Method and system for stress compensation in display device

Abstract

The present invention relates to a method and system for compensating stress in a display device. The method for compensating stress in a display device includes: obtaining, by a decoder, compressed stress data quantized by a quantization value; decoding, by the decoder, the compressed stress data to generate decoded data; generating a dither value based on the quantization value; and adding the dither value to the decoded data to compensate for the quantization of the compressed stress data.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of U.S. Provisional Patent Application Serial No. 62 / 902,284, filed on September 18, 2019, and entitled “UNBIASED ITERATIVE COMPRESSION ON ADDITIVE DATA USING DITHER,” the entire contents of which are hereby expressly incorporated by reference.

[0003] This application is also related to U.S. patent application serial number 15 / 979,279, filed on May 14, 2018, and entitled “STRESS PROFILE COMPRESSION,” which claims priority to and the benefit of U.S. provisional patent application serial number 62 / 643,622, filed on March 15, 2018, and entitled “STRESS PROFILE COMPRESSION,” the entire contents of which are hereby expressly incorporated by reference. Technical Field

[0004] Aspects of the present disclosure relate to stress compensation or image sticking or ghosting effects in display devices. Background Art

[0005] Compensation for output droop in video displays, such as organic light-emitting diode (OLED) displays, can be used to maintain image quality as the display ages. The data used to perform this compensation can be stored in a compressed form to reduce memory requirements; however, errors in this compressed data can accumulate unevenly, resulting in a loss of image quality.

[0006] Furthermore, when OLED displays display static images for extended periods, they can suffer from afterimages. As a result, once the static image is removed or altered, the user may still see a blurred outline or ghosting of the original image, even after the image content has changed. This is commonly referred to as image persistence, afterimages, or image ghosting. The same approach as for stress distribution applies to image persistence.

[0007] Therefore, there is a need for an improved system and method for stress compensation to reduce or eliminate output droop in OLED display devices.

[0008] The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not constitute prior art. Summary of the Invention

[0009] This summary is provided to introduce a selection of features and concepts of embodiments of the present disclosure that are further described in the detailed description below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. One or more of the described features can be combined with one or more other described features to provide a viable device.

[0010] Aspects of example embodiments of the present disclosure relate to systems and methods for reducing or eliminating display output degradation by mitigating the effects of pixel degradation / aging in display devices.

[0011] Aspects of example embodiments of the present disclosure relate to systems and methods for utilizing dithering to compensate for quantization noise in iterative compression of added data.

[0012] According to some embodiments of the present disclosure, a method for stress compensation in a display device is provided, the method comprising: obtaining, by a decoder, compressed stress data quantized by a quantization value; decoding, by the decoder, the compressed stress data to generate decoded data; generating a jitter value based on the quantization value; and adding the jitter value to the decoded data to compensate for the quantization of the compressed stress data.

[0013] In some embodiments, generating the dither values ​​and adding are performed by the decoder or circuitry external to the decoder.

[0014] In some embodiments, the quantized value is a power of two, the quantized value is stored in a header of the compressed stress data, and the compressed stress data corresponds to a luminance value of a slice of a frame of pixel data to be displayed on a display device.

[0015] In some embodiments, generating the jitter value is further based on a previous jitter value corresponding to the compressed stress data, wherein the previous jitter value is stored in a header of the compressed stress data.

[0016] In some embodiments, generating the dither value includes utilizing a uniform pseudo-random number generator.

[0017] In some embodiments, generating the dither value comprises: determining, by the decoder, that the quantization value is equal to 1; and in response, outputting, by the decoder, the dither value as zero.

[0018] In some embodiments, generating the dither value comprises: determining, by the decoder, a quantization value equal to 2; and in response, outputting, by the decoder, the dither value as a modulus of the quantization value and a previous dither value plus one.

[0019] In some embodiments, generating the dither value comprises outputting, by the decoder, the dither value as a modulus of a first value and a quantized value, wherein the first value is calculated as a previous dither value added to half the quantized value minus one.

[0020] In some embodiments, the method further comprises storing, by the decoder, the jitter value in a header of the decoded data.

[0021] According to some embodiments of the present disclosure, a method for stress compensation in a display device is provided, the method comprising: compressing, by an encoder, first accumulated stress data with quantization corresponding to a quantization value to generate compressed accumulated stress data; storing, by the encoder, the compressed accumulated stress data in a memory; obtaining, by a decoder, the compressed accumulated stress data and decompressing the compressed accumulated stress data to generate decoded data; generating, by the decoder, a jitter value based on the quantization value; and adding, by the decoder, the jitter value to the decoded data to compensate for the quantization of the first accumulated stress data.

