JPH02197893A - display device - Google Patents

Abstract

PURPOSE:To prevent the deterioration in image quality by a flash by controlling the dots of the same density in such a manner that the timing thereof varies with each line without being thinned out at the same timing on the entire screen. CONSTITUTION:A raster counter section 76 of m-ary constitution and an adder circuit section 77 which adds the outputs of the raster counter section 76 and a field counter section 74 are added, by which the thinning-out timing of data '1' to express various densities, i.e. the timing to generate data '0' is so controlled as to be shifted at every one raster (every one line). The timing to thin-out the dots of the same density by the adjacent rasters is shifted by using the raster counter section 76 of the octal constitution and changing the field to be thinned-out at every one raster, by which the adjacent rasters are so controlled as not to attain '0' in the same field as far as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is a display device equipped with a monochrome LCD, CRT, etc. used in personal computers, word processors, hand belt computers, and various other data processing devices. In particular, this invention relates to a display device that can provide high-quality display by suppressing flickering that occurs on the screen when displaying on a monochrome LCD, CRT, etc. using software compatible with color display. .

At present, LCD display devices are monochrome and are widely used in laptops, personal computers, and the like.

This laptop-shaped personal computer has functions equivalent to those of conventional personal computers.

However, the display devices are different, and in the conventional case, CR
1 display device, and a color display is adopted. Therefore, display control software is naturally compatible with color.

In other words, laptop-type personal computers use monochrome LCD display devices, but
This means that the display control software is compatible with color display.

Therefore, in the case of an LCD display device, it is necessary to express the gradation of an image by gradation display corresponding to color display, so-called display gradation.

Conventional gradation expression techniques for expressing such dot signals based on color signals as monochrome dots are broadly classified into two types: a field thinning method and a pulse control method.

Of these, in the case of the latter pulse control method, gradations are expressed by controlling pulses.

A special driver IC is required.

Therefore, the cost of the entire display device becomes extremely high, and it is currently extremely difficult to use it in relatively inexpensive laptop-type personal computers and the like from a cost standpoint.

For these reasons, the former field thinning method is generally used.

This field thinning method uses a field as one unit and thins out "1" data in dot display every m fields according to the number of gradations, in order to express shading corresponding to the density of color display. be.

Here, the relationship between a field serving as one unit and its raster will be briefly described.

FIG. 7 is a diagram illustrating the relationship between one field and raster in a normal LCD display device. In drawing 0, 0 to n indicate raster.

As shown in FIG. 7, the rasters are 0, 1, 2, . . . on the LCD screen. For example, in the case of an LCD with width x height = 640 x 200 (dots), n = 199.

Display data is LC synchronized with these rasters 0 to n.
Sent to the D display device, 1rj of Lasku 〇~n! One screen displayed by scanning i is called one field.

Normally, LCDs are scanned at a speed of 50 to 70, so the scanning time for one field (one screen) is 11
50 to 1/70 (sec).

In the case of a field thinning method in which color signals (R, G, B) are displayed in monochrome at three gradations, one dot of corresponding shading is displayed by scanning eight fields.

Therefore, in this case, the time required to display one cycle of one dot is 8150~8/70
(sec).

In particular, the thinning process performed for one field shown in FIG. 7 during monochrome gradation display compatible with color display,
The so-called field thinning method will be explained.

FIG. 8 is a time chart for explaining the conventional field thinning method.

FIG. 8 shows a field thinning method for 8-gradation data.

The bottom line shows the count value of a field counter (see FIG. 11 below). In the case of 8 gradations in this embodiment, this count value is incremented for each field and indicates a numerical value from 0 to 7 so that one cycle of light and shade can be expressed in eight fields.

Therefore, in the case of this 8-gradation data, an octal-configured field counter is used, and for each field, 2
The color signal (R.

Dots corresponding to G and B) are displayed.

As shown in the waveform shown in the second row from the top of FIG. 8, the darkest data, that is, the white color of the color display, is
, G, B) = "1" is output in all fields like a waveform of (1, 1, 1).

On the other hand, for the lightest data, that is, the black color shown in the bottom row of Figure 8, (R, G, B) = (0, O, O
), outputs tz O'' in all fields.

