Display system

Abstract

To make inconspicuous color shift caused by abnormal light emission.SOLUTION: A display system comprises: a display unit that displays a pixel by a red sub-pixel, a green sub-pixel, and a blue sub-pixel; and a correction circuit 40 for setting a color temperature in white light emission. When the pixel displays a first gradation being the same gradation by the red sub-pixel, green sub-pixel, and blue sub-pixel, the correction circuit 40 sets a first color temperature as a white point, and when the pixel displays a second gradation being the same gradation and lower than the first gradation by the red sub-pixel, green sub-pixel, and blue sub-pixel, the correction circuit 40 sets a second color temperature different from the first color temperature as the white point.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a display system.

Background Art

[0002] In recent years, various electro-optical devices using electro-optical elements such as OLEDs (Organic Light Emitting Diodes) have been proposed. In this type of electro-optical device, individual differences may occur due to differences in manufacturing conditions and the like. Individual differences refer to, for example, a phenomenon in which even when a plurality of electro-optical device displays are driven under the same conditions, they are displayed in different colors. More specifically, it refers to a phenomenon in which, when a certain electro-optical device is driven by input gradation data to specify a certain gradation (brightness), the luminance by the electro-optical device and the luminance by another electro-optical device when the same gradation is specified are perceived as different.

[0003] Therefore, in order to make the luminance similar even with individual differences, a technique has been proposed in which input gradation data is once converted into output gradation data that can obtain the target luminance, and the electro-optical element is driven based on the output gradation data (see, for example, Patent Document 1). Further, in Patent Document 1, for each of the colors red, green, and blue, for example, white light is displayed at a bright gradation, the color temperature of the white light is measured, the output gradation is determined based on the measured color temperature, and adjustment is made so that the color temperature does not vary over the entire gradation is also described.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Some electro-optic elements have a white point that shifts from the white point that is specified when a low grayscale is selected, i.e., when it is specified to be darker, due to the effects of leakage current and other factors.

[0006] When using such electro-optic elements, a configuration that determines the output gradation based on the color temperature of white light measured at a bright gradation presents a problem: when a dark gradation is specified, the white point shifts, resulting in color shift from the perspective of a display device. [Means for solving the problem]

[0007] To solve the above problems, a display system according to one aspect of the present disclosure includes a display unit having a plurality of subpixels and displaying a color according to a gradation set for each of the plurality of subpixels, and a correction circuit that corrects the color displayed by the plurality of subpixels according to the gradation set for each of the plurality of subpixels, wherein the correction circuit corrects the color by using a first color temperature as the white point when the chromaticity of the color is above a predetermined threshold and all of the plurality of subpixels display white with the same first gradation, and corrects the color by using a second color temperature different from the first color temperature as the white point when all of the plurality of subpixels display white with a second gradation lower than the same first gradation. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram showing the configuration of the display system according to the first embodiment. [Figure 2] This is a perspective view showing an electro-optical device applied to a display system. [Figure 3] This block diagram shows the electrical configuration of an electro-optical device. [Figure 4] This diagram shows the configuration of a pixel circuit in an electro-optical device. [Figure 5] This is a diagram illustrating the operation of an electro-optical device. [Figure 6] This is a diagram illustrating abnormal light emission in an electro-optical device. [Figure 7] This figure shows the CIE chromaticity diagram and the color temperature trajectory of blackbody radiation. [Figure 8] This is a block diagram showing the configuration when an inspection device and an electro-optical device are connected in an inspection process. [Figure 9] This diagram shows the relationship between specific tonal ranges, color temperature, and CIE chromaticity for each rank. [Figure 10] This figure shows the color temperature shift at the rank 1 white point. [Figure 11] This figure shows the color temperature shift at the rank 2 white point. [Figure 12] This figure shows the color temperature shift at the rank 3 white point. [Figure 13] This figure shows the R, G, and B values ​​of the video data stored in the LUT. [Figure 14] This figure shows an example of rank determination. [Figure 15] This figure shows the relationship between specific gradations, color temperature, and CIE chromaticity for each rank in an electro-optical device applied to a display system according to the second embodiment. [Figure 16] This is a block diagram showing the configuration of the display system related to the modified example. [Figure 17] This figure shows the color temperature trajectory of blackbody radiation applied to a modified display system. [Figure 18] This is a diagram showing the headset in display system 1. [Figure 19] This diagram shows the optical configuration of the headset. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. Note that the dimensions and scale of each part in the drawings have been appropriately altered from those of the actual parts. Furthermore, the embodiments described below are preferred examples and therefore subject to various technically advantageous limitations. However, the scope of the present invention is not limited to these forms unless otherwise specified in the following description.

[0010] FIG. 1 is a diagram showing the configuration of the display system 1 according to the first embodiment, FIG. 2 is a perspective view showing the appearance of the electro-optical device 10 applied to the display system, and FIG. 3 is a diagram showing the electrical configuration of the electro-optical device 10. As shown in FIG. 1, in the display system 1, the host device 4 and the electro-optical device 10 are connected via an FPC (Flexible Printed Circuits) board 194. The host device 4 supplies video data Din, a synchronization signal Sync, etc. to the electro-optical device 10 via the FPC board 194. Note that the first embodiment is an example in which a correction circuit 40 is provided in the electro-optical device 10.