[0022] In some embodiments, the method further includes: receiving, by the stress capture module, an output image to be displayed on a display device; and calculating, by the stress capture module, second stress data based on the output image.

[0023] In some embodiments, the method further includes: receiving, by the adding circuit, second stress data corresponding to an image data frame to be displayed on a display device; and adding, by the adding circuit, the decoded data and the second stress data to generate updated accumulated stress data.

[0024] In some embodiments, the method further includes compressing, by the encoder, the updated accumulated stress data for storage in the memory.

[0025] In some embodiments, generating the dither value is further based on a previous dither value corresponding to the first accumulated stress data, and wherein the previous dither value corresponds to a slice of the pixel data frame that is different from a slice of the pixel data frame that corresponds to the second stress data.

[0026] In some embodiments, the first accumulated stress data corresponds to a luminance value of a slice of a frame of pixel data to be displayed on a display device.

[0027] In some embodiments, generating the dither value is further based on a previous dither value corresponding to the first accumulated stress data, and wherein the quantized value and the previous dither value are stored in a header of the compressed accumulated stress data.

[0028] In some embodiments, generating the dither value includes: determining, by the decoder, a quantization value; and in response to determining that the quantization value is equal to 1, outputting, by the decoder, the dither value as zero; or, in response to determining that the quantization value is equal to 2, outputting, by the decoder, the dither value as a modulus of the quantization value and a previous dither value plus one.

[0029] In some embodiments, generating the dither value comprises outputting, by the decoder, the dither value as a modulus of the first value and the quantized value, and wherein the first value is calculated as a previous dither value added to half the quantized value minus one.

[0030] In some embodiments, the method further comprises storing, by the decoder, the jitter value in a header of the decoded data.

[0031] According to some embodiments of the present disclosure, a system for performing stress compensation in a display device is provided, the system including: a memory; and a processing circuit configured to perform: obtaining compressed stress data quantized by a quantization value; decoding the compressed stress data to generate decoded data; generating a jitter value based on the quantization value; and adding the jitter value to the decoded data to compensate for the quantization of the compressed stress data. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] These and other features of some example embodiments of the present disclosure will be appreciated and understood with reference to the specification, claims, and drawings, in which:

[0033] Figure 1 illustrates example embodiments of a display device according to some example embodiments of the present disclosure;

[0034] Figure 2 illustrates a block diagram of a system for stress compensation according to some embodiments of the present disclosure;

[0035] Figure 3A illustrates a block diagram of an encoder according to some example embodiments of the present disclosure;

[0036] Figure 3B illustrates a block diagram of a decoder according to some example embodiments of the present disclosure;

[0037] Figure 4 illustrates a process of stress compensation via a decoder in a display device according to some example embodiments of the present disclosure; and

[0038] Figure 5 A process of stress compensation in a display device according to some example embodiments of the present disclosure is illustrated. DETAILED DESCRIPTION

[0039] The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of some example embodiments of the systems and methods for mitigating the effects of compression errors provided in accordance with the present disclosure, and is not intended to represent the only form in which the present disclosure may be constructed or utilized. This description sets forth features of the present disclosure in conjunction with the illustrated embodiments. However, it is to be understood that the same or equivalent functions and structures may be implemented by different embodiments that are also intended to be included within the scope of the present disclosure. As indicated elsewhere herein, the same reference numerals are intended to indicate the same elements or features.

[0040] Certain types of display devices may have characteristics that change with use. For example, an organic light emitting diode (OLED) display device may include a display panel having a plurality of pixels, each pixel including a number of sub-pixels (e.g., a red sub-pixel, a green sub-pixel, and a blue sub-pixel), and each of the sub-pixels may include an organic light emitting diode configured to emit a different corresponding color. Each organic light emitting diode may have optical efficiency that decreases with use, so that, for example, after the organic light emitting diode has been operated for some time, the optical output at a certain current may be lower than the optical output at the same current when the organic light emitting diode was new.

[0041] This reduction in optical efficiency may cause portions of the display panel that uniformly display brighter portions of the displayed image than other portions of the display to dim over the lifetime of the display device. For example, a display device used to view a largely unchanging image from a security camera (where the security camera's field of view includes a scene having a first portion, the first portion being sunlit and relatively bright during most of the day, and a second portion being in shadow and relatively dim during most of the day) may eventually show a more significant reduction in optical efficiency in the first portion than in the second portion. As a result, the fidelity of image reproduction by such a display device may degrade over time. As another example, a display device that partly displays white text at the bottom of an image (separated from the rest of the image by a black border) may experience less reduction in optical efficiency in the black border than in other portions of the display panel. Consequently, if the display device is later used in a mode where the scene fills the entire display panel, a brighter band may appear where the black border was previously displayed. This may be referred to as image persistence or image ghosting.

