PATENT DOCUMENT

Publication Number: US-11803060-B1
Application Number: US-202117223495-A
Country: US
Kind Code: B1

Title: Eyewear with display-optimized lenses

Abstract:
Eyewear such as sunglasses may include display-optimized lenses. The lenses may be optimized for viewing an external display and/or for viewing a display in the head-mounted device while also providing sun protection for the user&#39;s eyes. The lenses may include a polarizer and a color filter that are designed for a given target display. Lenses that are optimized for a display that emits linearly polarized light may include a linear polarizer. Lenses that are optimized for a display that emits circularly polarized light may include a circular polarizer. The circular polarizer may include a quarter wave plate and a linear polarizer. The color filter may have a transmission spectrum curve with peaks corresponding to the primary colors of the target display so that the color and brightness of display light is preserved while the brightness of sunlight is reduced.

Claims:
What is claimed is: 
     
       1. Sunglasses through which a viewer may view a display that emits polarized display light, wherein the display is part of an electronic device having a facial recognition sensor that emits infrared light, the sunglasses comprising:
 a supporting frame; and 
 a lens in the supporting frame, wherein the lens comprises:
 a circular polarizer that transmits the polarized display light; and 
 a light filter having a transmission spectrum that reduces a brightness of sunlight by a greater amount than the polarized display light, wherein the light filter has a transmission spectrum curve with first, second, and third peaks corresponding respectively to first, second, and third primary colors of the display, and wherein the transmission spectrum curve has a fourth passband that transmits the infrared light from the facial recognition sensor. 
 
 
     
     
       2. The sunglasses defined in  claim 1  wherein polarized display light emitted by the display is circularly polarized and wherein the circular polarizer transmits the circularly polarized display light. 
     
     
       3. The sunglasses defined in  claim 2  wherein the circular polarizer comprises a linear polarizer and a quarter wave plate. 
     
     
       4. The sunglasses defined in  claim 3  wherein the quarter wave plate is interposed between the linear polarizer and the light filter. 
     
     
       5. The sunglasses defined in  claim 1  wherein the light filter is optimized for a non-zero-degree viewing angle such that no color shift is imparted to the polarized display light at the non-zero-degree viewing angle. 
     
     
       6. The sunglasses defined in  claim 5  wherein the transmission spectrum is based on data gathered using numerical optimization techniques. 
     
     
       7. The sunglasses defined in  claim 5  wherein the first, second, and third peaks are separated by troughs that have non-zero values. 
     
     
       8. The sunglasses defined in  claim 1  wherein the light filter comprises a dichroic filter. 
     
     
       9. The sunglasses defined in  claim 1  wherein the light filter is configured to minimize color shifts in traffic lights. 
     
     
       10. Sunglasses through which a viewer may view a display of an external electronic device, wherein the display emits polarized display light having a color spectrum with first, second, and third peaks corresponding to respective first, second, and third primary colors, and wherein the first, second, and third peaks are separated by first troughs having non-zero values, the sunglasses comprising:
 a frame; and 
 a lens mounted to the frame, the lens comprising:
 a polarizer that transmits the polarized display light; and 
 a color filter having a transmission spectrum curve with peaks that correspond to the first, second, and third primary colors of the display, wherein the peaks are separated by second troughs that have non-zero values to transmit wavelengths associated with the first troughs to preserve the color spectrum of the polarized display light, and wherein the color filter is configured to transmit infrared light from a facial recognition sensor in the external electronic device. 
 
 
     
     
       11. The sunglasses defined in  claim 10  wherein a brightness of the polarized display light that passes through the lens is greater than a brightness of sunlight that passes through the lens, and wherein the transmission spectrum curve includes a local peak to preserve at least one of: a skin color and a sky color. 
     
     
       12. The sunglasses defined in  claim 10  wherein the polarized display light is linearly polarized and the polarizer comprises a linear polarizer. 
     
     
       13. The sunglasses defined in  claim 10  wherein the polarized display light is circularly polarized and the polarizer comprises a circular polarizer. 
     
     
       14. The sunglasses defined in  claim 13  wherein the circular polarizer comprises a linear polarizer and a quarter wave plate and wherein the linear polarizer is interposed between the quarter wave plate and the color filter.