[0011] The electro-optical device 10 is a micro display panel that displays an image in, for example, a head-mounted display. The electro-optical device 10 includes a plurality of sub-pixels and a drive circuit that drives the sub-pixels. The sub-pixels and the drive circuit are integrated on a semiconductor substrate. The semiconductor substrate is typically a silicon substrate, but may be another semiconductor substrate.

[0012] As shown in FIG. 2, the electro-optical device 10 is housed in a frame-shaped case 192 having an opening 191. One end of the FPC board 194 is connected to the electro-optical device 10. A plurality of terminals 196 are provided at the other end of the FPC board 194. The plurality of terminals 196 are connected to the host device 4.

[0013] FIG. 3 is a diagram showing the electrical configuration of the electro-optical device 10. The electro-optical device 10 is roughly classified into a control circuit 30, a correction circuit 40, a data signal output circuit 50, a display unit 100, and a scan line drive circuit 120. In the display unit 100, m scan lines 12 are provided along the horizontal direction in the figure, and (3n) data lines 14 are provided along the vertical direction and electrically insulated from each scan line 12. Here, m and n are integers of 2 or more.

[0014] To distinguish between rows in scan line 12, they are sometimes referred to as rows 1, 2, ..., (m-1), and m in the diagram, starting from the top. Furthermore, to describe scan line 12 generally without specifying a row, an integer i (between 1 and m) is sometimes used to refer to it as the i-th row. Furthermore, to distinguish the columns in data line 14, they are sometimes referred to as columns 1, 2, 3, ..., (3n-2), (3n-1), and (3n) from left to right in the diagram. Note that data line 14 is grouped into groups of three columns. To explain the groups in a general way, if we use an integer j between 1 and n (inclusive), then the j-th group from the left contains data line 14 with a total of three columns: (3j-2), (3j-1), and (3j).

[0015] Sub-pixels 11R, 11G, and 11B are provided in correspondence with scan lines 12 arranged in m rows and data lines 14 arranged in (3n) columns. Specifically, sub-pixel 11R is provided in correspondence with the intersection of the scan line 12 in the i row and the data line 14 in the (3j-2) column. Sub-pixel 11G is provided in correspondence with the intersection of the scan line 12 in the i row and the data line 14 in the (3j-1) column. Sub-pixel 11B is provided in correspondence with the intersection of the scan line 12 in the i row and the data line 14 in the (3j) column.

[0016] Subpixel 11R emits red light, subpixel 11G emits green light, and subpixel 11B emits blue light. A single color pixel is represented by additive color mixing of the light emitted from subpixels 11R, 11B, and 11G. The electrical configuration of subpixels 11R, 11G, and 11B is identical. Therefore, unless there is a need to distinguish between them, the subpixels are described using the symbol 11.

[0017] As described above, the electro-optical device 10 is supplied with a synchronization signal Sync and video data Din from the host device 4. The synchronization signal Sync includes a vertical synchronization signal that instructs the start of vertical scanning of the video data Din, a horizontal synchronization signal that instructs the start of horizontal scanning, and a dot clock signal that indicates the timing of one pixel of the video data. The video data Din specifies the gradation of each subpixel to be displayed, for example, using 8 bits for red, green, and blue. The control circuit 30 controls each part based on the synchronization signal Sync. Specifically, the control circuit 30 generates various control signals to control each part.

[0018] In this embodiment, there is a one-to-one correspondence between the pixel to be displayed and one color pixel represented by three subpixels in the display unit 100. The luminance characteristics in the gradation shown by the video data Din do not necessarily match the luminance characteristics of the OLED contained in the subpixel 11. Therefore, in the LUT (Look Up Table) included in the correction circuit 40, for each color, the 8 bits of the video data Din are upconverted to, for example, 10 bits and output as video data Dout in order to make the OLED emit light at a luminance corresponding to the gradation shown by the video data Din. The correction circuit 40 corrects the color of the color pixel displayed by the three subpixels by converting the video data Din and outputting the video data Dout.

[0019] In the LUT, for each color, 10 bits of video data Dout are stored for each gradation from "0" to "255" in decimal representation of the video data Din. Then, the LUT reads out the video data Dout corresponding to the gradation of the video data Din and outputs it to the data signal output circuit 50. In addition, the red component of the video data Dout for each grayscale level is sometimes referred to as the R value, the green component as the G value, and the blue component as the B value. Furthermore, the detailed configuration of the correction circuit 40, and how the R, G, and B values ​​of the video data Dout are stored in relation to each grayscale of the video data Din, will be described later.

[0020] The scan line driving circuit 120 is a circuit for driving the sub-pixels 11, which are arranged in m rows (3n columns), one row at a time, according to the control of the control circuit 30. For example, the scan line driving circuit 120 supplies scan signals / Gwr(1), / Gwr(2), ..., / Gwr(m), and / Gwr(m) to the scan lines 12 of the 1st, 2nd, 3rd, ..., (m-1), and mth rows, respectively. Generally, the scan signal supplied to the scan line 12 of the ith row is denoted as / Gwr(i).

[0021] The data signal output circuit 50 is a circuit that outputs data signals via data lines 14 to subpixels 11 located in rows selected by the scan line drive circuit 120, according to the control of the control circuit 30. The data signal is a voltage signal obtained by converting the 10-bit video data Dout, which has been converted by the LUT of the correction circuit 40, into an analog. That is, the data signal output circuit 50 converts the video data Dout for one row corresponding to the subpixels 11 in columns 1 to (3n) of the selected row into an analog and outputs it in this order to the data lines 14 of columns 1 to (3n).

