This application relates to display devices and/or information handling systems with display devices, and more particularly to display devices, information handling systems and related methods for color and luminance characterization and compensation.
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.
Information handling systems typically utilize a display device to provide visual output related to operations occurring within and/or being performed by the information handling system. Depending on the type of information handling system, the display device can be physically connected or affixed to the system, or may be communicatively connected to the system via one or more cables and/or intermediary components (e.g., a docking station). Of the various types of display devices that can be provided with different information handling systems, perhaps the most common type of display device in use today is a liquid crystal display (LCD) device. LCDs are generally configured with a glass display screen, a color filter, a liquid crystal display panel of (color) pixels, and a backlight panel that illuminates the pixels to create an image on the display screen. The backlight panel includes a light source (e.g., a pair of cold cathode fluorescent lamps, CCFLs, or a plurality of light emitting diodes, LEDs), which may be driven to emit light that is transmitted and/or reflected through the LCD panel and color filter, and output from the display screen of the display device.
Over time, and during use of the display device, the color and luminance (i.e., the brightness perceived by a human observer) of the light output from the display device may drift from desired set point(s), such as a desired white balance and/or a desired luminance set point. In some cases, the changes in color and/or luminance over time (and other operating conditions) may be readily apparent to the human observer, and/or may be undesirable for certain image display applications, which require and/or benefit from consistently accurate color and luminance reproduction.
The following description of various embodiments of display devices, systems and methods is not to be construed in any way as limiting the subject matter of the appended claims.
Generally speaking, the present disclosure provides improved display devices, information handling systems and related methods that may be used to maintain consistent color and luminance over changes in operating conditions and lifetime of the display device. More specifically, the present disclosure provides a characterization method, which correlates the color/luminance measured from the light emitted by a light source disposed within the display device to the color/luminance measured from the light output from the display device at the time of manufacture. After the display device is characterized and a set of characterization values are stored within the display device (or within the information handling system), a compensation method is used during operation of the display device to perform color/luminance correction for the light output from the display device by repeatedly measuring the color/luminance of the light source illumination, and adjusting color gain values to maintain the color/luminance of the output light at a reference set point.
According to one embodiment, a method for characterizing a display device may generally begin by driving a light source of the display device to emit light at a reference set point. Once the light source is driven to emit light, the method may obtain a first set of color values corresponding to the light emitted by the light source, and a second set of color values corresponding to light output from the display device. The first set of color values are obtained from a light sensor disposed within the display device for receiving the emitted light, and the second set of color values are obtained from a light analyzer disposed outside of the display device for receiving the output light.
In general, the first set of color values and the second set of color values may be obtained in substantially any color space including, but not limited to, the CIE 1931 XYZ color space, the CIE 1931 xyY color space, the CIE 1931 RGB color space, the CIE 1976 LUV color space, and various other color spaces (e.g., sRGB, Adobe RGB, etc.). In some embodiments, the first set of color values and the second set of color values may include color values within the same color space. In one exemplary embodiment, the first and second sets of color values may include XYZ tristimulus values. In another exemplary embodiment, the first and second sets of color values may include RGB color values. However, the first and second sets of color values are not limited to such color spaces or values. In other embodiments, the first set of color values may include color values within a first color space, and the second set of color values may include color values within a second color space different from the first color space.
Once the first and second sets of color values are obtained, the method may generate a set of characterization values, which correlate the first set of color values to the second set of color values at the reference set point. In some embodiments, the step of generating a set of characterization values may include dividing the second set of color values by the first set of color values. The generated set of characterization values may then be stored, for example, within a storage medium of the display device (or the information handling system).
In some embodiments, the steps of driving a light source, obtaining a first set of color values, obtaining a second set of color values, generating a set of characterization values and storing the set of characterization values may be performed during manufacturing of the display device to characterize the light output by the display device at the reference set point (e.g., a white balance set point, a red set point, a green set point or a blue set point). In some embodiments, the steps of driving a light source, obtaining a first set of color values, obtaining a second set of color values, generating a set of display device characterization values and storing the set of characterization values may be repeated for a plurality of different reference set points.