For example, in the case of the second darkest data, that is, the yellow shown in the third row from the top of Figure 8, (R, G
, B) = (1, 1, O), 0'' is output only once out of 8 fields.

Also, the third densest data, that is, the 4th from the top of Figure 8.
In the case of purple shown in the row, CR, G.

B) = As shown in the waveform (1, 0, 1), PA0'' is output only twice out of 8 fields.

The same goes for other color signals (R, G, B).
Corresponding to the decrease in concentration, as shown in FIG.

The number of times to output '0' among the 8 fields has been increased,
As a result, the number of data "1"s that become bright spots is reduced.

In the case of this field thinning method, if we look at the dots that are intermediate in shading from yellow to blue, the number of times they are thinned out differs, but in common they are "0" and "
1" is repeated. In other words, it is in a flashing state.

Such a flash is not very noticeable when it is just one dot, but since all dots forming the same shade flash in the same periodic relationship, the entire surface appears to be flickering on both sides.

Usually when forming patterns such as letters or lines.

Since several or more dots of the same density are arranged in succession, such flickering on the screen has a non-negligible adverse effect on the image quality.

FIG. 9 is a time chart showing an example of an output waveform of a conventional thinning circuit in a conventional LCD display device when the color signals (R, G, B) are (1, 1, O).

In this FIG. 9, color signals (R, G, B) = (1, 1
, O), that is, the case shown in yellow in FIG.

This 91st! As is clear from 1, the dots constituting the same shade, that is, the field counter is 0 to 7"
“O” indicated by a raster counter for each field of
~ “8” . . . , all lines are changed at the same cycle.

In other words, for all rasters (lines), only when the field counter is "0", the data is "0" and becomes a non-bright spot, and when the other values are "1 to 7", the data is "0".
1", it becomes a bright spot. Note that this raster counter is a raster counter for scanning the screen, and is shown for convenience in order to clarify the correspondence with FIG. 2, which will be described later.

In this way, in the conventional thinning method, the thinning process is performed field by field, so in the case of the color signal (R, G, B) = (1,1°O) shown in Fig. 9, the field counter When is "0''', all rasters (all dot lines) are thinned out in common, and no data is output (strictly speaking, data of 00'' is output).

Such a state, that is, a state in which the thinned out dots are synchronized, is as shown in FIG.
G, B) = (1, 1, 1) and (R.

In cases other than G, B) = (0, O, O), the dots are commonly generated in all density dots.

Therefore, the entire screen flashes and appears flickering.

In the case of the conventional field thinning method, there is a problem in that the flickering caused by the above reasons causes a screen that is difficult to see with a degraded image quality, which also has a negative effect on operational efficiency.

FIG. 10 is a functional block diagram showing an example of the main configuration of a display controller for a conventional LCD display device. In the drawing, 1 is an oscillation section, 2 is a division section, 3 is a control signal generation section, 4 is an address counter, 5 is a RAM address selection section, 6 is a screen RAM, 6R is for the red color,
6G is for green color, 6B is for blue color, 7 is a data converter, and 8 is a transceiver.

The display controller shown in FIG. 10 sends a control signal and display data to one display device at a constant cycle preset for each display device.

The basic clock signal is generated by the oscillation section 1 and the division section 2.

The control signal generating section 3 generates a control signal for the display device based on the basic clock signal output from the branching section 2.

Further, in order to sequentially send display data, an address for the screen RAM 6 is generated by the address counter 4.

The CPU that controls the entire system needs to access this screen RAM 6 when changing or checking the displayed content.

Normally, RA is used to send display data to a display device at regular intervals, regardless of the operation of the CPU.
M6 is being accessed.

Therefore, in order to ensure that the reading operation of display data is not affected by CPU access and that the contents of the memory are not destroyed, access to screen RAM 6 for LCD display and data transfer between CPU and RAM 6 are necessary. A time-sharing system is used to avoid conflicts with other classes.

Therefore, when the CPU attempts to access the screen RAM 6, it is necessary to make the CPU wait temporarily.

For this purpose, the RAM address selection section 5 generates a wait signal to the CPU.

