Method and apparatus for adjusting a gamma voltage curve

Abstract

This invention discloses a method and apparatus for adjusting a gamma voltage curve. The gamma voltage curve adjustment apparatus includes: a driving voltage generation device for acquiring the driving voltage distribution of sub-pixels under different display brightness levels; a gamma curve correction device for mapping the input grayscale voltage to a gamma curve correction voltage under different display brightness levels; and a driving voltage lookup table connected to both the driving voltage generation device and the gamma curve correction device, for providing a corresponding driving voltage to the display unit based on the gamma curve correction voltage. By changing the correspondence between the grayscale voltage and the gamma curve correction voltage, the gamma curve of the grayscale voltage and the output driving voltage is changed, thus solving the difficulty of adjusting multiple resistors required for gamma voltage curve adjustment.

Description

Technical Field

[0001] This invention relates to the field of display technology, and in particular to a method and apparatus for adjusting gamma voltage curves. Background Technology

[0002] Compared to current mainstream LCD displays, OLED (organic light emitting diode) offers advantages such as high contrast, wide viewing angle, low power consumption, and thinner size, making it a promising next-generation flat panel display technology and one of the most anticipated technologies in the current flat panel display field.

[0003] Specifically, the human eye's response to brightness is not a linear proportional relationship; the human eye's ability to distinguish low brightness is stronger than its ability to distinguish high brightness. To ensure that the grayscale of an image can be perceived linearly by the human eye, gamma curves are needed to compensate and correct the image's grayscale, such as... Figure 1 As shown. Because the size, arrangement, and aging rate of the R / G / B sub-pixels of the display panel are different, three gamma curves are required for calibration.

[0004] In existing technologies, grayscale correction is typically achieved using only analog gamma circuits. The digital circuitry outputs the original grayscale value, while the analog circuitry performs a lookup table function, searching for and outputting the corresponding voltage based on the grayscale voltage. A drawback of this approach is that gamma adjustment is highly limited. Figure 2 As shown, for example, within a certain display brightness range, the larger voltage is Vreg, and the smaller voltage is VGMS. This gamma circuit consists of multiple voltage-dividing resistors connected in series across these voltage nodes. The more resistors, the higher the voltage division accuracy. In this example, the resistor series consists of 2048 resistors. Changing the gamma curve requires adjustment. Figure 2 Each resistor is difficult to implement on the module. Summary of the Invention

[0005] In view of the above problems, the purpose of this invention is to provide a method and device for adjusting the gamma voltage curve, so as to meet the flexible adjustment of the gamma curve in practical applications.

[0006] According to one aspect of the present invention, a device for adjusting a gamma voltage curve is provided, comprising:

[0007] A driving voltage generation device is used to obtain the driving voltage distribution of sub-pixels under different display brightness.

[0008] The gamma curve correction device is used to map the input grayscale voltage to the gamma curve correction voltage under different display brightness.

[0009] A drive voltage lookup table is connected to both the drive voltage generating device and the gamma curve correction device, and is used to provide a corresponding drive voltage to the display unit based on the gamma curve correction voltage.

[0010] Preferably, the reference point for the grayscale voltage is set via a user register.

[0011] Preferably, the display brightness includes multiple intervals, and the gamma curve correction voltage within the multiple intervals is calculated by interpolation of the binding point values ​​of the endpoint gamma correction voltage of each interval.

[0012] Preferably, the driving voltage distribution is obtained according to a fixed ratio of the maximum and minimum values ​​of the display brightness.

[0013] Preferably, the gamma voltage curve adjustment device further includes a digital-to-analog converter for converting the gamma curve correction voltage in digital signal form into an analog signal.

[0014] Preferably, the gamma curve correction device includes:

[0015] Storage module, used to store the binding point data of the endpoint gamma correction voltage;

[0016] The parallel-to-serial conversion module includes a multi-selector and a first-in-first-out queue. The multi-selector is used to store the parallel data from the two endpoints of the storage module into the first-in-first-out queue one by one, and the first-in-first-out queue is used to read out the stored data one by one.

[0017] The interpolation calculation module is used to perform interpolation calculations on the data read from the first-in-first-out queue;

[0018] The serial-to-parallel converter sends the calculation results of the interpolation calculation module to different ports according to the selection signal.

[0019] Preferably, the storage module includes a first storage unit and a second storage unit, wherein the first storage unit and the second storage unit respectively store the binding point data of the gamma correction voltage of two adjacent endpoints.

