JPH1165512A - Image data converting method for multicolor display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multicolor display device, without causing flickerings of a screen by converting an analog RGB luminance signal into a digital signal by disregarding a prescribed changing amount, even if luminance signal is changed near the boundary of a threshold. SOLUTION: An image is supplied to an A/D image-processing circuit 30 and digitaly converted. An analog RGB luminance signal is divided into respective 16 R, G, B thresholds in an A/D converter circuit 34, converted into luminance signals which are made into digital bits of the respective four R, G, B bits and inputted to an input image frame memory 36. By designating the address of the screen of a personal computer by means of an address memory 40 for a multicolor display device, the RGB luminance signal of the input image is successively outputted to a modifying converter circuit 42, in accordance with the designated order. When the input level is close to an adjacent threshold, by expanding the discriminating level of the next frame, absorbing the fluctuation due to a noise and converting them into the same data as two-bit data to be converted in the next frame, the rotation of a color display body can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen comprising a plurality of color display elements each having a motor mounted on a multicolored color display, and displaying the image by rotating and stopping the color display with the motor. The present invention relates to an image data conversion method of a multi-color display device that switches information such as characters and pictures at several tens of frames per second by changing a color to be displayed, and displays a moving image.

[0002]

2. Description of the Related Art The applicant of the present invention has proposed a circuit for taking in an image signal and performing color display with a high-speed multi-color display device in Japanese Patent Application Laid-Open No. Hei 5-297811. In the related art, an input image (analog RGB luminance signal) such as a television or a video is classified step by step at each luminance level, and once converted into a digital RGB luminance signal, a color display element is further provided. Yellow (Y), magenta (M), cyan (C),
It has been re-classified as white (W), and a plurality of color display elements have been combined to display an intermediate color such as purple, pink, or brown by area gradation. In such a case, if the luminance level fluctuates due to noise or the like, in a self-luminous type element, for example, a light emitting diode (LED), the element emits light in response to a change in input luminance, but is difficult to see due to the afterimage phenomenon of the eyes. Not be. However, in the case of a color display element, the motor rotates every time, which causes flickering.

[0003]

An input image from a television, a video, or the like is an analog RGB luminance signal.
1 dot R, G, B that constitutes a 480 dot screen
, Threshold values for separately sampling are provided, and the range of each threshold value is determined to obtain the type of color that is digitally displayed. If there is a slight difference in luminance or noise between frames near the boundary between these thresholds, even if the color is almost the same in analog, it is digitally determined to be another color, and the color display element has When re-classifying into yellow (Y), magenta (M), cyan (C), and white (W), the color display elements are driven and rotated each time, and the screen flickers and power consumption increases. An object of the present invention is to provide a multicolor display device in which even if an analog RGB luminance signal changes near a boundary of a threshold value, the change is converted into a digital signal ignoring a certain amount of change and the screen does not flicker.

[0004]

The variation of the analog luminance signal Means for Solving the Problems As a digitally suppressing means, the brightness of each frame N _n analog luminance signal of an input image composed of RGB luminance signals in the present invention Is converted into 16-bit bits (A _x ) represented by, for example, 4 bits of digital data according to the threshold value of the above-mentioned level, and classified into 4 rank bits (B _z ) by the weight of, for example, 2 bits of the upper digit. . When the luminance level of the luminance signal in a frame (N _n) is in the A _x bits located near the boundary B _z bits, the A _x bits of the next frame (N n _{+ 1),} for example A _x ± The range of _Bz bits is temporarily expanded to ₁ to absorb slight fluctuations due to noise. In this case, since the input signal is changed, a dead zone naturally occurs, but the input signal falls within a range that cannot be identified by viewing an actual image. Then several frames elapse, for example N
_When the luminance level of the analog luminance signal returns to the vicinity of the center of the _Bz bit when the frame becomes _{n + m} frames, the enlarged _Bz bit is restored. By doing so, the rotation of the motor due to noise can be suppressed, and flickering of the screen can be reduced. To make the above measures even more complete,
There are means for enlarging the dead zone according to the noise amount of the input image, taking the average value of the luminance signals of several frames, and comparing with the luminance signal values of the previous frame. In addition, an overall circuit configuration for realizing the above means, a method of using a working memory, and connection to a drive circuit will be described in detail.