Description:
This application claims the benefit of U.S. provisional patent application No. 63/016,813, filed Apr. 28, 2020, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to wearable devices, and, more particularly, to wearable devices such as eyewear. 
     BACKGROUND 
     Sunglasses and other eyewear may include filters that reduce the brightness of light reaching the user&#39;s eyes. 
     Conventional sunglasses use filters that significantly reduce the brightness of display light, making it difficult for users to view displays while wearing conventional sunglasses. 
     SUMMARY 
     Eyewear such as sunglasses may include display-optimized lenses. The lenses may be optimized for viewing an external display and/or for viewing a display in the head-mounted device while also providing sun protection for the user&#39;s eyes. 
     The display-optimized lenses may include a polarizer and a color filter that are designed for a given target display. Lenses that are optimized for a display that emits linearly polarized light may include a linear polarizer. Lenses that are optimized for a display that emits circularly polarized light may include a circular polarizer. The circular polarizer may include a quarter wave plate and a linear polarizer. The linear polarizer may be located between the quarter wave plate and the color filter. 
     The color filter may have a transmission spectrum curve with peaks corresponding to the primary colors of the target display so that the color and brightness of display light is preserved while the brightness of sunlight is reduced. The filter may be provided with other transmission spectrum characteristics depending on the desired filter attributes. For example, the light filter transmission spectrum may be designed to minimize the ratio of sunlight brightness to display light brightness reaching the user&#39;s eyes, to minimize color shifts in traffic lights and other driver safety signs, to minimize color shifts in memory colors such as skin colors, sky colors, tree colors, etc., to minimize color shifts in fluorescent lights, and/or to achieve other filter effects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram of illustrative system that includes eyewear with display-optimized lenses in accordance with an embodiment. 
         FIG.  2    is a cross-sectional side view of an illustrative system with eyewear for viewing a display that emits circularly polarized light in accordance with an embodiment. 
         FIG.  3    is a cross-sectional side view of an illustrative system with eyewear for viewing a display that emits linearly polarized light in accordance with an embodiment. 
         FIGS.  4 ,  5 , and  6    are graphs showing illustrative transmission spectrums for a filter that may be used in display-optimized lenses in accordance with an embodiment. 
         FIG.  7    is a cross-sectional side view of an illustrative filter that may be used in display-optimized lenses in accordance with an embodiment. 
         FIG.  8    is a graph showing how color difference varies with viewing angle for a filter that is optimized for a zero-degree viewing angle in accordance with an embodiment. 
         FIG.  9    is a graph showing how color difference varies with viewing angle for a filter that is optimized for a non-zero-degree viewing angle in accordance with an embodiment. 
         FIG.  10    is a flow chart of illustrative steps in producing a filter for a display-optimized lens in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Eyewear such as sunglasses may have display-optimized lenses that reduce the brightness of ambient light by a greater amount than the brightness of display light. The display-optimized lenses may each include a polarizer and a color filter. The polarization of the polarizer in the display-optimized lenses may match the polarization of light emitted from a target display, and the color filter may be customized based on the color spectrum of the target display. The display-optimized lenses may be optimized for an external display and/or may be optimized for a display that is part of the eyewear itself (e.g., a head-mounted display). 
     An illustrative system having eyewear with display-optimized lenses is shown in  FIG.  1   . System  10  may include head-mounted eyewear such as sunglasses  14  (sometimes referred to as glasses  14 , head-mounted device  14 , eyewear  14 , etc.). Sunglasses  14  may include one or more optical systems such as lens components  20  mounted in a support structure such as support structure  28 . Structure  28  may have the shape of a pair of eyeglasses (e.g., supporting frames), may have the shape of goggles, may form a housing having a helmet shape, or may have other configurations to help in mounting and securing the components of sunglasses  14  on the head of a user. 
     Lens components  20  may form lenses that allow a viewer (sometimes referred to herein as a user of sunglasses  14 , a wearer of sunglasses  14 , etc.) to view external objects through lenses  20  in direction  26 . For example, a user wearing sunglasses  14  may view external objects in the environment such as electronic device  12 , traffic lights  44 , and other objects in the environment through lenses  20 . Only a single lens  20  is shown in  FIG.  1   , but sunglasses  14  may include any suitable number of lenses  20 . Sunglasses  14  may, for example, include a left lens  20  aligned with a viewer&#39;s left eye and a right lens  20  aligned with a viewer&#39;s right eye. Arrangements in which sunglasses  14  include left and right lenses  20  for respective left and right eyes are sometimes described herein as an example. 
