Image processing apparatus and image display apparatus using same
An image processing apparatus of the present invention comprising (a) a first signal processing circuit for applying gamma correction to an n-bit (n: a natural number) digital signal inputted as a video signal and for converting the n-bit digital signal into an m-bit (m>n, m: a natural number) digital signal, and (b) a second signal processing circuit for adding a noise signal, which is used for pseudo contour reduction, into the m-bit digital signal from the first signal processing circuit and for outputting a Q-bit (Q: a natural number) digital signal, which is obtained from rounding off a less significant (m−Q) bit (Q≦n) from the m-bit digital signal, to a display section.
1. An image processing apparatus comprising:
a first signal processing circuit for converting an n-bit (n: a natural number) digital signal inputted as a video signal, into an m-bit (m>n, m: a natural number) digital signal, the n-bit digital signal expressing a tone gradation of 2 n , and the m-bit digital signal expressing a tone gradation of 2 m ; and
a second signal processing circuit having an address counter that is incremented by a horizontal synchronizing signal and a vertical synchronizing signal, the second signal processing circuit for (i) adding a noise signal to the m-bit digital signal converted by the first signal processing circuit, (ii) rounding down a less significant (m−Q) bit (Q<n, Q: a natural number) from the m-bit digital signal having added thereto the noise signal, and (iii) outputting the resulting Q-bit digital signal,
the first signal processing circuit including at least one look-up table for converting the inputted n-bit digital signal to the m-bit digital signal,
the first signal processing circuit converting the n-bit digital signal expressing the tone gradation of 2 n to the m-bit digital signal expressing the tone gradation of 2 m , by changing between, per display region, a plurality of look-up tables in which various values are entered in advance,
wherein the noise signal is added to the video signal based on a value of the address counter.
2. The image processing apparatus as set forth in claim 1 , wherein:
an average value of a signal level of the noise signal is set to zero.
3. The image processing apparatus as set forth in claim 1 , wherein:
the noise signal is a random noise signal with no regularity in its cycle of amplitude.
4. The image processing apparatus as set forth in claim 1 , wherein:
the noise signal is stored in a noise memory, the noise memory storing the noise signal for one screen.
5. The image processing apparatus as set forth in claim 1 , wherein:
the noise signal is stored in a noise memory, the noise memory storing the noise signal per block units smaller than one screen.
6. The image processing apparatus as set forth in claim 5 , wherein:
the noise signal is a signal generated by using an arbitrary noise pattern table and altering a starting point of the noise pattern for each of the block units.
7. The image processing apparatus as set forth in claim 1 , wherein:
a histogram of an amplitude of the noise signal shows Gaussian distribution where zero amplitude of the noise signal is at the center.
8. An image processing apparatus comprising:
a first signal processing circuit for converting an n-bit (n: a natural number) digital signal inputted as a video signal, into an m-bit (m>n, m: a natural number) digital signal, the n-bit digital signal expressing a tone gradation of 2 n , and the m-bit digital signal expressing a tone gradation of 2 m ; and
a second signal processing circuit having an address counter that is incremented by a horizontal synchronizing signal and a vertical synchronizing signal, the second signal processing circuit for (i) adding a noise signal to the m-bit digital signal converted by the first signal processing circuit, (ii) rounding down a less significant (m−Q) bit (Q<=n, Q: a natural number) from the m-bit digital signal having added thereto the noise signal, and (iii) outputting the resulting Q-bit digital signal,
the first signal processing circuit including at least one look-up table for converting the inputted n-bit digital signal to the m-bit digital signal,
the first signal processing circuit converting the n-bit digital signal expressing the tone gradation of 2 n to the m-bit digital signal expressing the tone gradation of 2 m , by rewriting, per display region, values in the look up table,
wherein the noise signal is added to the video signal based on a value of the address counter.