PATENT DOCUMENT

Publication Number: US-10475363-B2
Application Number: US-201414500458-A
Country: US
Kind Code: B2

Title: Displays with adaptive spectral characteristics

Abstract:
An electronic device may include a display having an array of display pixels and having display control circuitry that controls the operation of the display. The display control circuitry may adaptively adjust the spectral characteristics of display light emitted from the display to achieve a desired effect on the human circadian system. For example, the display control circuitry may adjust the spectral characteristics of blue light emitted from the display based on the time of day such that a user&#39;s exposure to the display light may result in a circadian response similar to that which would be experienced in natural light. The spectral characteristics of blue light emitted from the display may be adjusted by adjusting the relative maximum power levels provided to blue pixels in the display or by shifting the peak wavelength associated with blue light emitted from the display.

Claims:
What is claimed is: 
     
       1. A method for displaying images on an array of display pixels in a display having a white point, wherein the array of display pixels includes blue display pixels, the method comprising:
 with display control circuitry, gathering time of day information from a time source; and 
 adjusting spectral characteristics of display light emitted from the display based on the time of day information while maintaining the white point of the display on a black body curve, wherein adjusting the spectral characteristics of the display light comprises adjusting an overall intensity of blue light emitted from the display based on the time of day information, and wherein adjusting the overall intensity of blue light emitted from the display comprises adjusting maximum power levels delivered to the blue display pixels without shifting a peak wavelength of the blue light. 
 
     
     
       2. The method defined in  claim 1  further comprising:
 determining a daylight level based on the time of day information; and 
 adjusting the spectral characteristics of blue light emitted from the display based on the daylight level. 
 
     
     
       3. The method defined in  claim 2  wherein adjusting the spectral characteristics of the blue light emitted from the display comprises attenuating the blue light emitted from the display based on the time of day information. 
     
     
       4. The method defined in  claim 1  wherein adjusting the spectral characteristics of the display light based on the time of day information comprises:
 determining whether the time of day information is associated with daylight hours or nighttime hours; and 
 in response to determining that the time of day information is associated with nighttime hours, setting a maximum luminance for blue light at a level that is lower than that used during daylight hours. 
 
     
     
       5. A method for displaying images on an array of display pixels in a display having a white point, wherein the array of display pixels includes blue display pixels, the method comprising:
 with location detection circuitry, gathering geographic location information; 
 with a light sensor, gathering ambient lighting information; and 
 adjusting spectral characteristics of display light emitted from the display based on the geographic location information and the ambient lighting information while maintaining the white point of the display on a black body curve, wherein adjusting the spectral characteristics of the display light comprises adjusting an overall intensity of blue light emitted from the display based on the geographic location information and the ambient light information, and wherein adjusting the overall intensity of blue light emitted from the display comprises adjusting maximum power levels delivered to the blue display pixels without shifting a peak wavelength of the blue light emitted from the display. 
 
     
     
       6. The method defined in  claim 5  further comprising:
 determining a daylight level based on the geographic location information and the ambient lighting information; and 
 adjusting the spectral characteristics of the blue light emitted from the display based on the daylight level. 
 
     
     
       7. The method defined in  claim 6  wherein adjusting the spectral characteristics of the blue light emitted from the display comprises attenuating the blue light emitted from the display based on the daylight level. 
     
     
       8. The method defined in  claim 7  wherein the display pixels include blue display pixels and wherein adjusting the spectral characteristics of the display light comprises adjusting maximum power levels delivered to the blue display pixels based on the daylight level. 
     
     
       9. A method for displaying images on an array of display pixels in a display having a white point, wherein the array of display pixels comprises blue display pixels, the method comprising:
 with control circuitry, determining a daylight level; and 
 adjusting spectral characteristics of blue light emitted from the display based on the daylight level while maintaining the white point of the display on a black body curve, wherein adjusting the spectral characteristics of the blue light emitted from the display comprises adjusting an overall intensity of the blue light based on the daylight level, and wherein adjusting the overall intensity of the blue light comprises adjusting maximum power levels delivered to the blue pixels without shifting a peak wavelength of the blue light emitted from the display. 
 
