Abstract:
A system having a light guide adapted to collect light from a light source, a light detector attached to the light guide, a controller electrically connected to an output of the light detector, and a driver for driving the light source detachably connected to an output of the controller. The driver includes a memory that stores a calibration value for the light source.

Description:
FIELD OF THE INVENTION 
     The present disclosure relates generally to a method and system for a portable device that measures and adjusts the output of light-emitting diodes (LEDs). 
     BACKGROUND 
     An LED is a semiconductor based light source including a semiconductor diode and optionally photoluminescent phosphor material, also referred to herein as phosphor, for generating a light at a specified wavelength or a range of wavelengths. LEDs are traditionally used for indicator lamps and are increasingly used for displays, such as liquid-crystal displays (LCDs). 
     An LED emits light when a voltage is applied across a p-n junction formed by oppositely doped semiconductor compound layers. The wavelength of the light generated by the p-n junction depends on the band gaps of the semiconductor layers used to fabricating an active layer within the p-n junction of the LED. Thus, a specific p-n junction will emit only a narrow band of wavelengths. Additional phosphor materials are included in some LEDs as a coating over the LED. Light generated by the p-n junction that strikes the phosphors is converted up or down by the phosphors to a different wavelength. Thus, in addition to the wavelength of light emitted by the p-n junction, the LED emits other wavelengths from the phosphors. A typical white light LED, for example has a p-n junction that emits blue light. A portion of the blue light is converted to red and green light by the phosphors so that the total light output by the LED appears white. 
     As the LED is subjected to repeated use, the p-n junction within the LED begins to decay. As a result, over time the light intensity of the LED will drop. Further, the phosphors also decay at different rates with respect to each other and the p-n junction. Thus, the color of an LED with phosphors will also change with time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  is a high level functional block diagram of components of a light-adjusting system according to an embodiment. 
         FIGS. 2 and 3  are high level perspective views of two LCD displays incorporating the light-adjusting system according to an embodiment; and 
         FIG. 4  is a flowchart of a method of using the system of  FIG. 1  according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     It is understood that the following disclosure provides many different embodiments, or examples, for implementing different features of the present disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     Various embodiments of the present disclosure pertain to a system that detects and adjusts the light output of an electrical device that has light source. Some embodiments of the present disclosure include a hand-held, portable device. 
       FIG. 1  is a diagram of a light-adjusting system  100 . The light-adjusting system  100  comprises a portable light-detecting portion  110 . This portable light-detecting portion  110  is designed to measure and detect the intensity value of light output from a light source  115  of an electrical device  117 . The portable light-detecting portion  110  includes a light collecting and guiding portion  120  and a light detector  130 . The light collecting and guiding portion  120  collects the light output from the light source  115  at a particular location of a target electrical device, for example, the display screen of a liquid crystal display. The light collecting and guiding portion  120  guides the light to the light detector  130 . In various embodiments, the light collecting and guiding portion  120  is a known light guiding mechanism such as an optical fiber, a light pipe, a covered trench in a substrate. In various embodiments, the light detector  130  detects various light properties, such as intensity, color, color temperature or spectral distribution either separately or simultaneously. 
     The light detector  130  includes a photo sensor or photometer. In various embodiments, the photo sensor is a charge-coupled device, a complementary metal oxide semiconductor (CMOS) sensor, a phototransistor, a photoresister, a photovoltaic cell such as a solar cell or an LED configured to operate as a light detector. In some embodiments, a single collecting and guiding portion  120  is connected to a single light detector  130 . In some embodiments, more than one light collecting and guiding portion  120  is connected to a single light detector  130 . In some embodiments, light collecting and guiding portion  120  is connected to more than one light detector  130 . A controller  140  is connected to the light detector  130 . Light output information detected by the light detector  130  is sent to the controller  140 . 
     The light-adjusting system  100  further comprises a driver  150 . The controller  140  analyzes the light output information and controls the driver  150  that controls the power being supplied to the light source  115 . In some embodiments, the controller  140  increases the power supplied to the light source  115  by the driver  150  if the measured light intensity is lower than a predetermined threshold value. The controller  140  decreases the power supplied to the light source  115  by the driver  150  if the measured light intensity is greater than the predetermined threshold value. Thus, the light output by the light source  115  substantially matches the predetermined threshold value when controlled by the controller  140 . 
     In some embodiments, the controller  140  controls the color output by the light source  115  to be a predetermined color value rather than a predetermined intensity. For example, if the light source comprises red, green and blue LEDs, the ratios of power supplied to each color LED is adjusted separately by the controller  140  using the driver  150 . Thus, the color of the output light is adjusted to match the predetermined color value. 
     The light-adjusting system  100  further comprises a connection  160 . The connection  160  connects the driver  150  is to the controller  140 . Based on instructions received from the controller  140 , the driver  150  adjusts the electrical power supplied to the light source  115 . One example of such light a source would be an LED of an LED backlighting plate in an LCD display device. 
