Abstract:
An ambient light sensor testing module running on an information handling system verifies that an ambient light sensor managing brightness of an information handling system display is active and responding correctly. The testing module sets the display at first and second manually-selectable brightness levels and compares the brightness set from the first and second manually-selectable brightness levels when the ambient light sensor is engaged to set display brightness. An excessive difference between the brightness set by the ambient light sensor from the first and second manually-selectable brightness levels indicates a faulty ambient light sensor.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates in general to the field of information handling system displays, and more particularly to a system and method for ambient light sensor testing. 
   2. Description of the Related Art 
   As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems. 
   Portable information handling systems have, in particular, grown in popularity among end users. Portable information handling systems have integrated displays and an internal power source, such as a battery, so that end users may carry the system around while the system is operating. Portable information handling systems that interface through wireless networks allow end users to carry their office virtually anywhere. Since portable information handling systems are easily carried by an end user through different types of lighting environments, the systems typically include an interface to allow the end user to adjust display brightness. For instance, the key combination of function and up arrow increases display brightness while the key combination of function down arrow decreases display brightness. Generally, a plurality of brightness adjustment steps are available with each manual increase or decrease resulting in a step up or a step down of brightness. However, manual adjustments to brightness are often inconvenient for end users, especially where two hands are required while the end user is carrying the portable information handling system. 
   Ambient light sensors provide an automated way to adjust display brightness for varying external lighting conditions. Ambient light sensors measure the external light conditions and adjust the power to the display backlight to brighten the display when external lighting becomes more bright and to dim the display when external lighting becomes more dim. Automated brightness control allows an end user to continue using a portable information handling system as ambient lighting conditions change with minimal disruption to the presentation at the display. Displays having brightness automatically managed with an ambient light sensor avoid “over-bright” conditions which increase the stress on the backlight and more rapidly decrease battery power. However, including an ambient light sensor in a portable information handling system tends to increase the complexity of the manufacture of the system. For example, in order to test the operations of an ambient light sensor, a calibrated external light source, multimeters and user interaction are typically needed to determine whether the ambient light sensor is active and responding correctly. Such testing is time consuming, labor intensive, cumbersome and not easily performed out side of a laboratory, such as at an end user location. 
   SUMMARY OF THE INVENTION 
   Therefore a need has arisen for a system and method which tests an ambient light sensor managing brightness at an information handling system display. 
   In accordance with the present invention, a system and method are provided which substantially reduce the disadvantages and problems associated with previous methods and systems for testing an ambient light sensor. Ambient light sensor adjustments from first and second manually-selectable brightness levels are compared to verify that the ambient light sensor is active and accurately correcting screen brightness in response to detected ambient light levels. 
   More specifically, a testing module integrated in a portable information handling system automatically tests an ambient light sensor associated with an integrated display. The testing module commands the display to a first manually-selectable brightness, such as minimum brightness, and then engages the ambient light sensor to bring the display to a brightness managed by the ambient light sensor. The brightness setting of the ambient light sensor is determined after a slight delay for stabilization, and then the testing module commands the display to a second manually-selectable brightness, such as maximum brightness. The testing module again engages the ambient light sensor to bring the display to a brightness managed by the ambient light sensor and the brightness setting of the ambient light sensor is determined after a slight delay for stabilization. To determine that the ambient light sensor is active and providing accurate adjustments for sensed ambient light, the two separate ambient light sensor brightness settings are compared. The ambient light sensor fails if the two brightness settings have greater than a predetermined difference and passes if the two brightness settings are substantially the same. 
   The present invention provides a number of important technical advantages. One example of an important technical advantage is that ambient light sensor management of display brightness is quickly and simply tested for responsiveness. Active and correct ambient light sensor operations are tested at an information handling system without external equipment so that the test may be automatically initiated at an end user location. Test results are electronically available without user intervention so that the test may be accomplished as part of the manufacture process for an information handling system without additional labor and with automated reporting to a diagnostics server through a network. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may be better understood, and its numerous objects, features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. The use of the same reference number throughout the several figures designates a like or similar element. 
       FIG. 1  depicts a block diagram of an information handling system having an ambient light sensor testing module; and 
       FIG. 2  depicts a flow diagram of a process for testing an ambient light sensor. 
   

   DETAILED DESCRIPTION 
   Ambient light sensor testing capability is integrated within a portable information handling system. For purposes of this disclosure, an information handling system may include any instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, or other purposes. For example, an information handling system may be a personal computer, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The information handling system may include random access memory (RAM), one or more processing resources such as a central processing unit (CPU) or hardware or software control logic, ROM, and/or other types of nonvolatile memory. Additional components of the information handling system may include one or more disk drives, one or more network ports for communicating with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The information handling system may also include one or more buses operable to transmit communications between the various hardware components. 
