PATENT DOCUMENT

Publication Number: US-9024530-B2
Application Number: US-201313746549-A
Country: US
Kind Code: B2

Title: Synchronized ambient light sensor and display

Abstract:
An electronic device may be provided that has a display. The display may produce light using a backlight unit or using an array of light-emitting display pixels. An ambient light sensor may be mounted under an active area of the display to measure ambient light that is transmitted through the display. The display may be periodically disabled to prevent the display from producing light that interferes with the ambient light sensor. Display pixels may be coupled to a common cathode switch that can be periodically opened or the backlight in a display with a backlight can be periodically turned off. Control circuitry for periodically disabling the display while enabling the ambient light sensor may be implemented using a display driver integrated circuit mounted to a display.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a display; 
 an ambient light sensor mounted under the display that receives ambient light through the display; and 
 control circuitry that periodically disables the display while enabling the ambient light sensor so that the ambient light sensor gathers ambient light sensor data without interference from light from the display, wherein the ambient light sensor exhibits an active duty cycle of less than 20%. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the display includes an array of display pixels each of which has a light-emitting diode and wherein the control circuitry is configured to periodically disable the light-emitting diodes. 
     
     
       3. The electronic device defined in  claim 2  wherein the light-emitting diodes are coupled to a common switch and wherein the switch is periodically closed to enable the light-emitting diodes and is periodically opened to disable the light-emitting diodes. 
     
     
       4. The electronic device defined in  claim 3  wherein the light-emitting diodes are organic light-emitting diodes. 
     
     
       5. The electronic device defined in  claim 4  wherein the control circuitry includes a display driver integrated circuit that periodically enables the ambient light sensor while producing display disable signals that open the switch to disable the light-emitting diodes. 
     
     
       6. The electronic device defined in  claim 1  wherein the display comprises a backlight unit and wherein the control circuitry is configured to provide a control signal that turns off the backlight unit while turning on the ambient light sensor. 
     
     
       7. The electronic device defined in  claim 6  wherein the display comprises a liquid crystal display. 
     
     
       8. The electronic device defined in  claim 1  wherein the control circuitry is configured to adjust display brightness for the display in response to data from the ambient light sensor. 
     
     
       9. An electronic device, comprising:
 a display; 
 an ambient light sensor mounted under the display that receives ambient light through the display; 
 control circuitry that periodically disables the display while enabling the ambient light sensor so that the ambient light sensor gathers ambient light sensor data without interference from light from the display; 
 a housing in which the display is mounted; and 
 a display cover layer, wherein the display cover layer has a clear central portion that covers an active area of the display, wherein the display cover layer has an opaque inactive border region with an opaque masking layer that surrounds the clear central portion, and wherein the ambient light sensor is mounted under the active area of the display. 
 
     
     
       10. Apparatus, comprising:
 a display having an array of display pixels that each contain a light-emitting diode; 
 a switch configured to provide power to the light-emitting diodes when closed and to interrupt power to the light-emitting diodes when open; 
 an ambient light sensor that measures ambient light that is transmitted through the array of display pixels; and 
 control circuitry that directs the switch to periodically interrupt power to the light-emitting diodes while using the ambient light sensor to measure the ambient light. 
 
     
     
       11. The apparatus defined in  claim 10  wherein the control circuitry includes a display driver integrated circuit that provides a periodic control signal to the switch to periodically interrupt the power to the light-emitting diodes. 
     
     
       12. The apparatus defined in  claim 11  wherein the light emitting diodes comprise organic light-emitting diodes. 
     
     
       13. The apparatus defined in  claim 12  wherein the periodic control signal periodically enables the ambient light sensor so that the ambient light sensor exhibits an active duty cycle of less than 20%. 
     
     
       14. An electronic device, comprising:
 a housing; 
 a display mounted in the housing; 
 an ambient light sensor that is mounted under an active area of the display and that receives ambient light through the display; and 
 display driver circuitry that periodically directs the display not to produce light while directing the ambient light sensor to measure the ambient light received through the display, wherein the display driver circuitry is configured to alternately enable and disable the ambient light sensor. 
 