The RAM address selection section 5 also switches between the address from the CPU and the address from the address counter 4, and outputs it to the address bus of the screen RAM 6.

When the double-sided RAM 6 is accessed using the address from the address counter 4, the data conversion unit 7 converts the data output from the screen RAM 6 into a data format required by the LCD.

The transceiver 8 functions to prevent the display data bus from colliding with the CPU data bus.

The above is an outline of the operation of the conventional display controller shown in FIG. 10.

The conversion process of gradation display using the field thinning method is performed by the data converter 7 shown in FIG.

The following FIG. 11 is a functional block diagram showing an example of the detailed configuration of the data converter 7 shown in FIG. 10. Reference numbers in the drawing are the same as those in FIG. 10, and
71R, 71G, and 71B are latch circuits for red, green, and blue, respectively. 72R, 72G, and 72B are P/S (parallel/serial) converters for red, green, and blue, respectively. 73 is a thinning circuit. 74 is a field counter section, 75 is an S/P (serial/parallel) converter, and 9 is an LCD display section.

In a conventional LCD display device, the data conversion section 7 has a configuration as shown in FIG.

The display data output from the red screen RAM 6R shown in FIG. 10 is latched into the red latch circuit 71R.

The display data latched by the latch circuit 71R is converted from parallel data to serial data by the next-stage red P/S converter 72R.

Similarly, the green latch circuit 71G latches display data output from the green screen RAM 6G,
The parallel data is converted into serial data by the next-stage green P/S converter 72G.

Furthermore, the blue latch circuit 71B is connected to the blue screen R
Display data output from AM6B is latched. Then, the blue P/S converter 72B converts the parallel data into serial data.

In the case of a color CRT, these red.

Serial data of one bit each for blue and green is output to the CRT and displayed in color on the screen.

However, in the case of a monochrome LCD, the next thinning circuit section 73 converts the data into thinned data as described in connection with FIG. 8 above.

This thinning circuit section 73 changes the number of data "1" of the signal of the dot in units of m fields in accordance with the signals of three colors constituting one dot of color display, and outputs a dot signal corresponding to the light and shade. It has the function of

In the conventional field thinning method, in order to thin out each field, the field counter section 74 synchronizes and performs the thinning process.This field counter section 74 takes 8 fields as one cycle.
1 dot floor! ! This is a counter for expressing l (concentration).

In addition, in the case of an LCD display device, data is normally input in parallel, so the serially input data is converted into parallel data via the next stage S/P converter 75, and the data is displayed on the next stage LCD. Output to display section 9.

As already mentioned, in the conventional field thinning method, thinning processing is performed on a field-by-field basis, so for example, as shown in FIG. 9, color signals (R, G, B) =
In the case of (1, 1, O), when the value of the field counter section 74 is "0".

No data will be output for any raster (any line).

Therefore, dots of the same density flash, and the entire screen appears to flicker. There was this inconvenience.

In this invention, by simply adding a circuit means of a simple configuration to a display device using a conventional field thinning method, flickering can be suppressed, and the image quality can be improved by flash compared to a conventional field thinning method. It is an object of the present invention to provide a field thinning type display device with high image quality at a low cost by solving the inconvenience that operation efficiency decreases due to deterioration.

In this invention, the number of data "1" of the signal of the dot is changed in units of m fields in correspondence with the signals of three colors constituting one dot of a color display, thereby producing a dot signal corresponding to the light and shade. In a conventional display device using a field thinning method, which is equipped with an output thinning circuit and a field counter with an m-ary configuration, and performs gradation display by controlling data thinning for each field, the raster counter with an m-ary configuration and , adding means for changing the output timing of thinned data "0" according to the input of the count value of the raster counter, and by inputting the output of the adding means to the thinning circuit, dots of the same density are thinned out. The timing is controlled differently for each raster.

In summary, dots of the same density are not thinned out at the same timing on the entire screen (one field), but the timing is controlled to differ from line to line.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the display device of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a functional block diagram showing an embodiment of the main configuration of a data conversion section of a display device according to the present invention. Reference numerals in the drawing are the same as those in FIG.
Reference numeral 6 indicates a raster counter section, and 77 indicates an addition circuit section.