According to another embodiment, a compensation method for maintaining a color and a luminance of light output from a display device over time may generally begin by driving a light source of the display device to emit light at a reference set point. Once the light source is driven to emit light, the method may obtain a first set of color values corresponding to the light emitted by the light source, and may calculate a second set of color values corresponding to the light output from the display device. The first set of color values may be obtained from a light sensor, which is disposed within the display device for receiving the emitted light. The second set of color values may be calculated by combining the first set of color values with a set of characterization values, which were previously determined during manufacturing of the display device and stored (e.g., within a storage medium of the display device or information handling system).
In general, the first set of color values and the second set of color values may be obtained/calculated within substantially any color space including, but not limited to, the CIE 1931 XYZ color space, the CIE 1931 xyY color space, the CIE 1931 RGB color space, the CIE 1976 LUV color space, and various other color spaces (e.g., sRGB, Adobe RGB, etc.). However, it is generally desired that the compensation method obtains/calculates color values within the same color space(s), which were used in the characterization method to generate the set of characterization values.
In some embodiments, the stored set of display device characterization values may have been previously determined by dividing a fifth set of color values by a fourth set of color values. The fourth set of color values are values, which were previously obtained from a light sensor disposed within the display device upon receiving light emitted from a light source of the display device at the reference set point. The fifth set of color values are values, which were previously obtained from a light analyzer disposed outside of the display device for receiving light output from the display device. In some embodiments, the first, second, fourth and fifth sets of color values may include color values within the same color space. In one exemplary embodiment, the first, second, fourth and fifth sets of color values sets of color values may include XYZ tristimulus values. In one exemplary embodiment, the first, second, fourth and fifth sets of color values sets of color values may include RGB color values. However, the first, second, fourth and fifth sets of color values are not limited to such color spaces or values. In other embodiments, the first set of color values and the fourth set of color values may include color values within a first color space, while the second set of color values and the fifth set of color values comprise color values within a second color space different from the first color space.
Once a second set of color values is calculated, the method may derive a set of gain values from the second set of color values and a third set of color values corresponding to the reference set point, and may use the set of gain values to maintain the color and the luminance of the light output from the display device at the reference set point. In some embodiments, the steps of driving, obtaining, calculating, deriving and using may be performed repeatedly over time during operation of the display device to maintain the color and the luminance of the light output from the display device at the reference set point (e.g., a white balance set point, a red set point, a green set point or a blue set point). In some embodiments, the reference set point may be changed to a new reference set point, and the steps of driving, obtaining, calculating, deriving and using may be repeated to change the color and the luminance of the light output from the display device to the new reference set point.
According to another embodiment, a system is provided herein as comprising a light source, a display panel, a light sensor, a processing device and driver circuitry. In one embodiment, the system is a display device and the processing device is a display controller. In such an embodiment, the display device may be a stand-alone display device, which is communicably coupled to an information handling system. In another embodiment, the system is an information handling system and the processing device is a central processing unit (CPU), graphics processing unit (GPU), display controller, or other processing device of the information handling system. In such an embodiment, the system may include a display device, which is a stand-alone display device that is communicably coupled to the information handling system, or a display device that is permanently or detachably affixed to the information handling system.
The light source may be disposed within the display device and may be configured to emit light at a reference set point (e.g., a white balance set point, a red set point, a green set point or a blue set point). The display panel may be arranged above the light source for receiving the light emitted by the light source, and may be configured for generating images for display on a display screen of the display device. The light sensor may also be coupled to receive the light emitted from the light source, and may be configured to generate a first set of color values corresponding to the emitted light. In some embodiments, the light sensor may be a single light sensor, which is arranged behind the light source near a center point of the display panel. In other embodiments, the light sensor may comprise a plurality of light sensors, each arranged behind the light source and centered behind a different section of the display panel.
The processing device (e.g., a CPU, GPU or display controller) may be coupled to receive the first set of color values from the light sensor(s), and may be configured to calculate a second set of color values corresponding to light output from the system (e.g., the display device or information handling system) by combining the first set of color values with a stored set of characterization values. The processing device may then derive a set of gain values from the second set of color values and a third set of color values corresponding to the reference set point. The driver circuitry may be coupled to the light source and to the processing device, and may be configured to use the set of gain values to alter a drive signal supplied to the light source, so as to maintain a color and a luminance of the light output from the system at the reference set point.
