PATENT DOCUMENT

Publication Number: US-8384003-B2
Application Number: US-201113100757-A
Country: US
Kind Code: B2

Title: Display device control based on integrated ambient light detection and lighting source characteristics

Abstract:
Systems and methods are provided for a display device including one or more methods for modifying the display brightness by automatically adapting to ambient lighting conditions.

Claims:
1. A transmissive display comprising:
 an integrated light source for illuminating the transmissive display by emitting light during a first illumination period, 
 an integrated light sensor for generating a sensor signal based on an amount of light present during a first sensing interval after the first illumination period, and 
 a processor for receiving the sensor signal and controlling the light source during a second illumination period after the sensing interval based at least in part on the sensor signal, wherein the first illumination period includes a power period, during which a controller applies power to the integrated light source, and a delay period, and wherein the delay period is determined based on an illumination decay characteristic of at least one lighting element of the integrated light source. 
 
     
     
       2. The display of  claim 1 , wherein a path for ambient light to reach the integrated light sensor includes a path via the transmissive display. 
     
     
       3. The display of  claim 1 , wherein the at least one lighting element includes a light emitting diode (LED). 
     
     
       4. The display of  claim 3 , wherein the illumination decay characteristic of the LED is based on at least one of physical properties of the LED, an age of the LED, an amount of power applied to the LED during the power period, and a duration of the power period. 
     
     
       5. The display of  claim 1 , wherein the sensing interval begins after the delay period ends. 
     
     
       6. The display of  claim 1 , wherein the delay period associated with the first illumination period is preselected. 
     
     
       7. The display of  claim 1 , wherein the delay period associated with the first illumination period is determined based on an amount of time required after the power period for the illumination level to reach a threshold level. 
     
     
       8. The display of  claim 1 , wherein controlling includes adjusting an amount of power applied to at least one lighting element of the integrated light source to adjust an illumination intensity of the display. 
     
     
       9. The display of  claim 1 , wherein the integrated light source includes an array of lighting elements. 
     
     
       10. A transmissive display comprising:
 an integrated light source for illuminating the transmissive display by emitting light during a first illumination period, 
 an integrated light sensor for generating a sensor signal based on an amount of light present during a first sensing interval after the first illumination period, and 
 a processor for receiving the sensor signal and controlling the light source during a second illumination period after the sensing interval based at least in part on the sensor signal, wherein an illumination period includes a power period, during which a controller applies power to the integrated light source, and a delay period, and wherein controlling includes adjusting a duration of the power period of the second illumination period to adjust an illumination intensity of the display. 
 
     
     
       11. A method for automatically controlling a level of illumination for a transmissive display comprising:
 illuminating the transmissive display by emitting light from a light source during a first illumination period, 
 generating a sensor signal based on an amount of light present at an integrated light sensor during a sensing interval after the first illumination period, and 
 controlling the emitting of light during a second illumination period after the sensing interval based at least in part on the sensor signal, the controlling including adjusting the duration of a power period. 
 
     
     
       12. A display device comprising:
 a transmissive display assembly including: 
 a light source for emitting light over a first period of time to illuminate a portion of the display, wherein the first period of time comprises an illumination decay period during which power is not applied to the light source, 
 a sensor for sensing ambient light over a second period of time, wherein the second period of time begins a predetermined duration of time after the illumination decay period begins, and 
 a processor for controlling the emitting of light from the light source over the first period of time and the sensing of ambient light over the second period of time. 
 
     
     
       13. The device of  claim 12 , wherein the first period of time includes a period when the emitted light is above a predetermined threshold. 
     
     
       14. The device of  claim 13 , wherein the second period of time includes a period when the emitted light is at or below the predetermined threshold. 
     
     
       15. The device of  claim 14 , wherein the duration of a subsequent third period of time is determined, at least in part, by the amount of ambient light sensed during the second period of time. 
     
     
       16. The device of  claim 15 , wherein the duration of the third period of time is determined, at least in part, by the amount of light emitted during the first period of time. 
     
     
       17. The device of  claim 12 , wherein the transmissive display assembly includes of a liquid crystal display. 
     
     
       18. The device of  claim 12 , wherein the light source is comprised of an array of white light emitting diodes. 
     
     
       19. The device of  claim 12 , wherein the light sensor is comprised of at least one of a photodiode and a phototransistor that is sensitive to white light. 
     
