JPH11311976A - Drive circuit, display device and display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption at a display operation time by beforehand changing a weight level in a display period of a sub-field based on luminance information of a display part beforehand detected from an image signal and display operating with the display pulse of the weight level. SOLUTION: Analog video signals G, B, R are A/D converted by an A/D converter 1200 answering to 9 bits to be made a digital signal of 8 bits by a γ correction circuit 1201. This signal is stored in a frame memory 15, and the luminance of the signal is counted by a weighting counter 1202. The weighting counter 1202 counts the signals of respective sub-fields with the counters, and shifts a level of a binary code one bit each by an adder answering to the bits, and an adder output becomes a field integration luminance signal. This field integration luminance signal is added by the adder 1203 to obtain a contrast control signal 1204. This contrast control signal 1204 is inputted to a selection circuit 19 to select a ROM of a contrast level from a ROM group for a third electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for displaying an image using subfields.

[0002]

2. Description of the Related Art Conventionally, as a gradation display technique in an image display device using a subfield, for example, in a gas discharge television, Kaji et al .: IEICE Technical Committee on Image Engineering, Material No. IT72-45 (1973- 03) "AC
And a memory panel, for example, Mikoshiba, et al .; Soc. Information display, Digest o
f Technical Papers (1984) pp91-94, “An 8in.-Di
agonal High-Efficacy Townsend-Discharge Memory Pa
nel Color TV Display ”. Regarding the conventional method of lowering the brightness of a cathode ray tube,
HK Color Television Textbook "Upper" S52.10.20pp
139.

[0003]

In the above-mentioned prior art, normally, only a part of the screen has a high luminance, and the number of display pulses used for the light emission operation is small in a part other than the high luminance part. However, since all display pulses of all subfields are applied, there is a disadvantage that power loss increases. Also, the number of display pulses for each subfield is fixed and cannot be changed.

An object of the present invention is to provide a technique capable of improving the above-mentioned disadvantages of the conventional technique and reducing power consumption during a display operation.

[0005]

According to the present invention, there is provided a display device for displaying an image using a sub-field based on luminance information of a display unit detected in advance from an image signal. The weight level in the display period of the field is changed before driving the display unit, and the display operation is performed with the display pulse of the changed weight level.

(2) In a display device for displaying an image using a subfield, based on information detected from an image signal and corresponding to the number of cells of the display unit which is activated according to the luminance signal level. The weight level in the display period of the sub-field is changed before driving the cell with the weight level ratio kept substantially constant, and the cell is driven at the changed weight level to perform the display operation.

(3) In a display device for displaying an image using a subfield, the weight of the display period of the subfield is determined based on information corresponding to the number of cells of the display unit which is activated according to the luminance signal level of the image signal. The level is reduced before driving the cell with the weight level ratio being substantially constant, and the cell is controlled to be driven at the reduced weight level.

(4) In a display device for displaying an image by using a subfield, information corresponding to the number of cells of the display unit which is activated according to the luminance signal level is detected from the image signal, and sub-display is performed based on the detected signal. The weight level of the field display period is changed before driving the cell with the weight level ratio kept substantially constant, and the cell is driven at the changed weight level.

(5) In a display device for displaying an image by using a subfield, information corresponding to the number of cells of the display section which is activated according to the luminance signal level is detected from the image signal for each luminance level. , The weight level in the display period of the subfield is changed before driving the cell with the weight level ratio kept substantially constant, and the cell is driven at the changed weight level.

(6) In a display device for displaying an image by using a subfield, information corresponding to the number of cells of the display section which is activated according to the luminance signal level is detected from the image signal by a plurality of fields for each luminance level. Based on the detection signal, the weight level in the display period of the subfield is changed in advance before driving the cell with the weight level ratio kept substantially constant, and the cell is driven at the changed weight level.

(7) In a driving circuit for driving the display unit using the subfield, information corresponding to the number of cells of the display unit which is activated according to the luminance signal level is detected from the image signal for each luminance level. The weight level in the display period of the sub-field is changed beforehand in a state where the weight level ratio is kept substantially constant based on the signal, and the cell is driven with the changed weight level.

