PATENT DOCUMENT

Publication Number: US-8282261-B2
Application Number: US-47599309-A
Country: US
Kind Code: B2

Title: White point adjustment for multicolor keyboard backlight

Abstract:
There are provided systems, devices and methods for operating a light source to match a white point of ambient light. In one embodiment, a light control system is provided. The light control system includes a light source and a light sensor. The light sensor is configured to operate in conjunction with the light source to provide a visual effect. A controller is electrically coupled to the light source and the light sensor and configured to determine the intensity and color of light to which the light sensor is exposed and dynamically adjust the output of the light source to match the determined intensity and color of light to which the light sensor is exposed.

Claims:
1. A light control system comprising:
 a waveguide defining a passage; 
 a multicolor light source optically coupled to the waveguide; 
 a light sensor optically coupled to the waveguide, configured to sense ambient light and operate in conjunction with the multicolor light source to provide a visual effect; and 
 a controller communicatively coupled to the multicolor light source and the light sensor, wherein 
 the controller determines a white point of the sensed ambient light and dynamically adjusts an output of the multicolor light source based at least partially on the white point of the sensed ambient light; 
 the light sensor receives ambient light through the passage; and 
 the multicolor light source emits the output through the passage. 
 
     
     
       2. The light control system of  claim 1  wherein the multicolor light source comprises a red LED, a green LED and a blue LED. 
     
     
       3. The light control system of  claim 2  wherein:
 the calibration table includes a plurality of entries; and 
 each of the plurality of entries comprises a red, green and blue value. 
 
     
     
       4. The light control system of  claim 2 , wherein the controller employs the white point output to dynamically adjust a non-white output of the multicolor light source. 
     
     
       5. The light control system of  claim 1  wherein:
 the controller references a calibration table to determine a white point output for the light source; and 
 the controller uses the white point output to dynamically adjust the output of the multicolor light source. 
 
     
     
       6. The light control system of  claim 5  wherein the controller actuates the red, green and blue LEDs according to the red, green and blue values retrieved from the calibration table. 
     
     
       7. The light control system of  claim 1  wherein the multicolor light source comprises a top-firing LED. 
     
     
       8. The light control system of  claim 1  wherein the multicolor light source is a side firing LED. 
     
     
       9. The light control system of  claim 1  wherein the multicolor light source is configured to back light a keyboard. 
     
     
       10. The light control system of  claim 9  wherein the light sensor is located under a keycap for a key of the keyboard. 
     
     
       11. The light control system of  claim 1  wherein the light sensor comprises one or more narrowband photosensitive devices. 
     