As noted above, the set of characterization values may be predetermined during manufacturing of the system. In some embodiments, the set of characterization values may be stored within a storage medium of the system. In some embodiments, the stored set of characterization values may be predetermined by dividing a fifth set of color values by a fourth set of color values. The fourth set of color values are values, which were previously obtained from a light sensor disposed within the display device upon receiving light emitted from a light source of the display device at the reference set point. The fifth set of color values are values, which were previously obtained from a light analyzer disposed outside of the display device for receiving light output from the display device.
In some embodiments, the first, second, fourth and fifth sets of color values may include color values within the same color space. In one exemplary embodiment, the first, second, fourth and fifth sets of color values sets of color values may include XYZ tristimulus values. In such an embodiment, the light sensor disposed within the display device may be a XYZ tristimulus colorimeter, which is configured for providing the first and fourth sets of color values as a set of XYZ tristimulus values, or as (x,y) chromaticity coordinates and a Y tristimulus value that is convertible into a set of XYZ tristimulus values. The light sensor may be implemented differently in other embodiments.
Other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the accompanying drawings in which:
While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the disclosure to the particular form disclosed, but on the contrary, the present disclosure is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
This disclosure generally relates to display devices and related methods for characterizing a display device at the time of manufacture, and thereafter, for controlling a light source of the display device, so as to maintain a desired color and luminance of the light output from the display device over time and other operating conditions. The display device described herein may be part of, or configured for use with, a variety of different information handling systems.
For purposes of this disclosure, an information handling system, such as information handling system 100 shown in
With reference now to
In the generalized embodiment shown in
Information handling system 100 requires a power source to operate the various electronic components disposed therein. The power source can be provided via an external power source (e.g., mains power) and an internal power supply regulator, and/or by an internal power source, such as a battery. As shown in
System memory 120 and/or NVRAM 150 may be generally configured to store software and/or firmware modules and one or more sets of data that can be utilized during operation of information handling system 100. In some embodiments, one or more of these software and/or firmware modules can be loaded into system memory 120 from NVRAM 150 during operation of system 100. In one embodiment, system memory 120 may include, or may be loaded with, a plurality of such modules, including one or more firmware (FW) modules, a basic input/output system (BIOS), an operating system (OS), and one or more user application(s). These software and/or firmware modules have varying functionality when their corresponding program code is executed by a main processing device (e.g., CPU 110) or a secondary processing device (e.g., GPU 140) of information handling system 100.
As noted above, information handling system 100 also includes a display device 200, which may be a part of, or communicatively coupled to, the information handling system 100. For example, display device 200 may be permanently or detachably affixed to the information handling system 100, when system 100 is a laptop computer, tablet computer, “2 in 1” system or a mobile device. Alternatively, display device 200 may be a stand-alone display device, which is communicatively coupled to information handling system 100 via one or more cables and/or other interfaces (such as a docking station), when system 100 is a desktop computer. Regardless of whether the display device is a stand-alone device, or integrated with the information handling system 100, display device 200 may be coupled to receive data signals and/or display configuration settings from a processing device (e.g., CPU 110 or GPU 140) of system 110, and may be further coupled to receive power from the power management system 170 within system 100.
As shown in
In another embodiment, the software or firmware module used to configure or adjust display configuration settings, such as a white balance set point and/or a luminance set point, may be provided within display device 200. In such an embodiment, a user may make adjustments to the factory default display configuration settings, or to the currently applied display configuration settings, via one or more user-actuated buttons (e.g., power and control buttons 265 of
Device power module 260 provides power management for the display device, and may be coupled for receiving power from a power management system 170 of the information handling system 100, an external power source, or an internal power source (such as a battery). Power and control buttons 265 may include one or more user-actuated buttons for turning display device 200 or information handling system 100 on/off, and/or for setting or adjusting one or more display configuration settings. Display device 200 further includes a data interface 270, which may be communicatively coupled for receiving data signals and/or display configuration settings from a processing device of the information handling system (e.g., from CPU 110 or GPU 140 of
Display controller 250 may use the data signals to display images or video content on the display device by supplying appropriate control signals to display panel 220 and driver circuitry 240. Upon receiving control signals from display controller 250, driver circuitry 240 may supply a drive current to backlight panel 230 for providing backlight illumination to display panel 220. Display controller 250 may control color characteristics of the displayed images or video content by selectively altering one or more pixels of the display panel 220 to control the amount of backlight that passes through the pixels according to specified red, green and blue (RGB) gain settings.
