CN111201561A

CN111201561A - Luminance decay estimation

Info

Publication number: CN111201561A
Application number: CN201780095690.5A
Authority: CN
Inventors: 冈本忠之
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2017-10-30
Filing date: 2017-10-30
Publication date: 2020-05-26
Anticipated expiration: 2037-10-30
Also published as: WO2019084729A1; CN111201561B

Abstract

The invention provides a display device. The display device includes: means for estimating the transmission transaction time by monitoring one or more representative points of the images estimated to be displayed frequently, and means for setting the compensation data for each pixel in dependence on said estimated transmission transaction time. The invention implements brightness compensation based on transmit transaction time.

Description

Luminance decay estimation

Technical Field

The present application relates to a display device, and more particularly, to brightness compensation.

Background

Generally, a high quality display device is required, and it is necessary to ensure that the luminance of each pixel is uniform. However, if all pixel and frame transmission transactions need to be calculated to determine the luminance decay, then an extra large memory area is required, which is not feasible for mobile devices. Even if not counting every transaction, but counting one of several pixels or frames, the data is still too large to fit on the mobile device, and the data is not a count of transactions, but rather an estimated source. Furthermore, previous approaches have focused on large panels such as TV displays. These devices can be loaded with very large memories due to the sufficient space available. In the related art, a method of setting a predetermined brightness for a display and a method of counting transactions are disclosed in U.S. patent application No. 2016/0275420, japanese patent application No. 2005-55880, and japanese patent application No. 2005-62485. However, existing methods do not relate to how to count transmit transactions.

Disclosure of Invention

The following description is merely exemplary in nature and is in no way intended to limit and/or restrict the present application.

A display device is provided to achieve brightness compensation based on an emission transaction time.

According to a first aspect, there is provided a display device, wherein the display device comprises: means for estimating the transmission transaction time by monitoring one or more representative points of the images estimated to be displayed frequently, and means for setting the compensation data for each pixel in dependence on said estimated transmission transaction time.

A display device is provided according to various implementations to implement brightness compensation based on emission transaction time.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is obvious that the drawings in the following description only show some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort. .

FIG. 1 shows a display screen before and after brightness compensation;

FIG. 2 shows a display device;

FIG. 3 illustrates a system for compensating a display device;

FIG. 4 shows luminance versus time;

FIG. 5 shows a schematic diagram of a mobile device;

FIG. 6 shows a system overview of transaction estimation and compensation data generation;

FIG. 7 illustrates an area to be scanned;

FIG. 8 illustrates template image extraction;

FIG. 9 shows a representative point example;

FIG. 10 illustrates representative point reduction;

FIG. 11 illustrates region separation;

FIG. 12 illustrates region separation;

FIG. 13 illustrates an obscured region; and

FIG. 14 illustrates transaction estimation based on emission counts.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. The described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without making creative efforts based on the embodiments of the present invention, belong to the protection scope of the present invention.

For display devices, maintaining uniform brightness of each pixel is an important issue. For example, pixels of a small display mounted on a mobile device may also suffer from the same problems. Compensating for brightness non-uniformity is an important issue for display devices. This is an important issue for Organic Light Emitting Diode (OLED) display devices and high definition displays suitable for mobile devices, for example.

In general, initial problems and/or errors of pixels/pixel elements can be compensated for by using camera data. Fig. 1 shows an example of image brightness non-uniformity. The example before compensation is shown on the left; the compensated example is shown on the right. In fig. 1, the luminance unevenness has been compensated.

In fig. 2, the compensation data may be supplied from the outside at the time of factory shipment and stored in a Read Only Memory (ROM) 103 connected to a Display Driver Integrated Circuit (DDIC) 102. The adder 106 may receive gamma compensation data from the gamma compensation circuit 104 and compensation data from an IP circuit 105 manufactured using an Intellectual Property (IP) core, add the data to obtain image data, and output the image data to the display apparatus 101. The display device 101 may be provided in a variety of electronic devices including, but not limited to, smart phones, mobile devices, computers, televisions, and the like. As shown in fig. 3, the sample image is displayed on a display and captured by a Charge Coupled Device (CCD) camera 110, and then compensation data is generated using an algorithm 140 installed and executed on a PC 130.