     
     
       10. The method defined in  claim 9  wherein determining the daylight level comprises:
 gathering ambient lighting information from a light sensor; and 
 determining the daylight level based on the ambient lighting information. 
 
     
     
       11. The method defined in  claim 9  wherein determining the daylight level comprises:
 gathering time of day information from a time source; 
 gathering geographic location information from location detection circuitry; and 
 determining the daylight level based on the time of day information and the geographic location information.

Description:
This application claims the benefit of provisional patent application No. 62/006,781, filed Jun. 2, 2014, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices with displays and, more particularly, to electronic devices with displays having adaptive spectral characteristics. 
     The human circadian system may respond differently to different wavelengths of light. For example, when a user is exposed to blue light having a peak wavelength within a particular range, the user&#39;s circadian system may be activated and melatonin production may be suppressed. On the other hand, when a user is exposed to light outside of this range of wavelengths or when blue light is suppressed (e.g., compared to red light), the user&#39;s melatonin production may be increased, signaling nighttime to the body. 
     Conventional displays do not take into account the spectral sensitivity of the human circadian rhythm. For example, some displays emit light having spectral characteristics that trigger the circadian system regardless of the time of day, which can in turn have an adverse effect on sleep quality. 
     It would therefore be desirable to be able to provide improved ways of displaying images with displays. 
     SUMMARY 
     An electronic device may include a display having an array of display pixels and having display control circuitry that controls the operation of the display. The display control circuitry may adaptively adjust the spectral characteristics of display light emitted from the display to achieve a desired effect on the human circadian system. For example, the display control circuitry may adjust the spectral characteristics of blue light emitted from the display based on the time of day such that a user&#39;s exposure to the display light may result in a circadian response similar to that which would be experienced in natural light. 
     Other factors that may be taken into account when adjusting the spectral characteristics of display light include geographic location, time of year, season, ambient light, user input, and user preferences. 
     The spectral characteristics of blue light emitted from the display may be adjusted by adjusting the relative maximum power levels provided to blue pixels in the display or by shifting the peak wavelength associated with blue light emitted from the display. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device such as a portable computer having a display in accordance with an embodiment of the present invention. 
         FIG. 2  is a perspective view of an illustrative electronic device such as a cellular telephone or other handheld device having a display in accordance with an embodiment of the present invention. 
         FIG. 3  is a perspective view of an illustrative electronic device such as a tablet computer having a display in accordance with an embodiment of the present invention. 
         FIG. 4  is a perspective view of an illustrative electronic device such as a computer monitor with a built-in computer having a display in accordance with an embodiment of the present invention. 
         FIG. 5  is a schematic diagram of an illustrative system including an electronic device of the type that may be provided with a display having an adaptive color gamut in accordance with an embodiment of the present invention. 
         FIG. 6  is a schematic diagram of an illustrative electronic device having a display and display control circuitry in accordance with an embodiment of the present invention. 
         FIG. 7  is a diagram illustrating how the spectral characteristics of display light may be adjusted by shifting a peak wavelength associated with blue light emitted from the display in accordance with an embodiment of the present invention. 
         FIG. 8  is a diagram illustrating how the spectral characteristics of display light may be adjusted by attenuating the maximum luminance associated with blue light emitted from the display in accordance with an embodiment of the present invention. 
         FIG. 9  is a cross-sectional view of an illustrative backlit display having one or more switchable filters for adjusting the spectral characteristics of display light in accordance with an embodiment of the present invention. 
         FIG. 10  is a top view of an illustrative backlight for display having light sources with distinct spectral characteristics in accordance with an embodiment of the present invention. 
         FIG. 11  is a flow chart of illustrative steps involved in adjusting the spectral characteristics of display light to achieve a desired effect on circadian rhythm in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as cellular telephones, media players, computers, set-top boxes, wireless access points, and other electronic equipment may include displays. Displays may be used to present visual information and status data and/or may be used to gather user input data. 