[0042] To reduce the impact of such non-uniformities on the optical efficiency of a display device, the display device may include features to compensate for the reduction in optical efficiency resulting from use of the display.

[0043] Figure 1 An example embodiment of a display device 100 according to some example embodiments of the present disclosure is illustrated.

[0044] refer to Figure 1 , the display device 100 may include a display panel 110, a processing circuit 115 (e.g., a processor or central processing unit (CPU)), and a memory 120. The memory 120 includes data that may be referred to as a “stress profile” or “stress table” for the display device 100. The “stress profile” or “stress table” stored in the memory 120 may be a table of numbers or “stress values” that indicate the amount of stress to which each sub-pixel in the display device 100 has been subjected during the lifetime of the display device 100. “Stress” may be the sum of the total (e.g., time-integrated) drive current or displayed luminance values ​​that has flowed through each sub-pixel during the lifetime of the display device 100. For example, “stress” may be the total charge that has flowed through each sub-pixel during the lifetime of the display device 100.

[0045] In some example embodiments, the method of determining the "stress distribution" may be a data-driven method for compensating for a drop in OLED output. In some example embodiments, to determine the "stress distribution" of the display device 100, the memory 120 may accumulate a number for one or some sub-pixels as a new entry in a "stress distribution" or "stress table" for the display device 100 each time a new image is displayed in the display device 100. For example, when a continuous stream of images together forms a displayed video in the display device 100, the driving current for each sub-pixel in each image may be measured, and the number indicating the current or brightness of the sub-pixel may be added to the corresponding number or "stress" for the sub-pixel in the "stress distribution" or "stress table" in the memory 120. In some examples, the stress value for each sub-pixel may be calculated as the sum of the brightness values ​​displayed by the sub-pixels.

[0046] In some example embodiments, the display device 100 includes a timing controller and a plurality of driver integrated circuits (e.g., a scan / gate driver and a data driver). The processing circuit 115 may be one or more driver integrated circuits, or may be part of one or more driver integrated circuits. In some embodiments, each driver integrated circuit is responsible for driving a portion of the display panel 110, and therefore, it can perform stress accumulation and stress compensation on that portion independently of other driver integrated circuits.

[0047] In some example embodiments, during operation of the display device 100, the drive current to each subpixel may be adjusted to compensate for an estimated loss in optical efficiency. The estimated loss in optical efficiency may be based on the lifetime stress of the subpixel. For example, the drive current to each subpixel may be increased (e.g., as accumulated in the memory 120) based on the estimated loss in optical efficiency of the subpixel (e.g., proportional to the estimated loss in optical efficiency of the subpixel), so that the optical output of the subpixel may be substantially the same as it would have been if the optical efficiency of the subpixel had not decreased and the drive current had not increased. In some example embodiments, a nonlinear function based on empirical data or a physical model of the subpixel may be used to infer or predict the expected loss in optical efficiency based on the lifetime stress of the subpixel. The calculation of the predicted loss in optical efficiency and the corresponding adjusted drive current may be performed by the processing circuit 115. In some embodiments, the calculation results are stored in a lookup table in the memory, and the processing circuit 115 may use it for compensation. In some example embodiments, during operation of the display device 100 , a driving current to each sub-pixel may be adjusted according to a compensation factor that may be calculated based on cumulative luminance captured from an output image of the sub-pixel.

[0048] Figure 2A block diagram of a system 200 for stress compensation according to some embodiments of the present disclosure is shown. System 200 includes a memory 205 (which may be the same as or part of memory 120), a compensation module 210, a stress capture module 215, an adder circuit 220, and a memory controller 225. A stress table is stored in memory 205. In operation, stress values ​​in the stress table can be accessed (e.g., read out) via memory controller 225 and used by compensation module 210 to determine compensation factors for subpixels. Compensation module 210 may include drive current adjustment circuitry to calculate an adjusted drive current value for each subpixel based on the corresponding compensation factor for that subpixel. The compensation factor for each subpixel is based on the stress value for that subpixel. In some example embodiments, the adjusted drive current value for each subpixel may be a raw drive current value adjusted based on the accumulated stress of the subpixel (e.g., based on the desired optical output of the subpixel). The adjusted drive current value for each subpixel is read by stress capture module 215, which may include subpixel stress sampling circuitry. The adjusted drive current value for each sub-pixel represents the current rate of accumulation of stress for the sub-pixel being displayed. Each previously stored (e.g., in memory 205) stress value for each sub-pixel is increased (or "enhanced") in summing circuit 220 based on the current rate of accumulation of stress (e.g., by a number proportional to the adjusted drive current value) and saved back to memory 205 via memory controller 225. Memory controller 225 controls read and write operations in memory 205 and feeds stress values ​​from memory 205 to the drive current adjustment circuit of compensation module 210 and to summing circuit 220 as needed. Memory controller 225 also stores the enhanced stress value (which has been enhanced by adding the current rate of accumulation of stress at summing circuit 220) back to memory 205.