     
       12. The light control system of  claim 1  wherein the light sensor comprises a broadband photosensitive device.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     The following related patent applications are hereby incorporated by reference in their entirety and for all purposes: U.S. patent application Ser. No. 12/476,000, titled “Keyboard With Increased Control of Backlit Keys” and filed concurrently herewith; U.S. patent application Ser. No. 12/476,040, titled “User Interface Behaviors For Input Device with Individually Controlled Illuminated Input Elements” and filed concurrently herewith; and U.S. patent application Ser. No. 12/476,067, titled “Light Source With Light Sensor” and filed concurrently herewith. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates generally to lighted keyboards and, more particularly, to multicolored backlit keyboards. 
     2. Background Discussion 
     Electronic devices, including desktop computers, notebook computers, personal digital assistants, cell phones and mobile media devices, among others, have become ubiquitous in today&#39;s society. They serve as work tools, communication devices and provide entertainment. As such, they are operated in all types of lighting conditions. For example, electronic devices may be operated on an airplane with limited lighting or outdoors with the sun shining brightly. To help facilitate use of the electronic device regardless of lighting conditions, the keyboards and/or buttons on such devices may be provided with their own lighting. For example, in some instances, the keyboards have been lit by an LED or array of LEDs positioned under the keyboard. In other instances, the keyboards have been backlit by a light source placed under the keys of the keyboard. 
     SUMMARY 
     Certain embodiments may take the form of systems, devices and/or methods for adjusting a white point output of a light source according to ambient lighting conditions in which the light source is operating to provide a visual effect. The light control system includes a light source and a light sensor. In one embodiment, a light control system and light sensor are configured to operate in conjunction with the light source to provide a visual effect. Specifically, a controller is electrically coupled to the light source and the light sensor. The controller is configured to determine the intensity and color of light to which the light sensor is exposed and dynamically adjust the white point of the light output of the light source accordingly. 
     Another embodiment is of a method of operating a backlighting system of a keyboard. The method includes the operation of actuating a light sensor and determining a color of light, sensed by the sensor. A light source is then actuated such that an output of the light source is adjusted based on one or more characteristics of the determined color of sensed light to provide a desired white point for time output. 
     Yet another embodiment may take the form of or include a backlit keyboard. The backlit keyboard includes one or more light sources such as independently operable red LEDs, green LEDs and blue LEDs or multicolor LEDs. Additionally, the keyboard may include one or more light distribution networks to distribute light evenly to one or more keys of the keyboard, the keys may include a transparent portion through which light emitted from the one or more light sources may pass. One or more light sensors configured to sense ambient light may be included in the keyboard. A controller may be configured to determine intensity and color of the sensed ambient light. The controller actuates the red, green and blue LEDs (or multicolor LEDs) via pulse width modulation such that the light emitted from the one or more light sources visible through the transparent portion of the keys provides a determined white point effect relative to the intensity and color of the sensed ambient light. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a chromaticity curve. 
         FIGS. 2A and 2B  illustrate spectral power distribution curves for daylight and incandescent light, respectively. 
         FIG. 3  illustrates a portable computing device. 
         FIG. 4  illustrates a keyboard and mouse for use with the computing device of  FIG. 3 . 
         FIG. 5  is a simplified block diagram of a computer system. 
         FIG. 6  is an expanded view of a device incorporating a light sensor and light source. 
         FIGS. 7A and 7B  illustrate cross-sectional views of alternative embodiments for implementing light sensor and light source devices in the keyboard of  FIG. 4 . 
         FIGS. 8A and 8B  illustrate cross-sectional views of two keys of  FIG. 8B  showing alternative positioning of light sensors for the distributed light embodiment illustrated in  FIG. 8B . 
         FIG. 9  is a block diagram of a sample light control system in accordance with an embodiment. 
         FIG. 10  is a plot illustrating a transition curve for light output relative to a determined level of ambient light. 
         FIG. 11  illustrates an array of light sensors and light sources being controlled by a controller in a master slave configuration. 
         FIG. 12  is a block diagram illustrating a master and slave configuration for operating light sensor and light source arrays in accordance with an embodiment. 
         FIG. 13  illustrates one sample implementation of a light source as a light sensor in accordance with an alternative embodiment. 
         FIG. 14  is a flowchart illustrating a process for adjusting white point. 
     
    
    