     In some embodiments, the light source  115  is an LED. In some embodiments, the light source  115  is an incandescent bulb, a florescent tube, compact florescent bulb, electroluminescent emitter or an organic LED. In other embodiments the light source  115  is any combination of one or more of the above light sources. 
     The driver  150  is part of electrical device  117 . In some embodiments, the driver  150  is external to the electrical device  117 . 
     The driver  150  has a memory  170  that stores a calibration value for the power for the light source  115  that is determined by the controller  140 . If the controller  140  is controlling the driver  150 , the controller updates the memory  170  with new values based on the controlled power supplied to the light source  115 . If the driver  150  is disconnected from the controller  140 , the driver  150  will continue to supply the correct power to the light source  115  based on the values stored in the memory  170 . 
     In some embodiments, the controller  140  is placed in the driver  150  rather than the portable light-detecting portion  110 . Further, the connection  160  sends the signal output from the light detector  130  to the controller  140 . If the light detector  130  is connected to the controller  140  and the controller is controlling the driver  150 , the controller updates the memory  170  with new values based on the controlled power supplied to the light source  115 . If the controller  140  is disconnected from the light detector  130 , the driver  150  continues to supply the correct power to the light source  115  based on the values stored in the memory  170 . 
       FIGS. 2 and 3  are high level perspective views of the light-adjusting device  110  used to adjust a backlight output of LED display devices  200  and  300  respectively. LED display devices  200  and  300  are LCD display panels that use LEDs as light sources for backlighting. 
     With regard to  FIG. 2 , LED display device  200  is an LCD display panel with direct-type LED backlighting. In an LCD display device  200  with direct-type LED backlighting, LEDs  205  are distributed on an LED backlighting plate  220 . The LED backlighting plate  220  is positioned behind an LCD display panel, such as display panel  240 . When the LCD display device  200 , such as, for example, an LCD television, is turned on, the LEDs on the LED backlighting panel  220  create backlighting and the backlight is visible by a viewer from the front of the LCD device on the display panel  240 . There are several other panels placed between the LED backlighting panel  220  and the LCD display panel  240 , such as a diffuser plate  230 . 
     The portable light-detecting portion  110  is used to measure the LED light output in one area of the display surface for example area  250  of the LCD display panel  240 . The portable light-detecting portion  110  measures at least a portion of the surface of the display panel  240 . In an embodiment, portable light-detecting portion  110  to measures a specific area of the display surface that correlates to a particular light source. The portion of the display surface that most accurately reflects the light output of a particular LED is the portion of the LCD display surface that is directly in front of that LED. The LED  210  correlates with area  250 . 
     In some embodiments, the portable light-detecting portion  110  is not required to be in direct physical contact with the target portion of the LCD display panel surface  240  and only needs to be sufficiently close to the target surface so that the light-output is detected and accurately measured. 
     The portable light-detecting portion  110  is connected to the driver  150  in the LCD display device  200  via the connection  160 . In some embodiments, the connection  160  is an electrical or optical transmission line, for example an electrical cable, a fiber optic cable or a light guide. In some embodiments, the connection  160  is a wireless connection, for example a radio link or a free space infrared link or BLUETOOTH link. To calibrate the light output of LED  210 , the portable light-detecting portion  110  measures the light output by the LED  210  at area  250 . Based on the measured light output, the portable light-detecting portion  110  instructs the driver  150  to adjust an amount of electrical power or current or voltage to the corresponding LED  210  in the backlighting plate  220  of the LCD display device  200 . 
     The above measurement and adjustment continues until the light measured at area  250  reaches a predetermined threshold value stored in the controller  140  ( FIG. 1 ) of light-detecting portion  110 . The driver  150  stores a calibration value for the LED  210  in the memory  170  based on electrical power required to produce the predetermined threshold value. The stored calibration value for the LED  210  is used to calibrate the light output of LED  210  against other LEDs  205  in the backlighting plate  220  when the portable light-detecting portion  110  is not controlling the LED  210 . 
     In the same manner, each of the LEDs  205  in the backlighting plate  220  are calibrated by the light-adjusting system  100 , and a corresponding calibration value for each LED is stored in the memory  170 . 
     In some embodiments, the predetermined threshold value is a preset value, for example a factory setting. The use of light-adjusting system  100  on the display device  200  with a preset factory value adjusts each LED to output an intensity that substantially matches the original factory value. Thus, in some cases an old display is adjusted to be as bright as a new display. In some embodiments, the predetermined threshold value is set to be the light intensity measured one of the LEDs  205  in the display device  200 . Thus, in some embodiments, all of the LEDs in the display device  200  will be adjusted to be as bright as the one LED, and the display device  200  has uniform brightness. In some embodiments, the predetermined threshold value is set to be the light intensity measured for one of the LEDs  205  in a first display device  200 . The light-adjusting system  100  is then used to calibrate a second display device  200 . Thus, all of the LEDs in the second display device are adjusted to be as bright as the first display device  200 , and the display devices have uniform brightness. 