(8) In a drive circuit for driving a display unit using subfields, information corresponding to the luminance signal level and corresponding to the number of cells of the display unit to be activated is detected from the image signal for each luminance level over a plurality of fields. A configuration in which a weighting level in a display period of a subfield is changed beforehand in a state where the weighting level ratio is made substantially constant based on the detection signal and a display pulse for driving a cell with the weighting level after the change is output. And

(9) Information corresponding to the number of cells of the display unit which is activated according to the luminance signal level is detected from the image signal for each luminance level, and the weight level of the display period of the subfield is determined based on the detected signal. A display method in which the cell is driven at the controlled weight level in advance with the weight level ratio being kept substantially constant before driving the cell.

(10) In a display device for displaying an image by using a subfield, detecting means for detecting information corresponding to the number of cells of the display unit to be activated corresponding to the luminance signal level from the image signal for each luminance level. Means for changing the weight level of the display period of the sub-field based on the output signal of the detection means before driving the cell in a state where the weight level ratio is substantially constant, and driving the cell at the changed weight level; And controlling the brightness of the image based on the image signal.

(11) In a display device for displaying an image using a subfield, luminance information of a display section is detected from an image signal for each weight level of a display period of the subfield, and the weight level is determined based on the detection signal. With the ratio kept approximately constant, the display unit is changed before driving the display unit, and the display unit is driven at the weight level after the change to perform the display operation.

(12) In a display device for displaying an image using a subfield, luminance information of a display section is detected from image signals over a plurality of fields for each weight level of a display period of the subfield, and the weight level is determined based on the detection signal. With the weight level ratio kept substantially constant, the display section is changed before driving the display section, and the display section is driven by the changed weight level to perform the display operation.

(13) The luminance information of the display section is detected from the image signal for each weight level in the display period of the subfield, and the display section is driven in a state where the weight level is made substantially constant based on the detection signal. The display method is changed beforehand and the display unit is driven with the changed weight level.

In the above configuration, the display pulse drives a cell of the display unit to emit light or the like, and the weight level of the display period formed by the number of the display pulse or the like defines the luminance level of the image.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

First, the panel configuration and operation of the gas discharge television will be described with reference to FIGS.

FIG. 2 shows an example of a sectional structure of one cell of the gas discharge panel. First electrode (cathode) 22 on substrate 200
0 is made of Ba or a material such as Ni or LaB6. On the other hand, a third electrode (display anode) 24 is provided on the face plate 210.
0 is formed by a technique such as printing. Further, the discharge space (display discharge space 250 and auxiliary discharge space 270) shown in the figure is formed by, for example, stacking a number of perforated spacers, and the second electrode (auxiliary anode) 230 shown in the figure.
Is arranged. When a discharge (display discharge) occurs between the first electrode 220 and the third electrode 240, a gas (a mixed gas such as Xe or Ne-Xe, He-Xe) in the display discharge space 250 is generated.
Then, ultraviolet rays are generated, and the phosphor 260 emits light to perform display. Between the first electrode 220 and the second electrode 230,
A so-called pilot discharge (auxiliary discharge) occurs, and whether or not the auxiliary discharge shifts to a display discharge between the first electrode 220 and the third electrode 240 depends on the presence or absence of a pulse applied to the second electrode 230. . Since this auxiliary discharge does not excite the phosphor 260, it does not affect display light emission.

FIG. 3 is a diagram showing a wiring example of each electrode of the gas discharge panel 301. Each cell 3 of the gas discharge panel 301
The first electrode and the third electrode of No. 02 are connected to the first electrode lead 304 (K1, K2,...) And the third electrode lead 303 in the lateral direction.
(A1, A2,...), And the second electrode is vertically wired to the auxiliary anode lead wire 305 (S1, S2,...). Here, when the panel is vertically divided into two and driven simultaneously, the auxiliary anode electrode lead wire 305 is separated at the center of the panel.