[0020] Preferably, the gamma curve correction device further includes a clock gating module, used to turn each module in the gamma curve correction device on or off according to the state of the image control signal.

[0021] Preferably, the chip select signal of the storage module remains valid during the data reading process, and the read address signal of the storage module changes continuously until the reading is completed.

[0022] According to another aspect of the present invention, a method for adjusting a gamma voltage curve is provided, comprising:

[0023] Obtain the driving voltage distribution of sub-pixels under different display brightness levels;

[0024] Under different display brightness levels, the input grayscale voltage is mapped to the gamma curve correction voltage;

[0025] The corresponding driving voltage is provided to the display unit based on the gamma curve correction voltage.

[0026] In terms of power consumption, the gamma voltage curve adjustment device provided by this invention has the following advantages: when the display brightness changes, in the current frame (assuming there are 2400 horizontal synchronization signal cycles), the gamma curve correction device only has clock operation in the horizontal synchronization signal cycle, and the power consumption is close to 0. In terms of area, compared with the traditional 75-group parallel calculation method, this application reduces the area by 98.67% through serial-to-parallel conversion. In terms of visual effect, this design can meet the gamma curve requirements in practical applications. During the module debugging stage, the gamma adjustment is flexible and can be set freely by the screen manufacturer. Attached Figure Description

[0027] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0028] Figure 1 The graph showing the correspondence between grayscale voltage and display brightness in OLED is shown.

[0029] Figure 2 A schematic diagram of a gamma circuit in the background art is shown.

[0030] Figure 3 A block diagram of the device for adjusting the gamma voltage curve in a display panel provided by the present invention is shown.

[0031] Figure 4 A schematic diagram of piecewise linear fitting of grayscale voltage-gamma curve correction voltage provided by the present invention is shown.

[0032] Figure 5 This invention illustrates a schematic diagram of grayscale voltage-gamma curve correction voltage fitting under different backlight brightness levels.

[0033] Figure 6 An internal block diagram of the driving voltage generating device provided by the present invention is shown.

[0034] Figure 7 A schematic diagram of the gamma voltage interpolation process provided by the present invention is shown.

[0035] Figure 8 A schematic diagram of the storage module provided by the present invention is shown.

[0036] Figure 9A flowchart of the method for adjusting the gamma voltage curve in a display panel provided by the present invention is shown. Detailed Implementation

[0037] Various embodiments of the invention will now be described in more detail with reference to the accompanying drawings. In the various drawings, the same elements or modules are indicated by the same or similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale.

[0038] It should be understood that, in the following description, "circuit" may include single or combined hardware circuits, programmable circuits, state machine circuits, and / or elements capable of storing instructions executed by the programmable circuit. When an element or circuit is said to be "connected" to another element or "connected" between two nodes, it may be directly coupled or connected to the other element, or there may be intermediate elements; the connection between elements may be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected" to another element, it means that there are no intermediate elements between them.

[0039] Furthermore, certain terms are used in this patent specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This patent specification and claims do not distinguish components based on differences in name, but rather on differences in function.

[0040] Furthermore, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0041] To address the technical deficiencies mentioned in the prior art, a new device for adjusting the gamma voltage curve is proposed.

[0042] Figure 3 A block diagram of the device for adjusting the gamma voltage curve in a display panel provided by the present invention is shown.

[0043] like Figure 3As shown, the gamma voltage curve adjustment device includes a gamma curve correction device 10, a digital-to-analog converter 20, a drive voltage lookup table 30, and a drive voltage generation device 40. The gamma voltage curve adjustment device is divided into a digital part and an analog part. The digital part consists of the digital-to-analog converter 20 and the gamma curve correction device 10, while the analog part consists of the drive voltage generation device 40 and the drive voltage lookup table 30.

[0044] Figure 4 A schematic diagram of piecewise linear fitting of grayscale voltage-gamma curve correction voltage provided by the present invention is shown.

[0045] like Figure 4 As shown, in the digital section, the gamma curve correction device 10 maps the input grayscale voltage to the gamma curve-corrected value (i.e., the gamma curve correction voltage shown in the attached figure) based on the driving voltage Vdata of the three sub-pixels (R / G / B) under different display brightness levels. The digital signal of the gamma curve correction voltage is then converted into an analog signal by the digital-to-analog converter 20. In other words, a non-linear mapping is performed on the grayscale voltage. The input is the grayscale voltage corresponding to... Figure 4 The x-coordinate in the coordinate system can be set by the user register, and the y-coordinate in the graph is a gamma curve correction voltage in the form of an analog signal.

[0046] Figure 5 The diagram shows a schematic of the grayscale voltage-gamma curve correction voltage fitting under different backlight brightness provided by the present invention.

[0047] like Figure 5 As shown, in OLEDs, display brightness control is represented by Display Brightness Value (DBV), corresponding to backlight brightness in LCDs. It is typically represented by 13 bits of data, with a total of 8191 levels. DBV can be divided into multiple bands, with the two ends of each band being th_bands. When DBV reaches a certain th_band, the gamma curve corresponding to that th_band and the next th_band is invoked. To achieve good grayscale transitions at low display brightness, OLEDs use multiple gamma curves to control the entire display brightness area (the attached diagram only shows two gamma curves, one high and one low, as an example). The gamma curve correction voltages corresponding to adjacent endpoints of the th_band are linearly interpolated, meaning each display brightness value forms a gamma curve. For example, setting th_band = 100 and brightness to 5 nits means that when DBV = 100, the brightness corresponding to the highest grayscale level (1023 for 10 bits) is 5 nits.

[0048] In the analog section, the driving voltage generating device 40 obtains the maximum and minimum values ​​of the display brightness range according to different display brightness, and the remaining intermediate values ​​are fixed according to the ratio to obtain the driving voltage Vdata distribution of the three sub-pixels R / G / B.

[0049] Finally, in the analog section, the drive voltage lookup table 30 is used. By looking up the drive voltage Vdata corresponding to the gamma curve correction voltage in this lookup table, the display unit OLED can display the corresponding brightness according to the drive voltage Vdata. In this scheme, by adjusting the piecewise linear fitting of the grayscale voltage and gamma curve correction voltage in the digital section, the correspondence between the grayscale voltage and the gamma curve correction voltage in the digital section is changed, thereby changing the gamma curve of the grayscale voltage and the output drive voltage Vdata. This solves the difficulty of adjusting multiple resistors to adjust the gamma voltage curve.

[0050] Figure 6 An internal block diagram of the driving voltage generating device provided by the present invention is shown.

[0051] like Figure 6 As shown, the gamma curve correction device 10 includes a storage module 101, a parallel-to-serial conversion module 102, an interpolation calculation module 103, and a serial-to-parallel conversion module 104.

[0052] All configuration data for the gamma correction voltage binding point values ​​are stored in the storage module 101. To quickly obtain the required 75 binding point values ​​during the Vertical Back Porch, the DBV value range (0-8191) can be divided into 10 endpoints (th_band, corresponding to 9 intervals) to accommodate different user-set display brightness levels. Each endpoint (th_band) corresponds to a set of gamma binding point configurations (R / G / B gamma curves, 75 binding point values). When the DBV is within a certain interval, two endpoints (th_band) of that interval are selected, and then linear interpolation is performed.

[0053] exist Figure 6In this process, the gamma correction voltage binding point value data for each display brightness needs to be interpolated using the data from the two endpoints th_band. This application provides a parallel-to-serial and then serial-to-parallel calculation architecture. The storage module 101 outputs the binding point configuration data of the two endpoints th_band to the parallel-to-serial module 102. The binding point configuration data is, for example, divided into two groups, corresponding to band_low and band_high in the attached figure. Each group of data contains the binding point configuration data of three gamma curves, namely index_y_0_R-index_y_24_R, index_y_0_B-index_y_24_B, and index_y_0_G-index_y_24_G, which are read in parallel data form.

[0054] The parallel-to-serial conversion module 102 specifically includes a multiplexer and a First-In-First-Out (FIFO) queue. The multiplexer stores parallel data one by one into the FIFO queue, and then the data is read out one by one from the FIFO queue for interpolation calculation by the interpolation module 103. The serial-to-parallel conversion module 104 specifically includes a one-to-many selector, which, based on the selection signal, sends the calculation results of the interpolation module 103 to different ports to achieve data distribution.

[0055] The above scheme allows 75 sets of computational data to pass through the interpolation module sequentially, effectively utilizing hardware resources to ensure computational efficiency while saving hardware resources.

[0056] Figure 7 A schematic diagram of the gamma voltage interpolation process provided by the present invention is shown.

[0057] like Figure 7 As shown, when the background brightness is between endpoint th_band_5 and endpoint th_band_6, all configuration data for the binding point values ​​of the two endpoints are interpolated one-to-one. For example, in... Figure 7 The 25th binding point value index_y_24 in the middle endpoint th_band_6 is interpolated with the 25th binding point value index_y_24 in the endpoint th_band_5. The specific process will not be described here.

[0058] Figure 8 A schematic diagram of the storage module provided by the present invention is shown.

[0059] like Figure 8As shown, in one embodiment, all configuration data for the gamma correction voltage binding point value is stored in the storage module 101. If a traditional storage read control is used, the data is read once, then calculated, and then the next data is read. This storage read control not only increases the complexity of the control logic but also consumes a significant amount of unnecessary time, hindering the rapid calculation of the gamma binding point value. However, the storage module in this application uses continuous read control logic. Once storage read begins, the chip select signal remains active, and the read address signal changes continuously until the required gamma binding point configuration data is read.

[0060] Each DBV's gamma-corrected voltage binding point value requires interpolation calculation using two endpoints (th_band). Therefore, the configuration data for both endpoints (th_band) also needs to be read from the storage module. The storage module in this application includes a first storage unit 1011 and a second storage unit 1012, which respectively store the gamma configuration data for adjacent endpoints (th_band). When the gamma configuration data for both endpoints (th_band) needs to be read, it can be read from the first storage unit 1011 and the second storage unit 1012 simultaneously, reducing the total storage and retrieval time by 50% compared to traditional methods.

[0061] In one embodiment of this application, clock gating can be added to each module of the gamma curve correction device. The clock gating is controlled by an image control signal, which has two states: Active and Blank. In the Active state, the modules do not operate, so the clock is turned off. All calculations of the gamma curve correction device can be completed in approximately 300 clock cycles. Therefore, starting from the start of operation, a count is made, and when 300 clock cycles are reached, the clock is turned off. Until the next activation, the module only operates when the display brightness changes or the mode is switched, so the clock is turned off during other time periods. Adding clock gating control logic to the above scheme can effectively reduce power consumption.

[0062] Figure 9 A flowchart of the method for adjusting the gamma voltage curve in a display panel provided by the present invention is shown.

[0063] like Figure 9 As shown, the method for adjusting the gamma voltage curve is implemented, for example, by the aforementioned gamma voltage curve adjustment device. This method specifically includes the following steps:

[0064] S1: Obtain the driving voltage distribution of sub-pixels under different display brightness.

[0065] In step S1, the driving voltage generating device obtains the maximum and minimum values ​​of the display brightness range according to different display brightness, and the remaining intermediate values ​​are fixed according to the ratio, thus obtaining the driving voltage Vdata distribution of the three sub-pixels R / G / B.

[0066] S2: Map the input grayscale voltage to gamma curve correction voltage under different display brightness.

[0067] In step S2, the gamma curve correction device 10 maps the input grayscale voltage to the gamma curve-corrected value based on the driving voltage Vdata of the three sub-pixels (R / G / B) under different display brightness levels; that is, it performs a non-linear mapping on the grayscale voltage. The input is the grayscale voltage corresponding to... Figure 4 The x-coordinate in the coordinate system can be set by the user register, and the y-coordinate in the graph is a gamma curve correction voltage in the form of an analog signal.

[0068] S3: Provide a corresponding driving voltage to the display unit based on the gamma curve correction voltage.

[0069] In step S3, by finding the driving voltage Vdata corresponding to the gamma curve correction voltage, the display unit OLED can display the corresponding brightness according to the driving voltage Vdata. In this scheme, by adjusting the piecewise linear fitting of the gray level voltage and gamma curve correction voltage in the digital part, the correspondence between the gray level voltage and the gamma curve correction voltage in the digital part is changed, thereby changing the gamma curve of the gray level voltage and the output driving voltage Vdata. This solves the difficulty of adjusting multiple resistors for adjusting the gamma voltage curve.

[0070] In terms of power consumption, when the display brightness changes, the gamma curve correction device only operates during the horizontal synchronization signal cycle of the current frame (assuming 2400 horizontal synchronization signal cycles), resulting in near-zero power consumption. In terms of area, compared to the traditional 75-group parallel calculation method, this application reduces the area by 98.67% through serial-to-parallel conversion. In terms of visual effect, this design can meet the gamma curve requirements in practical applications. During the module debugging stage, the gamma adjustment is flexible and can be freely set by the screen manufacturer.

[0071] It should be noted that in this application, the backlight brightness is stored using 13 bits, and the background brightness is divided into 9 intervals. Each gamma curve uses 25 binding point values. These data can be modified according to the actual situation, and this application does not impose any restrictions on them.

[0072] It should be noted that those skilled in the art will understand that the terms “during,” “when,” and “when…” used herein in relation to circuit operation are not strict terms indicating an action that occurs immediately upon the commencement of a startup action, but rather that there may be some small but reasonable delays, such as various propagation delays, between the startup action and the reaction action initiated by it. The terms “approximately” or “substantially” used herein mean that an element value is expected to be close to the declared value or position. However, as is well known in the art, there are always small deviations that make it difficult for the value or position to be strictly the declared value. It has been properly determined in the art that a deviation of at least ten percent (10%) (or at least twenty percent (20%) for semiconductor doping concentration) is a reasonable deviation from the described accurate ideal target. When used in conjunction with signal states, the actual voltage value or logic state of the signal (e.g., “1” or “0”) depends on whether positive or negative logic is used.

[0073] As described above, these embodiments of the present invention do not exhaustively describe all details, nor do they limit the invention to specific embodiments. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to effectively utilize the invention and its modifications. The scope of protection of this invention should be determined by the scope defined in the claims and their equivalents.

Claims

1. A device for adjusting a gamma voltage curve, comprising digital circuitry and analog circuitry. The digital circuit includes: The gamma curve correction device is used to obtain the gamma curve correction voltage by nonlinearly mapping the input grayscale voltage under different display brightness. as well as A digital-to-analog converter is used to convert the gamma curve correction voltage in digital signal form into an analog signal. The analog circuit includes: A driving voltage generation device is used to acquire the driving voltage distribution of sub-pixels under different display brightness levels; and A drive voltage lookup table, connected to both the drive voltage generation device and the gamma curve correction device, is used to provide a corresponding drive voltage to the display unit based on the gamma curve correction voltage in analog signal form. The gamma curve correction device includes: The storage module is used to store the binding point data of the endpoint gamma correction voltage; The parallel-to-serial conversion module includes a multi-selector and a first-in-first-out queue. The multi-selector is used to store the parallel data from the two endpoints of the storage module into the first-in-first-out queue one by one, and the first-in-first-out queue is used to read out the stored data one by one. The interpolation calculation module is used to perform interpolation calculations on the data read from the first-in-first-out queue. Calculate; The serial-to-parallel converter sends the calculation results of the interpolation calculation module to different ports according to the selection signal.

2. In the gamma voltage curve adjustment device according to claim 1, the reference point of the grayscale voltage is set by a user register.

3. The gamma voltage curve adjustment device according to claim 1, wherein the display brightness includes multiple intervals, and the gamma curve correction voltage in the multiple intervals is calculated by interpolation of the binding point value of the gamma correction voltage at the endpoints of each interval.

4. The gamma voltage curve adjustment device according to claim 1, wherein the driving voltage distribution is obtained according to a fixed ratio of the maximum and minimum values ​​of the display brightness.

5. The gamma voltage curve adjustment device according to claim 1, wherein the storage module includes a first storage unit and a second storage unit, wherein the first storage unit and the second storage unit respectively store the binding point data of the gamma correction voltage of two adjacent endpoints.

6. The gamma voltage curve adjustment device according to claim 1, wherein the gamma curve correction device further includes a clock gating module for turning on or off each module in the gamma curve correction device according to the state of the image control signal.

7. In the gamma voltage curve adjustment device according to claim 6, the chip select signal of the storage module remains valid during the data reading process, and the read address signal of the storage module changes continuously until the reading is completed.

8. A method for adjusting a gamma voltage curve, comprising: Obtain the driving voltage distribution of sub-pixels under different display brightness levels; Under different display brightness levels, the input grayscale voltage is nonlinearly mapped to obtain the gamma curve correction voltage; The gamma curve correction voltage in digital signal form is converted into an analog signal; as well as A table is consulted based on the gamma curve correction voltage in analog signal form to provide the corresponding drive voltage to the display unit. The step of mapping the input grayscale voltage to gamma curve correction voltage under different display brightness conditions includes: Store the binding point data of the terminal gamma-corrected voltage; The parallel data at both ends of the storage is stored one by one into a first-in-first-out queue, so that the stored data can be read out one by one. The data read from the first-in-first-out queue is interpolated; and Based on the selection signal, the interpolation calculation results are sent to different ports respectively.

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