JP4701863B2 - Signal conversion method and signal conversion apparatus - Google Patents

Description

  The present invention relates to a signal conversion method and a signal conversion apparatus for driving a liquid crystal display device.

  Conventionally, signal conversion methods for driving a liquid crystal display device include those described in Non-Patent Document 1 and Patent Document 1.

  Note that “subpixel” refers to a region of a liquid crystal element including a single color filter, and “pixel” is configured by arranging a plurality of subpixels.

  First, Non-Patent Document 1 displays a display by combining a plurality of sub-pixels configured by a combination of RGBW (red, green, blue and white) color filters and liquid crystal elements in a panel surface and combining with a white backlight. The apparatus structure and signal processing system which obtain a screen are shown. Here, if the four subpixels of RGBW are arranged in the same size as the conventional pixel area (three subpixels of RGB), each subpixel area is reduced to three quarters. Since the W pixel has the wavelength distribution characteristics for the three RGB colors, the luminance of the display screen can be increased by 1.5 times from the relationship between the area ratio and the wavelength distribution characteristics. In addition, a signal conversion procedure is disclosed in which a common component of the input RGB signal (that is, the minimum value of the RGB signal) is replaced with the W signal in order to calculate the drive signal of the RGBW subpixel from the input RGB signal (video signal).

  Patent Document 1 discloses various arrangement methods of three-color sub-pixels composed of combinations of RGB three colors or RWB three colors selected from RGBW four colors and signal conversion procedures corresponding to the arrangement methods.

Japanese Patent Laid-Open No. 2004-199071 “Video Signal Display Method and Display Device” SID 2003, pages 1212-1215, TFT-LCD with R GBW Color System, Baek-woon Lee, etc.

  Both Non-Patent Document 1 and Patent Document 1 are intended to effectively use backlight emission by considering the wavelength transmission characteristics of RGBW sub-pixels of a panel in a liquid crystal display device. That is, W does not have RGB wavelength selectivity and can transmit the energy of three colors of RGB, so that the use of W pixels can improve the brightness of the display screen.

  Here, since the conversion from the input RGB signal to the panel-driven RGBW signal is the number of signal lines of 3 inputs and 4 outputs, there is a degree of freedom in the equation for signal conversion and a unique solution cannot be obtained.

  Therefore, Non-Patent Document 1 uses the common value (that is, the minimum value) of the input RGB signals as the drive signal for the W sub-pixel and the remaining RGB signal components as the drive signal for the RGB sub-pixel. Although there is a merit of simple signal conversion, there is no viewpoint of using the degree of freedom included in the equation to realize a specific evaluation index. Specifically, there is no evaluation index for reducing power consumption.

  All of these documents consider the wavelength distribution characteristics of the pixels on the panel side, but do not consider the wavelength distribution characteristics of the light emission on the backlight side. This is because all assume that white light such as a fluorescent tube is used as a backlight light source.

  For example, when displaying red, the transmittance of R is increased on the panel side, but the backlight turns on white, that is, all of RGB, and the wavelength distribution characteristic of the combination of both becomes red. In this case, the energy of the GB light included in the backlight is wasted.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a color signal conversion method and a color signal conversion device capable of improving the luminance at the time of white display and improving the image quality of the luminance reduction at the time of black display while reducing the power consumption of the display device. .

  In order to solve the above problems, a signal conversion apparatus and a signal conversion method of the present invention include a backlight composed of light emitting elements having light emission characteristics of R, G, and B wavelengths based on an input video signal. A means for calculating a backlight drive signal to be driven, and a panel drive signal for driving a panel composed of sub-pixels having R, G, B, and W wavelength transmittance characteristics based on the input video signal And means for calculating.

  Further, in addition to the above configuration, there is means for transmitting the backlight drive signal so that it precedes the video signal in time, and the means for calculating the panel drive signal calculates the panel drive signal from the backlight drive signal and the video signal. It is set as the structure to do.

  Further, a display control signal for controlling the inside of the display screen is included in the video signal.

  Further, the backlight drive signal is included in a part of the video signal in the display screen.

  Further, the input video signal is stored in a memory, and a panel drive signal for driving a panel composed of sub-pixels having R, G, B, and W wavelength transmittance characteristics based on the stored video signal Based on the input video signal, a backlight drive signal for driving a backlight composed of light emitting elements having light emission characteristics of R, G, and B wavelengths is calculated, and a panel drive signal and a backlight are calculated. The driving signal is output to the display device.

  The present invention can provide a signal conversion method and a signal conversion apparatus capable of improving the image quality of the brightness improvement during white display and the image quality reduction of brightness during black display while reducing the power consumption of the display device.

  Each example will be described below with reference to the drawings.

  One embodiment of the signal conversion apparatus of the present invention is shown in FIG.

  The present invention relates to a signal conversion device 1 for converting an input video signal 10 into a drive signal (a panel drive signal 13 and a backlight drive signal 14) for display using a display device 2. The present invention is characterized in that a signal for driving the display device 2 including the panel 26 and the backlight 28 is calculated so as to reduce power consumption.

  First, the configuration of the display device 2 to be driven will be briefly described. The panel 26 includes a combination of, for example, three types of RGB color filters having distribution characteristics within a wavelength range that can be sensed as visual characteristics, and liquid crystal elements for controlling the transmittance of the color filters. Here, in this embodiment, in addition to RGB (red, green and blue) color filters that divide the wavelength range, W (white) that does not divide the wavelength range is provided.

  Note that W (white) does not have wavelength distribution characteristics, but in the following description, four types of RGBW are treated as color filters. There is actually no color filter corresponding to the W sub-pixel, or a transparent filter or the like is used.

  A combination of any one of the color filters (monochromatic color filter) and a liquid crystal element is referred to as a sub-pixel, and covers a wavelength range, for example, a combination of three types of RGB or four types of RGBW sub-pixels, that is, a plurality of sub-pixels. A pixel formed from pixels is called a pixel. A large number of the pixels are arranged in the plane of the panel, and the wavelength distribution characteristic of each pixel is controlled by an external electric signal, so that the screen is displayed using the entire surface of the panel.

