Patent ID: 12217722

DETAILED DESCRIPTION

Systems and techniques directed at frequency compensation for a display are disclosed. Many electronic devices (e.g., wireless-network devices, desktops, smartwatches) include an electronic visual display, often referred to as a display or screen, integrated as a portion of the electronic device's housing. Electronic device manufacturers fabricate these displays in a layered structure (“display panel stack”), containing a cover layer (e.g., cover glass) and a display module having a display panel.

These display panels include an array of pixel circuits, each having an organic light emitting diode (“pixel”). The pixels may be composed of any colored combination of one or more subpixels, including a red subpixel, a green subpixel, and/or a blue subpixel. Electronic devices can control any of the pixels within a display panel to illuminate at various intensities and wavelengths (e.g., combined wavelengths of the sub-pixels), effective to produce on-screen content (e.g., images). By exploiting a feature of the human eye and brain referred to as persistence of vision (e.g., retinal persistence), a display panel can redraw on-screen content at predetermined frequencies (“refresh rate”) to save power, change on-screen content (e.g., scrolling) seamlessly, and give an illusion of on-screen content as images in motion (e.g., video). For example, a display panel configured to operate at a 120 hertz (Hz) refresh rate can redraw on-screen content 120 times per second. The benefits of displays such as organic light-emitting diode (OLED) displays include high refresh rates, small display response times, and low power consumption. These benefits make OLED displays well-suited for electronic devices, and are further appreciated by users, in large part, because of their display image-quality.

In example aspects, display technology, including low temperature polysilicon liquid crystal displays (LTPSs), can be driven at different refresh rates meaning different frequencies. It should be appreciated the LTPS displays are one type of OLED displays. For example, at different times during use of a device such as a smartphone, an LTPS display may be driven at 60, 90, or 120 Hz for different purposes. Lower frequencies may be employed for battery saving techniques while higher frequencies may be employed for applications such as displaying video. Changing the frequency or refresh rate during use of the display can be referred to as a VRR. A manufacturer of the display may manufacture the display such that multiple regions of the display are uniform relative to one another while driven at a first frequency but the multiple regions of the display are not uniform relative to one another when the display is driven at frequencies other than the first frequency. The difference in uniformity between regions of the same display when driven at different refresh rates can be referred to as transition flicker. The present technology generates compensations masks and RGB data such that the multiple regions of the display will be uniform when driven at frequencies different from the first frequency.

The following discussion describes operating environments, techniques that may be employed in the operating environments, and example methods. Although techniques using and apparatuses for frequency compensation for a display are described, it is to be understood that the subject of the appended claims is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as example implementations and reference is made to the operating environment by way of example only.

Example Environment

FIG.1illustrates an example device diagram100of an electronic device102in which frequency compensation for a display can be implemented. The electronic device102may include additional components and interfaces omitted fromFIG.1for the sake of clarity. The electronic device102can be a variety of consumer electronic devices. As non-limiting examples, the electronic device102can be a smartphone102-1, a tablet device102-2, a laptop computer102-3, a computerized watch102-4, a portable video game console102-5, smart glasses102-6, virtual-reality (VR) goggles102-7, and the like.

The electronic device102includes one or more processors104. The processor(s)104can include, as non-limiting examples, a system-on-a-chip (SoC), an application processor (AP), a central processing unit (CPU), or a graphics processing unit (GPU). The processor(s)104generally execute commands and processes utilized by the electronic device102and an operating system installed thereon. For example, the processor(s)104can perform operations to display graphics of the electronic device102on a display and can perform other specific computational tasks, such as controlling the creation and display of an image on the display.

The electronic device102also includes computer-readable media (CRM)106. The CRM106is a suitable storage device (e.g., random-access memory (RAM), static RAM (SRAM), dynamic RAM (DRAM), non-volatile RAM (NVRAM), read-only memory (ROM), flash memory) configured to store device data of the electronic device102, user data, and multimedia data. The CRM106may store an operating system that generally manages hardware and software resources (e.g., the applications) of the electronic device102and provides common services for applications stored on the CRM106. The operating system and the applications are generally executable by the processor(s)104to enable communications and user interaction with the electronic device102.