[0005]

FIG. 5 is an embodiment of an exploded perspective view of a color display element which is a component of the present multicolor display device. Four magnetic cores 62 are press-fitted into a base plate 61 made of a soft magnetic material, and coils 67 to 70 are wound around each of the magnetic cores 62, and coils 67 and 68 facing each other and 69 and 70 are connected in series. To form two sets of coils. Four magnetic cores 6
One stator 63 is connected to one upper end of each of the two magnetic cores 62, and the stators are separated by stator gaps 65, which are four gaps between the stators 63a to 63d. The lower end of the rotating shaft 75 attached to the magnet 66 is rotatably supported by being fitted into a hole formed in the main plate 61, and the magnet 66 is magnetized in the diametric direction, and is disposed in a space surrounded by one stator 63. It is located with the magnet gap 64 therebetween and constitutes a motor. The stator frame 76 is a plastic frame that positions and holds the four stators 63a to 63d and covers the stators 63a to 63d and the magnet 66. The upper end of the rotating shaft 75 protrudes through the bearing hole 77 of the stator frame 76, and is pushed into the center hole 79 of the color indicator 78 to be joined. The cylindrical surface of the color display 78 is painted in four colors, and the coil terminals 71 and 7 of the two sets of coils, respectively.
By applying drive pulses from 2, 73 and 74, the color display 78 is rotated to direct the color to be displayed on the display surface.

FIG. 6 is an explanatory diagram showing the dot configuration on the personal computer screen by address. Column X is (X1 to X64
0) and Y row, dots of (Y1 to Y480) are displayed as addresses as shown in the drawing, and a dot (X1
51 to X500) and (Y151 to Y300) are defined as the display space of the present multicolor display device. The number of dots in the display space is 350 dots for the X column and 150 dots for the Y row, for a total of 52,500 dots. One dot of the personal computer screen generally displays an intermediate color by R, G, and B luminance gradations, whereas the multicolor display device of the present embodiment displays one color for one dot of the personal computer screen. Elements are assigned, and each one color display element is white, blue,
It is assumed that it has a performance of displaying four colors of yellow and red.

FIG. 7 is an explanatory diagram for converting an analog RGB luminance signal into a digital signal. When an analog RGB luminance signal is converted into a digital signal, sampling is performed separately for each of R, G, and B. Here, the R luminance signal will be described. In this figure, for example, by dividing into 16 thresholds,
The threshold at which the analog R luminance signal is located is determined by the digital R luminance signal 4 bits (A
_{0 to} A ₁₅ bits). The G and B luminance signals are similarly subjected to digital conversion, and are composed of 4 bits each.

In the first frame (N ₁ ) of FIG. 7, the analog R luminance signal is located at the position of the black dot 212, and when converted into digital, it becomes “1001” from the right 4-bit conversion table.
(A ₉ ). Hereinafter, in the second frame (N ₂ ), the position of the black point 214 is converted into “0111” (A ₇ ), and in the third frame (N ₃ ), the position of the black point 216 is converted into “1001” (A ₉ ). , In the fourth frame (N ₄ ), “1100” from the position of the black point 218
(A ₁₂ ), and the fifth frame (N ₅ )
From position 20 is converted to “1011” (A ₁₁ ), and RG
B is converted into a 4-bit digital RGB luminance signal in the same manner. Represents general symbols A ₀ to A ₁₅ in A _x,
Represents general symbols N ₁ to N ₅ in N _n, is further increased frame represented by N _{n + m} or N _{n + m + p.} m and p are general symbols representing arbitrary numerical values. In order to convert a 4-bit digital luminance signal of R, G, and B into 2-bit data representing the four colors of the color display of this embodiment, the lower 2 bits are generally truncated and the upper 2 bits are taken. Therefore, as shown in the figure, “0000” (A ₀ ) to “0011”
(A ₃ ) is “00” (B ₀ ), “0100” (A ₄ )
“0111” (A ₇ ) becomes “01” (B ₁ ), “100”
0 ”(A ₈ ) to“ 1011 ”(A ₁₁ ) are“ 10 ”
(B ₂ ), “1100” (A ₁₂ ) to “1111”
(A ₁₅ ) is converted to a determination level of “11” (B ₃ ). It represents a general symbol B ₀ .about.B ₃ in B _z.