     DETAILED DESCRIPTION 
     Generally, one embodiment takes the form of a system for operating one or more light sources to produce a desired visual effect. In one embodiment, the light source(s) backlight one or more keys of a keyboard based on the amount of ambient light to which one or more keys of a keyboard are exposed. The system may be operated by a controller implemented in hardware and/or software. Additionally, the system typically includes one or more light sensors proximately located to the one or more keys of the keyboard so that the light sensors may determine or estimate the light falling on the one or more keys. The light sensor system may be capable of independently sensing different portions of the visible light spectrum, such as the red, green and blue components of the light spectrum. The system may then dynamically select and/or change the color, intensity, saturation or other aspect of the light emitted by the one or more light sources based on the sensed ambient light. Further, the system may include at least one optical system, such as a lightguide, for distributing light from the light sources relatively evenly and uniformly to every key and/or every illuminated part of every key of the keyboard. 
     The number of LEDs used as the light source may be selected to minimize or reduce the amount of power consumed while providing the desired level of brightness, color, saturation, etc. Additionally, perceived brightness and color of the LEDs may be influenced by the optical system distributing radiated light from the LEDs. For example, the optical system may include a lightguide, filters, etc. that may influence perceived color and brightness of the LEDs. 
     In one embodiment, a microcontroller may vary operation of the light sensor and the light source such that the light sensor is not influenced by light emitted by the light sources. That is, the light source is off while the light sensor is on and vice-versa. Thus, the light sensors may sense only ambient light and be used to determine certain operating conditions of the light source. The controller adjusts the output of the light sources according to determined ambient conditions in which the light sources is operating to create the desired visual effect. Specifically, the controller may dynamically adjust the white point of the LEDs&#39; output based on periodical sensing of the R, G, and B components of the ambient light. As used herein, “white point” refers to coordinates in a chromaticity curve that define the color “white.” 
     In particular,  FIG. 1  illustrates a plot  10  of a chromaticity curve  12  from the CIW (Commission International de I&#39;Eclairage). The circumference of the chromaticity curve  12  represents the range of wavelengths in nanometers of visible light and, hence, represents true colors, whereas points contained within the area defined by the chromaticity curve  12  represent a mixture of colors. A Planckian curve  14  is shown within the area defined by the chromaticity curve  12  and corresponds to colors of a black body when heated. The Planckian curve  14  passes through a white region (i.e., the region that includes a combination of all the colors) and, as such, the term “white point” is sometimes generalized as a point along the Planckian curve  14  resulting in either a bluish white point or a yellowish white point. However, for the purposes of the present disclosure, “white point” may also include points that are not on the Planckian curve  14 . For example, in some cases the white point may have a reddish hue, a greenish hue, or a hue resulting from any combination of colors. The perceived white point of light sources may vary depending on the ambient lighting conditions in which the lights source is operating. 
     In accordance with aspects of the present disclosure, the white point of the LEDs may be adjusted to achieve a desired white point based on, or to compensate for, the determined ambient light. For example,  FIG. 2A  illustrates a spectral distribution plot of representing daylight. In the plot, the horizontal axis represents the wavelength of light in nanometers and the vertical axis represents the intensity of light. Generally, the intensity of light may be represented in lumens or, for the purposes of a photosensor, an electrical current may be correlated to lumens and, hence, amperes may be used as units of light intensity. As can be seen, although all wavelengths of the visible spectrum are represented, the wavelengths with the highest intensity are in the blue-green range. In contrast,  FIG. 2B  illustrates a spectral distribution plot representing incandescent lighting. As can be seen, incandescent lighting is weighted towards the yellow and red end of the spectrum. A light source providing a constant color output would appear to have a different white point in daylight and under incandescent lighting because of the different color of light provided by daylight and incandescent lighting. Accordingly, embodiments of the present disclosure provide dynamic white point adjustment to achieve a desired visual effect or compensate for the spectral makeup of ambient light. Various algorithms, including transitions and fade in/out routines based on linear, multi-linear, logarithmic or power laws, may be implemented to accomplish dynamic changes in the white point output based on the ambient light. Examples of the various transition algorithms may be found in U.S. patent application Ser. No. 11/558,376, titled, “Brightness Control of a Status Indicator Light,”, which is incorporated herein by reference in its entirety and for all purposes. 
     Referring to  FIG. 3 , a notebook computer  100  is shown that may be configured to provide white point adjustment to a backlit keyboard  102 . In addition to the keyboard  102 , the notebook computer  100  may include a display  104 , a power button  106 , a track pad  108 , and other functional buttons  110 . The notebook computer  100  may be configured to execute applications and operating system programs. A user may interact with the notebook computer  100  via the keyboard  102 , the track pad  108 , the buttons  110 , or other input devices. Additionally, these and other peripheral devices (not shown) may be communicatively coupled, in a wired and/or wireless fashion, to the notebook computer  100  to allow the user to interact with the computer. For example,  FIG. 4  illustrates a keyboard  112  and a mouse  114  that may be wirelessly communicate with the notebook computer  100  through radio frequency (RF), infrared, Bluetooth, or any other suitable wireless communication protocol. In other embodiments, the keyboard  112 , the mouse  114  and the notebook computer  100  may communicate through wired connections. In other embodiments, the keyboard  112  and mouse  114  may be operatively coupled with a desktop computer. It should be understood that the various embodiments described herein may be physically or logically implemented in the keyboard  102 , keyboard  112 , or any other device or surface to achieve the described functionality. As such, although reference may be made to keyboard  112  it should be understood that the white point, intensity, color, etc. adjustments may be implemented in embodiments other than the keyboard  112 . 