     Sunglasses  14  may include light filters for reducing the intensity of light that reaches the viewer&#39;s eyes. For example, sunglasses  14  may be worn outside and may be used to reduce the brightness of sunlight  24  from sun  48 . 
     Sunglasses  14  may be used purely for sun protection or sunglasses  14  may include displays that display virtual reality or augmented reality content (e.g., sunglasses  14  may be a head-mounted display). In this type of configuration, one or both of lens components  20  may be overlapped by a display such as display  30 . 
     In arrangements where sunglasses  14  are part of a head-mounted device with electrical components such as displays  30 , sunglasses  14  may also include control circuitry. Control circuitry in sunglasses  14  may include processing circuitry such as microprocessors, digital signal processors, microcontrollers, baseband processors, image processors, application-specific integrated circuits with processing circuitry, and/or other processing circuitry and may include random-access memory, read-only memory, flash storage, hard disk storage, and/or other storage (e.g., a non-transitory storage media for storing computer instructions for software that runs on the control circuitry). 
     Sunglasses  14  that form part of a head-mounted device with electrical components may also include input-output circuitry such as eye state sensors, range finders disposed to measure the distance to external objects, touch sensors, buttons, microphones to gather voice input and other input, sensors, and other devices that gather input (e.g., input from a user of sunglasses  14 ) and may include light-emitting diodes, displays, speakers, and other devices for providing output. Sunglasses  14  may, if desired, include wireless circuitry and/or other circuitry to support communications with a computer or other external equipment. 
     This is merely illustrative, however. If desired, sunglasses  14  may not include displays  30  and/or may be completely free of electrical components. Arrangements in which glasses  14  are sunglasses that do not include displays are sometimes described herein as an illustrative example. 
     A user may wear sunglasses  14  to protect his or her eyes from sunlight  24 . While wearing sunglasses  14  for sun protection, the user may wish to use an electronic device such as electronic device  12 . Electronic device  12  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a 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. In the illustrative configuration of  FIG.  1   , device  12  is a portable device such as a cellular telephone, media player, tablet computer, laptop computer, wrist device, or other portable computing device. Other configurations may be used for device  12  if desired. The example of  FIG.  1    is merely illustrative. 
     In the example of  FIG.  1   , device  12  includes a display such as display  16  mounted in a housing. The housing of device  12  be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. The housing may be formed using a unibody configuration in which some or all of the housing is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     Display  16  may be a touch screen display that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a display that is not touch-sensitive. Capacitive touch screen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures. 
     Display  16  may include an array of display pixels formed from organic light-emitting diodes (e.g., a thin-film organic light-emitting diode display), liquid crystal display (LCD) components, an array of electrophoretic display pixels, an array of plasma display pixels, microelectromechanical (MEMs) shutter pixels, electrowetting pixels, micro-light-emitting diodes (small crystalline semiconductor die), quantum dot light-emitting diodes, or display pixels based on other display technologies. The array of display pixels may display images for a user in active area of display  16 . In some arrangements, the active area may be surrounded on one or more sides by an inactive border region. In other arrangements, display  16  may be borderless or nearly borderless (e.g., where inactive border regions have been eliminated or minimized). 
     Display  16  may be protected using a display cover layer such as a layer of transparent glass, polymer, or crystalline material such as sapphire. Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button, a speaker port, or other component. Openings may be formed in the housing of device  12  to form communications ports (e.g., an audio jack port, a digital data port, etc.), to form openings for buttons, etc. 
     Electronic device  12  may have control circuitry. The control circuitry may include storage and processing circuitry for supporting the operation of device  12 . 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 device  12 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. 
     Input-output circuitry in electronic device  12  may be used to allow data to be supplied to device  12  and to allow data to be provided from device  12  to external devices. Input-output devices in device  12  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors, light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device  12  by supplying commands through the input-output devices and may receive status information and other output from device  12  using the output resources of input-output devices. Input-output devices of device  12  may include one or more displays such as display  16 . 