[0049] In some example embodiments, tracking the total stress for each sub-pixel can require a significant amount of memory. For example, for a display with 1920x1080 pixels, each pixel having three sub-pixels, and the stress for each sub-pixel stored in a few bytes, the required memory size can be on the order of tens of megabytes. Furthermore, the computational burden of updating each stress figure for each sub-pixel for each frame of video (e.g., for each displayed image) is considerable.

[0050] Various methods can also be used to reduce the memory size required to store sub-pixel stresses in the stress table. In some embodiments, the memory on the stress distribution chipset is reduced by compressing the data stored in the memory.

[0051] According to some embodiments, the system 200 further includes a first decoder 230a, an encoder 235, and a second decoder 230b. In some example embodiments, a compressed representation of the stress table is stored in the memory 205. In operation, the compressed stress data can be accessed (e.g., read out) via the memory controller 225 and can be decompressed by the first decoder 230a before being fed to the drive current adjustment circuit of the compensation module 210. The drive current adjustment circuit of the compensation module 210 calculates an adjusted drive current value for each sub-pixel based on the corresponding compensation factor for that sub-pixel. The compensation factor for each sub-pixel is based on the stress value of the sub-pixel. The adjusted drive current value for each sub-pixel is read by the stress capture module 215. The adjusted drive current value for each sub-pixel represents the current accumulation rate of stress for the sub-pixel being displayed. The compressed stress data in the memory 205 is also decompressed by the second decoder 230b to obtain each previously stored (e.g., in the memory 205) stress value for each sub-pixel. The decompressed stress values ​​for the subpixels from the second decoder 230b are sent to the summing circuit 220. Each previously stored stress value for each subpixel is increased (or "boosted") in the summing circuit 220 based on the current accumulation rate of stress (e.g., by a number proportional to the adjusted drive current value). The boosted stress values ​​from the summing circuit 220 are compressed by the encoder 235 before being stored in the memory 205. The encoder 235 compresses the data it receives in a manner that reduces the size of the stored data. In some examples, the compression applied by the encoder 235 may be lossy in order to reduce (e.g., minimize) the memory capacity consumed by the compressed data. Each of the first decoder 230a and the second decoder 230b decompresses the received data. For example, each of the first decoder 230a and the second decoder 230b performs an operation that is the inverse or approximately the inverse of the operation performed by the encoder 235. Various compression methods can be employed, including entropy coding such as Huffman coding or arithmetic coding.

[0052] In some examples, the output of the first decoder 230a may be truncated to discard the less significant bits of the decoded value. This may be done due to the fact that, although the less significant bits are used to accurately measure the accumulated stress, they may not substantially affect the compensation performed by the compensation module 210.

[0053] According to some embodiments, encoder 235 and first and second decoders 230a and 230b operate on data units called slices. A slice is an independently coded unit of image data representing a portion of an image. For example, a slice can be a portion spanning the entire width of an image and four vertical lines. Each iteration of the encoding / decoding process described above can be performed on one slice of image data.

[0054] Although the first decoder 230a and the second decoder 230b Figure 2 2 has been illustrated as two separate circuits, but embodiments of the present disclosure are not limited thereto. For example, the first decoder 230a and the second decoder 230b can be combined into one decoder circuit. In some examples, the second decoder 230b can be omitted, and the output of the first decoder 230a can be provided to the adding circuit 220. Hereinafter, the combination of the encoder 235, the adding circuit 220, and one or more of the first decoder 230a and the second decoder 230b is referred to as a "codec device."