     
       20. The device of  claim 12 , wherein the light source is comprised of an array of red, blue, and green light emitting diodes. 
     
     
       21. The device of  claim 20 , wherein the sensor is comprised of at least one of a group of photodiodes and a group of phototransistors that are sensitive to the frequencies of red, blue, and green light emitted by the light emitting diodes. 
     
     
       22. A transmissive display comprising:
 a sensor for generating a sensor signal based on an amount of light present at its receptor, 
 a light source for illuminating the transmissive display, and 
 a processor for repeatedly performing the following i) applying power to the light source during a first period of time, ii) waiting a second period of time for the emitted light intensity from the light source to decay below a light sensor interference level, and iii) sensing the ambient light passing through the transmissive display during a third period of time. 
 
     
     
       23. A method for automatically controlling the level of illumination for a transmissive display based on measured ambient light levels comprising the steps of:
 A. enabling the light source to emit light and measuring the intensity of the light emitted by the light source during a first time period, 
 B. inhibiting the light source from emitting light and measuring the intensity of ambient light during a second time period, 
 C. processing the light measurements from the first time period and second time period to determine the durations of the first time period and second time period for a subsequent iteration of steps A-C, and 
 D. repeating steps A-C at least once.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application No. 12/002,120, filed Dec. 13, 2007, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This invention relates to personal display devices and, more particularly, to controlling the display brightness based on the measured ambient light and lighting source characteristics. 
     The proliferation of compact portable display devices (e.g., portable MP3 players, portable video players, and media capable cellular telephones) has enabled users to interact with such compact portable display devices in environments that have widely varying ambient lighting conditions. Most devices include a display illumination system wherein the brightness level can be varied. Because these devices are often battery-powered and can be used while performing other activities, such as walking or running, it is desirable that the device automatically adjust its display brightness in response to surrounding ambient light conditions to conserve power and to avoid the need for a user to continually manipulate the display brightness manually. 
     One problem with existing display devices is that their ambient light sensors often detect light generated by their own display light sources or backlights which prevents the device from accurately measuring surrounding ambient light conditions. More particularly, existing display backlight controllers do not account for the emitted light from lighting elements after power to these elements is removed, which is caused by certain physical characteristics of the lighting elements. Accordingly, there is a need for accurately measuring varying ambient light conditions without interference from the device&#39;s own display light sources to enable enhanced backlight brightness control. 
     Another problem with existing portable display devices, such as cellular telephones, is that typical ambient light sensors can occupy space within the device&#39;s housing and require an external opening in the housing to enable ambient light detection. A light sensing opening in the housing may expose the device interior to the surrounding environment, increase manufacturing costs, or detract from an otherwise aesthetically pleasing design. Accordingly, there is a need for providing ambient light detection without requiring an additional opening in the device housing to support such detection. 
     SUMMARY 
     The invention, in various embodiments, addresses deficiencies in the prior art by providing systems, methods, and devices that enable a display device to sense the amount of ambient light in the vicinity of the display during an interval when the amount of light emitted by a lighting source of the display is minimized or below an defined threshold. 
     In various aspects, the invention employs light sensors integrated with or positioned within a portion of a transmissive display. A light sensor may include, without limitation, one or more photodiodes and/or phototransistors. The display illumination level may be adjusted automatically based on the amount of ambient light measured by the light sensor. To accurately measure the ambient light without interference from the display illumination, the device processor does not read the sensor values until the display illumination intensity is below a determined light interference level. The light interference level and the time it takes for the illumination intensity to decay to such a level may be determined by the manufacturer of the display. Alternatively, the illumination decay duration can be calculated by the processor using various factors. 
     In one aspect, a transmissive display includes an integrated light source that illuminates the transmissive display by emitting light during a first illumination period. The display also includes an integrated light sensor that generate a sensor signal based on the amount of light present during a first sensing interval after the first illumination period. Also, the display includes a processor that receives the sensor signal and controls the light source during a second illumination period after the sensing interval based at least in part on the sensor signal. 
