JP2001075547A - Image signal correcting device and image signal separation method and calculator system using them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve display quality of a video without affecting a computer image even when the video and the computer image coexist in the same picture. SOLUTION: An image signal correcting device is provided with a video discrimination part 9 discriminating an image digital signal outputted from a display control part 4 between a computer image signal and a video signal and a video correction part 10 performing correction processing for signal separated as the video signal between the display control part 4 incorporated in a computer and a display part 5 of a CRT and an LCD, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, a computer display device, and the like, which separates a video signal taken into a computer system (computer system) from a normal computer image signal before display, and performs a correction process. The present invention relates to an image signal correction device, an image signal separation method, and a computer system using the same that improve display quality of a video signal without affecting a computer image signal.

[0002]

2. Description of the Related Art Heretofore, there has been known a liquid crystal display device, a computer display device, or the like, in which an image and a normal computer image can be superimposed and displayed on the same screen. For example, a video such as a television broadcast or a VTR input from a video input terminal such as a TV antenna or a video input terminal and a computer image such as a computer menu, an icon, and text data are displayed on the same screen.

As a technique for displaying this video beautifully, there is a technology that can switch between correction processes of an input video signal and an image signal including a computer image signal. For example, Japanese Patent Laying-Open No. 5-188352 discloses a display device provided with a gamma correction circuit in order to perform optimum display for each of a video signal and a normal computer image signal. Japanese Patent Application Laid-Open No. 6-208339 discloses a color correction circuit for canceling gamma correction and improving color reproducibility adapted to a liquid crystal display device (LCD) in order to improve the display quality of the liquid crystal display device (LCD). Is disclosed.

[0004]

However, the prior art disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-188352 switches a switch depending on whether or not a video signal is present.
The correction processing is effective in the case of a video signal. Further, in the prior art disclosed in Japanese Patent Laid-Open No. 6-208339, a correction circuit is applied to only a video signal by a correction circuit before the video signal and the computer image signal are superimposed. Therefore, in these prior arts, after storing a video signal as digital data in an external storage device of a computer by using a video capturing device such as a video capture device, for example, all are processed as computer image signals. Correction processing is not effective. To prevent this,
It is conceivable that the data after the above-described correction processing is taken into an external storage device. In this case, however, the display characteristics are changed when the data is displayed on another display device. Absent.

The present invention has been made to solve such a problem of the prior art, and performs a process of discriminating an image digital signal including a video signal and a computer image signal before displaying both signals before displaying the signal. Thus, the display quality of the video signal can be improved without affecting the computer image signal. Further, even when the video signal is taken into an external storage device, an effective image signal correction device and an image signal separation device can be provided. It is an object of the present invention to provide methods and computer systems using them.

[0006]

According to the present invention, there is provided an image signal correcting apparatus, comprising: a display capable of displaying a video signal and a computer image signal on the same screen; and a display for supplying an image digital signal including both signals to the display. Having a form that can be disposed between the control unit, a separation unit that separates the image digital signal output from the display control unit into a computer image signal and a video signal, and among the computer image signal and the video signal,
A correction unit for correcting a signal separated as a video signal, whereby the object is achieved.

An image signal separating method according to the present invention is an image signal for separating an image digital signal including a video signal and a computer image signal, which are supplied from a display control unit to a display unit capable of displaying both signals on the same screen. A separation method,
Depending on whether or not the luminance value of the image digital signal corresponds to a plurality of predetermined luminance values of a number smaller than the number of colors supported by the display control unit, the image digital signal is converted to the video signal and the computer. By judging which of the image signals, the two signals are separated, thereby achieving the above object.

[0008] As the plurality of predetermined brightness values,
A multiple of 16 and 255 may be used.

In a pixel and a pixel adjacent thereto,
It may also be considered whether or not the difference between the luminance values of the image digital signal exceeds a predetermined threshold.

A computer system according to the present invention provides a display control unit for supplying an image digital signal including a video signal and a computer image signal to a display unit, an external storage device for storing data, and temporarily storing data. An image signal correction device according to the present invention or an image signal separating method according to the present invention, comprising: a memory, a CPU that performs arithmetic processing, a display unit that displays an image, and an input device that performs input for operation by a user. An image signal correction device that separates an image digital signal into a computer image signal and a video signal by using the display unit and the video signal, and corrects the computer image signal and the video signal that are separated as a video signal. It is arranged between the display control unit and the display control unit, thereby achieving the above object.

[0011] The correction section may perform gamma correction processing in a liquid crystal display device on a signal separated as a video signal.

The correction section may perform a sharpening process on a signal separated as a video signal.

The operation of the present invention will be described below.

In the present invention, the image digital signal output from the display control unit is separated into a computer image signal and a video signal before being input to the display unit, and the separated computer image signal and video signal are separated. Among them, the signal separated as a video signal is corrected. Therefore, even after the video signal is fetched into the external storage device, the video signal is subjected to correction such as γ correction processing and sharpening processing on the LCD without affecting the computer image signal, thereby improving the display quality. It is possible to

The computer image signal is often composed of a color having a specific luminance value, such as a multiple of 16 or 255. Therefore, as shown in an embodiment described later,
If such a brightness value is defined in advance, it is possible to separate the image digital signal from the video signal by regarding the image digital signal as a computer image signal when the brightness value is satisfied.

By the way, even in the case of a computer image signal, for example, the upper part of the window may be formed by gradation. In this case, since it is not composed of a color having a specific luminance value, it is processed as a video signal.
However, the image may be locally formed of a color having a specific luminance value, and only that part is determined as a computer image signal, resulting in a spotted pattern. Therefore, in order to prevent such a phenomenon, as described in an embodiment described later, in the case of the video signal mode, even if all pixels in a certain range including a certain pixel are configured with a color having a specific luminance value. It is also considered whether or not the difference between the luminance value of the image digital signal between a certain pixel and a pixel adjacent thereto exceeds a predetermined threshold value.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a computer system to which the present invention can be applied. This computer system is a computer system provided with a normal video input means, an antenna 1 for receiving a video radio wave, a tuner unit 2 for converting a signal received by the antenna into a video signal of a desired channel, and a video input terminal 3a. A video capture unit 3 for converting a video signal obtained from the tuner unit 2 or a video signal input from the video input terminal 3a into digital data, a general-purpose display controller (display control unit) for transmitting the captured video signal to the display unit 5 4, a display unit 5 such as an LCD or CRT for displaying video and computer images, a CPU 6 for performing arithmetic processing, a memory 7 for temporarily storing data, and an external storage device 8 for storing video data. It also has an input device (not shown) such as a keyboard and a mouse.

In this computer system, in the case of a signal input from the antenna 1, the flow of the video data for the TV is displayed on the display unit via the antenna 1, the tuner unit 2, the video capturing unit 3 and the display control unit 4. Sent to 5. In this case, the processing proceeds without the intervention of the CPU 6. Also, video data from a recording device such as a VTR is
The data is sent to the display control unit 4 via the video input terminal 3 a and the video capturing unit 3, and is supplied to the display unit 5.

On the other hand, when some software processing is performed on the video data stored in the external storage device 8 using a video capturing device such as a video capture device, the data is called to the memory 7 and the processing is performed by the CPU 6. In addition, it is sent to the display control unit 4 and supplied to the display unit 5.

As described above, the portions of the video data that pass in common for each processing are the display control unit 4 and the display unit 5. Therefore, in the present embodiment, as shown in FIG. 2, an image signal correction device having a video identification unit 9 and a video correction unit 10 is provided between the display control unit 4 and the display unit 5.

This image signal correction device may be connected to a computer or display device having a built-in general-purpose display controller (display control unit) 4 by a cable, or may be connected as a board to the computer and display device by a bus. Is also good. Alternatively, it may be built in a computer main body or a display device as an electronic chip. Furthermore, each of the video identification unit 9 and the video correction unit 10 may be in a board / device form that can be individually connected to the computer body or the display device by a bus / cable, or in a chip form that can be individually built in the computer body or the display device. .

Thus, as described later, even a video signal input from a video input terminal such as a TV antenna or a video input terminal is stored as digital data in an external storage device of a computer by a video capture device or the like. It is possible to perform a correction process separately from a computer image signal such as a computer menu, an icon, and text data even if the video signal is a video signal.

In the image signal correction device, the image identification section 9 has a function of identifying whether the image digital signal is a video signal or a normal computer image signal. Further, the video correction unit 10 corrects only the pixels determined to be video by the video identification unit 9 and outputs the same value to other pixels. Note that a normal computer image indicates, for example, a menu, an icon, text data, and the like.

