JPH02125590A - Color video reproducing method - Google Patents

Abstract

PURPOSE:To easily reproduce a pattern with high picture quality by reproducing a lightness signal requiring high resolution with a 1st luminous quantity controller with high resolution and reproducing a signal with a sufficient color at a comparatively low resolution with a 2nd luminous quantity controller and synthesizing the results. CONSTITUTION:The light from a white color light source 3 is observed via a diffusion member 4 through both the 1st and 2nd luminous quantity controllers 1, 2 whose area are split in a dot matrix. When 5 the 2nd luminous quantity controller 2 controls three primary colors RGB independently. The 2nd luminous quantity controller 2 is placed at the light source side and the 1st luminous quantity controller 1 is placed at the observer side respectively. Thus, the transmissivities TR, TG, TB of the colors RGB are calculated by arithmetic circuits 11,12,13 to control color information. Moreover, lightness information J is controlled by an arithmetic circuit 14. The results of the circuits 11-14 are synthesized to reproduce a color video image with high resolution.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to a display device that uses a light source and a light amount control device like a liquid crystal television. ! The present invention relates to a method for reproducing video images, and particularly to a method for reproducing color video images.

[Prior art] As a playback device for a koji, consisting of a light source and a light amount control device,
Color LCD display (hereinafter referred to as "LCD display")
Full-color LCD televisions using CDs (called CDs) are mainly used in small portable televisions because they can be thinner than those using CRTs and do not require high voltage.

The color LCD used in these devices consists of pixels arranged in a matrix, and each pixel reproduces images by reproducing the color and brightness corresponding to its position.The zero-color reproduction method is limited to each of the three primary colors. There are two methods: one is based on subtractive color mixing, in which three layers of liquid crystals are stacked together, and the other is spatial mixing, in which pixels of each color of RGB are formed using micro color filters on two LCDs.

However, most color LCD TVs currently in practical use have small screen sizes of 2 to 4 inches.
For screen sizes larger than that, practical application has been delayed due to technological advances.

[Problem to be solved by the invention] In order to obtain a large screen size with a liquid crystal display, it is necessary to increase the number of pixels so that the roughness of the screen is not noticeable, but in general, the larger the number of pixels, the more difficult it is to use a liquid crystal shutter. In addition, when time-division driving is used, the duty ratio becomes small, making it difficult to suppress the decrease in contrast I and last.

This tendency is even greater in color LCD displays. For example, in subtractive color mixing using a GH type LCD, time-division driving is difficult if the duty ratio is small, and an active matrix with a semiconductor switch for each pixel is used. However, it is not easy to create an active matrix with a large area and many pixels, and in the case of spatial mixing using currently mainstream TN or STN type liquid crystals, - RGB on one LCD
Filters and electrodes for each color must be formed, which requires more pixels than a simple black shutter, resulting in poor yield and increased difficulty in driving.

Therefore, the present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a color video reproduction method that can relatively easily achieve high image quality in which roughness is not noticeable even on a large screen size. shall be.

Another object of the present invention is to provide a color video reproduction method 3 that can increase brightness information in response to a relatively large screen.

Another object of the present invention is to provide a color video reproduction method that can maximize the display capability of a display device and obtain brightness information more efficiently.

[Means for Solving the Problems] That is, according to one aspect of the present invention, a first light amount control device is divided into regions in a dot matrix shape, and a first light amount control device is divided into regions in a dot matrix shape and can control each of the three primary colors of RGB independently. , and a second light amount control device having a larger pixel pitch than the first light amount control device, and a white light source are installed so that the light from the light source passes through both light amount control devices and is observed, The first light amount control device reproduces the brightness information of the video signal representing the image to be reproduced, and the second light amount control device reproduces the hue information of the video signal, and these are superimposed to reproduce a color image. A color video reproduction method is provided.