[0022] In the diagram, the data signals output to data line 14 in columns 1, 2, 3, ..., (3n-2), (3n-1), and (3n) are denoted as Vd(1), Vd(2), Vd(3), ..., Vd(3n-2), Vd(3n-1), and Vd(3n), respectively. Generally, the data signal supplied to data line 14 in column j is denoted as Vd(j).

[0023] Figure 4 is a circuit diagram showing the electrical configuration of the subpixel 11. As shown in the figure, the subpixel 11 electrically includes P-channel MOS type transistors 121 and 122, an OLED 130, and a capacitive element 140. In the description of subpixel 11, "electrically speaking" refers to the multiple elements that constitute the subpixel 11 and the connection relationships between those elements. This expression is used because, from a mechanical or physical perspective, the subpixel 11 includes elements that do not contribute to the electrical connection relationships.

[0024] OLED130 is an example of a light-emitting element, in which a light-emitting layer 132 is sandwiched between a pixel electrode 131 and a common electrode 133. The pixel electrode 131 functions as an anode, and the common electrode 133 functions as a cathode. In OLED130, when current flows from the anode to the cathode, holes injected from the anode and electrons injected from the cathode recombine in the light-emitting layer 132 to generate excitons, and white (achromatic) light is produced. The generated white light resonates in an optical resonator composed of a reflective electrode and a semi-reflective, semi-transparent layer (not shown), and is emitted at a resonant wavelength set to correspond to red light in the case of subpixel 11R. A colored layer (color filter) corresponding to the red light is provided on the light emission side from the optical resonator. Therefore, the light emitted from the OLED 130 passes through the optical resonator and the colored layer before being visible to the observer. Furthermore, if subpixel 11G is used, it emits light at a resonant wavelength set to correspond to green, passes through a colored layer corresponding to green, and is visible to the observer. If subpixel 11B is used, it emits light at a resonant wavelength set to correspond to blue, passes through a colored layer corresponding to blue, and is visible to the observer.

[0025] In the transistor 121 of the subpixel 11 in row i (3j-2), the gate node g is connected to the drain node of transistor 122, the source node is connected to the voltage Vel feed line 116, and the drain node is connected to the pixel electrode 131, which is the anode of the OLED 130. In the transistor 122 of the subpixel 11 in row i (3j-2) column, the gate node is connected to the scan line 12 of row i, and the source node is connected to the data line 14 of the corresponding (3j-2) column. The common electrode 133, which functions as the cathode of the OLED 130, is connected to the voltage Vct feed line 118. Furthermore, since the electro-optical device 10 is formed on a silicon substrate, the substrate potential of transistors 121 and 122 is set to a potential equivalent to, for example, the voltage Vel.

[0026] Figure 5 is a timing chart illustrating the operation of the electro-optical device 10. In the electro-optical device 10, the m-row scan lines 12 are scanned one line at a time in the order of the 1st, 2nd, 3rd, ..., mth line during the frame (V) period. More specifically, as shown in the figure, the scan signals / Gwr(1), / Gwr(2), ..., / Gwr(m-1), and / Gwr(m) are sequentially and exclusively set to L level by the scan line drive circuit 120 for each horizontal scanning period (H). In this embodiment, among the scan signals / Gwr(1) to / Gwr(m), the periods during which adjacent scan signals are at an L level are temporally separated. Specifically, after the scan signal / Gwr(i-1) changes from an L level to an H level, the next scan signal / Gwr(i) becomes L level after a period of time. This period corresponds to the horizontal retrace period.

[0027] In this explanation, the duration of one frame (V) refers to the period required to display one frame of the image specified by the video data Vid. The length of one frame (V) is 16.7 milliseconds, which corresponds to one cycle of the vertical synchronization signal if the vertical synchronization signal included in the synchronization signal Sync has a frequency of 60 Hz. The horizontal scanning period (H) is the time interval between the scan signals / Gwr(1) to / Gwr(m) becoming L levels in sequence. For convenience, in the diagram, the start timing of the horizontal scanning period (H) is set to approximately the center of the horizontal retrace period.

[0028] If one of the scan signals / Gwr(1) to / Gwr(m) is a scan signal, for example, the scan signal / Gwr(i) supplied to the i-th row scan line 12, becomes low level, then in the (3j-2)th column, the transistor 122 in the i-th row (3j-2) subpixel 11 becomes ON. As a result, the gate node g of the transistor 121 in the subpixel 11 becomes electrically connected to the (3j-2)th column data line 14.

[0029] In this explanation, the "on state" of a transistor or switch refers to a low-impedance state where the source node and drain node of the transistor, or both ends of a switch, are electrically closed. Conversely, the "off state" of a transistor or switch refers to a high-impedance state where the source node and drain node, or both ends of a switch, are electrically open. Furthermore, in this explanation, "electrically connected" or simply "connected" means a state in which two or more elements are directly or indirectly connected or coupled. "Electrically disconnected" or simply "disconnected" means a state in which two or more elements are not directly or indirectly connected or coupled.