     
     
       15. The electronic device defined in  claim 14  wherein the display driver circuitry comprises a display driver integrated circuit mounted on the display. 
     
     
       16. The electronic device defined in  claim 14  wherein the display comprises an array of organic light-emitting diode display pixels. 
     
     
       17. The electronic device defined in  claim 14  wherein that the ambient light sensor exhibits an active duty cycle of less than 20%. 
     
     
       18. The electronic device defined in  claim 14  wherein the display driver circuitry is attached to the display and wherein the ambient light sensor is mounted on a printed circuit. 
     
     
       19. The electronic device defined in  claim 18  further comprising a flexible printed circuit that couples the display driver circuitry on the display with the ambient light sensor on the printed circuit.

Description:
This application claims priority to U.S. provisional patent application No. 61/725,948 filed Nov. 13, 2012, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with displays and ambient light sensors. 
     Electronic devices often include displays. For example, portable devices such as cellular telephones and tablet computers are often provided with touch screen displays. 
     Ambient light sensors are sometimes provided in devices with displays to allow the devices to monitor ambient lighting conditions. A user of a portable device may often move between dim and bright lighting environments such as when transitioning between indoor and outdoor environments. Ambient light sensor readings may be taken in this type of device so that automatic display brightness adjustments may be made. When an increase in ambient light level is detected, control circuitry within the device may automatically increase the brightness of the display in the device to compensate for the additional glare and brightness associated with a bright ambient environment. This allows a user to view content on the display without interruption. Similarly, when a decrease in ambient light level is detected, the control circuitry within the device may automatically lower display brightness to a level that is appropriate for dim ambient lighting conditions. 
     Challenges arise when mounting ambient light sensors in an electronic device. In conventional devices, ambient light sensors are mounted under a window in an inactive display border region. The inactive display border region contains an opaque masking layer that hides internal components in the device from view by a user. The ambient light sensor window is formed from an opening in the opaque masking layer. 
     The need to provide sufficient space for mounting the ambient light sensor in alignment with the ambient light sensor window may consume more space within a device than desired. For example, this type of mounting arrangement may make the width of the inactive border region larger than desired. Although an opening could be formed in a device housing to accommodate the ambient light sensor, this type of mounting location may not always adequately measure ambient light levels in the vicinity of the display. 
     It would therefore be desirable to be able to provide improved ambient light monitoring schemes for electronic devices. 
     SUMMARY 
     An electronic device may be provided that has a display. The display may use a backlight unit to illuminate an array of display pixels or may have an array of light-emitting display pixels. An ambient light sensor may be mounted under an active portion of the display. The display may be sufficiently transparent to allow the ambient light sensor to make ambient light sensor measurements through the display. 
     The display may be periodically disabled to prevent the display from producing light that might interfere with the ambient light sensor. Display pixels may be coupled to a common cathode switch that can be periodically opened to disable the display or the light production by the display can be periodically interrupted by temporarily turning the backlight off. Control circuitry for periodically disabling the display while enabling the ambient light sensor so that the ambient light sensor acquires ambient light data may be implemented using a display driver integrated circuit mounted to the display. 
     Further features, their nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device of the type that may be provided with display and ambient light sensor structures in accordance with an embodiment of the present invention. 
         FIG. 2  is a schematic view of an illustrative electronic device of the type that may be provided with display and ambient light sensor structures in accordance with an embodiment of the present invention. 
         FIG. 3  is a cross-sectional side view of a portion of an electronic device having a display and ambient light sensor in accordance with an embodiment of the present invention. 
         FIG. 4  is a perspective view of a display having rows and columns of display pixels in accordance with an embodiment of the present invention. 
         FIG. 5  is a circuit diagram of an array of display pixels in accordance with an embodiment of the present invention. 
