JPH08221027A - Display device - Google Patents

Abstract

(57) [Summary] [Object] To display a color image with reduced flicker while reducing the power consumption required for deflection even if a frame sequential method is adopted, and reducing the load on the deflection circuit and the deflection device. Get a display device that can. [Structure] In each of the three field screens of R, G, and B forming one frame, line scanning is performed by interlacing 3: 1 so as not to overlap with scanning lines forming field screens of other colors. Do 3 consecutive times
In a frame, a scan pattern is formed so that scan lines do not overlap between field screens of the same color.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device adopting a frame-sequential system, and it is preferable to display a color image by frame-sequential display, for example, when a flat cathode ray tube is used for an image receiving device. It is suitable for application to devices,

[0002]

2. Description of the Related Art As a picture tube, in addition to a so-called normal straight type CRT, a flat type CRT is known. In a straight CRT, the axis of the electron gun (the path of the electron beam when it is irradiated without being deflected)
A raster is formed while deflecting the electron beam with respect to the fluorescent film surface arranged so as to be substantially orthogonal to the fluorescent film surface. However, in the flat type cathode ray tube, the fluorescent film surface is arranged in a positional relationship substantially along the axis of the electron gun, and for example, the electron beam is deflected to nearly 90 ° to irradiate the fluorescent film surface. For example, in the case of a straight type CRT, it is difficult to obtain a small monitor device (or a television receiver) because the structure inevitably has a long depth, but the monitor device is configured using a flat type CRT. In such a case, it is possible to make the housing have a short depth, and the size can be reduced accordingly, and the selection of the actual installation place and the range of applications can be expanded.

7 (a) and 7 (b) show side views of structural examples of the flat type cathode ray tube (which is a reflection type in this case) and the straight type cathode ray tube.
In both figures, the same components are designated by the same reference numerals even if the shapes are different.

In each of the flat cathode ray tube 0 shown in FIG. 7A and the straight cathode ray tube 0a shown in FIG. 7B, 1 is a neck portion, 2 is a funnel portion, and 3 is a display main body portion. . An electron gun 5 having an electron lens 6 is provided in the neck portion 1 of each figure, and the axes of the electron gun are shown by solid lines C, respectively. Further, on the inner wall side of the display main body portion 3, as shown in the figure, there is provided a screen 4 forming a phosphor film surface coated with a phosphor that emits light upon collision of an electron beam. The viewing direction for seeing the image obtained on the screen 4 is as shown in FIG.
The display surface portion 7 is seen through from above in (a), while the straight type cathode ray tube 0a is seen through the display surface portion 7 from the front direction of the cathode ray tube (rightward direction in FIG. 7 (b)). It will be. A deflection yoke 8 for deflecting the electron beam in the horizontal and vertical directions is provided on the outer peripheral portion of each funnel portion 2. The deflection yoke 8 is composed of a deflection coil 9 and a ferrite core 10. There is.

Further, when displaying a color image, a picture tube is provided with three electron beams corresponding to R, G, and B colors, and these electron beams are simultaneously displayed on the screen.
A so-called simultaneous system is known as a normal system in which line scanning is performed by irradiating the phosphor of B. For example, in the straight type CRT shown in FIG. The scheme is used. Also,
As another method, one field screen is made to correspond to R, G, and B colors, one frame is formed by these three field screens, and one color image is formed by the afterimage phenomenon obtained on each field screen. There is also known a so-called frame-sequential expression designed to express. For example, specifically
A filter capable of passing only R, G, and B colors is provided on the screen of the picture tube, and only one of the R, G, and B filters can transmit light for each field. The R, G, and B field images are obtained by sequentially performing switching control so as to be in the state. In particular, in the case of the flat type cathode ray tube as shown in FIG. 7A, it is difficult to display a color image by the simultaneous type like the above-mentioned straight type cathode ray tube. Therefore, such a frame sequential method is adopted. It is preferable.