When the analog luminance signal shown in FIG. 7 has a noise component as shown in the figure, for example, the black point 214 of the second frame (N ₂ ) has a median value of “0111”.
Even (A ₇ ), “0” depends on the detection timing.
110 ”(A ₆ ).
In the case of bits, even if they are converted to 2 bits, they are all "0".
Since the discrimination level is 1 ″ (B ₁ ), the color display does not rotate. However, in the next fourth frame (N ₄ ) and fifth frame (N ₅ ), almost the same data is used as the analog luminance signal. Nevertheless, depending on the noise and the timing of detection, “110” is used in the fourth frame (N ₄ ).
0 "(A _12), the fifth frame (N ₅₎ In" 1011 "
(A ₁₁ ). Converting this to 2 bits gives
In the fourth frame (N ₄ ), it is converted to “11” (B ₃ ), and in the fifth frame (N ₅ ), it is converted to “10” (B ₂ ). As described above, even when data of substantially the same level continues, data may change every frame due to a change in amplitude due to noise or a detection timing shift, and each time the color display rotates and flickers on the screen. Is generated. Further, even when the analog luminance signal has no noise, if similar data continues for many frames near the boundary of the threshold value, the data is converted to one for each frame, so that the screen may flicker.

FIG. 1 is an explanatory diagram showing a method of converting a 4-bit digital luminance signal into 2-bit data according to the present invention. Input image described in FIG. 7 is transformed, converted by the setting of the threshold at N ₁ frame in Figure 1 R, G, and B luminance signals of each 4-bit digital, further R, G, B in each 2-bit data Is done. Hereinafter, the method of the present invention for performing digital correction near the threshold boundary will be described.

In the fourth frame (N ₄ ) of FIG. 7, the data discrimination levels are “1111” (A ₁₅ ) to “1100”.
(A ₁₂ ), and a 2-bit digital R
When converted to a luminance signal, it is “11” (B ₃ ),
“110” where the luminance level of the input signal is close to the adjacent threshold value
0 "when (A ₁₂₎ to a like is as shown in N ₂ frame in FIG. 1, for the next fifth frame (N _5), the data" 11 "to determine the level of (B _3)" 1011 "(A
The method of the present invention is to expand to ₁₁ ) and absorb the fluctuation due to noise.

As described above, when the input level is close to the adjacent threshold value, fluctuations due to noise are absorbed by expanding the discrimination level of the next frame, and the same data as the 2-bit data converted in the next frame. The color display body does not rotate and flickering can be suppressed. In this case, the range for expanding the threshold is at most one level. However, when the range of fluctuation due to noise is large, the number of levels of the threshold is increased, the bit division is set to 6 to 8 bits, and then 2 to 3 bits. You may enlarge and set to a level.

[0013] As described above, the table of the modified luminance signal of FIG. 1, when it comes to data or N ₂ frames N ₁ frame,
The discrimination level of 2-bit data “11” (B ₃ ) is “1”.
The data in the fifth frame (N ₅ ) in FIG. 7 is referred to as “this data” in the fourth frame (N ₄ ) in an enlarged form from “111” (A ₁₅ ) to “1011” (A ₁₁ ). Is compared with the “previous data”, but each data is stored in a separate memory 1 (fourth frame (N ₄ )) of FIG.
), And stored in the memory 2 (data of the fifth frame (N ₅ )), and then data comparison is performed for each of the RGB dots. The data of the fifth frame (N ₅ ) of the memory 2 is compared with the data of the fourth frame (N ₄ ) and corrected, and then the data of the fourth frame (N ₄ ) of the memory 1 is erased and stored in the memory 1. The data is written as "new fifth frame (N ₅ ) data", which becomes the "previous data", the data of the sixth frame (N ₆ ) is written as "current data" in the memory 2, and so on. The comparison continues.
The display by the color display is performed in the “new fifth frame (N
₅ ) Data ”is performed.

In the above description, the luminance signal is first classified into four-bit thresholds (A _{0 to} A ₁₅ ), and two bits (B _{0 to} B ₁₅ )
~ B ₃ ), but 8 bits vs. 3 bits,
The combination of the classification number of the input image and the color display such as 16 bits versus 4 bits is arbitrary. In addition, the range of the threshold value expansion may be expanded to one or three levels depending on the state of the input signal from the method of expanding the threshold by one level as described above. Also, the frame comparison is not limited to the “last time” and “this time”. Rather, several frames are stored, and an average value of the data is obtained and compared, thereby obtaining image data more stable against noise. be able to.

