Computer graphics processing and selective visual display system – Display peripheral interface input device – Light pen for fluid matrix display panel
Reexamination Certificate
1998-06-25
2001-08-21
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Light pen for fluid matrix display panel
C345S182000, C345S063000
Reexamination Certificate
active
06278436
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a brightness controlling apparatus for controlling a brightness of a video signal.
2. Description of the Related Art
There is a plasma display panel as a 2-dimensional image display apparatus of thin type. Among them, a plasma display panel of AC discharging type having a memory function is being developed.
In a display apparatus equipped with such a plasma display panel of AC discharging type, a signal processing unit processes a so-called composite video signal as an input signal. Then, a display unit including the plasma display panel receives a driving signal from the signal processing unit, so that the plasma display panel displays a video image on a 2-dimensional picture plane.
More concretely, this signal processing unit has an A/D (Analog to Digital) converting circuit, which converts the composite video signal as an input signal into pixel data. The pixel data is outputted from the A/D converter through a frame memory, an output processing circuit etc. to the display unit. The plasma display panel in the display unit includes row (i.e., vertical line) electrodes, and line (i.e., horizontal line) electrodes. As the pixel data is inputted to a row electrode driver in the display unit, the row electrodes are driven by the row electrode driver, which generates and supplies pixel data pulse based on the pixel data to the row electrodes respectively. On the other hand, the line electrodes are driven by a line electrode driver in the display unit, which generates and supplies scanning pulse etc., in synchronization with the pixel data pulse, to the line electrodes respectively. When the voltage difference is applied to each pixel located at an intersection of the row electrode and the line electrode respectively where a dielectric substance is interposed between the row electrode and the line electrode, the discharging light emission is caused at each pixel. Then, the discharging light emission is repeatedly performed by an application of a pulse to keep the discharge with a barrier charge in the dielectric substance. When a pulse to erase the barrier charge in the dielectric substance is applied to the line electrodes, the discharging light emission is stopped. In this manner, by the timing of applying this pulse to erase the barrier charge, the brightness of the discharge light emission can be controlled.
In the above described driving operation of the plasma display panel, a so-called ABL (Automatic Brightness/Beam Limiter) is employed to limit the brightness according to the video signal. The ABL is constructed such that the whole display picture plane is divided into a plurality of blocks and it limits the brightness of the whole frame of the video image or picture when an APL (Average Picture Level), which is the average value of the brightness signals of the video image in each block, in just one block exceeds a standard value.
The operation of the ABL is explained with reference to FIG.
6
(
a
) and FIG.
6
(
b
). As shown in FIG.
6
(
a
), it is assumed that the gradations of the brightness are 0 to 255 gradations, one picture plane consists of 8 blocks divided with respect to a vertical direction, and the brightness signal level is controlled or limited to be ½ when the gradation of any block exceeds the APL 144 as the standard level to actuate the ABL, for example. At this time, in case that each of the 1
st
to 3
rd
blocks of the inputted video image has the gradation of the APL 128, the 4
th
block has the gradation of the APL 200, each of the 5
th
to 8
th
blocks has the gradation of the APL 200, since the gradation of the 4
th
block (which has the brightness of the APL 200) exceeds the APL 144 as the standard value, the ABL is actuated for all of the signals of the whole one picture plane. Thus, the gradations of the brightness signals of all blocks become the APL display gradations as shown in FIG.
6
(
b
).
Namely, even if the gradation of just one block exceeds the standard APL, the ABL is actuated. Therefore, a case often occurs where the whole picture plane becomes dark.
In this manner, according to the above described brightness controlling apparatus, since the ABL is actuated even for such a video image or picture that the bright portion is dispersed on the picture plane and that the bright portions are relatively just rare and local on the video image or the picture plane, the whole picture plane becomes dark. For example, even in case of the picture having the pattern shown in FIG.
6
(
a
), the ABL is actuated so that the whole picture plane becomes dark (on the basis of the bright signals shown in FIG.
6
(
b
)), which is a serious problem in a practical sense.
SUMMARY OF THE INVENTION
Given these circumstances, it is an object of the present invention to provide a brightness controlling apparatus, which can prevent the picture plane from becoming dark in case that the video image or picture is just locally bright.
The above object of the present invention can be achieved by a first brightness controlling apparatus for adjusting a brightness level of a video signal inputted thereto and outputting the video signal having the adjusted brightness level to a display apparatus so that the display apparatus displays a video image corresponding to the video signal on the basis of the video signal having the adjusted brightness level. The first brightness controlling apparatus of the present invention is provided with: an average brightness level detecting device for detecting average brightness levels of the video signal in a plurality of blocks respectively, the blocks being obtained by dividing the video signal to be displayed on a picture plane by the display apparatus into the blocks; an average brightness level adding device for adding to each other the average brightness levels of the video signal in at least two of the blocks at a vicinity of each other for each of the blocks, which are detected by the average brightness level detecting device; a brightness level setting device for setting the brightness level of the video signal on the basis of the added average brightness levels added by the average brightness level adding device; and an outputting device for outputting the video signal having the brightness level set by the brightness level setting device to the display apparatus as the video signal having the adjusted brightness level.
According to the first brightness controlling apparatus, the average brightness levels of the video signal in a plurality of blocks are detected by the average brightness level detecting device, respectively. Then, the average brightness levels of the video signal in at least two of the blocks at a vicinity of each other are added to each other by the average brightness level adding device, for each of the blocks. Then, the brightness level of the video signal is set by the brightness level setting device, on the basis of the added average brightness levels. Finally, the video signal having the brightness level set by the brightness level setting device is outputted by the outputting device, to the display apparatus as the video signal having the adjusted brightness level. Accordingly, the display apparatus displays the video image corresponding to the video signal, on the basis of the video signal having the adjusted brightness level.
Therefore, since the first brightness controlling apparatus adjusts the brightness level on the basis of the average brightness levels as for the certain number of blocks, in case that the video image is just locally bright, the brightness level is not controlled or adjusted. On the other hand, in case that the adjustment for the brightness of the video image is really desired or required, the brightness level is certainly controlled or adjusted by the first brightness controlling apparatus, so that it is possible to prevent the display apparatus (e.g., the plasma display panel) from being destroyed or damaged due to the high brightness.
In one aspect of the first brightness controlling
Hosoi Kenichiro
Kikuchi Nozomu
Hjerpe Richard
Nguyen Kimnhung
Pioneer Electronic Corporation
Pitney Hardin Kipp & Szuch LLP
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