By the way, when an attempt is made to express a full-color image for one frame in the simultaneous type and the frame sequential type,
If line scanning is performed at the same scanning speed (horizontal scanning frequency) in the simultaneous method and the frame-sequential method, one frame of the one color in the frame-sequential method can be displayed within a period in which the simultaneous method can express a full-color screen of one frame. Only the field screen can be expressed. In other words, in the field-sequential system, the field screens for each of R, G, and B colors are sequentially displayed for each time length corresponding to one frame in the simultaneous system. (Flicker)
Is conspicuous, and good image quality cannot be obtained.
Therefore, for example, the field double speed processing is performed on the original video signal, and the horizontal deflection frequency and the vertical deflection frequency are increased until scanning of three field screens is performed within one frame period, and the same frame period time as in the simultaneous system is used. A frame sequential method is known in which a full-color image for one frame is represented.

FIG. 8 is a diagram showing the comparison of the scanning timings of the simultaneous type and the frame sequential type in which the deflection frequency is increased as described above. In this case, a frame frequency of 60 Hz (16.8 ms) and 600 horizontal scanning lines (however, not shown in the figure and shown by 6 scanning lines) are used for both the simultaneous system and the frame sequential system. The following description will be made assuming that progressive scanning is performed by interlacing. First, in the simultaneous system, 60 in the frame period of 60 Hz.
Since 0 scanning lines are sequentially scanned,
As shown in FIGS. 8A to 8C, 36 KHz (27.
Line scanning is performed at a horizontal scanning frequency of 8 μs. That is, 200 lines are sequentially scanned every 180 Hz (5.6 ms). As a result, one frame image is obtained for each frame frequency of 60 Hz as shown in FIG.

Next, in the frame-sequential system, since it is necessary to form three field screens expressing R, G, and B colors within a frame period of 60 Hz, the horizontal deflection frequency is 108 KHz, which is three times that of the simultaneous system. (9.3 μs), and
The vertical deflection frequency (field frequency) is also set to 180 Hz, which is three times that of the simultaneous equation, and 600 scanning lines are scanned at every 180 Hz field period as shown in FIGS. A field screen for each of G and B is formed. In this case, the order of R, G, and B colors displayed on the three field screens is arbitrary. As a result, as shown in FIG. 8 (h), 60 Hz
For each frame frequency, a full-color image similar to the simultaneous type shown in FIG. 8D is apparently obtained. At this time, however, the time length for which the field screen for each color is individually displayed is also the frame. 1/3 of 16.8 ms for frequency
Since it is about 5.6 ms (field frequency 180 Hz), flicker can be reduced and image quality can be improved.

[0009]

However, the above-mentioned FIG.
In the frame sequential method of the method described in (a) to (d), the horizontal deflection frequency and the vertical deflection frequency are tripled as compared with the simultaneous method. Vertical deflection frequency is 180
The horizontal deflection frequency is 108 KHz, which is considerably high as the deflection frequency, though it is not a problem because it is as low as Hz. This allows
Along with the problem that the power consumption required for the electron beam deflection increases and the efficiency deteriorates, the deflection circuit on the horizontal deflection side for performing line scanning and the deflection device such as the deflection yoke are newly designed or selected for high frequencies. Therefore, there will be problems such as a decrease in manufacturing efficiency and an increase in cost.

[0010]

Therefore, in order to solve the above-mentioned problems, the present invention reduces the power consumption required for the deflection even if a frame sequential method is adopted, thereby reducing the load on the deflection circuit and the deflection device. An object of the present invention is to obtain a display device capable of displaying a color image with reduced flicker while being reduced.

Therefore, according to the present invention, in a display device for displaying a color image by field sequential display in which field screens corresponding to respective colors of R, G, B are sequentially displayed, at least one frame is formed. In each of the three field screens, line scanning is performed so as not to overlap with the scan lines forming the field screens of other colors. Furthermore, in three consecutive frames, the scan lines are overlapped between the field screens of the same color. It is configured to form a line scanning pattern that does not occur. Then, in order to realize the line scanning pattern as described above, a line output conversion circuit that converts the output order of the lines of the original video signal corresponding to the line scanning pattern is provided, and
A DC component variable section is provided so as to vary the level of the DC component superimposed on the sub deflection current for each field period in accordance with the line scanning pattern. And
A flat type picture tube is used as the image receiving device.

[0012]

For example, in displaying an image by a frame sequential method in a display device using a flat cathode ray tube, fields of other colors are formed between the three R, G and B field screens forming one frame. Line scanning is performed in a state in which every two lines are interlaced so as not to overlap the scanning lines forming the screen. As a result, the number of scanning lines for each field screen is set to ⅓ of the total number of scanning lines. ,
It is possible to obtain a color image for one frame in which the colors G and B are visually combined. If line scanning is performed so that scanning lines do not overlap between field screens of the same color in three consecutive frames, Re
An image without horizontal stripes of d, Green, and Blue
The R, G, and B field screens can be obtained in units of 9 field screens that are repeated three times. Then, in accordance with the line scanning pattern as described above, a line output conversion circuit that converts the output order of the lines of the original video signal and a DC component that is superimposed on the sub deflection (vertical deflection) current for each field period. The line scanning according to the present invention can be easily realized by providing the direct-current component variable unit that varies the level.

[0013]

Embodiments of the display device of the present invention will be described below with reference to FIGS. As described above, the frame-sequential type is effective when used in a flat type cathode ray tube, so in this embodiment, a flat type cathode ray tube is used as a picture tube, but it is described as compared to a normal straight type. However, it is naturally applicable. Further, the structure of the picture tube used in the present embodiment may be the same as that shown in FIG. 7 regardless of whether it is a flat type or a straight type.

In the image display by the frame sequential method of this embodiment,
The unit of the frame screen consisting of a total of three field screens corresponding to each of R, G, and B is called "pre-frame", and the apparent screen obtained by repeating this pre-frame three times is completely. It is supposed that the display is performed as a "complete frame" in which a video for one frame is reproduced.
Therefore, first, the formation of the pre-frame will be described with reference to FIG. In the case of this embodiment, the frame frequency is 60 Hz, as in the case shown in FIG.
(16.8 ms), and 600 horizontal scanning lines (however, it is omitted in the figure and shown by 6 scanning lines).

First, the first 180 Hz shown in FIG.
The field frequency period of R forms a field screen of R color, for example. Specifically, with a horizontal deflection frequency of 36 KHz (the same as the simultaneous equation shown in FIG. 8), scanning is actually performed in a pattern of lines that jump every two scanning lines. Then, within this period, for example, the above-described filter is switched so as to transmit only R, so that an R field image composed of a total of 200 scanning lines can be obtained. FIG.
In the screen of (a), this state is conceptually shown by two scanning lines. It should be noted that at the time of G and B field screen scanning described below, the filter is assumed to be switched so as to transmit only G or B light.

Next, during the period of the second field frequency (180 Hz) shown in FIG. 1B, for example, a field screen of G color is formed. In this case, the interlaced scanning in which every other line is used as a scanning line is performed in the same manner as in the immediately preceding field period, but a scanning line at a position which does not overlap with the scanning line scanned in the immediately preceding field period is set. It will be scanned. For example, in the case of FIG. 1B, the scanning line located one position below the line scanned in the immediately preceding field period of FIG. 1A is sequentially scanned. Therefore, in this field period, a G field image consisting of a total of 200 scanning lines different from the immediately preceding line is obtained. Then, in the next third field cycle, a pattern of every two lines is formed so as not to overlap the scanning lines forming the first and second field screens shown in FIGS. 1A and 1B. Interlaced scanning is performed to obtain a G field image consisting of 200 scanning lines.

As described above, as shown in FIGS. 1A to 1C, line scanning is performed so that interlacing is performed for each of the R, G, and B field screens. As a result, 60 Hz (1
At a frame frequency of 6.8 ms, as shown in FIG. 1D, 600 lines are apparently arranged such that the scanning lines are arranged in the order of R → G → B → R → G → B. A frame image obtained by scanning is obtained. By doing so, at least 60 Hz (16.8) corresponding to the simultaneous frame frequency shown in FIGS.
Since it is possible to obtain an image of one frame expressing all colors of R, G, and B within the time of (ms), the flicker is the same as that of the simultaneous type in the present embodiment, although the horizontal deflection frequency is 36 KHz. As an example, the horizontal deflection frequency of 108 KHz shown in FIGS. 8E to 8H can be reduced to the same level as that of the frame sequential method.

In the present embodiment, the unit of the frame picture formed at the frame frequency of 60 Hz (16.8 ms) as shown in FIG. 1D is called a pre-frame. Although the field screens are displayed in the order of R, G, and B in FIG. 1, the order may be changed as an example.

Next, the formation of a complete frame obtained by synthesizing three pre-frame screens will be described with reference to FIG. The frame frequency of 60 Hz (16.8 ms) will be referred to as a pre-frame frequency hereinafter. The pre-frame screen shown in FIG. 2 (a) is shown in FIG.
It is the same as the pre-frame screen described in (d). If the pre-frame screen shown in FIG. 2A is repeated every 60-Hz pre-frame cycle, only the same color corresponds to the same scanning line, so that a visually visible image is obtained. Red, green, and blue stripes will be noticeable.

Therefore, in the present embodiment, if the pre-frame screen shown in FIG. 2A is the first pre-frame screen, for example, the first pre-frame screen will be displayed in the next second pre-frame cycle. In order not to overlap the same color as the scanning line in the frame period, each R, G, B field period (180
(Hz), interlaced scanning is performed with a pattern every two lines.

Specifically, for example, in the pre-frame screen of FIG. 2A, the scanning lines are arranged in the order of R.fwdarw.G.fwdarw.B.fwdarw.R.fwdarw.G.fwdarw.B, while in FIG. 2B. Second as shown in
On the pre-frame screen of B → R → G → B → R →
Line scanning is performed in each R, G, and B field period within this pre-frame frequency so that the scanning lines are arranged in the order of G to.

Then, in the subsequent third pre-frame period, the pre-frame screen is formed so that the same color as the scanning line does not overlap with any of the first and second pre-frame screens. Yes, for example, as shown in FIG. 2C, the pre-frame screen is B → R → G → B.
R, G, and B line scanning is performed in each field period so that the scanning lines are arranged in the order of → R → G.

As a result, the three pre-frame screens shown in FIGS. 2A to 2C are continuously formed at 20 Hz (5
In the period corresponding to the frequency of 0 ms),
As shown in (d), a state in which all 600 scanning lines are scanned once for each of the colors R, G, and B is obtained, and the original video signal is completely The reproduced state can be obtained. In addition, since the scanning pattern is configured so that the same color does not correspond to the same scanning line between consecutive pre-frames, the red, green, and blue stripes are eliminated.

In order to realize the line scanning with the pattern as described with reference to FIGS. 1 and 2, the horizontal line video signals are output in the order corresponding to the scanning pattern from the normal horizontal line video signal output order. Is converted so that the
The deflection circuit is configured so as to scan in the pattern shown in FIG.

Therefore, first, FIG. 3 shows a video signal conversion circuit for converting the input original video signal into a signal in the line output order corresponding to the scanning pattern of this embodiment. In the video signal conversion circuit shown in this figure, 21 to 23 are A /
A D converter is shown, which inputs analog composite signals corresponding to R, G, and B, respectively, and performs sampling on each of these signals based on the clock frequency from the memory controller 28 to convert them into digital signals. Further, 24 to 26 are field memories capable of holding video signal data, respectively. For example,
In the present embodiment, since the number of scanning lines in an image for one field is 600, there is a memory area corresponding to at least 600 rows, and an image for one horizontal line is provided for each row. The signal data can be stored. Further, it is preferable that the field memories 24 to 26 are 2-port type field memories capable of reading and writing simultaneously. And
Reference numeral 24 is a field memory corresponding to an R image, 25 is a G image, and 26 is a field memory corresponding to a B image. In the figure, each field memory 2
4 to 26 conceptually show the first 6th line. Further, 27 is a D / A converter for converting a digital signal into an analog signal based on the clock frequency from the memory controller 28, and 28 is a clock of a predetermined frequency for the A / D converters 21-23 and the D / A converter 27. Field memory 24 to
26 is a memory controller configured to control 26 write / read timings and addressing.

In the video signal conversion circuit having the above structure, the video signal corresponding to R converted into a digital signal by the A / D converter 21, for example, is supplied to the field memory 24. While the rows are incremented at a predetermined timing, the data for one horizontal line is sequentially written in the order of the horizontal lines forming the original video signal. The video signals corresponding to G and B converted into digital signals by the A / D converters 22 and 23 are also written in the field memories 25 and 26 in the same manner as above.

The field memories 24 to 26 are read out at the timings described below so that the pre-frame and complete frame shown in FIGS. 1 and 2 are formed.

First, in the first field period (180 Hz) within the pre-frame frequency forming the first first pre-frame, the field memory 24 corresponding to R stores the video signal of R1. Data is read out sequentially. That is, the signal data of a total of 200 horizontal lines is sequentially read every two rows from the top, starting from the first row. The read control is executed by the memory controller 28 while addressing at a predetermined timing. The video signal of R1 read out as described above is
The analog / horizontal line video signal is converted by the D / A converter 27 and then supplied to a video output circuit (not shown) for display on a picture tube, which is shown in FIG.
Corresponds to the R field screen shown in FIG.

Then, in the next second field period, the data of the row indicated by G1 is sequentially read from the field memory 25 corresponding to G, that is, 2 from the beginning.
Similarly, the reading is sequentially performed every two rows starting from the row, which corresponds to the G field screen shown in FIG. 1B. Further, in the next third field period, from the field memory 26 corresponding to B, every two rows starting from the third row from the beginning, B1 in the figure.
The data of the video signal of the line described as is read in, and this forms the field screen of B shown in FIG. 1 (c).

In this manner, by converting the output order of the video signals of the horizontal lines from the field memories corresponding to the respective colors and outputting the converted video signals in every three consecutive field periods, as shown in FIGS. The line scanning pattern shown corresponds to the position of the video signal as a horizontal line, and as a result, the first pre-frame screen shown in FIGS. 1D and 2A is formed. Become.

Then, in the next field period within the second pre-frame frequency, every second line from the second line at the beginning of the field memory 24, R,
The data of the horizontal line indicated by 2 will be sequentially read. Then, in the next field period, the horizontal line data indicated by G2, which is every two lines from the third row from the beginning, is read from the field memory 25, and from the field memory 26 every two lines from the beginning in the third field period. Then, the data of the horizontal line indicated by B2 is read out. The horizontal line video signal read out every three field periods is shown in FIG.
This corresponds to the positions of the lines of the R, G, and B scanning patterns shown in (b), and the second pre-frame screen can be formed.

Further, in the first field period in the third pre-frame frequency, every two lines from the third line at the beginning of the field memory 24, R3.
The data of the horizontal line indicated by is read in order, the data of the horizontal line indicated by G3 which is every two lines from the beginning is read from the field memory 25 in the next field period, and from the field memory 26 in the third field period. The data of the horizontal line indicated by B3, which is every two lines from the third line from the beginning, is read. Then, since the video signal of the horizontal line for each of the three field periods corresponds to the position of the line of the scanning pattern of R, G, B which is the same as that shown in FIG.
A frame screen can be formed. Then, at the stage where the reading of the data at the timing described so far has completed, the data of the horizontal line that can form the complete frame shown in FIG. 2D has been read. After that, the above-mentioned read operation is repeatedly executed along with the writing of the video signal data.

Here, FIG. 4 shows the configuration of the video signal obtained at the above-mentioned read timing on the time axis. In the first pre-frame, the video signal data of the horizontal line is read out from each field memory at every field cycle.
Read and play in the order of 1 → G1 → B1, and read 3 sheets of R,
It is configured by forming G and B field screens, and the subsequent second pre-frame and third pre-frame also have video signal data R2 of a horizontal line for each field cycle.
→ G2 → B2 and R3 → G3 → B3 are read in this order. That is, the memory controller 28 controls the field memories 24, 25, 2 according to the field cycle.
6 to R1 → G1 → B1 → R2 → G2 → B2 → R3 → G
The process of reading the video signal data of the horizontal line is repeated in the order of 3 → B3.

Next, a deflection method for realizing the above line scanning will be described. The line scanning pattern for each field period described so far with reference to FIGS. 2 and 3 is divided into any of the three scanning patterns shown in FIGS. 5A to 5C. In these figures, the points a, b, c, a, b, c from the top on the left side of the screen indicate the starting points of the scanning lines, while the points a, b, c from the top on the left side of the screen. , A, b, c
The points shown in this order indicate the end points of the scanning lines. For example, in the scanning pattern shown in FIG. 5A (this scanning pattern is referred to as a pattern), the left and right starting points a and a are connected as shown in the figure, and the field frequency is 180 Hz and the horizontal deflection frequency is 36 KHz. A pattern is formed such that 200 line scans are performed in one field period. For example, this a pattern is
The horizontal line video signal data R1 and G described in FIG.
3 and B2 are set as the scanning pattern corresponding to the field period in which the frame sequential video signals are supplied to the picture tube side.

Further, the scanning pattern as the b pattern shown in FIG. 5 (b) is a pattern in which the left and right starting points b and the end points b are sequentially scanned, that is,
A pattern is formed by shifting the pattern a shown in FIG. 5A downward by one scanning line. The b pattern corresponds to the field period in which the R2, G1, and B3 video signals described with reference to FIG. 3 are output. Further, the scanning pattern as the c pattern shown in FIG. 5 (c) is further scanned from the b pattern shown in FIG. 5 (b) such that the left and right starting points c and the end points c are sequentially scanned. The pattern is shifted downward by one line, as shown in FIG.
This corresponds to the field period during which the video signal data of the video signal data R3, G2, and B1 described above is output.

Therefore, in the deflection circuit of this embodiment, the video signals (R1 to R3, G1 to G3, B) of horizontal lines for every 9 fields in the complete frame period shown in FIG.
1 to B3), the electron beam is deflected by any one of the scanning patterns of the a pattern, the b pattern, and the c pattern.

FIG. 6 is a block diagram showing the main part of a display device including the deflection circuit of this embodiment. In this figure, 20 shows the video signal conversion circuit shown in FIG. 3, and 30 shows the deflection of this embodiment. In the circuit, 0 (0a) indicates a flat type cathode ray tube (or straight type cathode ray tube), and 8 provided on this cathode ray tube is a deflection yoke. In this configuration, the video signal input to the video signal conversion circuit 20 is deflected in the horizontal line output order as described with reference to FIG. 3, and the flat-type cathode-ray tube 0 is output as a frame sequential video signal corresponding to the present embodiment. Is supplied to. In the video signal conversion circuit 20, for example, in response to the output timing of the horizontal line from the internal memory controller 28,
A pattern switching signal for switching the scanning pattern to any one of the a, b, and c patterns shown in FIG. 5 is output to the deflection circuit 30. Then, the deflection circuit 30 generates a deflection current such that a field screen is formed by a scanning pattern of any one of a, b, and c patterns for each field period on the basis of the pattern switching signal and causes the deflection yoke 8 to generate a deflection current. Supply. The three types of deflection currents corresponding to each of the a, b, and c patterns are obtained by switching the DC component of the vertical deflection current so as to change a predetermined level according to each scanning pattern, while the horizontal deflection current is not changed. be able to.