     In one configuration, the path for the ambient light to reach the light sensor includes a path through the transmissive display. In one feature, an illumination period includes a power period, during which the controller applies power to the integrated light source, and a delay period. The delay period may be determined based on the illumination decay characteristics of at least one lighting element of the integrated light source. At least one lighting element may include a light emitting diode (LED). The illumination decay characteristic of the LED may be based on at least one of the physical properties of the LED, the age of the LED, the amount of power applied to the LED during the power interval, and the duration of the power period. 
     In another configuration, the delay period of the second illumination period is determined based on at least one illumination decay characteristic. The delay period associated with an illumination period may be pre-selected. The delay period associated with an illumination period may be determined based on the amount of time required after the power period for the illumination level to reach a threshold level. 
     In a further configuration, controlling includes adjusting the duration of the power period of the second illumination period to adjust the illumination intensity of the display. The controlling operation may also include adjusting the amount of power applied to at least one lighting element of the integrated light source to adjust the illumination intensity of the display. In one feature, the integrated light source may include an array of lighting elements. 
     In another aspect, a transmissive display includes a sensor for generating a sensor signal based on the amount of light present at its receptor, a light source for illuminating the transmissive display, and a processor. The processor repeatedly performs the following i) applying power to the light source during a first period of time, ii) waiting a second period of time for the emitted light intensity from the light source to decay below a light sensor interference level, and iii) sensing the ambient light passing through the transmissive display during a third period of time. 
     In a further aspect, a display device includes a display assembly consisting of at least three parts: a transmissive display, a light source to illuminate all or part of the display, and a light sensor that can measure the amount of ambient light that passes through the transmissive display into the display device or can measure the amount of light produced by the light source within the display device. 
     In one configuration, the transmissive display is a liquid crystal display. In another configuration, the light source is an array of white light emitting diodes. In a further configuration, the light sensor is an array of one or more photodiodes or phototransistors that measure white light. In another configuration, the light source is an array of red, blue, and green light emitting diodes. In a further configuration, the light sensor is an array of one or more groups of three photodiodes or phototransistors that measure at least the spectrum of red, blue, and green light emitted by the red, blue and green light emitting diodes of the light source. 
     Various advantages and applications using ambient light sensing for display illumination control for a display device in accordance with principles of the present invention are discussed in more detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features of the present invention, its nature and various advantages will become more apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
         FIG. 1A  is a perspective view of a personal display device with an exposed frame assembly according to an illustrative embodiment of the invention; 
         FIG. 1B  is another perspective view of a personal display device according to an illustrative embodiment of the invention; 
         FIG. 2A  shows a simplified functional block diagram of a personal display device according to an illustrative embodiment of the invention; 
         FIG. 2B  shows a functional block diagram of certain product-specific functions that may be included in a personal display device according to an illustrative embodiment of the invention; 
         FIG. 3A  shows a transverse sectional view of a display device including integrated ambient light sensors according to an illustrative embodiment of the invention; 
         FIG. 3B  is a diagram of a LCD-based display system including a backlight, embedded light sensors, and a backlight controller that controls the brightness of the light emitted from the backlight according to an illustrative embodiment of the invention; 
         FIG. 4  is a flow diagram of a process for calculating lighting parameters based on sensed ambient light and characteristics of the device&#39;s display lighting components according to an illustrative embodiment of the invention; and 
         FIG. 5  is a signal timing diagram illustrating the determined timing values based, in part, on the certain device characteristics according to an illustrative embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
       FIG. 1A  is a perspective view of a display device  100  according to an illustrative embodiment of the invention. The display device  100  includes a housing  102 , a first housing portion  104 , a second housing portion  106 , a display  108 , a keypad  110 , a speaker housing aperture  112 , a microphone housing aperture  114 , a headphone jack  116 , and frame sidewall  122 . In certain embodiments, the frame sidewall  122  is the exposed portion of a frame residing within or adjacent to the housing  102  that provides structural support for the media device  100  and various internal components. The housing  102  may also include various gaps  118  that may include openings, separations, vents, or other pathways between elements of the housing  102  which enable the passage of air or sound through the housing  102 . 