[0030] During the horizontal scanning period (H) when the scanning signal / Gwr(i) is at an L level, the data signal output circuit 50 converts the R, G, and B values ​​corresponding to the subpixels in row i, column 1 to row i(3n) indicated in the video data Dout into analog data signals Vd(1) to Vd(n) and outputs them to the data lines 14 in columns 1 to (3n). For column (3j-2), the data signal output circuit 50 converts the R value d(i,3j-2) corresponding to the subpixel 11R in row i(3j-2) in the video data Dout into an analog data signal Vd(j) and outputs it to the data line 14 in column (3j-2). Furthermore, during the horizontal scanning period (H) when the scan signal / Gwr(i-1) one row prior to the scan signal / Gwr(i) is at an L level, the data signal output circuit 50 converts the R value d(i-1,3j-2) of the subpixel 11R in the (i-1) row and (3j-2) column into an analog data signal Vd(3j-2) and outputs it to the data line 14 in the (3j-2) column.

[0031] The data signal Vd(3j-2) is supplied to the gate node g of transistor 121 in subpixel 11R of row i (3j-2) via the data line 14 of column (3j-2), and is held by the capacitive element 140. As a result, transistor 121 supplies a current to the OLED 130 corresponding to the voltage between the gate node and source node. Even when the scanning signal Gwr(i) becomes high and transistor 122 turns off, the voltage of the data signal Vd(3j-2) is held at one end of the capacitive element 140, so current continues to flow through the OLED 130. Therefore, in the subpixel 11 of row i (3j-2), the OLED 130 continues to emit light at the voltage held by the capacitive element 140, i.e., the brightness corresponding to the grayscale, until a frame (V) period has elapsed, transistor 122 turns on again, and the voltage of the data signal is reapplied.

[0032] Although we have described the subpixel 11 in row i and column (3j-2) here, the OLED130s other than column (3j-2) in row i also emit light at the brightness indicated by the video data Dout. Furthermore, each OLED 130 of the subpixel 11 in rows other than row i will emit light at the brightness indicated by the video data Dout as the scanning signals / Gwr(1) to / Gwr(m) sequentially become L levels. Therefore, in the electro-optical device 10, during the period of one frame (V), each OLED 130 in all subpixels 11 from row 1 to column m (3n) emits light with the brightness indicated by the video data Dout, thereby displaying one frame of image.

[0033] As described above, the OLED130 itself emits white light, and after being colored by the optical resonator and colored layer, it is visible to the observer as red in subpixel 11R, green in subpixel 11G, and blue in subpixel 11B. Furthermore, in the subpixels 11 of the electro-optical device 10, ideally, as shown by the dashed line in Figure 6, the current flowing through the OLED 130 increases as the grayscale level increases, resulting in increased brightness. In other words, as the grayscale level decreases, the current flowing through the OLED 130 decreases, and if the lowest grayscale level is "0", then no current should flow through the OLED 130, and the brightness should be zero.

[0034] However, when using a self-emissive element such as OLED130 as the electro-optic element, abnormal light emission may occur due to leakage current at low grayscale levels. Abnormal light emission can be explained as follows: for example, as shown by the solid line in Figure 6, at low grayscale levels, the OLED130 emits light at a brightness higher than the brightness specified for that grayscale level.

[0035] Conventionally, the white point is set at a certain color temperature, for example, 6800K, regardless of the gradation. The white point does not refer to white as a color, but rather to the color temperature and display state that should be displayed in subpixels 11R, 11G, and 11B when the R, G, and B values ​​of the video data Dout are the same. For this reason, the white point includes gray and black, which humans perceive as achromatic colors, and the display state of the white point is sometimes referred to as white emission or white display.

[0036] If abnormal light emission occurs in a specific color, such as red, the white point shifts as the grayscale level decreases. Depending on the degree of the shift, it may become difficult to create video data Vout in which the white point has the same color temperature across all grayscale levels. Furthermore, there are cases where such color shifts vary greatly from one electro-optical device 10 to another, and there is a problem that in mass production, some electro-optical devices 10 will have color shifts that cannot be corrected.

[0037] Here, I will briefly explain two reasons why abnormal light emission occurs. First, the primary reason stems from the constituent layers of the light-emitting layer 132. As described above, the OLED 130 has a configuration in which the light-emitting layer 132 is sandwiched between the anode pixel electrode 131 and the cathode common electrode 133, and the light-emitting layer 132 is further composed of multiple layers. Specifically, the light-emitting layer 132, viewed from the anode pixel electrode 131, consists of, for example, a hole injection layer, a red light-emitting layer, a blue light-emitting layer, a green light-emitting layer, and an electron injection layer. Here, we have described the case where the red light-emitting layer is closest to the anode among the red light-emitting layer, blue light-emitting layer, and green light-emitting layer in the light-emitting layer 132. However, if the blue light-emitting layer is closest, it will contain a large amount of blue light. In subpixels 11R, 11G, and 11B, there are steps due to optical resonators, etc. In the light-emitting layer 132, these steps hinder the flow, making layers other than the hole-injection layer thinner. When the hole-injection layer becomes relatively thicker, due to carrier mobility, the hole injection capacity decreases and the electron injection capacity increases. When the electron injection capacity increases, exciton recombination is more likely to occur on the anode side. As a result, the emission intensity of the red light-emitting layer on the anode side increases, and a larger red component is included.