         FIG. 6  is a timing diagram showing how a display may be presented with frames of data when an ambient light sensor is not being actively used in accordance with an embodiment of the present invention. 
         FIG. 7  is a timing diagram showing how a common cathode or other display circuit may be used to periodically turn off a display while synchronously enabling an ambient light sensor so that the ambient light sensor can gather ambient light readings through the display without interference from light produced by the display in accordance with an embodiment of the present invention. 
         FIG. 8  is a flow chart of illustrative steps involved in operating an electronic device having an ambient light sensor that gathers ambient light sensor readings through a display in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device that may be provided with a display and ambient light sensor circuitry is shown in  FIG. 1 . Electronic devices such as device  10  of  FIG. 1  may be cellular telephones, media players, other handheld portable devices, somewhat smaller portable devices such as wrist-watch devices, pendant devices, or other wearable or miniature devices, gaming equipment, tablet computers, notebook computers, desktop computers, televisions, computer monitors, computers integrated into computer displays, or other electronic equipment. 
     In the example of  FIG. 1 , device  10  includes a display such as display  14 . Display  14  has been mounted in a housing such as housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or 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.). 
     Display  14  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  14  may include an array of display pixels formed from liquid crystal display (LCD) components, an array of electrophoretic display pixels, an array of plasma display pixels, an array of organic light-emitting diode display pixels, an array of electrowetting display pixels, or display pixels based on other display technologies. The brightness of display  14  may be adjustable. For example, display  14  may include a backlight unit formed from a light source such as a lamp or light-emitting diodes that can be used to increase or decrease display backlight levels and thereby adjust display brightness. Display  14  may also include organic light-emitting diode pixels or other pixels with adjustable intensities. In this type of display, display brightness can be adjusted by adjusting the intensities of drive signals used to control individual display pixels. 
     To prevent light that is produced by display  14  from interfering with the process of gathering ambient light sensor signals in device  10 , the backlight unit or the individual light-producing display pixels in display  14  can be disabled whenever the ambient light sensor is enabled. 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass or clear plastic. 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 such as button  16 . An opening may also be formed in the display cover layer to accommodate ports such as speaker port  18 . 
     In the center of display  14 , display  14  may contain an array of active display pixels. This region is sometimes referred to as the active area of the display. A rectangular ring-shaped region surrounding the periphery of the active display region may not contain any active display pixels and may therefore sometimes be referred to as the inactive area of the display. The display cover layer or other display layers in display  14  may be provided with an opaque masking layer in the inactive region to hide internal components from view by a user. 
     A schematic diagram of device  10  is shown in  FIG. 2 . As shown in  FIG. 2 , 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 a processor such as a microprocessor and other suitable integrated circuits. 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. 
     Input-output circuitry  32  may be used to allow input to be supplied to device  10  from a user or external devices and to 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  16  of  FIG. 1 , joysticks, click wheels, scrolling wheels, a touch screen such as display  14  of  FIG. 1 , 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. 
     Sensor circuitry such as sensors  38  of  FIG. 2  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. 
     A cross-sectional side view of electronic device  10  is shown in  FIG. 3 . As shown in  FIG. 3 , display  14  may be mounted in housing  12 . Display structures  44  such as a liquid crystal display module, an organic light-emitting diode display layer, or other display structures that include an array of active display pixels  70  may be formed under active area AA of display cover layer  42 . Display structures  44  may be formed from one or more display layers and may sometimes be referred to as display layers  44  or display  44 . Display cover layer  42  may be formed from a clear glass layer, a layer of transparent plastic, or other cover layer material. A layer of ink (e.g., black ink or white ink or ink of other colors) such as opaque masking layer  46  may be formed on the underside of display cover layer  42  in inactive area IA. 
     During operation of display  44 , light  82  from display pixels  70  (sometimes referred to as display pixel light  82  or display light  82 ) may be observed in active area AA of display  14  by a user such as viewer  84  who is viewing display  14  in direction  86 . 
