KR20040108043A - Color wheel spoke control apparatus in the TV and method - Google Patents

Abstract

PURPOSE: An apparatus and a method for controlling a spoke of a color wheel in a reflection type image display device are provided to control the spoke of the color wheel so as to use also a spoke section, thereby improving brightness and enlarging color gamut. CONSTITUTION: R, G, and B input signals are mapped by a gamut mapping process in a color gamut mapping operation part. A spoke section control part decides whether a spoke section is to be used or not according to levels of the mapped R, G, and B signals. When it is decided that the spoke section is to be used, a control signal is inputted to a color signal processing part. Herein the color signal processing part uses the spoke section of a color wheel corresponding to the control signal and then, reduces the light quantities corresponding to the spoke section added according to the levels of the mapped R, G, and B signals.

Description

Color wheel spoke control apparatus and method in reflective image display apparatus

The present invention relates to an apparatus and method for controlling the use of spoke sections of a color wheel (i.e., sections in which light rays touch the boundary of each RGB color gamut) in an image display apparatus using a color wheel. It is about.

Recently, the image display device of the latest technology that exceeds the limit of the existing CRT TV has been in the spotlight. One example is a video display device implemented using reflective display elements such as DLP (Digital Light Processing) and LCOS. The DLP is a high-definition of 2.76 million pixels by combining advanced technology with optical and video circuit systems. It is defined as a projection engine system for a third generation projector (projection TV) for realizing high image quality.

The reflective display system uses a method of displaying the color gamut of RGB by focusing light rays from one light source onto the color wheel, unlike the conventional CRT displaying the color gamut using RGB three electron guns. The obtained RGB color signals are reflected on the screen by reflecting them using a digital micro-mirror device (DMD), an LCOS, or the like as a micro reflector assembly. Such a system is a digital display technology without color fading or bad pixels, and is evaluated as a third generation projection model following the CRT (Crown Tube) and LCD (Liquid Crystal Display) methods.

Among the reflective image display apparatuses, a basic configuration of a DLP TV using a DMD is illustrated in FIG. 1. Referring to the drawings, the DLP TV system includes one light source 110, a color wheel 120 composed of three color gamuts of RGB, a DMD 130 reflecting color signals transmitted through the color wheel, and reflected from the DMD. It consists of an optical lens 140 for adjusting the color signal. This shows only the components related to the color wheel and other detailed TV internal components are omitted from the illustration and description.

The light source 110 focuses a white beam including all three RGB components to the color wheel 120. The color wheel 120 is a filter for filtering color signals. The color wheel 120 includes an R region for transmitting only an R signal, a G region for transmitting only a G signal, and a B region for transmitting only a B signal. This represents a configuration of a conventional color wheel, and does not necessarily need to be implemented in three RGB color gamuts, and may be implemented in an area that transmits a W (white) signal as it is.

The color signal transmitted from the color wheel 120 is directly directed to the DMD 130 through an optical lens (not shown). The DMD 130 is composed of an aluminum micromirror 130a located in each memory cell implemented as a Complementary Metal Oxide Semiconductor (CMOS) Static Random Access memory (SRAM), each of which has two states. ("on" and "off") to switch to move, it serves to reflect the digital image on the screen for the light transmitted from the color wheel 120.

On the other hand, in such a reflective image display system, processing of the boundary surface of each color gamut in the color wheel 120 becomes a problem, that is, unlike the case of processing the input signal in the pure RGB region, the light source 110 In the case where the focused beam spot uses a section (hereinafter referred to as a "spoke section") that touches the interface between RGB regions (the interface between RG, GB, and BR regions), the hue is changed. There was a problem.

In order to solve this problem, conventionally, the input RGB signal is mapped into a pure RGB color gamut so as not to take a signal having a level corresponding to the spoke section, and then divided into 0 to 255 levels during 8-bit driving.

That is, salpimyeon in the structure of the color wheel shown in Figure 3, the prior art does not use the full RGB region (R _T, G _T, B _T region) pure, except for each of the spoke section (figure On Srg, Sgb, Sbr interval) There is a problem in that the luminance of each color signal is lower than when using the entire RGB region by mapping and using it in the RGB region (R _P , G _P , B _P region).

An object of the present invention is to expand the respective luminance and color gamut by controlling the spokes of the color wheel to use the spoke section of the color wheel to solve the above problems. In addition, it is another object to achieve a color balance by linearly mapping in the mapping step for all the color signals to control the spoke.

1 is a general configuration diagram of a reflective image display device;

2 is a block diagram showing an internal configuration of a reflective image display device using a color wheel spoke according to the present invention;

3 is a view showing a color wheel used in the reflective image display device according to the present invention;

4A is a view showing the maximum color gamut level and the input signal level of the R-G color gamut when the spokes of the blue color gamut are unavailable;

4B is a view showing the maximum color gamut level and input signal level of the R-G color gamut when one of the spokes of the blue color gamut is available;

4C is a view illustrating a maximum color gamut level and an input signal level of the R-G color gamut when all the spokes of the blue color gamut are available;

5 is a view showing a white light output level according to the present invention compared to the conventional scheme,

6 is a view showing an extended color gamut as an effect of the present invention as compared to the conventional method.

A color wheel spoke control apparatus in a reflective image display system using a color wheel according to the present invention includes a color gamut mapping calculator configured to map an input RGB signal to a predetermined filter ratio of R, G, and B at a predetermined compression ratio, and the color. The spoke section controller determines whether the spoke section is used according to the level of the RGB signal mapped by the area mapping operation unit, and if the spoke section controller determines that the spoke section is used, the spoke section is added as much as the spoke section added according to the level of the mapped RGB signal. It characterized in that it comprises a color signal processing unit for reducing the amount of light.

On the other hand, the color wheel spoke control method in a reflective image display system using a color wheel according to the present invention, the step of performing a color gamut mapping by calculating a predetermined compression ratio for the input RGB signal, a specific spoke according to the level of the mapped RGB signal And determining to use a section and outputting an output RGB signal subtracted from the spoke signal corresponding to the mapped signal level when it is determined to use the specific spoke section.

Unlike the conventional method, in the present invention, after the input RGB signal is mapped into the entire RGB region, the spoke interval is used for the signal having a level exceeding the pure RGB region among the mapped signals, and the amount of light in the spoke interval is reduced. Zoom in to maintain the saturation of the image.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the color wheel spoke control device and control method according to the present invention.

First, Figure 2 is a simplified block diagram showing the configuration of the apparatus for controlling the spoke according to the present invention and Figures 4a to 4c is a case of assuming that the B signal as a signal of a certain range in the rectangular coordinate system with the RGB signal as the axis The RG plane is shown.

In FIG. 2, when the RGB signal is input, the color gamut mapping calculator maps the RGB signal to a constant compression ratio. The color gamut mapping means converting a signal having a predetermined color band so as to be output under another color band. A mapping process performed by the color gamut mapping operation unit will be described.

4A shows the RG plane when the input B signal level is the signal level of a section in which none of the B spoke sections (between GB and BR regions) can be used. Taking P1 as an example, since the point P1 is an input signal exceeding AR _P which is a pure R region, one spoke segment of R (spoke segment between RG regions) should be used to express this. Using the spoke section between the RG regions in this way, the color signal of the used spoke is added to the R and G signals as much as the amount of light used, and thus the chroma is increased compared to the input signal. A treatment to reduce the amount of light is performed.

When this is expressed as an expression, Rm = Ri-Asr, Gm = Gi-Asg, and Bm = Bi, and when expressed in the drawing, P1 'is obtained by subtracting Asg and Asr from P1. Here, the subscript m denotes a mapped signal, and i denotes an input signal, Asr, Asg, and Asb, respectively, the amount of light in the RGB spoke section. Hereinafter, the symbols and the subscripts are used in the same meaning.

In general, the processing of the mapped signal is simple as described above, but the RGB signal of a specific level is not processed the same. That is, referring to P4 located at the lower end of the straight line ④ represented by the linear equation Gi = Ri * (Asg / Arp) in FIG. 4A, the G signal is obtained when the spoke is mapped using the spoke section. Subtracting Asg, the amount of G spoke light, is negative (ie, mapped to P4 '). Since such negative numbers are inexpressible data, there is a problem that saturation correction cannot be performed as a result. Therefore, in this section, the maximum color gamut mapping level is limited to a certain range. In Fig. 4A, the straight line? A is the maximum color gamut mapping level of this section.

Meanwhile, in the method of mapping in the color gamut mapping operation unit, unlike the conventional method, since the entire RGB area is used in the present invention, the compression ratio is changed. The compression ratio is expressed by the following formula: [compression ratio = maximum color gamut level / maximum input signal level]. The maximum color gamut level and the maximum input signal level can be observed in FIGS. 4A, 4B, and 4C.

Common lines 1, 2, 3, and 4 in Figs. 4A to 4C represent boundaries according to the level of the input G signal. On the other hand, the lines ①a to ④a, ①b to ④b, and ①c to ④c which connect each straight line represent the maximum color gamut levels in the section, respectively.

Referring first to FIG. 4A, as described above, FIG. 4A shows the R-G plane when the input B signal level is the signal level of a section in which none of the B spoke sections can be used. That is, it becomes the R-G plane shown about the section of Bi <Ri * (Asb / Arp) on the plane of Bi and Ri. In the figure, straight line ① is Gi = Ri, straight line ② is Gi = Ri * Agp / (Arp + 2Asr), straight line ③ is Gi = Ri * 2Asg / (Arp + Asr), straight line ④ is Gi = Ri * (Asg / Arp It is represented by the linear equation of (), the linear equation with Gi and Ri as variables.

Since the area where P3 exists in the section below the straight line ④ cannot be spoke reduced after the color gamut mapping as described above, the mapping is possible only for the Ri in the straight line ④a. Therefore, when straight line (a) is Gi value below the straight line (4), it shows the maximum mapping level. Therefore, if the compression ratio is obtained in this section, the maximum input level of Ri is Art and the maximum mapping level is Arp, so the compression ratio is (Arp / Art). If this is expressed as an expression for each RGB signal, it is as follows.

Next, in the section between the straight lines ② and ③, Gi also has a signal level of a certain size, so it is easy to map using one spoke section and reduce the amount of light in the section. This is as described above with respect to the P1 point. Therefore, the straight line ②a having the linear equation Ri = Arp + Asb becomes the maximum mapping level. When the compression ratio is obtained by using the straight line ②a and the mapping RGB signal is obtained, the following equation is obtained.

When Ri and Gi are at the level where one spoke section should be used in common, i.e., in the section between the straight line ① and the straight line ②, since the Ri and Gi have a constant signal level, mapping is performed using one spoke section. It has a maximum mapping level equal to the interval between the straight lines ② and ③ without any preparation to reduce the amount of light in the interval. Therefore, the mapping RGB signal in this section is as shown in Equation (2).

Next, in the section between the straight line ③ and the straight line ④, the straight line ③a becomes the maximum mapping level. In the case of the signal level existing on the right side of the straight line ③a, that is, in the case of P2 and P3 in the drawing, the color signal level does not differ significantly, but the mapping result is respectively mapped to P2 'and P3'. As a result, color tone imbalance can occur, so the signal level that can be mapped is limited to the left of the straight line a. The straight line ③a is represented by the linear equation Ri = Gi * (Asr * Asg) + Arp-Asr. Using this, a mapped RGB signal is obtained as follows.

Such a section is a section connecting a straight line ④ or less section and a line 3 or more section, and becomes a boundary surface in which the maximum mapping level which can be expressed changes from straight line ④a to straight line ②a. In this section, if the Ri signal at the Arp + Asr level (ie, the extension line of the straight line ②a) is set as the mapping level as before, the points P2 and P3 where the color signal levels are not significantly different are mapped to P2 'and P3', respectively. However, the Ri signal level is greatly different, and as a result, color imbalance may occur. Therefore, in the present invention, tonal balance can be achieved by mapping the straight line a as the maximum mapping level with a constant compression ratio.

Next, referring to FIG. 4B, FIG. 4B shows a Ri-Gi graph in the case of a Bi signal having a level capable of using one B-spoke section in the signal processing process for Ri. That is, on the plane of Bi and Ri, an R-G plane is shown for a section in which Ri * (Asb / Arp) ≦ Bi <Ri * 2 (Asb / Arp). In the figure, straight line ① is Gi = Ri, straight line ② is Gi = Ri * Agp / (Arp + 2Asr), straight line ③ is Gi = Ri * 2Asg / (Arp + 2Asr), straight line ④ is Gi = Ri * Asg (Arp + Asr) is represented by the linear equation. Since the B-spoke section of one of the Bi color gamuts can be used in FIG. 4B, the maximum mapping level is wider than that of FIG. 4A. That is, in the section below straight line ④, the maximum mapping level becomes straight line ④b. The straight line ④ b is represented by the plane equation Ri = Bi * (Asr / Asb) + Arp-Asr. Therefore, when the mapping RGB signal is obtained,

It is expressed as

Next, the maximum mapping level becomes a straight line ②b between the straight line ② and the straight line ③. If the mapping RGB signal in this case is obtained, it is as follows.

In this case, since the B spoke section and the G spoke section can be used one by one, the mapping is possible by using both spoke sections with respect to Ri.

Next, if we search for the section between the straight lines ③ and ④, which are the boundaries of the two sections, the maximum mapping level of the section becomes the straight line ③b. This is to achieve tonal balance. The mapping RGB signal mapped at a constant compression ratio using the straight line b as the maximum mapping level is obtained as follows.

Next, when the section between the straight line ① and the straight line ② is examined, FIG. 4B becomes a straight line ①b unlike the maximum mapping level of FIG. 4A. This is because only one B-spoke section can be used, so only one G-spoke section can be used. In this case, the plane equation used as the maximum mapping level is the smaller of the planes Ri = Bi * (Asr / Asb) + Arp and Ri =-(Gi-Agp) * (Asr / 2Asg) + Art that pass through the lines ①a and the line ①b. Becomes Accordingly, the mapped RGB signal is expressed as follows.

Next, FIG. 4C illustrates a case where all of the B-spoke sections can be used. In other words, the signal level of Bi is Bi ≧ Ri * 2 (Asb / Arp). In the figure, straight line ① is Gi = Ri, straight line ② is Gi = Ri * Agp / (Arp + 2Asr), straight line ③ is Gi = Ri * 2Asg / (Arp + 2Asr), straight line ④ is Gi = Ri * Asg / ( Arp + Asr). Obtaining the RGB signal mapped to each section as described above, as follows.

Section ④ below straight line

Interval between straight lines ④ and ③

Interval between straight line ① and straight line ②

Section where Bi => 3Ri * (Asb / Arp) between straight line ① and straight line ②, section between straight line ② and ③ (Bypass section)

Rm = Ri, Gm = Gi, Bm = Bi

The above-described equations describe the RGB characteristics and the color gamut mapping method divided by the intervals of the Ri, Gi, and Bi signal levels. The color gamut mapping calculator calculates the mapping RGB signal with respect to the input RGB signal in the above-described manner, and outputs the mapping RGB signal to the color signal processor and the spoke section controller. The spoke section controller determines which spoke section is used according to the level of the mapping RGB signal and outputs the spoke section to the color signal processor.

The color signal processing unit comprehensively processes the spoke control signal coming from the spoke section control unit and the mapping RGB signal coming from the color gamut mapping operation unit to convert to an output RGB signal, and the output unit outputs the output RGB signal.

The operation occurring in the spoke section control unit and the color signal processing unit will be described in detail with respect to the processing for Rm, for each level section.

First, when Arp <Rm ≤Arp + Asr, that is, when one spoke section is used, and when Gm≥Bm, the spoke section between RGs is used, and then Ro = Rm-Asr, Go = Gm-Asg, Bo = The output is converted into Bm value. That is, the spoke section determines which spoke section is used according to the signal level, and then sends a control signal to the color signal processor. When the color signal processing unit receives such a signal, the color signal processing unit outputs the output RGB signal after performing a process of reducing the light amount of the spoke used for Rm, Gm, and Bm.

On the other hand, if Bm> Gm, after using the spoke interval between B-R, it will output as Ro = Rm-Asr, Go = Gm, and Bo = Bm-Asb signal. In the above formula, Asr, Asg, Asb means the amount of light in the R, G, B spoke section, respectively.

Next, in the case of Rm> Arp + Asr section, that is, when using two spoke sections, after using the spoke sections between RG and BR, Ro = Rm-2Asr, Go = Gm-Asg, and Bo = Bm- It is output as an Asb signal. In other words, two spoke sections are used for Rm to reduce the light quantity of two spoke sections, and one spoke section is used for Gm and Bm. Because it is maintained.

Next, if Rm> Arp + Asr, Gm> Agp + Asg, and Rm> Arp + Asr, and Bm> Abp + Asb, i.e., a signal at a level where all spokes between RGB regions should be used, RG After using the spokes between the regions, the GB regions, and the BR regions, the signals are output as Ro = Rm-2Asr, Go = Gm-2Asg, and Bo = Bm-2Asb. Since all three spoke sections are used, the original Hue is maintained only when the amount of light of the two spoke sections is subtracted from each color signal. In the case of signal levels other than the above section, since the spoke section is not used, the mapping RGB signal is output as it is. Gm and Bm are converted in the same manner.

The output RGB signal converted in this manner is input to the reflective display device to reflect the image on the screen.

Referring to the method of controlling the color wheel spokes in the reflective image display system using the color wheel according to the present invention, the color gamut mapping calculator performs a step of outputting a mapping RGB signal by mapping at a constant compression ratio according to the level of the input RGB signal. . Since the description of the step has been described above, it will be omitted.

Next, the spoke section controller performs a step of determining to use a specific spoke section according to the level of the mapped RGB signal. Although the above-described steps have been described above, to sum up again, when Arp <Rm ≤ Arp + Asr, when the Gm ≥ Bm, the spoke interval between RGs is used, and when Bm> Gm, BR The inter-spoke section is used, and when Rm> Arp + Asr, the spoke section between RG and BR is used. On the other hand, when Rm> Arp + Asr, Gm> Agp + Asg, and Rm> Arp + Asr and Bm> Abp + Asb, it is decided to use all spokes between R-G regions, between G-B regions, and between B-R regions.

In the case of using the specific spoke section determined by the spoke section controller, the color signal processing unit outputs an output RGB signal subtracted from the spoke signal corresponding to the mapped signal level. In this case, when the spoke section controller determines that the signal section does not need to use the spoke section, since the mapping RGB signal becomes the output RGB signal as it is, the color signal processor does not need to perform a separate conversion process. The formula for the output RGB signal subtracted from the spoke signal used has been described above, but the results are summarized as follows.

(1) When Arp <Rm ≤ Arp + Asr:

If Gm≥Bm (using spoke interval between R-G), Ro = Rm-Asr, Go = Gm-Asg, Bo = Bm,

If Bm> Gm (using spoke interval between B-R), then Ro = Rm-Asr, Go = Gm, Bo = Bm-Asb,

(2) If Rm> Arp + Asr (use spoke section between R-G and B-R):

Ro = Rm-2Asr, Go = Gm-Asg, Bo = Bm-Asb,

(3) When Rm> Arp + Asr and Gm> Agp + Asg (using spokes between R-G region, G-B region and B-R region):

Ro = Rm-2Asr, Go = Gm-2Asg, Bo = Bm-2Asb,

(4) When Rm> Arp + Asr and Bm> Abp + Asb (using spokes between R-G, G-B and B-R regions):

Ro = Rm-2Asr, Go = Gm-2Asg, Bo = Bm-2Asb

The output RGB signal converted by the above equation is finally reflected on the screen by the reflective display element of the output unit.

On the other hand, Figure 5 is a graph showing how the brightness of the output RGB signal is changed compared to the conventional method, when mapped using the spoke period of the color wheel according to the present invention. In the figure, straight line 501 represents a luminance graph according to the conventional scheme, and straight line 502 represents a luminance graph represented by the apparatus and method according to the present invention. In the figure, it can be seen that the luminance of the output signal is improved and linearly increased as compared with the conventional method.

On the other hand, Figure 6 is a graph showing the expansion of the RGB color gamut expressed in the case of using the spoke section compared to the conventional method does not use the spoke section. In FIG. 6, points in a cube denoted by 901 are color signals of a level that can be expressed when the spoke section is not used, and points denoted by 902 show color signals of a level that can be expressed when the spoke section is used. Dots outside the 901 show that the color gamut is expanded according to the present invention.

The foregoing detailed description of the invention has been presented for purposes of illustration and description, and is not intended to limit the invention thereto. In view of the above description, those skilled in the art can make improvements and modifications without departing from the spirit and scope of the present invention.

According to the present invention, in the image display apparatus using the color wheel, unlike the prior art, it is possible to use the spoke section of the color wheel, so that the color gamut wider by 2Asr, 2Asg, 2Asb for Ri, Gi, and Bi, respectively. I can express it. Therefore, the gamut and luminance of the output image are increased compared to the existing invention. In addition, color mapping may be achieved by performing linear processing by mapping at a constant compression ratio during color gamut mapping. On the other hand, in the case of using the spoke section, the process of reducing the amount of light used in the spoke section is performed to keep the overall saturation constant.

Claims (5)

In the video display device using a color wheel, A color gamut mapping calculator configured to perform color gamut mapping on the input RGB signal; Spoke section control unit for determining whether to use the spoke section according to the level of the RGB signal mapped by the color gamut mapping operation unit; And And a color signal processor that reduces the amount of light equal to the spoke period added according to the level of the mapped RGB signal after using the corresponding color wheel spoke period when it is determined that the spoke period controller uses the spoke period and a control signal is input. Color wheel spoke control device, characterized in that. The method of claim 1, The color gamut mapping operation unit, A color wheel spoke control device for mapping an input RGB signal to all filter regions of R, G, and B, respectively, by a predetermined compression ratio. In the image display apparatus using a color wheel, (a) performing color gamut mapping by calculating a predetermined compression ratio with respect to the input RGB signal; (b) determining whether to use a specific spoke section according to the level of the mapped RGB signal; and (c) if it is determined that a specific spoke section is used, calculating the output RGB signal by subtracting the amount of light of the spoke section from the mapped signal level after using the corresponding spoke section; How to control the spokes. The method of claim 3, In step (c), among the mapped RGB signals, When one signal has a level using one spoke section, the spoke section between the regions is used for a signal having a higher level among other signals. If one signal is at a level that uses both spoke sections, then both spoke sections between the two other signal sections are used. When one signal and the other signal is the level using two spoke sections, respectively, it is determined that the spoke section between the R-G region, between the G-B region and between the B-R region to use all of the color wheel spoke control method. The method of claim 3, In the step (c) the output RGB signal, If you don't use spoke segments, Ro = Rm, Go = Gm, Bo = Bm, In case of using the spoke section between R-G regions, Ro = Rm-Asr, Go = Gm-Asg, Bo = Bm, In case of using the spoke section between B-R regions, Ro = Rm-Asr, Go = Gm, Bo = Bm-Asb, When spokes between R-G regions and spokes between B-R regions are used simultaneously, Ro = Rm-2Asr, Go = Gm-Asg, Bo = Bm-Asb, In case of using the spoke section between RG region, GB region and BR region, Ro = Rm-2Asr, Go = Gm-2Asg, Bo = Bm-2Asb, and Ro, Go, and Bo are respectively outputted. RGB signal, Asr, Asg, Asb means the amount of spoke light of R, G, B respectively color wheel spoke control method.