In the display device of the present invention shown in FIG.
The only difference is that a raster counter section 76 and an addition circuit section 77 are added to the conventional data conversion section 7 shown in FIG.

In the display device of the present invention shown in FIG. 1, by adding a raster counter section 76 having an m-adic configuration and an addition circuit section 77 that adds the outputs of the raster counter section 76 and the field counter section 74, Control is performed to shift the thinning timing of data "1" representing shading, or in other words, the timing at which data "0" is generated, for each raster (for each line).

The raster counter section 76 has the same 8
When expressing the gradation of gradation, it is an octal-configured counter like the field counter section 74.

In the first embodiment described below, a raster counter section 76 with an octal configuration is used, and by changing the field to be thinned out for each raster, dots of the same density are thinned out in adjacent rasters. By shifting the timing, control is performed so that adjacent rasters in the same field do not become "O" as much as possible.

FIG. 2 shows a color signal (
3 is a time chart showing an example of an output waveform of a thinning circuit when R, G, B) are (1, 1, O).

The output waveform shown in FIG.
In the case of a signal similar to the color signal shown in the figure, that is, yellow shown in the third row from the top of FIG. 8, the color signal (R) is the second darkest data.

G, B) = concentration signal corresponding to (1, 1, O).

Similarly to FIG. 9, there is a case where data is generated as '0' only once every eight fields.

The count value of the raster counter unit 76 (the raster counter shown on the left side of FIG. 2) increases sequentially from "0" to "7".
The timing at which data "'0" is generated (the field to be output) changes until it becomes "0".

The waveforms shown by raster counters 0 to 7 in FIG. be done.

The following FIG. 3 shows an example of the configuration of a circuit for generating the output shown in FIG. FIG. 2 is a functional block diagram illustrating an example. In the drawings, FIELD O to FIELD 2 indicate field count outputs, and RASO-RAS2 indicates raster count outputs.

In this example, the color signals (R, G, B) are (1,1
, O), and if the 3 bits input to the thinning circuit section 73 are (C2, C1, Go), then (C2, C
When I, co) = (0, o, O), the thinning result is “
OIF, otherwise the thinning result is II
An example in which I II is explained.

In the block diagram of FIG. 11, which generates a thinning output like the time chart of FIG. 9, the input to the thinning circuit section 73 is the output of the field counter section 74, so the raster count output Regardless of the value of
When the output of the field counter section 74 is "0", the result of one thinning is "O".

In the block diagram of FIG. 11, which generates the thinned out output as shown in the time chart of FIG. 9 above.

The input to the thinning circuit section 73 is the field counter section 7
Since the output is 4, the output of the field counter section 74 is 10, regardless of the value of the raster count output.
”, the 1-thinning result ′ becomes “0”.

On the other hand, in the display device of the present invention, as shown in FIG. 3, the field count output PIF! of the field counter section 74! , LD O-FIELD 2 and the raster count output RASO of the raster counter section 76
-RAS2 are input to the addition circuit section 77 and added.

Then, the addition result from the adder circuit 77 is input to the 1 decimation circuit 73, so the reason why the output of the decimation circuit 73 becomes "0" is due to (the value of the raster count output)
+ (field count output) is “O” or “8”
It's time.

Therefore, from the thinning circuit section 73 in FIG. 1, the raster counters O to 7 in FIG. A thinned-out output such as O (second to bottom line in FIG. 2) is generated.

As a result, as is clear from comparing this Figure 2 with the previous Figure 9, in the case of Figure 2, the timing at which data is set to "0" is a different raster for each field. .

For example, when the field counter is "Orp", the raster counter is "Ojl line (raster) data is uO".

The data of the adjacent line (raster) whose raster counter is Kl l 11 is 11 l IF.

Similarly, when the field counter is # l lj,
On the line where the raster counter is “7”, the data is “
Become Opt.

The lines on both sides, that is, the raster counter is 16
” and the raster of JJ O71, the data is It 1 #
be made into

In this way, by changing the timing of thinning out dots corresponding to the same density for each raster, dots with the same density repeat changes between bright spots and non-bright spots at the same period on the entire screen, unlike conventional methods. This eliminates the flash phenomenon caused by flipping the screen back and forth, resulting in a flicker-free screen.