Display controller 250 may further control the amount of backlight that passes through the pixels in accordance with one or more display configuration settings such as, for example, a white balance set point and/or a luminance set point for displaying images on the display screen of the display device 200. As noted above, the white balance set point and/or the luminance set point may be factory default settings provided by the manufacturer of the display device, and/or may be adjustable display configuration settings selectable by a user. In one embodiment, the display configuration settings may be supplied to display controller 250 via data interface 270 and/or via power and control buttons 265. In another embodiment, the display configuration settings may be stored within display controller 250, or within a storage medium 280 coupled to the display controller.
Display controller 250 may be any sub-system component that is capable of performing the operations noted herein for the display controller. For example, display controller may be a programmable integrated circuit, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller unit (MCU), a central processing unit (CPU) or other processing device. In some embodiments, display controller 250 may comprise, or be configured to execute, software and/or firmware to perform one or more of the operations noted herein.
Display panel 220 may include a variety of different types of display panels including, but not limited to, a light emitting diode (LED) display panel, an organic-LED (OLED) display panel and a liquid crystal display (LCD) panel. For the sake of brevity, display panel 220 is illustrated in
Since LCD panels produce no light on their own, backlight panel 230 is included within the display device 200 to illuminate display panel 220 and produce a visible image on the display panel/display screen of the display device. Although some LCD panels are illuminated with cold cathode fluorescent lamps (CCFL) placed at opposite edges of the display, or arranged as an array of parallel CCFLs, most LCD display devices are now being provided with an LED backlight, instead of the traditional CCFL backlight. Compared to CCFL backlights, LED backlights offer a wider color gamut, produce images with greater dynamic contrast, allow a wider dimming range and can be used to produce very slim display devices. In addition, LED backlights consume less power, have longer lifespans and are generally more reliable than CCFL backlights.
According to one embodiment, LED backlight panel 230 may comprise a serial string of LED emitters (EM) 232 arranged along each side edge of the LCD display screen. The combination of LCD panel 220 and an LED backlight panel 230 having side edge-mounted LEDs results in an edge-lit LCD display device. Many edge-lit LCD display devices comprise a string of white LED emitters 232, which are typically formed by coating a blue LED having a peak emission wavelength of about 450-490 nm with a phosphor (e.g., Yttrium aluminium garnet, YAG). Some edge-lit LCD display devices may comprise a string of RGB LED emitters 232. As shown in
An edge-lit LED backlight panel 230, as shown in
According to an alternative embodiment, LED backlight panel 230 may comprise a two-dimensional array of LED emitters (not shown), which is disposed behind LCD 222 and diffuser 234 for providing the illumination necessary to produce visible images or video content on display panel 220. The two-dimensional array may include an array of phosphor-converted white LEDs, an array of RGB LEDs, or an array of RGBW LEDs. LCD panels lit with RGB or RGBW LEDs provide wider color gamuts than those lit with phosphor-converted white LEDs, and therefore, may be preferred in some display devices and information handling systems where wide color gamuts are desired.
Although depicted as an LCD display device, and more specifically, an edge-lit LCD display device in
Although LEDs provide many advantages over other light sources used for illumination within a display device, the color and luminance of the light emitted by currently available LEDs tends to vary with changes in operating conditions (e.g., changes in drive current and junction temperature) and over time, as the LEDs age. For example, the luminous flux output from all LEDs generally decreases with increasing temperature, causing the light output from the display device to appear “dimmer” (i.e., less bright) with increasing LED junction temperature.
The chromaticity of the illumination produced by LEDs also varies with temperature, due to shifts in the dominant wavelength (for both phosphor-converted and non-phosphor converted LEDs) and changes in the phosphor efficiency (for phosphor-converted white LEDs). This change in chromaticity is different for different colors of LEDs. For example, while the peak emission wavelength of green LEDs tends to decrease with increasing junction temperature, the peak emission wavelength of red and blue LEDs tends to increase with increasing junction temperature. Although the change in chromaticity is relatively linear with temperature for most colors, red and yellow LEDs tend to exhibit a more significant non-linear change. This means that when RGB LEDs are combined within a display device, the color point of the illumination produced by the display device may appear increasingly “cooler” as the junction temperature of the LEDs rises. Phosphor converted white LEDs, on the other hand, may appear “cooler” or “warmer” with increasing junction temperature, depending on the peak emission wavelength of the LED and the phosphor used to produce the white LED.