     An illustrative electronic device of the type that may be provided with a display having an adaptive color gamut is shown in  FIG. 1 . Electronic device  10  may be a computer such as a computer that is integrated into a display such as a computer monitor, a laptop computer, a tablet computer, a somewhat smaller portable device such as a wrist-watch device, pendant device, or other wearable or miniature device, a cellular telephone, a media player, a tablet computer, a gaming device, a navigation device, a computer monitor, a television, or other electronic equipment. 
     As shown in  FIG. 1 , device  10  may include a display such as display  14 . Display  14  may be a touch screen that incorporates capacitive touch electrodes or other touch sensor components or may be a display that is not touch-sensitive. Display  14  may include image pixels formed from light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), plasma cells, electrophoretic display elements, electrowetting display elements, liquid crystal display (LCD) components, or other suitable image pixel structures. Arrangements in which display  14  is formed using organic light-emitting diode pixels are sometimes described herein as an example. This is, however, merely illustrative. Any suitable type of display technology may be used in forming display  14  if desired. 
     Device  10  may have a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. 
     Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     As shown in  FIG. 1 , housing  12  may have multiple parts. For example, housing  12  may have upper portion  12 A and lower portion  12 B. Upper portion  12 A may be coupled to lower portion  12 B using a hinge that allows portion  12 A to rotate about rotational axis  16  relative to portion  12 B. A keyboard such as keyboard  18  and a touch pad such as touch pad  20  may be mounted in housing portion  12 B. 
     In the example of  FIG. 2 , device  10  has been implemented using a housing that is sufficiently small to fit within a user&#39;s hand (e.g., device  10  of  FIG. 2  may be a handheld electronic device such as a cellular telephone). As show in  FIG. 2 , device  10  may include a display such as display  14  mounted on the front of housing  12 . Display  14  may be substantially filled with active display pixels or may have an active portion and an inactive portion. Display  14  may have openings (e.g., openings in the inactive or active portions of display  14 ) such as an opening to accommodate button  22  and an opening to accommodate speaker port  24 . 
       FIG. 3  is a perspective view of electronic device  10  in a configuration in which electronic device  10  has been implemented in the form of a tablet computer. As shown in  FIG. 3 , display  14  may be mounted on the upper (front) surface of housing  12 . An opening may be formed in display  14  to accommodate button  22 . 
       FIG. 4  is a perspective view of electronic device  10  in a configuration in which electronic device  10  has been implemented in the form of a computer integrated into a computer monitor. As shown in  FIG. 4 , display  14  may be mounted on a front surface of housing  12 . Stand  26  may be used to support housing  12 . 
     A schematic diagram of device  10  is shown in  FIG. 5 . As shown in  FIG. 5 , electronic device  10  may include control circuitry such as storage and processing circuitry  40 . Storage and processing circuitry  40  may include one or more different types of storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  40  may be used in controlling the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processor integrated circuits, application specific integrated circuits, etc. 
     With one suitable arrangement, storage and processing circuitry  40  may be used to run software on device  10  such as internet browsing applications, email applications, media playback applications, operating system functions, software for capturing and processing images, software implementing functions associated with gathering and processing sensor data, software that makes adjustments to display brightness and touch sensor functionality, etc. 
     To support interactions with external equipment, storage and processing circuitry  40  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  40  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, etc. 
     Input-output circuitry  32  may be used to allow input to be supplied to device  10  from a user or external devices and to allow output to be provided from device  10  to the user or external devices. 
     Input-output circuitry  32  may include wired and wireless communications circuitry  34 . Communications circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Input-output circuitry  32  may include input-output devices  36  such as button  22  of  FIG. 2 , joysticks, click wheels, scrolling wheels, a touch screen (e.g., display  14  of  FIG. 1, 2, 3 , or  4  may be a touch screen display), other touch sensors such as track pads or touch-sensor-based buttons, vibrators, audio components such as microphones and speakers, image capture devices such as a camera module having an image sensor and a corresponding lens system, keyboards, status-indicator lights, tone generators, key pads, and other equipment for gathering input from a user or other external source and/or generating output for a user or for external equipment. 