     Device  10  may contain one or more substrates such as substrate  48 . Components  76  may be mounted on substrate  48 . Components  76  may include integrated circuits and other circuitry such as circuitry  32  and  40  of  FIG. 2 . To make ambient light measurements, device  10  may include one or more ambient light sensors such as ambient light sensor  78 . Display  44  is preferably at least somewhat transparent to ambient light  80  (e.g., display  44  may be less than 1% or more than 1% transparent, may be less than 0.5% transparent, may be less than 0.25% transparent, etc.). As shown in  FIG. 3 , ambient light sensor  78  may be mounted on substrate  48  under active area AA of display  44 , so that ambient light  80  is received through display  44 . 
     Substrate  48  may be a dielectric carrier such as a molded plastic carrier or may be a printed circuit. For example, substrate  48  may be a printed circuit such as a rigid printed circuit board formed from a dielectric material such as fiberglass-filled epoxy or may be a flexible printed circuit formed from a dielectric layer such as a sheet of polyimide or other flexible polymer layer. Metal interconnect paths may be provided on substrate  48  to allow substrate  48  to covey signals between components. 
     Substrate  48  may be coupled to additional substrates in device  10  such as printed circuit  50  using connectors such as connector  52  (e.g., a board-to-board connector or other connection structures). Substrate  50  may be, for example, a flexible printed circuit cable that is attached to display  44  at connection  72  (e.g., using conductive adhesive contacts such as anisotropic conductive film contacts, using connectors, using welds, using solder joints, etc.). 
     One or more circuits such as display driver integrated circuit  74  may be coupled to display  44  using flexible printed circuits or by mounting such circuits on display  44  as shown in  FIG. 3 . Display driver circuitry such as circuitry  74  may also be partly or fully mounted on other substrates such as substrate  48 . 
     Display driver circuitry may receive information from a processor or other circuitry (e.g., one or more integrated circuits  76  mounted on substrate  48 ) via path  50  and may convert this information into display pixel control signals for controlling the array of display pixels in display  14 . 
     A perspective view of display structures  44  in a configuration in which display pixels  70  have been arranged in a rectangular array having rows and columns is shown in  FIG. 4 . Display structures  44  of  FIG. 4  may be organic light-emitting diode display structures, liquid crystal display structures, display structures associated with other types of display such as an electrophoretic display, an electrowetting display, a plasma display, or other types of display structures. For example, display structures  44  may be a top emission or bottom emission organic light-emitting diode display and display pixels  70  may each contain an organic light-emitting diode. 
     As shown in  FIG. 4 , information to be displayed on display  44  may be received from control circuitry  40  ( FIG. 2 ) via path  50 . Path  50  may also be used to convey signals to control circuitry  40  (e.g., components  76  on board  48 ). Path  50  may be implemented using a structure such as a flexible printed circuit cable. 
     The information that is to be displayed on display  44  may include text, still images, and video. Display driver integrated circuit  74  may convert the information that is received over path  50  into data signals D that are driven onto corresponding date lines  96 . Display driver integrated circuit  74  and gate driver circuitry  92  may also provide gate control signals G on gate lines  94 . 
     Gate driver circuitry  92  may be implemented as part of display driver circuitry  74  or may be formed as separate thin-film transistor circuitry on a glass substrate layer in display  44  as shown in  FIG. 4 . As an example, gate driver circuitry  92  may be formed from polysilicon or amorphous silicon thin-film transistors. During operation, display driver circuitry  74  may provide control signals (e.g., clock signals, etc.) to gate driver circuits  92  via paths such as path  98 . Gate driver circuits  92  may, in turn, assert gate control signals G on gate lines  94  to sequentially load data from data lines D into the rows of display pixels  70  in display  44 . 
     In the example of  FIG. 4 , there is one gate driver circuit  92  on the left edge of the array of display pixels  70  and another gate driver circuit  92  on the right edge of the array of display pixels  70 . This is merely illustrative. If desired, gate driver circuitry  92  may run along one edge of display  44  and gate lines  94  may extend from that edge of the display across the array of display pixels  70 . 