As LEDs age, the luminous flux output from both phosphor-converted and non-phosphor converted LEDs, and the chromaticity of phosphor-converted LEDs, also changes over time. Early on in life, the luminous flux can either increase (get brighter) or decrease (get dimmer), while late in life, the luminous flux generally decreases for all LEDs. As expected, the luminous flux output decreases faster over time when LEDs are subjected to higher drive currents and higher temperatures, often resulting in a noticeably dimmer display device. As a phosphor-converted white LED ages, the phosphor becomes less efficient and the amount of blue light that passes through the phosphor increases. This decrease in phosphor efficiency causes the overall color produced by the phosphor-converted white LED to appear “cooler” over time. Although the dominant wavelength and chromaticity of a non-phosphor converted LED (e.g., a red, green or blue LED) does not change over time, the luminous flux decreases as the LED ages, which in effect causes the chromaticity of light emitted by red, green and blue LEDs to change over time.
It is generally desirable that the light output from a display device (i.e., the light transmitted out of the device through the display screen 210) maintains consistent color and luminance over operating conditions and the lifetime of the display device. In other words, the light output from the display device should not deviate or drift significantly from a reference set point (e.g., a white balance set point, a luminance set point, a red set point, a green set point or a blue set point) during use of the display device, or over time. In LED-illuminated display devices (including LED-illuminated LCD devices, LED display devices and OLED display devices), the LED emitters are responsible for a vast majority of the color and luminance drift (e.g., roughly 90%), while the remaining display panel components (e.g., the LGP 234, LCD 222, color filter 224 and display screen 210 shown in the LCD device embodiments of
While prior art display devices and methods have attempted to combat age-related color and luminance drift by simply increasing the drive currents supplied to the LEDs over time, doing so creates additional problems. While it is true that supplying larger drive currents to the LEDs will increase the generated luminous flux, and therefore, the brightness of the display device, larger drive currents inherently result in higher LED temperatures, which affect the chromaticity of the emitted illumination and accelerate LED aging. Therefore, this method alone cannot be used to maintain consistent color and luminance from the LED emitters. This method also cannot be used to account for the color and luminance drift attributable to other display panel components, such as the LGP 234, LCD 222, color filter 224 and display screen 210 shown in the LCD device embodiments of
As described in more detail below with regard to
In the embodiments of
Once the light source is drive to emit light, method 300 may obtain a first set of color values corresponding to the light emitted by the light source from a light sensor, which is disposed within the display device for receiving the emitted light (in step 320). The first set of color values may be obtained (i.e., directly measured or calculated) in a first color space, including but not limited to, the CIE 1931 XYZ color space, the CIE 1931 xyY color space, the CIE 1931 RGB color space, the CIE 1976 LUV color space, and various other color spaces (e.g., sRGB, adobe RGB, etc.). In the embodiments of
In some embodiments, a single light sensor 290 may be arranged behind backlight panel 230 near a center point of display panel 220, as shown in
In some embodiments, light sensor 290 may be an XYZ tristimulus color sensor (or colorimeter), which is coupled and configured for obtaining a first set of XYZ tristimulus color values from the light emitted by the light source. In one exemplary embodiment, light sensor 290 may be a TCS3430 XYZ tristimulus color sensor from AMS USA Inc.; however, other XYZ tristimulus color sensors obtained from other manufacturers may also be used. An XYZ tristimulus color sensor provides direct measurement of color values in the CIE 1931 XYZ color space, which encompasses all color sensations that an average person can experience. In the CIE 1931 XYZ color space, Y is defined as luminance (i.e., perceived brightness), and the XZ plane is defined as containing all possible (x,y) chromaticities at that luminance.
However, light sensor 290 is not strictly limited to an XYZ tristimulus color sensor, nor is it restricted to measuring XYZ tristimulus color values, in all embodiments. In one alternative embodiment, light sensor 290 may be configured for providing the first set of color values as (x,y) chromaticity coordinates and a Y tristimulus value that is convertible into a set of XYZ tristimulus values. In another alternative embodiment, light sensor 290 may be an RGB color sensor, which is coupled and configured for obtaining a first set of RGB color values from the light emitted by the light source. In most embodiments, however, an XYZ color sensor may be preferred over an RGB color sensor, since an XYZ color sensor provides a direct measurement of real color coordinates and brightness (as opposed to a measurement of mixed RGB color effects), and thus, provides an accurate measurement of color and brightness.
In step 330, method 300 may obtain a second set of color values corresponding to light output from the display device from a light analyzer, which is disposed outside of the display device for receiving the output light. The second set of color values may be obtained (i.e., directly measured or calculated) in a second color space, including but not limited to, the CIE 1931 XYZ color space, the CIE 1931 xyY color space, the CIE 1931 RGB color space, the CIE 1976 LUV color space, and various other color spaces (e.g., sRGB, Adobe RGB, etc.). In some embodiments, light analyzer 205 may be configured for obtaining the second set of color values from the same color space used to obtain the first set of color values. In other embodiments, light analyzer 205 may be configured for obtaining the second set of color values from a second color space, which is different from the first color space.
In the embodiments of
In one alternative embodiment, light sensor 290 and light analyzer 205 may both comprise tristimulus colorimeters for measuring XYZ tristimulus values of the emitted light and the output light, respectively. In another alternative embodiment, light sensor 290 may be tristimulus colorimeter configured for measuring XYZ tristimulus values of the emitted light, and light analyzer 205 may be a spectrocolorimeter coupled for measuring the spectral power distribution of the output light and configured for calculating XYZ tristimulus values corresponding to the measured distribution.
In step 340, method 300 may generate a set of characterization values 345, which correlate the first set of color values to the second set of color values at the reference set point. By correlating the first set of color values to the second set of color values, the set of display device characterization values 345 may be used during a subsequent compensation method (e.g., method 400 shown in
In some embodiments, the set of characterization values 345 may be generated in step 340 by dividing the second set of color values by the first set of color values. According to one embodiment, the set of characterization values 345 may be generated in step 340, as shown in EQ. 1.
In EQ. 1, the XYZ matrix corresponds to the first set of color values obtained from a light sensor disposed within the display device (e.g., light sensor 290), the RGB matrix corresponds to the second set of color values obtained from a light analyzer disposed outside of the display device (e.g., light analyzer 205), and C11 . . . C33 correspond to the set of characterization values 345, which correlate the first set of color values to the second set of color values at the reference set point.
Once the set of characterization values 345 are generated in step 340, they may be stored in step 350 for use in a subsequent compensation method. In some embodiments, the set of characterization values may be stored within a storage medium of the display device or the information handling system. In the embodiments of
In some embodiments, steps 310-350 may be performed during manufacturing of the display device (or shortly thereafter) to determine a baseline from which color and luminance can be subsequently corrected to compensate for light source aging and other changes that occur in the output light during use of the display device. In the above described embodiments, this baseline is a set of characterization values, which correlates a first set of color values, which is obtained from a light sensor disposed within the display device in response to light emitted from a light source at a reference set point, to a second set of color values obtained from a light analyzer disposed outside of the display device in response to light output from the display device. In some embodiments, the reference set point may be a white balance set point and/or a luminance (i.e., brightness) set point for displaying images on a display screen of the display device. In other embodiments, the reference set point may be a red reference set point, a green reference set point and/or a blue reference set point.
In other embodiments, steps 310-350 may be repeated for a plurality of different reference set points, so as to generate and store a set of characterization values within a storage medium of the display device or information handling system for each of the different reference set points. In one such embodiment, steps 310-350 may be repeated for a plurality of different white balance set points and/or luminance set points. Such an embodiment may be desirable if the display device enables the white balance set point and/or the luminance set point to be adjusted, for example, by a user of the display device. In another such embodiment, a display device comprising an RGB light source may be characterized by repeating steps 310-350 at a red reference set point, a green reference set point, and/or a blue reference set point.