[0055] Figure 2 The system 200 can reduce the amount of memory required to store sub-pixel stresses in the stress table. However, due to the iterative nature of the system, errors can accumulate in the memory or stress table compared to a system that does not use compression. The iterative additive nature of the stress distribution can cause compression and decompression errors to accumulate from one iteration to the next. Therefore, unless carefully controlled, compression errors, which may be quantization errors, can accumulate and may result in significant compensation factor errors for some portions of the image. Some embodiments of the present disclosure compensate for the accumulation of errors by utilizing a specific dither at the first decoder 230a / second decoder 230b.

[0056] Figure 3A A block diagram of the encoder 235 is illustrated according to some example embodiments of the present disclosure. Figure 3B A block diagram of the decoder 230 is illustrated according to some example embodiments of the present disclosure. Figure 3B The decoder 230 can be used with Figure 2 The first decoder 230a and / or the second decoder 230b are identical or substantially identical. Figure 3A and Figure 3B In the example, X and Y represent the column index and row index of the slice, respectively.

[0057] refer to Figure 3AAccording to some embodiments, encoder 235 includes a quantizer 305 and an entropy encoder 310. Quantizer 305 may be a uniform quantizer with exponential quantization and may have the effect of zeroing the m (a positive integer) least significant bits of the input value, thereby removing m bits from the bit line. Therefore, the operation of quantizer 305 is inherently lossy. Here, the input value may be the accumulated stress data for a slice of an image data frame / pixel data frame received from stress capture module 215. Entropy encoder 310 may include any lossless encoding method such as arithmetic coding, Huffman coding, etc. Entropy encoder 310 may also include median adaptive prediction. Quantization allows for full control over the amount of loss in the system prior to encoding. For example, the value of m allows encoder 235 to control the amount of error caused by the encoding operation of encoder 235. In some examples, encoder 235 may determine the exponential quantization parameter m through an iterative process. For example, the value m may be initially set to a first value (e.g., 1) and increased until a desired compression ratio (e.g., a 4-to-1 compression ratio) is achieved by encoder 235. According to some embodiments, the resulting value of m is stored (eg, saved in a header of the encoded data) for later use by the decoder 230 .

[0058] In some embodiments, the decoder 230 includes an entropy decoder 315, a dither generator 320, and an adder 325. The entropy decoder 315 may be a lossless decoder (e.g., an arithmetic decoder or a Huffman decoder) that performs the inverse operation of the entropy encoder 310. In some embodiments, the entropy decoder 315 includes a decoder configured to multiply its input by 2. m Scaler, 2 m is the quantized value used by the encoder 235. The adder 325 adds the output of the entropy decoder 315 and the output of the dither generator 320.

[0059] In practice, the combined operation of the quantizer 305 and the entropy decoder 315 can be formulated by equation (1):

[0060]

[0061] Where x represents the input value (such as the obtained stress value), m represents the exponential quantization parameter, represents the bit operations performed by the quantizer 305 of the encoder 235, and 2 m The multiplication is performed by the entropy decoder 315 of the decoder 230, and q ′ m (x) represents the quantized value of x.

[0062] The quantization operation and the scaling operation have characteristics that can be expressed by equation (2):

[0063] q ′m (q ′ m (x))=q ′ m (x) Equation (2)

[0064] In other words, successive iterations of application of quantization and scaling do not increase further error.That is, the codec device is idempotent (ie, successive operations of the decoder-encoder operation do not change the result beyond the initial application) or substantially idempotent.

[0065] According to some embodiments, the dither generator 320 generates and outputs dither (eg, quantization constrained dither) that is added to the output of the entropy decoder 315 via the adder 325. The dither may be based on the quantization value n=2 m Calculated uniform dither. The dither values ​​can be {0, 1...n-1}. As will be described below, due to the nature of the encoding algorithm, the added dither results in an unbiased addition of stress values ​​(ie, an addition that does not accumulate quantization errors).

[0066] In some embodiments, the same dither value is added to the decompressed stress value of all pixels in the same slice. This ensures that additional entropy is not introduced by the next addition operation of the next iteration of the codec device. This is because the added dither is more useful in time (each iteration) than in space. If the dither is different in space for different pixels, it will unnecessarily introduce additional noise that is more difficult to compress. For example, if different dither values ​​are used within the same slice, the brightness values ​​of pixels in flat areas may be different after further addition and quantization. In some examples, even for the same quantization value, the dither will vary from slice to slice because each slice is processed independently and the start of the dither sequence is based on when the quantization changes and is independent of other slices. In effect, dithering allows the codec to effectively subsample the addition performed by the addition circuit 220 while maintaining an unbiased estimate. This can be mathematically illustrated as follows.