     In one embodiment, the housing  102  includes a first housing portion  104  and a second housing portion  106  that are fastened together and/or to the frame sidewall  122  to encase various components of the media device  100 . The housing  102  and its housing portions  104  and  106  may include polymer-based materials that are formed by, for example, injection molding to define the form factor of the media device  100 . In one embodiment, the housing  102  surrounds and/or supports internal components such as, for example, a display lighting element  108  with externally controlled, variable brightness, one or more circuit boards having integrated circuit components, internal radio frequency (RF) circuitry, an internal antenna, a speaker, a microphone, a hard drive, a processor, and other components. Further details regarding certain internal components are discussed herein with respect to  FIG. 2 . The housing  102  provides for mounting of a display  108 , keypad  110 , external jack  116 , data connectors, or other external interface elements. The housing  102  may include one or more housing apertures  112  to facilitate delivery of sound, including voice and music, to a user from a speaker within the housing  102 . The housing  102  may include one or more housing apertures  114  to facilitate the reception of sounds, such as voice, for an internal microphone from a display device user. 
     The display device  100  may include a personal media device and/or wireless communications device such as a cellular telephone, satellite telephone, cordless telephone, personal digital assistant (PDA), pager, portable computer, or any other device capable of wireless communications. In certain embodiments, the display device can include any computing device, dedicated processing device, television, display unit, or like device that includes a display element for the display of information. 
     The display device  100  may also be integrated within the packaging of other devices or structures such a vehicle, video game system, appliance, clothing, helmet, glasses, wearable apparel, stereo system, entertainment system, or other portable devices. In certain embodiments, device  100  may be docked or connected to a wireless enabling accessory system (e.g., a wi-fi docking system) that provides the display device  100  with short-range communicating functionality. Alternative types of display devices  100  may include, for example, a media player such as an iPod or iPhone that are made available by Apple Inc., of Cupertino, Calif., pocket-sized personal computers such as an iPAQ Pocket PC available by Hewlett Packard Inc., of Palo Alto, Calif. and any other device capable of communicating wirelessly (with or without the aid of a wireless enabling accessory system). 
     In certain embodiments, the display device  100  may synchronize with, for example, a remote computing system or server to receive media (using either wireless or wireline communications paths). Wireless syncing enables the display device  100  to transmit and receive media and data without requiring a wired connection. Media may include, without limitation, sound or audio files, music, video, multi-media, and digital data, in streaming and/or discrete (e.g., files and packets) formats. 
     During synchronization, a host system may provide media to a client system or software application embedded within the display device  100 . In certain embodiments, media and/or data is “downloaded” to the display device  100 . In other embodiments, the display device  100  is capable of uploading media to a remote host or other client system. Further details regarding the capabilities of certain embodiments of the display device  100  are provided in U.S. patent application Ser. No. 10/423,490, filed on Apr. 25, 2003, the entire contents of which are incorporated herein by reference. 
       FIG. 1B  is another perspective view of a display device  100  according to an illustrative embodiment of the invention. In this embodiment, as opposed to the embodiment of  FIG. 1A , the media device&#39;s frame and/or the frame&#39;s sidewalls are not exposed to an external surface of the device. However, in certain embodiments, the frame is connected internally with at least a portion of one of the first housing portion  104  or the second housing portion  106 . Display devices of this type may include touchscreen remote controls, such as a Pronto made available by Royal Philips Electronics of the Netherlands or a handheld GPS receivers made available by Garmin International, Inc. of Olathe, Kans. In certain embodiments, the display  108  includes a graphical user interface (GUI) to enable a user to interact with the display device  100 . 
       FIG. 2A  shows a simplified functional block diagram of the display device  100  according to an illustrative embodiment of the invention. The display device  200  may include a processor  202 , display  210 , bus  218 , memory  220 , display lighting  234 , light sensors  236 , and product-specific functional blocks  240 . 
       FIG. 2B  shows an embodiment of the product-specific functional blocks  240  that includes the following elements: storage device  204 , user interface  208 , CODEC  212 , communications circuitry  322 , a speaker or transducer  224 , a microphone  226 , a GPS receiver  242  and an infrared transmission device for the control of consumer electronics  244 . Processor  202  may control the operation of many functions and other circuitry included in display device  200 . Processor  202  may drive display  210  and control the display lighting  234  brightness level. 