FIG. 2 shows a first embodiment of a method for converting a luminance signal into data for each frame according to the present invention. A method of converting a digital bit luminance signal underlined with the luminance signal shown in the figure will be described. As described with reference to FIG. 1, the range in which the threshold value is expanded will be described up to one level. Previous state of the N _n frames, as shown in N ₁ frame in Figure 1, determines the level _{"00" (B 0) ~} "1
1 ”(B ₃ ).

In the N _{n -th} frame of FIG. 2, "1100"
Assuming that (A ₁₂ ) is detected, 2-bit data is converted to “11” (B ₃ ). When N _{n + 1} frame "1011" (A ₁₁₎ is detected, is compared with the luminance signal "1100" of the N _n frame (A _12), it is determined it from one level lower luminance signal. In this case, it is regarded as a range of fluctuation due to noise, and as described in FIG.
The discrimination level of 2-bit data “11” (B ₃ ) is “1”.
011 ″ (A ₁₁ ), and 2 of the N _{n + 1 th} frame
The bit data is converted to “11” (B ₃ ). “1111” (A ₁₅ ) to “101” continuously from the next frame.
When “1” (A ₁₁ ) is detected, all “11” are detected.
The determination level is (B ₃ ). “1” in the N _{n + 2} frame
010 "When (A ₁₀₎ is detected, the N _{n + 1} frame luminance signal" is compared with 1011 "(A _11), wherein any time it is determined that one level lower luminance signal, the threshold in the second frame Has already been expanded by one level, and is not expanded, but is converted into 2-bit data "10" (B ₂ ).
“1011” (A ₁₁ ) is also returned to the original determination level of “10” (B ₂ ), and the determination level “0” before the N _n-th frame is returned.
_{0 "(B 0) ~"} 11 "(B 3) is a state of being uniformly divided. At the N _{n + 3} frame," 1011 "(A
_{When 11} ) is determined, it is compared with the luminance signal of the N _{n + 2th} frame, and is determined to be data one level higher, but the same “10” (B ₂ ) determination is performed even when converted to 2-bit data. since the level is converted to 2-bit data "10" (B _2). Such conversion is performed for each frame, and noise fluctuations are absorbed by similarly expanding or returning the threshold value for the other luminance signals shown in the figure. It should be noted that the frame for which the threshold value is returned is performed in the N _{n + m-th} frame or the N _{n + m + p-th} frame depending on the noise state of the luminance signal. m and p are general symbols representing arbitrary numerical values. Hereinafter, if the N _{n + 1 th} frame is defined as “the current frame”, the N _{n th} frame is defined as the “previous frame”, and the N _{n + 2 th} frame is defined as the “next frame”.

FIG. 3 shows a second embodiment of the method for converting a luminance signal into data for each frame according to the present invention. Differs from the first embodiment in FIG. 2, the first previous time in the embodiment of the frame (the N _n frame) of time to go back expansion and threshold with reference to the luminance signal of the frame (N-th _{n + 1} frames)
Was converted to 2-bit data, but in the second embodiment of this figure, the threshold value is determined with reference to the luminance signal of the next frame (the N _{n + 1 th} frame as viewed from the N _{n th} frame). The enlargement and restoration are performed, and the luminance signal of the current frame (N _nth frame) is converted into 2-bit data based on the result. Previous state of the N _n frames, as shown in N _n frames of Figure 1, the data discrimination level "00" (B ₀₎ of the luminance signals ~ "11" (B ₃₎ to be divided equally State.

In the N _n-1 frame shown in FIG.
0 "(A ₁₀₎ but is as has been detected, does not perform the conversion in this frame. Then at the N _n frames" 110
If “0” (A ₁₂ ) is detected, “1010” (A ₁₀ ) of the N _{n-1 th} frame is not an adjacent threshold value as described with reference to FIG. N
determine the level of _n-1 frame is "10" (B _2).
The N _{n + 1} frame "1011" follows the (A ₁₁₎ is to have been detected, "1100" of the N _n frame (A ₁₂₎
Since the threshold value is adjacent to the N _{n -th}
The determination of the frame "10" and (B _2). Next, the N-th
_Assuming that “1100” (A ₁₂ ) is detected in the ( _{n + 2} ) _-th frame, the determination level of “11” (B ₃ ) is normally “1” because the determination level has already been expanded in the (N _{n + 1) -th} frame.
0 "(B ₂ ), and the expanded discrimination level remains unchanged. If the next N _{n + 3} frame is" 1100 "
If (A ₁₂ ) continues, the discrimination level is “10” (B ₂ ), but if it is “1101” (A ₁₃ ) in the figure, “101” (A ₁₃ )
Since it is not adjacent to “1” (A ₁₁ ), the expanded determination level is returned to the original level, and “1100” (A ₁₂ ) is replaced with the normal “1”.
1 "as a determination level (B _3). This example first embodiment in a manner to determine the discrimination level of the previous frame by referring to the luminance signal data of the next frame, when a high frame frequency The same effect can be obtained.