The electronic device102further includes one or more sensors108. In some examples, the sensors108may be disposed on or in a peripheral input device connected (e.g., wired, wirelessly) to the electronic device102. In implementations, the sensors108include display sensors including a touch-input sensor (e.g., a touchscreen), an image-capture device (e.g., a camera, video-camera), proximity sensors (e.g., capacitive sensors), an ambient light sensor (e.g., photodetector), and/or an under-display fingerprint sensor (UDFPS).

The electronic device102further includes an OLED display110having a pixel array112and a driver114that can be described as a display driver integrated circuit. Although an OLED display110is described herein, it is provided as an example only. In additional or alternative implementations, the electronic device102may include any of a variety of displays, including an active-matrix OLED (AMOLED) display, an electroluminescent display (ELD), a microLED display, a liquid crystal display (LCD), a thin film transistor (TFT) LCD, an in-place switching (IPS) LCD, a plasma monitor panel (PDP), and so forth.

Further, the driver114may control the pixel circuits of a pixel array112for the OLED display110. The pixel array112may include multiple regions including region116, region118, region120, region122. The OLED display110may be driven by the driver114at different frequencies. Driving the OLED display110at a given frequency can result in differences in uniformity between the regions116,118,120, and122. A compensation mask and RGB data may be applied to the OLED display110by the driver114when driven at the given frequency to compensate for the differences between the regions116,118,120, and122such that the regions116,118,120, and122appear uniform when driven at the given frequency. Together, under the direction of the processor(s)104, the driver114controls the pixel array112to generate light to create an image on the OLED display110.

In one aspect, a first uniformity of the multiple regions of the OLED display110can be measured at a reference frequency, such as 120 Hz. The reference frequency can be the frequency guaranteed by the manufacturer of the display to provide uniformity. The OLED display110can then be driven at a second frequency, such as 90 Hz or 60 Hz, and a second uniformity of the multiple regions of the display can be measured. The measurements can be made in an XYZ domain as opposed to a RGB domain. The differences between the first and second uniformity can then be used to generate a compensation mask. XYZ domain data from the first and second uniformity measurements can be used to generate a color model characterization. The color model characterization can be used to convert the XYZ domain data into RGB data when the OLED display110is driven at the second frequency to compensate for the differences in uniformity across the multiple regions of the OLED display110.

FIGS.2A and2Billustrate example systems of diagrams200and210, respectively, in which frequency compensation for a display can be implemented. Diagram200depicts the OLED display110with a camera202and a device controller204. The device controller204can drive the OLED display110at different frequencies and the camera202can measure the light output by the OLED display110. The camera202can be a two-dimensional (2D) camera that is capable of measuring a color map of different regions of the OLED display110when driven at different frequencies.

In one aspect, the OLED display110can be manufactured or tuned such that multiple regions of the OLED display110are uniform when driven at a certain frequency. For example, the OLED display110can be designed or manufactured with 120 Hz as a frequency that provides uniformity across all regions of the display. This frequency may be described as the reference frequency. The reference frequency may be guaranteed to provide uniformity by the manufacturer of the OLED display110. The OLED display110may not be manufactured with a guarantee of uniformity across multiple regions for different frequencies, the OLED display110may not be manufactured with such guarantees for different frequencies to reduce cost in manufacturing the OLED display110. However, in use the OLED display110may be driven at different frequencies for purposes such as reducing power consumption to increase battery life.

In one aspect, diagram200depicts a system for generating a uniformity-gain estimation that can be performed before the OLED display110is shipped to a consumer. The OLED display110can be driven at the reference frequency by the device controller204. In one example, the reference frequency is 120 Hz. The device controller204can drive the OLED display110using an RGB format image that causes the OLED display110to display an image or video and can be referred to as a control signal. The camera202is used to capture light from the OLED display110. The light captured by the camera202can be a color map that provides information or data about the uniformity of different regions of the OLED display110as compared to one another. In one example, the camera202can be a 2D camera or other image capturing device. The device controller204can vary the control signal while driving the OLED display110at the reference frequency. For example, the control signal can provide low, mid and high decibel Volt (dBv) settings as well as low, mid and high gray levels.