     Storage device  204  may store media (e.g., music and video files), software (e.g., for implanting functions on device  200 , preference information (e.g., media playback preferences), lifestyle information (e.g., food preferences), exercise information (e.g., information obtained by exercise monitoring equipment), transaction information (e.g., information such as credit card information), wireless connection information (e.g., information that may enable media device to establish wireless communication with another device), subscription information (e.g., information that keeps tracks of podcasts or television shows or other media a user subscribes to), and any other suitable data. Storage device  204  may include one more storage mediums, including for example, a hard-drive, permanent memory such as ROM, semi-permanent memory such as RAM, or cache. 
     Memory  220  may include one or more different types of memory which may be used for performing device functions. For example, memory  220  may include cache, ROM, and/or RAM. Bus  218  may provide a data transfer path for transferring data to, from, or between at least storage device  204 , memory  220 , and processor  202 . Coder/decoder (CODEC)  212  may be included to convert digital audio signals into an analog signal for driving the speaker  224  to produce sound including voice, music, and other like audio. The CODEC  212  may also convert audio inputs from the microphone  226  into digital audio signals. 
     User interface  208  may allow a user to interact with the display device  200 . For example, the user input device  208  can take a variety of forms, such as a button, keypad, dial, a click wheel, or a touch screen. Communications circuitry  222  may include circuitry for wireless communication (e.g., short-range and/or long range communication). For example, the wireless communication circuitry may be wi-fi enabling circuitry that permits wireless communication according to one of the 802.11 standards. Other wireless network protocols standards could also be used, either in alternative to the identified protocols or in addition to the identified protocol. Other network standards may include Bluetooth, the Global System for Mobile Communications (GSM), and code division multiple access (CDMA) based wireless protocols. Communications circuitry  222  may also include circuitry that enables device  200  to be electrically coupled to another device (e.g., a computer or an accessory device) and communicate with that other device. 
     In one embodiment, the display device  200  may be a portable computing device dedicated to processing media such as audio and video. For example, display device  200  may be a media player (e.g., MP3 player), a game player, a remote controller, a portable communication device, a remote ordering interface, an audio tour player, or other suitable personal device. The display device  200  may be battery-operated and highly portable so as to allow a user to listen to music, play games or video, record video or take pictures, communicate with others, and/or control other devices. In addition, the display device  200  may be sized such that it fits relatively easily into a pocket or hand of the user. By being hand held, the display device  200  (or display device  100  shown in  FIG. 1A  or  1 B) is relatively small and easily handled and utilized by its user and thus may be taken practically anywhere the user travels. 
     As discussed previously, the relatively small form factor of the display device  200 , in certain embodiments, enables a user operate the device in environments with widely varying ambient lighting conditions, e.g., from total darkness to full, direct sunlight. Accordingly, embodiments of the invention provide for improved techniques of sensing such changes in ambient lighting conditions to enable a user to view the information presented on the display  210  of the display device  200  by controlling the device&#39;s display lighting  234 . 
       FIG. 3A  shows a transverse sectional view of a display device  300  including a display  308 , a display lighting element  334  of variable brightness and internally-housed and/or integrated light sensors  336  according to an illustrative embodiment of the invention. The display device  300  may include an upper housing  306 . The main structural frame  304  may be secured to the lower housing  310 , which may be fabricated from a die-castable material using a die-casting process. The structural frame  304  may support a printed circuit board  320 , the display lighting elements  334 , the light sensors  336 , and/or the display  308 . The printed circuit board may include a processor, memory, and other product-specific functional elements such as the functional blocks described in  FIG. 3A . 
     In certain embodiments, the display  308  includes a liquid crystal display (LCD). The most commonly used types of LCDs in use today include active matrix thin film transistor LCDs (TFT LCD). A LCD may include a two-dimensional regular rectangular array of picture elements or “pixels” organized into rows and columns. In a color LCD, each pixel may include three sub-pixels, one for each of the primary colors, e.g., red, blue, and green. A LCD is a transmissive display, meaning that each pixel (or sub-pixel in the case of a color display) filters some or all of the light passing through it from behind. In a monochromatic display, a pixel that is fully ON is the color of the display lighting elements  334 . 
     In certain instances, the desired color of the display lighting elements  334  is a true white color or as close to true white as can be produced. If a pixel is partially ON, that pixel will be gray. If a pixel is fully OFF, that pixel will be black because it does not allow any light to pass through it. In a color display, each of the sub-pixels is set at a level so that the combined light produces the desired tone. For example, if yellow is desired, the red and green sub-pixels are set to be fully ON and the blue sub-pixel is set to be fully OFF. In certain embodiments, the light passes through an LCD in both directions. 