  The backlight 28 is constituted by an LED (Light Emitting Diode) or LD (Laser Diode) which is a semiconductor element. Compared with a conventional fluorescent lamp, the wavelength distribution characteristic is a shape close to a normal distribution having a single peak, so that the color purity is high, and the temporal response of the input electric signal and light emission is extremely fast. The backlight 28 can have the entire display screen as a single drive target, or can divide the plane into a plurality of areas and make each area an independent drive target. In the case of division into a plurality of areas, a plurality of drive signals are prepared. In any configuration, since much of the power consumption in the display device is consumed by the backlight, it is an issue to be solved to reduce the drive signal of the backlight.

Note that the layout of the RGBW sub-pixels in the panel surface is not limited. For example, as a visual characteristic, it is known that the resolution of brightness is higher than the resolution of color. Therefore, it is possible to arrange the panel so that the arrangement period of W sub-pixels is higher than the arrangement period of RGB sub-pixels. Specifically, instead of the RGBW combination, the pixel is configured by a combination of RGB and RWB, so that an increase in the number of subpixels can be suppressed while maintaining a pixel density within a certain area. Depending on the arrangement of sub-pixels on these panels, signal processing such as contour correction, smoothing, and color correction for improving display image quality can be performed. However, the present invention describes the contents of signal processing for improving image quality. It is not intended to limit.

  The panel 26 and the backlight 28 receive the panel drive signal 13 and the backlight drive signal 14 for driving the panel 26 and the backlight 28 from the signal conversion device 1, and are driven using the panel drive circuit 25 and the backlight drive circuit 27. The display output 11 is configured as a combination of both. When there is a non-linear characteristic called a gamma characteristic as a combination of both, it is a common practice to provide conversion means related to the gamma characteristic between the input signal and the display output. In the following description, for the sake of simplicity, it is assumed that the input signal and the display output have a linear characteristic, but if necessary, a conversion unit related to the gamma characteristic can be incorporated.

  Based on the input video signal 10, the signal conversion device 1 calculates the panel drive signal 13 and the backlight drive signal 14 for driving the panel and the backlight so as to reduce power consumption. In order to adjust the calculation time, the video signal 10 that temporarily stores the input RGB signal 12 included in the video signal 10 in the screen memory 21 and the input RGB signal 12 have the same contents as the image data. 10 is distinguished because the format may include a blanking period. The display device 2 receives the panel drive signal 13 and the backlight drive signal 14 and drives the panel 26 and the backlight 28 to generate a display screen. This relation is that the input RGB signal 12 included in the input video signal 10 is Ri, Gi, Bi, the panel drive signal RGBW signal is Rp, Gp, Bp, Wp, and the backlight drive signal RGB signal is Rb, Gb, Bb. Is expressed by the following equation.

[Equation 1]
Ri = Rp × Rb + Wp × Rb
Gi = Gp × Gb + Wp × Gb
Bi = Bp × Bb + Wp × Bb
Here, the backlight drive signal is set for the entire screen, whereas the panel drive signal is a signal set for each pixel. Therefore, the above expression is a relational expression for each pixel of the entire screen.

  Since the total number of signals of the panel drive signal 13 and the backlight drive signal 14 is larger than that of the input RGB signal 12, the drive signal cannot naturally be set uniquely. The present invention is characterized in that a solution is obtained so as to reduce power consumption. However, in order to display the frame screen at a fixed time period, the long processing time for obtaining the solution impairs the basic function of the display device. Therefore, it is an indispensable requirement for constructing a practical apparatus to use the above-described power consumption reduction index in combination with an index within a certain processing load instead of using it alone.

In consideration of the above conditions, the present invention drives a backlight composed of light-emitting elements having R, G, and B wavelength emission characteristics while referring to input signals (video signals) stored in the screen memory 21. The backlight drive signal calculation circuit 22, which is means for calculating the backlight drive signal to be calculated, calculates the backlight drive signal 14 and temporarily stores the result in the backlight drive signal storage circuit 24. Further, a panel drive signal calculation circuit which is a means for calculating a panel drive signal for driving a panel composed of sub-pixels having R, G, B, and W wavelength transmittance characteristics based on the input video signal. 23 calculates the panel drive signal 13 while referring to the screen memory 21 and the backlight drive signal storage circuit 24. Then, the display device is driven by a combination of the panel drive signal 13 and the backlight drive signal 14. It goes without saying that functions equivalent to those of the above circuit can be realized by software processing. Specific processing procedures and circuit operations are described below.

The input RGB signal is Ri, Gi, Bi, the panel drive RGBW signal is Rp, Gp, Bp, Wp, and the backlight drive signal RGB signal is Rb, Gb, Bb. In the following description, for the sake of simplicity, it is assumed that the screen is composed of pixels m and pixels n as shown in FIG. The procedure is divided into several for illustrative purposes.
Step 1:
The maximum values Rmax, Gmax, and Bmax of each color signal are calculated from the in-plane input RGB signals, and the temporary setting values (Rb ′, Gb ′, Bb ′) = (Rmax, Gmax, Bmax) of the backlight drive signals RGB And
Step 2:
Using the temporary setting values (Rb ′, Gb ′, Bb ′) of the backlight driving signal RGB, the temporary setting values (Rp ′, Gp ′, Bp ′) of the panel driving signal RGB of each pixel are inversely proportional to the following equations: To satisfy the relationship. Here, the notation of pixel m and pixel n is omitted.

[Equation 2]
Ri = Rb ′ × Rp ′
Gi = Gb ′ × Gp ′
Bi = Bb ′ × Bp ′
Obviously, if the backlight drive signal is set based on the maximum value in the plane of the input RGB signal, the amount of light emitted from the backlight will change from frame to frame. This has the effect of reducing power consumption while maintaining the display screen. At this time, the panel drive signal has the maximum amplitude (= 1) in the pixel having the maximum value in the display screen.
Step 3:
There is no problem even if display is performed using the temporary setting values (Rp ′, Gp ′, Bp ′) of the panel drive signal RGB obtained in the above procedure 2. Next, the minimum value in the screen of the temporary setting values is displayed. Is determined as a temporary setting value Wp ′ of the drive signal for the W sub-pixel. In addition, the description of the pixel m and the pixel n is abbreviated.