     Gate driver circuitry  92  typically asserts gate line signals G on gate lines  94  in sequence (e.g., asserting a signal on gate line N while deasserting all other gate line signals, subsequently asserting gate control signal G on gate line N+1 while deasserting the gate control signal G on gate line N and the other gate lines, etc.). A sequence in which all gate line signals G have been successively asserted from the 0 th  row to the last row in display  44  is sometimes referred to as a frame of display data. Frames may be displayed at any suitable frequency (e.g., 50 Hz, 60 Hz, 62 Hz, 120 Hz, more than 60 Hz, less than 60 Hz, etc.). 
     The circuitry used in each display pixel  70  may depend on the type of display technology used in forming display  44 . For example, in a liquid crystal display, each display pixel  70  may contain electrodes for applying an electric field to an associated portion of a layer of liquid crystal material. A thin-film transistor may be provided in each display pixel  70  in this type of arrangement to load display data D into a storage capacitor within the display pixel. Storage capacitors and thin-film transistors may also be used in controlling the operation of an organic light-emitting diode display and other displays. 
     The storage capacitor in each display pixel may be used to retain the loaded data bit for that display pixel between successive frames. For example, the storage capacitor in a data pixel in row M may have a size sufficient to allow the storage capacitor to retain loaded data while gate driver circuitry  92  is used to load data into lines M+1 to K (where K is the number of rows in display  44 ) and while gate driver circuitry  92  is used to load data into lines 0 to M−1 before returning to line M. 
     A circuit diagram of a portion of an array of display pixels  70  in display  44  is shown in  FIG. 5 . As shown in  FIG. 5 , each display pixel  70  may, if desired, include a storage element such as storage capacitor Cs. Each display pixel  70  may also contain one or more control devices such as thin-film transistors  100 . Each transistor  100  may have a gate such a gate  102 , a drain such as drain  104 , and a source such as source  106 . Terminals such as source terminal  106  and drain terminal  104  may sometimes be referred to collectively as source-drain terminals. Gate lines  94  may be coupled to gate terminals such as gate terminal  102  of  FIG. 5  to control the operation of transistor  100 . 
     In displays such as organic light-emitting diode displays, display pixels  70  may each contain a light-emitting diode such as light-emitting diode  108  of  FIG. 5 . Each light emitting diode  108  may emit a respective pixel of light  82 . A shared power terminal such as common cathode terminal  118  may be used to supply a ground voltage from terminal  120  (or other suitable power signal) to all light-emitting diodes  108  in display  14  in parallel. Control signals on the gate lines and data lines may be used in determining how strongly each light-emitting diode  108  is driven. This allows control circuitry  40  to increase and decrease the brightness of display  14  in response to ambient light sensor signals from ambient light sensor  78 . 
     Switching circuitry such as switch  114  may be interposed in the power supply path between display pixels (and light-emitting diodes  108 ) and common power supply terminal  120 . Switch  114  may receive control signals on input  112  from control circuitry in device  10  such as display driver circuitry  74 . The control signals on input  112  may be used to open and close switch  114 . For example, switch  114  may be closed during time periods in which it is desired to enable display  44  and thereby allow pixels  70  to be driven to display images to viewer  84 . Switch  114  may be opened during time periods in which it is desired to temporarily disable display  44  by cutting off power to light-emitting diodes  108  in pixels  70 . As an example, switch  114  may be opened when it is desired to turn off display  44  for sufficiently long to allow ambient light sensor  78  to receive ambient light  80  without interference from display light  82 . 
     In displays such as liquid crystal displays, display backlight may be provided from a backlight unit such as backlight unit  110  of  FIG. 5 . Backlight unit  110  may contain a light guide plate or other optical structures that distribute the backlight to display  44  from an array of light-emitting diodes or other light source. In configurations for display  14  in which backlight unit  110  is used to provide backlight for display  44 , ambient light sensor  78  may be located between backlight unit  110  and display  44  or may be integrated into one of the structures of display  44  (e.g., by forming ambient light sensor  78  as a thin-film layer on a substrate or by mounting ambient light sensor  78  to a substrate). 
     Both in configurations in which ambient light is gathered by ambient light sensor  78  without passing directly through all of the layers of display  44  and in which ambient light is gathered by ambient light sensor  78  after being transmitted through display  44 , it may be helpful to temporarily disable display  44  while enabling ambient light sensor  78  to prevent the light that is produced by display  44  from interfering with the operation of ambient light sensor  78 . 
