Computer graphics processing and selective visual display system – Display peripheral interface input device – Light pen for fluid matrix display panel
Reexamination Certificate
1999-02-08
2001-04-03
Luu, Matthew (Department: 2672)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Light pen for fluid matrix display panel
C345S182000, C345S182000
Reexamination Certificate
active
06211854
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display apparatus and to a driving method for the display apparatus; more particularly, the invention relates to a moving-image/still-image determination circuit for switching the driving method between that for a moving image and that for a still image, particularly in a display apparatus (hereinafter may be referred to as an LCD) such as a lower power consumption type.
2. Description of the Related Art
Generally, there are two types of driving methods for display apparatuses. One is a sequential-scanning driving method (called a “progressive driving method”) that sequentially scans all scanning lines in a frame. Another is a reduction driving method (called an “interlaced driving method”) that separates the frame into plural fields and reduces the scanning lines when carrying out the scanning of the scanning lines in the field.
In a field of TFT-LCDs, lower power consumption is increasingly demanded. To satisfy such an increasing demand, use of the reduction driving method from among the two methods is effective. However, the display apparatus must display moving images and still images, and when the reduction method is used for such images, especially for the moving image, defective elements such as lags and tailings are caused. For this reason, the progressive (non-reduction) driving method must be used. Therefore, the two driving methods must be switched between that for the moving image and that for the still image. This requires use of a function that quickly determines whether an image to be displayed is a moving image or a still image.
FIG. 9
shows a drawing illustrative of a conventional moving-image/still-image determination method. As shown in the figure, a frame memory
1
and a comparator circuit
2
are arranged in a display apparatus to perform the moving-image/still-image determination. When the moving-image/still-image determination is performed, image signals for an immediately-preceding screen are stored in the frame memory
1
in digital signal form, and the digital signals corresponding to the image signals for the immediately-preceding screen, which are supplied from the frame memory
1
, are compared to digital signals corresponding to current signals in the comparator circuit
2
. In this case, all digital signals of pixels on the same position of the screen are compared. As a result, when any difference is found between the signals for the immediately-preceding screen and the current signals, the screens are determined by the comparator circuit
2
to be moving screens, whereas when all the signals for the immediately-preceding and the current signals match, the screens are determined by the comparator circuit
2
to be still images.
Conventional display apparatuses having the moving-image/still-image determination function, however, uses a frame memory having a large capacity sufficiently to store signals corresponding to all pixels of one screen. For example, for a VGA (640×480 pixels), a frame memory of about 1 megabyte is necessary. When the moving-image/still-image determination is performed in a configuration such as that described above and a frame memory of a large capacity is used, a larger configuration is necessary and higher cost is required for manufacture. Therefore, use of such a large frame memory increases manufacturing cost of the display apparatus and limits the possibility of size reduction.
Furthermore, such a 1-megabyte frame memory alone consumes 1.5 W of power, while power that can be saved by use of the reduction driving method for still images in a VGA display apparatus is about 0.5 W. Therefore, this power saving by use of the large frame invites converse effects.
SUMMARY OF THE INVENTION
To solve the foregoing problems, an object of the present invention is to provide a display apparatus and a driving method for the display apparatus that allows size reduction without increasing manufacturing cost and provides greatest possible power saving effects by drive-method switching.
To these ends, according to one aspect of the present invention, there is provided a display apparatus that comprises a plurality of scanning lines and signal lines which are arranged in a matrix form; a scanning-line driving circuit to drive the scanning lines; a signal-line driving circuit to drive the signal lines; a moving-image/still-image determination circuit that has an adding means to add digital signals of pixels constituting image signals for a screen by receiving the digital signals on a pixel basis, has a comparing means to compare a result of addition of image signals for a one screen, which has been provided by the adding means, to a result of addition of digital signals constituting image signals for another screen which is adjacent in time to the earlier-stated one screen, uses a result of comparison by the comparing means to determine individual images provided by the image signals and by the image signals for the earlier-stated one screen and later-stated another-screen to be moving images when the two addition results are different from each other and to determine the images to be still images when the two addition results are identical to each other, and outputs a determination signal corresponding to the moving image or the still image; and controls the scanning-line driving circuit and the signal-line driving circuit according to the determination signal.
In performing the moving-image/still-image determination by using digital signals of screens which are adjacent in time to each other, for example, image signals for the immediately-preceding screen and the current screen, conventionally, digital signals equivalent to the image signals have been directly compared; therefore, a frame memory of a larger capacity has been required to store the image signals corresponding to all the pixels for one screen.
In the present invention, however, the adding means receives, on a pixel basis, digital signals of individual pixels which constitute image signals for one screen, and the comparing means compares a result of addition of the image signals for the immediately-preceding screen to a result of addition of the current image signals.
Hereinbelow, a description will be given of a principle of the determination method to be performed by the moving-image/still-image determination circuit of the present invention.
As shown in
FIGS. 8A and 8B
, an example arrangement is considered. In this arrangement, each of the non-hatched pixels is allowed to assume a “0” digital data (1 bit) and each of hatched pixels is allowed to assume a “1” digital data (1 bit) on a display screen formed of 12 pixels 3 (4 horizontal pixels×3 vertical pixels). Suppose a rectangular pattern
4
of the hatched pixels (1s ) in a background of the non-hatched pixels (0s), as shown in
FIG. 8A
, moves down, as shown in FIG.
8
B. In this case, the image signal data is represented by a bit string of “000000110011”, as arrayed from the upper left toward the lower right, in which the addition result is “4”. On the other hand, the image signal data after the movement is represented by a bit string of “000000000011”, in which the addition result is “2”. Comparison of these addition results provides a difference, and therefore determines the images which are to be deemed moving images.
In this case, when an arrangement is made so that the image signal data is transferred on a one-pixel basis in time series, real-time operation can be performed and a frame memory that preserves signal data of all the pixels is not necessary. With a conventional method that preserves the data in the frame memory, a memory capacity of 12 bits (1 bit×12 pixels) is necessary in the above example case. In the present invention, only the addition results and bits represented by binary digits preserved; therefore, only a 4-bit memory capacity is sufficient. Even when an addition result of a field of one-immediately-preceding screen is preserved, an 8-bit capacity is sufficient, in which case the
Brinks Hofer Gilson & Lione
Frontec Incorporated
Havan Thu-Thao
Luu Matthew
LandOfFree
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