Matsushita Electric Industrial Co., Ltd.

Yuki Kakuya

Atsuhisa Kageyama

Hidetoshi Suzuki

Katsuya Ishikawa

Keiichi Ito

Nobutaka Okada

Hisao Kunitani

The present invention has an object to provide a gradation correcting apparatus for correcting the gradation of the white side of a video luminance signal. The gradation correcting apparatus is provided with a maximum value detectorfor detecting a maximum value of a luminance signal S, a white comparatorfor comparing the luminance signal S, a maximum luminance value Sdetected by the maximum value detector, and a first white threshold value S, a white linear converterfor performing linear conversion on the luminance signal Son the basis of the maximum luminance value S, the first white threshold value S, and a second white threshold value S, and a white controllerfor correcting the luminance signal Son the basis of the result of the comparison in the white comparator, the output of the white linear converter, and the second white threshold value S

Gradation correcting apparatus gradation correcting method and video display apparatus

A luminance signal processing apparatus that detects an average luminance level, adaptively to various video signal formats. This luminance signal processing apparatus includes a window pulse generation unitfor generating a window pulse signal Sthat indicates a period during which a luminance signal of an input video signal is sampled; a luminance value addition unitfor obtaining a total sum of luminance values of the luminance signal in the period indicated by the window pulse signal S; a number-of-pixel addition unitfor obtaining the number of pixels in the period indicated by the window pulse signal S; a bit shift unitfor bit-shifting an output signal of the luminance value addition unitand an output signal of the number-of-pixel addition unit, respectively; and a division unitfor dividing the bit-shifted output signal of the luminance value addition unitby the bit-shifted output signal of the number-of-pixel addition unit, thereby obtaining an average luminance level.

Apparatus for processing luminance signal

An appropriate correction quantity is obtained for a video luminance signal on an individual video basis with a characteristic value, like the maximum or average value, of the luminance signal taken into account, thereby performing gray scale correction more effectively. A dynamic gamma correction apparatus for performing a correction on a video luminance signal includes: a correction start point control section for obtaining a correction start point, which is a lower limit of a given correction range, in accordance with a characteristic value of the luminance signal; a gamma correction quantity calculating section for obtaining a provisional correction quantity for the luminance signal to be corrected using the correction start point and the luminance signal; a gamma correction gain control section for obtaining a gain for the provisional correction quantity in accordance with the characteristic value of the luminance signal; a multiplier for obtaining a product of the provisional correction quantity and the gain as a gamma correction quantity; and an adder for obtaining a sum of the luminance signal and the gamma correction quantity and outputting the sum. The correction start point and the gain for the provisional correction quantity are controllable in accordance with the characteristic value of the luminance signal. Thus, an appropriate gamma correction quantity can be obtained as a final correction quantity.

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Osaka, Japan

Yuki Kakuya