       FIG. 3  is an edge-type LED backlighting display  300  in conjunction with which light-adjusting system  100  is used. Unlike panels with direct-type LED backlighting (in which LEDs are placed on a panel behind the display panel), display panels with edge-type LED backlighting comprise LEDs placed on one or more elongated bars that are positioned on the edges of the display panel. 
     LED backlighting display  300  has a number of LEDs  305  that are placed on an elongated LED light bar  320 . In some embodiments, the LED light bar  320  is placed on the left side of the display panel  340 . Display panels with edge-type LED backlighting are not limited to this particular configuration. In various embodiments, LED light bars  310  are placed at the left, the right, the top, the bottom or any combination of the left, the right, the top or the bottom edges of the display panel  340 . In various embodiments, more than one LED light bar  310  is placed on an edge of the display panel  340 . 
     The portable light-detecting portion  110  is connected to the driver  150  in the LCD display device  300  via the connection  160 . In some embodiments, the connection  160  is an electrical or optical transmission line. In some embodiments, the connection  160  is a wireless connection. To calibrate the light output of LED  305 , the portable light-detecting portion  110  measures the light output by the LED  310  at area  350 . 
     Based on the measured light output, the portable light-detecting portion  110  instructs the driver  150  to adjust an amount of electrical power or current or voltage to the corresponding LED  310  in the LED light bar  320  of the LCD display device  300 . The above measurement and adjustment continues until the light measured at area  350  reaches a predetermined threshold value. The driver  150  stores a calibration value for the LED  310  in the memory  170  based on electrical power or current or voltage required to produce the predetermined threshold value. The stored calibration value for the LED  310  is used to calibrate the light output of LED  310  with other LEDs in the LED light bar  320  when the portable light-detecting portion  110  is not controlling the LED  310 . 
     In the same manner, in some embodiments, all of the LEDs  305  in the LED light bars  320  are calibrated by the light-adjusting system  100 , and a corresponding calibration value for each LED stored in the memory  170 . 
     In various embodiments, the predetermined threshold value is set using one or more of the methods described in relation to  FIG. 2 . 
       FIG. 4  is a method  400  of calibrating the LCD display devices of  FIGS. 2 and 3  using the light-adjusting system  100 . The method begins at step  410  and proceeds to step  420 . 
     In step  420 , LED  210  or  310  in the LED-backlighting panel  220  or LED light bar  320  is switched on to emit light. Next, the method proceeds to step  430 . 
     At step  430 , a previously set predetermined threshold value is retrieved. The predetermined threshold value is used at step  460  to compare with an LED intensity at an area of the display measured by the portable light-detecting portion  110 . Next, the method proceeds to step  440 . 
     At step  440 , the portable light-detecting portion  110  is connected to the LCD display device  200  or  300  by the connection  160 . Next, the method proceeds to step  450 . 
     At step  450 , the intensity of the LED  210  or  310  is measured by the portable light-detecting portion  110  at the area  250  or  350  corresponding to the LED  210  or  310 . Upon completion of the measurement the method proceeds to step  460 . 
     At step  460 , the measured intensity of the LED  210  or  310  is compared to the predetermined threshold value. The power fed to the LED is adjusted by driver  150  until the measured intensity of the LED substantially matches the predetermined threshold value. Upon completion of the adjustment the method proceeds to step  470 . 
     At step  470 , the power fed to the LED  210  or  310  that causes the intensity of the LED to match substantially the predetermined threshold value is stored as a calibration value in the memory  170  of the driver  150 . After storing the calibration value the method proceeds to step  480 . 
     At step  480 , the steps  430 - 450  are repeated for the remaining LEDs on the display device  200  or  300 . Upon completion of steps  430 - 450  for all of the LEDs the method proceeds to step  490 . 
     At step  490 , the portable light-detecting portion  110  is disconnected from the LCD display device  200  or  300 . The method proceeds to step  495  where the method terminates. 
     Embodiments of the disclosure are applicable to LCD display devices, display such as plasma displays, direct LED displays in which each pixel is an LED or organic LED displays. Further, embodiments of the disclosure are applicable to warn an operator of a safety issue. LEDs are used for lighting and warning applications in, for example, cars, airplanes and trains. The system and method are applicable to measuring LED light intensity as detected on an exterior of a vehicle. For example, the system and method are applicable to measuring LED light intensity on the surface of a headlight casing for a car, comparing the measured light intensities to a specified baseline. The operator is warned if the measured light intensities are below the specified baseline, and the light output of the LEDs corrected to a required safe level. 
     The foregoing has outlined features of several embodiments. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.