     Control signals on control input  116  may be used to control the operation of backlight unit  110  and thereby control the brightness of the backlight for display  44  (e.g., using signals that are modulated using pulse width modulating schemes or other suitable control schemes). At the same time that the backlight strength of backlight unit  110  is being adjusted, signals on the gate lines and data lines in display  44  may be used to create images from the display pixels  70  in display  44 . 
     The control signals on input  116  may be used to enable or disable light production for display  44 . For example, the control signals on input  116  may be used to enable display  44  and adjust the brightness of display  44  when it is desired to display images on display  44  for viewer  84 . The control signals on input  116  may also be used to periodically disable display  44 . For example, control signals on input  116  may be used to temporarily turn off display  44  (i.e., the backlight in display  44 ) for sufficiently long to allow ambient light sensor  78  to receive ambient light  80  without interference from display backlight (e.g., display light  82  that is passing through pixels  70 ). 
       FIG. 6  is a timing diagram showing how display  14  may be provided with display data in frames  122 . During each frame, display data D is driven onto data lines  96  by display driver circuitry  74  while successive gate line signals G on gate lines  94  are asserted to load the data into successive rows of display pixels  70  (e.g., to load the data bits for the image that is to be displayed onto the storage capacitors Cs of display pixels  70 ). After a full frame of data has been loaded, the data loading process may repeat (i.e., display driver circuitry  74  may load another frame  122  of data into the storage capacitors of the array of display pixels in display  44 ). The length of each frame  122  may be about 5-20 ms or other suitable duration, depending on the frame rate of display  14 . For example, when display  14  has a frame rate of 62 Hz, each frame  122  will have a duration of about 16 ms. 
     It may be desirable to adjust display brightness automatically based on ambient light sensor readings. For example, it may be desirable for device  10  to automatically increase display brightness when brighter conditions are detected such as when a user carries electronic device  10  from a dim indoor environment into a brighter outdoor environment and it may be desirable for device  10  to automatically decrease display brightness when dimmer conditions are detected such as when a user carries electronic device  10  from a bright outdoor environment into dimmer indoor conditions. 
     When automatic real time adjustments to display brightness are desired, the frame-by-frame data loading process of  FIG. 6  may be modified to prevent display light that is generated by the display from interfering with the ability of ambient light sensor  78  to monitor how much ambient light is present in the vicinity of display  14 . If display brightness is not adjusted during ambient light signal acquisition, there is a potential that ambient light reading accuracy will be degraded or that ambient light signals cannot be successfully acquired due to the presence of interfering display light. 
       FIG. 7  is a timing diagram showing how display  14  may be periodically disabled to allow ambient light sensor data to be gathered by ambient light sensor  78  without being affected by display light (e.g., display pixel light produced when illuminating display pixels  70  with backlight from backlight unit  110  or display pixel light produced by the display pixels of light-emitting diodes  108 ). As shown in  FIG. 7 , data may be provided to display  44  in frames  122 . Each frame may have a duration of about 5-20 ms or other suitable duration, as determined by the frame rate of display  14 . If, for example, display  14  has a frame rate of 62 Hz, each frame  122  will have a length of about 16 ms. 
     Control circuitry in device  10  such as display driver  74  may issue periodic control signals that are used as display disable signals and ambient light sensor enable signals. As shown in  FIG. 7 , for example, display  44  may be turned on while ambient light sensor  78  is turned off and display  44  may be turned off when ambient light sensor  78  is turned on. In an illustrative configuration in which each frame  122  has a period of 16 ms, it may be desirable to turn ambient light sensor  78  on (and display  44  off) for two 1 ms intervals and to turn ambient light sensor  78  off (and display  44  on) for two 7 ms intervals during each frame. The on and off periods of ambient light sensor  78  (and display  44 ) may alternate. In the illustrative configuration in which ambient light sensor  78  is on for 1 ms and off for 7 ms, the active duty cycle of ambient light sensor  78  will be ⅛ (i.e., 12.5%). In general, the ambient light sensor active duty cycle may be 1-99%, 5-80%, more than 4%, less than 70%, less than 50%, less than 40%, less than 30%, less than 20%, more than 10%, 10-45%, or other suitable amount. 
