JP2000148074A - Matrix type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a matrix type display device which can be inversely gamma-corrected while suppressing decrease in peak brightness by improving the driving method. SOLUTION: On a display panel 10, plural rows and columns of light emitting elements are arranged in a matrix form. A PWM circuit 4 and a shift register 7 supply the display panel 10 with a driving waveform corresponding to an image data to be displayed with each light emitting element, and drive each light emitting element. The driving waveform is ramped so that each light emitting element has an inverse gamma characteristic, by cutting off a ramping voltage, which is generated by a waveform generating circuit 8 and partially has a flat voltage, by the pulse from the PWM circuit 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matrix for a display device using an electron emission source such as a cold cathode electron emission device (so-called field emission display device) and an electroluminescence (hereinafter abbreviated as EL) display device. The present invention relates to a type display device.

[0002]

2. Description of the Related Art As a matrix type display device, a field emission display device and an EL display device using a cold cathode electron-emitting device are known. FIG. 8 is a block diagram showing a conventional matrix type display device of this kind. 8, a display panel 10 is a display panel using, for example, cold cathode electron-emitting devices. As shown in FIG. 9, as an example, a plurality of row wirings connected to scan electrodes S1 to Sm;
The cells 10s forming the pixels are arranged in a matrix by a plurality of column wirings connected to the data electrodes D1 to Dn. The cell 10s includes an electron-emitting device that is an electron-emitting source and a phosphor that receives electron irradiation from the electron-emitting device.

A video signal input to a terminal 1 is written to a shift register 2. 1 in shift register 2
After the data for the row is written, the data is latched by the latch circuit 3. The data output from the latch circuit 3 is
The signal is input to a pulse width modulation (PWM) circuit 4. The PWM circuit 4 switches the switch Sd1 with a pulse corresponding to the magnitude of the data.
To Sdn. Switches Sd1 to Sdn are PW
It is turned on when the pulse input from the M circuit 4 is high, and a constant voltage + is applied to the data electrodes D1 to Dn of the display panel 10.
Vd.

On the other hand, the synchronization signal input to the terminal 5 is input to the timing control circuit 6. The timing control circuit 6 supplies a shift clock to the shift register 2 and a latch clock to the latch circuit 3. The timing control circuit 6 also supplies a one-line-width scan pulse to the shift register 7. The shift register 7 controls the switches Ss1 to Ssm with the pulse. The switches are turned on when the scan pulse input from the shift register 7 is high, and the scan electrodes S1 to Sm of the display panel 10 are turned on.
Is supplied with a constant voltage −Vs.

Further, the operation when driving the matrix type display device shown in FIG. 8 will be described in detail. As described above, the scan pulse is sequentially applied to the scan electrodes S1 to Sm of the display panel 10 by the shift register 7. Further, a pulse whose pulse width (PWM) is modulated by the PWM circuit 4 in accordance with data corresponding to the selected line is applied to the data electrodes D1 to Dn of the display panel 10. That is, a voltage is applied to the data electrode Dj for the data in the i-th row and the j-th column while the scanning electrode Si is selected. The intensity (gradation) of the light emission depends on the data electrode D1.
ＤDn is represented by the application time (pulse width) of the pulse applied to Dn.

FIGS. 10A to 10C are waveform diagrams showing the operation when displaying the j-th column as an example. FIGS. 10A to 10C show scan pulses applied to the scan electrodes, and FIG. 10D shows the scan pulses applied to the data electrodes. Pulses to be applied are shown in (E) to (G) in the element (cell 10).
The voltage applied to s) is shown. Here, the number of bits of the video signal is represented as 8 bits, perfect black is represented as 0, complete white is represented as 255, i-th row and j-column are black (0),
The (i + 1) th row and jth column are gray (128), and the (i + 2) th row and jth column are white (255). One horizontal scanning period is constituted by 255 unit times. The unit time is P
This is the clock cycle of the WM circuit 4, and the unit time is represented by T. The gradation expression is performed by changing the pulse width of the pulse applied to the data electrodes D1 to Dn from 0T to 255T. Actually, one horizontal scanning period is 2
The unit time may be 55 T or more.