   Referring now to  FIG. 1 , a block diagram depicts an information handling system  10  having an ambient light sensor testing module. Information handling system  10  is configured as a portable system having an integrated liquid crystal display (LCD)  12  to present visual information generated by processing components, such as a CPU  14 , hard disk drive  16 , RAM  18 , network interface card  20  and chipset  22 , which are disposed in a housing  24 . An embedded controller  26  receives user inputs through input devices and a graphics processor unit (GPU)  28  formats visual information for presentation at display  12 . An inverter  30  provides power to a backlight, CCFL  32 , which illuminates the image presented at display  12 . Inverter  30  provides variable settings of power to backlight  32  to provide variable brightness levels. Brightness settings are automatically varied based on ambient light detected proximate display  12  by an ambient light sensor (ALS)  34 . For example, as ALS  34  detects increased levels of ambient light brightness, inverter  30  provides increased brightness settings for illuminating backlight  32 . As ALS  34  detects decreased levels of ambient light brightness, inverter  30  provides decreased brightness settings for illuminating backlight  32 . Brightness settings are, alternatively, manually selectable based on user inputs, such as the function up/down arrow combination input through embedded controller  26 . For instance, eight step brightness values are manually-selectable from a minimum brightness setting to a maximum brightness setting. 
   In order to test the operation of ALS  34 , firmware instructions are integrated into a processing component, such as a microcontroller operating in inverter  30 , embedded controller  26  or a BIOS  36  running on chipset  22 , which alters brightness settings at inverter  30  and checks that ALS  34  returns the brightness setting to substantially the same value. For instance, a testing module  38  is included in BIOS  36  to test the repeatability of the response of ALS  34 . Testing module  38  automatically commands a brightness selector  40  to set the manually-selectable minimum value at inverter  30 . Testing module  38  then automatically engages ALS  34  to adjust the brightness of display  12  to compensate for ambient lighting conditions. After a slight delay to stabilize the brightness setting made by ALS  34 , a brightness setting detector  42  reads the brightness setting at inverter  30 . After the reading is complete, testing module  38  next automatically commands brightness selector  40  to set the manually-selectable maximum value at inverter  30 . Testing module  38  then once again automatically engages ALS  34  to adjust the brightness of display  12  to compensate for ambient lighting conditions. After a slight delay, brightness setting detector  42  reads the brightness setting at inverter  30  as set by ALS  34 . Testing module  38  compares the two ALS brightness settings read by brightness setting detector  42  to determine an ALS failure if the difference is too great or to determine an ALS pass if the two ALS brightness settings are substantially similar. The pass or fail status may be communicated to a network location through NIC  20  or presented at display  12 . Because ALS testing is internally supported, an ALS test may be automatically performed during manufacture and communicated to a diagnostics server to ensure proper ALS operation before shipment of the information handling system. 
   Referring now to  FIG. 2 , a flow diagram depicts a process for testing an ambient light sensor. The process starts at step  44  with initiation of an ALS test and continues to step  46  to set the test iteration value to zero. At step  48 , the SMBus mode is enabled to support two-way communication between the inverter and the testing module. At step  50 , a determination is made of whether the test iteration value is zero, and, if so, the process continues to step  52  to set the display panel brightness to maximum. If at step  50  the iteration is not zero, such as will occur with the loop iteration explained below, the process continues to step  54  to set the display panel brightness to minimum. From steps  52  or  54 , the process continues to step  56  to switch from manually-selectable brightness settings to management of brightness by the ALS. At step  58 , the current brightness setting is read as commanded by the ALS and assigned a variable of b 0  for the first iteration and b 1  for the second iteration. At step  60  a determination is made of whether the iteration is equal to one. If not, the process continues to step  62  to set the iteration value to one and back to step  48  to complete the second iteration of the loop. If at step  60  the iteration value is one, then values exist for both b 0  and b 1  and the process continues to step  64  to compare the values of b 0  and b 1 . If the comparison at  64  indicates a difference between b 0  and b 1  that is greater than a predetermined value, the process continues to step  66  to indicate a bad ambient light sensor. If the comparison at step  64  shows that the values of b 0  and b 1  are substantially the same, the process continues to step  68  to indicate a good ambient light sensor. 
   Although the present invention has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims.