Display device and control method for display device

Abstract

A display device (100) comprises: a display unit (10) having a plurality of sub-pixels (Pi) each including a light-emitting element; and a control unit (20) for controlling the display unit, the control unit shifting the display position of an image frame in the display unit with the passage of time. The control unit sets the display position according to gradation data of the image frame and stress data corresponding to a sub-pixel group in a predetermined region of the display unit.

Description

Display device and display device control method

[0001] The present disclosure relates to a display device and a method for controlling the display device.

[0002] In a display device, for example, an organic electroluminescent (hereinafter referred to as "organic EL") display device, when an image is displayed for a long period of time, a trace of the image may remain on the screen even after the display of the image is stopped (burn-in). There is a demand for a technology to make this burn-in less noticeable, that is, a burn-in compensation (brightness degradation compensation) technology.

[0003] Japanese Patent Application Laid-Open No. 2006-124499 discloses a technology that reduces the visibility of image burn-in by shifting the display position of the entire image on the panel by a predetermined distance at predetermined time intervals. When the same image is displayed for a long period of time, the burn-in at the image boundaries can be blurred and made less noticeable.

[0004] Japanese Patent Publication No. 2007-304318

[0005] However, this technique has difficulty in reducing image burn-in itself, meaning that even if this technique is applied, there is no significant change in the degree of burn-in except near the boundary of the burn-in.

[0006] An object of the present disclosure is to provide a display device and a method for controlling the display device that effectively suppress image burn-in on the display device.

[0007] The display device comprises a display unit having a plurality of sub-pixels each including a light-emitting element, and a control unit that controls the display unit, wherein the control unit shifts the display position of a frame image within the display unit over time, and the control unit sets the display position according to the gradation data of the frame image and stress data corresponding to a group of sub-pixels within a specified area of ​​the display unit.

[0008] The present disclosure can provide a display device and a method for controlling the display device that effectively suppress image burn-in on the display device.

[0009] 1 is a schematic diagram illustrating an example of a display device; FIG. 2 is a flow diagram illustrating an example of a control method for a display device; FIG. 3 is a schematic diagram illustrating an example of frame image shifting processing; FIG. 4 is a diagram illustrating an example of frame images being shifted; FIG. 5 is a diagram illustrating an example of a change in stress level due to frame image shifting processing; FIG. 6 is a diagram illustrating an example of a frame image being shifted; FIG. 7 is a diagram illustrating an example of a frame image being shifted; FIG. 8 is a diagram illustrating an example of a change in stress level due to frame image shifting processing; FIG. 9 is a flow diagram illustrating an example of a control method for a display device; FIG. 10 is a schematic diagram illustrating an example of frame image shifting processing; FIG. 11 is a diagram illustrating an example of frame image being shifted; FIG. 12 is a flow diagram illustrating an example of a control method for a display device; FIG. 13 is a diagram illustrating an example of a change in stress level due to frame image shifting processing.

[0010] [Embodiment 1] Hereinafter, a display device 100 according to embodiment 1 will be described in detail. Fig. 1 is a schematic diagram showing the display device 100 of embodiment 1. The display device 100 includes a display unit 10 and a control unit 20.

[0011] The display unit 10 is, for example, an EL display device, and has a display region R0 that displays images, characters, and other videos. The display region R0 has pixel regions P0 arranged vertically and horizontally. In the pixel region P0, sub-pixels P1 to P3 (hereinafter, "P1 to P3" may be collectively referred to as Pi), each of which includes a light-emitting element, are arranged. That is, the display unit 10 has a plurality of sub-pixels Pi, each of which includes a light-emitting element. Here, the pixel region P has three sub-pixels P1 to P3, but the pixel region P0 may have one, two, four or more sub-pixels Pi.

[0012] The emission colors (emission colors of the light-emitting elements) of the sub-pixels P1 to P3 can be different. For example, if the emission colors of the sub-pixels P1 to P3 are red (R), green (G), and blue (B), respectively, the sub-pixels P1 to P3 will be red sub-pixels, green sub-pixels, and blue sub-pixels, respectively. If the emission colors of the sub-pixels P1 and P2 are white and yellow, respectively, the sub-pixels P1 and P2 will be white sub-pixels and yellow sub-pixels, respectively.

[0013] The luminance characteristics of the subpixels Pi tend to deteriorate over time. That is, the luminance at the same gradation value decreases as time passes. The decrease in luminance is considered to be caused by the sum of stresses (hereinafter referred to as "stress amount", e.g., the integrated value of current) applied to the subpixels Pi. In particular, if the stress amount STi of a certain subpixel Pi is greater than the stress amounts STj of its surrounding subpixels Pj, the subpixel Pi will appear darker than the surrounding subpixels Pj, which will be perceived by the user as burn-in.

[0014] The control unit 20 processes the video signal S0 to generate a shifted video signal S1, thereby controlling the display unit 10 and shifting the display position of the frame video within the display unit 10 over time. This reduces non-uniformity in the characteristics of the sub-pixels Pi. The shifted video signal S1 is a video signal in which the frame video in the video signal S0 is shifted from its original display position (hereinafter also referred to as the "normal display position") on the display unit 10, and the control unit 20 changes the amount of shift M of the position in the shifted video signal S1 (hereinafter also referred to as the "shift amount") over time. This will be described in detail later.

[0015] The control unit 20 includes a gradation current conversion unit 21 , a temperature coefficient calculation unit 22 , a time sampling unit 23 , a stress data storage unit 24 , a position shift calculation unit 25 , a gradation correction calculation unit 26 , and a signal processing unit 27 .

[0016] The gradation current converter 21 converts the gradation signal of each pixel of the frame image in the shifted video signal S1 into a digital gradation value BL. The integrated amount of this gradation value is a basic element of stress data (a kind of stress amount) and is a factor in the deterioration of the characteristics of the sub-pixels.

[0017] The temperature coefficient calculation unit 22 derives the temperature coefficient Ktmp based on the temperature of the display unit 10 measured by the temperature sensor TS. This is because temperature has a significant effect on the degradation of the characteristics of the subpixel Pi. That is, even when the same current is supplied to the subpixel Pi, the higher the temperature, the faster the degradation of the characteristics will progress.

[0018] The temperature coefficient calculation unit 22 multiplies the derived temperature coefficient Ktmp by the gradation value BL output from the gradation current conversion unit 21 for each sub-pixel Pi to calculate a stress basic amount Sb (=BL*Ktmp).

[0019] The time sampling unit 23 samples the basic stress amount Sb calculated by the temperature coefficient calculation unit 22 and stores and integrates it in the stress data storage unit 24 .

[0020] By integrating the basic stress amount Sb for each subpixel Pi, stress data for each subpixel Pi can be calculated. The stress data is the total amount of load on the subpixel Pi and corresponds to the deterioration of the characteristics (current-luminance curve) of the subpixel Pi. Hereinafter, the stress data calculated in this manner may be referred to as a stress amount ST. Note that the stress data may be calculated based on factors that define the luminance of the subpixel Pi other than the gradation value BL, such as the luminance value or the current value.

[0021] The time sampling unit 23 samples the stress data every update period Tr (for example, one to several seconds) and updates the stress data in the stress data storage unit 24. By sampling the stress data over time, the efficiency of processing in the control unit 20 can be improved. The stress data update period Tr is preferably longer than the frame period T0 (the update interval between frame images). This is because the state of the image does not change within the frame period T0. It is also possible to calculate stress data for all frame images without sampling.

[0022] The stress data storage unit 24 is, for example, a memory, and stores stress data for the sub-pixels Pi. The stress data is accumulated for each unit area including one or more sub-pixels Pi. The stress data corresponds to the gradation data of the frame image and to a group of sub-pixels within a predetermined area R1 of the display unit 10.

[0023] The predetermined region R1 is a region excluding the edge portions of the display region R0. As shown in FIG. 1 , the predetermined region R1 may be a region excluding the vicinity of the periphery of the display region R0 (for example, near the frame or edge portion). The edge portions or vicinity of the periphery of the display unit 10 are less noticeable even if the luminance of the sub-pixels Pi is low, so they can be excluded from the predetermined region R1. Note that the predetermined region R1 may be the entire display region R0 of the display unit 10.

[0024] The position shift calculation unit 25 determines the amount of shift M of the display position based on the stress data, as will be described in detail later.

[0025] The gradation correction calculation unit 26 corrects the gradation of the frame image based on the stress data and the shift amount M of the display position. The gradation of each sub-pixel Pi is corrected based on the stress data in response to deterioration of the characteristics. By correcting the gradation, the current supplied to the sub-pixel Pi is increased, preventing a decrease in the luminance of the sub-pixel Pi. At this time, the correspondence between the gradation value and the sub-pixel, which has changed due to the shift of the display position, is aligned based on the shift amount M.

[0026] In this way, the control unit 20 shifts the display position of the frame image and corrects the gradation corresponding to the luminance degradation. However, the control unit 20 may only shift the display position of the frame image without correcting the gradation corresponding to the luminance degradation.

[0027] The signal processing unit 27 processes the video signal S0 based on the shift amount M and the tone correction amount to shift the frame video and perform tone correction, thereby generating a shifted video signal S1.

[0028] (Control method of display device 100) The control method of display device 100, particularly the shifting process of frame images, will be described below. The shifting process of frame images is basically performed by position shift calculation unit 25. However, the process will be described here as being performed by control unit 20.

[0029] Fig. 2 is a flow diagram showing an example of a control method for the display device 100. Fig. 3 is a schematic diagram showing an example of frame image shifting processing. Fig. 4 is a diagram showing an example of frame images to be shifted. Fig. 5 is a diagram showing an example of a change in stress amount due to frame image shifting processing.

[0030] The control unit 20 sets the display position of the frame image in accordance with the gradation data and stress data of the frame image. The stress data corresponds to a group of sub-pixels in a predetermined region R1 of the display unit 10. In other words, the control unit 20 sets the display position of the frame image in accordance with the gradation data of the frame image and the stress data corresponding to a group of sub-pixels in a predetermined region R1 of the display unit 10. This makes the characteristics of the sub-pixels Pi uniform, reducing image burn-in.

[0031] As shown in Fig. 2, the shifting process of the frame images is performed by determining whether or not a period T has elapsed (step S15) and dividing the period T. Here, the period before it is determined that the period T has elapsed is referred to as a first period T1, and the period after it is determined that the period has elapsed is referred to as a second period T2. Thereafter, the period T sequentially transitions to a third period T3, a fourth period T4, and so on. This period T is a period in which the shift amount M of the frame images is constant, and is set so that the shift of the frame images is difficult to visually recognize. Note that the shift amount M may be set for each frame image.

[0032] This period T may be longer than the frame period T0 (the update interval of the frame image), for example, one minute or more. That is, the first period T1 and the second period T2 may each be one minute or more. The period T may be longer than the update period Tr of the stress data. The update period Tr of the stress data may be longer than the frame period T0 but shorter than the first period T1.

[0033] (1) Selection of Most Degraded Subpixel Pw (Step S11) During the first period T1, the control unit 20 selects the most degraded subpixel Pw from the subpixel group in the predetermined region R1 of the display unit 10 based on the stress data (Step S11).

[0034] The most degraded subpixel Pw is the subpixel Pi with the largest amount of stress within the predetermined region R1 (see FIG. 1 ). There may be multiple most degraded subpixels Pw within the predetermined region R1. In this case, from among these multiple most degraded subpixels Pw, the subpixel Pi closest to the position where scanning of the frame image starts, for example, the upper left position, can be selected as the most degraded subpixel Pw.

[0035] (2) Determining the Shift Amount M (Display Position) (Step S12) The control unit 20 sets the first display position so that the minimum gradation is assigned to the most deteriorated subpixel Pw during the first period T1. This will be described in detail below.

[0036] The control unit 20 determines the shift amount M of the frame image, i.e., the position at which the frame image is displayed on the display unit 10. As shown in Fig. 3, the frame image is shifted from the normal display position Fs to a display position Fe (first display position). This shift amount M(ix, iy) can be expressed as a vector quantity having the shift direction and the absolute value of the shift amount M relative to a reference point O(0,0). ix and iy represent the shift amount M in the X-axis and Y-axis directions in units of sub-pixel Pi.

[0037] Here, three areas A0, A1, and A2 can be defined depending on the degree of overlap between display position Fs and display position Fe. Area A0 is an area where display position Fs and display position Fe overlap, and a shifted frame video is displayed. Area A1 is located outside the normal display position Fs (i.e., display area R0), and is an area that is not displayed on the display unit 10. Area A2 is located outside the display position Fe, and is an area where there is no video data (frame video) of the video signal S0. For area A0, for example, it is possible to set the gradation of the sub-pixel Pi to the lowest gradation (black).

[0038] The control unit 20 selects a minimum gradation region with the minimum display gradation from the frame image, and determines the shift amount M of the frame image so that this minimum gradation region is assigned to the most deteriorated subpixel Pw. For example, the control unit 20 controls the light-emitting element of the most deteriorated subpixel to be turned off (lowest gradation (dark display), or a state in which the light-emitting element is not emitting light). That is, the light-emitting element of the most deteriorated subpixel may be turned off during at least one of the first period T1 and the second period T2.

[0039] The first display position may be the display position at which the most deteriorated sub-pixel Pw has the minimum display grayscale level in the first frame image of the plurality of frame images.

[0040] As shown in FIG. 3, by shifting the display position from the normal display position Fs to the display position Fe, the minimum gradation BL1 can be assigned to the most deteriorated subpixel Pw.

[0041] In this case, the shift amount M can be limited within a predetermined range AM. That is, as shown in FIG. 3 , the shift amount (shift amount M) of the first display position Fe and the second display position relative to the normal display position Fs may be within a predetermined range AM (Lx, Ly). The predetermined range AM (Lx, Ly) can be defined as twice the maximum allowable shift amounts ixmax and iymax in the X-axis and Y-axis directions relative to the reference point O (0, 0) (Lx = 2 * ixmax, Ly = 2 * iymax). By limiting the shift amount M, the shift in the frame image can be made less noticeable, reducing the likelihood of an unnatural image. This predetermined range AM is, for example, a shift amount of 1% in the horizontal scanning direction (x direction) and 1% in the vertical scanning direction (y direction) relative to the normal display position Fs. This predetermined range AM is not limited to a square or rectangle, but may also be a circle or ellipse.

[0042] In this case, the control unit 20 selects, during the first period T1, a first display position at which the display gradation of the most deteriorated subpixel Pw obtained from the stress data is minimum, from among display positions whose deviation from the normal display position is within a predetermined range AM. That is, during the first period T1, the control unit 20 selects the minimum gradation from the gradation data of the frame video within the predetermined range AM based on the most deteriorated subpixel Pw. That is, the control unit 20 searches for the minimum gradation BL1(Fs) within a search range AS (i.e., the predetermined range AM(Lx, Ly)) centered at C, which is the most deteriorated subpixel Pw, and shifts the display position of the frame video by a shift amount M so that the minimum gradation BL1(Fs) is assigned to the most deteriorated subpixel Pw.

[0043] Here, it is possible that multiple minimum gradations BL1(Fs) are arranged within the search range AS. For example, in FIG. 3, three minimum gradations BL1(Fs), BL2(Fs), and BL3(Fs) may be arranged within the search range AS. In such a case, for example, it is possible to select the minimum gradation BL1(Fs) that results in the smallest shift amount M.

[0044] (3) Shifting the Frame Image (Step S13) The frame image is shifted based on the determined shift amount M (Step S13).

[0045] 4 includes a stress distribution ST1, a pre-shift frame image Fs1, and a post-shift frame image Fe1. The stress distribution ST1 represents the amount of stress for each subpixel Pi. The magnitude of the stress amount is represented by shading, with the subpixel Pw enclosed in a bold frame (the most deteriorated subpixel Pw) having the largest amount of stress. The pre-shift frame image Fs1 and the post-shift frame image Fe1 represent the frame images before and after the shift, respectively.

[0046] Here, a frame image with a black and white 4x4 checkerboard pattern is used as the frame image. Because a white display has a large amount of stress and a black display has a small amount of stress, if the frame image Fs1 is displayed as is, the amount of stress of the most deteriorated subpixel Pw will increase, and the difference in stress between the most deteriorated subpixel Pw and the other subpixels Pi will also increase. Therefore, the frame image is shifted to reduce the increase in the amount of stress to the most deteriorated subpixel Pw. In other words, the gradation assigned to the most deteriorated subpixel Pw is changed from the highest gradation (bright state) to the lowest gradation (dark state), thereby reducing the amount of stress applied to the most deteriorated subpixel Pw.

[0047] At this time, in addition to shifting the frame image, gradation correction may be performed. In this case, the current value of the light-emitting element included in the most deteriorated subpixel Pw is set to a value corresponding to the gradation data and stress data. As a result, the current value supplied to the light-emitting element of the most deteriorated subpixel Pw is adjusted to correspond to the deterioration state of the most deteriorated subpixel Pw, thereby ensuring luminance that more closely corresponds to the gradation data. Gradation correction may be performed not only for the most deteriorated subpixel Pw but also for all subpixels, and the current value of the light-emitting element may be set to a value corresponding to the gradation data and stress data. This ensures appropriate luminance throughout the display unit 10.

[0048] (4) When the frame image is updated, a shift process is executed on the updated frame image (steps S14 and S15). At this time, the shifting continues by the determined shift amount M until the period T has elapsed. As mentioned above, if the shift amount M is determined for each frame image, the frame image will shift frequently, which can easily cause an unnatural feeling.

[0049] If the frame video is a still image, the same frame video will be displayed at the first display position during the first period T1. On the other hand, if the frame video is a moving image, multiple different frame videos will be displayed at the first display position during the first period T1.

[0050] (5) Passage of Period (Step S15) When the period has passed (Step S15), the period transitions from the first period T1 to the second period T2, and the most deteriorated subpixel is selected, the shift amount M (display position) is determined, the frame image is updated, the frame image is shifted, and so on.

[0051] Since the stress data is updated, the most degraded subpixel may change between the first period T1 and the second period T2. On the other hand, the most degraded subpixel may not change between the first period T1 and the second period T2. This is because it may take some time for the stress amounts of the other subpixels to become greater than the stress amount of the most degraded subpixel.

[0052] In such a case, for example, if the video is a still image, the display grayscale of the most deteriorated subpixel Pw may be the same throughout the first period T1 and the second period T2, whereas if the video is a moving image, the display grayscale of the most deteriorated subpixel Pw may be different throughout the first period T1 and the second period T2.

[0053] The control unit 20 may set a second display position different from the first display position so that the minimum gradation is assigned to the second display position during the second period T2. When the first display position can be selected as the second display position, the control unit 20 may select the second display position from display positions excluding the first display position. That is, during the second period T2, the control unit 20 may select the first display position at which the display gradation of the most deteriorated subpixel Pw obtained from the stress data is minimum, from among display positions excluding the first display position whose deviation amount from the normal display position is within the predetermined range AM.

[0054] The following describes how the stress amount changes due to frame image shifting. If the stress amount for that pixel increases, the brightness characteristics will deteriorate. Figures 5 and 6 are diagrams showing an example of how the stress amount ST changes due to frame image shifting. Suppose that subpixels Pa and Pb with different stress amounts ST are present on a single screen. Suppose that the stress amount STa0 of subpixel Pa is greater than the stress amount STb of subpixel Pb. In this case, the difference between the brightness RBa0 and RBb of subpixels Pa and Pb is perceived by the user as a brightness difference ΔRB (=RBb-RBa0).

[0055] In FIG. 5, a large stress ΔST1 is applied to subpixel Pa from this state. As a result, the luminance difference ΔRB1 (=RBb-RBa1) between subpixels Pa and Pb becomes large. On the other hand, in FIG. 6, subpixel Pa is caused to display a grayscale that results in the smallest stress amount ΔST2 within a specified range, thereby suppressing an increase in the stress amount ST. As a result, compared to FIG. 5, the difference in stress amount between subpixel Pa and subpixel Pb and other pixels is made smaller, and the luminance difference ΔRB2 (=RBb-RBa2) can be suppressed.

[0056] As mentioned above, increasing the shift amount M may cause a visual discomfort, for example, the image may appear different from the image that is originally intended to be displayed. Therefore, it is more practical to limit the shift amount M to within a predetermined range AM.

[0057] 7 is a diagram showing an example of a shifted frame image. This diagram includes stress distributions ST2 and ST3, pre-shift frame images Fs2 and Fs3, and post-shift frame images Fe2 and Fe3. For the stress distribution ST2, pre-shift frame image Fs2, and post-shift frame image Fe2, the minimum gradation is selected within a 7×7 square predetermined range AM of ±3 pixels (picture elements). Within the predetermined range AM, the frame image is shifted three pixels to the right and three pixels downward so that the minimum gradation is assigned to the most deteriorated subpixel Pw.

[0058] Increasing the predetermined range AM increases the shift amount M, which may result in an image that looks different from the image that was originally intended to be displayed. The stress distribution ST3, pre-shift frame image Fs3, and post-shift frame image Fe3 represent examples in which the image looks different from the image that was originally intended to be displayed as a result of shifting the frame image within the predetermined range AM0, which is a 16 x 16 square of ±8 pixels (picture elements).

[0059] Note that the display area R0 of many display devices 100 (e.g., televisions, PCs, notebook PCs, smartphones, and in-car navigation devices) is 1000 pixels or more in both length and width, so a shift amount M of about 10 pixels does not pose a significant problem in terms of visibility.

[0060] The most deteriorated subpixel Pw changes as the display continues. For example, in the case of the stress distribution ST4 in FIG. 8 , a shifted image Fe4 is displayed in accordance with the most deteriorated subpixel Pwa. Continuing this display results in a stress distribution ST5, in which the most deteriorated subpixel shifts from pixel Pwa to pixel Pwb. In this case, a shifted image Fe5 is displayed so that the increase in the stress amount of the most deteriorated subpixel Pwb is reduced. As a result, the increase in the stress amount of the entire screen can be suppressed.

[0061] 9 and 10 , by shifting the image so that the increase in the stress amount of the most deteriorated subpixel Pwa becomes smaller, the difference in the stress amount between the most deteriorated subpixel Pwa and the other most deteriorated subpixels Pwb becomes smaller, and ultimately the stress amounts of the other pixels become larger. In this way, in order to suppress the deterioration of the most deteriorated subpixel Pw (the pixel with the largest stress amount), it is preferable to shift the image in accordance with the change in the most deteriorated subpixel Pw. By repeating this, the deterioration rate of the subpixels Pi can be suppressed across the entire screen.

[0062] As described above, the display device 100 according to the first embodiment includes a display unit 10 having a plurality of sub-pixels Pi each including a light-emitting element, and a control unit 20 that controls the display unit 10, and the control unit 20 shifts the display position of a frame image within the display unit 10 over time, and the control unit 20 sets the display position according to the gradation data of the frame image and stress data corresponding to a group of sub-pixels within a predetermined region R1 of the display unit 10. This makes it possible to effectively suppress image burn-in on the display unit 10.

[0063] [Embodiment 2] A display device 100 according to embodiment 2 will now be described in detail. Fig. 11 is a flow diagram showing an example of frame image shifting processing. Fig. 12 is a schematic diagram showing an example of frame image shifting processing according to this shifting processing. Fig. 13 is a diagram showing an example of frame images to be shifted.