FIG. 4 is an explanatory diagram of a circuit embodying the present invention. Images displayed on the screen of a personal computer (image output source) are transmitted from a television, video, image scanner,
The data is supplied to the image processing circuit 30 and is converted into a digital image having a screen size of a personal computer, for example, 640 × 480 dots, and is displayed on the screen of the personal computer 32 at a speed of 30 frames. On the screen of the personal computer 32, one dot is displayed in an analog manner in a combination of R, G, and B.
The A / D conversion circuit 34 divides the GB luminance signal into 16 R, G, and B thresholds as described with reference to FIG.
The luminance signal is converted into a 4-bit digital bit luminance signal and input to the input image frame memory 36.

The input image frame memory 36 stores all digital RGB luminance signals of a frame frame of 640 × 480 dots on a personal computer screen. The storage order is
Each dot is controlled by a vertical synchronizing signal (VS) and a horizontal synchronizing signal (HS) of the personal computer 32 input to the writing control circuit 38, and addresses are assigned according to a time series and are sequentially stored. When extracting the data stored in the input image frame memory 36, for example, the address (X151, Y151) of the personal computer screen indicated by the thick line in FIG.
If (X500, Y300) is specified by the multi-color display device address memory 40, the RGB luminance signals of the input image are sequentially output to the correction conversion circuit 42 in the specified order.

The correction conversion circuit 42 is a circuit for comparing the 4-bit R, G, and B luminance signals of the previous frame and the current frame and converting them into 2-bit luminance signals.
4) and the memory 2 (46) as working memory. The operation will be described with reference to the first embodiment (FIG. 2). In one memory (for example, the memory 1 (44)), the 4-bit luminance signal of the previous frame (the N _n-th frame) is stored, and the memory 2 (46) is stored. ) Is the current frame (N _{n + 1} frame)
Are stored and re-input to the correction conversion circuit 42 to compare the weight of each bit. When converting to 2 bits, select whether to use the enlarged level “11” or the normal level “10”. Then, the result is stored in the discrimination level memory 47. The 2-bit result converted at the same time is output to a data conversion circuit 48 for a multi-color display device described later. The N _{n + 2}
In the frame period, the 4 bits of the memory 2 (46) are transferred to the memory 1 (44) and become the "previous frame", and the _{Nn + 2th} frame becomes the "current frame" and the memory 2 (46). 46), is re-input to the correction conversion circuit 42, and the same bit weight comparison is performed. The 2-bit determination is performed with reference to the contents of the determination level memory 47, and the result is used as a new value. Discrimination level memory 4 as information
7 and also output to the multi-color display device data conversion circuit 48. Hereinafter, the above operation is repeated. The same applies to the second embodiment shown in FIG.

The multi-color display device data conversion circuit 48 includes:
R, G, and B separately converted 2-bit data are input, and a total of 6 bits are combined to create gradation color data, and the color display element described with reference to FIG. The color data is converted into color data, and the output is sequentially input to the multi-color display device driving circuit 50 to store one frame to be displayed once, and then start all at once to convert the screen of the multi-color display device 52 to the screen. I do. The above operation is performed at a speed of 30 frames per second, and a moving image at the same speed as the television can be displayed.

[0023]

According to the present invention, a slight difference in luminance and fluctuation due to noise in an input image for each frame of a television or a video can be substantially absorbed, and a color display element used in the present invention is unnecessary. This eliminates unnecessary rotation and has a great effect on screen flicker, power consumption, and motor durability. The present invention relates to a self-luminous element such as a light emitting diode (LE).
D) and the like, but it is an indispensable method especially for a color display element using a motor.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a method of converting a 4-bit digital luminance signal into 2-bit data according to the present invention.