After data has been captured by the camera202while the OLED display110is driven at the reference frequency, the OLED display110can be driven at a second frequency by the device controller204and data can be captured by the camera202. This process can be repeated for any number of frequencies that are different from the reference frequency. For example, a second frequency can be 90 Hz and a third frequency can be 60 Hz.

In one aspect, the color map captured by the camera202can have XYZ data in two dimensions. The XYZ data can include RGB data as well as other data. In one example, the X measures red color, the Y measures green color, and the Z measures blue color. The XYZ can also include data such as gain, luminosity, brightness, sharpness, etc. The XYZ data in the XYZ domain or CIE color space for RGB control signal input can be represented by Xi,j,k(U,V)where (U,V) represents a pixel in the pixel resolution of the OLED display110. Example data for pixel (U,V) can be i∈{60 Hz, 90 Hz, 120 Hx}; j∈{0×100, 0×200, . . . 0×FFF}; k∈{G32, G64, G128, . . . G255}; U∈{0, 1, 2, U−1}; and V∈{0, 1, 2, V−1}. The XYZ color map can be used to generate the uniformity gain estimation for each frequency that the OLED display110is driven at by the device controller204.

FIG.2Band diagram210depict a system for generating a color model characterization. The diagram210includes the OLED display110, the device controller204, and a light-measuring device212. The light-measuring device212can be a colorimeter or a spectroradiometer that is used for capturing data from the OLED display110when the OLED display110is driven at a frequency by the device controller204. In one aspect of diagram210, the control signal from the device controller204can include RGB data (Ri, Gi, Bi) as well as gray colors used to characterize a color model of the OLED display110.

The color model characterization can be generated by equation 1:
C+H*D→H=C*inv(D)  Equation 1

In Equation 1, C represents CIE X,Y,Z value for corresponding RGB patterns, in other words, C represents the color transfer function RGB to XYZ transfer function, D represents RGB digital values, and H represents a color transform function. Example values for D and C are shown below:

D=(R⁢0⁢G⁢0⁢B⁢0R⁢1⁢G⁢1⁢B⁢1R⁢2⁢G⁢2⁢B⁢2R⁢3⁢G⁢3⁢B⁢3---RiGi⁢B⁢iR⁢0⁢G⁢0⁢B⁢0R⁢1⁢G⁢1⁢B⁢1R⁢2⁢G⁢2⁢B⁢2R⁢3⁢G⁢3⁢B⁢3RiGi⁢B⁢iR⁢0⁢G⁢0⁢B⁢0R⁢1⁢G⁢1⁢B⁢1R⁢2⁢G⁢2⁢B⁢2R⁢3⁢G⁢3⁢B⁢3RiGi⁢B⁢i)C=(XR⁢0⁢G⁢0⁢B⁢0XR⁢1⁢G⁢1⁢B⁢1XR⁢2⁢G⁢2⁢B⁢2XR⁢3⁢G⁢3⁢B⁢3---XR⁢i⁢G⁢i⁢B⁢iYR⁢0⁢G⁢0⁢B⁢0YR⁢1⁢G⁢1⁢B⁢1YR⁢2⁢G⁢2⁢B⁢2YR⁢3⁢G⁢3⁢B⁢3YR⁢i⁢G⁢i⁢B⁢iZR⁢0⁢G⁢0⁢B⁢0ZR⁢1⁢G⁢1⁢B⁢1ZR⁢2⁢G⁢2⁢B⁢2ZR⁢3⁢G⁢3⁢B⁢3ZR⁢i⁢G⁢i⁢B⁢i)

To convert the XYZ data to RGB data and generate the compensation mask, the matrix of data Xi,j,kcan be processed using equation 2:
Gi,j,k=Xi,j,k/Xi,j,k_refEquation 2

In Equation 2, Xi,j,k_refis a 2D image map with constant luminance value. For example, the reference frequency can be used to generate Xi,j,k_refand Xi,j,kis generated using a second frequency different from the reference frequency. Gi,j,kis a gap between the measured luminance of Xi,j,k_refand a desired luminance response for Xi,j,k.