As shown in the graph of fig. 4, the brightness of the pixel may decrease by about 10% to 20% as the total usage time increases. In addition, as the total usage time increases, the luminance of the pixel having a relatively high current luminance may be lower than the initial luminance of the pixel having a relatively low current luminance.

The pixel error due to aging degradation shown in fig. 4 can be compensated for by the same method as shown in fig. 3. The method of fig. 3 employs an external device, such as a CCD camera, and therefore, it may not be easy to apply this method in a stand-alone manner.

If there are other methods and/or systems other than FIG. 4, it is generally desirable that such methods/systems be capable of measuring aging decay without the need for external equipment.

In general, the pixels of a mobile device equipped with a high resolution display may be small. Therefore, it is difficult to accurately compensate for the mobile device using the method shown in fig. 3. Furthermore, in many cases, the use environment of the mobile device is unstable, and thus the signal of the OLED pixel is generally sensitive to noise. Signal values have implications, it is necessary to understand the implications of the measurement operation of pixel errors, and measuring the Direct Current (DC) component with sufficient accuracy may require long measurement times and sophisticated sensors.

The method according to embodiments of the invention provides an accurate, fast, low-cost method to obtain a reference value for use in estimating the degree of pixel attenuation. The method can directly convert signals of OLED pixels into digital values, and therefore has noise tolerance. The sequence of processes discussed above is performed simultaneously for each row, so that short-time measurements can be achieved.

Despite the small allowed space of the electronic circuit, the mobile device has its advantages. Generally, a display device has a display driver capable of performing relatively simple processing, and an image generation processor capable of performing complex image processing exists outside the display device. For example, a personal computer main body and a display device have different housings and are connected by a display cable. The personal computer is provided with an image generation processor. The display device continuously receives and displays image signals and does not have data of the entire screen. On the other hand, the image generation processor of the mobile device is also located in the same housing as the display device, and can be processed using both the image generation processor and the display driver.

Image "aging" is a typical phenomenon that causes the above-described brightness unevenness of each pixel. As described in conjunction with fig. 4, even if the command luminance is the same, the luminance of the high-load pixel is lower than that of the low-load pixel. If one image is displayed for a relatively long time, for example, a menu bar or a clock or icon that is always displayed, the brightness of the pixels emitted for displaying the image becomes low and the outline of the image is visible when another image is displayed. Such images are typically fixed and stable, so the images themselves can be used as template images to statistically estimate the transmission transactions, and these images facilitate the generation of compensation data, particularly for estimated aging images.

In one embodiment, an original image to be aged is detected and used as a template image with attenuation weights. If a representative point can be set on the original image and the transaction at that point can be counted, a transaction estimation can be made for the area where image aging is likely to occur. The actual transmit transaction may include some other transmission of other images but is statistically negligible because image aging is only visible at very high loaded pixels for a Low Temperature Polysilicon (LTPS) backplane.

Fig. 5 shows a schematic diagram of a mobile device 200. In addition to the display apparatus 101, the DDIC 102 and the ROM 103 described in conjunction with fig. 2, the mobile apparatus 200 includes a RAM 104 connected to the DDIC 102, a Central Processing Unit (CPU) 201, and a Random Access Memory (RAM) 202 and a ROM 203 connected to the CPU 201. The ROM 103 and the RAM 104 may be integrated in the DDIC 102 and have a relatively small memory area. Mobile device 200 may be a smartphone. The CPU201 may be a chipset including a Graphics Processing Unit (GPU), a Digital Signal Processor (DSP), a communication processor, and the CPU201 itself. The RAM 202 may be dynamic random access memory, while the ROM 203 may be non-volatile memory. The RAM 202 and the ROM 203 may have a relatively large storage area in order to execute various system programs and application programs. The RAM 202 may include a frame memory for storing data of the entire screen to be displayed.

FIG. 6 shows an overview of a system for transaction estimation and compensation data generation in view of functional relationships. Each function may be implemented on hardware, such as DDIC 102 in fig. 5, or may be implemented using one or more processors, such as CPU201 and one or more computer programs in fig. 5. In one example, simple but always-running functions such as "heavy duty detector (HD)" and "Transaction counter for representative point" (TC) as described below are executed using fixed hardware logic on the DDIC 102, while functions that are complex but run only in the case of receiving an Interrupt Request (IRQ) or the like call, such as "Pattern analyzer" (PA) including "template image extractor" and "compensation data generator" as described below, are executed on the CPU 201. The allocation of functions to hardware and software in fig. 6 is only one example. In another example, all functions may be performed by software. Instead of the IRQ, a warning message may be sent from DDIC 102 to CPU 201. The above function will be described in detail below.