     Control circuitry in device  12  may be used to run software on device  12  such as operating system code and applications. During operation of device  12 , the software running on the control circuitry may display images on display  16  using an array of pixels in display  16 . While displaying images, display  16  may emit display light  22 . Display  16  may be covered with a polarizer such as polarizer  18 . Polarizer  18  may include one or more polarizer layers such as linear polarizer layers, one or more circular polarizer layers, one or more quarter wave plate layers, and/or one or more half wave plate layers. In some arrangements, polarizer  18  may include a linear polarizer and display light  22  may be linearly polarized light. In other arrangements, polarizer  18  may include a linear polarizer that is covered with a quarter wave plate. The quarter wave plate may convert the linearly polarized light received from the linear polarizer into circularly polarized display light  22 . These examples are merely illustrative. Device  12  may have other polarizer arrangements, if desired. 
     To protect the user&#39;s eyes from sunlight  24  while also allowing the user to view electronic device displays such as display  16  and/or display  30 , lenses  20  of sunglasses  14  may be display-optimized lenses that reduce the brightness of sunlight  24  by a greater amount than light from other light sources such as display light  22 . Display-optimized lenses  20  may include one or more polarizers such as polarizer  32  and one or more light filters such as light filter  34  (sometimes referred to as a color filter). Polarizer  32  and light filter  34  may be optimized for display viewing. Because different types of displays have different color spectrums and different polarizer configurations, display-optimized lenses  20  may include polarizer layers and light filter layers that are tailored to a target display. As used herein, “target display” may refer to any display that can be viewed through lenses  20 , such as display  16  of device  12  and/or display  30  in glasses  14 . 
     In the example of  FIG.  1   , light filter  34  is interposed between the user&#39;s eye and polarizer  32 . This is merely illustrative. If desired, polarizer  32  may be interposed between the user&#39;s eye and light filter  34 , and light filter  34  may be interposed between display  30  and polarizer  32 . 
     In configurations where glasses  14  include displays  30 , lenses  20  may be optimized for viewing of display  30  (e.g., by reducing the brightness of sunlight  24  while preserving the brightness and/or color of light from display  30  as much as possible or desired). Arrangements in which polarizer  32  and light filter  34  are optimized for viewing of display  16  are sometimes described herein as an example. However, it should be understood that polarizer  32  and light filter  34  may be optimized for any display, including displays  30  in glasses  14 . 
     Polarizer  32  and light filter  34  may have properties that are selected based on the characteristics of a given target display. In particular, the polarization properties of polarizer  32  may be selected based on the polarization of display light  22 , and the transmission spectrum of light filter  34  may be based on the color spectrum of display light  22 . For example, if polarizer  18  of device  12  is a circular polarizer and display light  22  is circularly polarized, polarizer  32  may be a circular polarizer. If polarizer  18  of device  12  is a linear polarizer and display light  22  is linearly polarized, polarizer  32  may be a linear polarizer. Polarizer  32  may be configured to transmit more display light  22  than sunlight  24 . For example, polarizer  32  may transmit 90% (or other suitable amount) of display light  22  while blocking 50% (or other suitable amount) of light from the environment (e.g., sunlight  24 ). This is merely illustrative. Polarizer  32  may transmit other amounts of display light  22  and sunlight  24 . 
     Light filter  34  may also be configured to transmit more display light  22  than sunlight  24 . In particular, light filter  34  may have a transmission spectrum that reduces the brightness of sunlight  24  (e.g., by blocking certain wavelengths of light that are present in sunlight  24  but not present in display light  22 ) without reducing (or without significantly reducing) the brightness of display light  22  (e.g., by transmitting certain wavelengths of light that are present in display light  22  and blocking certain wavelengths of light that are not present in display light  22 ). Light filter  34  may be a reflective filter (e.g., a dichroic filter) that reflects light that is not transmitted through filter  34  or may be an absorptive filter that absorbs light that is not transmitted through filter  34 . 
     If desired, light filter  34  may be specifically designed based on a target display. For example, light filter  34  may be produced by first obtaining the color spectrum of a given target display (e.g., display  16  and/or display  30 ) and then determining the desired transmission spectrum of light filter  34  based on the color spectrum of the target display (e.g., so that the transmission spectrum curve of color filter  34  has passbands and/or peaks that correspond to the primary colors of light emitted by display  16  and/or display  30 ). 