As shown in FIG. 10, during the horizontal scanning period of the i-th row, the voltage -Vs is applied to the scanning electrodes Si of the i-th row, and no voltage is applied to the other scanning electrodes.
At this time, since the signal in the i-th row and the j-th column is 0, the data electrode Dj in the j-th column is always at the 0 potential. When the horizontal scanning period for the i-th row ends, the process proceeds to the horizontal scanning period for the (i + 1) -th row.

In the horizontal scanning period of the (i + 1) th row, i +
A voltage -Vs is applied to one row of scan electrodes S (i + 1), and no voltage is applied to the other scan electrodes. At this time, since the signal of the (i + 1) -th row and the j-th column is 128, the voltage + Vd is applied to the data electrode Dj of the j-th column only for about half (128T) of the horizontal scanning period (255T). It becomes 0 potential. When the horizontal scanning period of the (i + 1) -th row ends, the process proceeds to the horizontal scanning period of the (i + 2) -th row.

In the horizontal scanning period of the i + 2 row, i +
The voltage -Vs is applied to the scanning electrodes S (i + 2) in two rows, and no voltage is applied to the other scanning electrodes. At this time, since the signal of the (i + 2) th row and the jth column is 255, the data electrode Dj of the jth column is supplied to the entire horizontal scanning period (255T).
, A voltage + Vd is applied.

Meanwhile, in the case of the display panel 10 using the cold cathode electron emitting device, the electron emitting device has a threshold value for emitting electrons. In FIG. 11, the solid line is
Shows the characteristic of emission current i _e to the applied voltage v _a of the cold cathode electron emission element. Voltage Vth is a threshold for the emission current i _e is generated. During the scanning period, the scanning electrodes S1 to S1
Voltage (absolute value) Vs applied to Sm and data electrode D
The voltages Vd applied to 1 to Dn are both set to be equal to or lower than the voltage Vth, and the voltage (Vd + Vs) is set to be higher than the voltage Vth.

The voltage applied to the cold cathode electron-emitting device (cell 10s) includes the potentials of the data electrodes D1 to Dn and the scanning electrodes S
In this case, when a voltage (Vd or Vs) is applied to only one of the data electrodes D1 to Dn and the scan electrodes S1 to Sm, the cold cathode electron-emitting device emits electrons. No data electrode D1 to Dn and scan electrode S1
Only when a voltage is applied to both Sm to Sm, the cold cathode electron-emitting device emits electrons, and the cell 10s emits light.

In the example of FIG. 10, the voltage applied to the cell 10s in the i-th row and the j-th column is always equal to or lower than the voltage Vth, so that the cell 10s does not emit light. The voltage applied to the cell 10s in the (i + 1) -th row and the j-th column is the voltage Vt only for a period of 128T indicated by hatching.
h, the cell 10s emits light only for a period of 128T. Since the voltage applied to the cell 10s in the (i + 2) row and j column exceeds the voltage Vth in the hatched period of 255T, the cell 10s emits light in the period of 255T.

Here, only the display process from the i-th row to the (i + 2) -th row has been described.
0 scanning electrodes S1 to Sm are sequentially arranged from row 1 to row M.
A scan pulse is applied, and a PWM-modulated pulse is applied to the data electrodes D1 to Dn in accordance with the scan timing. In the case of displaying 480 rows × 640 columns of effective pixels, 480 scanning electrodes and 6 data electrodes are used.
There are 40 data electrodes and 1920 data electrodes in the case of color display of the RGB stripe structure.

[0014]

According to the gradation expression by the PWM modulation, it is possible to exhibit a substantially linear light emission characteristic with respect to the image data. However, in an actual video signal, the relationship between the brightness of the original image (original image) and the amplitude of the image data is not linear but has a gamma characteristic. Therefore, in a matrix type display device having linear characteristics, it is necessary to perform inverse gamma correction on a video signal. Although it is conceivable to perform inverse gamma correction on the input video signal in advance, the configuration becomes complicated. At this time, it is desirable that the peak luminance is not reduced as much as possible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a matrix type display device capable of performing inverse gamma correction by improving a driving method while suppressing a decrease in peak luminance. With the goal.