< Heavy load Detector (HD) executed on DDIC >

This is a detection function of a potential overload point, in other words a pixel that is estimated to be emitted at a relatively high brightness and/or for a relatively long time. HD is only concerned with searching for these points and does not require a memory for accumulating transaction counts per pixel. When a potential load point is detected, the HD sends an IRQ to another function, which is executed by a separate sequencer or CPU using an algorithm.

The HD scans each divided area in order and sums the instructed luminance of each pixel based on a scanning signal and an emission signal for specifying the pixel, a data signal for indicating the luminance, and a signal for specifying a color of red, green, blue, or the like. The scan rate must not be too low to prevent skipping the detection of a flickering image. When the possible flicker frequency is 1Hz, at least a double frequency of 2Hz is required. As shown in fig. 7, the scan area may be divided to store the memory area. By dividing into small areas and scanning each area in sequence, the entire display area can be covered. For example, for a full high definition (FHD, 1920x1080) panel scanned once every 120 lines, the necessary memory area would be 1/16 (fig. 7) for scanning the memory area of the undivided display area. In the example of fig. 7, HD attempts to detect the excess emission of each divided region within one minute at the scan rate described above. In another embodiment, a particular region, such as a "menu bar" region or a "fixed icon" region, may be frequently selected as a scanning region. The PA may set the frequency to be scanned.

The frequency at which the IRQ is sent to the PA is preferably limited, e.g., once per scan of each area. Further, skipping scanning of an occlusion region containing an image corresponding to a template image is effective to prevent repeated IRQ, provided that the image corresponding to the template image is displayed at a specific position on the screen and the image is stable, i.e., does not change. The PA may contain masked areas to perform such processing. As shown in fig. 8, the function may hold a plurality of coordinates of the masked area in each scanned area. The masked area is fixed by the PA and notified to the HD.

For example, the condition for IRQ to be sent to PA may be set as follows:

(for each pixel) "the sum of the command luminances" is greater than "a specific value that may cause aging", or

(for each scan area) "the number of points at which the sum of the command luminances exceeds a predetermined value" is greater than "a specific number".

The sum of the command luminances may be a coarse value, for example only the upper bits of the command luminances may be summed to save a memory area in the RAM 104, since the HD is only concerned with the detection of possible load points, and the precise compensation data is determined by another function.

< Pattern Analyzer (Pattern analyzer, PA): algorithm executed by a computer program running on a CPU >

The function extracts template images around possible points of overload detected by the HD, determines whether the images have a possibility of aging, and selects representative points from which images corresponding to the template images can be identified. A "template image extractor" that may be included in the PA extracts the template image by accessing the frame memory in the RAM 202. The template image is the most important information for accurate compensation. Various image processing techniques may be employed to extract the template image.

How to judge the possibility of aging and how to determine the template image are described below. When receiving the IRQ from the HD, the PA extracts the contours of the image around the detected possible loading point. When the commanded brightness within the image contour is stable over several frames, then the pattern of gears, etc. in FIG. 8 is likely to age and is considered part of the template image. If another stable image exists around the contour, such as the rounded square in FIG. 8, then this image is also part of the template image. A rectangular area including a gear and a rounded square and possibly corresponding to the setting icon is stored as a template image in the ROM 203.

After the PA determines the template image, points to be monitored are selected, which represent the image. In order to distinguish the image corresponding to the template image from other images, it is desirable to ensure that the dots uniquely identify the image corresponding to the template image. The representative points may be fixed as follows:

-a most stable point;

-brightest/dark spot;

-if the template image is planar, the center of the template image or outline; or

-the point in the template image that is furthest from the other monitoring point.

If the PA infers that 3 points are needed to identify the image corresponding to the template image, the PA assigns 3 points of the image corresponding to the template image to TC. Fig. 9 shows three examples of allocation of 3 points, respectively. The left image is a set icon with representative points at the gear center, on the gear, and on the upper left of the gear. The middle image is a flower icon, and representative points are distributed on the center, the petals and the left lower side of the flower. The right image is a weather icon, and representative points are distributed in the sun center, the cloud center and below the cloud.