The waveform of the voltage applied to each of these electrodes is shown in FIG.
Shown in In the drawing, Vk is a waveform of a voltage applied to the first electrode lead line, and a pulse 400 is a pulse for addressing one line of the gas discharge panel 301 and is called a first electrode address pulse. The pulse width of the first electrode address pulse 400 is the same as the time width Δ assigned for addressing one line in the example of FIG. For example, when the scanning time of each line is 1H and 240 lines (half the number of lines of a panel driven by two rows simultaneously) in one field are displayed in 8 subfields, Δ ≒ 8 μs.

In the figure, Vs indicates a pulse voltage waveform applied to the second electrode lead, and pulse 410 is a second electrode pulse having a pulse width narrower than that of the first electrode address pulse 400 and behind the time width of Δ. To position. The second electrode pulse 410 may or may not be present depending on the content of the television signal. In the figure, Va indicates the waveform of the voltage applied to the third electrode lead, and for the same line number of the first electrode lead and the third electrode lead, a pulse 420 having a narrow width applied to the third electrode in the figure. Immediately after the first electrode address by the number corresponding to the bit number of the gradation.

Next, the state of discharge between the electrodes will be described with reference to periods I, II and III shown in FIG.

When the address pulse 400 is applied to the first electrode, a discharge occurs between the first electrode and the second electrode during a period I. This is called an auxiliary discharge. This discharge path occurs in the auxiliary discharge space 270 shown in FIG. 2. The wall surface of the space 270 is not coated with a phosphor, and has a structure hidden from the front of the panel. Is less affected.

Next, in the period II in which the pulse 410 is applied to the second electrode, the potential difference between the first electrode and the second electrode is reduced, so that the discharge between the first electrode and the second electrode stops. However, since pilot discharge (auxiliary discharge) is performed in advance in period I, a large number of space charges exist in the vicinity of the first electrode in period II. Therefore, a discharge occurs between the first electrode and the third electrode. The transition of the discharge from the second electrode to the third electrode in this manner is referred to herein as switching. When this switching is performed, a large number of charged particles are generated in a discharge path (display discharge space 250 shown in FIG. 2) between the first electrode and the third electrode.

Next, in a period III of FIG. 4, a pulse 420 having a narrow pulse width is first applied to the third electrode. Above period
Since a large number of charged particles are present in the display discharge space due to the switching of II, the pulse 420 causes a pulse-like discharge between the first electrode and the third electrode. Due to the pulse-like discharge, charged particles are further generated in the display discharge space, and discharge is performed even in the next pulse. As described above, in the period III, the discharge continues while the pulse is continuously applied or until a new potential that stops the discharge is applied to the first electrode. This is called a pulse memory. This discharge excites the phosphor 260 shown in FIG. 2 to emit display light.

When the display is not to emit light, the pulse 410 of the second electrode in FIG. 4 is removed. In this case, switching is not performed and no discharge occurs between the first electrode and the third electrode, so that the number of charged particles in the display discharge space 250 in FIG. 2 is small.
Therefore, no discharge occurs even when the third electrode pulse 420 is applied, and the phosphor 260 in FIG. 2 is not excited.

Therefore, the second electrode pulse 410 serves to control the discharge between the first electrode and the third electrode, and the display brightness can be arbitrarily controlled by the presence or absence of this pulse.

Next, the gradation display method of the gas discharge panel will be described with reference to FIG. 5, taking the case of 8-bit gradation (256 gradations) as an example. FIG. 5 shows one field (NTSC).
FIG. 5 is a diagram illustrating an example of a voltage Vk applied to a first electrode and a voltage Va applied to a third electrode during 1/60 second (s) in the case of a television signal. Eight pulses corresponding to subfields (bits) are applied to the first electrode in one field. Each of them is called an address pulse of b0, b1,..., B7. The pulse applied to the third electrode starts immediately after the application of the address pulse 400 and ends before the next address pulse comes, as shown in FIGS. The respective pulse numbers correspond to b0, b1, b2,..., And if the ratio is 1: 2: 4: 8.
A gradation is formed. Whether or not to discharge by the pulse train of each third electrode is determined by the pulse of the second electrode (4 in FIG. 4) corresponding to the address pulse of b0, b1, b2,.
10) Depending on the presence or absence. If the light emission in the period II in FIG. 4 cannot be neglected, the number of pulses (third electrode pulses) applied to the third electrode is distributed taking into account the luminance due to this.

This brightness level (contrast) is controlled by the number of third electrode pulses in each subfield. Table 1 is 7
The number of third electrode pulses in each subfield showing the contrast of the stage is shown. However, in this example, it is assumed that the brightness due to switching is substantially equal to one third electrode pulse.

[0033]

[Table 1] Table 1

FIG. 1 is a diagram showing an example of a configuration in which γ correction, 1H delay line, peak detection, k-fold amplification, etc. are performed by analog video signal processing.

The G (green), B (blue), and R (red) analog video signals 10 are input to an analog γ (gamma) correction circuit 11. The gamma correction circuit 11 is a circuit for restoring a signal having a gamma characteristic in a television broadcasting station. In a gas discharge television, unlike a cathode ray tube, there is no gamma characteristic. Need to return to linear. This circuit is performed by, for example, a diode broken line approximation circuit.

The γ-corrected signal is input to the peak detection circuit 16 and the 1H delay line 12.

As the peak detection circuit 16, for example, a voltage comparator (comparator) is used as shown in FIG. Although FIG. 6 shows only the G signal (signal after γ correction) 607, the same applies to the B and R signals. The signal 607 after the γ correction is input to the comparator 600 in six stages. The comparison voltage of each comparator is
The levels are set to 1/7, 2/7... 6/7. The output of this comparator is input to a non-retrigable three-input monostable multivibrator 601 and the output pulse width of the multivibrator 601 is set to 1H ($ 63.5).
μs) or more, if the video signal is equal to or more than each comparison level, a High signal is output during the 1H blanking period. Here, the multivibrator resets after the blanking period of H. Each of the comparison signal latch circuits 6
If the clock is set to the blanking period of H at 02, the latch output outputs six signals in the blanking period. This is input to the ROM 604, and here, similar signals of B and R are also output to the ROM 604. The contents of the ROM 604 output seven control signals 606 corresponding to only the maximum value of each comparator and latch output. The seven signals 606 determine the peak level of the signal by 1/7, 2
/ 7,... Output in correspondence with 6/7. The control signal of 606 is input to the control voltage generation circuit 605, whereby the amplification degree of the gain control amplifier 13 is controlled, and the 1H delay line 12 amplifies the analog video signal delayed by 1H.

FIG. 7 shows a configuration example of the control voltage generation circuit of FIG. Reference numeral 700 denotes a voltage generation circuit for controlling the gain of the gain control amplifier 13.
7/2 times, 7/3 times, 7/4 times, 7/5 times, 7/6 times,
The voltage value is set to be one time. Each control voltage is input to the switch circuit 701, and the control of the switch circuit 701 is performed by the control signal 60 of the ROM 604 in FIG.
6 is performed. Table 2 shows the relationship between signal peak level and amplification.
Like

[0039]

[Table 2]

In the case of the configuration shown in FIG. 1, the analog video signal amplified by the k-fold amplifier is converted into an 8-bit A / D converter 14.
After being converted into a digital signal and stored in the frame memory 15. The peak detection circuit 16 stores the degree of amplification for each 1H in the memory 17. Frame memory 15
The digital video signal stored in the gas discharge panel 3
The signal is read out at a time suitable for the display of No. 01, converted into a high voltage signal by the second electrode drive circuit 23 via the shift register 22, and then input to the second electrode lead 305 in FIG.

On the other hand, the signal for driving the first electrode is generated from the ROM 24 for the first electrode, and the first electrode lead (304 in FIG. 3) of the gas discharge panel 301 is passed through the shift register 26 and the first electrode driving circuit 25. Is input to

The signal for driving the third electrode is the third electrode RO.
The ROM is selected for the H signal multiplied by k from the M group 18. FIG. 8 shows a specific circuit example of the selection circuit 19 and the control signal 27 at that time. As shown in Table 1, each of the contrast levels 1 to 7 corresponds to the number of pulses (the number of display pulses) of each subfield applied to the display anode. Table 3 shows the selection of the ROMs 800 of these contrast levels 1 to 7.

[0043]

[Table 3] Table 3

The selection of these ROMs is performed by a data selector (selection circuit) 19 shown in FIG. 8, and the control signal 27 is a signal 27 generated from the memory 17 in FIG. Here, the output signal of the data selector 19 in FIG. 8 is input to the shift register 20 in FIG.
Reading from the electrode ROM is performed in the order of 1H, 2H,. Therefore, the ROM for determining the contrast level of each H is switched in the reading order. The signal input to the shift register 20 in FIG.
The pulse phase and the pulse width are determined via the third electrode lead (303 in FIG. 3).

FIG. 9 is a diagram showing an example of a configuration in which peak detection, 1H memory, and k-fold amplification are realized by a digital circuit.

G (green), B (blue), R
Each of the three primary color (red) analog video signals 10 is converted into a digital signal by the A / D converter 900. In this example,
The A / D converter 900 supports 12 bits. One bit is used for gamma correction, three bits are used for increasing the gradation even in a dark image, and 8 bits are used for the gradation display of a gas discharge television. This is expected, and the total corresponds to 12 bits. Therefore, when a dark image may have the same number of gradations as in the past, the A / D converter may be a 9-bit compatible one.

The A / D-converted 12-bit video signal is converted to an 11-bit signal through a gamma correction circuit 910.
Next, the output signal of the γ correction is input to the 1H memory 912 and the peak detector 911. FIG. 10 shows a circuit example of the peak detector 911.

Output of gamma correction circuit 910 (b0 to b10)
Upper 3 bits (b10, b9, b8) 91 of each color signal
4 is input to the demultiplexer 1000 and converted into a signal of seven stages. Here, there are seven levels of contrast levels in the table, and the maximum amplitude value of the input signal of the A / D converter is set to 7/8 times the maximum amplitude of the A / D converter standard. Each output is input to the counter 1001, and the counter operation is performed during a period in which a 1H video signal exists.
The reset is performed in a blanking period of 1H. If all outputs of each counter are input to an OR circuit 1002,
If at least one 1H digital signal is at that level, it becomes a high signal. Each G at each level,
If the B and R signals are input to the OR circuit 1003, the output signals can detect the maximum values of G, B and R.

These circuit configurations are performed at all levels (seven levels), and the signals are input to the ROM 1004.
The ROM 1004 stores 3 bits corresponding to only the top of each level.
Displays the level of the binary code of the bit. If this is input to the latch circuit 1005 and latched just before the counter 1001 is reset, the output signals A, B and C 1006 output the maximum amplitude of the 1H signal in seven steps (3 bits are required).

In the configuration shown in FIG. 9, the signal delayed by 1H in the 1H memory 912 is multiplied by k times in the k multiplication circuit 913 using the peak detection signal.

FIG. 11 shows a configuration example of the circuit 913.
In the configuration of FIG. 11, the digital signal is multiplied by k using a ROM. The TV signals from b0 to b10 are respectively k = 1, k = 7/6, k = 7/5, 7/4 ... 7
/ 2, 7 are input to the ROM. This value of k corresponds to the contrast level shown in Table 1 above. Each ROM1
The data selector 1108 extracts only one output from the seven ROMs with the maximum luminance signals A, B, and C1006. In this example, the level of the maximum luminance within 1H is 7
The value of k is k = 7 from the lower luminance level,
7/2 ... k is multiplied by k corresponding to 7 / 6,1. The control signals A, B, and C1006 of the luminance level are stored in the memory 17 in correspondence with the numbers H in FIG. Only the upper 8 bits of the signal multiplied by k are stored in the frame memory 15 of FIG. The operation is the same as in the configuration of FIG.

FIG. 12 detects the brightness of the entire screen,
This is an example of a circuit configuration for controlling the contrast of the display screen by adding several fields so that the observer does not dazzle when a bright screen is displayed.

The analog video signals G, B, R shown in FIG.
Is subjected to A / D conversion by an A / D converter 1200 corresponding to 9 bits, and is converted into an 8-bit digital signal by a gamma correction circuit (ROM) 1201. This signal is stored in the frame memory 15, and the luminance counter 1202 counts the luminance of the signal.

As shown in FIG. 13, for example, as shown in FIG. 13, the weighting counter 1202 counts the signal of each subfield (may be some of the higher-order subfields) by the counter 1300 and adds the signal by the adder 1301. , The level of the binary code of the adder 1301 is shifted by one bit corresponding to the bit. This adder output becomes the field integrated luminance signal 1302.

The field integrated luminance signal 1302 is input to a shift register 1400 shown in FIG. Assuming that the clock signal of the shift register is V (vertical scanning signal), the signal is transferred in the shift register for each field. In the example of FIG. 14, the integrated luminance signal of eight fields is added by the adder 1401 to add the contrast control signal 12.
Get 04.

This contrast control signal 1204 corresponds to FIG.
2, and selects a ROM having the contrast level shown in Table 1 from the ROM group of the third electrode.

It should be noted that the present invention is not limited to the scope of the above-described configuration, and the method of controlling the contrast of display from the integrated luminance of the entire screen shown in FIG. 12 and the 1H peak luminance shown in FIG. 1 or FIG. This also includes a configuration in which a method for controlling the contrast level from the same time is performed simultaneously.

Although the above description has been made in the case of a gas discharge panel, the present invention is not limited to this, and the present invention relates to other display techniques for controlling gradation and luminance by the number of pulses and the display period width. Including cases.

[0059]

According to the present invention, power consumption can be reduced. Also, since the number of gradations can be increased even on dark screens,
Image quality can be improved. On a bright screen, the brightness can be reduced so that the observer does not dazzle.

[Brief description of the drawings]

FIG. 1 is a configuration example diagram for explaining the present invention.

FIG. 2 is an example of a cell cross section in the case of a gas discharge panel.

FIG. 3 is an example of electrode wiring of a gas discharge panel.

FIG. 4 is an example of a waveform of a voltage applied to each electrode of the gas discharge panel.

FIG. 5 is an explanatory diagram of gray scale display in a memory type gas discharge panel.

FIG. 6 is a diagram illustrating an example of a signal peak detection circuit.

FIG. 7 is an example diagram of a control voltage generation circuit.

FIG. 8 is a diagram showing an example of a third electrode ROM group and a selection circuit.

FIG. 9 is a configuration example diagram for explaining the present invention.

FIG. 10 is a diagram illustrating a configuration example of a circuit that digitally detects a peak of a signal.

FIG. 11 is a diagram illustrating a configuration example of a circuit that multiplies a digital signal by k times.

FIG. 12 is a diagram illustrating a configuration example of a device that controls contrast based on average luminance of a screen.

FIG. 13 is a diagram illustrating a configuration example of a weighting counter.

FIG. 14 is a diagram illustrating a configuration example of a circuit that outputs an average luminance over several fields.

[Explanation of symbols]

12 1H delay circuit, 13 Gain control amplifier, 16 Peak detection circuit, 18 ROM for third electrode
Group, 19: selection circuit, 301: gas discharge panel.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Shinichi Shinada, Inventor 1-280, Higashi-Koigabo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. Inside the Central Research Laboratory

Claims (13)

[Claims] 1. A display device for displaying an image using a subfield, wherein a weight level of a display period of the subfield is previously changed based on luminance information of the display unit detected from an image signal before driving the display unit. A display operation performed by a display pulse having a weight level. 2. A display device for displaying an image by using a subfield, wherein information corresponding to the luminance signal level of the image signal and corresponding to the number of cells of the display unit to be activated is detected from the image signal. In the state where the weight level of the display period of the subfield is changed beforehand in a state where the weight level ratio is kept substantially constant, the cell is driven at the changed weight level and the display operation is performed. Display device. 3. A display device for displaying an image by using a subfield, wherein a weight level of a display period of the subfield is based on information corresponding to the number of cells of the display unit to be activated corresponding to the luminance signal level of the image signal. Wherein the weight level ratio is controlled to be reduced before driving the cell with the weight level ratio being substantially constant, and the cell is driven at the reduced weight level. 4. A display device for displaying an image using a subfield, wherein information corresponding to the luminance signal level and the number of cells of the display unit to be activated is detected from the image signal, and a subfield is detected based on the detected signal. Wherein the weight level during the display period is changed before driving the cell while the weight level ratio is kept substantially constant, and the cell is driven at the changed weight level. 5. A display device for displaying an image using a subfield, wherein information corresponding to the number of cells of the display unit which is activated according to the luminance signal level is detected from the image signal for each luminance level, and the detected signal is detected. A display device characterized in that a weight level in a display period of a subfield is changed before driving a cell in a state where the weight level ratio is kept substantially constant, and a cell is driven at the changed weight level. 6. A display device for displaying an image using a subfield, wherein information corresponding to the luminance signal level and corresponding to the number of cells of the display section to be activated is detected for each luminance level over a plurality of fields from the image signal. The weight level of the display period of the sub-field is changed beforehand in a state where the weight level ratio is made substantially constant based on the detection signal, and the cell is driven with the changed weight level. Display device. 7. A driving circuit for driving a display unit using a subfield, wherein information corresponding to the luminance signal level and corresponding to the number of cells of the display unit to be activated is detected for each luminance level from the image signal. A driving circuit which changes a weight level in a display period of a subfield in advance in a state where the weight level ratio is made substantially constant before driving the cell and drives the cell at the changed weight level. 8. A drive circuit for driving a display unit using a subfield, wherein information corresponding to the luminance signal level and corresponding to the number of cells of the display unit to be activated is detected from the image signal for each luminance level over a plurality of fields. Outputting a display pulse for driving a cell at the changed weight level in advance by changing the weight level of the display period of the subfield based on the detection signal before driving the cell with the weight level ratio being substantially constant. Characteristic drive circuit. 9. Information corresponding to the number of cells of the display unit which is activated according to the luminance signal level is detected for each luminance level from the image signal, and the weight level of the display period of the subfield is determined based on the detected signal. A display method characterized in that the weight level ratio is kept substantially constant before the cell is driven, and the cell is driven at the controlled weight level. 10. A display device for displaying an image using a sub-field, comprising: detecting means for detecting, from the image signal, information corresponding to the number of cells of the display unit corresponding to the luminance signal level, for each luminance level; Means for changing the weight level in the display period of the subfield based on the output signal of the detection means before driving the cell in a state where the weight level ratio is kept substantially constant, and driving the cell with the changed weight level; A display device, comprising: controlling brightness of an image based on the image signal. 11. A display device for displaying an image using a subfield, wherein luminance information of a display section is detected from an image signal for each weight level of a display period of the subfield, and the weight level is determined based on the detection signal. A display device which changes in advance before driving the display unit while driving the display unit at a substantially constant state and drives the display unit with the changed weight level to perform a display operation. 12. A display device for displaying an image using a subfield, wherein luminance information of a display section is detected from image signals over a plurality of fields for each weight level of a display period of the subfield, and the weight level is determined based on the detection signal. A display device characterized in that the weight level ratio is made substantially constant before driving the display unit, and the display unit is driven with the changed weight level to perform a display operation. 13. A method of detecting luminance information of a display unit from an image signal for each weight level in a display period of a subfield, and adjusting the weight level based on the detection signal before driving the display unit with the weight level ratio being substantially constant. Wherein the display unit is driven with the changed weight level in advance.