Specifically, as shown in FIG. 4, in a total of 9 fields within the complete frame period, [R1 → G1 →
[B1] → [R2 → G2 → B2] → [R3 → G3 → B3]
When the horizontal line video signals are output in the order of ([] indicates the pre-frame period), [a → b → c] → [b → c → a] → for each field period accordingly. [C
The direct current component of the vertical deflection current is varied and supplied to the deflection yoke so that a scanning pattern can be obtained in the order of [→ a → b]. By doing so, a complete frame image as described with reference to FIG. 2D can be obtained.

The order of the color screens expressed for each field period, the output order of the positions of the horizontal lines in the video signal shown in FIG. 3, and the order of the a, b, and c scanning patterns accompanying this are R, G, B in one pre-frame
If the scanning pattern is formed such that the field screens are interlaced and the same color does not overlap the same scanning line between the pre-frames, the embodiment is limited to those shown in the drawings. It is not necessary and can be changed. In addition, the above embodiment is based on NTSC, PAL, SE.
The present invention can be applied to the case where so-called normal 2: 1 interlace scanning is performed as seen in a television system such as CAM, and the deflection frequency in the above embodiment is also an example. It can be deflected according to the conditions such as the television system.

[0040]

As described above, according to the present invention, when a color image is displayed on a display device by a field sequential method, the display speed is the same as that of the simultaneous method without increasing the deflection speed for scanning the electron beam. Even if it does, it is possible to significantly reduce the flicker of the image and prevent horizontal stripes from occurring. As a result, even with the frame-sequential type, the power consumption required for deflection is reduced to the same level as with the simultaneous type, and the efficiency is improved. In addition, since it is not necessary for the deflection device such as the deflection yoke and the deflection circuit to be particularly adapted to high frequencies, the deflection device can be configured with the same design and material as the simultaneous system, and the deflection circuit can be configured as the simultaneous system. Since the same thing can be dealt with, the cost can be reduced accordingly. In particular, when a flat type cathode ray tube is used as the picture tube, it is effective to adopt the frame sequential method, which is effective.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing formation of a pre-frame in an embodiment of a display device of the present invention.

FIG. 2 is an explanatory diagram showing formation of a complete frame in this embodiment.

FIG. 3 is a block diagram showing a video signal conversion device in this embodiment.

FIG. 4 is an explanatory diagram showing an output order of video signal data of a horizontal line in a complete frame period.

FIG. 5 is an explanatory diagram showing a scanning pattern in this embodiment.

FIG. 6 is a block diagram showing a main part of a display device including a deflection circuit of this embodiment.

FIG. 7 is a diagram showing structures of flat type and straight type cathode ray tubes.

FIG. 8 is a diagram showing a conventional simultaneous-type and field-sequential-type line scanning.

[Explanation of symbols]

0 Flat type cathode ray tube 0a Straight type cathode ray tube 4 Screen 6 _CT Center of electron lens 7 Display surface 8 Deflection yoke 20 Video signal conversion circuit 24, 25, 26 Field memory 28 Memory controller 30 Deflection circuit

Claims (5)

[Claims] 1. A display device for displaying a color image in a frame sequence in which field screens corresponding to respective colors of R, G, B are sequentially displayed, and a field screen for each of three colors of R, G, B forming one frame. In each display, a line scanning is performed so as not to overlap with a scanning line forming a field screen of another color. 2. The display device according to claim 1, wherein a line scanning pattern is formed so that scanning lines do not overlap between field screens of the same color in three consecutive frames. 3. The display according to claim 1, further comprising line output conversion means for converting the output order of the lines of the original video signal according to the line scanning pattern. apparatus. 4. Corresponding to the line scanning pattern,
4. The display device according to claim 1, further comprising: a DC component varying unit configured to vary a level of a DC component superimposed on the sub deflection current for each field period. . 5. The display device according to claim 1, wherein a flat type picture tube is used as the image receiving device.