The accompany drawings, which are included to provide a further understanding of the invention and are incorporated on and constitute a part of this specification illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:
a to 5c illustrate histograms of a video signal to which characteristics of each of a video signal controller and a video signal limitation unit according to an exemplary embodiment are applied;
a and 6b illustrate subfields before and after the application of characteristics of a power controller according to an exemplary embodiment; and
a and 7b illustrate histograms of a video signal to which characteristics of a video signal limitation unit according to an exemplary embodiment are applied.
Reference will now be made in detail embodiments of the invention examples of which are illustrated in the accompanying drawings.
As illustrated in
The inverse gamma correction unit 100 can perform an inverse gamma correction process on a video signal. The inverse gamma correction unit 100 maps an input n-bit video signal according to an inverse gamma curve to convert the n-bit video signal into a Q-bit video signal. Since an input video signal is generally 8 bits, an explanation will be below given of an example of 8-bit video signal. When an 8-bit video signal is corrected into a Q-bit video signal, the inverse gamma correction unit 100 determines an output of the inverse gamma correction depending on the number of sustain pulses.
2Q-1≦P<2Q [Equation 2]
In the above Equation 2, P indicates the number of sustain pulses. For instance, when the number of sustain pulses is 1023, the size of output data is 10 bits through the above Equation 2 and a lookup table (not shown) of the inverse gamma correction unit 100 is determined. In other words, the inverse gamma correction unit 100 outputs an inverse-gamma corrected gray level corresponding to the number of sustain pulses.
The video signal input to the inverse gamma correction unit 100 is a digital signal. In case that an analog video signal is input to the plasma display panel, the analog video signal is converted into a digital video signal using an analog-to-digital converter (not shown). Further, the inverse gamma correction unit 100 may include a lookup table for storing data corresponding to an inverse-gamma curve so as to map a video signal, and a logic circuit for producing logical operations from the data corresponding to the inverse-gamma curve.
Accordingly, the inverse gamma correction unit 100 can output a maximum gray level (S) of the video signal after being inverse gamma corrected.
The video signal controller 200 can calculate an occupation proportion of a maximum gray level of a video signal in a histogram of the video signal using location information of an object displayed on the screen.
In other words, an occupation proportion (h) of a maximum gray level of a video signal can be output. The maximum gray level of the video signal may be indicated as a white peak. This will be described below with reference to
The video motion unit 210 can calculate a motion proportion of a video signal displayed on the screen. In other words, a motion proportion (in) of a video signal can be calculated in terms of %.
The APL unit 220 can calculate an APL of a video signal. In other words, an APL (y) of a video signal can be output.
The video signal limitation unit 300 can limit the maximum gray level of the inverse-gamma corrected video signal by the inverse gamma correction unit 100 using the occupation proportion (h) output from the video signal controller 200, the motion proportion (m) output from the video motion unit 210, and the APL (y) output from the APL unit 220.
The video signal limitation unit 300 can output a value (I) obtained by limiting the maximum gray level (S) of the video signal after being inverse-gamma corrected by the inverse gamma correction unit 100 using the above values h, m and y. The value (I) may be inversely proportional to the value (m), and may be proportional to the value (h).
The power controller 400 can control one of an APL of the video signal and the number of subfields using the maximum gray level (S) limited by the video signal limitation unit 300. Therefore, the power controller 400 can change the APL (y) output from the APL unit 220 into an optimized APL (Y′), and can output a value (S*g) obtained by multiplying the maximum gray level (S) of the video signal by a gain (g).
The half toning unit 500 can perform a half toning process on the video signal output from the power controller 400. The half toning unit 500 diffuses a quantization error of digital video data (RGB) after being inverse-gamma corrected into adjacent discharge cells, and then finely controls a luminance of the video signal. For this, the half toning unit 500 divides data into an integer part and a fraction part, and multiplies the fraction part by a previously set error diffusion coefficient (for example, Floid-Steinberg coefficient). Hence, the half toning unit 500 can perform the half toning process on the optimized APL (Y′) and the value (S*g).
The subfield mapping unit 600 can map subfields of the video signal output from the half toning unit 500. The subfield mapping unit 600 maps the digital video data output from the half toning unit 500 according to a subfield pattern previously set based on each bit, and then supplies the mapped data to a data driving integrated circuit (not shown) of the plasma display panel 700 through a data arranging unit (not shown).
The plasma display panel 700 receives the video signal output from the subfield mapping unit 600, and then can display an image on the screen.
As above, the driving device of the plasma display panel according to an exemplary embodiment can compensate a distortion of a video signal using a histogram of the video signal and a weight value depending on a location of a bright portion of an object.
As illustrated in
The histogram detection unit 201 can provide location information of an object in a histogram with respect to a present pixel of a video signal presently input.
The location detection unit 202 can provide location information of the object on the screen with respect to the present pixel. In other words, the location detection unit 202 can calculate a moving distance of the object from the center of the screen.
The central object privilege calculation unit 203 can control a maximum gray level of the video signal depending on the location information output from the location detection unit 202. In other words, when the output location information is located in the center of the screen, a maximum gray level of a video signal is controlled to be high. Further, when the output location information is far away from the center of the screen, a maximum gray level of a video signal is controlled to be low.
The conversion unit 204 combines the maximum gray level of the video signal output from the central object privilege calculation unit 203 with the location information of the object in the histogram, and obtains the occupation proportion (h) of the maximum gray level of the video signal using the combined information.
Accordingly, as the output location information is far away from the center of the screen, the occupation proportion (h) of the maximum gray level of the video signal is reduced. As the output location information is close to the center of the screen, the occupation proportion (b) of the maximum gray level of the video signal increases.
The histogram of the video signal, to which the characteristics of each of the video signal controller 200, the video signal limitation unit 300, and the power controller 400 are applied, will be described below.
a to 5c illustrate histograms of a video signal to which characteristics of each of a video signal controller and a video signal limitation unit according to an exemplary embodiment are applied.
a illustrates a histogram of a video signal to which characteristics of the video signal controller 200 are applied. In
Generally, a main object or a main area of an image is located in the center of the screen, and thus the center of the screen is important. Accordingly, the driving device of the plasma display panel according to an exemplary embodiment supplies information of the video signal obtained through the APL unit and the video motion unit to the video signal limitation unit, and supplies the location information on the object of the video signal obtained through the video signal controller to the video signal limitation unit. Hence, the driving device of the plasma display panel according to an exemplary embodiment can reduce a distortion on the information of the video signal.
The video signal limitation unit can be indicated as maximum input signal control, and the video signal controller can be indicated as central object privilege.
b and 5c illustrate histograms of a video signal to which characteristics of each of the video signal controller 200 and the video signal limitation unit 300 are applied. In
In
In
In other words, the occupation proportion of the maximum gray level of the video signal in the histogram of the video signal is calculated and controlled using the location information of the object displayed on the screen, and thus the power consumption can be reduced and the gray scale representation can be improved.
a and 6b illustrate subfields before and after the application of characteristics of a power controller according to an exemplary embodiment.
a illustrates subfields before the application of characteristics of the power controller. In
Accordingly, an image can be displayed only using 256 sustain pulses (i.e., (the total number of sustain pulses)/4 (1024/4=256). In case that the total number of sustain pulses is 256, the APL is 987. When the APL is 987, a maximum gray level of the video signal ranges 1 to 1020 using the reciprocal (=4) of the calculated input image display ratio (¼) as a gain value of the video signal. Hence, a half toning noise and power consumption can be reduced.
In other words, the power controller is used to reduce power consumption in the screen of a low APL. The power controller reduces the number of sustain pulses in subfields, which are not actually used, or removes the subfields, which are not actually used to increase the driving efficiency. The power controller according to an exemplary embodiment may be indicated as black power recovery.
The power controller controls the APL and the use of the subfields with reference to the maximum gray level of the video signal. When the maximum gray level is low at a low APL, the use of the power controller is effective. In the other hand, when the maximum gray level is high at a low APL, the use of the power controller is not effective. Since many audiovisual (AV) images pass through a VSC board and perform operations for increasing a contrast ratio such as histogram extension, it is difficult to expect the use effect of the power controller in an actual AV image.
Accordingly, the video signal limitation unit is used to maximize the use effect of the power controller. The video signal limitation unit controls a maximum gray level of the input video signal by changing the input video signal using information of the input video signal.
a and 7b illustrate histograms of a video signal to which characteristics of a video signal limitation unit according to an exemplary embodiment are applied.
a illustrates information on a histogram of a video signal.
In case that only the power controller is applied to a video signal in which a white peak is generated, the video signal can have a maximum luminance capable of representing a maximum gray level of the video signal in spite of the video signal mainly using a low gray level at a low APL. Therefore, it is difficult to expect the use effect of the power controller.
Accordingly, the video signal limitation unit is used to overcome drawbacks of the power controller. The video signal limitation unit can limit a luminance of a portion of an image having a maximum gray level at a low value using a maximum input signal control method assuming that an occupation proportion of a white peak portion to the entire image is small and negligible.
As illustrated in
Further, as illustrated in
Accordingly, since an exemplary embodiment sets a gray scale and a luminance using a histogram and a motion of a video signal and location information of an object, a gray scale can be finely represented and the power consumption can be reduced.
The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the foregoing embodiments is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art.
Number | Date | Country | Kind |
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10-2006-0068103 | Jul 2006 | KR | national |