     In certain instances, a LCD can be usable without display lighting elements  334  by the inclusion of a reflector element behind the display. Thus, the information present by the display is viewable only by whatever ambient light is reflected through the display to the viewer. In certain embodiments, as illustrated in  FIG. 3 , display lighting elements  334  are included with the display  304  to allow for viewing in varying ambient lighting conditions. The display lighting element  334  may include an array of one or more light emitting diodes (LEDs), cold-cathode fluorescent lamps (CCFLs), or like lighting elements. LEDs are semiconductor devices that can be manufactured to produce a variety of different colors of light while consuming relatively little power or producing relatively little heat. In certain embodiments, the LCD display may include a backlight that can be one or more CCFLs mounted along the edges of the LCD or spaced uniformly over the back of the display, or it can be a string of light-emitting diodes (LEDs) arranged along the edges of the LCD or as a matrix over the back of the LCD assembly. 
     A LCD may include one or more arrays of LEDs. The LED arrays include white colored LEDs or may be a combination of red, blue, and green LEDs utilized together to produce a white light. In certain embodiments, the display lighting elements  334  may produce varying degrees of brightness under external control by, for example, the processor  202 . This may be accomplished by: 1) varying the amount of power that is input into the display lighting elements  334  (known as amplitude modulation), 2) varying the amount of time that power is applied to the lighting elements (known as pulse width modulation), and/or 3) in the case where the display lighting elements  334  is comprised of more than one individually controllable lighting element, applying power to varying numbers of the lighting elements to modulate or adjust the lighting brightness level. Under certain conditions, due to the physical properties of the semi-conductor material of LEDs, there is often a measurable amount of light emitted from the display lighting elements  334  for a period of time after the external control, voltage, and/or power applied to the elements  334  has been turned off and/or removed. 
     The display  308  may include, without limitation, one or more of a transreflective LCD, active-matrix LCD (AMLCD), anisotropic conductive film, a cathode ray tube, a digital light processing (DLP) display, a field emission display (FED), liquid crystal on silicon (LCOS), organic light-emitting diode (OLED), plasma display panel (PDP), surface-conduction electron-emitter display (SED), and a vacuum fluorescent display (VFD). The display  308  may include certain categories of display devices such as, without limitation, a segment LCD, a dot matrix LCD, a graphic LCD, passive matrix LCD, and active matrix LCD. The display  308  may include a controller such as, without limitation, as PAN (hardware scrolling) control, frequency rate control (FRC), and palette color lookup table control. 
     In certain embodiments, the light sensors  336  may include one or more photodiodes, phototransistors, and/or like light sensing elements. One or more of these sensors  336  may be used to measure a broad spectrum of light. In one embodiment, at least one sensor  336  is tuned to be responsive to a narrow spectrum of light. In another embodiment, each of a plurality of sensors  336  is tuned to a different spectrum of light. For example, a photodiode may be tuned to be most responsive to the frequencies of light that are produced by the blue LEDs that are part of the display lighting elements  334 . Therefore, a set of three photodiodes, one tuned to red, one to blue, and one to green, may be used to measure the amount of each light component being produced by a LED-based display lighting element  334 . 
       FIG. 3B  is a diagram of a color LCD-based display system  350  including a backlight  352 , embedded light sensors  358 , and a backlight controller  356  to control the brightness of the light  386  emitted from the backlight  352  according to an illustrative embodiment of the invention. The backlight  352  may include one or more lighting elements  354 . In certain embodiments, the backlight  352  may include a semi-conductive substrate on which the one or more lighting elements are embedded and/or attached. The system  350  may also include a sandwiched structure  386  having a first polarizing filter  372 , a first glass substrate  374 , one or more first transparent electrodes  376 , a first alignment layer  378 , liquid crystals  380 , a spacer  364 , a second alignment layer  366 , one or more second transparent electrodes  368 , a color filter layer  370 , a second glass substrate  362 , and a second polarizing filter  360 . 
     In one embodiment, one or more light sensors  358  are integrated with the R, G, and B filters of the color filter layer  370 . The one or more light sensors  358  may be distributed throughout the color filter layer  370 . The distribution may be random or predetermined to maximize light detection and/or minimize any impact on the resolution of the system  352 . In other embodiments, the light sensors  358  may be included in any one of the various layers of the system  352 . 