In one embodiment, additional points to be monitored are placed for the first time, the points decreasing over time. For example, when the PA assigns 3 points for the first time to monitor a particular icon and the contour values of these 3 points are almost the same for a long period of time, e.g., several days, then over time the representative points can be reduced to 1, except for the most unique one, i.e., assigned to the gear center, as shown in fig. 10.

As shown in fig. 11, the template image may contain separate data for images that change over time (like a clock or battery icon). The PA may process the image contour separately and set several counters for the respective areas. In fig. 11, it is assumed that representative points are allocated on four rectangles and at the lightning center in the case where the counter value of the lightning center is the same as the counter value of the battery shape. As shown in fig. 12, the PA may identify different regions based on different respective counter values.

Assuming that the template image is displayed at a specific position on the screen and the image is stable, i.e., does not change, PA sets a mask region covering the outline of the image to HD as shown in fig. 13 after the above procedure becomes stable and the counter value of TC coincides with the detection value of HD. To handle simple hardware detectors, the shape of the masked-area is preferably simple, e.g., square or rectangular, etc. After the template image is fixed, the mask pattern including the mask coordinates should be registered in the HD.

< Transaction Counter (TC) executed on DDIC >

This is a simple counter for the PA to determine the representative point. The TC need only count the emission transactions of the image corresponding to the template image, and need not count the transactions per pixel and per frame. In the present embodiment, the transaction count of the template image can be easily estimated by setting one or more representative points on the template image. This function operates through parameters input to an algorithm executed by a computer program running on the CPU201 as follows:

—ID；

-point coordinates (X, Y);

-the RGB value of point (R, G, B), the counter being incremented when the RGB value of point (X, Y) matches; and is

-counting the full number (Nc), when the counter value exceeds Nc, IRQ is sent to CPU 201;

-a sampling period.

In this embodiment, the TC monitors the representative point by these parameters. When the commanded brightness is the same as the "RGB value" at point (R, G, B), TC calculates the total

When the CPU201 estimates a transmission transaction for a specific area, or receives an IRQ whose counter is full, the CPU201 inquires the counter value of the TC and calculates the level of the transmission transaction time, as shown in fig. 14. Fig. 14 shows that the transmit transaction amount is estimated based on the transmit count of the representative point. From this level, the "compensation data generator" shown in fig. 6 generates compensation data values based on the relationship of luminance with time shown in fig. 4 and updates the ROM 103 according to these values.

The method can estimate the transmit transaction time to weight the compensation value. In addition, the method compensates for image aging and improves image uniformity of the OLED display. Embodiments of the present invention implement illumination compensation based on transmit transaction time.

The method is particularly applicable to Augmented Reality (AR)/Virtual Reality (VR) and gaming applications where the image is generated by a processor on the same system as the display.

The foregoing disclosure is only illustrative of the present invention and is, of course, not intended to limit the scope of the invention. It will be understood by those of ordinary skill in the art that all or a portion of the flow chart for implementing the above embodiments and equivalent modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims

1. A display device, comprising:

means for estimating the time of the transmission transaction by monitoring one or more representative points of the images estimated to be displayed frequently, an

Means for setting compensation data for each pixel according to the estimated transmit transaction time.

2. The apparatus of claim 1, wherein estimating the image that is displayed often and has a heavy load comprises an outline of the image around one or more points.

3. The apparatus of claim 1 or 2, further comprising: means for reducing the representative points if the monitoring results of the representative points are substantially the same.

4. The apparatus of any of claims 1 to 3, further comprising: means for dividing the image estimated to be frequently displayed in a case where the monitoring results of the representative points are different.

5. A display method, comprising:

the processor estimates the transmission transaction time by monitoring one or more representative points of the images estimated to be displayed frequently, an

The processor sets compensation data for each pixel according to the estimated transmit transaction time.

6. The method of claim 5, wherein estimating the image that is displayed often and has a reload comprises the outline of the image around one or more points.

7. The method of claim 5 or 6, further comprising:

the processor decreases the representative point if the monitoring results of the representative points are substantially the same.

8. The method of any of claims 1 to 3, further comprising:

if the monitoring results of the representative points are different, a processor divides the image estimated to be frequently displayed.

9. An electronic device characterized by comprising the display device according to any one of claims 1 to 4.

10. A computer program, characterized in that it causes a processor to execute the method according to any of claims 5 to 8.