Therefore, flickering in conventional display devices is prevented, and a high-quality screen can be obtained.

However, in the case of this first embodiment, there remains the problem that when color signals of the same gradation level are output over a wide area, the display screen appears to be flowing.

In addition, in the time chart of FIG. 2, the color signals (R,
Although the case of G, B) = (1, 1, 0) was shown,
The same applies to other color signals (R, G, B).

Furthermore, in the case of the time chart of FIG. 2, the case where the timing is shifted by one unit for each adjacent raster (line) (the case where it is changed for each field) has been described.

However, instead of shifting the timing at which the output of the thinning circuit section 73 reaches 0# by one unit, it is also possible to shift it randomly, which will be described in the next section as a second embodiment.

Loss of JJL Next, as a second embodiment, a case will be described in which the timing at which the output of the thinning circuit section 73 becomes "0" is randomly shifted for each adjacent raster (line).

To summarize, in the adder circuit section 77 of FIG. 1, the count output of the field counter section 74 is adjusted.

Instead of adding the value of the count output of the raster counter section 76, the addition circuit section 77 stores addition values randomly arranged for each adjacent raster (line) (in the case of 8 gradations, from 0 to 7). The added value may be stored without regard to the order of the numerical values) and accessed by the outputs of the field counter section 74 and raster counter section 76.

For example, the first line is the added value Jlj, and the second line is “5”.
”, the third line is “3”, the fourth line is “6”, and so on. Random addition values consisting of eight types or less values corresponding to rasters 1 to 8 (lines) are set.

Then, the addition result of these values is converted into a color signal (R
, G, B) are serially inputted to a thinning circuit section 73 to control the generation point of thinned data (timing at which data "0" is output) for each field.

Furthermore, as another method, it is also possible to change the input signal to the adder circuit section 77.

The following description will focus on the case where the count output from the raster counter section is inputted to the adder circuit section 77 with the LSB and MSB reversed.

FIG. 4 is a time chart showing an example of the output waveform of the thinning circuit section 73 when the color signals (R, G, B) are (1, 1°0) in the second embodiment of the display device of the present invention. It is a chart.

The output waveform shown in FIG.
The color signal shown in the figure and the second example as a first example.
In the case of a signal similar to the color signal shown in the figure, that is, yellow shown in the third row from the top of Figure 8, the second darkest data is the color signal (R, G, B) = (1, 1 , O)
is the concentration signal corresponding to .

Then, as in Figure 9 and Figure 2, 1 field is set every 8 fields.
This is a case where the data is generated as "0"' only once, and the value of the count output of the raster counter section 76 (the value of the raster counter shown on the left side of FIG. 4) increases sequentially from "0" until II 713. Until then, the timing of generation of data 110'' (field to be output) changes randomly.

FIG. 5 is a functional block diagram showing one embodiment of the circuit configuration for generating the output shown in FIG.
' indicates the raster counter section.

The output waveforms shown by the raster counters O to 7 in FIG. It is generated from the circuit section 73.

In the case of this second embodiment, the raster counter section 76
The output of ' is different from that in FIG. 3 showing the first embodiment,
The LSB and MSB are reversed.

FIG. 6 is a diagram showing the relationship between the value of the raster count output, the value obtained by reversing the LSB and MSB of the raster count value, and the value of the field count output.

As shown in Fig. 6, when (the value obtained by reversing the LSB and MSB of the raster count output value) + (the value of the field count output) is "0" or "8", the raster count output value Corresponding to O to 7, the value of the field count output at which the output of the thinning circuit section 73 becomes 0'' changes as 0, 4, 6 degrees, 2.7, 3, 5, 1.

The addition result added by the adding circuit section 77 in FIG. 5, that is, the addition result of the value obtained by reversing the LSB and MSB of the raster count output value in FIG. 6 and the field count value is the first The signal is input to the thinning circuit section 73 in the figure. That is, the signals input to the adder circuit section 77 are replaced.