     In operation, the LCD-based display system  350 , using the controller  356 , controls the amount of light  386  emitted from the backlight  352  based on the measured ambient light detected by one or more light sensors  358 . The controller  356  may be the processor  202  of  FIG. 2  or may be another processor that is dedicated to the system  350 . In one embodiment, the controller  352  is in electrical communication with the backlight  352  to control the power applied to the lighting elements  354 . In another embodiment, the controller  352  is in electrical communication with one or more light sensors  358  via the connection  382  to enable the reception of light intensity information from the one or more light sensors  358 . In one embodiment, an LED may also function as a light sensor. 
     The first and second polarizing filters  372  and  360  may control the light entering and leaving the sandwiched LCD structure  386  respectively. The first and second glass substrates  374  and  362  may provide electrical and physical insulation. The first and second transparent electrode layers  376  and  368  include electrodes that drive the LCD and include highly transparent material to minimize possible interference with image quality. The first and second alignment layers  378  and  366  may include films that are used to align the molecules of the liquid crystal  380  in a fixed direction. The spacer  364  maintains a uniform distance between the alignment layers  378  and  366 , and the glass substrates  374  and  362 . The color filter layer  370  includes a plurality of red (R), green (G), and blue (B) filters that enable to display of color images. In one embodiment, the backlight  352  emits light  386 , over a variable interval and/or at a variable intensity, into the sandwiched structure  386  to control the light intensity observed by a user&#39;s eye  384 . 
     In certain embodiment, one or more light sensors  358  may be located at the same layer and/or plane as the lighting elements  354 . The one or more light sensors  358  may be dispersed among and/or interspersed with the one or more lighting elements  354  of the backlight  352 . In one embodiment, the one or more light sensors  358  and/or lighting elements  354  are micromachined semi-conductive components in communication with a substrate of the backlight  352 . The substrate may be planar and correspond with a portion of the planar surface of the polarizing filter  372 . 
     In one embodiment, the controller  356  may automatically adjust the light output of one or more lighting elements  354  such that the illumination intensity of the system  350  is at an predetermined level above the ambient light intensity as measured by one or more light sensors  358 . In other words, as the surrounding ambient light intensity varies, the controller  356  can vary the system  350  display illumination intensity level to maintain a predetermined difference in intensity level between surround light and the emitted light from the system  350 . 
       FIG. 4  is a flow diagram of a process  400  for calculating the appropriate lighting parameters based on sensed ambient light and characteristics of the device&#39;s display lighting elements and/or components according to an illustrative embodiment of the invention. In certain embodiments, when the display device  100  is in an operating mode where the display  108  should be illuminated (e.g., the user has pressed a button  110  or touched the touchscreen  322 ), the processor  202  may activate and/or enable the display lighting  234  [Step  401 ]. The processor  202  may then retrieve from memory  220  or the storage device  204  a value for the amount of time or duration that the display lighting remains enabled, named the duty_cycle_on counter value in  FIG. 4 . The duty_cycle_on value may be calculated either by device default or user preference settings or by a previous iteration, cycle, or loop through the process  400 . The processor  202  may use the duty_cycle_on value as an input to a timer and/or counter application to enable the timer to begin counting towards zero [Step  402 ]. The process  400  continues to apply power to the display lighting  234  until the duty_cycle_on timer reaches zero [Step  403 ]. After the duty_cycle_on time reaches zero [Step  403 ], the power period ends and the processor  202  removes power from the display lighting  234  or backlight [Step  404 ]. 
     The processor  202  may then retrieve from memory  220  or the storage device  204  via the bus  218 , a value for the amount of time for which no power is to be applied to the display lighting  234 , known as the duty_cycle_off counter value. The duty_cycle_off value may be calculated either by device default or user preference settings or by a previous iteration, cycle, or loop through the process  400 . The duty_cycle_off value may be loaded into a timer application of, for example, the processor  202  to enable the timer application to begin counting towards zero [Step  409 ]. The processor  202  may retrieve from memory  220  or the storage device  204  a value for the amount of time to delay the ambient light sensing after power is removed from the display lighting  234  (e.g., after the power period), known as the backlight_decay counter value. 
     The backlight_decay value may be based on a predetermined light emission decay characteristic of an lighting element  334 , e.g., LED. In one embodiment, the light emission decay characteristic may include a non-linear decay constant. The decay constant may be based on the physical properties of one or more light elements  334 . For example, a semi-conductor device or like device may continue to emit light energy after its power source is removed for an interval or period of time that decays at a linear or non-linear rate. Alternatively, the light emission decay characteristic may measured and/or calculated dynamically based upon the display lighting element  334  characteristics and the duty_cycle_on and duty_cycle_off values from a previous loop through the process  400 . In one embodiment, the combined durations of the duty_cycle_on period and the backlight_decay period is duration of the illumination period. 