[0016]

According to the present invention, there is provided a display panel (10) in which light emitting elements (10s) are arranged in a matrix by a plurality of rows and a plurality of columns. In the matrix type display device that drives the light emitting elements, the driving circuits (2 to 4, 6, 7, Sd1 to Sdn, and Ss) that drive the light emitting elements by a driving waveform corresponding to the image data displayed by the light emitting elements.
1 to Ssm), and forming a gradient in the driving waveform and forming a flat portion in another part of the driving waveform so that the light emitting characteristics of each of the light emitting elements become inverse gamma characteristics. (8) A matrix-type display device characterized by comprising:

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a matrix type display device according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing a first embodiment of the matrix type display device of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the first embodiment of the matrix type display device of the present invention, and FIG. FIG. 4 is a waveform chart for explaining the matrix type display device of the present invention, and FIG. 5 is a waveform chart for explaining an application example of the matrix type display device of the present invention. FIGS. 6 and 7 are block diagrams showing a second embodiment of the matrix type display device of the present invention, and FIG. 7 is a waveform diagram for explaining the operation of the second embodiment of the matrix type display device of the present invention. 1 and 6, the same parts as those in FIG. 8 are denoted by the same reference numerals.

<First Embodiment> In FIG. 1, a display panel 10 is a display panel using, for example, a cold cathode electron-emitting device, and the specific configuration is as described with reference to FIG. The video signal input to the terminal 1 is transmitted to the shift register 2
Is written to. After one row of data is written in the shift register 2, the data is latched by the latch circuit 3. The data output from the latch circuit 3 is input to the PWM circuit 4. The PWM4 circuit controls the switches Sd1 to Sdn with a pulse corresponding to the magnitude of the data. The switches Sd1 to Sdn are turned on when the pulse input from the PWM circuit 4 is high. Switches Sd1 to Sdn
, A ramp-shaped voltage having a partially flat voltage as described later from the waveform generation circuit 8 is input, and the ramp-shaped voltage is supplied to the data electrodes D1 to Dn of the display panel 10. In the present specification, for convenience, not only a waveform having a gradient in all periods but also a waveform having a gradient in one part and a flat part in another part is referred to as a ramp voltage.

The synchronization signal input to the terminal 5 is input to the timing control circuit 6. The timing control circuit 6 supplies a shift clock to the shift register 2 and a latch clock to the latch circuit 3. The timing control circuit 6 also supplies a pulse of one line width to the shift register 7. The shift register 7 controls the switches Ss1 to Ssm with the pulse. Switches Ss1 to Ssm
Is turned on when the scan pulse input from the shift register 7 is high, and the scan electrode S1 of the display panel 10 is turned on.
ＳSm is supplied with a constant voltage −Vs. The timing control circuit 6 further controls the timing at which the waveform generation circuit 8 generates a ramp voltage.

Here, the operation of the driving circuit shown in FIG.
This will be described in detail with reference to FIG. FIG. 2 also shows the operation when displaying the j-th column as an example, and (A) to (C)
Shows a scan pulse applied to the scan electrode, (D) shows a ramp-shaped voltage generated by the waveform generating circuit 8 having a partially flat voltage, (E) shows a pulse applied to the data electrode, F) to (H) show voltages applied to the element (cell 10s). As shown in FIG. 2D, the ramp-like voltage generated by the waveform generating circuit 8 has a waveform having a predetermined gradient and a flat waveform following it in one horizontal scanning period. The lowest voltage (start voltage of the slope) of the ramp voltage is the voltage + Vd1, and the highest voltage (end voltage of the slope and the voltage of the flat portion) is the voltage + Vd2.

Here, the number of bits of the video signal is 8 bits, perfect black is represented as 0, and perfect white is represented as 255, i-th row and j-th column is black (0), and i + 1-th row and j-th column are gray ( 128), the case where the (i + 2) th row and the jth column are white (255). One horizontal scanning period is constituted by 255 units. The unit time is a clock cycle, and the unit time is represented by T. The gradation is expressed by the data electrodes D1 to D1.
This is performed by changing the pulse width of the pulse applied to Dn from 0T to 255T.

As shown in FIG. 2, during the horizontal scanning period of the i-th row, the voltage -Vs is applied to the scanning electrodes Si of the i-th row, and no voltage is applied to the other scanning electrodes. At this time, since the signal in the i-th row and the j-th column is 0, the data electrode Dj in the j-th column is always at the 0 potential. When the horizontal scanning period for the i-th row ends, the process proceeds to the horizontal scanning period for the (i + 1) -th row.

In the horizontal scanning period of the (i + 1) th row, i +
A voltage -Vs is applied to one row of scan electrodes S (i + 1), and no voltage is applied to the other scan electrodes. At this time, since the signal of the (i + 1) -th row and the j-th column is 128, a voltage is applied to the data electrode Dj of the j-th column for about half (128T) of the horizontal scanning period (255T), and 0 is applied for about half of the subsequent period. Potential. The voltage applied to the data electrode Dj has a ramp-shaped waveform obtained by cutting off the ramp-shaped voltage shown in FIG. When the horizontal scanning period of the (i + 1) -th row ends, the process proceeds to the horizontal scanning period of the (i + 2) -th row.

In the horizontal scanning period of the i + 2 row, i +
The voltage −Vs is applied to the scanning electrodes S (i + 2) of the two rows, and no voltage is applied to the other scanning electrodes. At this time, since the signal of the (i + 2) th row and the jth column is 255, the data electrode Dj of the jth column is applied to the entire horizontal scanning period (255).
Voltage is applied at T). The voltage applied to the data electrode Dj has a partially flat ramp waveform corresponding to the ramp voltage shown in FIG.

In the scanning period, the voltage (absolute value) Vs applied to the scanning electrodes S1 to Sm and the data electrodes D1 to Dn
Are set to be equal to or lower than the voltage Vth which is the threshold for the electron-emitting device of the display panel 10 to emit electrons described with reference to FIG.
The sum of 1 to Vd2 and the voltage Vs is set higher than the voltage Vth. Therefore, the data electrodes D1 to Dn and the scan electrode S
Only when a voltage is applied to both 1 to Sm, the cold cathode electron-emitting device emits electrons, and the cell 10s emits light.

In the example of FIG. 2, the element (cell 10
Since the voltage applied to s) is always equal to or lower than the voltage Vth, the cell 10s does not emit light. Cell 10 at i + 1 row and j column
Since the voltage applied to s exceeds the voltage Vth only for a period of 128T indicated by hatching, the cell 10s emits light only for a period of 128T. Since the voltage applied to the cell 10s in the (i + 2) row and j column exceeds the voltage Vth in the hatched period of 255T, the cell 10s emits light in the period of 255T. In the present embodiment, it can be seen that a voltage having a predetermined gradient is applied during the light emitting period indicated by the hatching.

Here, only the display process from the i-th row to the (i + 2) -th row has been described.
0 scanning electrodes S1 to Sm are sequentially arranged from row 1 to row M.
A scan pulse is applied, and a PWM-modulated pulse is applied to the data electrodes D1 to Dn in accordance with the scan timing. At this time, the voltage applied to the data electrodes D1 to Dn is different from a conventional flat waveform, and the ramp voltage generated by the waveform generating circuit 8 is changed according to the pulse width of the pulse generated by the PWM circuit 4. It becomes the cut waveform.

The light emission characteristics when driven with the above-described waveforms will be specifically described. Note that, to simplify the calculation,
It is assumed that the voltage-emission current characteristics of the electron-emitting device described with reference to FIG. 11 are approximated not by actual characteristics shown by solid lines but by straight lines shown by broken lines. When this straight line is expressed by a mathematical formula, the following formula is obtained. Incidentally, i _e is the emission current, v _a is the applied voltage, g is the slope of the straight line (conductance).

[0029]

(Equation 1)

The voltage v _a applied to each element of the display panel 10 is such that the voltage at t = 0 is v ₁ and t = t as shown in FIG.
₁ voltage linearly boosted so as to be _{v 2, t = t 1 ~t} 2
If it is assumed that the voltage is constant v ₂ , it can be expressed as a function of time t as in the following equation.

[0031]

(Equation 2)

[0032]

(Equation 3)

The electronic volume q to be emitted from the elements in the pulse width from time 0 up to time t _p may be calculated by the following equation.

[0034]

(Equation 4)

[0035] Here, the portion t is linearly boost in the period 0 to t ₁ becomes a following formula, the amount of emitted electrons q with respect to the pulse width t _p is seen to exhibit a quadratic function.

[0036]

(Equation 5)

Further, in the t period of constant voltage t ₁ ~t _2, since the sum of (5) the amount of electrons t _p = t ₁ of formula and the amount of electrons flat portion, becomes the following equation, the amount of emitted electrons q with respect to an increase of the pulse width t _p increases linearly.

[0038]

(Equation 6)

[0039] than these things, pulse width t _p is 0~t ₁
It can be seen that the function is a quadratic function in the range of, and a linear function (straight line) in the range of t _{1 to} t ₂ . Therefore, the light emission characteristics for the image data are as shown by the curve 100 in FIG. Strictly speaking, it is necessary to consider an error caused by approximating a voltage-emission current characteristic with a straight line, a saturation phenomenon of a phosphor that emits light upon irradiation with electrons, and the like. However, even in consideration of the above error, the saturation phenomenon of the phosphor, and the like, the emission characteristics for the image data show an inverse gamma curve as shown by a curve 100 in FIG.

Therefore, when the display panel 10 is driven by the driving method of the first embodiment, the video signal can be subjected to inverse gamma correction. By performing inverse gamma correction on a video signal having a gamma characteristic, as a result, it is possible to display an original image with substantially linear emission characteristics with respect to an original image.

[0041] If, instead of providing a flat period that is a constant voltage of t ₁ ~t _2, if linearly boosted so that v ₂ at v _1, t = t ₂ at t = 0, the light emitting The characteristic is shown by curve 3 in FIG.
It becomes a quadratic function in all periods as shown by 00. However, this time, the maximum light emission amount at t _p = t ₂ (peak luminance) is lower than the curve 100. As described above, in the first embodiment, the inverse gamma correction can be performed while suppressing the decrease in the peak luminance.

Assuming that the relative luminance of the subject is L, the HDTV is defined to have a low luminance of 0 ≦ L <0.018 and a gamma correction of a 4.5L straight line. Therefore, in order to realize the inverse characteristic in the matrix type display device, the low luminance portion must be a straight line. In order to realize this characteristic, as shown in FIG. 5, the waveform applied to the display panel 10 may be provided with a constant voltage period on the start voltage side (t = 0 to t ₃ ). The calculation for obtaining the light emission amount at this time is omitted, but the light emission characteristics are as shown by a curve 200 in FIG. As described above, the present invention can also be applied to a case where light emission characteristics are required to be partially linear.

In the above embodiment, the ramp voltage is
Although the waveform in which the end voltage is higher than the start voltage of the slope is used, a waveform in which the end voltage is lower than the start voltage of the slope is used, and according to the pulse width of the pulse generated by the PWM circuit 4, Even if the waveform is cut from the end voltage side of the ramp voltage, exactly the same effect is obtained. A gradient may be formed in the driving waveform for driving the cell 10s so that the light emission characteristic of each cell 10s of the display panel 10 has the inverse gamma characteristic. Note that ringing (overshoot) is less likely to occur when a waveform in which the end voltage is higher than the slope start voltage is used as the ramp voltage.

<Second Embodiment> A second embodiment shown in FIG.
The ramp-like voltage generated by the waveform generating circuit 8 is supplied to the scan electrodes S1 to Sm of the display panel 10. To the switches Ss1 to Ssm, a ramp-shaped voltage having a partially flat voltage as described after the waveform generation circuit 8 is input, and the scan electrodes S1 to S1 of the display panel 10 are input.
A ramp voltage is supplied to Sm.

Here, the operation of the drive circuit shown in FIG.
This will be described in detail with reference to FIG. FIG. 7 also shows an operation when displaying the j-th column as an example. FIG. 7A shows a ramp-shaped voltage generated by the waveform generating circuit 8 having a partially flat voltage, and FIGS. D) shows a scan pulse applied to the scan electrode, (E) shows a pulse applied to the data electrode, and (F) to (H) show voltages applied to the element (cell 10s). As shown in FIG. 2A, the ramp-shaped voltage generated by the waveform generating circuit 8 has a waveform having a predetermined gradient and a flat waveform following it in one horizontal scanning period. The maximum voltage of the absolute value of the ramp voltage (the end voltage of the slope and the voltage of the flat portion) is the voltage −V
s2, and the lowest voltage of the absolute value (the start and end points of the slope) is the voltage -Vs1.

Also in this case, the number of bits of the video signal is 8 bits, complete black is represented as 0, and complete white is represented as 255, i-th row and j-th column is black (0), and i + 1-th row and j-th column are gray ( 128), the case where the (i + 2) th row and the jth column are white (255). One horizontal scanning period is constituted by 255 units. The gradation expression is performed by changing the pulse width of the pulse applied to the data electrodes D1 to Dn from 0T to 255T.

As shown in FIG. 7, during the horizontal scanning period of the i-th row, the voltages -Vs1 to -Vs
No. 2 ramp voltage is applied, and no voltage is applied to the other scan electrodes. At this time, since the signal in the i-th row and the j-th column is 0, the data electrode Dj in the j-th column is always at the 0 potential. When the horizontal scanning period for the i-th row ends, the process proceeds to the horizontal scanning period for the (i + 1) -th row.

Even in the horizontal scanning period of the (i + 1) th row, i +
The voltages -Vs1 to -Vs are applied to the scanning electrodes S (i + 1) of one row.
No. 2 ramp voltage is applied, and no voltage is applied to the other scan electrodes. At this time, since the signal of the (i + 1) -th row and the j-th column is 128, the voltage + Vd is applied to the data electrode Dj of the j-th column only for about half (128T) of the horizontal scanning period (255T). It becomes 0 potential. When the horizontal scanning period of the (i + 1) th row is completed, i + 2
Move to the horizontal scanning period of the row.

Even in the horizontal scanning period of the (i + 2) th row, the i +
The voltages -Vs1 to -Vs are applied to the two rows of scan electrodes S (i + 2).
No. 2 ramp voltage is applied, and no voltage is applied to the other scan electrodes. At this time, since the signal of the (i + 2) th row and the jth column is 255, the voltage + Vd is applied to the data electrode Dj of the jth column during the entire horizontal scanning period (255T).

In the scanning period, the voltages (absolute values) Vs1 to Vs2 applied to the scan electrodes S1 to Sm and the voltage Vd applied to the data electrodes D1 to Dn are both the electron emission elements of the display panel 10 described with reference to FIG. Is set to be equal to or lower than a voltage Vth which is a threshold value for emitting electrons, and a voltage Vd
And the sum of the voltages Vs1 and Vs2 is set higher than the voltage Vth. Therefore, the data electrodes D1 to Dn and the scan electrode S
Only when a voltage is applied to both 1 to Sm, the cold cathode electron-emitting device emits electrons, and the cell 10s emits light.

In the example of FIG. 7, the element (cell 10
Since the voltage applied to s) is always equal to or lower than the voltage Vth, the cell 10s does not emit light. Cell 10 at i + 1 row and j column
Since the voltage applied to s exceeds the voltage Vth only for a period of 128T indicated by hatching, the cell 10s emits light only for a period of 128T. Since the voltage applied to the cell 10s in the (i + 2) row and j column exceeds the voltage Vth in the hatched period of 255T, the cell 10s emits light in the period of 255T. Also in this example, it can be seen that a voltage having a predetermined gradient is applied during the light emitting period indicated by the diagonal lines.

Here, only the display process from the i-th row to the (i + 2) -th row has been described.
0 scanning electrodes S1 to Sm are sequentially arranged from row 1 to row M.
A scan pulse is applied, and a PWM-modulated pulse is applied to the data electrodes D1 to Dn in accordance with the scan timing. At this time, the voltage applied to the scan electrodes S1 to Sm is a ramp-like voltage generated by the waveform generating circuit 8, unlike a flat waveform as in the related art.

Also in the second embodiment, the light emission characteristic with respect to the image data shows an inverse gamma curve as shown by a curve 100 in FIG. Therefore, when the display panel 10 is driven by the driving method of the second embodiment, the video signal can be subjected to inverse gamma correction. By performing inverse gamma correction on a video signal having a gamma characteristic, as a result, it is possible to display an original image with substantially linear emission characteristics with respect to an original image. Also in the second embodiment,
Since the ramp voltage has a flat portion, the inverse gamma correction can be performed while suppressing a decrease in peak luminance.

In the above embodiment, the ramp voltage is
Although the waveform in which the absolute value of the end voltage is higher than the absolute value of the start voltage of the slope is used, a waveform in which the absolute value of the end voltage is lower than the absolute value of the start voltage of the slope is used.
The same effect can be obtained by using a pulse whose rising position changes in accordance with image data, contrary to FIG. 7E, as the pulse generated by the M circuit 4. When a waveform in which the absolute value of the end voltage is higher than the absolute value of the slope start voltage is used as the ramp voltage, ringing (overshoot) is less likely to occur.