     In addition to optimizing light filter  34  for display viewing by using a transmission spectrum that reduces brightness of sunlight  24  more than display light  22 , it may be desirable to ensure that the color and/or brightness of light from other light sources is preserved and/or minimally altered after passing through lenses  22 . For example, light filter  34  may be designed so that the color and/or brightness of light  46  from traffic lights  44  (and/or other driver safety associated colors such as signs, placards, warning lights, etc.) is unchanged or only slightly changed after passing through lenses  20 . Preserving traffic light color, traffic sign color, and/or other driver safety associated colors is an illustrative example of the types of characteristics that light filter  34  may exhibit. In general, light filter  34  may be designed to preserve any suitable color. For example, common colors (sometimes referred to as “memory” colors) such as skin colors, sky colors, tree colors, fluorescent light colors, and/or any other desired color may be unchanged or minimally changed after passing through filter  34  by providing filter  34  with the appropriate transmission characteristics. 
       FIG.  2    is a cross-sectional side view of system  10  in which sunglasses  14  are optimized for a display that emits circularly polarized light. As shown in  FIG.  2   , display  16  of device  12  may be covered by polarizer  18 . Polarizer  18  may be a polarizer that is integral with display  16  and/or that is incorporated into device  12  during manufacturing of device  12 , or polarizer  18  may be an optional accessory that a user of device  12  may purchase separately and attach to display  16 . 
     In the example of  FIG.  2   , polarizer  18  is a circular polarizer that converts light from display  16  to circularly polarized light. Polarizer  18  may include one or more polarizer layers such as inner polarizer layer  36  and outer polarizer layer  38 . Inner polarizer layer  36  may be interposed between display  16  (e.g., the pixel array of display  16 ) and outer polarizer  38 . Inner polarizer  36  may be a linear polarizer (e.g., having a vertical transmission axis that runs parallel to the Z-axis of  FIG.  2    or other suitable transmission axis). Outer polarizer layer  38  may be a quarter wave plate that circularly polarizes the light received from polarizer  36  to produce circularly polarized display light  22 . 
     To transmit circularly polarized display light  22 , polarizer  32  of lenses  20  in sunglasses  14  may be a circular polarizer having an outer polarizer layer  40  and an inner polarizer layer  42 . Outer polarizer layer  40  may be a quarter wave plate that converts the circularly polarized display light  22  to linearly polarized light. Inner polarizer layer  42  may be interposed between outer polarizer  40  and light filter  34 . Inner polarizer layer  42  may be a linear polarizer (e.g., having a vertical transmission axis that runs parallel to the Z-axis of  FIG.  2    or having other suitable transmission axis that aligns with the polarization of display light  22 ). After circularly polarized display light  22  is converted to linearly polarized display light by quarter wave plate  40 , the linearly polarized display light may be aligned with the transmission axis of linear polarizer  42  and may pass through linear polarizer  42  towards light filter  34 . 
     Light filter  34  may be a color filter having a transmission spectrum that is optimized for display viewing while also providing satisfactory sun protection. As discussed in connection with  FIG.  1   , the transmission spectrum of light filter  34  may be customized for the color spectrum of display light  22  so that the brightness and/or color of display light  22  are preserved while the brightness of sunlight  24  is significantly reduced. For example, the transmission spectrum curve of light filter  34  may have passbands and/or peaks that correspond to the primary colors emitted by display  16  (e.g., red, green, and blue), while other wavelengths of light that are present in sunlight  24  may be blocked (e.g., reflected from filter  34  and/or absorbed by filter  34 ). 
     If desired, filter  34  may be provided with additional transmission spectrum characteristics so that certain colors are preserved and/or minimally changed by filter  34 . For example, filter  34  may be designed to preserve or minimally alter traffic light color, traffic sign color, and/or other driver safety associated colors, memory colors such as skin, sky, trees, etc., fluorescent light colors, and/or any other suitable color. This is, however, merely illustrative. If desired, filter  34  may only be optimized to reduce the brightness of sunlight  24  while preserving as much of the brightness and/or color of display light  22  as desired. 
     The combination of polarizer  32  and filter  34  may reduce the brightness of sunlight  24  by a first amount (e.g., between 90% and 85%, between 85% and 80%, between 95% and 85%, between 90% and 70%, less than 70%, more than 70%, or other suitable amount) and may reduce the brightness of display light  22  by a second amount (e.g., between 0% and 50%, between 40% and 50%, between 20% and 40%, between 10% and 50%, between 50% and 60%, between 60% and 70%, more than 50%, less than 50%, or other suitable amount) that is less than the first amount. The brightness ratio of sunlight  24  to display light  22  (e.g., as measured in the XYZ color space or other suitable color space) reaching the user&#39;s eyes through lenses  20  may be, for example, between 0.2 and 0.3, between 0.15 and 0.40, between 0.1 and 0.35, between 0.25 and 0.45, between 0.3 and 0.6, greater than 0.6, less than 0.6, or other suitable ratio. 
     The example of  FIG.  2    in which polarizer  32  is stacked in front of light filter  34  is merely illustrative. If desired, light filter  34  may be stacked in front of polarizer  32  so that outside light first passes through light filter  34  and then passes through polarizer  32  before reaching the user&#39;s eye. With this type of configuration, quarter wave plate  40  may be interposed between linear polarizer layer  42  and light filter  34 . 