Equation 3 can be used to generate the color transform function H:

Xi,j,kref=Xi,j,kGi,j,k=C*Di,j,kGi,j,k=(CGi,j,k)*Di,j,kEquation⁢3

Equation 4 can be generated using Gi,j,kand the systems of diagrams200and210:

(1Gi,j,k)Equation⁢4

Equation 4 can then be sent to a device that incorporates the OLED display110. The results of equation 4 can be stored and used by a uniformity-gain look-up-table memory component of the device that incorporates the OLED display110. Equation 5 can be described as frequency adaptive uniformity compensation logic:

(1Gi,j,k)*Di,j,kEquation⁢5

The results of equations 4 and 5 can be used by the device that incorporates the OLED display110to compensate for differences in uniformity between different regions of the OLED display110when driven at a certain frequency. It should be appreciated that the results of equations 4 and 5 may be associated with a particular frequency, such as 90 Hz, and different results from equations 4 and 5 may be associated with a different frequency, such as 60 Hz. The different results can be used by the device that incorporates the OLED display110when driving the OLED display110at the associated frequencies.

Applying equations 4 and 5 can cause gamma and 3D color correction for the OLED display110when driven at an associated frequency. In one aspect, the equations 3, 4, and 5 can be generated for each unique display that is manufactured. Alternatively, the equations 3, 4, and 5 can be generated for a representative display that is similar to and representative of multiple displays (e.g., a group of displays) and the results of the equations 3, 4, and 5 can be applied to each of the displays. Thus, the RGB data and the compensation mask are applied to multiple displays being driven at the second frequency. The equations 3, 4, and 5 can be generated for a OLED display110before the OLED display110is incorporated into a device.

FIGS.3A,3B and3Cillustrate example diagrams300,310, and320, respectively, in which frequency compensation for a display can be implemented. Diagram300depicts the OLED display110with region302and region304. The OLED display110is driven at the reference frequency of 120 Hz. The regions302and304show no differences in uniformity.

Diagram310depicts the OLED display110with region312and region314. The OLED display110is driven at the second frequency of 90 Hz before any compensation has been applied. The regions312and314show differences in uniformity. For example, region314depicts cross hatching representing that region314is darker than region312.

Diagram320depicts the OLED display110with region322and region324. The OLED display110is driven at the third frequency of 60 Hz before any compensation has been applied. The regions322and324show differences in uniformity. For example, region322depicts cross hatching representing that region344is darker than region312.

Comparing diagrams300,310, and320demonstrates that different regions of the OLED display110react differently when the OLED display110is driven at different frequencies. After applying the techniques disclosed herein, the differences in uniformity of the regions in diagrams310and320may no longer be apparent and the regions may appear uniform.

FIG.4illustrates an example diagram of a device400in which frequency compensation for a display can be implemented. The device400may have the same features and capabilities as the electronic device102ofFIG.1. The SOC402is a system on a chip associated with the device400. The OLED display110ofFIG.1may be incorporated in the device400and can be represented by the display404.FIG.4illustrates a flow in which the techniques described herein may be implemented in the device400including the SOC402and the display404. The SOC402may include GPU406, which is a graphics processing unit configured to process display data for a display. Data from the GPU406can be sent to a color enhancement module408. Data from the color enhancement module408can be Di,j,k, as described above, and be sent to a first compensation module410. The first compensation module410can receive input from a second compensation module412, which includes applying equation 4 to the data generated in the first compensation module410. The equation 4 can be applied depending on the driving frequency (i) and the dBv values (j), different gain can be multiplied to input RGB data Di,j,k. The first compensation module410can apply equation 5. The first compensation module410can be described as frequency adaptive uniformity compensation logic.

Data from the first compensation module410can be sent to a gamma and 3D color correction module414. Data from the gamma and 3D color correction module414can be sent out of the SOC402to a data dictionary (DDIC)416associated with the display404. The DDIC416can be a display driver integrated circuit which uses the data from the gamma and 3D color correction module414to drive a panel418of the display404.

FIGS.5A and5Billustrate example diagrams500and510, respectively, in which frequency compensation for a display can be implemented. Diagram500depicts the OLED display110with regions502,504,506, and508while being driven at 90 Hz before frequency compensation is applied. The regions504,506, and508are depicted with cross hatching representing a difference in uniformity as compared to the region502. Diagram510depicts the OLED display110with regions502,504,506, and508while being driven at 90 Hz after frequency compensation is applied. The regions502,504,506, and508in the diagram510are depicted with no cross hatching representing that the regions502,504,506, and508are uniform compared to one another. The uniformity being due to frequency compensation being applied to the OLED display110. While diagrams500and510depict four distinct regions of the OLED display110, it should be appreciated that in various aspects, any number of regions for the OLED display110can be measured and frequency compensation can be applied. In one aspect, each portion of the OLED display110can be represented by a region such that the whole of the OLED display110has the potential for frequency compensation to be applied in accordance with the techniques described herein.