     The backlight_decay value may be input into a timer application of the processor  202  to enable the timer application to begin counting, for example, towards zero [Step  405 ]. The process  400  delays measuring ambient light until the backlight_decay timer reaches zero [Step  406 ]. After the backlight_decay interval is completed, the processor  202  then samples and/or measures the ambient light level from one or more light sensor elements  336  [Step  407 ]. In one embodiment, the sensing occurs during a sensing period. Based on the available ambient light measured by the sensor elements  336 , the characteristics of the display lighting elements  334 , the device default, and/or user-preferred display lighting level, the processor  202  may calculate new values for the duty_cycle_on, duty_cycle_off, and backlight_decay counter values for a subsequent lighting period [Step  408 ]. The process  400  waits until the duty_cycle_off timer reaches zero [Step  410 ]. Alternatively, instead of counting down, the processor may count up to a counter value. After the duty_cycle_off timer reaches zero [Step  410 ], the processor  202  may store the new calculated values for the duty_cycle_on, duty_cycle_off, and backlight_decay timer values into memory  220  or the storage device  204  via the bus  218  for use in the next loop, cycle, or iteration of the process  400  [Step  411 ]. If the processor  202  determines that display lighting is still needed, the process  400  repeats process  400  continuously by returning to Step  401 . 
       FIG. 5  is a signal timing diagram  500  illustrating the relationship between the determined timing values and the device element characteristics to be accounted for according to an illustrative embodiment of the invention. In certain embodiments, the processor  202  controls the display lighting via a lighting control signal that is applied, for example, to one or more lighting elements  234  or  334 . 
     The brightness of the display lighting elements  234  may be controlled and modulated using a pulse-width modulation (PWM) technique that includes a variable duty cycle. In one embodiment, there is a pair of on/off values, known as the duty_cycle_on  501  and duty_cycle_off  502  values that are also used in process  400 . To make the display lighting elements  234  brighter, the duty_cycle_on  501  duration value may be increased while the duty_cycle_off  502  duration value may be decreased. To make the display lighting elements  234  dimmer, the duty_cycle_off  501  duration value may be increased while the duty_cycle_on  502  duration value may be decreased. 
     Depending on the physical characteristics of the display lighting elements  234  or  334 , the amount of time it takes for the display lighting elements  234  to stop emitting light above a particular threshold, known as the backlight_decay time  503 , may vary based on the duty_cycle_on  501  time, the duty_cycle_off  502  time, the ambient temperature, the age of the display lighting elements  234 , the short-term and long-term cumulative power use of the display lighting elements  234 , among other factors. The process  400  may take one or more of these factors into account to determine when a sampling, sensing, detection, and/or measuring window  504  of the light sensors  236  includes the actual ambient light conditions, and not any remaining light generated by the display lighting elements  234  or  334 . 
     It will be apparent to those of ordinary skill in the art that methods involved in the present invention may be embodied in a computer program product that includes a computer usable and/or readable medium. For example, such a computer usable medium may consist of a read only memory device, such as a CD ROM disk or conventional ROM devices, or a random access memory, such as a hard drive device or a computer diskette, or flash memory device having a computer readable program code stored thereon. 
     It is understood that the various features, elements, or processes of the foregoing figures and description are interchangeable or combinable to realize or practice the invention describe herein. Those skilled in the art will appreciate that the invention can be practiced by other than the described embodiments, which are presented for purposes of illustration rather than of limitation, and the invention is limited only by the claims which follow.

Metadata:
Filing Date: 20110504
Publication Date: 20130226
Grant Date: 20130226
Priority Date: 20071213
Inventors: GARDNER, JR. WILLIAM BRYSON
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/041", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3406", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2360/145", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/064", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/145", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3413", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/064", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/36", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/043", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/36", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/043", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3406", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3413", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/36", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G3/3225", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05B47/165", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05B47/165", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 40149665