FIELD

Aspects of the present disclosure relate to stress compensation or image sticking or ghosting effect in a display device.

BACKGROUND

Compensation for output decline in a video display such as an organic light-emitting diode (OLED) display may be used to preserve image quality as a display ages. The data used to perform such compensation may be stored in compressed form to reduce memory requirements; however, errors in such compressed data may accumulate unevenly, resulting in loss of image quality.

Additionally, when an OLED display device displays a static image for a prolonged period of time, it may suffer from image retention. The result is that once the static image is removed or changed, a faint outline—or ghosting—of the original image may still be visible to a user, even when the image content has changed. This is often referred to as image sticking, image retention, or image ghosting. The same method as stress profile is applied for image sticking.

Thus, there is a need for an improved system and method for stress compensation.

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

SUMMARY

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

Aspects of example embodiments of the present disclosure relate to a system and a method for reducing or eliminating display output decline by mitigating the effects of pixel degradation/aging in a display device.

According to some embodiments of the present disclosure, there is provided a method of stress compensation in a display device, the method including: accumulating, by an adding circuit, a brightness value of images displayed by the display device; encoding, by an encoder, the accumulated brightness value to preserve a protected portion of the accumulated brightness value; compressing, by a compressor, the accumulated brightness value; storing, by the compressor, the compressed accumulated brightness value in a memory; retrieving and decompressing, by the decompressor, the compressed accumulated brightness value to generate a decompressed value; and decoding, by a decoder, the decompressed value based on the protected portion to generate a decoded value corresponding to the accumulated brightness value, the decoded value having lower compression noise than the decompressed value.

In some embodiments, the protected portion includes k bits of the accumulated brightness value starting from a p-th bit of the accumulated brightness value (both p and k being integers greater than 1), and p+k−1 is less than a bit length of the accumulated brightness value.

In some embodiments, the compression noise in the decompressed value is entirely contained within a first (p+k−1)-th bits of the decompressed value.

In some embodiments, the method further includes discarding, by a truncator, lesser significant bits of the decoded value preceding the protected portion.

In some embodiments, the method further includes providing the decoded value to a compensator for compensating an input image for a stress of the display device.

In some embodiments, the encoding the accumulated brightness value includes: identifying, by the encoder, the protected portion of the accumulated brightness value; and storing, by the encoder, the protected portion in the memory.

In some embodiments, the protected portion is stored in memory in an uncompressed state.

In some embodiments, the decoding the decompressed value includes:

identifying, by the decoder, a decompressed protected portion of the decompressed value; calculating, by the decoder, a difference between the protected portion and the decompressed protected portion to generate an estimated compression noise; and calculating, by the decoder, the decoded value based on the decompressed value and the estimated compression noise to mitigate compression noise in the decompressed value.

In some embodiments, the decompressed protected portion of the decompressed value corresponds in bit position to the protected portion of the accumulated brightness value.

In some embodiments, the calculating the difference includes: calculating, by the decoder, a first error (E1) and a second error (E2) as: E1=({tilde over (x)}k−xk) mod 2kand E2=(xk−{tilde over (x)}k) mod 2k, where xkrepresents the protected portion of the accumulated brightness value, {tilde over (k)}krepresents the decompressed protected portion, and mod represents a modulo operation.

In some embodiments, calculating the decoded value includes: determining, by the decoder, that the first error is less than the second error; and in response to the determination, calculating, by the decoder, the decoded value (g) as {circumflex over (X)}={tilde over (X)}−E1·2p−1, where {tilde over (E)} represents the decompressed value and p represents a first bit location of the protected portion in the accumulated brightness value.

In some embodiments, calculating the decoded value includes: determining, by the decoder, that the first error is greater than the second error; and in response to the determination, calculating, by the decoder, the decoded value ({tilde over (X)}) as {circumflex over (X)}={tilde over (X)}+Ehd2·2p−1, where {tilde over (X)} presents the decompressed value and p represents a first bit location of the protected portion in the accumulated brightness value.

In some embodiments, calculating the decoded value includes: determining, by the decoder, that the first error is equal to the second error; and determining, by the decoder, the decoded value as the decompressed value.

In some embodiments, the encoding the accumulated brightness value includes: replicating, by the encoder, the protected portion of a plurality of times to form a binary replica string, and wherein the method further includes: compressing, by the compressor, the binary replica string; storing, by the compressor, the compressed binary replica string in the memory; and retrieving and decompressing, by the decompressor, the compressed binary replica string to generate a decompressed binary replica string.

In some embodiments, the decoding the decompressed value includes: calculating, by the decoder, a decoded protected portion to estimate the protected portion by applying a maximum likelihood decoding (MLD) process to the decompressed binary replica string; calculating, by the decoder, a difference between the decoded protected portion and a decompressed protected portion of the decompressed value to generate an estimated compression noise; and calculating, by the decoder, the decoded value based on the decompressed value and the estimated compression noise to mitigate compression noise in the decompressed value.

In some embodiments, the encoding the accumulated brightness value includes: coding, by the encoder, the protected portion to generate a plurality of parity bits, wherein the compressing the accumulated brightness value includes: compressing, by the compressor, the parity bits along with the accumulated brightness value, and wherein the decompressing the compressed accumulated brightness value includes: decompressing, by the decompressor, the compressed binary parity bits together with the compressed accumulated brightness value to generate a decompressed protected portion and decompressed parity bits.

In some embodiments, the coding of the protected portion is according to a reed-solomon code applied across slices of the accumulated brightness value, and wherein the parity bits are compressed via a different compression than the accumulated brightness value.

In some embodiments, the decoding the decompressed value includes: calculating, by the decoder, a decoded protected portion to estimate the protected portion based on the decompressed protected portion and decompressed parity bits; calculating, by the decoder, a difference between the decoded protected portion and the decompressed protected portion to generate an estimated compression noise; and calculating, by the decoder, the decoded value based on the decompressed value and the estimated compression noise to mitigate compression noise in the decompressed value.

According to some embodiments of the present disclosure, there is provided a method of stress compensation in a display device, the method including: accumulating, by an adding circuit, a brightness value of the output image with displayed by the display device; encoding, by an encoder, the accumulated brightness value to preserve a protected portion of the accumulated brightness value; compressing, by a compressor, the accumulated brightness value; storing, by the compressor, the compressed accumulated brightness value in a memory; retrieving and decompressing, by the decompressor, the compressed accumulated brightness value to generate a decompressed value; decoding, by a decoder, the decompressed value based on the protected portion to generate a decoded value corresponding to the accumulated brightness value, the decoded value having lower compression noise than the decompressed value; receiving, by the adding circuit, an output image to be displayed on the display device; adding, by the adding circuit, the decoded value to a brightness value of the output image to generate an updated accumulated brightness value.

According to some embodiments of the present disclosure, there is provided a system for performing stress compensation in a display device, the system including: a memory; and a processing circuit configured to perform: accumulating a brightness value of images displayed by the display device; encoding the accumulated brightness value to preserve a protected portion of the accumulated brightness value; compressing the accumulated brightness value; storing the compressed accumulated brightness value in the memory; retrieving and decompressing the compressed accumulated brightness value to generate a decompressed value; and decoding the decompressed value based on the protected portion to generate a decoded value corresponding to the accumulated brightness value, the decoded value having lower compression noise than the decompressed value.