In one aspect, the described techniques can measure for uniformity and apply frequency compensation at portions of the OLED display110and not across the whole of the OLED display110. For example, the regions502,504,506, and508are depicted as being located at the four corners of the OLED display110. An example embodiment may measure for uniformity at the four corners such as the regions502,504,506, and508and apply frequency compensation as needed at the four corners. In such an example, sections of the OLED display110outside of the regions502,504,506, and508are not measured for uniformity and frequency compensation is not applied. Thus the compensation mask may only be applied at the regions502,504,506, and508. By measuring and applying frequency compensation to some portions of the OLED display110and not others can increase manufacturing time and efficiency. Selection of which portions of the OLED display110to apply the frequency compensation can be based on portions of displays that typically suffer from differences in uniformity, such as the four corners of the display or the bottom and top portions of the display.

Example Methods

FIG.6depicts example method600for implementing aspects of frequency compensation for a display (e.g. OLED display110). Method600is shown as a set of operations (or acts) performed but not necessarily limited to the order or combinations in which the operations are shown herein. Further, any of one or more of the operations may be repeated, combined, reorganized, or linked to provide a wide array of additional and/or alternate methods. In portions of the following discussion, reference may be made to the example device diagram100ofFIG.1, and entities detailed inFIGS.2A,2B,3A,3B,3C,4,5A, and5B, reference to which is made for example only. The techniques are not limited to performance by one entity or multiple entities operating on one device.

At step602, a display is driven at a first frequency with a control signal via a device controller, the first frequency being a reference frequency. The display can be driven at the first frequency for a first period of time. In an example, the reference frequency can be a frequency at which the manufacturer of the display guarantees uniformity between regions of the display. In one aspect, the reference frequency is 120 Hz but could be any other frequency. In one aspect, no differences of uniformity are measured between the difference regions at the reference frequency. In one aspect, the first frequency is considered a high speed frequency as compared to a second frequency, which is considered a normal or low speed frequency. For example, 120 Hz may be considered a high speed frequency, 90 Hz a normal frequency, and 60 Hz a low speed frequency.

At step604, a first uniformity is measured, at the first frequency, of multiple regions of the display in an XYZ domain at the reference frequency. The multiple regions of the display may combine to cover the whole of the display or may cover different portions of the display.

At step606, the display is driven at a second frequency with the control signal via the device controller. The display can be driven at the second frequency for a second period of time. The second period of time is different from the first period of time. The second frequency may be different from the first frequency, such as 60 Hz or 90 Hz.

At step608, a second uniformity is measured, at the second frequency, of the multiple regions of the display in the XYZ domain. At the second frequency, differences in uniformity between the different regions of the display may be measured.

At step610, a compensation mask is generated to compensate for a difference between the second uniformity and the first uniformity. The compensation mask may be calculated using the equations described above.

At step612, a color model characterization is generated based on the difference between the second uniformity and the first uniformity to generate a conversion formula. The color model characterization may be calculated using the equations described above.

At step614, data associated with the XYZ domain is converted to RGB data using the conversion formula. For example, a formula or a color conversion model can be employed to convert from XYZ data to RGB data.

At step616, the RGB data and the compensation mask are applied to the display with the display being driven at the second frequency to compensate for the difference between the first uniformity and the second uniformity. In one example, the RGB data and the compensation mask are applied to the display after the display is incorporated into a device. In another example, the RGB data and the compensation mask are applied to multiple displays being driven at the second frequency.

In one aspect, the steps of method600can be repeated for a third frequency to generate a compensation mask and RGB data unique to the third frequency.

Conclusion

Although techniques using, and apparatuses including, frequency compensation for a display have been described in language specific to features and/or methods, it is to be understood that the subject of the appended claims is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as example implementations of frequency compensation for a display.