As shown in
In the embodiments of
Once the light source is driven to emit light, method 400 may obtain a first set of color values corresponding to the light emitted by the light source from a light sensor, which is disposed within the display device for receiving the emitted light (in step 420). The first set of color values may be obtained (i.e., directly measured or calculated) in a first color space, including but not limited to, the CIE 1931 XYZ color space, the CIE 1931 xyY color space, the CIE 1931 RGB color space, the CIE 1976 LUV color space, and various other color spaces (e.g., sRGB, Adobe RGB, etc.). In the embodiments of
As noted above, light sensor 290 may be a single light sensor 290, which is arranged behind backlight panel 230 near a center point of display panel 220, or may comprise a plurality of light sensors 290, each arranged behind backlight panel 230 and centered behind a different section of display panel 220. Although light sensor 290 may be configured for obtaining the first set of color values within substantially any color space, light sensor 290 may be an XYZ tristimulus color sensor, in at least one embodiment. As noted above, an XYZ tristimulus color sensor may be preferred due to its ability to generate accurate measurements of real color and intensity.
In step 430, method 400 calculates a second set of color values corresponding to a predicted light output from the display device. In other words, a light sensor or light analyzer will typically not be disposed outside of the display device for measuring light output during user operation of the display device. Therefore, method 400 computes a predicted light output in step 430 by combining the first set of color values obtained in step 420 with the set of characterization values 345, which were generated at the time of manufacturing and stored within the display device or the information handling system for later use. In the embodiments shown in
According to one embodiment, the second set of color values corresponding to the predicted light output from the display device may be calculated in step 430 by multiplying the first set of color values with the set of characterization values, as shown in EQ. 2.
In EQ. 2, the X′Y′Z′ matrix corresponds to the first set of color values obtained from the internal light sensor (e.g., light sensor 290) in step 420, C11 . . . C33 correspond to the set of characterization values 345 that were generated and stored in method 300, and the R′G′B′ matrix corresponds to the second set of color values, which correspond to the predicted light output from the display device. By multiplying the first set of color values (X′Y′Z′) obtained from the internal light sensor in step 420 with the stored set of characterization values (C11 . . . C33), EQ. 2 can be used to predict the light output from the display device.
In step 440, method 400 derives a set of gain values that may be used to compensate or correct for the color/luminance drift of the light output from the display device. According to one embodiment, a set of gain values may be derived in step 440 by combining the second set of color values calculated in step 430 with a third set of color values corresponding to the reference set point, as shown in EQ. 3.
In EQ. 3, the R′G′B′ matrix corresponds to the second set of color values calculated in step 430, the WXWYWZ matrix corresponds to the third set of color values corresponding to the reference set point (e.g., a white balance set point), and R′gain, G′gain, and B′gain correspond to the RGB gain values derived in step 440. In the embodiments shown in
In step 450, the RGB gain values derived in step 440 are used to maintain the color and luminance of the light output from the display device at the reference color set point (e.g., the white balance set point, WXWYWZ). In the embodiments shown in
As noted above, method steps 410-450 may be repeated over the lifetime of the display device to maintain consistent color/luminance of the light output from the display device at the reference set point. In some embodiments, the reference set point may be changed to a new reference set point (e.g., a new white balance set point), and steps 410-450 may be repeated to change the color and the luminance of the light output from the display device to the new reference set point.
According to one embodiment, the characterization method 300 shown in the flow chart diagram of
In some embodiments, the computer readable code or program instructions used to implement characterization method 300 and compensation method 400 may be stored within a computer readable storage medium (e.g., storage medium 280) and may be executed by a display controller (e.g., display controller 250) or other processing unit of a display device (e.g., display device 200). Although illustrated in
While the present disclosure may be adaptable to various modifications and alternative forms, specific embodiments have been shown by way of example and described herein. However, it should be understood that the present disclosure is not intended to be limited to the particular display device, information handling system and/or methods disclosed and illustrated herein. Rather, the present disclosure is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
In some implementations, certain steps of the methods described herein may be combined, performed simultaneously or in a different order, or perhaps omitted, without deviating from the scope of the disclosure. Thus, while the method steps are described and illustrated in a particular sequence, use of a specific sequence of steps is not meant to imply any limitations on the disclosure. Changes may be made with regards to the sequence of steps without departing from the spirit or scope of the present disclosure. Use of a particular sequence of steps is therefore, not to be taken in a limiting sense, and the scope of the present disclosure is defined only by the appended claims. Furthermore, certain changes may be made with regard to the display device and/or the information handling system without departing from the spirit or scope of the present disclosure. For example, the display device may be configured with a light source, display panel and/or light sensor different from those described and illustrated herein. Thus, the present disclosure is not limited to only those embodiments shown and described herein, and may include other embodiments and/or combinations of embodiments.