       FIG.  3    is a cross-sectional side view of system  10  in which sunglasses  14  are optimized for a display that emits linearly polarized light. As shown in  FIG.  3   , display  16  of device  12  may be covered by polarizer  18 . 
     In the example of  FIG.  3   , polarizer  18  is a linear polarizer that converts light from display  16  to linearly polarized light. Polarizer  18  may include one or more polarizer layers such as linear polarizer layer  86 . Linear polarizer  86  may, for example, have a vertical transmission axis that runs parallel to the Z-axis of  FIG.  3    or other suitable transmission spectrum. 
     To transmit linearly polarized display light  22 , polarizer  32  of lenses  20  in sunglasses  14  may be a linear polarizer formed from linear polarizer layer  84 . Linear polarizer layer  84  may have a transmission axis that is parallel to the transmission axis of linear polarizer  86  (e.g., linear polarizer layer  84  may have a vertical transmission axis that runs parallel to the Z-axis of  FIG.  3    or other suitable transmission axis that aligns with polarized display light  22 ). The linearly polarized display light  22  may be aligned with the transmission axis of linear polarizer  84  and may pass through linear polarizer  84  towards light filter  34 . 
     Light filter  34  may be a color filter having a transmission spectrum that is optimized for display viewing while also providing satisfactory sun protection. As discussed in connection with  FIG.  1   , the transmission spectrum of light filter  34  may be customized for the color spectrum of display light  22  so that the brightness and/or color of display light  22  are preserved while the brightness of sunlight  24  is significantly reduced. For example, the transmission spectrum of light filter  34  may have passbands that encompass the peak wavelengths of the primary colors emitted by display  16  (e.g., red, green, and blue), while other wavelengths of light that are present in sunlight  24  may be blocked (e.g., reflected from filter  34  and/or absorbed by filter  34 ). 
     If desired, filter  34  may be provided with additional transmission spectrum characteristics so that certain colors are preserved and/or minimally changed by filter  34 . For example, filter  34  may be designed to preserve or minimally alter traffic light color, traffic sign color, and/or other driver safety associated colors, memory colors such as skin, sky, trees, etc., fluorescent light colors, and/or any other suitable color. This is, however, merely illustrative. If desired, filter  34  may only be optimized to reduce the brightness of sunlight  24  while preserving as much of the brightness and/or color of display light  22  as desired. 
     The combination of polarizer  32  and filter  34  may reduce the brightness of sunlight  24  by a first amount (e.g., between 90% and 85%, between 85% and 80%, between 95% and 85%, between 90% and 70%, less than 70%, more than 70%, or other suitable amount) and may reduce the brightness of display light  22  by a second amount (e.g., between 0% and 50%, between 40% and 50%, between 20% and 40%, between 10% and 50%, between 50% and 60%, between 60% and 70%, more than 50%, less than 50%, or other suitable amount) that is less than the first amount. The brightness ratio of sunlight  24  to display light  22  (e.g., as measured in the XYZ color space or other suitable color space) reaching the user&#39;s eyes through lenses  20  may be, for example, between 0.2 and 0.3, between 0.15 and 0.40, between 0.1 and 0.35, between 0.25 and 0.45, between 0.3 and 0.6, greater than 0.6, less than 0.6, or other suitable ratio. 
     The example of  FIG.  3    in which polarizer  32  is stacked in front of light filter  34  is merely illustrative. If desired, light filter  34  may be stacked in front of polarizer  32  so that outside light first passes through light filter  34  and then passes through polarizer  32  before reaching the user&#39;s eye. With this type of configuration, linear polarizer layer  84  may receive outside light such as display light  22  and sunlight  24  through light filter  34 . 
       FIG.  4    is a graph of an illustrative transmission spectrum that may be used in light filter  34 . Curve  90  of  FIG.  4    illustrates how much light of different wavelengths is transmitted through filter  34  when filter  34  has a discrete pass band configuration. In the example of  FIG.  4   , filter  34  has discrete pass bands such as pass bands  50 ,  52 , and  54 . The discrete pass bands may each encompass a given primary color of display  16 . For example, pass band  50  may transmit a range of wavelengths corresponding to blue light, pass band  52  may transmit a range of wavelengths corresponding to green light, and pass band  54  may transmit a range of wavelengths corresponding to red light. Filter  34  may block all light outside of these discrete pass bands, if desired. Filter  34  of  FIG.  4    may be configured to reduce the brightness of sunlight more than the brightness of display light. 
     In most displays, the display color spectrum does not have discrete color ranges but instead has a continuous curve with peaks at the display&#39;s primary colors and troughs between the peaks. The troughs between the peaks may not reach zero, so that the display can emit colors across the entire range of desired wavelengths. When 100% of the light between the pass bands is blocked, as in the example of  FIG.  4   , filter  34  may impart some color shifts to display light  22 . Color shifts may be reduced by using a filter  34  that with a transmission spectrum that is more continuous than the discrete pass band arrangement of  FIG.  4   . This type of example is illustrated in  FIG.  5   . 