[0067] You can also The case is shown:

[0068] e[q n (X+c)]=c Equation (3)

[0069] Where n is the quantized value 2 m , c is a non-negative integer representing the stress value of a single sub-pixel (e.g., the red sub-pixel, the green sub-pixel, or the blue sub-pixel of the pixel) for a given iteration calculated by the stress capture module 215, X is a random variable between 0 and n-1 representing the dither value, and E[q n(X + c)] is the expected value of the quantized stress value that can be stored at the memory 205. As an example, if the quantized value n is equal to 4 and c is equal to 1, then in the absence of dither (i.e., without the random variable X), the expected value described by equation (3) is 0; however, in the presence of dither, the expected value is c = 1. In other words, with the addition of dither, the expected value of the quantized / compressed stress value stored in the memory is the same as the uncompressed stress value.

[0070] Further, it can be shown that:

[0071]

[0072] in, is between 0 and n i -1, i is a natural number representing the current iteration, n i is a natural number greater than 1, represents the compressed value obtained from the memory 205, c i-1 is the captured stress value corresponding to the acquired quantized stress value, is the previous jitter value corresponding to the acquired quantized stress value, c i is the newly added stress value from the stress capture module 215, and is the new jitter value.

[0073] Equation (4) is an expression for the expected value of the stored stress values ​​for two consecutive iterations. However, even when extended to an arbitrary number of iterations, the overall conclusion is that, according to some embodiments, the expected value of the accumulated stress value after compression is the same as the accumulated value in its uncompressed form. This is due to the application of the quantization value based on 2 m Thus, the added dither can compensate for the quantization effect of the encoder 235. As a result, the combination of the encoder 235 and the decoder 230 can be used as an unbiased estimator for the composite addition of stress values.

[0074] In some examples, encoder 235 can store the quantization value in the header of the encoded data, and decoder 230 can recover the dither value in the header of the decoded data. Thus, it may not be necessary to track the number of iterations. In this way, decoder 230 can always identify the previous quantization value and the previous dither value that decoder 230 can use to determine the dither value in the current iteration.

[0075] According to some embodiments, when the decoder 230 determines that no quantization was applied in the previous iteration (eg, determining the exponential quantization parameter m=0 or the quantization value 2 m=1), the dither value is set to zero and no dithering is applied to the encoded data. When the decoder 230 determines that the quantization value is equal to 2 (i.e., m=1), the decoder 230 calculates the current dither value as the modulus or remainder of the previous dither value plus one divided by the integer of the quantization value. Otherwise (i.e., m>1), the decoder 230 calculates the dither value as the previous dither value divided by 2. m-1 -1 is added to the modulus of the quantized value. Although a slice of the data can use a single dither value, it can be shown that by using 2 m-1 If all dither values ​​are added modulo -1, all dither values ​​will be used (over multiple iterations) for a given quantized value, as long as the quantization step size does not change between iterations. If not all values ​​are used, then over multiple iterations the result of the addition and quantization step size may deviate from the actual value. In general, the dither sequence only needs to conform to a uniform pseudorandom number sequence based on the quantization step size to support unbiased iterative addition. The above description is only one possible approximation for maintaining the state of the pseudorandom number (PRN) generator without requiring additional information in the header; embodiments of the present invention are not limited thereto. For example, rather than "jumping" around all dither values ​​as done above, it is possible to advance through the possible dither values ​​in a linear manner.

[0076] According to some embodiments, the calculation of the dither value based on the quantized value and the previous dither value (ie, the dither value of the previous iteration) can also be expressed in pseudo code as:

[0077]

[0078]

[0079] Thus, according to some embodiments, by using quantization-constrained dithering, the codec can compress / quantize the accumulated stress value data without additive bias. This also allows for dynamic changes in quantization to match memory requirements. The methods and systems according to some embodiments of the present disclosure can be easily implemented because they do not require knowledge of the output values ​​of the decoder or previous values ​​input to the encoder.

[0080] Figure 4 A process S400 of stress compensation via the decoder 230 in the display device according to some example embodiments of the present disclosure is illustrated.

[0081] refer to Figure 4 According to some embodiments, the decoder 230 obtains (S402) the quantized value 2 from the memory 205. mQuantized compressed stress data. The decoder 230 decodes the compressed stress data to generate decoded data (S404), and generates a jitter value based on the quantized value (S406). In some embodiments, the jitter value is further based on a previous jitter value from a previous iteration corresponding to the compressed stress data. The previous jitter value and the quantized value can be stored in the header of the compressed stress data. In this way, it may not be necessary to track the number of iterations that the cumulative stress data has experienced. The generation of the jitter value can be completed by approximation of the previous jitter value and the quantized value by a uniform random number generator (e.g., a uniform pseudo-random number generator). In some embodiments, the decoder 230 adds the jitter value to the decoded data to compensate for the quantization of the compressed stress data (S408).

[0082] Figure 5 A process S500 of stress compensation in a display device according to some example embodiments of the present disclosure is illustrated.

[0083] refer to Figure 5 According to some embodiments, the encoder 235 generates a quantized value 2 m The first accumulated stress data is compressed by the corresponding quantization to generate compressed accumulated stress data (S502). The first accumulated stress data may correspond to the brightness value of a slice of the pixel data frame to be displayed on the display device 100. In some embodiments, the encoder 235 stores the compressed accumulated stress data in the memory 205 (S504). The decoder 230 then obtains the compressed accumulated stress data and decompresses the compressed accumulated stress data to generate decoded data (S506). In some embodiments, the decoder 230 decompresses the compressed accumulated stress data based on the quantization value 2 m A dither value is generated (S508), and the dither value is added to the decoded data to compensate for quantization of the first accumulated stress data (S510). The generation of the dither value may be further based on a previous dither value from a previous iteration corresponding to the first accumulated stress data.

[0084] The stress capture module 215 can receive an output image to be displayed on the display device 100 and calculate second stress data based on the output image. The adding circuit 220 can receive second stress data corresponding to a frame of image data to be displayed on the display device 100 and add the decoded data to the second stress data to generate updated accumulated stress data. The encoder 235 can compress the updated accumulated stress data for storage in the memory 205. The previous dither value can be used in conjunction with a slice of the pixel data frame that is different from the slice of the pixel data frame corresponding to the second stress data.

[0085] It will be understood that although the terms "first," "second," "third," etc. may be used herein to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion. Thus, a first element, component, region, layer, or portion discussed herein could be referred to as a second element, component, region, layer, or portion without departing from the spirit and scope of the present inventive concept.

[0086] In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.

[0087] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present inventive concept. As used herein, the terms "substantially," "approximately," and similar terms are used as terms of approximation and not as terms of degree, and are intended to take into account the inherent deviations of measured or calculated values ​​that would be recognized by one of ordinary skill in the art.

[0088] As used herein, the singular form " one " is intended to also include the plural form, unless the context clearly indicates otherwise. It will be further understood that, when used in this specification, the terms "include" and / or "comprise" specify the presence of stated features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their groups. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. When following an element list, expressions such as "at least one of ... " modify the entire element list without modifying the individual elements in the list. Further, when describing an embodiment of the present invention, the use of "can" refers to "one or more embodiments of the present disclosure." In addition, the term "exemplary" is intended to indicate an example or illustration. As used herein, the terms "use," "being used," and "being used" may be considered to be synonymous with the terms "utilize," "being utilized," and "being utilized," respectively.

[0089] It will be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” or “adjacent” another element or layer, it can be directly on, directly connected to, directly coupled to, or adjacent to the other element or layer, or one or more intervening elements or layers may be present. In contrast, when an element or layer is referred to as being “directly on,” “directly connected to,” “directly coupled to,” or “immediately adjacent to” another element or layer, there are no intervening elements or layers present.

[0090] The electronic or electrical devices and / or any other related devices or components according to the embodiments of the present disclosure described herein can be implemented using any suitable hardware, firmware (e.g., application specific integrated circuits), software, or a combination of software, firmware, and hardware. For example, the various components of these devices can be formed on an integrated circuit (IC) chip or on separate IC chips. Further, the various components of these devices can be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB), or formed on a substrate. Further, the various components of these devices can be processes or threads running on one or more processors in one or more computing devices, executing computer program instructions and interacting with other system components to perform the various functions described herein. The computer program instructions are stored in a memory that can be implemented in a computing device using a standard memory device (such as, for example, a random access memory (RAM)). The computer program instructions can also be stored in other non-transient computer-readable media (such as, for example, a CD-ROM, a flash drive, etc.). In addition, those skilled in the art will recognize that the functions of various computing devices can be combined or integrated into a single computing device, or the functions of a particular computing device can be distributed on one or more other computing devices without departing from the spirit and scope of the exemplary embodiments of the present disclosure.

[0091] Although exemplary embodiments of systems and methods for mitigating the effects of compensation errors have been specifically described and illustrated herein, numerous modifications and variations will be apparent to those skilled in the art. Therefore, it is to be understood that systems and methods for mitigating the effects of compression errors using stress distribution compression, constructed in accordance with the principles of the present disclosure, may be embodied in other ways than as specifically described herein. The scope of the present disclosure is defined by the appended claims and their equivalents.