As described above, according to the present invention, the emission current from the electron-emitting device by the pulse width corresponding to the image data is:
By giving a gradient so that it increases or decreases with time, the light emission characteristic for the image data can be made the inverse gamma characteristic. In addition, by providing a flat portion, a decrease in peak luminance can be suppressed. The present invention is not limited to the above first and second embodiments, but can be variously modified. For example, the scan electrodes S1 to S1 of the display panel 10 are combined by combining the first embodiment and the second embodiment.
A ramp voltage may be supplied to both Sm and the data electrodes D1 to Dn. The drive signals (drive waveforms) supplied to the scan electrodes S1 to Sm and the data electrodes D1 to Dn may be current sources instead of voltage sources.
The polarity of the drive waveform between the data electrodes D1 to Dn may be opposite.

Further, it is not necessary that the ramp portion of the ramp waveform formed (added) to the drive waveform increases or decreases linearly. By using a non-linear waveform, desired emission characteristics can be obtained. The present invention is not limited to a field emission display device or an EL display device, but can be applied to any matrix type display device in which a light emitting element is driven by a pulse having a pulse width corresponding to image data.

[0057]

As described above in detail, in the matrix type display device of the present invention, the driving circuit for driving each light emitting element by the driving waveform corresponding to the image data displayed by each light emitting element, and the light emitting element respectively And a gradient / flat portion forming means for forming a gradient in a part of the drive waveform and forming a flat portion in the other part of the drive waveform so that the light emission characteristic of the drive waveform becomes an inverse gamma characteristic. So
Inverse gamma correction can be performed on a video signal while suppressing a decrease in peak luminance. As a result, in the matrix type display device, it is possible to display with high peak luminance and substantially linear emission characteristics with respect to the original image.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the first embodiment of the present invention.

FIG. 3 is a waveform chart for explaining the present invention.

FIG. 4 is a characteristic diagram for explaining the present invention.

FIG. 5 is a waveform chart for explaining an application example of the present invention.

FIG. 6 is a block diagram showing a second embodiment of the present invention.

FIG. 7 is a waveform chart for explaining the operation of the second embodiment of the present invention.

FIG. 8 is a block diagram showing a conventional example.

FIG. 9 is a diagram illustrating a configuration of a display panel of a matrix display device.

FIG. 10 is a waveform chart for explaining the operation of the conventional example.

FIG. 11 is a characteristic diagram showing a relationship between a voltage applied to a cold cathode electron-emitting device and an emission current.

[Explanation of symbols]

 1, 5 terminal 2 shift register 3 latch circuit 4 pulse width modulation circuit 6 timing control circuit 7 shift register (pulse supply circuit) 8 waveform generation circuit 10 display panel 10s cell (light emitting element) Sd1-Sdn, Ss1-Ssm switch

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[Procedure amendment]

[Submission date] January 5, 1999 (1999.1.5)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 3

[Correction method] Change

[Correction contents]

Claims (4)

[Claims] 1. A matrix-type display device for driving a display panel in which light-emitting elements are arranged in a matrix by a plurality of rows and a plurality of columns, wherein a driving waveform corresponding to image data displayed by each of the light-emitting elements is used. A driving circuit for driving each light emitting element, and forming a gradient in a part of the driving waveform and a flat part in another part of the driving waveform so that the light emitting characteristic of each light emitting element has an inverse gamma characteristic. A matrix type display device comprising: a gradient / flat portion forming means for forming. 2. The driving circuit according to claim 1, further comprising a pulse width modulation circuit for supplying a pulse having a pulse width modulated within one horizontal scanning period to the display panel in accordance with the image data. 2. The matrix type display device according to claim 1, wherein the portion forming means forms a gradient and a flat portion in the pulse. 3. A pulse width modulation circuit for supplying a first pulse having a pulse width modulated within one horizontal scanning period to one of a row and a column of the display panel according to the image data. A pulse supply circuit for supplying a second pulse having a length of one horizontal scanning period to the other of the rows or columns of the display panel in accordance with the image data. 2. The matrix type display device according to claim 1, wherein the second pulse forms a gradient and a flat portion in the second pulse. 4. The matrix type display device according to claim 1, wherein said matrix type display device is a field emission display device or an electroluminescence display device.