     The keyboard  112  may be a traditional 101/104 key keyboard used in the United States of America, a 102/105 key keyboard commonly used in Europe, or any other suitable keyboard or number pad. The keyboard  112  may have a letter, number, symbol, or function (“indicator” collectively) indicated on a top surface of the key that may be translucent or transparent so that light may pass through the key. Specifically, in one embodiment, indicator may be a clear portion of an otherwise opaque surface of a key so that the indicator acts as a window for light to pass through. In an alternative embodiment the indicator may be printed on a translucent surface. In any case, the keys may be illuminated using a backlight, which will be discussed in detail below, such that a user may easily recognize the different keys, in low light or no light environments. 
     Turning to  FIG. 5 , a simplified block diagram of the notebook computer  100  is illustrated. As can be seen, the notebook computer  100  may include a central processing unit (CPU)  120  that may be configured to process data and execute applications and programs. The CPU  120  may be any suitable microprocessor and may include one or more processing cores. As one example, in some embodiments, the CPU  120  may be a microprocessor manufactured by Intel, such as the 80X86, or Core 2 Duo® processor. 
     The CPU  120  may be communicatively coupled to other component parts of the computer  100 . Specifically, in some embodiments, the CPU  120  may be coupled to other component parts of the computer  100  via one or more busses. In some embodiments, the computer  100  may have multiple busses coupled between the CPU and dedicated chip sets, memory or device expansion slots, for example, such as a Northbridge chip, RAM and/or a PCI graphics board. Busses may also transmit data between chip sets, such as from the Northbridge chip to the Southbridge chip and vice versa. For the sake of simplicity, however, only a single bus  122  is illustrated. 
     Memory  124  may be random access memory (RAM), such as dynamic RAM or static RAM, or any other type of memory including flash memory and read-only memory. Other devices, such as a storage memory  126 , a keyboard  112  and/or mouse  114 , a network interface device  128 , and a monitor  104 , for example, may also be coupled to the bus  122 . The storage memory  126  may be any type of non-volatile computer readable medium such as a hard disk drive, a semiconductor disk drive, a tape drive, flash drive etc. The storage memory  126  may store data, applications, programs, and/or the operating system. The network interface device  128  may allow for the computer system  100  to communicate over a network  130  with other computer systems or devices. 
     The keyboard  112  includes a microcontroller unit (“controller”)  132  that may control the backlighting of the keyboard  112 . The controller  132  may actuate the light source  144  by pulse-width modulating the input to the source. The controller may also activate time light sensor  142  as necessary, often cycling it with the light source in a manner described below with respect to  FIG. 14 . In some embodiments, the controller  132  may be a model 8742 manufactured by Intel Corporation, or a PIC16F84 manufactured by Microchip, Inc. In other embodiments, the controller  132  may be part of a larger integrated circuit, such as a microprocessor capable of running in either master or slave modes. The microcontroller  132  may include hardware and/or software to control actuation of the light sensor  142  and the light source  144 . Additionally, in some embodiments, the controller  132  may be communicatively coupled to the CPU  120  of the computer  100  or another microcontroller of the computer  100 . Further, in yet another embodiment, the controller  132  may be a multi-channel LED driver with precise current setting and matching across all LEDs being driven by the controller. In such an embodiment, the LEDs may be driven with one or more low side field effect transistors. These transistors are typically internal to the controller  132 , but may be external. Further, in this embodiment the resistors  192  are generally unnecessary. Examples of multi-channel LED drivers include the LTC3220 driver, manufactured by Linear Technology and the TLC5940 driver, manufactured by Texas Instruments. It should be understood that other drivers may be used; these two are provided as examples only and are not intended to be limiting. 
     The controller  132  dynamically adjusts the intensity and color output of the light source  144  based on a sensed ambient light and desired white point. In one embodiment, the intensity and color may be adjusted to match the ambient lighting. For example, in one embodiment, if the display  104  of the computer  100  shows a bright green image, such that it is the primary source of light that strikes the keyboard  112 , the backlighting of the keyboard  112  may adjusted to have a greenish hue. Additionally or alternatively, when the keyboard is outside and the sunlight provides the ambient lighting, the white point of the ambient light may be determined and the keyboard  112  may be backlit accordingly to a desired white point. For example, the keyboard  112  may be backlit to provide a soft white hue, yellowish hue, bluish hue or other color depending on the ambient circumstances, for example, if the keyboard is being used in an office setting with a yellowish fluorescent lighting. Additionally, the intensity or brightness of the backlighting may be adjusted based on the brightness of the ambient light. 
     One example of a light sensing and emitting device  140  that may be implemented to backlight the keyboard  112  includes a light sensor  142  and a light source  144 , as generally shown in  FIG. 6 . The light sensor  142  may be a photodiode, a phototransistor, an integrated photodiode and amplifier, or any other suitable photo-sensitive device. In some embodiments, more than one light sensor may be integrated into the device  140 . For example, in one embodiment, multiple narrowband light sensors may be integrated into the device  140  and each light sensor may be sensitive in a different portion of the visible light spectrum. Continuing this example, three narrowband light sensors may be integrated into a single sensor package: a first light sensor may be sensitive to light in the red region of the electromagnetic spectrum; a second light sensor may be sensitive in a blue region of the electromagnetic spectrum; and a third light sensor may be sensitive in the green portion of the electromagnetic spectrum. In other embodiments, one or more broadband light sensors (not shown) may be integrated into the device  140 . The sensing frequencies of each narrowband sensor may also partially overlap, or nearly overlap, that of another narrowband sensor. Each of the broadband light sensors may be sensitive to light throughout the spectrum of visible light and the various ranges of visible light, i.e. red, green and blue ranges, may be filtered out so that a determination may be made as to the color of the ambient light. The determined color of the ambient light is used to dynamically adjust the output of the light source  144  to provide a visual effect. In one embodiment, the white point of light output from the light source  144  may be adjusted to match the ambient lighting conditions. Although the operation and construction of the device  140  is generally discussed herein, a more thorough discussion is provided in U.S. patent application Ser. No. 12/476,067, which is incorporated by reference herein in its entirety. That application also discusses alternative configurations for the device  140 , which likewise may be employed with the methods, techniques and embodiments disclosed herein 
     The light source  144  may be any suitable light emitting element, including incandescent lights, light emitting diodes (LEDs), organic LEDs, solid-state lighting, and so on. The light source  144  may include one or more different colored light emitting elements or light emitting elements that emit light having different wavelengths so that the light source  144  may generate a desired visual effect. In some embodiments, the light source  144  may include a multicolored LED or three LED of different colors. For example, in one embodiment, the light source  144  may be a top firing red, green and blue (RGB) LED that emits light in the red, green and blue portions of the electromagnetic spectrum. The emitted red, green and blue may be combined to achieve a variety of colors and a desired brightness level. Additionally, when the white point output of the light source  144  is adjusted to achieve a desired white point, the output of all other color outputs are adjusted accordingly. 
     The light emitted from the light source  144  and the light sensed by the light sensor  142  passes through an opening  150 , wave guide or otherwise transparent portion of a cover, such as a keycap  152  for a key of the keyboard  112 , for example. In certain embodiments, a wave guide may communicate the emitted light to the opening from the source, as well as communicating sensed light from the opening to the sensor. Thus, a single wave guide may be shared by both the light source  144  and light sensor  142 .  FIG. 7A  illustrates a cross-sectional view of the keyboard  112  with devices  140  located beneath each keycap  152 . Each device  140  may be communicatively coupled to the controller  132  and, hence, each key of the keyboard  112  may be independently backlit according to the ambient light which strikes the particular key. As illustrated, the devices  140  may be located directly under the keycap  152  (as illustrated with respect to keys B and N). Alternatively, the devices  140  may be located some distance from the top of the keycap  152 . For example, the devices  140  may be located on a substrate and may receive and transmit light though the keycaps  152  via a waveguide, lens or other device. Additionally, one or more light sensors  142  and/or light sources  162  may be dedicated to a single key, a particular region, or to the entire keyboard  112 . For example, in one embodiment, a space bar  168  ( FIG. 4 ) may have several light sensors  142  and light sources  144  dedicated to illuminating it so that illumination may vary across the key. This may be useful, for example, when the ambient light that strikes one end of the space bar  168  may be different from the ambient light to which the other end of the space bar  168  is exposed. 
     In other embodiments, a light sensor  142  may be positioned in locations other than the keyboard  112  and, further, the light source  144  may illuminate objects other than keys of the keyboard  112 . As such, it should be understood that although the discussion has been directed toward implementation in a keyboard, other embodiments may include implementations for lighting and/or backlighting other devices, enclosures, surfaces, etc. In one alternative embodiment, a trademark or symbol on a surface of a device, for example, on a surface opposite of the display  104 , may be backlit in accordance with the techniques discussed herein to achieve a desired visual effect. 
     While the light sources and the light sensors have been described as being co-located in the devices  160  and  140 , it should be understood that the light sources  144  and  162  of the device  160  and  140  may be packaged separately and located in different positions from the light sensor  142 . For example,  FIGS. 7A-7B  illustrate embodiments where the light sensors  142  and the light sources  162  may be separated. Specifically, the light sensors  142  may be co-located with the keys while the light sources  162  may be remotely located from the keys or even the keyboard  112 . For example, in  FIG. 8A  the light sensors  142  may be positioned directly under the keycaps  170  of the keys, while the light source  162  may be distributed to the keys via the light distribution network  154 . In another embodiment, light sensors  142  may be positioned beneath the light distribution network  154  while the light source  144  is distributed via the light distribution network  154 . In other embodiments, there may be one or more light sensors  142  for one or several keys. Further, in other embodiments, the light source  144  may be co-located with the keys and the light sensor  142  may be located remotely from the keys, as shown in  FIGS. 8A-8B . In particular,  FIG. 8A  shows the sensor  142  being located directly beneath a key cap  170  and  FIG. 8B  shows the sensor  142  located near the light distribution network  154 . In both  FIGS. 8A and 8B , the light source  162  may be located remotely from the light sensors  142 . Moreover, one or more light sensors  142  may be located near the display  104  ( FIG. 3 ) rather than near or under the keyboard  102 . As such, various different configurations may be provided to achieve a desired light sensitivity and light output. 
