| 摘要 |
An apparatus and method for stretching the black level of an image signal to minimize flicker are provided. A black level stretching apparatus includes a minimum and maximum value extraction unit, and an adaptive black level stretch unit. The minimum and maximum value extraction unit for extracting the minimum and maximum values of each field of an image signal removes impulse noise using at least one low-pass-filter. The adaptive black level stretch unit extracts a tilt point, which delimits a dark region that is stretched, calculates a first gradient, selects the first gradient or a second gradient defined by users according to the dynamic range of the input signal, and stretches the black level of the image signal using the selected gradient. Another black level stretching apparatus includes a minimum value extraction unit, a dark region average value extractor, and a black level stretch unit. The minimum value extraction unit extracts and outputs the minimum value of each field of an image signal. The dark region average value extractor for extracting the average value of the image signal levels of each field, which belong to a dark portion of the field, removes impulse noise using at least one low-pass filter. The black level stretch unit calculates a pre-gradient and a gradient, which is obtained by multiplying the pre-gradient by a predetermined gradient gain, and stretches the black level of the image signal using the gradient. The black level stretching apparatus and method are effective in minimizing flicker caused by caption data. |