     Sensor circuitry such as sensors  38  of  FIG. 5  may include an ambient light sensor for gathering information on ambient light levels, proximity sensor components (e.g., light-based proximity sensors and/or proximity sensors based on other structures), accelerometers, gyroscopes, magnetic sensors, and other sensor structures. Sensors  38  of  FIG. 5  may, for example, include one or more microelectromechanical systems (MEMS) sensors (e.g., accelerometers, gyroscopes, microphones, force sensors, pressure sensors, capacitive sensors, or any other suitable type of sensor formed using a microelectromechanical systems device). 
       FIG. 6  is a diagram of device  10  showing illustrative circuitry that may be used in displaying images for a user of device  10  on pixel array  92  of display  14 . As shown in  FIG. 6 , display  14  may have column driver circuitry  120  that drives data signals (analog voltages) onto the data lines D of array  92 . Gate driver circuitry  118  drives gate line signals onto gate lines G of array  92 . Using the data lines and gate lines, display pixels  52  may be configured to display images on display  14  for a user. Gate driver circuitry  118  may be implemented using thin-film transistor circuitry on a display substrate such as a glass or plastic display substrate or may be implemented using integrated circuits that are mounted on the display substrate or attached to the display substrate by a flexible printed circuit or other connecting layer. Column driver circuitry  120  may be implemented using one or more column driver integrated circuits that are mounted on the display substrate or using column driver circuits mounted on other substrates. 
     During operation of device  10 , storage and processing circuitry  40  may produce data that is to be displayed on display  14 . This display data may be provided to display control circuitry such as timing controller integrated circuit  126  using graphics processing unit  124 . 
     Timing controller  126  may provide digital display data to column driver circuitry  120  using paths  128 . Column driver circuitry  120  may receive the digital display data from timing controller  126 . Using digital-to-analog converter circuitry within column driver circuitry  120 , column driver circuitry  120  may provide corresponding analog output signals on the data lines D running along the columns of display pixels  52  of array  92 . 
     Storage and processing circuitry  40 , graphics processing unit  124 , and timing controller  126  may sometimes collectively be referred to herein as display control circuitry  30 . Display control circuitry  30  may be used in controlling the operation of display  14 . 
     Display control circuitry  30  may be configured to adaptively adjust the spectral characteristics of light emitted from display  14  to achieve a desired effect on the human circadian system. For example, the human circadian rhythm may be most sensitive to wavelengths of light between 450 nm and 480 nm. When a user is exposed to light within this range of wavelengths (e.g., blue light having a wavelength of 470 nm), the user&#39;s melatonin production may be suppressed to daytime levels. On the other hand, when a user is exposed to light outside of this range of wavelengths (e.g., blue light having a different wavelength) or when blue light is suppressed (e.g., compared to red light), the user&#39;s melatonin production may be increased, signaling nighttime to the body. Display control circuitry  30  may adaptively adjust the spectral characteristics of display light emitted from display  14  (e.g., by adjusting the blue spectrum of light emitted from display  14 ) to achieve the desired circadian response from a user. 
     In one illustrative configuration, display control circuitry  30  may adjust the blue content of images displayed on display  14  based on the time of day. For example, display control circuitry  30  may increase the amount of blue light emitted from display  14  during daylight hours (e.g., to suppress melatonin production as daylight does) and may decrease the amount of blue light emitted from display  14  during evening hours (e.g., to promote melatonin production as darkness does). 
     In another illustrative configuration, display control circuitry may adjust the blue content of images displayed on display  14  based on user input. For example, a user may adjust a setting on device  10  to manually control the color spectrum of display  14  (e.g., to increase or decrease the amount of blue light emitted from display  14 ). 
     If desired, a user may activate a “jet-lag assistance” setting to help reduce jet-lag when traveling. In this mode, display control circuitry  30  may automatically adjust the blue content of images on display  14  when it is detected that the user is traveling (e.g., when a time zone change is detected). For example, display control circuitry  30  may automatically adjust the blue content of images on display  14  to promote melatonin production and thereby act as a sleep-aid (if so desired by the user). 
