1. Field of the Invention
The present invention relates in general to the field of information handling system display brightness, and more particularly to a system and method for calibration of ambient light sensor brightness output.
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.
Typically, information handling systems present information to end users through a display. One common type of display is a liquid crystal display (LCD) which uses liquid crystals to selectively pass varying amounts of red, green and blue light at each of plural pixels to present desired colors. LCDs generally are illuminated with a backlight, such as a CCFL, that runs along one or more edges of a display area. The backlight is generally powered by an inverter that provides a high voltage alternating current from a DC-to-AC inverter power supply. Because LCD panels are both energy efficient and compact, they are typically selected for use as portable information handling system integrated displays. Since portable information handling systems are often carried by end users to various locations with different levels of ambient light, the brightness at which a display panel is illuminated is generally manually selectable by an end user, such as with eight levels sequentially selected with a function up arrow or function down arrow keyboard input. Typically, the various display panels are set so that the brightness level at each of the eight manually selected levels is substantially similar.
Manually adjusting display brightness is often a hassle for end users since it usually requires two hands and the display image is sometimes not visible until after an adjustment is made. Ambient light sensors (ALS) help to avoid the need for manual brightness adjustments by sensing ambient light and automatically applying the sensed ambient light to adjust display brightness. ALS adjustments are typically performed with greater numbers of increments having smaller increment sizes than manual adjustments. For instance, 256 nit values are generally available for adjusting brightness settings output by the inverter with the eight manual settings selected from these increments to have defined brightness levels. However, the response of the ALS adjustments may vary widely at different brightness levels. These variances result in part due to imprecise tolerances found in ALS devices and also due to varying visual impacts that result from ALS adjustments at different nit values and with different display panels. Variance in an ALS response curve for different types of display panels makes it difficult to adapt a common ALS device for use in multiple types of display panels. However, calibration of an ALS device specifically for each type of display panel is prohibitively time consuming and expensive.
Therefore a need has arisen for a system and method which automatically adapts an ALS device response to obtain consistent display panel brightness output.
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 calibrating display panel brightness output. An ambient light sensor response is modified by reference to preset brightness values that output known brightness from an information handling system display. Brightness of the display is then maintained with the modified ambient light sensor response so that the brightness output by different types of displays is substantially calibrated when under management of the ambient light sensor.
More specifically, manually selectable brightness levels are stored at a display in a brightness step table, such as in Electronic Extended Device Identification Data (EEDID) or nonvolatile memory associated with the display inverter. User inputs to manually select a brightness level are performed by retrieving the brightness step table and applying an sequential SMBus value associated with a selected brightness to the inverter. Alternatively, display brightness is automatically adjusted by ambient light sensor measurements of ambient light provided to the inverter. A brightness calibration module modifies the ambient light sensor response to provide a consistent brightness output for different types of displays. For instance, a linearization method produces a modified ambient light sensor response by reference to manually selectable brightness levels. In one embodiment, piecewise linearization based on each pair of sequential manually selectable brightness levels generates a composite ambient light sensor response calibrated so that automatically set brightness under management of the ambient light sensor is consistent with the brightness provided by preset levels.
The present invention provides a number of important technical advantages. One example of an important technical advantage is that ALS device response automatically adapts to calibrate brightness output for different types of display panels during variations of ambient light. Estimating ambient light response based on manual brightness levels provides predictable and consistent responses across different types of display panels without requiring calibration of each type of display panel. Thus, a single ALS device integrates into multiple different types of display panels to reduce the complexity and expense associated with design and repair of display panels. For instance, a common ALS device is integrated into the inverters of plural types of display panels to reduce the number of parts needed for manufacture of an information handling system.
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.
Calibration of ambient light sensor outputs to an information handling system display by reference to manually selectable brightness levels provides consistent automated brightness adjustments for a variety of display types. 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
The brightness at which display 12 is illuminated by CCFL 14 is determined by the power output from inverter 34. In one mode, display brightness is manually controlled with preset brightness step levels through user inputs of function up arrow to increase brightness and function down arrow to decrease brightness. For instance,
In an automated mode, display brightness is automatically adjusted to adapt to varying ambient light conditions as sensed by an ambient light sensor (ALS) 40. For instance,
Referring now to
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.