       FIG. 10  illustrates block diagram of an embodiment with the light source  144  and the light sensor  142  coupled to the controller  132 . The illustrated light sensor  142  includes a photodiode  182  with an amplifier  184 . A positive and negative rail voltage  186  and  188  may be supplied to the light sensor  142  from the controller  132  for the operation of the amplifier  184 . An output  190  of the light sensor  142  is coupled to an analog-to-digital converter (ADC)  192  that may be part of the controller  132 . The ADC  192  converts analog signals generated by the light sensor  142  into a digital signal to be processed and/or interpreted by the controller  132  or a host. For example, the controller  132  may receive a converted digital signal and determine the brightness of ambient light in which the multicolored light source  144  is operating. The controller  132  may then adjust the output of the light source  144  to achieve a desired visual effect according to ambient light conditions that are determined in real time. Stated differently, the controller  132  may dynamically adjust the light output (both intensity and color) based on current lighting conditions in which a light source is operating. 
     As illustrated, the light source  144  may include multiple LEDs  190 . Specifically, the light source  144  may include a red LED, a green LED and a blue LED. The multiple LEDs  190  may be used together to emit a range of colors and brightness levels. The individual control of the LEDs  190  may be conducted in several different ways. In one embodiment, for example, each anode  192  of the LEDs  190  in the light source  144  may be coupled to a common supply voltage  194 , while each cathode  196  is independently coupled to buffers  198  within the controller  132 . Thus, each of the LEDs  190  may be independently actuated to achieve a desired color and brightness. The controller  132  may be configured to operate the LEDs  190  according to a particular lighting and/or coloring scheme. In one embodiment, the controller  132  may be configured to follow a programmed color and intensity scheme to achieve a desired white point based on the ambient lighting conditions. 
     The desired color and intensity output for particular ambient conditions may be empirically determined. Specifically, the light source  144  and light sensor  142  may be operated in various ambient lighting conditions and the output of the light source  144  may be adjusted under each of the various conditions until a desired white point for the ambient lighting conditions is achieved. The ambient lighting (both color and intensity) may be recorded along with the light output (i.e. the color and intensity) from the light source  144  that provided the desired white point. Specifically, the operating parameters such as input current and/or voltage for each of the LEDs  190  of the light source is recorded for each ambient light condition. Hence, one or several tables may be produced that can be used to determine the output from each light source necessary to achieve a desired white point for different ambient lighting conditions. 
     In addition to adjusting the white point of the light outputted by the source  144 , another possible visual effect that may be produced may be referred to as “constant contrast ratio” illumination. Constant contrast ratio illumination refers to adjusting the brightness of the light source such that, in particular ambient light conditions, the window  150  or part of a key that is illuminated by the light source  144  appears to have the same brightness as a surrounding non-illuminated surface. Thus the illuminated window  150  or surface appears as if it is printed or painted, rather than illuminated. In short, an illuminated key does not appear to glow but it is still colored when the light source is active. 
     In order to achieve this effect, a calibration may be performed to generate a table that represents different possible light outputs that provide a desired visual effect for a variety of ambient light conditions ranging from dark to light. As such the calibration process may begin by measuring ambient light with the ambient light sensor  142 . The color and brightness output by the light source  144  is adjusted to achieve an appropriate appearance for the given conditions. The ambient light conditions and the corresponding output brightness and color are then recorded into a calibration table. Different calibration tables may be recorded for particular sets of ambient light conditions. After calibration, the calibration table may be used for driving the LEDs  190  to a corresponding brightness and color output based on current ambient light as determined by the light sensor  142  and employing one of many possible interpolation algorithms, i.e., linear, logarithmic, exponential, etc., between the points of the calibration table. Where different color LEDs are implemented, each color will have a unique calibration table. Each entry in the calibration table generally includes operating parameters for each of the component elements of the light source  144 , such as the individual red, green and blue diodes. The operating parameters for each entry may include a power input to each LED (such as a pulse-width modulation duration for an input to the LED) that is employed to generate a desired “white” color or white point for the aggregate output of the light source. Further, these scaling parameters may be employed when generating other colors, such that the selected white point effectively adjusts all other colors outputted by the light source  144  as well. 
     Thus, the light source  144  may output a two different wavelengths of light under two different circumstances, but a user may perceive the first and second wavelengths as appearing identical due to changes in ambient light in the different circumstances. For example, the embodiment may be used inside under florescent lights, which are somewhat yellowish. In this case, the embodiment may select a white point having a higher blue content than standard in order to offset the yellow ambient light. Further, when the light source  144  emits a purple light, the source may likewise increase the blue portion of the emitted light to account for the white point selected. Conversely, if the embodiment is operating outside under sunlight, a more yellow white point may be selected to create the visual appearance of “true white” and a purple color emitted by the light source  144  may have more yellow or red than under neutral lighting conditions. 
       FIG. 10  illustrates a plot  200  of a transfer curve for example data points (shown as “x”) of a calibration table. The horizontal axis  202  represents an ambient light level having a scale relative to a maximum level that may be detected. The vertical axis  204  represents the brightness of the light sources relative to a maximum brightness level. Each data point is generated by determining the ambient light level and then determining an appropriate brightness and color level for the light source to achieve the desired effect, such as constant contrast ratio, for example. As the light source  144  may include more than one color and as each color may be independently controlled to achieve a desired color and brightness output, there may be multiple points, each having a unique brightness and color for each level of ambient light. Once sufficient data points have been collected to establish a range of data from a minimum to a maximum ambient light level with each point offset from its neighbors by no more than a maximum allowable interval, the data points may be programmed into a controller so that the controller may operate the light sources according to the desired visual effect based on the determined amount of ambient light. 
     In some embodiments, in order to operate the light source  144  and the light sensor  142  without the light sensor  142  being influenced by the output of the light source  144 , a time division multiplexing (TDM) scheme is implemented by the controller  132 . Additionally, a pulse width modulation (PWM) scheme may be implemented to allow the controller  132  to control the brightness and color output of the light source  144 . 
       FIG. 11  illustrates implementation of an array  230  of light sources  144  and light sensors  142 . The array  230  may be implemented to illuminate and provide visual effects to a larger surface than the embodiments described above. Additionally, the array  230  may provide for a diverse field of visual effects based on the determined ambient light for the illuminated surface. As illustrated, the light sensors  142  and the light source  144  may be located under a single surface  232  that is to be illuminated. For the purposes of this discussion, the top surface of all the keys of the keyboard  112  may be considered a single surface that is to be illuminated by the array  230 . In one embodiment, the surface  232  may include a clear window  234  or multiple windows which may be illuminated or through which the light from the light sources  14  may shine. Additionally, as with other embodiments, other layers  236  may be used to diffuse, mix or shape the light. Specifically, for example, light guides, lenses, filters, holographic diffuses, etc. may be positioned between the surface  232  and the light sources  144  and light sensors  142 . In one embodiment, the array  230  may be controlled by a single controller  132 , as discussed above, to operate the light sources  144  and light sensors  142  in a TDM and PWM manner to achieve a desired effect. In an alternative embodiment, multiple controllers are implemented to operate the array  230 , with each controller controlling a different number of light sources and/or light sensors. 
       FIG. 12  illustrates a block diagram  240  of an embodiment having a master microcontroller  242  configured to control an arbitrary number K slave controllers in a master-slave configuration. For example, a slave controller  244  may control the actuation of N light sources  246  and M light sensors  248 . Additional slave controllers  250  and  252  may control actuation of other arrays of light sources and light sensors (not shown). In some embodiments, the master controller  242  may also control an array of light sources and light sensors. 
     The array  230  may have several different arrangements. For example, in one embodiment, there may be more light sources  246  than light sensors  248  and, as such, a single light sensor may sense ambient light for more than one light source  246 . In other embodiments, there may be the same number of light sensors  248  as light sources  246  or even more light sensors  248  than light source  126 . Additionally, in one embodiment, one controller may be dedicated to operating light sources and another controller may be dedicated to operating the light sensors. 
     The array  230  may be useful for providing a “painted light surface” effect similar to the constant contrast effect previously mentioned and defined. In the painted light surface embodiment, the array  230  of light sources  246  with each coupled to one or more light sensors, which may be integrated with or separate from the light source, may be placed underneath the larger surface and spaced such that the light shines through the surface when the light sources are driven. The control of the light sources  246  may be calibrated so that a surface appears uniformly painted in a range of ambient light conditions, following the process set forth above. The operation of the light sources  246  and the light sensors  248  of the array  230  is similar to that discussed above. In particular, each LED  254  of the light sources  246  may be individually controlled to provide a desired effect. 
     Several different arrangements are possible for arrayed light sensors and light sources. In general, N light sources and M ambient light sensors may be implemented for a particular application, where N and M may or may not be equal. In one embodiment, the anodes  256  of each of the LEDs  254  may be coupled together while the cathodes  258  of the LEDs  252  may be coupled independently to buffers  260  in the controller  244 . Hence, each of the LEDs  252  may be independently controlled by the controller  244 . Additionally, each of the other controllers  250  and  252  may independently control light sources (not shown) to create a desired visual effect. That is, in one embodiment the N light sources  246  and the M light sensors  248  to be controlled by different controllers. 
     It should be noted that certain timing schemes may be employed to operate the light sources  246  and/or light sensors  248 . Such timing schemes, including methods and embodiments for synchronizing operation of the sources and sensors, are disclosed in U.S. patent application Ser. No. 12/476,067, previously incorporated by reference in its entirety. 
     In some embodiments the light sources may also operate as light sensors. As illustrated in  FIG. 13 , a light source  280  may operate as both a light source and a light sensor. The light source  280  may be an LED or a multicolor LED light, such as the RGB LED light source shown. Each LED  282  of the light source  280  may operate as a separate light sensor. Hence, there is no separate light sensor. 
     In order to operate as a light sensor, the light source  280  is biased in a non-conducting direction. That is, each LED  282  may be reverse biased. In order to reverse bias the LEDs  282 , amplifiers  284  are provided in a controller  286  that is configured to control the operation of the light source  280 . The amplifiers  284  are coupled in between an ADC  288  and the light source  280 . Specifically, inverting inputs  290  of the amplifiers  284  are coupled to the anodes  292  of the light source  280  and non-inverting inputs  294  of the amplifiers  284  are coupled to the cathodes  296  of the light source  280 . Each LED  282  of the light source  280  has a leakage current that will dissipate normally either through the diode itself or the large input impedance of the micro-controller in the High-Z state (in the megaOhm range). This increases proportionally to the brightness or the level of ambient light. Thus, if the LEDs  282  are driven during the period T_LED and then reverse biased and sensed during the T_ALS period, the LEDs  282  may operate as both the light sensor and the light source. 
     In order to increase the sensitivity, results from sensing of multiple LEDs (or R, G, and B components) can be added together, either in analog or in the digital domain. That is, light sensed by each of the LED  282  of the light source  280  may be added together to determine the amount of ambient light. The determined amount of ambient light may then be used to determine a corresponding light output for the determined ambient light conditions by referencing a calibration table, as discussed above. Thus, the controller  286  may operate the light source  280  to provide a dynamic, desired light output based on current ambient light conditions. 
       FIG. 14  is a flowchart illustrating a process  300  for adjusting white point. The process  300  begins by detecting the ambient light, as indicated at block  302 . As previously discussed the ambient light detection may include the intensity of the light as well as the different color components of the light. The ambient light is analyzed to determine a white point of the ambient light, as indicated at block  304 . The ambient light white point is used to determine a desired white point output for light sources for the current ambient lighting conditions, as indicated at block  306 . U.S. patent application Ser. No. 12/251,186, titled “Color Correction of Electronic Displays” and filed Oct. 14, 2008, is incorporated herein by reference in its entirety and for all purposes, and describes adjusting for a desired white point. In some embodiments, the desired white point output may be obtained from a transfer curve or table for predetermined desired outputs. Additionally, the desired white point output may be determined through extrapolation or interpolation of data points contained in a transfer curve or table. Adjustment coefficients are calculated such that the desired white point may be achieved under the current ambient lighting conditions, as indicated at block  308 . The coefficients may be representative of an actuation time for an LED relative to a light source actuation time period such as T_LED described above. In another embodiment, the coefficient may represent an actuation time relative to a prior actuation period. In yet another embodiment, the coefficient may represent a relative voltage level used for actuation of the LED. The determined coefficient is applied to the operation of the light sources to achieve a desired white point output, as indicated at block  310 . In a system implementing multiple light sources, the output of each of the light sources is adjusted to account for the adjusted white point, as indicated at block  312 . 
     Although the present embodiment has been described with respect to particular embodiments and methods of operation, it should be understood that changes to the described embodiments and/or methods may be made yet still embraced by alternative embodiments of the invention. For example, certain embodiments may be implemented to light and/or backlight objects other than keys and keyboards, such as status lights, displays, surfaces and so forth. Yet other embodiments may omit or add operations to the methods and processes disclosed herein. Still other embodiments may vary the rates of change of color and/or intensity. Accordingly, the proper scope of the present invention is defined by the claims herein.

Metadata:
Filing Date: 20090601
Publication Date: 20121009
Grant Date: 20121009
Priority Date: 20090601
Inventors: PANCE ALEKSANDAR
KERR DUNCAN
BILBREY BRETT
SLACK BRANDON DEAN
CUTLER REESE T.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01H2219/038", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H2219/039", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H2219/038", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H2219/039", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05B45/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05B45/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0001", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05B47/165", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05B47/165", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 43218991