[Equation 3]
Wp ′ = MIN (Rp ′, Gp ′, Bp ′)
The provisional setting value Wp ′ is an RGB signal level that all pixels in the screen have in common, and can be replaced with white. However, since it is used for replacement, the temporarily set value Wp ′ may be less than Wp ′ and in the range of 0 or more. These relationships are expressed by the following equation, and the panel drive signal RGB is replaced with a value obtained by subtracting Wp ′ from the temporary setting values (Rp ′, Gp ′, Bp ′), and Wp ′ is newly added. Displays the input RGB signal. However, for the purpose of illustrating the principle, no calculation is required in the signal processing procedure.

[Equation 4]
Ri = Rb ′ × (Rp′−Wp ′) + Rb ′ × Wp ′
Gi = Gb ′ × (Gp′−Wp ′) + Gb ′ × Wp ′
Bi = Bb ′ × (Bp′−Wp ′) + Bb ′ × Wp ′
Step 4:
The above equation indicates the sharing ratio by RGB and W of the sub-pixels of the panel in order to display the input RGB signal. That is, the first term is the display output by the RGB sub-pixels, and the second term is the display output by the W sub-pixels. Then, it can be seen that the sharing ratio between the two is in a complementary relationship depending on the magnitude of the temporary setting value Wp ′ (when one is increased, the other is decreased). As described above, the provisional setting value Wp ′ may be selected within the range of 0 to Wp ′, so that the degree of freedom remains in setting the above-described sharing ratio.

  Here, in the present invention, the maximum value of the corrected signal of the temporary setting values (Rp ′, Gp ′, Bp ′) of the panel drive signal RGB is minimized by setting the Wp ′ of the W subpixel in the above equation. To. In order to satisfy the above condition when the maximum value of the provisional setting values (Rp ′, Gp ′, Bp ′) of the in-plane panel drive signal RGB is the maximum amplitude (= 1), Wp ′ = 0.5 It will be good. As a result, the upper limit of Wp ′ ≦ 0.5 is set for Wp ′.

[Equation 5]
Wp ′ = MIN (Wp ′, 0.5)
Step 5:
The correction of the drive signal of each color sub-pixel using Wp works in the direction of lowering the panel drive signal. Here, since the relationship between the drive signal of the panel and the backlight is inversely proportional, the correction of the panel drive signal can be reflected in the correction of the backlight drive signal. That is, the correction of the drive signal of the sub-pixel in the display screen can be used for reducing the backlight emission amount. As described in the procedure (2), the maximum value of the drive signal of the sub-pixel in the display screen is the maximum amplitude (= 1). If this is corrected by Wp ′, the amplitude is (1−Wp ′). It becomes. To make this value the maximum amplitude (= 1) again, it is sufficient to divide by (1−Wp ′). If the backlight drive signal is multiplied by (1-Wp ′) in an inversely proportional relationship, the relationship between the panel for reproducing the input RGB signal and the backlight drive signal can be maintained. The newly set backlight drive signal is as follows. Since the magnitude of (1-Wp ′) as the coefficient is 1.0 or less, the effect of reducing power consumption can be obtained.

[Equation 6]
Rb = Rb ′ × (1−Wp ′)
Gb = Gb ′ × (1−Wp ′)
Bb = Bb ′ × (1−Wp ′)
Step 6:
In order to display the input RGB signal using the light amount based on the backlight drive signal thus determined, a panel drive signal for each pixel in the plane is calculated. If the above-described coefficient (1-Wp ′) is used, it can be uniquely calculated as in the following equation.

[Equation 7]
Rp = (Rp′−Wp ′) / (1−Wp ′)
Gp = (Gp′−Wp ′) / (1−Wp ′)
Bp = (Bp′−Wp ′) / (1−Wp ′)
Wp = Wp ′ / (1-Wp ′)
Thus, the input RGB signal can be reproduced as in the following equation.

[Equation 8]
Ri = Rb × Rp + Rb × Wp
Gi = Gb × Gp + Gb × Wp
Bi = Bb × Bp + Bb × Wp
At this stage, the backlight drive signal that consumes most of the power consumption has already been calculated. Even if the coefficient (1-Wp ′) is not used in the above equation [Equation 7], the following equations 2 and 3 are satisfied along the procedures 2 and 3 so as to satisfy the relationship between the input RGB signal and the backlight drive signal. The panel drive signal can be obtained by performing the calculation of [Equation 4]. This means that the signal passed in steps 5 to 6 need only be the backlight drive signal (if the input RGB signal is common to all steps).
Step 7:
This completes the basic signal conversion. What can be noted here is that it is an implicit premise to obtain panel and backlight drive signals for faithfully reproducing input RGB signals. Therefore, if the premise of faithful reproduction is removed, the degree of freedom of signal setting can be increased from the viewpoint of improving image quality. By relatively changing the contribution of the W sub-pixel and the RGB sub-pixel obtained in the above procedure, an effect of changing the relationship between luminance and saturation is obtained.

  For example, brighter display can be realized by multiplying the signal of the W sub-pixel by a coefficient. Alternatively, a display with higher saturation can be realized by multiplying the RGB sub-pixel signal by a coefficient. By such a coefficient setting, the visual quality can be improved by producing a display screen. These coefficients can be set arbitrarily by the user observing the display screen, and a means for measuring the distribution characteristics of the video signal is prepared to set the image quality effect coefficient with some judgment criteria. It can also be configured.

  In the present invention, these color reproduction effects can be realized by correcting the drive signal obtained in the above procedure.

  Further, the above procedure can be classified into two, ie, procedure 1 to procedure 5 for calculating the backlight drive signal, and procedure 6 and procedure 7 for calculating the panel drive signal based on the backlight drive signal. The former backlight drive signal calculation procedure refers to the entire input RGB signal of the screen twice, and the latter panel drive signal calculation procedure refers to the entire input RGB signal of the screen once again and sums it up. Thus, by referring to the entire input RGB signal three times, both the resulting backlight drive signal and panel drive signal are calculated.

  In order to refer to the data of one screen three times, the present invention can perform the above procedure by temporarily storing the screen data in the memory and accessing the memory. Either an electric circuit or software can be used.