     Curve  74  of  FIG.  5    illustrates how much light of different wavelengths is transmitted through filter  34 . In the example of  FIG.  5   , filter  34  has a continuous transmission spectrum such that curve  74  has peaks (e.g., peaks  60 ,  62 , and  64 ) separated by troughs (e.g., trough  56 ) that do not reach all the way to zero. Peaks  60 ,  62 , and  64  of curve  74  may each correspond to a given primary color of display  16 . For example, peak  60  may correspond to blue light, peak  62  may correspond to green light, and peak  64  may correspond to blue light. Filter  34  may block some or most of the light that is outside of the ranges of wavelengths encompassing the primary colors of display  16 . The presence of troughs such as trough  56  at non-zero values allows colors between the primary colors to pass through filter  34 , which can help preserve the color of display light  22 . Curve  74  may have other types of transmission spectrum features (e.g., local peaks such as local peak  58 , local troughs, and/or other features) that help reduce the brightness of sunlight  24  while preserving (as much as desired) the brightness and/or color of display light  22  and/or while preserving (or minimally altering) other colors such as traffic light colors, traffic sign colors, and/or other driver safety associated colors, memory colors such as skin, sky, trees, etc., fluorescent light colors, and/or any other suitable color. 
     In the example of  FIG.  5   , light filter  34  filters out infrared light. This is merely illustrative. If desired, filter  34  may be configured to transmit infrared light so that infrared cameras in device  12  may capture infrared images of the user&#39;s eyes (e.g., in devices that use facial recognition technology to verify the identity of a user). To ensure that device  12  can still properly verify the identity of a user wearing sunglasses  14 , filter  34  may be configured to transmit infrared light, as shown in the example of  FIG.  6   . 
     Curve  76  of  FIG.  6    illustrates how much light of different wavelengths is transmitted through light filter  34 . Similar to the example of  FIG.  5   , filter  34  has a continuous transmission spectrum with peaks separated by troughs that do not reach all the way to zero. The peaks of curve  76  may each correspond to a given primary color of display  16 . The presence of troughs at non-zero values and other transmission spectrum features (e.g., local peaks, local troughs, etc.) may help reduce the brightness of sunlight  24  while preserving the brightness and/or color of display light  22 . Curve  76  also transmits light in infrared wavelength range  78 , so that infrared light from an infrared light source in device  12  (e.g., a facial recognition sensor in device  12  that is used to verify the identity of a user wearing sunglasses  14 ). This allows device  12  to verify the identity of a user wearing sunglasses  14  by emitting infrared light (e.g., structured infrared light) towards the user&#39;s face and eyes and detecting the reflected infrared light that reflects from the user&#39;s face and eyes. The infrared light may pass through lenses  20  by incorporating an infrared pass region in the transmission spectrum of filter  34 . 
       FIG.  7    is a cross-sectional side view of an illustrative light filter  34 . In the example of  FIG.  7   , light filter  34  is a dichroic filter formed from a stack of thin films  68  on a substrate such as substrate  66 . Substrate  66  may be polymer, glass, or other suitable material. Thin films  68  may form a thin film interference filter by stacking dielectric layers such as dielectric layers  70  and  72  with alternating higher and lower refractive index values. Dielectric layers  70  and  72  may, for example, be formed from silicon oxide and niobium pentoxide, respectively, or may be formed from any other suitable combination of dielectric thin films. The total thickness T of filter  34  may be between 2 microns and 3 microns, between 1 micron and 4 microns, between 0.5 microns and 2 microns, between 2.5 microns and 3.5 microns, between 4 and 5 microns, greater than 5 microns, less than 5 microns, or other suitable thickness. 
     The arrangement of  FIG.  7    in which filter  34  is a reflective dichroic filter is merely illustrative. If desired, light filter  34  may be an absorptive filter. 
       FIGS.  8  and  9    show how a light filter such as light filter  34  may be optimized for different viewing angles to achieve the desired amount of color accuracy at different viewing angles. When light filter  34  is formed from a dichroic filter of the type shown in  FIG.  7   , the filter may impart a color shift to light that is transmitted through the filter. The amount of color shift may depend on the viewing angle that the dichroic filter is optimized for. 
     The amount of color shift imparted by a given filter may be determined by calculating the color difference (sometimes referred to as delta E or ΔE) between a color observed without the filter and the color observed with the filter. Color difference may be determined in any suitable color space (e.g., CIE La*b* color space, XYZ color space, RGB color space, etc.). 
       FIG.  8    illustrates how colors are shifted at different viewing angles when filter  34  is optimized for a zero-degree viewing angle. As shown in  FIG.  8   , dichroic filters that are optimized for a zero-degree viewing angle exhibit no color difference (color shifts) at a viewing angle of zero-degrees, but exhibit a sharp increase in color difference for viewing angles just outside of the zero-degree viewing angle. The maximum color shift may reach value V 1  at wide viewing angles. 