     In scenarios in which display  44  is off for only brief periods of time (e.g., 1 ms at a time or other suitable short interval associated with relatively smaller active ambient light sensor duty cycles), viewer  84  will not be able to perceive any significant dimming or flickering of display  14 . At the same time, ambient light sensor  78  may be able to acquire sufficient data during the display “OFF” intervals. In devices with backlight units  110 , backlight  110  may be turned off in the “OFF” intervals by sending the display control signal to input  116  of backlight unit  110  ( FIG. 5 ). The backlight “OFF” intervals may correspond to off times applied as part of a pulse width modulation power control scheme for the backlight or may be asynchronous with respect to any backlight power pulse width modulation signals that are supplied to the backlight unit. In devices with organic light-emitting diode displays or other displays having pixel-sized light sources such as light-emitting diodes  108 , control circuitry such as common cathode switch  114  may be provided with a control signal on input  112  that temporarily disables the display during the “OFF” intervals. 
     Illustrative steps involved in controlling display  14  so that ambient light sensor  78  can make ambient light sensor measurements without interference from light from display  14  and thereby allow device  10  to make screen brightness adjustments or other take other suitable actions are shown in  FIG. 8 . During the operations of step  124 , device  10  may provide display  14  with display data while periodically disabling the production of light by display  14  so that ambient light sensor data can be acquired without interference from the light of display  14 . In particular, control circuitry  40  may, during the operations of step  126 , provide display data to display driver circuitry  74  over path  50  so that display driver circuitry  74  may load the display data into storage capacitors Cs in display pixels  70  (e.g., using gate driver circuitry  92 , data lines  96 , and gate lines  94 ). The display data loading process may be performed continuously over a series of frames, as indicated by line  128 . 
     While display data is being loaded into display pixels  70  by display driver circuitry  74 , display driver circuitry  74  may produce display light and ambient light sensor control signals (sometimes referred to as display enable/disable signals and/or ambient light sensor disable/enable signals). The control signals may be provided to ambient light sensor  78  over path  50  and to display circuitry such as control line  116  of  FIG. 5  or control line  112  of  FIG. 5 . In particular, a control signal may be provided to display  44  and ambient light sensor  78  (e.g., for a duration of 7 ms) that enables display  44  (i.e., that allows display  44  to produce light) while disabling ambient light sensor  78  (step  130 ), followed by a control signal (e.g., for 1 ms) that disables display  44  (to temporarily prevent display  44  from producing light) while enabling ambient light sensor  78 . As indicated by line  134 , the operations of steps  130  and  134  may be performed continuously, while display  14  is being continuously loaded with data during the operations of step  126 . 
     Ambient light sensor  78  may include photodetector structures for converting incoming ambient light from artificial lighting or the sun into electrical signals. Ambient light sensor  78  or associated control circuitry may digitize the electrical signals to produce digital ambient light sensor data. Digital filtering and other signal processing techniques may be applied to the digital ambient light sensor data, if desired. Periodically (e.g., according to a schedule or whenever sufficient data has been gathered), control circuitry  40  may adjust the brightness of display  14  (step  136 ). Processing may continuously loop through steps  124  and  136 , as indicated by line  138 . 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20130122
Publication Date: 20150505
Grant Date: 20150505
Priority Date: 20121113
Inventors: LAND BRIAN R.
HOLENARSIPUR PRASHANTH S. S.
GILTON TERRY
DRZAIC PAUL S.
YAO WEI H.
Assignee: APPLE INC
CPC Classifications: [{"code": "G09G2310/0237", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0633", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3648", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3648", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/141", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3406", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0626", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05B47/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G3/3225", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3225", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0626", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0633", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2310/0237", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0626", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3225", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2310/0237", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3406", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/141", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05B37/02", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05B47/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K59/13", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 50681049