[0038] Next, the second reason is due to the step created by the optical resonator. The distance between the reflective electrode and the common electrode 133 in the optical resonator increases in stages in the order of subpixels 11B, 11G, and 11R. As a result, at the periphery of subpixel 11R, that is, in the part of subpixel 11R adjacent to other subpixels 11G and 11B, the step creates a localized thinning of the light-emitting layer 132 between the pixel electrode 131 and the common electrode 133. Current flows more easily in the areas where the light-emitting layer 132 is thinned. In the flat areas without steps, i.e., the areas where the red component is emitted in the subpixel 11R, even a minute current that does not emit light or emits only a very small amount of light will cause light to flow more easily in the areas where the light-emitting layer 132 is thinned by the steps, making it visible. If this emission wavelength satisfies the resonance conditions of the optical resonator in the subpixel 11R, it becomes more easily visible.

[0039] In this embodiment, the white point is set according to the gradation, along the blackbody radiation color temperature locus Bdr in the CIE chromaticity diagram shown in Figure 7. The blackbody radiation color temperature locus Bdr will be simply referred to as the blackbody locus Bdr. Generally, colors on the blackbody locus Bdr are easily perceived by humans as white, including achromatic colors. Therefore, even if the coordinates of the white point in high gradation and low gradation differ in the CIE chromaticity diagram, if it lies on the blackbody locus Bdr, it is less likely to cause discomfort. By utilizing this, even in low gradation states, i.e., when the current flowing through the OLED130 is small, the white point can be set to a point on the blackbody locus Bdr with a reproducible color temperature. By creating the video data Dout so that it is perceived as white, including achromatic colors, in those low gradation states, color shifts can be made less noticeable even if abnormal light emission occurs. Furthermore, abnormal red color appears in the low-gradation area. When light is present, the lower the gradation, the more the color temperature is set along the blackbody locus Bdr, moving away from the white reference color temperature point, for example, 6800K, in the direction of decreasing color temperature.

[0040] In low-gradation color gamuts, if there is significant variation between individual electro-optical devices 10, multiple white point settings become necessary. Therefore, in this embodiment, data for identifying individual differences is acquired during the post-manufacturing inspection process of the electro-optical device 10, and based on this data, the correction circuit 40 determines a rank for setting the white point according to the individual difference. The determined rank is classified according to the degree of color gamut in low-gradation areas and is used to set the white point to match the color gamut.

[0041] Figure 8 is a block diagram showing the relationship between the correction circuit 40 and the functional blocks of the inspection device 60 used in the inspection process. In the inspection process, the inspection device 60 is connected to the correction circuit 40 of the electro-optical device 10. The inspection device 60 is a computer that controls the measuring device by executing a program using a central processing unit such as a CPU (Central Processing Unit). The execution of this program constructs the low-gradation data acquisition unit 610 and the high-gradation data acquisition unit 620.

[0042] In the inspection device 60, the low-gradation data acquisition unit 610 causes the electro-optical device 10, which is the target for creating the video data Dout, to emit light at a level corresponding to a low gradation, and acquires and stores data such as brightness, chromaticity, and current value from the measuring device when the device is illuminated. Furthermore, data such as luminance, chromaticity, and current values ​​measured during low-gradation emission will be used in the rank determination described later. Also, a low gradation level refers to a level where the red, blue, and green gradations are relatively low, i.e., a dark level. For the second reason mentioned above, if abnormal emission occurs in red at the periphery of subpixel 11R, it may be possible to emit light at a dark level in a single color, such as green or blue, where such abnormal emission does not occur.

[0043] The high-gradation data acquisition unit 620 acquires and stores 10 bits each of the R, G, and B values ​​of the video data Dout corresponding to the highest gradation of "255" in red, green, and blue in the electro-optical device 10 to be created. The video data Dout corresponding to "255" gradation is acquired, for example, as follows: The inspection device 60 causes the electro-optical device 10 to emit light by changing the red, green, and blue video data Dout, and determines the combination of R, G, and B values ​​of the video data Dout that results in the design chromaticity and brightness. The design chromaticity is, for example, the chromaticity where the x value is 0.309 and the y value is 0.319 in the CIE chromaticity diagram, which is the white point on the blackbody locus Bdr at a color temperature of 6800K.

[0044] The correction circuit 40 includes a set value storage unit 410, a rank determination unit 420, a gradation setting unit 430, and a LUT 440. The setting value storage unit 410 stores the measurement data acquired by the low-gradation data acquisition unit 610 and the R, G, and B values ​​of the video data Dout acquired by the high-gradation data acquisition unit 620, which are transferred from the inspection device 60. In other words, the setting value storage unit 410 of the electro-optical device 10 stores the data measured by the electro-optical device 10 by the inspection device 60.

[0045] The rank determination unit 420 determines the rank type of the electro-optical device 10 from the measurement data during low-gradation emission stored in the set value storage unit 410, as described later. In this embodiment, there are three rank types: rank 1, rank 2, and rank 3. For each rank, data on the color temperature and chromaticity (x and y values) of the blackbody locus Bdr set when white light is emitted are associated with a specific gradation from "0" to "255," for example, for gradations "31," "47," "63," "127," and "255" as shown in Figure 9, and these data are stored in the rank determination unit 420.

[0046] In Figure 9, rank 1 represents an electro-optical device 10 in which the red component tends to increase as the gradation decreases, and the color temperature of the white point is set to decrease as the gradation decreases. In this example of rank 1, there are three types of color temperatures. Also, the gradation referred to here is used when white light is emitted, so the R, G, and B values ​​are the same. In terms of the CIE chromaticity diagram, rank 1, as shown in Figure 10, is characterized by a gradual decrease in the color temperature of the white point as the gradation progresses from high to medium to low levels.

[0047] Rank 3 in Figure 9 represents an electro-optical device 10 in which the red component tends to remain almost unchanged even when the gradation is low, and in which only one color temperature is used to set the white point, even when the gradation is low. In the CIE chromaticity diagram, rank 3, as shown in Figure 12, maintains a constant white point color temperature even when transitioning from high tones to medium tones and low tones. Note that if the white points overlap, the image becomes illegible; therefore, in Figure 12, the white points have been slightly shifted to prioritize readability.

[0048] Rank 2 in Figure 9 represents an electro-optical device 10 where the red component at lower tonal levels is positioned between Rank 1 and Rank 2. It shares the same characteristics as Rank 1 in that the color temperature of the white point decreases as the tonal level decreases. However, Rank 2 has only two types of white point color temperatures, which is fewer than Rank 1. Rank 2, as shown in Figure 11 of the CIE chromaticity diagram, is characterized by a smaller change in the color temperature of the white point when transitioning from high tones to medium tones and low tones compared to Rank 1.

[0049] Rank 1 or Rank 2 is an example of Rank A, where there are multiple color temperatures set for white light emission, depending on the tone. Rank 3 is an example of Rank B, where there is only one color temperature set for white light emission, regardless of the tone.

[0050] When the rank determination unit 420 determines the rank type of the electro-optical device 10, it supplies color temperature and chromaticity data for a specific gradation corresponding to that rank type to the gradation setting unit 430. This sets the white point for a specific gradation. The gradation setting unit 430 first calculates the R, G, and B values ​​of the video data Dout corresponding to a specific gradation using the data stored in the setting value storage unit 410. That is, the setting value storage unit 410 stores the measurement data for low gradation emission and the R, G, and B values ​​of the video data Dout corresponding to the "255" gradation, so the gradation setting unit 430 calculates the R, G, and B values ​​of the video data Dout corresponding to a specific gradation.

[0051] The gradation setting unit 430 then calculates the R, G, and B values ​​of the video data Dout corresponding to gradations other than the specific gradation, using the R, G, and B values ​​of the video data Dout corresponding to the specific gradation as a node. That is, the gradation setting unit 430 calculates the R, G, and B values ​​of the video data Dout corresponding to gradations other than the specific gradation by interpolating them with the R, G, and B values ​​of the video data Dout corresponding to the specific gradation. In this way, the gradation setting unit 430 determines the R, G, and B values ​​of the video data Dout, corresponding to each of the gradations from "0" to "255". Then, the gradation setting unit 430 sets the R, G, and B values ​​of the video data Dout, corresponding to each of the gradations from "0" to "255", into the LUT 440.

[0052] Figure 13 shows an example of video data Dout stored in LUT440. In this example, when the target electro-optical device 10 is rank 1, the R, G, and B values ​​of video data Dout corresponding to specific grayscale levels "31", "47", "63", "127", and "255" are calculated, and then the R, G, and B values ​​of video data Dout corresponding to grayscale levels other than the specific grayscale levels are obtained by interpolation.

[0053] An example of rank determination in the rank determination unit 420 will now be explained. As shown in Figures 10 to 12, the higher the rank, the smaller the color temperature change of the white point in low gradation. This point is used to determine the rank.

[0054] Figure 14 is a diagram illustrating the determination of ranks. First, in the CIE chromaticity diagram, color gamut L1 corresponding to rank 1, color gamut L2 corresponding to rank 2, and color gamut L2 corresponding to rank 3 are predetermined. Color gamuts L1, L2, and L3 are color gamuts that the electro-optical device 10 can represent in low gradation, and are all represented by triangles.

[0055] In simple terms, the rank determination unit 420 determines that the electro-optical device 10 under inspection is rank 1 if, when the electro-optical device 10 emits only blue light at a low gradation, the X value of the chromaticity, shown by the white circle in the figure, is less than threshold x1 and greater than or equal to threshold x2. The rank determination unit 420 determines that the electro-optical device 10 under inspection is rank 2 if the X value of the chromaticity when emitting blue light at a low gradation is less than threshold x2 and greater than or equal to threshold x3, and determines that the electro-optical device 10 under inspection is rank 3 if it is less than threshold x3. The threshold x1 is the x-value at which the color temperature is lowest in the blackbody locus Bdr within the L1 color gamut. Threshold x2 is the x-value at which the color temperature is lowest in the blackbody locus Bdr in the L2 color gamut, and similarly, threshold x3 is the x-value at which the color temperature is lowest in the blackbody locus Bdr in the L3 color gamut.

[0056] According to the first embodiment, the color temperature of the white point is set to shift along the blackbody locus Bdr according to the gradation. Therefore, even if abnormal emission occurs in red at low gradations, and the degree of such abnormal emission varies greatly from one electro-optical device 10 to another, the color shift caused by such abnormal emission can be made less noticeable.

[0057] In the first embodiment, the electro-optical device 10 showed a tendency for the color temperature of the white point to decrease as the gradation level decreased. However, abnormal emission is not limited to red light, as described above. Specifically, in the light-emitting layer 132, if the blue light-emitting layer is closest to the anode among the red light-emitting layer, blue light-emitting layer, and green light-emitting layer, abnormal emission may occur in blue light. When abnormal emission occurs in blue light in the electro-optical device 10, the color temperature of the white point increases as the gradation level decreases. Therefore, a second embodiment will be described that addresses the color shift in the electro-optical device 10, in which the color temperature of the white point increases as the gradation decreases.

[0058] Figure 15 shows the color temperature and chromaticity data in the blackbody locus Bdr associated with specific gradations in ranks 1, 2, and 3 determined by the rank determination unit 420 in the second embodiment.

[0059] In Figure 15, rank 1 applies to the electro-optical device 10, where the blue component increases as the grayscale level decreases. On the other hand, rank 3 applies to the electro-optical device 10, in which the blue component hardly changes even when the gradation is reduced. Rank 2 is applied to the electro-optical device 10, where the blue component when the gradation is low is located between rank 1 and rank 2.

[0060] The rank of an electro-optical device 10 in which the color temperature of the white point increases as the gradation decreases may be determined by measuring the chromaticity of the target electro-optical device 10 when it emits only red light at low gradation, i.e., only colors in which no abnormal emission occurs, and determining which of the ranges indicated by the thresholds x1, x2, and x3 shown in Figure 14 the x-value of the chromaticity belongs to.

[0061] According to the second embodiment, even if abnormal light emission occurs in blue at low gradations, and the degree of such abnormal light emission varies greatly from one electro-optical device 10 to another, the color shift caused by such abnormal light emission can be made less noticeable.

[0062] The first and second embodiments described above (hereinafter referred to as "embodiments, etc.") can be modified or applied in various ways as follows.

[0063] In the embodiments, the white point for each gradation was defined as a point on the blackbody locus Bdr in the CIE chromaticity diagram, but it is not necessarily required to be on the blackbody locus Bdr. Generally, when comparing two colors, if the distance (Δu'v') in color space is greater than 0.02, humans can perceive the difference between those two colors. In other words, when comparing two colors, if the distance (Δu'v') in color space is less than 0.02, humans cannot perceive the difference between those two colors. This distance (Δu'v') is also called the color difference. Therefore, when setting different color temperatures for each grayscale level, it is sufficient to set a point where the color difference (Δu'v') from the blackbody locus Bdr is 0.02 or less. A color difference (Δu'v') of 0.02 or less from the blackbody locus Bdr means the range from the positive locus Bdru to the negative locus Bdrl, centered on the blackbody locus Bdr in Figure 16.

[0064] In this embodiment, there are three rank categories, but at least two categories are sufficient. Increasing the number of rank categories allows for compatibility with electro-optical devices 10 with different tendencies, but it complicates rank determination and increases the amount of data that needs to be prepared.

[0065] In the embodiments described, the correction circuit 40 is provided in the electro-optical device 10, but as shown in Figure 17, the correction circuit 40 may also be provided in, for example, a higher-level device 4. In a configuration where the correction circuit 40 is provided in the higher-level device 4, the LUT 440 within the correction circuit 40 converts the video data Din to video data Dout, and the electro-optical device 10 displays the video based on the video data Dout.

[0066] In a configuration where the correction circuit 40 is provided in the higher-level device 4, it is assumed that the higher-level device 4 and the electro-optical device 10 are used as a pair. Such an assumption can be seen, for example, in the head-mounted display described below. Furthermore, in a configuration where the correction circuit 40 is provided in the higher-level device 4, the inspection device 60 is connected to the paired higher-level device 4 during the inspection process, so that the R, G, and B values ​​of the video data Dout for each grayscale are stored in the LUT 440, similar to the embodiments described above.

[0067] Next, we will describe electronic devices to which the display system 1 according to the embodiment is applied. The electro-optical device 10 is suitable for applications requiring small-sized pixels and high-definition display. Therefore, we will explain using a head-mounted display as an example of an electronic device.

[0068] Figure 18 shows the appearance of display system 1 applied to a head-mounted display, and Figure 19 shows the optical configuration of the headset of the head-mounted display. The headset 300 has, externally, the same features as ordinary eyeglasses, including temples 310, a bridge 320, and lenses 301L and 301R. Furthermore, as shown in Figure 19, the headset 300 is equipped with an electro-optical device 10L for the left eye and an electro-optical device 10R for the right eye near the bridge 320, behind (below in the figure) the lenses 301L and 301R. In this example, the host device 4 and the electro-optical devices 10L and 10R are connected via cable 360, rather than via the FPC board 174 shown in Figures 1 and 17. Furthermore, in this example, the host device 4 also functions as the controller for the head-mounted display.

[0069] The image display surface of the electro-optical device 10L is positioned to the left in Figure 19. As a result, the image displayed by the electro-optical device 10L is emitted in the 9 o'clock direction in the figure via the optical lens 302L. The half mirror 303L reflects the image displayed by the electro-optical device 10L in the 6 o'clock direction while transmitting light incident from the 12 o'clock direction. The image display surface of the electro-optical device 10R is positioned to the right, opposite to the electro-optical device 10L. As a result, the image displayed by the electro-optical device 10R is emitted in the 3 o'clock direction in the figure via the optical lens 302R. The half mirror 303R reflects the image displayed by the electro-optical device 10R in the 6 o'clock direction while transmitting light incident from the 12 o'clock direction.