Claims

1. A method for compensating stress in a display device, the method comprising: compressing, by an encoder, the first accumulated stress data with quantization corresponding to the quantization value to generate compressed accumulated stress data; storing the compressed accumulated stress data in a memory; Obtaining the compressed accumulated stress data by a decoder; decoding the compressed accumulated stress data by the decoder to generate decoded data; generating a dither value based on the quantized value; adding the dither value to the decoded data to generate compensated decoded data, thereby compensating the quantization of the first accumulated stress data; receiving, by a stress capture module, an output image to be displayed on the display device and calculating second stress data based on the output image; as well as The compensated decoded data is added to the second stress data by an adding circuit to generate updated accumulated stress data.

2. The method according to claim 1, wherein Generating the dither value and adding the dither value to the decoded data are performed by the decoder or a circuit external to the decoder.

3. The method according to claim 1, wherein The quantized value is a power of two, wherein the quantized value is stored in the header of the compressed accumulated stress data, and The compressed accumulated stress data corresponds to the brightness value of a slice of a pixel data frame to be displayed on the display device.

4. The method according to claim 1, wherein Generating the jitter value is further based on a previous jitter value corresponding to the compressed accumulated stress data, The previous jitter value is stored in a header of the compressed accumulated stress data.

5. The method according to claim 4, wherein Generating the dither value includes utilizing a uniform pseudo-random number generator.

6. The method according to claim 1, wherein Generating the jitter value includes: determining, by the decoder, that the quantization value is equal to 1; and In response, the jitter value is output by the decoder as zero.

7. The method according to claim 1, wherein Generating the jitter value includes: determining, by the decoder, that the quantization value is equal to 2; and In response, the dither value is output by the decoder as a modulus of the quantized value and a previous dither value plus one.

8. The method according to claim 1, wherein Generating the jitter value includes: determining, by the decoder, that the quantization value is greater than 2; and In response, the decoder outputs the dithered value as a modulus of the first value and the quantized value, The first value is calculated as the sum of a previous jitter value and half of the quantized value minus one.

9. The method according to claim 1, further comprising: The jitter value is stored by the decoder in a header of the decoded data.

10. A method for compensating stress in a display device, the method comprising: compressing, by an encoder, the first accumulated stress data with quantization corresponding to the quantization value to generate compressed accumulated stress data; The encoder stores the compressed accumulated stress data in a memory; The decoder acquires the compressed accumulated stress data and decompresses the compressed accumulated stress data to generate decoded data; generating, by the decoder, a dither value based on the quantized value; adding, by the decoder, the dither value to the decoded data to generate compensated decoded data, thereby compensating for the quantization of the first accumulated stress data; receiving, by the adding circuit, second stress data corresponding to an image data frame to be displayed on the display device; as well as The compensated decoded data is added to the second stress data by the adding circuit to generate updated accumulated stress data.

11. The method according to claim 10, further comprising: The updated accumulated stress data is compressed by the encoder for storage in the memory.

12. The method according to claim 10, wherein: Generating the jitter value is further based on a previous jitter value corresponding to the first accumulated stress data, and The previous jitter value corresponds to a slice of a frame of pixel data, and the slice of the frame of pixel data is different from a slice of the frame of pixel data corresponding to the second stress data.

13. The method according to claim 10, wherein: The first accumulated stress data corresponds to a brightness value of a slice of a frame of pixel data to be displayed on the display device.

14. The method according to claim 10, wherein: Generating the jitter value is further based on a previous jitter value corresponding to the first accumulated stress data, and The quantized value and the previous jitter value are stored in a header of the compressed accumulated stress data.

15. The method according to claim 10, wherein Generating the jitter value includes: determining, by the decoder, the quantized value; and In response to determining that the quantized value is equal to 1, the decoder outputs the dither value as zero; or, in response to determining that the quantized value is equal to 2, the decoder outputs the dither value as a modulus of the quantized value plus one of a previous dither value.

16. The method according to claim 10, wherein Generating the jitter value includes: determining, by the decoder, that the quantization value is greater than 2; and In response, the decoder outputs the dither value as a modulus of the first value and the quantized value, and The first value is calculated as the sum of a previous jitter value and half of the quantized value minus one.

17. The method according to claim 10, further comprising: The jitter value is stored by the decoder in a header of the decoded data.

18. A system for performing stress compensation in a display device, the system comprising: Memory; as well as A processing circuit configured to perform the method according to any one of claims 1-17.

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