The output of the thinning circuit section 73 becomes 0'' because the sum of the value obtained by reversing the LSB and MSB of the raster count output value shown in the middle column of FIG. 6 and the field count value is ``0''.
This is when it becomes 0" or 8".

Therefore, as shown in FIG. 4, the phase of thinning is not shifted by one unit for each raster, but is shifted randomly.

Therefore, the flow of the display screen that occurs in the case of the output shown in FIG. 2 showing the first embodiment is also prevented.

Also in the case of the second embodiment, dots with a constant density (for example, dots with a constant density corresponding to yellow, red, etc.)
At least adjacent rasters are thinned out at different times, so the entire screen (one field)
are not flushed synchronously.

Therefore, in this case as well, as in the first embodiment, flickering is suppressed and high-quality gradation display is obtained, and color signals with the same gradation level are output over a wide area. However, the problem that the display screen appears to be flowing does not occur.

Although the above first and second embodiments have mainly been described with reference to the case of an LCD display device, it goes without saying that the present invention can also be easily implemented in the case of a CRT.

Moreover, according to the display device of the present invention, even in the first embodiment, the second embodiment
In this embodiment as well, it is possible to realize an easy-to-read screen gradation display without flickering by using a display device using a field thinning method, without using an expensive pulse control type LCD or CRT.

Furthermore, in the second embodiment, even if color signals of the same gradation level are output over a wide area, the problem that the display screen appears to be flowing does not occur.

Therefore, it is especially important for data processing devices such as laptop personal computers, which are equipped with a monochrome LCD or CRT, display device that uses control software that supports color display, and whose main unit price is relatively low. An excellent effect can be obtained in that a display device that is suitable, low cost, and provides high quality display can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing an embodiment of the main configuration of a data conversion section of a display device of the present invention. FIG. 2 shows a color signal (
A time chart showing an example of the output waveform of the thinning circuit when R, G, B) is (1, 1, 0), FIG. 3 is an example of the configuration of a circuit for generating the output shown in FIG. Regarding the detailed configurations of the field counter section 74, raster counter section 76, and addition circuit section 77 shown in FIG.
FIG. 4 is a functional block diagram illustrating one embodiment of the present invention, which shows a thinning circuit in a second embodiment of the display device of the present invention when the color signals (R, G, B) are (1, 1°0). 5 is a functional block diagram showing an example of the circuit configuration for generating the output shown in FIG. 4; FIG. 6 is a time chart showing an example of the output waveform of the section 73; Figure 7 shows the relationship between the value, the value obtained by reversing the LSB and MSB of the raster count value, and the value of the field count output.
FIG. 3 is a diagram illustrating the relationship between one field and raster in a CD display device. FIG. 8 is a time chart for explaining the conventional field thinning method. FIG. 9 is a time chart for explaining the conventional field thinning method. A time chart showing an example of the output waveform of a conventional thinning circuit; FIG. 10 is a functional block diagram showing an example of the main part configuration of a display controller of a conventional LCD display device; FIG. FIG. 2 is a functional block diagram showing an example of the detailed configuration of the data conversion unit 7 shown in FIG. In the drawing, 6 is the screen RAM, 6R is the red one, 6G is the green one, 6B is the blue one, and 7 is the data converter.
71R, 71G, and 71B are latch circuits for red, green, and blue, respectively; 72R972G, and 72B are P/S converters for red, green, and blue, respectively; 73 is a thinning circuit section; and 74 is a field counter section. , 75 is an S/P converter, 76 and 76' are raster counter sections, 77 is an addition circuit section, and 9 is an LCD display section. talent map

Claims (1)

[Claims] Corresponding to signals of three colors constituting one dot of a color display, the number of data "1" of the signal of the dot is changed in units of m fields, and a dot signal corresponding to light and shade is outputted. Equipped with a thinning circuit and a field counter with an m-adic configuration,
A display device using a field thinning method that performs gradation display by controlling data thinning on a field-by-field basis includes a raster counter having an m-ary configuration, and data thinned out by inputting the count value of the raster counter. adding means for changing the output timing of "0", and by inputting the output of the adding means to the thinning circuit, the thinning timing of dots of the same density is controlled differently for each raster. display device.