FIG. 2 is a first embodiment of a method of converting a luminance signal into data for each frame according to the present invention.

FIG. 3 is a second embodiment of the method for converting a luminance signal into data for each frame according to the present invention.

FIG. 4 is an explanatory diagram of a circuit embodying the present invention.

FIG. 5 is an embodiment of an exploded perspective view of a color display element which is a component of the present multicolor display device.

FIG. 6 is an explanatory diagram showing a dot configuration of a personal computer screen by an address.

FIG. 7 is an explanatory diagram when converting an analog RGB luminance signal into a digital signal.

[Explanation of symbols]

 34 A / D conversion circuit 36 Input image frame memory 38 Write control circuit 40 Address memory for multi-color display device 42 Correction conversion circuit 44 Memory 1 46 Memory 2 47 Discrimination level memory 48 Data conversion circuit for multi-color display device 50 Multi-color display Device drive circuit 52 Multicolor display device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuo Kasahara 5-6-112 Maehara-cho, Koganei-shi, Tokyo In-house of TII Citizen Koganei Co., Ltd. (72) Inventor Yoshihiko Yanagawa Tokorozawa, Saitama 840 Takeno, Shimotomi, Citizen Watch Co., Ltd.

Claims (5)

[Claims] 1. A means for converting the N _n frames of the input image composed of RGB analog luminance signal to the luminance level digital A _x bits by the threshold according to the of the analog luminance signal, common the A _x bits means for converting the B _z bits constituting the upper digit bits when the luminance level of the analog luminance signal of the first n _n frame is in the a _x bits located near the boundary B _z bits, the n _{n +} means for temporarily expanding the a _x bits a _x range ± to _y of B _z bits of _one frame, to the n _{n + m} frames, the luminance level of the analog luminance signal is in the center direction of the B _z bits When returning, the B _z
Means for restoring bit enlargement to the original state. An image data conversion method for a multicolor display device, comprising: 2. The multicolor display device according to claim 1, further comprising means for setting the y term of A _x ± _y arbitrarily in proportion to the noise level of the RGB analog luminance signal. Image data conversion method. 3. means for converting the N _n frames of the input image composed of RGB analog luminance signal to the luminance level digital A _x bits by the threshold according to the of the analog luminance signal, common the A _x bits upper means for converting the B _z bits constituting the digit bit, when the luminance level of the analog luminance signal of the first n _n frame is in the a _x bits located near the boundary B _z bits, the n _n frames To N
_Ax bits of average value up to _{n + m} frames are _converted to _Ax ± _y to _Bz
Means for temporarily expanding the range of bits; and N _{n + m + P}
In the frame, the luminance level of the analog luminance signal is B _z
Means for restoring the enlargement of the _Bz bit when returning to the center direction of the bit, and a method for converting image data of a multicolor display device. 4. A means for converting the N _n frames of the input image composed of RGB analog luminance signal to the luminance level digital A _x bits by the threshold according to the of the analog luminance signal, common the A _x bits means for converting the B _z bits constituting the upper digit bits when the luminance level of the analog luminance signal of the first n _n frame is in the a _x bits located near the boundary B _z bits, the n _n- the a _x bits of _a frame and means for temporarily expanding the range of a _x B _z bits to ± _y, the luminance level of the analog luminance signal to a n _{n + m} frames return towards the middle of the B _z bits Means for restoring the enlargement of the _Bz bit when restored. 5. Convert the first N _n frames of RGB of an input image composed of an analog luminance signal to a digital A _x bits by the threshold level of the luminance of the analog luminance signal,
Common and A / D conversion circuit for converting the B _z bits constituting the upper significant bits of the A _x bit level near the boundary of B _z bits of the luminance of the analog luminance signal of the N _n frames of the A _x bits a determination level memory to detect that it is in, the first n _n frame or a _x bits of n _n ± ₁ temporarily enlarged a _x B _z of bit range to ± _y, the n _{n + m} or n _n a _{+ m + P-frame,} wherein when the luminance level of the analog luminance signal is returned to the central direction of the B _z bits, and modified converter to undo expansion of the B _z bits, the input and output of the modified conversion circuit A working memory for temporarily storing digital data, a multicolor display data conversion circuit for converting the output of the correction conversion circuit into multicolor display data, and a multicolor display device based on the output of the data conversion circuit Circuit for driving multicolor display device A method for converting image data of a multi-color display device, comprising: