Liquid crystal display device and method for emphasizing temporal signal change on a video signal based on at least a polarity for the video signal
A drive circuit of a liquid crystal display device performs line inversion drive based on a correction video signal V. A look-up table ( 12 ) includes two types of tables having stored therein correction values for use in overshoot drive. Based on a current-frame video signal X, a previous-frame video signal Y stored in a frame memory ( 11 ), and a polarity-reversing signal REV, a correction process portion ( 13 ) reads a correction value from the look-up table ( 12 ), and outputs the correction value being read as the correction video signal V. In such a manner, a correcting circuit ( 10 ) is used to control the degree of overshoot in accordance with the polarity-reversing signal REV. Thus, it is possible to suitably control the change in pixel brightness regardless of the polarity of the applied voltage, thereby preventing any fringes from being generated while displaying moving images.
1. A liquid crystal display device that performs line inversion drive, comprising:
a pixel array including a plurality of pixels disposed in row and column directions, a plurality of scanning signal lines each commonly connected to the pixels disposed in the same row, and a plurality of data signal lines each commonly connected to the pixels disposed in the same column;
a correcting circuit for obtaining a correction video signal by storing a video signal supplied from a signal source and performing correction for emphasizing temporal signal change between frames on the supplied video signal;
a scanning signal line drive circuit for sequentially selecting and activating the scanning signal lines; and
a data signal line drive circuit for applying a voltage corresponding to the correction video signal to the data signal lines, while changing its polarity every number of line periods, wherein
the correcting circuit performs a first correction for emphasizing the temporal signal change when the polarity of the voltage applied to the data signal line is positive and performs a second correction for emphasizing the temporal signal change when the polarity of the voltage applied to the data signal line is negative, and the first and second correction includes modifying a value of a current frame of the supplied video signal such that the temporal signal change is emphasized,
when the value of the current frame is greater than a value of a previous frame, then an amount that the value of the current frame is modified using the first correction is greater than to an amount that the value of the current frame is modified using the second correction, and
when the value of the current frame is less than the value of the previous frame, then the amount that the value of the current frame is modified using the first correction is less than to an amount that the value of the current frame is modified using the second correction.
2. The liquid crystal display device according to claim 1 , wherein the correcting circuit includes:
a storage portion for storing a video signal of at least one frame;
a conversion table having stored therein correction values emphasizing the temporal signal change in association with combinations of values for the video signal, as well as voltage polarities; and
a correction process portion for reading a correction value from the conversion table and outputting the correction value being read as the correction video signal based on a current-frame video signal supplied from the signal source, a previous-frame video signal stored in the storage portion, and the polarity of the voltage applied to the data signal lines.
3. The liquid crystal display device according to claim 1 , wherein the correcting circuit includes:
a storage portion for storing a video signal of at least one frame;
a conversion table having stored therein correction values emphasizing the temporal signal change in association with combinations of value ranges for the video signal, as well as voltage polarities; and
a correction process portion for reading a correction value from the conversion table and outputting a result obtained by subjecting the correction value being read to a operation as the correction video signal, based on a current-frame video signal supplied from the signal source, a previous-frame video signal stored in the storage portion, and the polarity of the voltage applied to the data signal lines.
4. The liquid crystal display device according to claim 1 ,
wherein the correcting circuit includes:
a storage portion for storing a video signal of at least one frame; and
a correction process portion for performing a correcting operation to emphasize the temporal signal change based on a current-frame video signal supplied from the signal source and a previous-frame video signal stored in the storage portion, and
wherein the correction process portion differentially performs the correcting operation in accordance with the polarity of the voltage applied to the data signal lines.
5. The liquid crystal display device according to claim 1 , further comprising a display control circuit for outputting a control signal to the scanning signal line drive circuit and the data signal line drive circuit,
wherein the correcting circuit differentially performs the correction in accordance with a polarity-reversing signal outputted from the display control circuit to the data signal line drive circuit.
6. The liquid crystal display device according to claim 1 , wherein the correcting circuit differentially performs the correction in accordance with a polarity-reversing signal supplied from the signal source, along with the video signal.
7. A method for driving a liquid crystal display device provided with a pixel array including a plurality of pixels disposed in row and column directions, a plurality of scanning signal lines each commonly connected to the pixels disposed in the same row, and a plurality of data signal lines each commonly connected to the pixels disposed in the same column, the method comprising the steps of:
obtaining a correction video signal by storing a video signal supplied from a signal source and performing correction for emphasizing temporal signal change between frames on the supplied video signal;
sequentially selecting and activating the scanning signal lines; and
applying a voltage corresponding to the correction video signal to the data signal lines, while changing its polarity every number of line periods, wherein
in the step of obtaining the correction video signal, a first correction for emphasizing the temporal signal change is performed when the polarity of the voltage applied to the data signal line is positive and a second correction for emphasizing the temporal signal change is performed when the polarity of the voltage applied to the data signal line is negative, and the first and second correction includes modifying a value of a current frame of the supplied video signal such that the temporal signal change is emphasized,
when the value of the current frame is greater than a value of a previous frame, then an amount that the value of the current frame is modified using the first correction is greater than an amount that the value of the current frame is modified using the second correction, and
when the value of the current frame is less than the value of the previous frame, then the amount that the value of the current frame is modified using the first correction is less than the amount that the value of the current frame is modified using the second correction.