[0064] As mentioned above, if the shift amount M is large, the image to be displayed may fluctuate significantly, which may cause the user to feel uncomfortable. Also, if the shift frequency is high, the user may feel that the image flickers.

[0065] To avoid this, it is conceivable to insert an intermediate shift Fi (F1, F2) between the shift from the current display position Fs to the next display position Fe.

[0066] (1) Selection of Most Degraded Subpixel (Step S21) Based on the stress data, the control unit 20 selects the most deteriorated subpixel Pw from the subpixel group in the predetermined region R1 of the display unit 10 (Step S21). The details of this step are the same as those of Step S11 in the first embodiment, and therefore will not be described again.

[0067] (2) Determining the Final Shift Amount M (Final Display Position) (Step S22) The control unit 20 sets the first display position so that the minimum gradation is assigned to the most deteriorated subpixel Pw (Step S22). The details of determining the final shift amount M are the same as those of determining the shift amount M (display position) in the first embodiment (Step S12), and therefore will not be described again.

[0068] (3) Determining the Individual Shift Amount Mi (Display Position) and Individual Period Ti (Step S23) In the second embodiment, one or more shifts are performed before the shift to the final display position. In Figs. 12 and 13, as an example, two shifts are performed before the shift to the final display position. In other words, the third shift is the final shift. Generally, the nth shift (n: an integer of 2 or more) is the final shift. In other words, the following equation is established: M = M1 + ... + Mn

[0069] An individual shift amount Mi is set for each shift number i. For example, the individual shift amount Mi can be determined by dividing the final shift amount M by the shift number n. If the final shift amount M=(Δx, Δy), the i-th individual shift amount Mi can be expressed as follows: Mi=(Δx·i / n, Δy·i / n)

[0070] For example, when shifting three times to shift three pixels and six pixels in the horizontal and vertical directions, the individual shift amounts M1 to M3 are expressed as follows: M1=(2, 3) M2=(4, 6) M3=(6, 9)

[0071] In this way, if the final shift amount M is an integer multiple of the number of shifts, the individual shift amount Mi can be determined by dividing the final shift amount M by the number of shifts. On the other hand, even if the final shift amount M is not an integer multiple of the number of shifts, the individual shift amount can be determined based on the value obtained by dividing the total shift amount by the number of shifts. For example, when shifting by 5 pixels and 8 pixels in the horizontal and vertical directions through three shifts, the individual shift amounts M1 to M3 are expressed as follows: M1=(2, 3) M2=(4, 6) M3=(5, 8)

[0072] Here, as an example, the individual shift amounts M1 to M3 are set so as to result in a linear shift, although the shift does not have to be linear.

[0073] An individual period Ti corresponding to the individual shift amount Mi is set. The individual period Ti can be determined from the period T by the following formula, for example: Ti=T / n

[0074] The period T and the individual period Ti can be set appropriately. For example, in the case of a still image, the individual period Ti may be set to about one minute.

[0075] (3) Shifting of Frame Images (Steps S24 to S29) The frame images are shifted based on the determined individual shift amount Mi (Step S25). Within an individual period Ti, the frame images are shifted by the individual shift amount Mi. Within an individual period Ti, the frame images are shifted by the individual shift amount Mi every time the frame images are updated. Note that in order to count the number of shifts, the shift count i is set to an initial value (Step S24). Here, the initial value of the shift count i is set to 1.

[0076] As shown in FIGS. 12 and 13, the image is shifted in order so that display positions F1 and F2 are located between normal display position Fs and first display position Fe.

[0077] If the most deteriorated subpixel Pw changes during the period T, it is possible to stop shifting to the display position Fe and shift to a new display position Fe1. Figure 14 is a flow diagram showing an example of a control method for the display device 100 that takes such a case into consideration. When the frame image is updated ("YES" in step S26), it is determined whether the most deteriorated subpixel Pw has changed (step S31). If it is determined that the most deteriorated subpixel Pw has changed ("YES" in step S31), the process returns to step S21, and the most deteriorated subpixel Pw is selected. Except for this point, Figure 14 is similar to Figure 11, and therefore a detailed description will be omitted.

[0078] (4) Elapse of Period T (Step S29) When the period T has elapsed (Step S29), the period transitions from the first period T1 to the second period T2, and the most deteriorated subpixel is selected, the final shift amount M (final display position) is determined, the frame image is updated, the frame image is shifted, and so on.

[0079] As described above, in the display device 100 according to the second embodiment, the control unit 20 selects a display position different from the first display position and the second display position during the intermediate period between the first period T1 and the second period T2. This makes it possible to make the shift of the image on the display unit 10 less noticeable.

