light reflecting layer). Layer  102  may be a visible light absorbing layer (e.g., a thin-film interference layer structure such as portion  32 B of  FIG. 3 , a polymer containing a visible-light absorbing dye, pigment, or other material that absorbs visible light, or other visible light absorbing material). Layer  102  may be transparent at infrared wavelengths. 
     If desired, adhesive  100  may be used to attach layer  102  to layer  98 . Adhesive  100  may be transparent at visible and infrared wavelengths. With this type of arrangement, incoming visible light  48  is partially reflected by layer  98 . Because layer  98  is formed on a textured surface, reflected light  48 ′ will be diffuse and layer  98  will have a matte appearance. The refractive index of layer  100  can be matched to that of layer  98  (e.g., the inner most layer of layer  98 ) within 10%, 5%, 2%, 1%, or other suitable amount and the distance between layer  98  and components  44  (e.g., visible light component  46 ) can be small (e.g., less than 1 mm, less than 0.3 mm, at least 0.001 mm, or other suitable distance), so that transmitted light  48 ″ will not be scattered significantly before reaching component  46  (e.g., incoming light sees little haze). Layer  98  will therefore appear matte in reflection, but will not diffuse transmitted light  48 ″ significantly. Arrangements of the type shown in  FIG. 7  may be used to create a matte appearance (at visible light wavelengths) for layer  30  while allowing layer  30  to serve as an infrared-transparent one-way mirror for covering components  44  so that components  44  can operate at visible and infrared wavelengths of interest. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20190311
Publication Date: 20220426
Grant Date: 20220426
Priority Date: 20180517
Inventors: WILSON, JAMES R.
VANDYKE, James W.
ROGERS, MATTHEW S.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B2027/0138", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B5/287", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0179", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/208", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0101", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/0138", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B5/208", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/0187", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B2027/0187", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0138", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/208", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0179", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/287", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 68532545