Further, according to the second invention, the first light amount control device is divided into regions in a dot matrix shape, and the first light amount control device is divided into regions in a dot matrix shape and can control each of the three primary colors of RGB independently; A second light amount control device having a larger pixel pitch than the control device and a white light source are installed so that the light from the light source passes through both light amount control devices and is observed, and the brightness including high spatial frequency components is adjusted. When reproducing a color video signal consisting of a signal and a chromaticity signal with a spatial frequency lower than the brightness signal, the frequency is lower than the upper limit frequency that can be reproduced without deterioration of contrast with the resolution of the second light amount control device,
and determine the frequency fc that is higher than the upper limit frequency of the chromaticity signal, R
The second light amount control device reproduces the intensity signal of each color of GB by removing the component of fc or higher, and adds the intensity signal of each color of RGB to a brightness signal K, which is f c L of this K.
: Signal obtained by dividing the frequency component below J by 1 = K, /
A color video reproducing method is proposed in which KL is reproduced by the first light amount control device and these are superimposed to reproduce a color video.

Furthermore, according to a third invention, the first light amount control device is divided into regions in a dot matrix shape, and the first light amount control device is divided into regions in a dot matrix shape and can control each of the three primary colors of RGB independently, and A second light amount control device having a larger pixel pitch than the control device and a white light source are installed so that the light from the light source passes through both light amount control devices and is observed, and high spatial frequency components are detected. When reproducing a color image consisting of a brightness signal including a brightness signal and a chromaticity signal having a spatial frequency lower than the brightness signal, the frequency is below the upper limit frequency that can be reproduced without deterioration of contrast with the resolution of the second light amount control device,
and determines a frequency fc that is higher than the upper limit frequency of the chromaticity signal, and reproduces the RGB color reproduction signals R', G of the second light amount control device.
A color video reproduction method is provided in which the reproduction signal J' of the first light quantity control device and the reproduction signal J' of the first light amount control device satisfy the following conditions.

(a) R', G', and B' are signals consisting of frequency components below fc, and satisfy or approximately satisfy R'≧R, G'≧G, and B'≧B.

(b) J'= (R+G+B)/ (R'+G' +
B') However, R, G, and B are the original signals of the three primary colors.

[Function] The color video reproduction method according to the first invention reproduces a brightness signal that requires high resolution using the first light amount WI control device that has high resolution, while also reproducing a signal with sufficient hue even at a relatively low resolution. A second light amount control device reproduces the images and combines them to create a color image.

In the color video reproduction method according to the second invention, the second light amount control device reproduces the chromaticity signal and the low resolution brightness signal, and the first light amount control device reproduces the high resolution brightness signal. , By combining these, color images 1? ! ,
8. The color video reproduction method according to the third invention is as follows:
By making the reproduction signals of each RGB color of the second light quantity M door device and the reproduction signal of the first light quantity control device satisfy predetermined conditions (a) and (b), the light in the first light quantity control device is Brightness information can be efficiently obtained by minimizing loss and maximizing the capabilities of the display device.

[Embodiment] A color video reproduction method according to the first invention includes separately providing a first light amount control device for reproducing brightness information and a second light amount control device for reproducing color tone information. This allows high-resolution color reproduction to be performed relatively easily.

Human perception of image resolution is sensitive to brightness, but relatively dull to hue.If we focus on this, we can see that the resolution required for the second light control device is not very high. Recognize. Regarding current TV broadcasting and home VTRs in Japan, the brightness signal horizontal group 1 pitch is 200 to 500 TV lines.
The chroma signal is actually 40 TV lines. From this, the second
It can be seen that a matrix size of about 80\112, which is twice the resolution of 1 degree of the chroma signal, is sufficient for the light amount control device.

On the other hand, the first light amount control device that reproduces brightness information is
Since it requires a high resolution (?, power), a device with a larger number of pixels than the second light amount control device is used, but it is relatively easy to manufacture and drive because there is no need to reproduce the hue.

That is, the meaning of the present invention is that in a color display constituted by a light source and a light amount control device,
The video signal is divided into a brightness signal and a signal representing hue, and the brightness signal that requires high resolution is reproduced by the first light amount control device with high resolution, while the signal with sufficient hue is reproduced even with relatively low resolution. The object of the present invention is to relatively easily achieve high image quality that does not suffer from roughness even on a large screen size by reproducing images using a second light amount control device with a high resolution and combining them to create a color image.

Therefore, in the first invention, it is necessary that the resolution of the first light amount control device is higher than that of the second light amount control device. The pixel pitch of the m device is one of that of the second light amount control device.
It is desirable that the ratio be less than 1/2. However, if the difference in pixel pitch between the two light quantity control devices becomes too large, color bleeding will become noticeable, so it is not preferable for this ratio to become smaller than 1/10.

The color video reproduction method according to the first invention will be explained in more detail with reference to FIGS. 1 and 2. In FIG. 1, light from a white light source 3 is transmitted through a diffusion member 4 provided to improve uniformity to a first light amount control device 1 and a second light amount control device which are divided into regions in a dot matrix shape. The light passes through both light amount control devices of device 2 and is observed.

The second light amount control device 2 is capable of independently controlling each of the three primary colors of RGB, and has a larger pixel pitch than the first light amount control, and the second light amount control device 2 is arranged on the light source side. , the first light amount control device 1 is Ii!
installed on each side.

The first light amount control device 1 is configured to reproduce brightness information, and the light amount control device 2 is configured to reproduce color tone information.

At this time, the first light amount i1i+11311 device 1 is controlled by brightness information. Here, brightness represents the brightness of each pixel, and if light is divided into the three primary color components of RGB and the brightness of each color is R, G, and B, each has a positive coefficient as shown in formula It is expressed as a linear combination that is multiplied by .

J=CR+CG+CBB...■G where C, Ca, Ca: Positive real number J: Brightness information,
In the first light amount control device 1, the transmittance is controlled so as to be proportional to J.Equation (2) shows that each coefficient 't&C, C, and CB is the intensity ratio shown in each wavelength range by the white light source 3G, and the second light amount. An appropriate value may be determined based on the characteristics of the II fi device 2.

On the other hand, the second light amount control device! 2 is controlled by hue information, and this is controlled so that the transmittance is shown in formula 000.

T = C-R/(J-LR)...■T T =C-G/(J-LG)...■T T =C-B/(J-LB)...■8■ However , 000, when the right side is larger than the maximum transmittance, the left side = maximum transmittance.

T, T, T: Transmittance in each G8 pixel of each RGB color L, L, L: Light intensity shown in the black RGB each wave GB long range of the white light source CI: Positive real number As a result, the amount of transmitted light of each component is proportional to R, G, and B, respectively.
Color images are reproduced correctly. Note that the larger the CI, the higher the efficiency and the brighter the screen will be. However, if any of the right sides of the 000 formula exceed the maximum transmittance, the image reproducibility will deteriorate, so these values are the maximum transmittance. Adjustments must be made so that the rate is not exceeded too often.

Specifically, as shown in FIG. 2, the transmittances T, T, and T8 at each pixel of each RGB color are calculated by the calculation circuits 11, 12, and 13, and the hue information is controlled based on this. , and the brightness information J is controlled by the arithmetic circuit 14.

Next, an apparatus configuration similar to that shown in FIG. 1 described above was used.

We will explain how to play color video in different ways.

That is, in the color video reproducing method according to the second invention, the second light amount control device 2 used for reproducing hue information in the first invention is actually capable of reproducing brightness information. to reproduce the low frequency component of the video signal, and the first light amount control device l to reproduce the high frequency component of the video signal,
The purpose of the second invention is to complete a color image by combining these images.

This will be further explained in detail using Fig. 3 (21, 4).

Here, reproduction of an NTSC video signal will be explained as an example. In this case, the video signal consists of a brightness signal Y and chromaticity signals Q and I, each using R, G, and B.
It is expressed as follows.

Y = 0.30R+ 0.59G + (1,1+B
...■Q = 0.21R-0,52G + 0.3
1B...■1 = 0. (ioR-0,28G-
0,32B... ■Also 2 Normal TV broadcasting and home VT
In R, as shown in Figure 4, the Y signal has a band of several MHz, but the Q signal and ■ signal have a band of 0.5 to 1.5 MHz.
It only has a bandwidth of From the 000 formula, R, G, and B are ■■[
It is calculated as follows:

R2O,9GI + 0. f33Q + Y...■G
= -0,28I -0,64Q + Y...■B
=-1, NI +1.72Q+Y...0 R, G above
= 8 has a band of several MHz, and only frequency components below the cutoff frequency fc are extracted through a low-pass filter (hereinafter referred to as P and F) and used as a reproduction signal for the second light amount control device 2.

Here, fc must be lower than the upper limit frequency that can be reproduced without deterioration of contrast at the resolution of the second light control device 2, and must be higher than the upper limit frequency of the chromaticity signal.

Therefore, the transmittance of the three primary colors of the second light quantity device 2 is expressed by the formula OoO.

T = C-R゛/LR...OT From the frequency components of G and B below fc, K is calculated using the 0 formula from R, G, and B obtained using the 000 formula,
This is then passed through P and F to the frequency component K below fc.
is determined, and J' determined from J' = /K[ is used as the reproduction signal of the second light amount control device 2. J' is a signal containing a DC component and a high-resolution brightness signal.

K=R+G+B...O Specifically, it is implemented in an electronic circuit according to the block diagram of FIG. In other words, a brightness signal Y that includes a high spatial frequency component and a chromaticity signal Q that has a spatial frequency lower than the brightness signal.
,■ When reproducing a color video signal consisting of
The intensity signals of each color of R, G, and B are obtained by the matrix circuit 21, and the second light amount control device 2 is used to cut a frequency below the upper limit frequency that can be reproduced without deterioration of contrast and above the upper limit frequency of the chromaticity signal with the degree of decoupling of the second light amount control device 2. A low-pass filter 22 having an off-frequency fc removes components above fc from the intensity signals of each RGB color, and the second light amount control device 2 reproduces the intensity signals, and an arithmetic circuit 23 adds the intensity signals of each RGB color. A signal J'=K/KL is obtained by dividing the combined brightness signal K by Kt, in which only the frequency components below fc of this K are extracted by a low-pass filter 24, and this is used in the first light amount control. Make it playback on device 1.

In this way, the chromaticity signal and the low-resolution brightness signal are reproduced by the second light amount control device 2, and the high-resolution brightness signal is reproduced by the first
is reproduced by the light amount control device 1.

By combining these, a complete image is created.

Next, let us consider the efficiency of the color video reproduction method according to the first and second inventions.

Second light control device! Assuming that the display device consisting of the light source 2 and the white light source 3 can display each color of RGB up to a brightness of 1, the white color which is the sum of the three primary colors can be displayed with a brightness of 3. In my opinion, it is the second light amount! II 1311 Since it is fundamentally undesirable for the brightness to change depending on the device 2 (because only the hue information is reproduced in the second light amount control device 2), RGB
As with each of the colors, the white color can only be reproduced to a brightness of substantially 1. In this sense, the first invention can only produce images with a brightness of about 1/3 of the display capacity of the device.

The efficiency of the second invention will be explained by referring to No. 5121. 5th [brightness signal represented by the solid line in 2I(A)) (]
When reproduced, K1 appears as a dotted line, which is reproduced by the second light amount control device 2 through the three primary color signals. On the other hand, J'=/KL becomes as shown in FIG. 3B, and is reproduced by the first light amount control device 1. Assuming that the control range of the transmittance of the first light amount control device l is 0-Tmax, from the waveform in FIG. It can be seen that it is. Since the brightness of the reproduced image is the product of J' and KL, the brightness of the second light amount control device 2 (T of the brightness of the bond)
In this sense, it can be seen that in the second invention, an image with a brightness of approximately 1,...'2 of the display capacity of the display device can be obtained.

As shown in item 2, the images obtained by the first and second inventions each have a device capacity of 1. '3.1.・'2. For this reason, the light source 3 needs to be bright, but as the screen size increases, a larger amount of light is required. It becomes difficult to ensure brightness.

In order to solve this problem, as in the first and second inventions, an efficient color video reproduction method using the apparatus shown in FIG. 1 and making full use of the display capacity of this apparatus will be explained as a third invention. .

The principle of the third invention will be explained using FIG.
In the second invention, KL was determined as shown in FIG. 5(A), whereas in the third invention, as shown in FIG. 61(A), f
A signal with a waveform that envelops a high-resolution component of c or higher is used. As a result, J'=K, /K becomes as shown in (B), and the transmittance of the first light amount control device 1 is T on average.
max/2 or more.

When ring No. 12 Kl) does not have a frequency component higher than Cfc, it becomes equal to Tmax. As a result, the tl ratio in the first light amount control device 1 is minimized, and the device shown in FIG. 1 can be used to its maximum potential.

In other words, the RG of the second light amount control device 2
When the reproduction signals of the B colors are R', G', and the reproduction signal of the B light quantity control device is J', it can be said that these satisfy the following conditions.

(a>R', G', B' is a signal consisting of frequency components below fc and satisfies or approximately satisfies R'≧R, G'≧G, B'≧B.

(b), J' = (R+G+B)/ (R'10G'
+B') However, R, G, and B are the original signals of the three primary colors RGB.

Here, K = R, + G + 8, and since the chromaticity signal does not have a frequency component higher than fc, K = R'
The condition that K[ is a signal with a waveform that envelops K and that holds G+B′ is the above condition (a), but since this alone is insufficient to explain it, we actually use the method to find This will be explained below.

First, FIG. 7 shows a first embodiment different from the third invention.

The 9 R, G, and B signals explained based on FIG. 8 are 1/1 according to the block diagram of FIG.
The signal passes through the peak hold circuit 31 having a relaxation time of fc, passes through the acid cutoff frequency fc, and passes through P, F, 32 to become a signal that approximately satisfies the condition (a). This situation is shown in FIG. 8(A). The original signal shown as a solid line becomes a dotted line due to the peak hold circuit 31, and L, P, F
, 32 and becomes a one-point M line. Although this cannot be called an envelope in the strict sense, even if it is used as R', G', and B', it has a sufficient efficiency improvement effect compared to the second invention, and under the above condition (a). This is what is meant by approximately satisfying. More preferably, in order to approach a more perfect envelope, find the most efficient conditions by correcting the signal indicated by the dashed dotted line in Fig. 8 by a coefficient greater than 1 using the calculation circuit i\833 in Fig. 7. However, if this coefficient becomes larger than 2, the efficiency of the second invention will be lower than that of the second invention, so the effect of the invention will be lost and it is not preferable. , J.
This is an arithmetic circuit that obtains ′.

Next, a second embodiment according to the third invention will be described based on FIG. 9. The R, G, and B signals are passed through a bandpass filter (8
, P, F, ) 36, it is divided into a frequency component above fc and a frequency component below fc, and the component above fC is A.
After AM detection by the M detection circuit 37, the correction circuit 38
is corrected by multiplying by a coefficient larger than 1, and the adder circuit 3
9 and are added together again to form R', G', and B'.

The amount of correction depends on the method of A P, 1 detection, but half wave rectification +
For detection of L, P, F, ×π, double wave rectification + L, P,
For detection of F, it is preferable to apply a coefficient of xπ/2, and for detection using a rectifier circuit and a peak hold circuit using a diode D, a capacitor C1, and a resistor R1 as shown in FIG.

In this way, R', G'B' satisfying the above-mentioned condition 1+(a) are obtained by each embodiment according to 712I and FIG.
is obtained, and the third invention is implemented.

Next, important points in carrying out the first to third inventions will be explained below.

The white light source 3 used in the first to third inventions preferably contains components of each color approximately equally.

So-called colored light, which contains a large amount of specific components, is not preferred.

Further, in FIG. 1, it is preferable that the distance between the first light amount control device 1 and the second light amount control device 2 be as small as possible.
It is most preferable to bring them into close contact.

Furthermore, as the first light amount control device 1 and the second light amount control device 2 used in the first to third inventions, it is currently most practical to use liquid crystal shutters; The method of the second invention is more general, and uses another light amount control means as the first light amount control means for either or both of the first light amount control device 1 and the second light amount control device 2. Other light amount control means that may be used include:
For example, insulating materials such as polythiophine or polypyrrole (using conductor-conductor transition) and electrochromic materials may be considered.

In the first to third inventions, the positional relationship between the first light amount control device 1 and the second light amount control device 2 is such that the second light amount control device 2 is on the light source side and the first light amount control device 1 is on the observation side. It is preferable that the light from the light source first pass through the second light amount control device 2, then pass through the first light amount control device 1, and be observed. The high resolution video reproduced by the device 1 can be observed as is.

In the opposite case, when the video reproduced by the first light amount control device 1 is viewed through the second light amount control device 2, the second light amount control device 1
There is a possibility that the light may be distorted or partially blocked by the light amount control device 2, which is not preferable.

Note that when using a liquid crystal shutter that uses rotation of the polarization plane together with the first light amount control device 1 and the second light amount control device 2, it is preferable that the polarization planes of the two steel photons on the opposing surfaces are the same; Therefore, one light plate can serve as both.

[Effects of the Invention] As explained above, according to the color video reproduction method different from the first invention, the first light amount control device has a high degree of resolution, and the second light amount control device has a low degree of resolution and can control hues in three groups. By combining this light amount control device, it is possible to easily reproduce high-resolution color images.

Further, according to the color video bond recycling method according to the second invention, the second light amount control device reproduces the hue information and the low resolution brightness information, and the first light amount control device reproduces the high resolution brightness information. By reproducing information and composing them to reproduce a color image, brightness information can be further enhanced.

Furthermore, according to the color video reproduction method according to the third invention, by making the reproduction signals of the first and second light quantity control devices satisfy a predetermined condition, the transmission in the first light quantity control device is reduced. The performance of the display device can be maximized by minimizing the loss in brightness, and necessary brightness information can be efficiently obtained in response to an increase in screen size.

Therefore, according to the color video playback method according to the first to third inventions, it is possible to relatively easily achieve high image quality in which roughness is not noticeable even on a large screen size, and it is possible to achieve high image quality with less noticeable roughness even on a large screen size, and it is also possible to achieve high image quality without noticeable roughness even on a large screen size. It can satisfy image quality, small size, light weight and low price at the same time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of an apparatus for implementing the first to third inventions, FIG. 2 is a block diagram for signal processing for implementing the first invention, and FIG. FIG. 2 is a block diagram of signal processing implementing the invention. FIG. 4 is an explanatory diagram illustrating the synthesis of reproduction signals in the color video reproduction method according to the second invention, FIG. 5 is an explanatory diagram illustrating the efficiency (video brightness) according to the method of the second invention, FIG. 6 is a characteristic diagram showing the principle of the third invention for improving efficiency, FIG. 7 is a block diagram of signal processing according to the first embodiment of the third invention, and FIG. 8 is an explanation of its operating principle. FIG. 9 is a block diagram of signal processing according to the second embodiment of the third invention. 1...First light amount control device. 2... Second light amount control device, 3... White light source. Inventor Noriji Oishi

Claims (3)

[Claims] (1) A first light amount control device divided into regions in a dot matrix shape, and an RG light amount control device divided into regions in a dot matrix shape;
A second light amount control device that can independently control each of the three primary colors of B and has a larger pixel pitch than the first light amount control device, and a white light source, the light from the light source passing through both light amount control devices and observing. the first light amount control device reproduces brightness information of a video signal representing an image to be reproduced, and the second light amount control device reproduces color tone information of the video signal, respectively; A color video playback method that plays back color video by overlapping these images. (2) A first light amount control device divided into regions in a dot matrix shape;
A second light amount control device that can independently control each of the three primary colors of B and has a larger pixel pitch than the first light amount control device, and a white light source, the light from the light source passing through both light amount control devices and observing. When reproducing a color video signal consisting of a brightness signal containing a high spatial frequency component and a chromaticity signal having a spatial frequency lower than the brightness signal, the resolution of the second light amount control device is A frequency fc that is below the upper limit frequency that can be reproduced without deterioration of contrast and above the upper limit frequency of the chromaticity signal is determined, and the intensity signal of each RGB color excluding components above fc is reproduced by the second light amount control device. Then, the lightness signal K obtained by adding up the intensity signals of each RGB color is divided by the frequency component K_L below fc of this K, and the signal = K/K_L is reproduced by the first light amount control device, and these are A color video playback method that plays back color videos by overlapping them. (3) A first light amount control device divided into regions in a dot matrix shape;
A second light amount control device that can independently control each of the three primary colors of B and has a larger pixel pitch than the first light amount control device, and a white light source, the light from the light source passing through both light amount control devices and observing. When reproducing a color image consisting of a brightness signal containing a high spatial frequency component and a chromaticity signal having a spatial frequency lower than the brightness signal, the resolution of the second light amount control device determines the contrast. A frequency fc that is below the upper limit frequency that can be reproduced without deterioration of the chromaticity signal and above the upper limit frequency of the chromaticity signal is determined, and the R of the second light amount control device is determined.
A color video reproduction method in which the reproduction signals R'G', B' of each color of GB and the reproduction signal J' of the first light amount control device satisfy the following conditions. (a) R', G', and B' are signals consisting of frequency components below fc, and satisfy or approximately satisfy R'≧R, G'≧G, and B'≧B. (b) J'=(R+G+B)/(R'+G'+B') However, R, G, and B are original signals of the three primary colors.