[0080] [Embodiment 3] A display device 100 according to embodiment 3 will now be described in detail. Fig. 15 is a diagram showing an example of changes in stress amount due to frame image shifting processing. Here, the frame image is shifted with attention focused on the color of the sub-pixel Pi. For example, if the degradation characteristics differ for each color of the sub-pixel Pi, it is conceivable to shift the frame image based on the color that is most susceptible to degradation. Since the sub-pixels Pi are generally composed of red (R), green (G), and blue (B), it is conceivable to classify them into RGB and select the most deteriorated sub-pixel Pw.

[0081] 15 shows an example of temporal changes in luminance at red (R), green (G), and blue (B) subpixels. If the blue subpixel is prone to degradation, it is conceivable to define the amount of stress based on the blue subpixel. In general, it is expected that red (R) and green (G) will be less susceptible to degradation due to stress than blue (B). In other words, the most deteriorated subpixel Pw and the shift amount M can be determined for the blue subpixel, which is prone to degradation in luminance characteristics.

[0082] For example, if the stress amount in pixel region P0a is "R=100, G=10, B=1" and the stress amount in pixel region P0b is "R=1, G=10, B=100," the most deteriorated subpixel Pw and the minimum gradation can be selected from the blue (B) subpixel. On the other hand, considering the proportions of RGB in white display, green (G) generally accounts for 70% of the total, so the most deteriorated subpixel Pw and the minimum gradation can also be selected from the green (G) subpixel. Regarding the color of the subpixel, for example, the following options (a) to (e) are possible.

[0083] (a) The subpixel group may include a plurality of red subpixels and at least one of a plurality of green subpixels and a plurality of blue subpixels, and the most deteriorated subpixel may be the subpixel having the largest stress data value among all the subpixels of all colors. The subpixel group may further include a plurality of white subpixels or a plurality of yellow subpixels.

[0084] (b) The subpixel group may include a plurality of blue subpixels and at least one of a plurality of red subpixels and a plurality of green subpixels, and the most deteriorated subpixel may be the blue subpixel having the largest stress data value.

[0085] (c) The subpixel group may include a plurality of green subpixels and at least one of a plurality of red subpixels and a plurality of blue subpixels, and the most deteriorated subpixel may be the green subpixel having the largest stress data value among the plurality of green subpixels.

[0086] (d) The subpixel group may include a plurality of red subpixels and at least one of a plurality of green subpixels and a plurality of blue subpixels, and the most deteriorated subpixel may be the red subpixel having the largest stress data value among the plurality of red subpixels.

[0087] (e) The subpixel group may include a plurality of red subpixels, a plurality of green subpixels, and a plurality of white subpixels or a plurality of yellow subpixels, and the most deteriorated subpixel may be the one having the largest stress data value among the plurality of white subpixels or the plurality of yellow subpixels.

[0088] As described above, in the display device 100 according to the third embodiment, the most deteriorated subpixel Pw and the minimum gradation are selected according to the color of the subpixel Pi, thereby more effectively suppressing image burn-in on the display unit 10.

[0089] [Example of implementation using software] The functions of the display device 100 (hereinafter referred to as the "device") can be realized by a program that causes a computer to function as the device, and a program that causes a computer to function as each control block of the device (particularly each part included in the control unit 20).

[0090] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The functions described in each of the above embodiments are realized by executing the program using the control device and storage device.

[0091] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.

[0092] Furthermore, some or all of the functions of the control blocks can be realized by logic circuits. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of the present invention. In addition, the functions of the control blocks can also be realized by, for example, a quantum computer.

[0093] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0094] REFERENCE SIGNS LIST 100 Display device 10 Display unit 20 Control unit 21 Gradation current conversion unit 22 Temperature coefficient calculation unit 23 Time sampling unit 24 Stress data storage unit 25 Position shift calculation unit 26 Gradation correction calculation unit 27 Signal processing unit

Claims

1. A display device including a display unit having a plurality of sub-pixels each including a light-emitting element, and a control unit for controlling the display unit, wherein the control unit shifts the display position of a frame image in the display unit over time, and the control unit sets the display position according to the gradation data of the frame image and stress data corresponding to a sub-pixel group in a predetermined area of the display unit.

2. The display device according to claim 1, wherein in a first period, the control unit selects a first display position at which the display gradation of the most deteriorated sub-pixel obtained from the stress data is minimized among the display positions where the shift amount with respect to the normal display position is within a predetermined range.

3. The display device according to claim 2, wherein in a second period, the control unit selects a second display position at which the display gradation of the most deteriorated sub-pixel obtained from the stress data is minimized among the display positions where the shift amount with respect to the normal display position is within a predetermined range, excluding the first display position.

4. The display device according to claim 1, wherein in the first period, based on the stress data, the control unit selects the most deteriorated sub-pixel from the sub-pixel group in the predetermined area, and sets the first display position so that the minimum gradation is assigned to the most deteriorated sub-pixel.