     As shown in  FIG. 6 , display control circuitry  30  may gather information from input-output circuitry  32  to adaptively determine optimal spectral characteristics for achieving the desired circadian response. For example, display control circuitry  30  may gather light information from one or more light sensors (e.g., an ambient light sensor, a light meter, a color meter, a color temperature meter, and/or other light sensor), time information from a clock, calendar, and/or other time source, location information from location detection circuitry (e.g., Global Positioning System receiver circuitry, IEEE 802.11 transceiver circuitry, or other location detection circuitry), user input information from a user input device such as a touchscreen (e.g., touchscreen display  14 ) or keyboard, etc. Display control circuitry  30  may adjust spectral characteristics of display light emitted from display  14  (e.g., may adjust peak wavelength or peak luminance of blue light emitted from display  14 ) based on information from input-output circuitry  32 . 
     Diagrams illustrating ways in which the spectral characteristics of blue light emitted from display  14  may be adjusted are shown in  FIGS. 7 and 8 . In the example of  FIG. 7 , a first color gamut may be defined by spectral distribution curve  84  having a peak at λ 1 , whereas a second color gamut may be defined by spectral distribution curve  86  having a peak at λ 2 . Blue light of the first color gamut may, for example, have a wavelength λ 1  between 450 nm and 480 nm, 440 nm and 480 nm, 460 nm and 490 nm, 465 nm and 485 nm, or other suitable wavelength. Blue light of the second color gamut may have a wavelength λ 2  between 400 nm and 420 nm, 400 nm and 430 nm, 400 nm and 450 nm, or other suitable wavelength. Wavelength λ 1  may be greater than wavelength λ 2 . 
     Wavelength λ 1  may, for example, correspond to the peak spectral sensitivity of the circadian response. Exposure to blue light with peak wavelengths at λ 1  may therefore result in suppressed nocturnal melatonin. Wavelength λ 2 , on the other hand, may be out of phase with the spectral sensitivity of the circadian response and may therefore result in unaffected, normal, or increased melatonin levels. 
     Display control circuitry  30  may switch between a first display mode in which images are displayed according to a color gamut defined by spectral distribution curve  84  and a second display mode in which images are displayed according to a color gamut defined by spectral distribution curve  86 . In the first mode, blue content in the images may be in sync with the peak spectral sensitivity of the circadian response. In the second mode, blue content in the images may be out of sync with the peak spectral sensitivity of the circadian response. 
     If desired, the blue content of images displayed on display  14  may be adjusted by adjusting the peak luminance of blue light (e.g., without shifting the peak wavelength). This type of adjustment is illustrated in  FIG. 8 . In the example of  FIG. 8 , a first color gamut may be defined by blue spectral distribution curve  88  (having a peak wavelength at λ 1 ), green spectral distribution curve  94 , and red spectral distribution curve  96 . The peak luminance of blue spectral distribution curve  88  may correspond to luminance L 1 . A second color gamut may be defined by blue spectral distribution curve  90 . The peak luminance of blue spectral distribution curve  90  may correspond to luminance L 2  (e.g., a luminance less than L 1 ). 
     Wavelength λ 1  may, for example, correspond to the peak spectral sensitivity of the circadian response. Exposure to bright blue light (e.g., blue light at luminance L 1 ) with peak wavelengths at λ 1  may therefore result in suppressed nocturnal melatonin. A lower brightness of blue light (e.g., blue light at luminance L 2 ), on the other hand, may result in unaffected, normal, or increased melatonin levels. If desired, luminance L 1  may be lower than the peak luminance associated with red light  96 . 
     With this type of spectral adjustment, display control circuitry  30  may switch between a first display mode in which images are displayed according to a color gamut defined by blue spectral distribution curve  88  and a second display mode in which images are displayed according to a color gamut defined by blue spectral distribution curve  90 . In the first mode, blue content in the images may be in sync with the peak spectral sensitivity of the circadian response and may be bright enough to trigger a response. In the second mode, blue light may still be aligned with the peak spectral sensitivity of the circadian response (if desired) but may be sufficiently dim to avoid suppression of nocturnal melatonin. 
     To adjust the spectral characteristics of display light emitted from display  14  according to the method described in connection with  FIG. 8 , display control circuitry  30  may adjust the relative maximum power levels that display control circuitry  30  delivers to pixels  52 . Maximum power levels for pixels  52  of a given color may be reduced, for example, by reducing the maximum possible digital display control value for the pixels of that color (e.g., from a maximum value of 255 to a maximum value of 251). When the blue channel of display  14  is attenuated in this way, other color channels (e.g., red and blue channels of display  14 ) may also be adjusted to maintain desired color characteristics for display  14  (e.g., to maintain a desired white point). If desired, a look-up table (LUT) such as a gamma LUT may be used to determine the appropriate digital display control values for display pixels  52  when the blue channel is attenuated. 
     If it is desired to attenuate blue light emitted from display  14  while maintaining the same number of digital display control values, the relative maximum power levels that display control circuitry  30  delivers to pixels  52  may be reduced by reducing the maximum allowable voltage with which pixels  52  in display  14  are driven. This may include, for example, adjusting the maximum allowable driving voltage for blue pixels through register settings (e.g., using a reset register). 
     To avoid undesirable shifts in color balance when adjusting the blue content of images on display  14 , steps may be taken to ensure that perceivable shifts in the display white point do not occur. For example, when blue light is attenuated by reducing the maximum possible digital display control value for the blue pixels, the red and green channels may be adjusted accordingly to maintain the display white point on a black body curve. Maintaining the white point along a black body curve may minimize perceivable color shifts. Display control circuitry  30  may, if desired manage the color balance and white point of display  14  based on ambient lighting conditions (e.g., based on sensor data from an ambient light sensor, camera, etc.). 
     A cross-sectional side view of an illustrative configuration for display  14  of device  10  (e.g., for display  14  of the devices of  FIG. 1 ,  FIG. 2 ,  FIG. 3 ,  FIG. 4  or other suitable electronic devices) is shown in  FIG. 9 . As shown in  FIG. 9 , display  14  includes backlight structures such as backlight unit  42  for producing backlight  44 . During operation, backlight  44  travels outwards (vertically upwards in dimension Z in the orientation of  FIG. 9 ) and passes through display pixel structures in display layers  46 . This illuminates any images that are being produced by the display pixels for viewing by a user. For example, backlight  44  illuminates images on display layers  46  that are being viewed by viewer  48  in direction  50 . 
     Display layers  46  may be mounted in chassis structures such as a plastic chassis structure and/or a metal chassis structure to form a display module for mounting in housing  12  or display layers  46  may be mounted directly in housing  12  (e.g., by stacking display layers  46  into a recessed portion in housing  12 ). Display layers  46  form a liquid crystal display or may be used in forming displays of other types. 
     In a configuration in which display layers  46  are used in forming a liquid crystal display, display layers  46  include a liquid crystal layer such a liquid crystal layer  68 . Liquid crystal layer  68  is sandwiched between display layers such as display layers  58  and  56 . Layers  56  and  58  are interposed between lower polarizer layer  60  and upper polarizer layer  54 . 
     Layers  58  and  56  are formed from transparent substrate layers such as clear layers of glass or plastic. Layers  56  and  58  are layers such as a thin-film transistor layer (e.g., a thin-film-transistor substrate such as a glass layer coated with a layer of thin-film transistor circuitry) and/or a color filter layer (e.g., a color filter layer substrate such as a layer of glass having a layer of color filter elements  98  such as red, blue, and green color filter elements arranged in an array). Conductive traces, color filter elements, transistors, and other circuits and structures are formed on the substrates of layers  58  and  56  (e.g., to form a thin-film transistor layer and/or a color filter layer). Touch sensor electrodes may also be incorporated into layers such as layers  58  and  56  and/or touch sensor electrodes may be formed on other substrates. 
     With one illustrative configuration, layer  58  is a thin-film transistor layer that includes an array of thin-film transistors and associated electrodes (display pixel electrodes) for applying electric fields to liquid crystal layer  68  and thereby displaying images on display  14 . Layer  56  is a color filter layer that includes an array of color filter elements  98  for providing display  14  with the ability to display color images. If desired, layer  58  may be a color filter layer and layer  56  may be a thin-film transistor layer. 
     During operation of display  14  in device  10 , control circuitry (e.g., display control circuitry  30  of  FIG. 6 ) is used to generate information to be displayed on display  14  (e.g., display data). The information to be displayed is conveyed from the control circuitry to display driver integrated circuit  62  using a signal path such as a signal path formed from conductive metal traces in flexible printed circuit  64  (as an example). 
     Display driver circuitry such as display driver integrated circuit  62  of  FIG. 9  is mounted on thin-film-transistor layer driver ledge  82  or elsewhere in device  10 . A flexible printed circuit cable such as flexible printed circuit  64  is used in routing signals to and from thin-film-transistor layer  58 . If desired, display driver integrated circuit  62  may be mounted on flexible printed circuit  64 . 
     Backlight structures  42  include a light guide plate such as light guide plate  78 . Light guide plate  78  is formed from a transparent material such as clear glass or plastic. During operation of backlight structures  42 , a light source such as light source  72  generates light  74 . Light source  72  may be, for example, an array of light-emitting diodes. 
     Light  74  from one or more light sources such as light source  72  is coupled into one or more corresponding edge surfaces such as edge surface  76  of light guide plate  78  and is distributed in dimensions X and Y throughout light guide plate  78  due to the principal of total internal reflection. Light guide plate  78  includes light-scattering features such as pits or bumps. The light-scattering features are located on an upper surface and/or on an opposing lower surface of light guide plate  78 . 
     Light  74  that scatters upwards in direction Z from light guide plate  78  serves as backlight  44  for display  14 . Light  74  that scatters downwards is reflected back in the upwards direction by reflector  80 . Reflector  80  is formed from a reflective material such as a layer of white plastic or other shiny materials. 
     To enhance backlight performance for backlight structures  42 , backlight structures  42  include optical films  70 . Optical films  70  include diffuser layers for helping to homogenize backlight  44  and thereby reduce hotspots, compensation films for enhancing off-axis viewing, and brightness enhancement films (also sometimes referred to as turning films) for collimating backlight  44 . Optical films  70  overlap the other structures in backlight unit  42  such as light guide plate  78  and reflector  80 . For example, if light guide plate  78  has a rectangular footprint in the X-Y plane of  FIG. 9 , optical films  70  and reflector  80  preferably have a matching rectangular footprint. 
     To adjust the spectral characteristics of display light emitted from display  14  according to the method described in connection with  FIG. 7 , display  14  may include one or more switchable color filters. For example, backlight structures  42  may include switchable filter  102  operable in first and second filtering states. In a first state, filter  102  may pass a first range of wavelengths corresponding to a first hue of blue light (e.g., a range centered around λ 1  of  FIG. 7 ) while blocking a second range of wavelengths corresponding to a second hue of blue light (e.g., a range centered around λ 2  of  FIG. 7 ). In a second state, filter  102  may pass the second range of wavelengths corresponding to the second hue of blue light (e.g., centered around λ 2  of  FIG. 7 ) while blocking the first range of wavelengths corresponding to the first hue of blue light (e.g., centered around λ 1  of  FIG. 7 ). 
     Filter  102  may be a tunable filter formed from microelectromechanical systems devices, cholesteric liquid crystal, tunable photonic crystal, guest-host liquid crystal film, polymer dispersed liquid crystal, and/or other structures. 
     In another suitable arrangement, switchable color filters may be implemented in color filter layer  56 . For example, blue color filter elements  98 B may be switchable color filter elements that are operable in first and second filtering states. In a first state, filters  98 B may pass a first range of wavelengths corresponding to a first hue of blue light  31  (e.g., a range centered around λ 1  of  FIG. 7 ) while blocking a second range of wavelengths corresponding to a second hue of blue light B 2  (e.g., a range centered around λ 2  of  FIG. 7 ). In a second state, filters  98 B may pass the second range of wavelengths corresponding to the second hue of blue light (e.g., centered around λ 2  of  FIG. 7 ) while blocking the first range of wavelengths corresponding to the first hue of blue light (e.g., centered around λ 1  of  FIG. 7 ). 
     In another suitable arrangement, light source  72  may include light sources with distinct spectral characteristics. This example is illustrated in  FIG. 10 . As shown in  FIG. 10 , backlight structures  42  may include an array of light-emitting diodes  72 . Light-emitting diodes  72 B 1  in backlight  42  may have a first emission spectrum, whereas light-emitting diodes  72 B 1  in backlight  42  may have a second emission spectrum. The blue spectrum of light emitted by light-emitting diodes  72 B 1  may correspond to a first hue of blue light B 1  (e.g., a range centered around λ 1  of  FIG. 7 ) while the blue spectrum of light emitted by light-emitting diodes  72 B 2  may correspond to a second hue of blue light B 2  (e.g., a range centered around λ 2  of  FIG. 7 ). 
     If desired, filters such as filter  104  (e.g., a bandpass filter, notch filter, or other suitable filter) may be used to adjust the spectral characteristics of light emitted by light-emitting diodes  72 . 
     Light emitting diodes  72 B 1  and  72 B 2  may be arranged in any suitable fashion. For example, light-emitting diodes  72  that emit light into edge  76 A may emit blue light of the first hue B 1 , whereas light-emitting diodes  72  that emit light into edge  76 B may emit blue light of the second hue B 2 . If desired, light-emitting diodes  72 B 1  and  72 B 2  may be interlaced with each other along one or more edges of light guide plate  78  and/or may be mounted together in a single semiconductor package. 
     Backlight switchable filter  102 , switchable color filter  98 B, and distinct sources of blue light  72 B 1  and  72 B 2  are illustrative examples of structures that may be used to adjust the spectral characteristics of light emitted from display  14 . These structures may be implemented together, separately, or in any combination, or other suitable structures may be used to adjust the spectral characteristics of display light in a similar manner. 
       FIG. 11  is a flow chart of illustrative steps involved in adjusting the spectral characteristics of display light emitted from display  14  to achieve a desired effect on circadian rhythm. 
     At step  200 , display control circuitry  30  may gather user context information from various sources in device  10 . For example, display control circuitry  30  may gather time, date, and/or season information from a clock or calendar application on device  10 , light information from one or more light sensors (e.g., an ambient light sensor, a light meter, a color meter, a color temperature meter, and/or other light sensor), location information from Global Positioning System receiver circuitry, IEEE 802.11 transceiver circuitry, or other location detection circuitry in device  10 , user input information from a user input device such as a touchscreen (e.g., touchscreen display  14 ) or keyboard, etc. 
     At step  202 , display control circuitry  30  may determine optimal spectral characteristics for display light based on the user context information gathered in step  200 . For example, display control circuitry  30  may determine that the blue spectrum of light emitted by display  14  should be adjusted to suppress nocturnal melatonin (e.g., in accordance with spectral distribution curve  84  or  88 ), or display control circuitry  30  may determine that the blue spectrum of light emitted by display  14  should be adjusted to promote nocturnal melatonin (e.g., in accordance with spectral distribution curve  86  or  90 ). 
     At step  204 , display control circuitry  30  may adjust display settings based on the optimal spectral characteristics determined in step  202 . This may include, for example, adjusting the relative maximum power levels that display control circuitry  30  delivers to pixels  52  (e.g., by adjusting the maximum possible digital display control value provided to pixels  52  or by reducing the maximum allowable pixel driving voltage through register settings). If using hardware to adjust the spectral distribution of display light in accordance with  FIG. 7 , step  204  may include adjusting a switchable filter in display  14  (e.g., filter  102  or filter  98 B) or may include adjusting backlight  42  to activate one set of light-emitting diodes (e.g., light-emitting diodes  72 B 1 ) and to deactivate another set of light-emitting diodes (e.g., light-emitting diodes  72 B 2 ). 
     At step  204 , display  14  may display colors with the optimal spectral characteristics (e.g., the optimal spectral characteristics for achieving the desired effect on the circadian rhythm as determined by user context information). 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20140929
Publication Date: 20191112
Grant Date: 20191112
Priority Date: 20140602
Inventors: CHEN, CHENG
TEOMAN, DENIZ
WU, JIAYING
ZHONG, JOHN Z.
JIANG, JUN
Assignee: APPLE INC
CPC Classifications: [{"code": "G09G2310/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0666", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3413", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0633", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/2003", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0633", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3413", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/2003", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G3/3406", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0666", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/064", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/2003", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2310/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0633", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3406", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3413", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3413", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/2003", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2310/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0666", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0633", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/064", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0666", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/2003", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2320/0666", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3413", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2310/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3406", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0633", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/064", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 54702494