The processing of the image correction unit 10 includes, for example,
Brightness correction, contour correction and the like can be mentioned. Normally, if the captured video signal is output as it is, the voltage-light conversion characteristics of the display unit 5 are not linear, so that a video having a different color tone or the like from that at the time of shooting is displayed. Therefore, for a normal TV broadcast, a correction process is performed by a gamma correction circuit to make the input light of a camera or the like proportional to the output light of a display. This correction process is generally performed using a γ function as shown in FIG.

Further, contour correction processing or the like is often performed on moving images in order to improve sharpness. It is well known that such a sharpening process is realized by a Laplacian filter represented by g (x) = f (x) + Δ ² f (x). For example, the sharpening process shown in FIG. The pixel value is converted by a filter having coefficients.

By the way, when the entire screen of the display unit 5 is an image, the above-described correction processing may be always performed, so that a general-purpose display control circuit can display a sufficiently high-quality image. However, when the image and the normal computer data are mixed on the screen, if the display state is adjusted to be suitable for the image, the display state of the normal computer data is deteriorated.

In order to prevent this, in the present embodiment, the video discriminating unit 9 discriminates between a normal computer image signal and a video signal with respect to the image digital signal, and the video correcting unit 10 performs a correction process only on the video signal. To do. Hereinafter, the determination processing by the video identification unit 9 will be described with a specific example.

In a computer system, various data such as menus and icons are displayed in a mixed state in addition to video, and the data such as menus and icons are composed of a color having a specific luminance value. There are many things. This was originally due to the fact that the computer system could only handle a small amount of memory, and many of the computer images (text, menus, icons, etc.) The value is composed of colors. Therefore, the luminance value of a specific pixel is individually checked for RGB, and if any of a plurality of predetermined luminance values is satisfied, it can be regarded as a normal computer image.

In computer image signals, colors are represented by the intensity of the colors "red", "green", and "blue".
For example, the combination of red, green, and blue (red brightness level,
When a numerical value is represented by a hexadecimal number as a green luminance level and a blue luminance level, red is (255, 0, 0) and gray is (0xc
0, 0xc0, 0xc0), and pink is (0xff, 0,
0xff), the light blue is (0x80, 0xff, 0xff)
Becomes Therefore, it is possible to determine to some extent whether or not the image is a computer image based on whether or not the image corresponds to a specific luminance value. Note that these luminance values are examples.

However, a moving image (video) or a still image can have an arbitrary luminance value. Therefore, when the luminance values are compared in units of one pixel, the luminance value is specified at a position where the luminance value changes continuously. There is a problem that a portion corresponding to the luminance value is generated and the image and the normal computer image mode are partially switched.

In a computer image, for example, the upper part of the window (where the mouse is operated when the window is moved) or the like has a gradation on the video display, and the luminance value changes smoothly, and is composed of only a specific luminance value. Therefore, it is processed as a video signal. In such a case, as described above, if the image digital signal is identified only by the criterion of whether or not the luminance value at a specific pixel corresponds to a specific luminance value, the luminance value corresponding to a normal computer image is obtained. , The result after the processing becomes worse.

FIG. 8 shows an example in which a part of the video signal is erroneously determined to be a normal computer image, resulting in a sense of incongruity in the processing result. As shown in FIG.
The input signal is periodically determined to be in the normal mode (text area). Then, the brightness correction is performed on the portion determined to be in the moving image mode (video mode) mode, but the brightness correction is not performed for the portion determined to be in the normal mode.
As shown in (b), a stripe pattern occurs.

In order to prevent this, in the present embodiment, two modes, a normal mode (computer image mode) and a video mode, are provided. In the video mode, pixels at a certain interval including the target pixel are set. It is assumed that a change in the brightness value larger than a certain threshold value occurs in a portion corresponding to a specific brightness value and switching from the video mode to the normal mode. Accordingly, a pattern such as a gradation can be identified as an image and a correction process can be performed, so that a stripe pattern as shown in FIG. 8 does not occur.

FIG. 3 shows a processing flow for determining an image digital signal in this embodiment. Here, the image data (pixel row) of each pixel input in time series is (R
₁ , G ₁ , B ₁ ), (R ₂ , G ₂ , B ₂ ),..., (R _i ,
G _i , B _i ),..., (R _N , G _N , B _N ). The buffers P _{1 to} P ₅ store flags (1 if applicable, 0 if not applicable) indicating whether all the RGB luminance values correspond to a specific luminance value. I do. In the present embodiment, the luminance value is a multiple of 16 or 255
Is determined based on whether or not. It is assumed that the buffers E ₁ and E ₂ store the maximum value of the luminance value difference between the pixel of interest and its left and right pixels. Further, a flag indicating whether the mode is the normal mode or the video mode (1 in the normal mode, 1 in the video mode) is stored in the buffer M, and the value of the counter is stored in i. .

First, in step 21 of FIG. 3, M (video mode) is set to 0 and P ₁ and P ₂ are set to 1 as initial settings.
(Corresponding to a specific luminance value), and set 1 to a counter i.

Next, in step 22, the data is entered in time series.
The first pixel (R₁, G₁, B ₁), There is
A specific luminance value (a multiple of 16 or 25 in this embodiment)
It is determined whether or not 5) is satisfied. And applicable
P_ThreeTo 1; if not applicable, P_ThreeTo
Substitute 0. Next, in step 23,
22, the second pixel (R_Two, G_Two, B_Two) For
To a specific luminance value (a multiple of 16 or 255).
Judgment of whether or not to hit, if applicable P_FourTo
Substitute 1 and P if not applicable_FourTo 0.
Next, in step 24, as in step 22,
The (i + 2) th (third at the first) pixel (R_{i + Two}, G_{i + 2}, B
_{i + 2}) For a particular luminance value (a multiple of 16 or
255) is determined, and
If P_FiveTo 1; if not applicable, P_Five0 to
substitute.

Next, in step 25, the luminance value difference between the target pixel and the pixel on the left thereof, that is, R _i -R _i-1 ,
The maximum value of the absolute values of G _i -G _i-1 and B _i -B _i-1,
And stores it in the E _1. Next, in step 26, as in step 25, the brightness value difference between a target pixel and its right adjacent pixel, _{i.e., R i -R i + 1,} G i -G i + 1 and B _i -B
_{i + 1} of the maximum value of the absolute value is stored in E _2.

Next, processing for mode determination is performed. First, in step 27, branch processing is performed depending on whether M (current mode) is 1.

If M is 1 (normal mode), at step 28, one of P ₃ , P ₂ and P ₁ becomes 0
Is calculated, and if all are 1, step 3
Proceed to 1. If any _one of P ₃ , P ₂ and P ₁ is 0, the process proceeds to step 29. In step 29, as in step 28, one of P ₃ , P ₄ and P ₅ becomes 0
Is calculated, and if all are 1, the process proceeds to step 31, and if any of P ₃ , P ₄ and P ₅ is 0, the process proceeds to step 30.

On the other hand, if M is 0 (video mode), at step 32, all of P ₃ , P ₂ and P ₁ are 1, and E ₂ is a certain threshold (Th, for example, 25)
Is calculated. Then, if the condition is satisfied, the process proceeds to step 31; otherwise, the process proceeds to step 33. In step 33, step 32
Similarly, calculate whether P ₃ , P ₄ and P ₅ are all 1 and whether E ₁ exceeds a certain threshold. Then, when the condition is satisfied, the process proceeds to step 31, and when the condition is not satisfied, the process proceeds to step 34.

In steps 30 and 34, 0 (video mode) is substituted for mode M, and in step 31, 1 (normal mode) is substituted for mode M.

Next, in step 35, the values of P _{2 to} P ₅ are sequentially changed to P _{1 to} P ₄ in order to process the next pixel.
And increment the value of i by one.

Next, in step 36, it is calculated whether or not i is equal to or less than N (the rightmost pixel of the row). If i is the rightmost of the row, the processing is terminated. move on. In step 37, it is calculated whether or not i is equal to or smaller than N-2 (the third pixel from the right of the row). Step 3 if it is the rightmost pixel
Proceed to 8. In step 38 to P ₅ by substituting 0 returns to step 25.

As described above, it is possible to discriminate between an image digital signal as a video signal when it is in the video mode and as a computer image signal when it is in the normal mode.

The video discriminating section 9 for discriminating an image digital signal is realized by, for example, an apparatus configuration as shown in FIG. The video identification unit 9 includes a pixel feature extraction unit 4
0, a pixel characteristic register 41, a luminance difference calculation unit 42, a luminance difference register 43, a mode storage unit 44, a mode determination unit 45, and a synchronization circuit 46.

The pixel feature extraction unit 40 determines whether or not all the RGB values of the input pixel (image digital signal) correspond to a specific luminance value. If all of the RGB values correspond to a specific luminance value, a flag (here, 1) indicating a normal computer image is output, and RGB is output.
If any one of these does not correspond to a specific luminance value, a flag (here, 0) indicating an image is output.

The pixel feature register 41 performs a bit shift while sequentially taking in the flag (1 bit) output from the pixel feature extraction unit 40. In this embodiment, 5 bits
).

The luminance difference calculating section 42 calculates a luminance value difference between each of RGB for the target pixel and its left and right pixels, and determines whether or not the maximum value exceeds a certain threshold value. And
When the maximum value of the luminance value difference exceeds a certain threshold, 1 is output as a flag, and when the maximum value is not exceeded, 0 is output as a flag.

The luminance difference register 43 stores the clock (CL
K) Bit shift is performed while sequentially storing the flag (1 bit) output from the luminance difference calculator 42 in synchronization with the input. In the present embodiment, it is constituted by a 3-bit shift register.

The mode storage section 44 stores whether the current pixel mode is the normal mode or the video mode. The mode storage section 44 synchronizes with the clock (CLK) input.
5 is fetched. Mode determination unit 45
Determines the current pixel mode from the outputs of the pixel characteristic register 41, the luminance difference register 43, and the mode storage unit 44, and outputs the current pixel mode in synchronization with the clock.

The mode judging section 45 includes the pixel characteristic register 4
1. The current pixel mode is determined from the output of the luminance difference register 43 and the mode storage unit 44.

The synchronization circuit 46 synchronizes the RGB input with the mode output. In the present embodiment, a delay circuit is used to transmit the output of four clock data.

Hereinafter, the processing of the video identification unit 9 will be described.
This will be described with reference to the timing chart of FIG. The image data (image digital signal) is given to the video identification unit 9 in synchronization with the clock, and is synchronized with the times T ₁ , T ₂ ,.
_{1, G 1, B 1)} , (R 2, G 2, B 2), assumed to be given as ....

First, at time T ₁ , the pixel data (R ₁ , G ₁ , B ₁ ) is sent to the pixel feature extraction unit 40, the brightness calculation unit 42, and the synchronization circuit 46. Then, the pixel feature extraction unit 40 calculates whether or not all of R ₁ , G ₁ , and B ₁ are a specific luminance value, and outputs the result to the pixel feature register 41 as a flag. In the present embodiment, 1 is output if all have a specific luminance value, and 0 is output otherwise. On the other hand, the brightness difference calculation unit 42 calculates the brightness difference between each of RGB for the given pixel data and the data one time before, calculates whether the maximum value exceeds a certain threshold Th, and calculates the result. It outputs to the luminance difference register 43 as a flag. When the time T _1, the initial value _{(R 0, G 0, B} 0) = performs calculation as (0,0,0). In the present embodiment, 1 is output when the maximum value of the luminance difference between each of the RGB adjacent pixels exceeds a certain threshold value, and 0 is output otherwise.

Next, at time T ₂ , the pixel characteristic register 41 and the luminance difference register 43 store data. At time T _2, the output value of the pixel characteristic register 41 becomes (X, X, 1,1, F 1). X is Don '
t Care, and F ₁ represents the result of the operation on (R ₁ , G ₁ , B ₁ ). The value of the luminance difference register 43 is (X, X, E _0-1 ). E _0-1 is an initial value (0,
0,0) and shows the calculation result of _{(R 1, G 1, B} 1).

Thereafter, the same processing is performed, and the time T_FourIn
The output result of the pixel feature register 41 is (1, 1,
F₁, F_Two, F_Three), The output result of the luminance difference register 43 is
(E_0-1, E _1-2, E_2-3).

The mode judging section 45 includes the pixel characteristic register 4
1 output, 5 high-order bits of the output of the luminance difference register 43, and 1 bit of the output of the mode storage unit 44
Is input, and the calculation is performed as follows.

When the input from the mode storage unit 44 is 0,
When the input from the pixel feature register 41 is (1,1,1, X,
X) and the input from the luminance difference register 43 is (X, 1, X), or the pixel characteristic register 4
The input from 1 is (X, X, 1,1,1), and
When the input from the luminance difference register 43 is (1, X, X), the mode output is set to 1, and otherwise, the mode output is set to 0.

When the input from the mode storage unit 44 is 1,
When the input from the pixel feature register 41 is (1,1,1, X,
If not (X) and not (X, X, 1, 1, 1), the mode output is set to 0; otherwise, the mode output is set to 1.

The result M ₁ obtained by the mode determination section 45 is
It is output at time T ₅ in synchronization with the clock, which indicates the mode of pixel data _{(R 1, G 1, B} 1). on the other hand,
Since the synchronization circuit 46 is implemented as a delay circuit of four clocks, the pixel data at time _{T 5 (R 1, G 1} ,
B ₁ ) is output.

As described above, the mode identifying unit 9 identifies the mode for each pixel, and the image correcting unit 10 performs the correction such as the γ correction processing and the sharpening processing on only the pixels determined as the image. it can. Therefore, even when the image and the normal computer image are mixed on the screen, the effect on the computer image can be reduced and the display quality of the image can be improved. Furthermore, according to the above processing, since the line memory is not used, the video signal correction device of the present invention can be realized with a very small circuit scale.

In this embodiment, the image digital signal is separated into the image signal and the computer image signal by the image discriminating section 9 and the image correcting section 10 corrects only the image signal. A correction unit for correcting only the signal may be provided. In this case, for example, h correct processing can be performed on the computer image signal without affecting the video signal. However, computer image signals are not always very effective because they are often created at the best appearance level.

[0064]

As described in detail above, according to the present invention,
For example, even when a video signal input from a TV antenna or a video input terminal and a normal computer image signal are mixed on the same screen, the display of the video signal portion can be performed without deteriorating the display quality of the computer image signal portion. The quality can be improved. Further, according to the present invention, a video signal stored as digital data in an external storage device can be corrected separately from a computer image signal.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a computer system to which the present invention can be applied.

FIG. 2 is a block diagram illustrating a configuration of an image signal correction device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a processing flow for determining an image digital signal in the embodiment.

FIG. 4 is a block diagram illustrating a configuration of a video determination unit in the image signal correction device according to the embodiment of the present invention.

FIG. 5 is a timing chart for explaining processing of a video determination unit in the embodiment.

FIG. 6 is a graph of a γ function used for γ correction processing of a video signal.

FIG. 7 is a diagram illustrating an example of a filter used for a sharpening process of a video signal.

FIG. 8 is a diagram for explaining a determination error due to a gradation pattern of a video signal.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 antenna 2 tuner unit 3 video capture unit 3 a video input terminal 4 display control unit 5 display unit 6 CPU 7 memory 8 external storage device 9 video identification unit 10 video correction unit 40 pixel feature extraction unit 41 pixel feature register 42 luminance difference calculation unit 43 brightness difference register 44 mode storage unit 45 mode determination unit 46 synchronization circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Rui Sakuta 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Nozomu 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Co., Ltd. F-term (reference) 5C082 AA01 AA02 BA27 BD02 CB01 DA51 MM10

Claims (7)

[Claims] 1. A display unit that can be arranged between a display unit capable of displaying a video signal and a computer image signal on the same screen, and a display control unit that supplies an image digital signal including both signals to the display unit. A separating unit that separates an image digital signal output from the display control unit into a computer image signal and a video signal; and a correction unit that corrects a computer image signal and a video signal that are separated as a video signal. Signal correction device comprising: 2. An image signal separating method for separating an image digital signal including a video signal and a computer image signal, which is supplied from a display control unit to a display unit capable of displaying both signals on the same screen, comprising: Depending on whether or not the luminance value of the image digital signal corresponds to a plurality of predetermined luminance values of a number smaller than the number of colors supported by the display control unit, the image digital signal is converted to the video signal and the computer image. An image signal separation method for determining which one of the signals is used to separate the two signals. 3. The image signal separation method according to claim 2, wherein a multiple of 16 and 255 are used as the plurality of predetermined luminance values. 4. The image signal according to claim 2, wherein whether or not a difference between the luminance value of the image digital signal and a pixel adjacent to the pixel exceeds a predetermined threshold value is considered. Separation method. 5. A display control unit for supplying an image digital signal including a video signal and a computer image signal to a display unit; an external storage device for storing data; a memory for temporarily storing data; And a display unit for performing image display; and an input device for performing input for operation by a user, the image signal correction device according to claim 1, or the image signal separation device according to claim 2. An image signal correction device that separates an image digital signal into a computer image signal and a video signal by a method, and performs correction on a computer image signal and a video signal that are separated as a video signal. A computer system disposed between the display control unit and the display control unit. 6. The image signal correction device according to claim 1, wherein the correction unit performs a γ correction process in a liquid crystal display device on a signal separated as a video signal. 7. The image signal correction device according to claim 1, wherein the correction unit performs a sharpening process on a signal separated as a video signal.