5. The display device according to claim 4, wherein in the second period, based on the stress data, the control unit selects the most deteriorated sub-pixel from the sub-pixel group in the predetermined area, and sets a second display position different from the first display position so that the minimum gradation is assigned to the most deteriorated sub-pixel.

6. The display device according to claim 4 or 5, wherein the first display position has a shift amount with respect to the normal display position within a predetermined range, and in the first period, the control unit selects the minimum gradation from the gradation data of the frame image within the predetermined range with reference to the most deteriorated sub-pixel.

7. The display device according to claim 6, wherein the second display position has a shift amount with respect to the normal display position within the predetermined range, and in the second period, the control unit selects the minimum gradation from the gradation data of the frame image within the predetermined range with reference to the most deteriorated sub-pixel.

8. The display device according to claim 3 or 5, wherein the most deteriorated sub-pixel does not change over the first period and the second period.

9. The display device according to any one of claims 3, 5, and 8, wherein the display gradation of the most deteriorated sub-pixel is the same over the first period and the second period.

10. The display device according to any one of claims 3, 5, and 8, wherein the display gradation of the most deteriorated sub-pixel is different between the first period and the second period.

11. The display device according to any one of claims 3, 5, and 8 to 10, wherein the light-emitting element of the most deteriorated sub-pixel is turned off in at least one of the first period and the second period.

12. The display device according to claim 3 or 5, wherein the most deteriorated sub-pixel changes between the first period and the second period.

13. The display device according to any one of claims 3, 5, and 8 to 12, wherein each of the first period and the second period is 1 minute or more.

14. The display device according to any one of claims 1 to 13, wherein the predetermined region is a region excluding the edge portion in the display unit.

15. The display device according to any one of claims 2 to 7, wherein the predetermined range is a deviation amount of 1% in the vertical scanning direction and 1% in the horizontal scanning direction with respect to the normal display position.

16. The display device according to claim 12, wherein the control unit selects a display position different from the first display position and the second display position during an intermediate period between the first period and the second period.

17. The display device according to any one of claims 2 to 7, wherein the frame video is a still image, and the same frame video is displayed at the first display position during the first period.

18. The display device according to any one of claims 2 to 7, wherein the frame video is a moving image, and a plurality of different frame videos are displayed at the first display position during the first period.

19. The display device according to claim 18, wherein the first display position is a display position where the display gradation of the most deteriorated sub-pixel is minimized with respect to the first frame video of the plurality of frame videos.

20. The display device according to any one of claims 2 to 7, wherein the sub-pixel group includes a plurality of red sub-pixels and at least one of a plurality of green sub-pixels and a plurality of blue sub-pixels, and the most deteriorated sub-pixel is the one having the largest stress data value among all-color sub-pixels.

21. The display device according to claim 20, wherein the sub-pixel group further includes a plurality of white sub-pixels or a plurality of yellow sub-pixels.

22. The sub-pixel group includes a plurality of blue sub-pixels and at least one of a plurality of red sub-pixels and a plurality of green sub-pixels, and the most deteriorated sub-pixel is the one having the largest stress data value among the plurality of blue sub-pixels. The display device according to any one of claims 2 to 7.

23. The sub-pixel group includes a plurality of green sub-pixels and at least one of a plurality of red sub-pixels and a plurality of blue sub-pixels, and the most deteriorated sub-pixel is the one having the largest stress data value among the plurality of green sub-pixels. The display device according to any one of claims 2 to 7.

24. The sub-pixel group includes a plurality of red sub-pixels and at least one of a plurality of green sub-pixels and a plurality of blue sub-pixels, and the most deteriorated sub-pixel is the one having the largest stress data value among the plurality of red sub-pixels. The display device according to any one of claims 2 to 7.

25. The sub-pixel group includes a plurality of red sub-pixels and a plurality of green sub-pixels, and a plurality of white sub-pixels or a plurality of yellow sub-pixels, and the most deteriorated sub-pixel is the one having the largest stress data value among the plurality of white sub-pixels or the plurality of yellow sub-pixels. The display device according to any one of claims 2 to 7.

26. The update period of the stress data is longer than the frame period and shorter than the first period. The display device according to any one of claims 2 to 7.

27. The current value of the light-emitting element included in the most deteriorated sub-pixel is set to a value corresponding to the gradation data and the stress data. The display device according to any one of claims 2 to 7.

28. The stress data is accumulated for each unit region including one or more sub-pixels. The display device according to any one of claims 1 to 27.

29. A control method for a display device provided with a display unit having a plurality of sub-pixels each including a light-emitting element, and shifting the display position of a frame image in the display unit over time, wherein the display position is set according to the gradation data of the frame image and the stress data corresponding to the sub-pixel group in a predetermined region of the display unit. A control method for a display device.

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