     If it is desired to preserve colors for a wider range of viewing angles, light filter  34  may be optimized for a non-zero-degree viewing angle, as shown in the example of  FIG.  9   . 
       FIG.  9    illustrates how colors are shifted at different viewing angles when filter  34  is optimized for viewing angle A. Angle A may be a non-zero value such as 15 degrees, 20 degrees, 25 degrees, 10 degrees, greater than 10 degrees, less than 10 degrees, or other suitable angle. As shown in  FIG.  9   , dichroic filters that are optimized for a viewing angle with a non-zero value exhibit a moderate color shift at a viewing angle of zero-degrees and no color shift at angle A. The maximum color shift (sometimes referred to as color difference) may reach value V 2  at wide viewing angles, which may be less than value V 1 . The moderate amount of color shifting at zero-degrees in  FIG.  9    may be less noticeable to the user than the sharp increase in color shifting that occurs when filter  34  is optimized for a zero-degree viewing angle. This is merely illustrative, however. In general, light filter  34  may be optimized for any suitable viewing angle. 
       FIG.  10    is a flow chart of illustrative steps involved in forming a display-optimized color filter such as light filter  34  for sunglasses  14 . 
     During the operations of block  200 , the color spectrum of the target display may be obtained. This may include, for example, obtaining the display specifications of a given cellular telephone display, a laptop display, a tablet computer display, a wrist watch display, television display, and/or any other suitable display. The color spectrum may be measured or may be a known (predetermined) color spectrum. 
     During the operations of block  202 , the desired filter attributes of light filter  34  may be determined. This may include, for example, determining what the maximum brightness reduction of sunlight  24  should be, what the maximum brightness reduction of display light  22  should be, what the desired brightness ratio of sunlight to display light should be, what the acceptable color error ranges should be for display light  22 , sunlight  24 , traffic lights and other driver safety colors, fluorescent lights, memory colors (e.g., skin colors, sky colors, tree colors, etc.), and/or other desired characteristics of light filter  34 . 
     The operations of block  202  may also include determining how to weight the various desired aspects of filter  34 . For example, there may be tradeoffs when trying to reduce the brightness of sunlight  24  while preserving the brightness and color of display light  22 . Different weights may be applied to the desired filter attributes depending on the level of importance of each filter attribute. In particular, a formula may be used to obtain the desired filter characteristics. The formula may include multiple terms, each term corresponding to a different filter attribute. For example, some terms may maximize transmission of certain colors and other terms may minimize transmission of other colors. Different weights may be applied to the different formula terms depending on the level of importance of each term. For example, reducing sunlight brightness may be more important than preserving colors of fluorescent lights, so the term that corresponds reducing sunlight brightness may be weighted more heavily than the term that preserves the colors of fluorescent lights, if desired. 
     In the operations of block  204 , the transmission spectrum of light filter  34  may be determined based on the color spectrum of the target display and the other desired filter attributes determined during the operations of block  202 . If desired, numerical optimization techniques may be employed to determine the transmission spectrum that best fits the desired filter characteristics. For example, computing equipment may make an initial guess of the transmission spectrum followed by an iterative process to refine the transmission spectrum to the best final result that satisfies a figure of merit (e.g., minimization techniques, making a derivative equal to zero by comparing and filtering intermediate results, etc.). In general, any suitable numerical methods may be used to obtain the transmission spectrum of filter  34  based on the color spectrum of the target display and other desired filter attributes. 
     In the operations of block  206 , a filter having the transmission spectrum determined during the operations of step  204  may be produced. This may include, for example, forming thin-film interference layers on a substrate to form a dichroic filter and/or forming other suitable filter layers to produce filter  34  with the display-optimized transmission spectrum. 
     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: 20210406
Publication Date: 20231031
Grant Date: 20231031
Priority Date: 20200428
Inventors: WILBURN, BENNETT S.
MOISANT-THOMPSON, JONATHAN C.
CHAPIRO, ALEXANDRE
HUNTER, SETH E.
LYNGNES, OVE
BONNIER, NICOLAS P.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02C7/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02C11/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/0178", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0187", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02C7/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/0187", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0178", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02C11/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B2027/0187", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0178", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02C7/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02C7/10", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 88534471