[0070] In this configuration, the wearer of the headset 300 can observe the images displayed by the electro-optical devices 10L and 10R in a see-through state, superimposed on the outside environment. Furthermore, in this headset 300, if the left-eye image is displayed by the electro-optical device 10L and the right-eye image is displayed by the electro-optical device 10R, the wearer can perceive the displayed images as if they had depth and three-dimensionality.

[0071] The higher-level device 4 may include a correction circuit 40 for the electro-optical device 10L and a correction circuit 40 for the electro-optical device 10R, or the electro-optical device 10L may include a correction circuit 40 and the electro-optical device 10R may include a correction circuit 40. Furthermore, the inspection device 60 may be configured to include elements of the correction circuit 40 other than the LUT 440.

[0072] Furthermore, in addition to head-mounted displays, the electronic devices to which display system 1 is applied can also be used in electronic viewfinders in video cameras and interchangeable-lens digital cameras, personal digital assistants, watch displays, and light bulbs in projection projectors.

[0073] From the above description, preferred embodiments of this disclosure can be understood, for example, as follows. For the sake of ease of understanding each embodiment, the reference numerals in the drawings are conveniently included in parentheses below, but this does not mean that the present invention is limited to the illustrated embodiments.

[0074] A display system (1) according to one embodiment includes a display unit (100) having a plurality of subpixels (11R, 11G, 11B) and displaying a color according to a gradation set for each of the plurality of subpixels (11R, 11G, 11B), and a correction circuit (40) that corrects the color displayed by the plurality of subpixels (11R, 11G, 11B) according to the gradation set for each of the plurality of subpixels (11R, 11G, 11B), wherein the correction circuit (40) corrects the color by using the first color temperature as the white point when the chromaticity of the color is above a predetermined threshold and when all of the plurality of subpixels display white with the same first gradation, and when the chromaticity of the color is below a predetermined threshold and when all of the plurality of subpixels display white with a second gradation lower than the same first gradation, the correction circuit (40) corrects the color by using the second color temperature, which is different from the first color temperature, as the white point.

[0075] In the display system (1) relating to the specific embodiment 2 of embodiment 1, the first color temperature and the second color temperature correspond to the color temperature trajectory of blackbody radiation. Specifically, the color temperature is not limited to points along the color temperature trajectory of blackbody radiation; it is also acceptable for points outside the color temperature trajectory of blackbody radiation to have a color difference that is imperceptible to humans.

[0076] In the display system (1) according to specific embodiment 3 of embodiment 2, the first color temperature is higher than the second color temperature. Also, in the display system (1) according to specific embodiment 4 of embodiment 2, the first color temperature is lower than the second color temperature.

[0077] In the display system (1) according to specific embodiment 5 of embodiment 1, the correction circuit (40) has a gradation setting unit (430), and the gradation setting unit (430) sets the first color temperature and the second color temperature.

[0078] In the display system (1) according to a specific embodiment 6 of embodiment 5, the correction circuit (40) has a rank determination unit (420), which determines whether the color gamut is at least A rank or B rank according to the low-gradation color gamut below the color threshold, and the gradation setting unit (430) sets multiple color temperatures to be set when displaying white according to different same gradations if the rank determination unit (420) determines it to be A rank, and sets one color temperature to be set when emitting white light if it determines it to be B rank. [Explanation of Symbols]

[0079] 1...Display system, 10...Electro-optical device, 11R, 11G, 11B...Subpixel, 12...Scan line, 14...Data line, 40...Correction circuit, 100...Display unit, 420...Rank determination unit, 430...Gradation setting unit, 440...LUT.

Claims

1. a display unit having a plurality of sub-pixels and displaying colors according to gradations set for each of the plurality of sub-pixels; a correction circuit that corrects the colors displayed by the plurality of sub-pixels in accordance with the gradations set for each of the plurality of sub-pixels; Equipped with The correction circuit when the chromaticity of the color is equal to or greater than a predetermined threshold, correcting the color by setting a first color temperature when all of the plurality of sub-pixels display white at the same first gradation as a white point; When the chromaticity of the color is less than a predetermined threshold, the color is corrected by using a second color temperature different from the first color temperature as a white point when all of the plurality of sub-pixels display white at a second gradation lower than the same first gradation. Display system.

2. The first color temperature and the second color temperature correspond to a color temperature locus of blackbody radiation. The display system of claim 1 .

3. The first color temperature is higher than the second color temperature. The display system of claim 2 .

4. The first color temperature is lower than the second color temperature. The display system of claim 2 .

5. The correction circuit A gradation setting unit is provided, The gradation setting unit Setting the first color temperature and the second color temperature The display system of claim 1 .

6. The correction circuit A rank determination unit is provided, The rank determination unit determining whether the color is at least A rank or B rank according to a color gamut of low gradations equal to or less than a predetermined threshold value of the color; The gradation setting unit when the rank determination unit determines that the display is of rank A, a color temperature to be set when displaying white is set to a plurality of color temperatures according to different gradations; If the color temperature is determined to be B rank, the color temperature to be set when displaying white is set to one. The display system of claim 5 .

Images