  In the above procedure, when the sub-pixels constituting the panel are three types of RGB, the backlight drive signal and the panel drive signal are obtained by performing steps 1 and 2 using the signal conversion device 1 of the present invention. Can be calculated. Although not shown in the above procedure, if the backlight can be driven in four types of RGBW, a procedure added to the above may be prepared. For example, although not shown, as a means for setting switching of whether the sub-pixels constituting the panel are 4 types of RGBW or 3 types of RGB, a switch for holding a set value, a register for writing the set value, or a memory By preparing the above variables, the signal processing procedure can be switched with reference to the setting values of these setting means. This switching means has an advantage that it can easily cope with diversification of display principles of the display device.

A numerical example of signal calculation is shown along the above procedure. First, as a first numerical example, the input RGB signal has the maximum amplitude. In the conventional RGB sub-pixel display device, display is performed with the drive signals of both the backlight and the panel being maximized. In the present invention, the display is as follows.
Numerical example 1
Pixel m (RmGmBm = 1, 1, 1), Pixel n (RnGnBn = 1, 1, 1)
Step 1:
Rmax = 1, Gmax = 1, Bmax = 1
(Rb ′, Gb ′, Bb ′) = (Rmax, Gmax, Bmax)
= (1,1,1)
Step 2:
Rpm '= 1, Gpm' = 1, Bpm '= 1
Rpn ′ = 1, Gpn ′ = 1, Bpn ′ = 1
Step 3:
Wp ′ = MIN (Rp ′, Gp ′, Bp ′)
= 1
Step 4:
Wp ′ = MIN (Wp ′, 0.5)
= 0.5
Step 5:
Rb = Rb ′ × (1−Wp ′)
Gb = Gb ′ × (1−Wp ′)
Bb = Bb ′ × (1−Wp ′)
Rb = 0.5, Gb = 0.5, Bb = 0.5
Step 6:
Rp = (Rp′−Wp ′) / (1−Wp ′)
Gp = (Gp′−Wp ′) / (1−Wp ′)
Bp = (Bp′−Wp ′) / (1−Wp ′)
Wp = Wp ′ / (1−Wp ′)
Rpm = 1, Gpm = 1, Bpm = 1, Wpm = 1
Rpn = 1, Gpn = 1, Bpn = 1, Wpn = 1
Accordingly, in the present invention, the backlight drive signal can be set to half the maximum amplitude while the drive signal of the RGBW sub-pixel is maximized. Since there is a margin in the amplitude of the backlight drive signal, display output exceeding the instruction of the input RGB signal can be performed using the margin. This can be set as the image quality calculation coefficient as described above.

Next, another numerical example is shown along the procedure.
Numerical example 2
Pixel m (RmGmBm = 1, 0.4, 0.4), Pixel n (RnGnBn = 0.7, 0.5, 0.3)
Step 1:
Rmax = 1, Gmax = 0.5, Bmax = 0.4
(Rb ′, Gb ′, Bb ′) = (Rmax, Gmax, Bmax)
= (1, 0.5, 0.4)
Step 2:
Rpm ′ = 1, Gpm ′ = 0.8, Bpm ′ = 1
Rpn '= 0.7, Gpn' = 1, Bpn '= 0.75
Step 3:
Wp ′ = MIN (Rp ′, Gp ′, Bp ′) = 0.7
Step 4:
Wp ′ = MIN (Wp ′, 0.5) = 0.5
Step 5:
Rb = 0.5, Gb = 0.25, Bb = 0.2
Step 6:
Rpm = 1.0, Gpm = 0.6, Bpm = 1.0, Wpm = 1.0
Rpn = 0.4, Gpm = 1.0, Bpm = 0.5, Wpn = 1.0
FIG. 3 shows a circuit configuration example for executing signal processing in the signal conversion apparatus 1.

The input RGB signal 32 is temporarily stored in the screen memory 21, and a temporary setting value of the backlight drive signal RGB is calculated by executing the procedure 1 using the temporary illumination calculation circuit 30. The signal processing from steps 2 to 4 is executed by the W signal calculation circuit 31 while reading the input RGB signal 33 from the screen memory 21. The signal processing of the procedure 5 is executed by the backlight drive signal calculation circuit 22, and the resulting backlight drive signal is stored in the backlight drive signal storage circuit 24. The storage means can use a register or a memory. In step 6, the panel drive signal 13 for each sub-pixel is generated from the accumulated backlight drive signal and the input RGB signal 34 read from the screen memory 21 using the panel drive signal calculation circuit 23. Then, the backlight drive signal 14 and the panel drive signal 13 are output together.

  Here, the formats of the output signals of the backlight drive signal 14 and the panel drive signal 13 will be described.

  In the signal conversion device 1 of this embodiment, it is indispensable to transmit a signal between the display device 2 including a panel and a backlight. The signal conversion device of the present invention may be configured either in a case where the signal conversion device is incorporated in the same housing as the display device or in a case different from the display device. In either case, the transmission and reception of signals is realized by providing the transmission device 3 that connects the two. In the device configuration in which the signal conversion device 1 and the display device 2 are in the same housing, the transmission device 3 that connects them may be a wiring on a circuit board or a wiring via an appropriate connector.

On the other hand, in a device configuration in which the signal conversion device 1 and the display device 2 are in separate housings, the transmission device 3 that connects both has a format conversion function based on some transmission format. Signals transmitted by the transmission device 3 are basically a panel drive signal 13 and a backlight drive signal 14. Alternatively, by providing the display device 2 with a panel signal calculation circuit, the input RGB signal 12 and the backlight drive signal 14 can be obtained.

  Here, the processing procedure described above is for a single screen frame, but the time response characteristics of the liquid crystal element may not always be stable in the screen frame period. Alternatively, when a fluorescent lamp is used as the backlight, it is difficult to adjust the luminance at the screen frame period. For example, when the panel drive signal is changed from the lowest value to the highest value and no response is made in the frame period, an error occurs in the display output.

  In order to reduce such an image quality deterioration factor that depends on time response, the present invention places a limit on the temporal change amount of the drive signal. This can be realized by preparing a limiter so that the magnitude of the inter-frame difference of the backlight drive signal calculated in the above-described procedure is not more than a predetermined upper limit value. Although the structure of this limiter is not shown, it is realized by preparing the backlight drive signal calculation circuit 22 with an inter-frame difference calculation means for the backlight drive signal, a register in which an upper limit value is set, and a comparison circuit for both. it can. If it is software, it can be realized by making a comparison with the upper limit value using an IF sentence or the like. In any configuration, the upper limit value can be set arbitrarily.

  Further, by storing a plurality of pieces of image data in the screen memory 21 in the image memory 21, the backlight drive signal calculation circuit 22 can calculate a plurality of backlight drive signals prior to actual display output. When the temporal change of the backlight drive signal calculated here is large, the backlight drive signal calculation circuit 22 can correct the backlight drive signal so as not to exceed the upper limit value in advance. The panel drive signal calculation circuit 23 uses the input RGB signal as a target signal and calculates the panel drive signal with reference to the corrected backlight drive signal. In this way, the present invention can realize the effect of reducing the image quality deterioration depending on the time response characteristic of the display device by providing an upper limit to the temporal change amount of the backlight drive signal.

  On the other hand, the signal conversion apparatus 1 and the display apparatus 2 may change the configuration of the signal processing means shared by them, and change the signal format of the transmission apparatus 3 that connects them together. Here, two types of sharing methods shown in FIG. 4 will be described.

  FIG. 4A shows a configuration in which the panel drive signal 13 and the backlight drive signal 14 are calculated up to the final stage and then transmitted from the signal conversion device 1 to the display device 2 using the transmission device 3. As described above, the panel drive signal 13 differs from the input video signal 10 in signal format and data amount. Therefore, in the device configuration in which the signal conversion device 1 and the display device 2 are in the same housing, the transmission device 3 is a dedicated signal line that connects the panel drive signal 13 and the backlight drive signal 14. For example, the signal line constituting the transmission device may be a wiring on a printed board.

In FIG. 4B, the input RGB signal 12 and the backlight drive signal 14 are transmitted using the transmission device 3, and the display device 2 on the receiving side uses the input RGB signal 12 and the backlight drive signal 14 to drive the panel. In this configuration, the signal 13 is calculated. Here, the transmission apparatus 3 uses the same signal format as the input video signal 10. For this reason, a backlight drive signal is written in a pixel constituting the video signal or a blanking period. As described above, according to the present invention, the backlight drive signal is added and transmitted while maintaining the transmission format of the video signal 10. Since the transmission format of the input video signal 10 is maintained, the transmission device 3 can be configured using a conventional video signal cable. This is a device configuration in which the signal conversion device 1 and the display device 2 are in separate housings, and is suitable for a configuration in which both are connected by a cable or the like. Here, even if the display device is a conventional CRT, display can be performed with the backlight drive signal added to the video signal. Thus, as described above, by using the existing transmission device 3 such as a transmission cable for video signals, it is possible to easily realize signal connection from the signal conversion device 1 to the display device 2.

  FIG. 5 shows signal processing and transmission timing at which the signal conversion device 1 and the display device 2 operate in the configuration of FIG. Here, the numbers (1) to (3) in the figure are the roles of the signal conversion apparatus 1, the number (4) in the figure is the role of the transmission apparatus 3, and the numbers (5) to (6) in the figure are. The role of the display device 2 is assumed. The signals transmitted from the signal conversion device 1 to the display device 2 are a backlight drive signal and an input RGB signal, and the display device 2 on the receiving side generates a panel drive signal from both signals. Description will be made along the numbers in the figure.

(1) Input RGB Signal The input RGB signal 12 is input for each screen according to the frame period of the video signal 10 and stored in the screen memory.

(2) Calculation of Backlight Drive Signal A backlight drive signal is generated from the input RGB signal 12 according to the procedure described above. This generation starts from the input start time of the input RGB signal 12 and further references the screen memory even after the input is completed.

(3) Transmission of input RGB signal and backlight drive signal The signal conversion apparatus 1 outputs the calculated backlight drive signal and the input RGB signal read from the screen memory without performing the calculation of the panel drive signal. Here, in consideration of the signal processing procedure on the receiving side, the backlight drive signal is output prior to the input RGB signal. This effect will be described later.

(4) Transmission Signals are transmitted by the transmission device 3. In general, if the distance is short, the transmission delay is negligible, but the transmission rate of a large-screen video signal tends to be extremely high. In order to reduce the influence of transmission delay (so-called skew), it is desirable to use a serial transmission path. The present invention is characterized by combining screen data and control data in a single format as described later, and is suitable for using a serial transmission path. As will be described later, this serial transmission line can maintain compatibility with the existing system.

(5) Reception of input RGB signal and backlight drive signal The backlight drive signal and input RGB signal are received via the above (3) and (4). Here, the backlight drive signal can be prepared before the input RGB signal arrives.

(6) Calculation of Panel Drive Signal Here, the panel drive signal is calculated from input RGB signals that are sequentially input with reference to the backlight drive signal. Here, if it is noted that the input RGB signals are three types of signals and the panel drive signals are four types of RGBW signals, it can be seen that the data amount has increased to four thirds. However, the panel drive signal after calculation is immediately transmitted to the panel drive circuit included in the display device 2, so that it is not necessary to arrange the data into a new data format or to accumulate data. That is, according to the present invention, there is an effect that it is possible to minimize the range in which the influence of the data amount that increases to the above-mentioned 4/3 is affected.

(7) Display by backlight drive signal and panel drive signal The backlight and the panel are driven using the backlight drive signal input via the transmission device 3 and the panel drive signal generated in the procedure (6), respectively. By doing so, a display output is obtained as a combination of both.

  FIG. 6 schematically illustrates a display period included in the video signal 10 and a blanking period attached thereto. The backlight drive signal is a set of signals that divide the plane depending on the set of the plane or the configuration of the backlight. On the other hand, the panel drive signal is a signal for each sub-pixel in the plane. Here, it is not included in the original input RGB signal, and can be newly set as the control signal 53 in the display screen or the control signal 52 in the blanking period in order to drive the display device. The present invention is a technique for solving a new problem born in order to realize a new display principle of controlling the amount of backlight in units of frames, and maintains compatibility with conventional video signals. It solves the problem.

  For example, the backlight drive signal can be written by a method of replacing or modulating a signal of a part of the sub-pixels of the input RGB signal. A new signal can be superimposed without causing an image quality change to the original input RGB signal.

  As described with reference to the timing chart, in the combination of the backlight drive signal and the input RGB signal, the backlight drive signal is transmitted prior to the input RGB signal. The control signal 52 for the frame blanking period shown in the figure can be set prior to the input RGB signal in the display screen area of the frame. On the other hand, the control signal 53 in the display screen shown in the figure cannot precede the input RGB signal in the display screen area of the frame. In order to solve this, the control signal (backlight drive signal) preceded by one frame period is set, and the control signal is stored in the backlight drive signal storage circuit 24 in the display device on the receiving side. Can achieve time alignment.

This
(A) A control signal such as a backlight drive signal can be transmitted in synchronization with the video frame.
(B) Existing video signal transmission means can be used.
(C) Various control signals can be read and written by means equivalent to video signals.
(D) Various control signals as well as video signals can be stored in the screen memory.
(E) Suitable for transmission.
There is a merit.

  The present invention uses the above-mentioned merits, for example, when a signal processing device such as a personal computer is used as a signal conversion device, by writing display data and control data to the screen memory, the conventional video signal format is maintained. The signal can be output to the display device as it is. In general, in a personal computer, the screen memory can be accessed from a CPU (Central Processing Unit) and a GPU (Graphic Processing Unit). The functions of the signal conversion apparatus of the present invention can be executed by software processing of these processing units. In such an apparatus configuration, the feature of the present invention can be observed as a backlight drive signal included in an output video signal.

  Note that RGB (red, blue, and green) color types are used in the description of the video signal, but the present invention does not limit the color types. For example, a combination of luminance and color difference, a combination of lightness, saturation, and hue, and subtraction Needless to say, CMY (cyan, magenta, yellow), which is a primary color, can be used. In video signal transmission / storage, some compression means may be used for the purpose of reducing the data capacity. It goes without saying that the present invention can be used in combination with such a compression means for video signals. Depending on the compression means, the data format of the compressed data may be determined, but these can be used.

  The present invention can switch the signal content to be transmitted based on the device characteristics of the display device. Simultaneously with the switching of the signal contents, it is possible to switch the role of signal processing between the signal conversion device and the display device via the transmission means. Further, a signal for identifying this switching can be transmitted together with the panel drive signal and the backlight drive signal using the transmission means. Thereby, in the display apparatus based on various principles, the effect which improves the compatibility of apparatus connection is realizable. Alternatively, compatibility of device connection can be realized without using a switching identification signal. In order to use the switching identification signal, a method such as modulation of a pixel signal in the screen or signal writing in a blanking period can be used, as in the case of setting the control signal in the video frame.

  The present invention can explicitly indicate the signal content transmitted using the identification signal. This is particularly effective for improving image quality when performing signal processing based on the display principle of the display device on the transmission side via the transmission means. Here, in order to perform signal transmission to the display device after performing advanced signal processing including processing of a video signal, a means for setting information related to the device characteristics of the display device can be prepared in advance. The setting means may include information receiving means from the display device, or may be set by a user of the display device.

  However, according to the present invention, when the information related to the device characteristics of the display device cannot be obtained, the signal content can be set so as to improve the compatibility. For example, a conventional CRT display device obtains a display output by emitting light by exciting a phosphor at each pixel position by in-plane scanning of an electron beam. Therefore, it is not necessary to separate the video signal into the panel drive signal and the backlight drive signal, but the present invention can transmit the input RGB signal and the backlight drive signal together. In this configuration, the CRT display device on the receiving side can realize display output by using the received input RGB signal as it is as a signal for display. Since the conventional display device does not have a means for determining the presence or absence of an identification signal, even if an identification signal indicating the content of the signal to be transmitted is set, the above-described operation will not be hindered. On the other hand, if the display device is configured to drive both the panel drive signal and the backlight drive signal, a panel drive signal is generated from the received input RGB signal and backlight drive signal based on the contents of the identification signal. can do. As described above, according to the present invention, it is possible to realize compatibility of operations in old and new display devices.

  As described above, the signal conditions and the operation contents transmitted between the signal conversion device and the display device via the transmission means can be determined according to a priority order that improves compatibility. Then, by making the determination condition a protocol that should be maintained between devices, the compatibility of the interconnections between various signal conversion devices and display devices can be improved.

  Hereinafter, another embodiment of the signal conversion device and the display device will be described with reference to FIG.

  FIG. 7 shows an apparatus configuration in the case where the signal conversion apparatus 1 described above is realized by a so-called personal computer (personal computer 5). Further, the display device 2 is connected using a video signal cable 15 in order to display the image data generated by the personal computer 5.

  The personal computer 5 includes a CPU 100 (central processing unit), a GPU 101 (graphic processing unit), a system memory 102, and a graphic memory 103 as basic elements, and generates display data or a television video signal according to a signal processing procedure described in the program. Signal processing such as reception. Programs and data are placed in the system memory 102 and read / written by the CPU 100. The GPU 101 accumulates the generated data in the graphics memory 103 and then outputs the data externally using the video signal cable 15 according to the format and timing of the video signal. Here, the arrangement of the color signals for each pixel is arbitrary, but for example, as shown in FIG.

  In the present embodiment, such an apparatus configuration not only decomposes an externally input video signal into a combination of a panel drive signal and a backlight drive signal, but also generates a pixel unit from model data called so-called computer graphics. The display data can be generated from the beginning by combining the panel drive signal and the backlight drive signal. Therefore, it has a feature that a wide dynamic range can be displayed, corresponding to the floating point format in which the panel drive signal is a decimal part and the backlight drive signal is an exponent part.

For example, the color signal C has a 16-bit configuration in which both of the decimal part A (1.0 or less) and the exponent part (an integer from 0 to 255) are combined to satisfy the relationship of C = A × 2 ^B as 8 bits. By using data, the digit position of the fractional part A can be shifted according to the size of the exponent part B, so that the dynamic range can be greatly expanded.

Here, each combination of the panel drive signal and the backlight drive signal is an 8-bit signal, and in some cases, the combination is the 16-bit combination of the panel drive signal RGB and the backlight drive signal RiGiBi shown in FIG. .

  Alternatively, assuming that the entire screen is within a certain range, the exponent B can be prepared for each screen instead of for each pixel. For example, as shown in FIG. 8 (3), the data format is one in which the panel drive signal RGB in the screen is combined with one backlight drive signal RiGiBi. The exponent B for each screen can be used as a backlight driving signal for the entire screen.

  In this embodiment, a means for storing or transmitting this floating point format data is prepared. When the exponent B is prepared for each pixel, if the above numerical example is used, 16 bits are required for each pixel. On the other hand, when an exponent B is prepared for each screen, an 8-bit fractional part is provided for each pixel, and an 8-bit exponent is provided for each screen.

  In this way, by configuring a transmission device that transmits a floating-point video signal between devices, the dynamic range of the floating-point video signal can be used in the display device. One feature of the present invention is a transmission apparatus that transmits a video signal in a floating-point format. In addition, writing a control signal for interpretation and use on the display device side in the display screen can be easily realized by describing the procedure in a program. The program may be executed by either the CPU 100 or the GPU 101. Since data of a plurality of frames can be accumulated depending on the capacity of the memory provided in the personal computer 5, the control signal can be written to an arbitrary address (that is, an arbitrary pixel) of an arbitrary frame stored on the memory. . In other words, since it is difficult to write data in the screen blanking period by the processing procedure described in the program, writing as data in the screen is a solution.

  Here, the writing of the control signal is distributed to a plurality of pixels in the screen synchronized with the control signal. Further, the selection of the dispersed pixels is changed between temporally consecutive frames. Employing such a distributed pixel selection method that suppresses the correlation between frames and a control signal writing method makes visual identification difficult. As a method for selecting dispersed pixels, the correlation between pixel positions between frames can be reduced by setting different pixel positions for each frame determined using random number generation means. Alternatively, it is possible to make it difficult to identify a signal change caused by writing a control signal by setting the pixel position where the change of the video signal in the screen is large. Alternatively, the pixels located on the four sides of the screen can be constantly used. These pixel positions can be calculated in common in both the control signal writing means and the reading means.

  Next, a device configuration example of the control signal writing method will be described with reference to FIG.

  The signal transmission difference 201 and the signal receiving device 20 are configured to transmit the video signal and the control signal through the transmission means 207. The control signal writing method and the reading method are reversible operations, and the components are the same. First, the graphic memory 203 for storing the screen data is provided, and the control signal read / write means 204 is used to read / write the control signal. Basically, the signal transmitter 201 only needs to write a control signal, and the signal receiver 202 only needs to read the control signal. Therefore, dedicated means may be provided for each. Means for managing the memory address of the graphic memory 203 are provided to set the pixel position for reading and writing the control signal. The output unit 205 and the input unit 206 are connected using the transmission unit 207.

  First, it is assumed that the control signal writing position has already been determined. It is assumed that a 1-bit signal is written in the pixel position. A reference signal of the pixel is calculated from a plurality of pixels adjacent to the pixel position. Then, the minimum bit of the reference signal is replaced with one bit of the control signal. On the other hand, in the reading means, the set control signal can be restored from the difference between the actual pixel signal and the reference signal from the adjacent pixel, assuming that the pixel position and the number of bits to be written are set in common. By performing such writing and reading at eight locations, an 8-bit control signal can be transmitted using screen data. This is rewriting of the minimum bit, and the influence on the image quality can be reduced by changing the pixel position for each frame. Needless to say, the above procedure can be realized by either hardware or software.

  For example, when the signal transmission device 201 is divided into a personal computer and the signal reception device 202 is a liquid crystal panel, the signal processing described above is described and operated by software on the personal computer, and the video signal and the control signal that are the signal processing results are processed. It can be transmitted and displayed on the liquid crystal panel side. Note that writing of the control signal can be performed on a frame preceding the frame synchronized with the control signal. By making the writing frame shift amount common between the transmission side and the reception side, synchronization can be maintained. Thus, the control signal of the frame can be received in advance prior to the reception of the video signal of the frame, thereby preparing for signal processing using the control signal prior to the reception of the video signal of the frame. Can be completed.

  For example, display data is generated and stored in a personal computer using a memory. Here, the configuration of the memory is generally read and written by software in units of three types of RGB, or four types of RGB α to which the α value of transmittance control for use in the synthesis process is added.

  The present invention is characterized in that RGBα4 types of data are read and written using the above memory configuration. For the sake of explanation, it is assumed that each signal is in units of bytes.

Here, as shown in FIG. 10, 3 types of RGB data is 3 bytes for 1 pixel, and 4 types of RGBW data is 4 bytes for 1 pixel. Therefore, if 12 pixels are the least common multiple of 3 and 4, then RGB pixels For example, three RGBW pixels can be arranged in a memory area of four. By using such a relationship, an address management means for calculating the pixel position in the screen memory and the order of the color signals in the pixel can be prepared. As shown in FIG. 10 (1), the RGB memory 110 and the RGBW memory 111 are physically the same, but the address management of the color signal written to the memory is performed, so that the RGB pixel and the RGBW pixel are switched and read / written. be able to. This makes it possible to read / write RGBW four types of data while using a conventional memory for reading / writing RGB three types of data. Even when signals stored in the memory are transmitted, RGBW four types of color signals can be transmitted using the RGB three types of signal transmission means in the same manner as the pixel arrangement in the memory. On the other hand, in the configuration for storing and transmitting RGBα4 types of data, the RGBW4 types of signals can be stored and transmitted by replacing the α signal with the W signal as shown in FIG.

  In the configuration of a personal computer, by combining software for generating image data, a screen memory for storing image data, and a video signal output means for outputting image data, processing can be performed by switching between RGB 3 type data and RGBW 4 type data. it can. Here, a code for identifying the RGB 3 type data or the RGBW 4 type data is added to the image data. This identification code adding method can be realized in the same manner as the control signal adding method described above. The operation can be switched so that the panel function of the receiving apparatus and the received identification signal are collided so as not to fail. For example, when the image data is RGBW and the panel pixel structure is RGB, an RGB signal is generated from RGBW by signal conversion on the receiving side and displayed. Alternatively, if the image data is RGB and the panel pixel configuration is RGBW, only RGB is extracted from the received RGBW and, if necessary, displayed after being multiplied by the above-described image quality effect coefficient, etc. You can also.

  Thereby, it is possible to output a video signal having a data format which is a feature of the present invention while using an existing personal computer device configuration. Further, if attention is paid to the fact that the RGBW four types of signals of the present invention can be transmitted while using the transmission means developed on the assumption that three types of RGB signals are transmitted, the transmission means can be a conventional wired or wireless transmission. Alternatively, a storage means such as a hard disk or a DVD can be used instead of the transmission means. If such a video signal storage means is used, calculation and writing of the control signal can be executed without depending on the display timing of the video signal.

  In addition, by calculating the backlight drive signal over a plurality of frames in advance, an upper limit can be set for the change in the amount of backlight light between frames by observing the temporal change in the backlight drive signal in advance. Further, temporal load distribution can be performed such that the panel drive signal is calculated at the time of display using the calculated backlight drive signal.

  In this manner, the video signal in which the control signal, which is a feature of the present invention, is output in a format and timing compatible with the existing video signal.

  The present invention relates to a color signal conversion method and conversion device for driving a liquid crystal display device, and relates to a television receiver, a projector, a monitor display device connected to a personal computer, a so-called personal computer television for performing television reception by a personal computer, and a game device. Applicable to, etc.

It is a figure which shows one Example of the signal converter concerning this invention. It is a figure explaining the signal processing procedure of the signal converter concerning the present invention. It is a figure which shows one Example of the circuit structure of the signal converter concerning this invention. It is a figure which shows the example of 1 structure of the transmission apparatus between the signal converter concerning this invention, and a display apparatus. It is a figure explaining the timing of the process sequence of the signal converter which concerns on this invention. It is a figure which shows an example of the signal format transmitted with the signal converter which concerns on this invention. It is a figure which shows the other Example of the signal converter which concerns on this invention. It is a figure explaining one example of data of the floating point format transmitted with the signal converter concerning the present invention. It is a figure which shows one structural example which reads / writes the control signal of the signal converter which concerns on this invention. It is a figure which shows the address management of the screen memory of the signal converter which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Signal conversion apparatus, 2 ... Display apparatus, 3 ... Transmission apparatus, 5 ... Personal computer (PC), 10 ... Video signal, 11 ... Display output, 12 ... Input RGB signal, 13 ... Panel drive signal, 14 ... Backlight Drive signal, 21 ... screen memory, 22 ... backlight drive signal calculation circuit, 23 ... panel drive signal calculation circuit, 24 ... backlight drive signal storage circuit, 25 ... panel drive circuit, 26 ... panel, 27 ... backlight drive circuit 28 ... Backlight, 30 ... Temporary illumination calculation circuit, 31 ... W signal calculation circuit, 32, 33, 34 ... Input RGB signal, 50 ... Video signal blanking period, 51 ... Video signal display period, 52, 53 ... Control Signal, 100 ... CPU
(Central processing unit) 101: GPU (graphic processing unit) 102: System memory 103: Graphic memory

Claims (10)

Means for calculating a backlight drive signal for controlling the light emission amount of each of the RGB light emitting elements of the backlight composed of light emitting elements having light emission characteristics of R, G, B based on the input RGB video signal; ,
Panel on the basis of the inputted RGB image signal and the backlight driving signal to control R, G, B, sub-pixels each transmittance of the panel consisting of sub pixels having respective wavelength transmittance characteristics of the W Means for calculating a drive signal,
The backlight drive signal and the panel drive signal are in an inversely proportional relationship,
Wherein W on the basis of the panel drive signal of the sub-pixel by reducing the backlight driving signal to increase the panel drive signal, Rukoto includes a signal conversion means for converting the backlight driving signal and the panel drive signal A signal converter characterized by the above. The signal converter according to claim 1,
In the calculation of the RGBW signal of the panel drive signal, the panel drive signal of the W subpixel is calculated so that the maximum value of the panel drive signal of the RGB subpixel is minimized . The signal converter according to claim 1,
In calculating the RGBW signal of the panel drive signal, the luminance and color of the display screen are changed by changing the contribution ratio of the panel drive signal of the RGB subpixel and the panel drive signal of the W subpixel to the input RGB video signal. A signal conversion device characterized by changing the degree relationship . The signal converter according to claim 3, wherein
A signal conversion apparatus characterized in that a relationship between luminance and saturation of a display screen in the calculation of the RGBW signal of the panel drive signal is arbitrarily set . The signal converter according to claim 1 ,
Setting means for setting switching of whether the sub-pixels constituting the panel are RGBW4 types or RGB3 types;
And a switching unit that switches a signal processing procedure of the signal converting unit by referring to a setting value of the setting unit. The signal converter according to claim 1,
A display device to which the backlight drive signal and the panel drive signal are input;
A signal conversion apparatus comprising: means for switching sharing of signal processing by the signal conversion means between the signal conversion apparatus and the display apparatus. The signal converter according to claim 1,
Means for transmitting the backlight drive signal calculated based on the input RGB video signal in one frame prior to the panel drive signal calculated based on the input RGB video signal in the one frame; A signal converter characterized by the above. The signal converter according to claim 1,
The input RGB video signal is a floating point format signal,
The panel drive signal is shown in the decimal part of the floating point format signal,
The signal converter according to claim 1, wherein the backlight driving signal is indicated by an exponent part of the floating point format signal. Store the input RGB video signal in memory,
A panel that controls the transmissivity of each sub-pixel of the panel composed of sub-pixels having R, G, B, and W wavelength transmissivity characteristics based on the stored RGB video signal and the backlight drive signal Calculate the drive signal,
Based on the input RGB video signal, a backlight driving signal for controlling the light emission amount of each of the RGB light emitting elements of the backlight composed of light emitting elements having R, G, B wavelength emission characteristics is calculated,
The backlight drive signal and the panel drive signal are in an inversely proportional relationship,
Converting the backlight drive signal and the panel drive signal to decrease the backlight drive signal based on the panel drive signal of the W sub-pixel and increase the panel drive signal;
A signal conversion method comprising outputting the panel drive signal and the backlight drive signal to a display device. The signal converter according to claim 9, wherein
Backlight driving signal the calculated, the signal conversion method characterized by after having temporarily stored in the backlight driving signal storage means, and outputs to the display device.

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